Είμαστε εξειδικευμένοι στο σχεδιασμό και την κατασκευή συνθετικών, γρήγορων μηχανοκίνητων και ιστιοφόρων σκαφών, επιβατικών ή αναψυχής.
Το έμπειρο προσωπικό μας μπορεί να αντεπεξέλθει σε οποιαδήποτε υλική ζημιά και βλάβη που αφορά fiberglass, αποξικές και παραδοσιακές κατασκευές.
Μπορούμε να αναλάβουμε οπουδήποτε επίπεδο εργασίας που είναι απαραίτητο, ακόμα και το "γδύσιμο" και επανεπένδυση ενός σκάφους από το μηδέν.
Μπορούμε είτε να σας προσφέρουμε υπηρεσίες επισκευής / συντήρησης απευθείας στο σκάφος σας, ή στο ναυπηγείο, εφόσον είναι απαραίτητο. Η ομάδα μας έχει την κατάλληλη εμπειρία και γνώση για να αντιμετωπίσουν μία πληθώρα προβλημάτων σε παράκτια αλλά και πιο ανοιχτή περιοχή. Είναι δηλαδή εφικτό να επισκευάσουμε το σκάφος σας, χωρίς να χρειάζεται να το ρυμουλκήσουμε στο ναυπηγείο, ή και ούτε καν να δέσετε σε κάποιο από τα λιμάνια της Σαντορίνης.
Γρήγορες Παράκτιες Λύσεις
Επισκευές και μετατροπές
Ηλεκτρονικά υψηλής τεχνολογίας
Όλα σε ένα "Εντός" ή "Εκτός" Ναυπηγείου
Σχετικά με την Εταιρεία
Το Ναυπηγείο Σαντορίνης, ήταν μια ιδέα που ήρθε εν ζωή με το να φέρουμε μαζί τους πιο ικανούς και έμπειρους κατασκευαστές σκαφών στις Κυκλάδες.
Δημιουργήσαμε το μοναδικό ναυπηγείο του είδους του σε μια αρκετά μεγάλη ακτίνα, με την ικανότητα να κατασκευάζονται ορισμένων τύπων σκάφη.
Είμαστε εξειδικευμένοι σε σκάφη αναψυχής υψηλών επιδόσεων και γρήγορα GRP επιβατηγά πλοία.
Οι τεχνίτες μας έχουν περισσότερα από 30 χρόνια εμπειρίας στην κατασκευή fiberglass, καθώς και σε σύνθετες κατασκευές και επισκευές με χρήση τεχνικής κενού ή έγχυσης υλικών.
Οι ειδικές κατασκευές yacht και ιστιοπλοϊκών σκαφών, είναι ένα άλλο πεδίο κατασκευών για το οποίο είμαστε περήφανοι. Δίνουμε τεράστια προσοχή στη λεπτομέρεια, συμπεριλαμβανομένου του εσωτερικού, τις ξυλοκατασκευές και επενδύσεις, για τα οποία, μπορούμε να πούμε πως είναι μοναδικά.
Η Σαντορίνη είναι το νοτιότερο νησί των Κυκλάδων.
Οι Κυκλάδες είναι μια περιοχή με υψηλά ποσοστά κίνησης πλοίων και -σε πολλές περιπτώσεις- υπάρχει ανάγκη για την άμεση βοήθεια όσον αφορά υπηρεσίες επισκευής, συντήρησης κλπ.
Το ναυπηγείο μας έχει τη δυνατότητα να παρέχει αυτό το αρκετά αναγκαίο χέρι βοηθείας σε εξαιρετικό χρόνο απόκρισης με υψηλή ποιότητα των παρεχόμενων υπηρεσιών και των συνολικών αποτελεσμάτων.
Η ομάδα μας είναι διαθέσιμη όλο το εικοσιτετράωρο (24/7) και μπορούν να εγγυηθούν την αποτελεσματικότητα τους, ανεξάρτητα από την κλίμακα του προβλήματος που αντιμετωπίζετε.
Επιπρόσθετα, αν θα πρέπει να ρυμουλκήσουμε το σκάφος σας, για επισκευές, το προσωπικό μας θα δώσει προτεραιότητα στο έργο σας και να είστε βέβαιοι πως θα είστε βρεθείτε ξανά στη θάλασσα σε ελάχιστο χρόνο.
Είμαστε εξιδεικευμένοι στο σχεδιασμό και την -κατά παραγγελία- κατασκευή γρήγορων επιβατηγών πλοίων και τα ιστιοφόρων σκαφών.
Τα επιβατηγά πλοία μας είναι στην πλειοψηφία κατασκευασμένα από GRP fiberglass με βάση τον πολυεστέρα.
Έχουμε εισαγάγει μια εντελώς νέα διαδικασία στη κατασκευή σκαφών, ειδικά στις εξατομικευμένες κατασκευές, στο σχεδιασμό, ανάπτυξη και συναρμολόγηση από το πρώτο μέχρι το τελικό στάδιο.
Όλες τα βήματα της κατασκευής, εκτελούνται ένα προς ένα, βάση των απαιτήσεων και προδιαγραφών των πελατών, σε συνδυασμό με τα υψηλά μας πρότυπα ναυπηγικής και μηχανικής.
Η κατασκευή των επιβατηγών πλοίων βασίζεται κυρίως σε fiberglass και πολυεστέρα, ενώ η εφαρμογή και εγκατάσταση τους γίνεται με το χέρι, αφού πρώτα τα υλικά εμποτίζονται με ειδικά ρολλά για να ενισχυθεί η αντοχή τους.
Είμαστε επίσης πολύ έμπειροι σε προηγμένα σύνθετα κατασκευαστικά υλικά και εφαρμογές με εποξική ρητίνη με τη χρήση τεχνικής κενού.
Το έμπειρο προσωπικό του ναυπηγείου μπορεί να χειριστεί οποιοδήποτε είδος επισκευής σε fiberglass, εποξικά υλικά ή και παραδοσιακά υλικά.
Έχουμε διαθέσιμες ειδικές ομάδες που αναλαμβάνουν συγκεκριμένες επισκευές
Υπηρεσίες επισκευής επί ξηράς είναι διαθέσιμες στο νησί της Θήρας (Σαντορίνη) και το γενικό νότιο τμημα της ευρήτερης Κυκλαδικής περιοχής.
Επισκευές έκτακτης ανάγκης είναι διαθέσιμες απευθείας στο σκάφος σας .
Υπηρεσίες συντήρησης είναι διαθέσιμες όλο το Χειμώνα. Μπορούμε να αναλάβουμε οποιοδήποτε επίπεδο της διαδικασίας που απαιτείται, ακόμα και απογύμνωση και την ανακατασκευή του σκάφους από σχεδόν μηδενικό σημείο.
Επιπλέον παρέχουμε τις αναγκαίες συμβουλευτικές υπηρεσίες, για όλη τη δουλειά που θα μπορούσε ή θα έπρεπε να γίνει στο πλοίο, πάντα με βάση τις απαιτήσεις σας.
Εσωτερικά (ταπετσαρίες κλπ)
Ανακατασκευή Ξύλινων Στοιχείων
Βάψιμο – Βερνίκωμα
εχνική Κατασκευής Σκαφών Θαλάσσης
Έχουμε υιοθετήσει καινοτόμες τεχνικές σε όλες τις πτυχές της κατασκευής με fiberglass και ειδικά σε σύνθετες εφαρμογές με εποξική τεχνολογία κενού ή έγχυση ρητίνης.
Εφαρμογή Τεχνικής Κενού
Όλες οι ενισχύσεις είναι προ-εμποτισμένες από ένα κυλιόμενο μηχανισμό που εκτυλίζει το υλικό πριν από την ξήρανση του έτσι ώστε στη συνέχεια να εφαρμοστή η τεχνική κενού.
Χρησιμοποιούμε κυρίως μονής κατεύθυνσης ανθρακονήματα και biaxials ως πρόσθετα για την ενίσχυση του υλικού.
Η διαδικασία έχει ως στόχο:
Τη χρήση μικρότερου ποσοστού ρητίνης στις πλαστικοποιημένες επιφάνειες και τη μείωση των κενών που παράγουν καλύτερες μηχανικές και πλευστικές ιδιότητες, μειώνοντας το συνολικό βάρος του υλικού.
Μεγαλύτερη διάρκεια ζωής
Καλύτερη συμπεριφορά στο νερό
Υψηλότερο επίπεδο αντίστασης
Ελαττώνει την ανάγκη για συχνή συντήρηση
Ελαττώνει το κόστος συντήρησης
Περισσότερη ασφάλεια σε ακραίες συνθήκες
Ελαττώνει το χρόνο παράδοσης
Ελαττώνει ιδιαίτερα, το χρόνο επισκευών και συντήρησης
Το Τμήμα Εμπορικής Ναυτιλίας επιθυμεί να ενημερώσει το ενδιαφερόμενο κοινό που προτίθεται να κατασκευάσει σκάφος αναψυχής για ιδία χρήση ότι:
Ο ιδιοκτήτης του σκάφους θα πρέπει να ενημερώσει το Τμήμα Εμπορικής Ναυτιλίας για το χώρο κατασκευής του σκάφους ούτως ώστε να διενεργούνται έλεγχοι κατά τη διάρκεια της κατασκευής του.
Ο ιδιοκτήτης του σκάφους αναψυχής θα πρέπει να προσκομίσει στα γραφεία του Τμήματος Εμπορικής Ναυτιλίας Πιστοποιητικό Κατασκευαστή Μικρού Σκάφους (πιστοποιημένο από Πιστοποιόντα Υπάλληλο) (MS48).
Μαζί με το πιστοποιητικό κατασκευής μικρού σκάφους (MS48) θα πρέπει να κατατίθενται και τα κατασκευαστικά σχέδια (εάν υπάρχουν) καθώς επίσης και άλλα αποδεικτικά στοιχεία που να αποδεικνύουν ότι το σκάφος κατασκευάστηκε από τον συγκεκριμένο ιδιοκτήτη για ιδίαν χρήση (π.χ. φωτογραφικό υλικό, αποδείξεις για την αγορά των υλικών που αγοράστηκαν και χρησιμοποιήθηκαν για την κατασκευή του σκάφους κλπ.)
Υπενθυμίζεται ότι, με βάση τους Περί Βασικών Απαιτήσεων (Σκάφη Αναψυχής) Κανονισμούς του 2003, που δημοσιεύτηκαν στη Επίσημη Εφημερίδα με Αριθμό 3706 στις 18-04-2003 Ε.Ε. Παρ. ΙΙΙ (Ι) [Κ. Δ. Π. 307/2003] και τους περί Βασικών Απαιτήσεων (Σκάφη Αναψυχής) (Τροποποιητικούς) Κανονισμούς του 2004, δημοσιεύτηκαν στη Επίσημη Εφημερίδα με Αριθμό 3853 στις 30-04-2004 Ε.Ε. Παρ. ΙΙΙ (Ι) [Κ. Δ. Π. 537/2004], σκάφη που κατασκευάζονται για ιδία χρήση δεν θα διατίθενται στην αγορά για περίοδο πέντε (5) ετών.
Πληροφορίες για τις Ευρωπαϊκές Οδηγίες που αφορούν τα σκάφη αναψυχής και τις μηχανές θαλάσσης για τα σκάφη αναψυχής βρίσκονται στις ακόλουθες σελίδες:
Σκάφη αναψυχής - Επίσημη σελίδα Ευρωπαϊκής Επιτροπής
The Recreation Craft Sectoral Group
Οδηγίες νέας προσέγγισης - Υπουργείο Εμπορίου, Βιομηχανίας και Τουρισμού
Ως Ιστιοφόρο χαρακτηρίζεται οποιοδήποτε σκάφος ή πλωτό ναυπήγημα που αποκλειστικό μέσο πρόωσής του έχει την αιολική ενέργεια (τον άνεμο) επί των ιστίων του (πανιά) τα οποία και φέρει, εξ ου και η ονομασία του. Αποτελεί τη 2η εξελικτική βασική κατηγορία τύπων πλοίων, μετά το "κωπήλατο" και πριν από το "μηχανοκίνητο" (ατμόπλοιο).
Σήμερα σύμφωνα με τον υφιστάμενο Διεθνή Κανονισμό Αποφυγής Συγκρούσεως στη θάλασσα (ΔΚΑΣ) ιστιοφόρο - μηχανοκίνητο σκάφος που κινείται με τη φερόμενη βοηθητική μηχανή του, (σε άπνοια, ή σε αντιμονές, ή σε εκτέλεση αναστροφών, για τις οποίες η επιτυχία χωρίς τη μηχανή του θα ήταν αμφίβολη), παύει να θεωρείται ιστιοφόρο, αλλά μηχανοκίνητο, χωρίς δηλαδή το προνόμιο της προτεραιότητας.
Γενικά τα ιστιοφόρα λόγω των περιορισμένων δυνατοτήτων ευελιξίας τους, στην αλλαγή πορειών, διατηρούν προτεραιότητα σε τυχόν διασταύρωση της πορείας τους με άλλα μηχανοκίνητα πλοία, και ειδικότερα εντός διαύλων , εισόδων - εξόδων λιμένων κ.λπ., όπου ο χώρος εντείνει ακόμη περισσότερο αυτή την αδυναμία.
Σημειώνεται ότι παλαιότερα τα μηχανοκίνητα ιστιοφόρα λεγόμενα και αμφικίνητα, του άλλοτε ναυτικού, καθώς και τα πρώτα ατμοκίνητα ιστιοφόρα δεν θεωρούνταν ιστιοφόρα έστω κι αν η μηχανή τους αποτελούσε βοηθητικό μέσον της πρόωσής τους.
Τα ιστιοφόρα σε αντίθεση με τα μηχανοκίνητα (ατμόπλοια) χρειάστηκαν πολλούς αιώνες για την εξέλιξή τους προκειμένου να φθάσουν στο απόγειο της τελειοποίησής τους, όταν τότε αποκαλύφθηκε η δύναμη του ατμού που άρχισε να επικρατεί ως μέσον πρόωσης των πλοίων με συνέπεια δεκαετηρίδα με δεκαετηρίδα τα μεν ιστιοφόρα να παραγκωνίζονται, τα δε ατμόπλοια να εξελίσσονται.
Από την απώτατη αρχαιότητα μέχρι τα μέσα του μεσαίωνα η εξέλιξη του ιστιοφόρου πλοίου ήταν βραδύτατη, αν και το κουπί συνέχιζε να παραμένει ισχυρό μέσον πρόωσης. Τότε το ιστίο (πανί) που φέρονταν κυρίως από σταυρωτή κεραία (οριζόντια δοκό) από τον ιστό (κατάρτι), αποτελούσε το βοηθητικό μέσον πρόωσης, αφενός για τη μερική ανάπαυση των πληρωμάτων, αλλά ειδικότερα για την λεγόμενη «ουριοδρομία» (με τον άνεμο από πρύμνη).
Όπως μας πληροφορεί ακόμη και ο ανυπέρβλητος Όμηρος η ώρα απόπλου ήταν αμέσως μετά τη θερινή δύση του Ηλίου όπου αφού κόπαζε η θαλάσσια αύρα, η «πελαγία αύρα» των αρχαίων άρχιζε να πνέει η «απόγεια αύρα», δηλαδή όταν «αρχίζουν να βγάζουν οι στεριές» κατά την κοινή γλώσσα των Ελλήνων σύγχρονων ναυτικών.
Έτσι απέπλεαν οι τριήρεις ουριοδρομώντας, με κολπωμένο (φουσκωμένο) το εγκάρσιο πανί (ιστίο) τους. Σύμφωνα με τον σπουδαίο ναύαρχο και αρχαιολόγο Σέρρε το λυκαυγές της δόξας του ιστιοφόρου ήταν το "τετράγωνο ιστίο" και η εξέλιξή του σε τρίγωνο και τραπεζοειδές που άρχισε και η χρήση τους.
Παρά ταύτα πολλοί ναυτικοί ιστορικοί επιμένουν ότι η τριήρης δεν ήταν ιστιοφόρο αφού κύριο μέσον είχε τα κουπιά, επηρεασμένοι από τη σύγχρονη αντίληψη του όρου. Λειτουργικά θεωρούν ότι το ιστιοφόρο δεν αναδείχθηκε ούτε στη ρωμαϊκή περίοδο, αλλά ούτε και στη βυζαντινή αλλά περί τον 14ο με 15ο αιώνα όπου τότε μπορούσαν να πλέουν και με αντίθετο άνεμο δηλαδή να πλέουν την «εγγυτάτη». Τότε άρχισαν να εμφανίζονται τα λεγόμενα πανιά λατίνια, με τα οποία οι γαλέρες και οι νεφ του Λουδοβίκου του Αγίου πέτυχαν τη μέγιστη εξέλιξη. Παράλληλα εμφανίσθηκαν τα αργοκίνητα ιστιοφόρα σκάφη όπως το γαλιόνι, οι καράκες και λίγο αργότερα οι καραβέλες. Μικρά μεν, πλην όμως ευέλικτα, τα οποία και χρησιμοποίησαν οι πρώτοι εξερευνητές όπως ο Χριστόφορος Κολόμβος, ο Βάσκο ντα Γκάμα, κ.ά.
Αναμφίβολα σταθμός στην εξέλιξη των ιστιοφόρων αποτέλεσε η επιπλέον σπουδαία για τη ναυπηγική, ναυτική τέχνη και ναυτική τακτική, ναυμαχία της Ναυπάκτου όπου το ιστιοφόρο καθιερώθηκε και ως πολεμικό πλοίο γραμμής.
Όλων αυτών ακολούθησαν παράλληλες εφευρέσεις και ανακαλύψεις, όπως π.χ. το πηδάλιο, η άγκυρα, η πυξίδα, η αλυσιδωτή θωράκιση, κ.λπ., που επιτάχυναν την παραπέρα εξέλιξη του ιστιοφόρου πλοίου. Μέχρι που έφθασε η στιγμή της εξέλιξης, όταν ο λευκός ατμός αποτέλεσε τα μαύρα σύννεφα των ιστιοφόρων πλοίων.
Την εποχή των ιστιοφόρων πλοίων υπήρχαν μόνο τρεις βασικές κατηγορίες: α) τα πολεμικά ιστιοφόρα, β) τα εμπορικά ιστιοφόρα και γ) τα ανένταχτα, τα κοινώς λεγόμενα «πειρατικά». Τα δε εμπορικά μετέφεραν εμπορεύματα, επιβάτες και ζώα, δεν υπήρχε ακόμη ιδιαίτερη κατηγορία αντίστοιχη με το φορτίο όπως σήμερα. Ο δε πλοίαρχος αυτών εκτελούσε και χρέη ναυτικού πράκτορα, τροφοδότη, και όλες εκείνες τις επιμέρους βοηθητικές ειδικότητες που απαντώνται σήμερα στο ναυτιλιακό κόσμο.
Επίσης η σπουδαιότερη διάκριση που γίνονταν τότε στα ιστιοφόρα ήταν ανάλογα με τον αριθμό των ορθίων ιστών τους (κοινώς κατάρτια, ή άρμπουρα) που έφεραν, μη λαμβάνοντας υπόψη τον πρόβολο. Έτσι αυτά διακρίνονταν σε:
μονόστηλα, (κοινώς μονάρμπουρα) όσα έφεραν ένα κατάρτι
διίστια, ή δίστηλα (κοινώς δικάταρτα) όσα έφεραν δύο κατάρτια
τριίστια, ή τρίστηλα (κοινώς τρικάταρτα) όσα έφεραν τρια κατάρτια, και πολυΐστια, ή πολυκάταρτα,(κοινώς πολυάρμπουρα) όσα έφεραν από τέσσερα μέχρι και επτά όρθιους ιστούς, τα οποία συνήθως εκτελούσαν υπερπόντια ναυσιπλοΐα.
Εκτός αυτής της διάκρισης τα μονόστηλα και τα δίστηλα έπαιρναν και άλλες ονομασίες ανάλογα του είδους και του αριθμού των ιστίων τους (των πανιών τους), αλλά και εκ της γενικότερης εξαρτίας τους.
Το ελληνικό ναυτικό κατά την Ελληνική Επανάσταση του 1821 και μέχρι της εμφάνισης της «Καρτερίας» ήταν εξ ολοκλήρου ιστιοφόρο ναυτικό που περιελάμβανε σχεδόν όλους τους τύπους ιστιοφόρων της εποχής εκείνης όπως νάβες και ναβέτες, μπρίκια και γολετομπρίκια, γολέτες και σαχτούρες, μίστικα και μπελούτες, γαβάρες και πολλάκρες κ.ά. Ομοίως και τα πρώτα ελληνικά εμπορικά πλοία επιβατηγά και φορτηγά ήταν ιστιοφόρα, καθώς και τα αλιευτικά.
Η πλέον περίεργη εξέλιξη των ιστιοφόρων αποτελούν τα λεγόμενα, πειραματικά ακόμα, πλοία Μάγκνους ή Ρότορ ή Φλέττνερ
Αβιζό, Αδρομολόγητο πλοίο, Αερόστρωμνο, Αεροναυαγοσωστικό, Αεροπλανοφόρο, Ακταιωρός, Αμφίπλωρο, Αντιλίμπερτυ, Αντιτορπιλικό, Αποβατική υποστήριξη, Αποβατικό, Αρματαγωγό, Ατμόπλοιο, Ατμοβάρις, Ατμοδρόμων, Ατμοκορβέττα, Ατμομυοδρόμων, Ατμοτελωνίς, Ατμοφρεγάτα
Βαθυσκάφος, Βελλού, Βοηθητικό Βάσης, Βομβάρδα, Βρίκιον, Βρατσέρα, Βριγαντίνο, Βρικογολέτο, Βυθοκόρος
Γαλέα, Γαλεάσσα, Γαλιόνι, Πλοίο γραμμής
Δίκροτο, Δεξαμενόπλοιο, Διήρης, Διπύθμενα, Δρόμων, Δρομολογημένο πλοίο
Εύδρομον, Εκατόντορος, Εκπαιδευτικό, Εκρανοπλάνο, Ελικοπτεροφόρο, Εμπορικό πλοίο, Επίτακτο, Επιβατηγό πλοίο
Ημιβυθιζόμενο σκάφος, Ημιολία
Θαλάσσιο ταξί, Θαλαμηγός, Θωρακοβάρις, Θωρακοδρόμων, Θωρηκτό
Κάτεργο, Κότερο, Καλωδιακό πλοίο, Κανό, Κανονιοφόρος, Καραβέλα, Καταδιωκτικό πλοίο, Καταδρομικό, Καταμαράν, Κηρυκευτικό, Κοντέινερ (πλοίο), Κορβέττα
Λίμπερτυ, Λιβύρνις, Λιμνόπλοιο
Μίνι κάριερ, Μότορσιπ, Μύστικο, Μεσογειακό πλοίο, Μεταλλευματοφόρο πλοίο, Μηχανοκάικο, Μπαλκ κάριερ, Μυοδρόμων, Μυοπάρων
Νάβα, Ναβέτα, Ναρκαλιευτικό, Ναρκοθέτις, Ναυαγοσωστικό, Ναυκλαστροφόρο
Πάμφυλος (πλοίο), Παγοθραυστικό, Παράκτιο βοηθητικό, Πεντηκόντορος, Περιπολικό, Περιπολικό ανθυποβρυχιακό, Πετρελαιοφόρο, Πλοίο RoRo, Πλοίο άνευ εκτοπίσματος, Πλοίο Αλιείας Τορπιλών, Πλοίο Μάγκνους, Πλοίο Ο.Β.Ο., Πλοίο ψυγείο, Πλοηγίδα, Πλοιάριο, Πλωτό, ναυπήγημα, Πλωτό νοσοκομείο, Πλωτό συνεργείο, Πολεμικό πλοίο, Ποντοπόρο, Πορθμείο, Πορθμείο σιδηροδρόμων, Ποταμόπλοιο, Πυραυλάκατος, Πυρηνοκίνητο πλοίο, Πυροσβεστικό (πλοίο), Πυρπολικό
Σακολέβα, Σακτούρα, Σεμπέκο, Σπογγαλιευτικό, Συνοδό στόλου
Ταχύπλοο, Ταχυδρομικό πλοίο, Τζόγκα, Τορπιλάκατος, Τορπιλοβόλο, Τριήρης, Τροχήλατο πλοίο, Τσαμπέκο
Υγραεριοφόρο πλοίο, Υδρογραφικό, Υδροκόπτερο, Υδροπλάνο, Υδροπτέρυγο, Υδροφόρο, Υπερωκεάνειο
Φαλαινοθηρικό, Φαρόπλοιο, Φελούκα, Φούστα (πλοίο), Φορτηγό πλοίο, Φορτηγιδοφόρο, Φρεγάδιο, Φρεγάτα, Φυλακίδα
Από ιστορικής άποψης διακρίνονται τρία είδη πλοίων τα οποία γενικά ταυτίζονται με αντίστοιχες ιστορικές περιόδους. Στην πρώτη περίοδο, την εποχή των κωπήλατων σκαφών, στη δεύτερη περίοδο που κυριαρχούν τα ιστία (πανιά), δηλαδή των ιστιοφόρων σκαφών και τέλος στην τρίτη των (πάσης φύσεως) μηχανοκίνητων σκαφών.
Σ΄ αυτό που τουλάχιστον συμφωνούν όλοι οι αρχαιολόγοι, ιστορικοί ερευνητές αλλά και φιλόλογοι είναι ότι η "γέννηση" του πλοίου ανάγεται στην προϊστορική εποχή. Ακριβώς τότε που ο άνθρωπος όταν βρισκόμενος δίπλα σε επιπλέοντα κορμό δένδρου ανέβηκε σ΄ αυτό και κατάφερε ακουμπώντας είτε τα χέρια είτε τα πόδια στο νερό να τον κατευθύνει μετατρέποντάς τον σε σκάφος. Αυτή είναι η πρώτη ναυπηγική κατασκευή!
Η εξέλιξη της ναυπηγικής τέχνης την εποχή εκείνη ήταν πολύ αργή, όπως και με τις άλλες δραστηριότητες του ανθρώπου. Για πολλά χρόνια οι άνθρωποι χρησιμοποιούσαν κωπήλατα μονόξυλα, πλοιάρια δηλαδή τα οποία ήταν λαξευμένα από ένα και μόνο κορμό δένδρου, τα οποία είχαν τη δυνατότητα μεταφοράς εμπορευμάτων. Μάρτυρες της εμπορικής χρήσης των μονόξυλων είναι τα εργαλεία από οψιανό που έχουν βρεθεί σε αρκετούς προϊστορικούς οικισμούς. Το ηφαιστειογενές αυτό πέτρωμα υπάρχει μόνο στη Μήλο, στο Γυαλί της Νισύρου και στην Αντίπαρο. Υποστηρίζεται ότι τουλάχιστον από τη Μεσολιθική εποχή (8η χιλιετία π.Χ.) οι κάτοικοι του Αιγαίου είχαν τη δυνατότητα να διασχίζουν το Αρχιπέλαγος και να μεταφέρουν το απαραίτητο ορυκτό στον τόπο τους από τη Μήλο.
Για να λάβει το μονόξυλο τη μορφή της σχεδίας (σύνδεση κορμών) και από αυτή τη μορφή της "διήρους" και της "τριήρους" πέρασαν πολλές εκατονταετίες ίσως και χιλιετίες! Άξιο προσοχής όμως είναι η διατήρηση του επιμήκους σχήματος που είχε απ' αρχής το πλοίο. Οι παλαιότερες αναπαραστάσεις πλοίων προέρχονται από πήλινα τηγανόσχημα σκεύη της Πρωτοκυκλαδικής ΙΙ περιόδου (2800-2300 π.Χ.). Στα βασικά στοιχεία αυτών των μορφών διακρίνονται ένα είδος εμβόλου στην ελαφρώς ανασηκωμένη πλώρη, οι σειρές κουπιών εκατέρωθεν του σκάφους και η ογκώδης ανασηκωμένη πρύμνη.
Διά μέσου των αιώνων η εξέλιξη διαπιστώνεται στο μέγεθος (δυνατότητα μεταφοράς) και στη ταχύτητα (με αύξηση των αριθμών των κουπιών). Όμως, ο τρόπος ναυπήγησης σε συνδυασμό με τη χρήση ξύλου καθώς και η ελικτική ικανότητα, δεν επέτρεψαν την αύξηση του μήκους πέρα από ένα όριο, με συνέπεια την ανάπτυξη πολύκωπων πλοίων (900-700 π.Χ.). Ταυτόχρονα, παρατηρείται για πρώτη φορά ο διαχωρισμός εμπορικών και πολεμικών πλοίων. Τα πολεμικά πλοία, για λόγους ευελιξίας ήταν ελαφρά, στενά και χαμηλά σκάφη. Διέθεταν έμβολο στην πλώρη ως επιθετικό όπλο(*), υπερυψωμένο κατάστρωμα που προαναγγέλλει τη δεύτερη σειρά κουπιών καθώς και λίγο αργότερα, την παρεξειρεσία (προεξοχή των πλευρών για την τοποθέτηση των κουπιών). Οι ανάγκες της νέας πολεμικής τακτικής του εμβολισμού οδήγησαν στην καθιέρωση των πολύκωπων πλοίων, τα οποία είναι γρήγορα και ευέλικτα αφού το μήκος τους υποδιπλασιάζεται τουλάχιστον. Τα πιο κοινά πολεμικά πλοία την εποχή αυτή είναι η τριακόντορος και και η πεντηκόντορος, με με τριάντα και πενήντα κουπιά αντίστοιχα, διατεταγμένα σε μία ή δύο σειρές, οπότε και ονομάζονταν μονήρη και διήρη. Αντίθετα τα εμπορικά σκάφη που χρειάζονταν όγκο για μεταφορική ικανότητα, ήταν φαρδύτερα, ψηλότερα και βαθύτερα. Είχαν λιγότερους κωπηλάτες και μεγαλύτερη επιφάνεια ιστίων. Τα σκάφη αυτά ήταν γνωστά ως "στρογγυλά" ενώ τα πολεμικά ως "μακραί νήες".
Από τον 8ο έως τον 6ο αι. π.Χ. οι "μακραί νήες" εξελίσσονται ακόμα περισσότερο με αποκορύφωμα τη δημιουργία των τριήρεων, που κατά πάσα πιθανότητα ναυπηγούνται στην Κόρινθο. Το κορυφαίο αυτό πλοίο θα καθιερωθεί στη συνέχεα σε όλα τα ελληνικά ναυτικά κέντρα. Με συνολικό μήκος 38-40 μ. και αναλογία μήκους προς πλάτος ένα προς δέκα, οι τριήριε προωθούνταν από 170 κουπιά και αντίστοιχους κωπηλάτες, διατεταγμένους σε τρεις σειρές καθ'ύψος (τους θαλαμίτες, τους ζυγίτες και τους θρανίτες).
Στους Ελληνιστικούς χρόνους οι ισορροπίες δυνάμεων μετατοπίζουν την ναυτική ισχύ από την Ελλάδα στην Αίγυπτο των Πτολεμαίων αλλά και στη Ρόδο, την κορυφαία ναυτική δύναμη στο Αιγαίο την εποχή εκείνη. Η ναυπηγική δεν εξελίσσεται ιδιαίτερα, όμως ναυπηγούνται αξιόλογα πλοία όπως η ναυαρχίδα του Πτολεμαίου του Φιλοπάτορα (3ος π.Χ. αιώνας).
Οι αρχαίοι Έλληνες κατ΄ εξοχήν ναυτικός λαός συνέβαλε ιδιαίτερα στην εξέλιξη της ναυπηγικής. Επινόησε πλείστες κατασκευαστικές μεθόδους στη ναυπηγική τέχνη που διατηρούνται ακόμα μέχρι και σήμερα. Η αναφορά του Ομήρου στη κατασκευή πλοίου από τον Οδυσσέα δεν διαφέρει σε τίποτα από το σημερινό τρόπο κατασκευής των ξύλινων σκαφών! Αλλά και η προ του Τρωϊκού πολέμου, η Αργοναυτική εκστρατεία καταμαρτυρά σπουδαίες γνώσεις ναυπηγικής και πλεύσης και να καταστεί έτσι πολύ μεγάλη στην εποχή της ναυτική επιχείρηση.
Τα ιστία (πανιά) χρησιμοποιήθηκαν από τους αρχαιότατους χρόνους. Λέγεται ότι με αυτά οι Αιγύπτιοι βοηθούσαν τους εργάτες που έσερναν τεράστιες σχεδίες κατά μήκος του Νείλου. Αλλά και η εμπορική επέκταση στον Εύξεινο Πόντο, γνωστότερη κατά την παράδοση ως Αργοναυτική Εκστρατεία έγινε με τη βοήθεια των ιστίων, όπως και η μετάβαση (διαπόρθμευση) των Ελλήνων κατά την Εκστρατεία της Τροίας στηρίχτηκε στη δύναμη των "ούριων ανέμων". Καταφανής και η γνώση των αιολικών δυνάμεων.
Η επικράτηση όμως των ιστιοφόρων επί των κωπήλατων σκαφών ολοκληρώθηκε με την ανακάλυψη της Αμερικής, όταν οι νέοι θαλάσσιοι δρόμοι που προέκυψαν, εκτός της Μεσογείου, για τα κωπήλατα σκάφη ήταν πλέον μακρινοί, δύσκολοι έως αδύνατοι και άσκοποι.
Η ανακάλυψη της ιστιοπλοΐας (μανουβράρισμα πολλών πανιών) και της πυξίδας με την εξέλιξη της ναυπηγίας (σε θέματα ευστάθειας) ήταν οι κύριοι συντελεστές της επικράτησης των ιστιοφόρων σκαφών. Μέγα ορόσημο της επικράτησης αυτής υπήρξε η Ναυμαχία της Ναυπάκτου (7 Οκτωβρίου 1571) όταν ο στόλος των Ευρωπαϊκών δυνάμεων (από ιστιοφόρα) κατατρόπωσε τον Οθωμανικό στόλο (από κωπήλατα σκάφη) και αναδείχθηκε η υπεροχή!
Οι επαναστατικές εφευρέσεις εντός μικρού σχετικά χρονικού διαστήματος κατά τον 19ο αι. δημιούργησε το τύπο του μηχανοκίνητου πλοίου ώστε να φθάσουμε τελικά στη σύγχρονη εποχή της Ναυπηγικής.
Ενώ στις δύο προηγούμενες εποχές το υλικό κατασκευής των πλοίων ήταν το ξύλο, στην εποχή των μηχανοκίνητων, υλικό κατασκευής πλέον ήταν ο χάλυβας, υλικό που έμελλε να προσφέρει τεράστιες δυνατότητες στη περαιτέρω εξέλιξη.
Κύριες εφευρέσεις που μετέβαλαν ριζικά την όψη του πλοίου είναι: Η ατμομηχανή, η έλικα, η φθηνή παραγωγή του χάλυβα, το ραντάρ, το πυροβόλο γραμμωτής (εσωτερικά) κάνης, τα εκρηκτικά βλήματα πυροβόλου, η τορπίλη και οι πύραυλοι.
Αν και οι τέσσερις τελευταίες εφευρέσεις είναι καθαρά πολεμικά μέσα, εντούτοις πρωτοστάτησαν στην εξέλιξη της ναυπηγικής. Χαρακτηριστικό παράδειγμα ήταν όταν οι Γάλλοι κάλυπταν τα πλευρά του ξύλινου πολεμικού τους πλοίου Gloire (εκτοπ. 5000 τόν.) με χαλύβδινο θώρακα προκειμένου να το προστατεύσουν από τα επικίνδυνα βλήματα του εχθρού (που εκτοξεύονταν από μακρινή απόσταση χάρις στη γραμμωτή κάνη). Με τη τοποθέτηση όμως της ατμομηχανής οι πυρκαγιές των ιστίων από τους εξερχόμενους των καπνοδόχων σπινθήρες ήταν αναπόφευκτες. Έτσι όχι μόνο τα ιστία καταργήθηκαν σύντομα αλλά και τα καταστρώματα και οι υπερκατασκευές αντικαταστάθηκαν από χαλύβδινα.
Οι Ναυπηγικές γραμμές και οι κύριες διστάσεις του πλοίου όχι μόνο ολοκληρώνουν μια πλήρη γεωμετρική εικόνα του πλοίου. Στην ανάλυση των ναυπηγικών γραμμών και των διαστάσεων θα αναφερθούν μόνο οι αναγκαίοι επί μέρους όροι για τη πληρέστερη αντίληψη.
Βασικό χαρακτηριστικό του σχήματος του πλοίου είναι η συμμετρία.
(Μοναδική ίσως περίπτωση ασύμμετρης ναυπήγησης είναι οι "γόνδολες" λόγω ανάγκης έκκεντρης ώθησης της κώπης).
Ως ναυπηγικές γραμμές θεωρούνται οι:
Εγκάρσιες ναυπηγικές γραμμές ή γραμμές νομέων (frame lines)
Διαμήκεις ναυπηγικές γραμμές ή κάθετοι (Longitudinal lines, Vertical lines, Buttocks)
Οριζόντιες ναυπηγικές γραμμές ή παρίσαλοι ή ίσαλοι (Water lines) και οι Διαγώνιες βοηθητικές ναυπηγικές γραμμές (Diagonals)
Για όλες τις παραπάνω δείτε το άρθρο Ναυπηγικές γραμμές καθώς και για το τρόπο σχεδίασής των.
Για τις κύριες διαστάσεις Μήκος σκάφους (Length), Πλάτος σκάφους (Breadth ή Beam) και Κοίλο σκάφους Κύριες διαστάσεις πλοίου
Ναυπ. μονάδες μέτρησης
Στη Ναυπηγική λόγω της επί σειρά ετών επικράτησης των Βρετανών το αγγλικό σύστημα μετρήσεων έχει ευρύτατη χρήση.
Παρατίθενται οι συντελεστές μετατροπής των μονάδων μέτρησης από το αγγλικό σύστημα στο μετρικό των πλέον εύχρηστων στη ναυπηγική.
Μονάδα Μήκους (Length):
Δάκτυλος, κοινώς ίντσα (inch συμβολίζεται: in ή ΄΄ ) 1in = 25,4 mm.
Πους, κοινώς ποδάρι (foot συμβολίζεται: ft ή ' ) 1 ft = 304,8 mm (=12in).
Υάρδα, κοινώς γιάρδα (yard συμβολίζεται: yd ) 1 yd = 914,4 mm (= 36in = 3ft).
Μίλιον, κοινώς μίλι (Statue mile or mile)
1 mile = 1609958 mm (=1759,684 yd = 5281,998 ft = 63384,04 in).
Ναυτικό μίλι (nautical mile or mile)
1 mile = 1853190 mm (=2025,536 yd = 6080 ft = 72960,09 in)
Ευρέως χρησιμοποιούμενο υποπολλαπλάσιο του δακτύλου είναι το 1/8 αυτού, 1/8΄΄= 3,175 mm. Για τη ταχύτερη εύρεση των πολλαπλάσιων του 1/8΄΄ σε mm μετατρέπουμε αυτά σε όγδοα, έτσι το 1/4΄΄=2/8΄΄, 3/8΄΄, 1/2΄΄=4/8΄΄, 5/8΄΄, 3/4΄΄=6/8΄΄ και τέλος 7/8΄΄ αρκεί να πολλαπλασιάσουμε τα 3,175mm επί 2,3,4,5,6 και 7 αντίστοιχα.
Δείγμα γραφής μήκους στο σχέδιο κατά το αγγλοσαξονικό σύστημα: 54'-5 5/8΄΄. Αυτό σημαίνει 54 πόδες (54'Χ304,8=16459,2mm) συν 5 δάκτυλοι (5Χ25,4=127,0mm) συν 5/8 δακτύλου (5Χ3,175=15,9mm). Ήτοι 54'-5 5/8΄΄= 16602,01 mm ή 16,602μ.
Ιδιαίτερη προσοχή: παύλα μεταξύ ποδών και δακτύλων δεν είναι σημείο αφαίρεσης, επίσης ως η ελληνική υποδιαστολή, στο αγγλικό σχέδιο είναι η τελεία.
Σε πολλά σχέδια αναγράφονται ενδείξεις όπως 0,24΄΄ ή .24΄΄. Αμφότεροι οι τρόποι σημαίνουν το αυτό δηλ. 24 εκατοστά της ίντσας. Για σύντομη προσεγγιτική μετατροπή αυτών σε mm διαιρούμε το 24 διά του 4 (δηλ. διά του λόγου 100/25,4=3,94 κατά προσέγγιση 4).
Οι Αμερικανοί για το πάχος των ελασμάτων αναγράφουν το βάρος αυτών σε λίβρες (Pounds) ανά τετραγωνικό πόδι και το συμβολίζουν με την ένδειξη #.
Μονάδα Βάρους (Weight):
Μετρικός Τόνος (metric ton) συμβολίζεται mt ή mton ή ton. 1mt = 1000 Kg
Λίβρα (pound) συμβολίζεται lb. 1lb = 0,45359 kg
Μακρύς Αγγλικός τόνος ή Αγγλικός τόνος ( Long Ton ή Gross Ton ) συμβολίζεται gt ή gton ή ton.
1 gton = 1016,05 Kg (=2240 lbs).
Βραχύς τόνος (Sort Ton ή Net Ton) συμβολίζεται nt ή nton ή ton.
1 nton = 907,185 Kg (= 2000 lbs = 0,89286 ton).
Χάντρεντγουέιτ (Hundredweight), συμβολίζεται cwt. 1 cwt = 50,8024 Kg (= 112lbs = 0,05gton).
Σημ: Όταν αναφέρεται η λέξη τόνος χωρίς άλλη διευκρίνιση νοείται ο μετρικός τόνος, όταν διευκρινίζεται αγγλικός τόνος χωρίς επί μέρους διευκρίνιση νοείται ο μακρύς τόνος (2240lbs)
Διαγωγή πλοίου (trim), ονομάζεται οποιαδήποτε εικόνα παρουσιάζει ένα πλοίο όταν δεν είναι ζυγοσταθμισμένο, δηλαδή δεν είναι ισοβύθιστο κυρίως κατά το διάμηκες, (κατά το εγκάρσιο χαρακτηρίζεται κλίση πλοίου).
Ή Διαγωγή πλοίου συμβολίζεται συνήθως με το γράμμα d. Και υφίσταται κάθε φορά που παρατηρείται διαφορά μεταξύ του πρωραίου και του πρυμναίου βυθίσματος. (d = dΠΡ - dΠM). Όταν d = 0 δεν υπάρχει διαγωγή.
Δύο είναι οι μορφές διαγωγής ενός πλοίου:
1. Όταν το πρωραίο βύθισμα είναι μικρότερο του πρυμναίου, οπότε και καλείται έμπρυμνο (by the stern), και
2. Όταν το πρωραίο βύθισμα είναι μεγαλύτερο του πρυμναίου, οπότε το πλοίο χαρακτηρίζεται έμπρωρο (by the bow).
Σε τακτά χρονικά διαστήματα θα πρέπει να ελέγχονται τα βυθίσματα πλώρης μέσου και πρύμνης προκειμένου να διαπιστώνεται αν το πλοίο έχει υποστεί παραμορφώσεις από τις διάφορες καταπονήσεις του, στο κυματισμό όπως αυτές είναι η κύρτωση ή η κοίλωση του πλοίου.
Με τον όρο ζυγοστάθμιση πλοίου (trimming) χαρακτηρίζεται η διαγωγή ενός έμφορτου πλοίου όταν αυτό φέρεται ισοβύθιστο σε πλώρη, πρύμνη και κατά πλευρά. Τότε το πλοίο λέγεται "ζυγοσταθμισμένο" (trimmed ship). Στη περίπτωση αυτή η Διαγωγή πλοίου είναι μηδενική.
Η ζυγοστάθμιση φορτηγού πλοίου γίνεται κυρίως με την τακτοποίηση του μεταφερομένου φορτίου το καλούμενο ευτρεπισμό (σε ξηρά φορτία) ή χαπιάρισμα (σε χύμα φορτία). Σε όλους τους άλλους τύπους πλοίων γίνεται με την ισοβαρή κατανομή έρματος, φορτίων, επιβατών και εφοδίων πλοίου.
Όταν το φορτίο που παραμένει στο πλοίο είναι περιορισμένο ή πλέει "κενό φορτίου" τότε η ζυγοστάθμιση επιτυγχάνεται με τον ερματισμό των δεξαμενών ζυγοστάθμισης.
Έχοντας υπόψη τον ορισμό της ταλάντωσης δια της οποίας χαρακτηρίζεται η οποιαδήποτε παλινδρομική κίνηση ενός σώματος γύρω από τη θέση ισορροπίας του, κατ΄ επέκταση προσδιορίζεται ότι με τον όρο ταλάντωση πλοίου χαρακτηρίζονται στο σύνολό τους οι διάφορες παλινδρομικές κινήσεις που απαντώνται (παρατηρούνται) στο πλοίο συνήθως σε κυματισμό.
Στη ταλάντωση πλοίου περιλαμβάνονται τρεις παλινδρομικές κινήσεις, οι οποίες και είναι:
Σχεδιάγραμμα των ταλαντώσεων πλοίου σε κυματισμό.
ο Προνευστασμός, (pitching), κοινώς λεγόμενο σκαμπανεύασμα, η Διατοίχιση, (rolling), κοινώς λεγόμενο μπότζι ή μποτζάρισμα, και η Ανάπαλση ή ταλάντωση καθ΄ ύψος, (vertical), κοινώς λεγόμενο ανεβοκατέβασμα.
Οι δύο πρώτες παραπάνω μορφές ταλάντωσης αφορούν κλίση πλοίου, ενώ η τρίτη είναι ταλάντωση κατακόρυφη, χωρίς απαραίτητα να δημιουργεί γωνία κλίσης.
Στο σχεδιάγραμμα που παρατίθεται διαφαίνονται οι άξονες χ, y και z, των τριών ταλαντώσεων που παρουσιάζει το πλοίο (και όχι οι διευθύνσεις κλίσεων). Ο άξονας χ είναι ο άξονας του διατοιχισμού, ο άξονας y είναι ο άξονας του προνευστασμού και z ο άξονας της ανάπαλσης. Έτσι 1 είναι η διεύθυνση της ανάλπασης ως προς τη θέση ισσοροπίας, 2 ομοίως του προνευστασμού και 3 της διατοίχισης. Επ΄ αυτών 4 είναι η ταλάντωση της ανάλπασης κατά κάθετη διεύθυνση και στροφή δεξιά αριστερά του διαμήκους άξονα του πλοίου, 5 η ταλάντωση του προνευστασμού, εγκάρσια ταλάντωση του πλοίου κατά πλώρη - πρύμνη και 6 η ταλάντωση της διατοίχισης, διαμήκης ταλάντωση του πλοίου δεξιά - αριστερά.
Γενικά όμως στη πράξη, σε θαλασσοταραχή, παρατηρείται ταυτόχρονος συνδυασμός και των τριών παραπάνω μορφών ταλάντωσης, δίνοντας την εντύπωση ότι το πλοίο εκτελεί μια σύνθετη κίνηση μορφής του αριθμού "οκτώ", (εξ ου και λαογραφικά "οκτάρι" ονομάζεται στο ελληνικό πολεμικό ναυτικό, εκ μέρους των ναυτών, ο υψηλόβαθμος αξιωματικός, ως μέσον διευκόλυνσης).
Ως κέντρο ταλάντωσης πλοίου (center of oscillation) προσδιορίζεται το κέντρο πλευστότητας γύρω από το οποίο ταλαντεύεται το πλοίο από εξωτερικές δυνάμεις.
Ευστάθεια πλοίου (stability) ονομάζεται η τάση που παρουσιάζει ένα πλοίο ν΄ ανθίσταται σε οποιαδήποτε κλίση εγκάρσια ή διαμήκη, που προκαλείται από διάφορες αιτίες, καθώς επίσης και η τάση επαναφοράς του στην "αρχική θέση ισορροπίας" του (κατακόρυφη θέση).
Οι διάφοροι χειρισμοί του πλοίου, η κατανάλωση καυσίμων και ποσίμου ύδατος, η ποσότητα του μεταφερόμενου φορτίου, ο τρόπος στοιβασίας του (κυρίως), η πλήρωση, ή η εκκένωση θαλασσέρματος κ.λπ. είναι σημαντικοί παράγοντες που επηρεάζουν την ευστάθεια του πλοίου. Η γνώση της ευστάθειας του πλοίου θεωρείται ζωτικής σημασίας και ενδιαφέρει κυρίως στις εγκάρσιες κλίσεις (κατά δεξιά - αριστερή πλευρά), του λεγόμενου διατοιχισμού αφού απ΄ αυτήν εξαρτάται ο κίνδυνος ανατροπής του πλοίου.
Προκειμένου τα πλοία να διατηρούν την ευστάθειά τους ιδίως όταν είναι άφορτα γεμίζουν τις ειδικές δεξαμενές που φέρουν με έρμα. Στη ναυπηγική γίνεται ιδιαίτερος λόγος για αρχική (initial st.), δυναμική (dynamical st.), αρνητική (negative st.), στατική (statical st.), εγκάρσια ευστάθεια (transverse st.) κ.λπ. που εξαρτάται από το ύψος εξάλλων, επίσης για καμπύλη ευστάθειας (curve of st.), όριο ευστάθειας (range of st.) καθώς και για ροπή ευστάθειας (moment of st.).
Για όλες όμως τις παραπάνω αναφορές έξι είναι οι βασικές έννοιες: η βαρύτητα και το κέντρο βάρους, η άντωση και το κέντρο άντωσης, καθώς και το μετάκεντρο και το μετακεντρικό ύψος, όπου εξ αυτών ορίζονται σχετικές αποστάσεις και ροπές επί των διαστάσεων του κάθε πλοίου.
Η εξακρίβωση της ευστάθειας ενός πλοίου γίνεται με ειδικό πείραμα το λεγόμενο πείραμα ευσταθείας (experiment of stability).
Για τη πληρέστερη κατανόηση της ευστάθειας των πλοίων κρίνεται απαραίτητη η παράθεση στοιχειδών πειραματικών γνώσεων υδροστατικής και ειδικά επί της Αρχής του Αρχιμήδη σε ότι αφορά τα πλοία.
Αν σε κάποια μικρή δεξαμενή νερού ριφθεί ένα μεταλλικό συμπαγές αντικείμενο βάρους π.χ. 3 kg, αυτό αμέσως θα βυθισθεί, θα φθάσει στο πυθμένα εκτοπίζοντας όγκο ύδατος ίσο με τον όγκο του αντικειμένου. Αν όμως ριφθεί στο νερό ένα υδατοστεγές (στεγανό) δοχείο ίδιου βάρους με το προηγούμενο αντικείμενο τότε αυτό θα επιπλέει στη επιφάνεια του νερού εκτοπίζοντας τόσο όγκο νερού όσος θα είναι και ο όγκος του βυθισμένου (υπό τη στάθμη) τμήματος του δοχείου. Τότε διαπιστώνεται ότι: το βάρος του εκτοπιζομένου (όγκου) ύδατος είναι ίσο με το βάρος του δοχείου. Αν στη συνέχεια τοποθετηθεί ένα αντικείμενο μέσα στο δοχείο βάρους π.χ. 1 kg, τότε το δοχείο θα βυθισθεί ακόμα περισσότερο έτσι ώστε να εκτοπίσει επιπλέον όγκο ύδατος, ίσο με το επιπλέον όγκο του βυθισμένου τμήματός του, του οποίου το βάρος θα είναι 1 kg. Έτσι υπό τη νέα αυτή συνθήκη ο συνολικός όγκος ύδατος που θα έχει εκτοπιστεί θα είναι 4 κιλά.
Ένα πλοίο λοιπόν όταν είναι σε κατακόρυφη θέση ως προς τη στάθμη της θάλασσας εκτοπίζει ένα ορισμένο όγκο ύδατος. Αν αυτό κλίνει προς τη μια πλευρά τότε αλλάζει το σχήμα μόνο του βυθισμένου τμήματός του, των υφάλων του, ενώ ο όγκος του εκτοπιζομένου ύδατος και βεβαίως το βάρος αυτού παραμένει το ίδιο. Συνεπώς η ευστάθεια είναι εκείνη που θα διατηρήσει το πλοίο σε ασφαλή πλεύση.
Κύρια στοιχεία της ευστάθειας των πλοίων είναι το κέντρο βάρους πλοίου, το κέντρο άντωσης πλοίου, που και τα δύο επενεργούν ως ζεύγος ευστάθειας, η ροπή ευστάθειας (μοχλοβραχίονας ευστάθειας), το μετάκεντρο, το μετακεντρικό ύψος, ο βαθμός ευστάθειας και τέλος οι συνθήκες ευστάθειας στις διάφορες κλίσεις πλοίου.
Κύρια βοηθήματα που λαμβάνονται υπόψη στην ευστάθεια του πλοίου είναι το εκάστοτε μέσο βύθισμα του πλοίου, το μετακεντρικό διάγραμμα, η καμπύλη ευστάθειας και ερευνητικά το πείραμα ευσταθείας.
Ερματισμός (ballasting) ονομάζεται η χρησιμοποίηση θαλάσσιου νερού με το οποίο γίνεται η πλήρωση ειδικών δεξαμενών (θαλασσέρματος) των πλοίων για την επίτευξη επαρκούς ευστάθειας. Η εργασία αυτή ονομάζεται ερμάτωση και αποτελεί αντικείμενο της ναυτικής τέχνης, που εμπίπτει γενικότερα στην αρμοδιότητα του Υποπλοιάρχου (Υπάρχου) και των αξιωματικών καταστρώματος του πλοίου.
Μετά το πέρας της εκφόρτωσης ενός πλοίου και προκειμένου να συνεχίσει τον πλού του "άνευ φορτίου" (in ballast), θα πρέπει αυτό να ερματιστεί με πλήρωση των προς τούτο δεξαμενών ή και δεξαμενών φορτίου αν πρόκειται για δεξαμενόπλοιο, είτε με θαλασσινό νερό είτε με ποτάμιο, το οποίο και επιτυγχάνεται με τις αντλίες φορτίου. Ο ερματισμός γίνεται πάντα σύμφωνα με σχετικές οδηγίες των κατασκευαστών - ναυπηγών προκειμένου ν΄ αποφευχθούν μόνιμες παραμορφώσεις του πλοίου, (κοίλωση ή κύρτωση).
Η ανάγκη αυτή του ερματισμού είναι περισσότερο έκδηλη στα φορτηγά πλοία, (έναντι των επιβατηγών), όπου οι διαφορές βάρους και βυθίσματος μεταξύ έμφορτης και άφορτης κατάστασης είναι μεγάλες και επομένως μεγάλη και η απαιτούμενη ποσότητα έρματος. Η χρήση θαλασσέρματος επιτρέπει την ταχεία και εύκολη ρύθμιση του ερματισμού με ανάλογη πλήρωση ή κένωση των καταλλήλων δεξαμενών. Ως δεξαμενές θαλασσέρματος χρησιμοποιούνται συνήθως οι δεξαμενές ζυγοστάθμισης, τα διπύθμενα καθώς και οι δεξαμενές κύτους.
Με τη χρησιμοποίηση των δεξαμενών ζυγοστάθμισης μεταβάλλεται αισθητά και σχετικά γρήγορα η διαγωγή του πλοίου αφού προστίθεται ή αφαιρείται βάρος σε μεγάλη απόσταση από το κέντρο πλευστότητας. εντούτοις η προσθήκη "βαρών" στα ακραία σημεία του πλοίου (πλώρη - πρύμνη) αυξάνει τις κοπώσεις ιδίως σε θαλασσοταραχή και μειώνει την ικανότητα του σκάφους ν΄ ανταπεξέρχεται τα κύματα. Ακόμη η χρησιμοποίηση δεξαμενής μόνο στο ένα άκρο του πλοίου προκαλεί μετατόπιση του κέντρου βάρους προς την κατεύθυνση του κέντρου άντωσης με συνέπεια να μειώνεται το διάμηκες μετακεντρικό ύψος.
Η κατασκευή των διπυθμένων δίνει μια πολύ καλή λύση στο πρόβλημα του ερματισμού καθόσον το βάρος κατανέμεται μέσω αυτών στο μέσο του πλοίου και η άυξηση του βυθίσματος είναι ισομερής και στα δύο άκρα του πλοίου. Η υποδαίρεση των διπυθμένων σε επιμέρους στεγανά διαμερίσματα αποκλείει την ύπαρξη ελεύθερων επιφανειών του θαλάσσιου έρματος και διευκολύνει πολύ περισσότερο για όπου και όσο χρειάζεται. Επίσης η μεταβολή της θέσης του κέντρου βάρους είναι ουσιαστική αφού οι δεξαμενές διπυθμένων βρίσκονται στο κατώτερο μέρος του πλοίου.
Οι δεξαμενές κύτους που κατασκευάζονται συνήθως στο μέσον του πλοίου πρώραθεν και πρύμνηθεν του μηχανοστασίου (όταν αυτό βρίσκεται κάτω από το μεσόστεγο) έχουν μικρό μήκος και το σύνηθες ύψος τους είναι από τον εσωτερικό πυθμένα μέχρι του κατώτερου καταστρώματος (πανιόλου). Λόγω δε του ύψους αυτού επηρεάζουν αισθητά την καθ΄ ύψος θέση του κέντρου βάρους όποτε χρησιμοποιούνται αυτά. Η κατασκευή τους όμως επιτρέπει να δέχονται και φορτία χύμα όταν το πλοίο ταξιδεύει έμφορτο και ν΄ αντέχουν έτσι στις διάφορες αναπτυσσόμενες πιέσεις όταν είναι πλήρεις θαλασσέρματος. Όλοι οι παραπάνω χώροι είναι οι συνήθεις χώροι θαλασσέρματος πλην όμως πλοία ειδικής κατασκευής μπορεί να προβλέπουν και άλλους ιδιαίτερους χώρους π.χ. πλωτές δεξαμενές κ.λπ.
Γενικά ο τρόπος ερματισμού και το εκάστοτε βάρος του έρματος εξαρτάται από την κατάσταση του φόρτου, το τύπο του πλοίου, τις ιδιότητες του πλοίου, την εποχή, την κατάσταση θαλάσσης και τη διάρκεια του ταξιδίου. Ενδεικτικά αναφέρεται ότι για άφορτο πλοίο με δυσμενή εποχή και περιοχή ταξιδίου, η ποσότητα έρματος ίση με το 50% - 60% του εκτοπίσματος του πλοίου κρίνεται ικανοποιητική ή το μέσο βύθισμα του ερματισθέντος πλοίου θα πρέπει να είναι ίσο με το μέσο όρο του μέσου αφόρτου και μέσου εμφόρτου βυθίσματος του πλοίου ή λίγο περισσότερο.
Πολλές φορές συμβαίνει σε έκτακτες περιπτώσεις, η ανάγκη της εκκένωσης ή αντίθετα της πλήρωσης των δεξαμενών θαλασσέρματος κατά τη διάρκεια του πλου. Σε τέτοιες περιπτώσεις θα πρέπει πάντα να λαμβάνεται υπόψη ότι κατά το χρονικό αυτό διάστημα της πλήρωσης ή της απάντλησης θα υφίσταται εντός των δεξαμενών μια επικίνδυνη μετακινούμενη μάζα ύδατος. Σε τέτοιες συνθήκες, επιβάλλεται να τεθεί το πλοίο σε αντιμονή (κοινώς τραβέρσο), ίδίως αν πρόκειται για δεξαμενές του κύτους ή της ζυγοστάθμισης, δεδομένου ότι στα κυψελοειδή διπύθμενα η ελεύθερη επιφάνεια του έρματος περιορίζεται από τους νομείς και τις σταθμίδες, τόσο ώστε να φθάνει να μειώνεται η επίδρασή της μέχρι και στο 1/4, στην ευστάθεια του πλοίου.
Ειδικότερα για τα δεξαμενόπλοια που μεταφέρουν επικίνδυνα φορτία ο ερματισμός ή αφερματισμός που γίνεται για ιδιαίτερους σκοπούς, όπως πλήρωσης δεξαμενών φορτίου για απομάκρυνση επικίνδυνων αερίων, αυτοί διακόπτονται αμέσως στις ακόλουθες περιπτώσεις:
Όταν επέλθει θύελλα με κεραυνούς.
Όταν από της καπνοδόχου του πλοίου ή άλλου πλοίου που βρίσκεται εγγύτατα αναδίδονται σπινθήρες που ο άνεμος κατευθύνει στο Δεξαμενόπλοιο.
Όταν προσεγγίσει άλλο πλοίο, π.χ. ρυμουλκό ή άλλο σκάφος και υφίσταται παρόμοιος παραπάνω κίνδυνος.
Σ΄ όλες αυτές τις περιπτώσεις παράλληλα με τη διακοπή κλείνονται όλα τα ανοίγματα των δεξαμενών φορτίου. Επισημαίνεται ακόμη ότι ο αξιωματικός του πλοίου που εκτελεί φυλακή κατά τη διάρκεια ερματισμού ή αφερματισμού, όπως και φόρτωσης ή εκφόρτωσης του πλοίου θα πρέπει να βρίσκεται στο κατάστρωμα έτοιμος ν΄ αντιμετωπίσει κάθε έκτακτη περίσταση και να λάβει τα ανάλογα μέτρα ασφάλειας. Παράλληλα παρακολουθεί τους κάβους πρόσδεσης του πλοίου ώστε αυτοί στη διάρκεια των παραπάνω εργασιών να μην είναι ιδιαίτερα τεταμένοι, αλλά ούτε και χαλαροί. Τέλος οι εργασίες αυτές θα πρέπει να γνωρίζονται προηγουμένως στις Αρχές του λιμένος και να ακολουθούνται τα τυχόν επιπρόσθετα μέτρα ασφαλείας που μπορεί να έχουν θεσπιστεί.
Η αντοχή της κατασκευής του πλοίου συνίσταται στη διερεύνηση της συμπεριφοράς του πλοίου ως δοκού στην επιφάνεια της θάλασσας καθώς και στη συμπεριφορά των επιμέρους κατασκευαστικών στοιχείων υπό τις συνθήκες φόρτισης που προδιαγράφονται από τις λειτουργικές και επιχειρησιακές ανάγκες.
Πλαστικότητα πλοίου (plasticity) ή και "πλαστικός σχεδιασμός πλοίου" (plastic desing) είναι όρος της ναυπηγικής.
Με τη σύγχρονη θεωρία της πλαστικότητας των υλικών, αντιμετωπίζονται από τους Νηογνώμονες τα προβλήματα αντοχής τμημάτων του μεταλλικού σκελετού του πλοίου.
Η βάση της θεωρίας αυτής είναι η πλαστική ροπή της επιφάνειας, που στη πράξη σημαίνει το μέτρο της δυνατότητας χρησιμοποίησης της διατομής.
Η Λέμβος (κοινώς βάρκα) είναι ένα μικρό πλωτό μέσο μεταφοράς. Οι βάρκες είναι γενικά μικρότερες από τα σκάφη και τα πλοιάρια. Η κατασκευή μιας βάρκας είναι συνήθως από ξύλο, μέταλλο ή το πλαστικό GFK. Σημειώνεται ότι συνεκδοχικά λέμβος λέγεται και ο κάλαθος -χώρος- των αεροναυτών στα αερόστατα.
Οι λέμβοι χρησιμοποιούνται για συγκοινωνία κοντινών αποστάσεων, σε περιορισμένες μεταφορές, φορτοεκφορτώσεις πλοίων, σε απο-επιβιβάσεις στα λιμάνια και πλοία, για ψάρεμα (ψαροπούλες ή τράτες), για άθλημα ή θαλάσσιους περιπάτους, όπου και ανάλογα της χρήσης τους λαμβάνουν διάφορες ονομασίες. Στην αρχαιότητα η ονομασία της ήταν αρσενικού γένους ο λέμβος.
Συνεπώς η λέμβος είναι ένα θαλάσσιο μέσον, πλωτό ναυπήγημα, "άφρακτο", χωρίς δηλαδή κατάστρωμα, (κατά το μεγαλύτερο μέρος), σχεδιασμένο να επιπλέει στο νερό, και να βοηθά στις μετακινήσεις κυρίως σε θαλάσσιες ή λιμναίες προστατευμένες περιοχές.
Γενικά ως λέμβος χαρακτηρίζεται το μικρό σκάφος (βάρκα) μήκους μέχρι 8-10 μέτρα, που κύριο μέσον πρόωσής του έχει τα κουπιά ή τα ιστία, σε αντιδιαστολή με την άκατο που μέσον πρόωσης έχει την έλικα. Συνεπώς άκατος καθιερώθηκε να λέγεται η μηχανοκίνητη λέμβος που διακρίνεται επιμέρους, ανάλογα με τη φέρουσα μηχανή. Το σύνολο των λέμβων που φέρει ένα πλοίο ή κάποιος φορέας π.χ. ναύσταθμος, ή υπηρεσία λιμένος ή αθλητικός όμιλος λέγονται γενικά εφόλκια. Η ένθεση των εφολκίων των πλοίων, γίνεται επ΄ αυτών με ειδικά μέσα που ονομάζονται επωτίδες.
Οι λέμβοι προωθήθηκαν σαν ένα ιδανικό όχημα για μικρές μεταφορές τα πρώτα χρόνια. Γίνονταν όμως πιο ευρύχωρες και κατάληλες για ήρεμα ποτάμια και θάλασσες. Άρχισαν να χρησιμοποιούνται το 4000-3000 π.Χ. στον Ινδικό ωκεανό, παίζοντας σημαντικό ρόλο στο εμπόριο μεταξύ των πολιτισμών Ινδίας και Μεσοποταμίας. Υπολείμματα και παραστάσεις αρχαίων τύπων λέμβων έχουν ανακαλυφτεί σε πολλές περιοχές της Ινδικής κοιλάδας.
Shipyards and dockyards are places where ships are repaired and built. These can be yachts, military vessels
, cruise liners or other cargo or passenger ships
are sometimes more associated with maintenance and basing activities than shipyards, which are sometimes associated more with initial construction. The terms are routinely used interchangeably, in part because the evolution of dockyards and shipyards has often caused them to change or merge roles.
Countries with large shipbuilding industries include South Korea, Australia, Japan, China, Germany, Turkey, Poland and Croatia. The shipbuilding industry tends to be more fragmented in Europe than in Asia. In European countries there are a greater number of small companies, compared to the fewer, larger companies in the shipbuilding countries of Asia.
Most shipbuilders in the United States are privately owned, the largest being Huntington Ingalls Industries, a multi-billion dollar defense contractor. The publicly owned shipyards in the US are Naval facilities providing basing, support and repair.
are constructed nearby the sea or tidal rivers to allow easy access for their ships. In the United Kingdom, for example, shipyards were established on the River Thames (King Henry VIII founded yards at Woolwich and Deptford in 1512 and 1513 respectively), River Mersey, River Tees, River Tyne, River Wear and River Clyde – the latter growing to be the World's pre-eminent shipbuilding centre.
Sir Alfred Yarrow established his yard by the Thames in London's Docklands in the late 19th century before moving it northwards to the banks of the Clyde at Scotstoun (1906–08). Other famous UK shipyards include the Harland and Wolff yard in Belfast, Northern Ireland, where the Titanic was built, and the naval dockyard at Chatham, England on the Medway in north Kent.
The site of a large shipyard will contain many specialised cranes, dry docks, slipways, dust-free warehouses, painting facilities
and extremely large areas for fabrication of the ships.
After a ship's useful life is over, it makes its final voyage to a shipbreaking yard, often on a beach in South Asia. Historically shipbreaking was carried on in drydock in developed countries, but high wages and environmental regulations have resulted in movement of the industry to developing regions.
The world's earliest known dockyards were built in the Harappan port city of Lothal circa 2400 BC in Gujarat, India. Lothal's dockyards connected to an ancient course of the Sabarmati river on the trade route between Harappan cities in Sindh and the peninsula of Saurashtra when the surrounding Kutch desert was a part of the Arabian Sea.
Lothal engineers accorded high priority to the creation of a dockyard and a warehouse to serve the purposes of naval trade. The dock was built on the eastern flank of the town, and is regarded by archaeologists as an engineering feat of the highest order. It was located away from the main current of the river to avoid silting, but provided access to ships in high tide as well.
The name of the ancient Greek city of Naupactus means "shipyard" (combination of the Greek words ναύς naus ship, boat and πήγνυμι pêgnumi, pegnymi builder, fixer). Naupactus' reputation in this field extends to the time of legend, where it is depicted as the place where the Heraclidae built a fleet to invade the Peloponnesus.
In the Spanish city of Barcelona, the Drassanes shipyards were active from at least the mid-13th century until the 18th century, although it at times served as a barracks for troops as well as an arsenal. During its time of operation it was continuously changed, rebuilt and modified, but two original towers and part of the original eight construction naves remain today. It is currently a maritime museum.
Ships were the first items to be manufactured in a factory, several hundred years before the Industrial Revolution, in the Venice Arsenal, Venice, Italy. The Arsenal apparently mass-produced nearly one ship every day using pre-manufactured parts, and assembly lines and, at its height, employed 16,000 people.
Shipbuilding is the construction of ships and floating vessels. It normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces its roots to before recorded history.
Shipbuilding and ship repairs
, both commercial and military, are referred to as "naval engineering". The construction of boats is a similar activity called boat building.
The dismantling of ships is called ship breaking.
Archaeological evidence indicates that humans arrived on Borneo at least 120,000 years ago, probably by sea from the Asian mainland during an ice age period when the sea was lower and distances between islands shorter (See History of Borneo and Papua New Guinea). The ancestors of Australian Aborigines and New Guineans also went across the Lombok Strait to Sahul by boat over 50,000 years ago.
Evidence from Ancient Egypt shows that the early Egyptians knew how to assemble planks of wood into a ship hull as early as 3000 BC. The Archaeological Institute of America reports that some of the oldest ships yet unearthed are known as the Abydos boats. These are a group of 14 discovered ships in Abydos that were constructed of wooden planks which were "sewn" together. Discovered by Egyptologist David O'Connor of New York University, woven straps were found to have been used to lash the planks together, and reeds or grass stuffed between the planks helped to seal the seams. Because the ships are all buried together and near a mortuary belonging to Pharaoh Khasekhemwy, originally they were all thought to have belonged to him, but one of the 14 ships dates to 3000 BC, and the associated pottery jars buried with the vessels also suggest earlier dating. The ship dating to 3000 BC was about 25 m, 75 feet long and is now thought to perhaps have belonged to an earlier pharaoh. According to professor O'Connor, the 5,000-year-old ship may have even belonged to Pharaoh Aha.
Early Egyptians also knew how to assemble planks of wood with treenails to fasten them together, using pitch for caulking the seams. The "Khufu ship", a 43.6-meter vessel sealed into a pit in the Giza pyramid complex at the foot of the Great Pyramid of Giza in the Fourth Dynasty around 2500 BC, is a full-size surviving example which may have fulfilled the symbolic function of a solar barque. Early Egyptians also knew how to fasten the planks of this ship together with mortise and tenon joints.
The oldest known tidal dock in the world was built around 2500 BC during the Harappan civilisation at Lothal near the present day Mangrol harbour on the Gujarat coast in India. Other ports were probably at Balakot and Dwarka. However, it is probable that many small-scale ports, and not massive ports, were used for the Harappan maritime trade. Ships from the harbour at these ancient port cities established trade with Mesopotamia. Shipbuilding and boatmaking may have been prosperous industries in ancient India. Native labourers may have manufactured the flotilla of boats used by Alexander the Great to navigate across the Hydaspes and even the Indus, under Nearchos. The Indians also exported teak for shipbuilding to ancient Persia. Other references to Indian timber used for shipbuilding is noted in the works of Ibn Jubayr.
The ships of Ancient Egypt's Eighteenth Dynasty were typically about 25 meters (80 ft) in length, and had a single mast, sometimes consisting of two poles lashed together at the top making an "A" shape. They mounted a single square sail on a yard, with an additional spar along the bottom of the sail. These ships could also be oar propelled. The ocean and sea going ships of Ancient Egypt were constructed with cedar wood, most likely hailing from Lebanon.
The naval history of China stems back to the Spring and Autumn Period (722 BC–481 BC) of the ancient Chinese Zhou Dynasty. The Chinese built large rectangular barges known as "castle ships", which were essentially floating fortresses complete with multiple decks with guarded ramparts.
The ancient Chinese also built ramming vessels as in the Greco-Roman tradition of the trireme, although oar-steered ships in China lost favor very early on since it was in the 1st century China that the stern-mounted rudder was first developed. This was dually met with the introduction of the Han Dynasty junk ship design in the same century.
Archeological investigations done at Portus near Rome have revealed inscriptions indicating the existence of a 'guild of shipbuilders' during the time of Hadrian.
Viking longships were an advancement from the traditional clinker-built hulls of plank boards tied together with leather thongs. Sometime around the 12th century, northern European ships began to be built with a straight sternpost, enabling the mounting of a rudder, which was much more durable than a steering oar held over the side. Development in the Middle Ages favored "round ships", with a broad beam and heavily curved at both ends. Another important ship type was the galley which was constructed with both sails and oars.
An insight into ship building in the North Sea/Baltic areas of the early medieval period was found at Sutton Hoo, England, where a ship was buried with a chieftain. the ship was 26 metres (85 ft) long and, 4.3 metres (14 ft) wide. Upward from the keel, the hull was made by overlapping nine planks on either side with rivets fastening the oaken planks together. It could hold upwards of thirty men.
The first extant treatise on shipbuilding was written ca. 1436 by Michael of Rhodes, a man who began his career as an oarsman on a Venetian galley in 1401 and worked his way up into officer positions. He wrote and illustrated a book that contains a treatise on ship buildin
g, a treatise on mathematics, much material on astrology, and other materials. His treatise on shipbuilding treats three kinds of galleys and two kinds of round ships.
Outside Medieval Europe, great advances were being made in shipbuilding. The shipbuilding industry in Imperial China reached its height during the Song Dynasty, Yuan Dynasty, and early Ming Dynasty, building commercial vessels that by the end of this period were to reach a size and sophistication far exceeding that of contemporary Europe. The mainstay of China's merchant and naval fleets was the junk, which had existed for centuries, but it was at this time that the large ships based on this design were built. During the Sung period (960–1279 AD), the establishment of China's first official standing navy in 1132 AD and the enormous increase in maritime trade abroad (from Heian Japan to Fatimid Egypt) allowed the shipbuilding industry in provinces like Fujian to thrive as never before. The largest seaports in the world were in China and included Guangzhou, Quanzhou, and Xiamen.
In the Islamic world, shipbuilding thrived at Basra and Alexandria, the dhow, felucca, baghlah and the sambuk, became symbols of successful maritime trade around the Indian Ocean; from the ports of East Africa to Southeast Asia and the ports of Sindh and Hind (India) during the Abbasid period.
At this time islands spread over vast distances across the Pacific Ocean were being colonised by the Melenesians and Polynesians, who built giant canoes and progressed to great catamarans.
With the development of the carrack, the west moved into a new era of ship construction by building the first regular ocean going vessels. In a relatively short time, these ships grew to an unprecedented size, complexity and cost.
Shipyards became large industrial complexes and the ships built were financed by consortia of investors. These considerations led to the documentation of design and construction practices in what had previously been a secretive trade run by master shipwrights, and ultimately led to the field of naval architecture, where professional designers and draughtsmen played an increasingly important role. Even so, construction techniques changed only very gradually. The ships of the Napoleonic Wars were still built more or less to the same basic plan as those of the Spanish Armada of two centuries earlier but there had been numerous subtle improvements in ship design and construction throughout this period. For instance, the introduction of tumblehome; adjustments to the shapes of sails and hulls; the introduction of the wheel; the introduction of hardened copper fastenings below the waterline; the introduction of copper sheathing as a deterrent to shipworm and fouling; etc
The industrial revolution made possible the use of new materials and designs that radically altered shipbuilding. Other than its widespread use in fastenings, Iron was gradually adopted in ship construction, initially in discrete areas in a wooden hull needing greater strength, (e.g. as deck knees, hanging knees, knee riders and the like). Then, in the form of plates rivetted together and made watertight, it was used to form the hull itself. Initially copying wooden construction traditions with a frame over which the hull was fastened, Isambard Kingdom Brunel's Great Britain of 1843 was the first radical new design, being built entirely of wrought iron. Despite her success, and the great savings in cost and space provided by the iron hull, compared to a copper sheathed counterpart, there remained problems with fouling due to the adherence of weeds and barnacles. As a result composite construction remained the dominant approach where fast ships were required, with wooden timbers laid over an iron frame (the Cutty Sark is a famous example). Later Great Britain's iron hull was sheathed in wood to enable it to carry a copper-based sheathing. Brunel's Great Eastern represented the next great development in shipbuilding. Built in association with John Scott Russell, it used longitudinal stringers for strength, inner and outer hulls, and bulkheads to form multiple watertight compartments. Steel also supplanted wrought iron when it became readily available in the latter half of the 19th century, providing great savings when compared with iron in cost and weight. Wood continued to be favored for the decks.
After the Second World War, shipbuilding (which encompasses the shipyards, the marine equipment manufacturers, and many related service and knowledge providers) grew as an important and strategic industry in a number of countries around the world. This importance stems from:
The large number of skilled workers required directly by the shipyard, along with supporting industries such as steel mills, railroads and engine manufacturers
A nation's need to manufacture and repair its own navy and vessels that support its primary industries
Historically, the industry has suffered from the absence of global rules and a tendency towards (state-supported) over-investment due to the fact that shipyards offer a wide range of technologies, employ a significant number of workers, and generate income as the shipbuilding market is global.
Shipbuilding is therefore an attractive industry for developing nations. Japan used shipbuilding in the 1950s and 1960s to rebuild its industrial structure; South Korea started to make shipbuilding a strategic industry in the 1970s, and China is now in the process of repeating these models with large state-supported investments in this industry. Conversely, Croatia is privatising its shipbuilding industry.
As a result, the world shipbuilding
market suffers from over-capacities, depressed prices (although the industry experienced a price increase in the period 2003–2005 due to strong demand for new ships which was in excess of actual cost increases), low profit margins, trade distortions and widespread subsidisation. All efforts to address the problems in the OECD have so far failed, with the 1994 international shipbuilding agreement never entering into force and the 2003–2005 round of negotiations being paused in September 2005 after no agreement was possible. After numerous efforts to restart the negotiations these were formally terminated in December 2010. The OECD's Council Working Party on Shipbuilding (WP6) will continue its efforts to identify and progressively reduce factors that distort the shipbuilding market.
Where state subsidies have been removed and domestic industrial policies do not provide support in high labor cost countries, shipbuilding has gone into decline. The British shipbuilding industry is a prime example of this with its industries suffering badly from the 1960s. In the early 1970s British yards still had the capacity to build all types and sizes of merchant ships but today they have been reduced to a small number specialising in defence contracts and repair work. Decline has also occurred in other European countries, although to some extent this has reduced by protective measures and industrial support policies. In the U.S.A, the Jones Act (which places restrictions on the ships that can be used for moving domestic cargoes) has meant that merchant shipbuilding has continued, albeit at a reduced rate, but such protection has failed to penalise shipbuilding inefficiencies. The consequence of this is that contract prices are far higher than those of any other country building oceangoing ships.
China is an emerging shipbuilder that overtook South Korea during the 2008-2010 global financial crisis as they won new orders for medium and small-sized container ships. China is now firmly the world's largest shipbuilder with 45% of the world's total orders, and its quality and technology have improved very much.
Today, South Korea is the world's second largest shipbuilding country with a global market share of 29% in 2012. South Korea leads in the production of large vessels such as cruise liners, super tankers, LNG carriers, drill ships, and large container ships. In the 3rd quarter of 2011, South Korea won all 18 orders for LNG carriers, 3 out of 5 drill ships and 5 out of 7 large container ships. South Korea's shipyards are highly efficient, with the world's largest shipyard in Ulsan operated by Hyundai Heavy Industries slipping a newly built, $80 million vessel into the water every four working days. South Korea's "big three" shipbuilders, Hyundai Heavy Industries, Samsung Heavy Industries, and Daewoo Shipbuilding & Marine Engineering, dominate global shipbuilding, with STX Shipbuilding, Hyundai Samho Heavy Industries, Hanjin Heavy Industries, and Sungdong Shipbuilding & Marine Engineering also ranking among the top ten shipbuilders in the world. In 2007, STX Shipbuilding further strengthened South Korea's leading position in the industry by acquiring Aker Yards, the largest shipbuilding group in Europe. (The former Aker Yards was renamed STX Europe in 2008). In the first half of 2011, South Korean shipbuilders won new orders to build 25 LNG carriers, out of the total 29 orders placed worldwide during the period.
Japan had been the dominant ship building country from the 1960s through to the end of 1990s but gradually lost its competitive advantage to the emerging industry in South Korea which had the advantages of much cheaper wages, strong government backing and a cheaper currency. South Korean production overtook Japan's in 2003 and Japanese market share has since fallen sharply.
The Philippines has placed fourth among shipbuilding nations around the world producing more than six million deadweight tonnes of ships built in 2012. The country is anchored by South Korean Hanjin and Japan's Tsuneishi shipbuilders. The country has shipyards in Subic and Cebu.
The market share of European ship builders began to decline in the 1960s as they lost work to the Japanese in the same way as Japanese builders have lost work to South Koreans more recently; Europe's production is now a tenth of South Korea's and is primarily military, although cruise liners and some cargo ships are still built in Italy, Finland, France, Germany and Denmark. The largest shares of the European shipbuilding market belong to Germany, Italy, Norway, the Netherlands and Spain, which accounted in 2010 for over 70% of total deliveries by the yards. This activity accounted in 2010 for 1.5% of European GDP. Over the four years from 2007, the total number of employees in the European shipbuilding industry declined from 150,000 to 115,000. The output of the United States also underwent a similar change
Modern shipbuilding makes considerable use of prefabricated sections. Entire multi-deck segments of the hull or superstructure will be built elsewhere in the yard, transported to the building dock or slipway, then lifted into place. This is known as "block construction". The most modern shipyards pre-install equipment, pipes, electrical cables, and any other components within the blocks, to minimize the effort needed to assemble or install components deep within the hull once it is welded together.
Ship design work, also called naval architecture, may be conducted using a ship model basin. Modern ships, since roughly 1940, have been produced almost exclusively of welded steel. Early welded steel ships used steels with inadequate fracture toughness, which resulted in some ships suffering catastrophic brittle fracture structural cracks (see problems of the Liberty ship). Since roughly 1950, specialized steels such as ABS Steels with good properties for ship construction have been used. Although it is commonly accepted that modern steel has eliminated brittle fracture in ships, some controversy still exists. Brittle fracture of modern vessels continues to occur from time to time because grade A and grade B steel of unknown toughness or fracture appearance transition temperature (FATT) in ships' side shells can be less than adequate for all ambient conditions
All ships need maintenance and repairs. A part of these jobs must be carried out under the supervision of the Classification Society. A lot of maintenance is carried out while at sea or in port by ship's staff. However a large number of repair and maintenance works can only be carried out while the ship is out of commercial operation, in a Shiprepair Yard. Prior to undergoing repairs, tankers must dock at a Deballasting Station for completing the tank cleaning operations and pumping ashore its slops (dirty cleaning water and hydrocarbon residues).
, one of the oldest branches of engineering, is concerned with constructing the hulls of boats and, for sailboats, the masts, spars and rigging.
Anchor- a heavy, pick like device, attached to a boat's stem by a warp and chain. Common types are Plow or Fisherman and Danforth. Modern anchors are made of steel but in pre-industrial societies rocks were used. The chain is added to the lower anchor end to add weight and prevent chafing of the rope warp on rocks or shellfish beds.
Angel also virgin or maiden. A Viking invention used in sailing long ships from about the 10th century AD that predates blocks. They served the purpose of a block/jamb cleat in one unit. It was a flat section of wood about 150 high x 120 wide shaped like an angel/butterfly used in attaching stays to the hull. The V-shape at the lower part of the "wings" acted as a V jam cleat.
Bitts - Two short strong posts often made of steel, located on the fore and aft side decks of a heavily built boat or ship, that are designed to take heavy mooring lines.
Bilge - the lowest part of the hull interior, under the sole. Often water and or fuel tanks are placed in the bilges to lower the centre of gravity.
Bilge keel - a longitudinal, external, underwater member used to reduce a ship's tendency to roll
Bilge pump - a pump, either manual or electric with the inlet set at the lowest point in the bilges where water will collect when the boat is upright. The inlet is protected by a screen to stop blockages
Block a fitting with a circular wheel inside 2 cheeks designed to hold the turn of a rope. Originally made of wood, they are now made of plastic, stainless steel or carbon fibre. They are mainly used in rigging in pairs or quads to allow a single person to operate a sail that creates a lot of force. Similar to a pulley or sheave.
Bow - The front and generally sharp end of the hull. It is designed to reduce the resistance of the hull cutting through water and should be tall enough to prevent water from easily washing over the deck of the hull.
Bowsprit - A spar that extends forward from the foredeck, outboard of the hull proper. Common in square rigged ships where they were used to attach the outer or flying jib. In modern sailboats they are often made of lightweight carbon and used for attaching the luff of lightweight down-wind sails.
Breasthook - A roughly triangular piece of wood fitted immediately aft of the stem and between the two inwales or sheer clamps usually in a wooden dinghy.
Bulkhead - The internal transverse walls of the hull.
Bulwarks - The upstanding part of the topsides, above the deck, providing safe footing when a boat is heeled.
Cam cleat- a mechanical cleat with 2 spring loaded cam jaws, usually made of hard plastic, that clamp onto a sheet. The sheet can be easily pulled forward and upwards to release it but is held tight in the cam jaws when unattended.
Catsheads - A short timber(or pair of timbers) that protrudes approximately at right angles from the foredeck of a square rigged sailing ship. Its purpose is to support the weight of the anchor and keep the anchor secure and outboard of the hull to avoid Capstan A vertical metal or wooden winch secured to the foredeck of a ship, used for hoisting the anchor. Capstans may be manually operated or powered hydraulically or electrically. A traditional wooden capstan is fitted with removable wooden arms fitted into sockets on which the seaman push. Seashanties were often chanted to keep the seamen together as they pushed.
Carlin - A longitudinal strip parallel to, but inboard of, the inwale (sheer clamp). It supports the inboard edge of the side deck and the side of the cabin cladding.
Chainplate - A strip of strong metal, often stainless steel, through-bolted to the topsides and a frame and protruding above deck level to take the load of a stay in a sail boat.
Centre board - (also dagger board) an elongated underwater appendage that fits vertically in the slot of a centre case and extends below the hull. It can be retracted so the boat can float in very shallow water. The board has a length to breadth ratio of about 4;1. The board is tapered to a hydrodynamic (teardrop) shape in plan section to promote laminar flow of the water. This shape prevents stalling or eddying when sailing to windward. Together with the sails it lifts the hull in the windward direction. Common materials are wood often reinforced with fibreglass or carbon to obtain more stiffness and abrasion resistance. When sailing to windward the board is fully down but is retracted about half way when sailing directly down wind. When sailing to windward an efficient board prevents most leeway (sideways movement).
Chines - Are long, longitudinal strips on hydroplaning hulls that deflect downwards the spray that is produced by the hull when it travels at speed in the water. The term also refers to distinct changes in angle of the hull sections, where the bottom blends into the top sides of a flat, v or arc- bottomed boat such as a skiff, for instance. A multi chine hull has 4 or more chines to allow an approximation of a round bottomed shape using flat panels. It also refers to the longitudinal members inside the hull which support the edges of these panels.
Cleat - A fitting designed to tie off ropes. Often T shaped.
Coaming - any vertical surface on a ship designed to deflect or prevent entry of water
Cockpit - The seating area towards the stern of a small decked vessel where the rudder controls are located.
Counter stern - a traditional stern construction with a long overhang and a shorter, upright, end piece. The stern is rounded when in plan-view. The counter is usually decked over.
Companion way-in a small yacht this is the short ladder that leads from the cockpit to cabin or saloon. Often it is detachable for access to the engine or storage. In a large vessel it is a permanent ladder between decks. A companion way usually has non slip treads and handholds.
Crosstree- two short metal arms that are attached to a mast athwartwise about mid height. Mast side stays are tensioned by running through the outboard end of the arms, often forming a diamond shape. Similar to a spreader.
Deck - The top surface of the hull keeps water and weather out of the hull and allows the crew to operate the boat more easily. It stiffens the hull. Temporary frames (or moulds) can be removed and kept for another boat.
Deck beam - A heavy timber running athwartwise(across)from the top of a frame under the deck. It usually has a gentle convex (upward) curve for extra strength, extra head height below deck along the centre line and to allow water to run off the deck when the boat is upright.
Dolphin striker - A short spar fitted mid-way and vertically downwards, midway along a bowsprit that holds the bobstay and prevents the outboard end of the bowsprit riding upwards under the load of a tensioned headsail.
Dorade - A ventilation intake consisting of a cowling connected to a short vertical tube connected to a deck mounted scuppered (Dorade) box, usually made from teak. The cabin intake is offset to prevent water entering the cabin. The upper section swivels to stop breaking seas entering the dorade. Named after the 1931 yacht Dorade where it was first used.
Fairlead-A U shape or circular fitting often positioned near the bow that leads an anchor warp or a sheet to a cleat or winch. The anchor fairlead is usually bronze or stainless steel as it must take the regular abrasion of the warp and chain. The anchor fairlead is usually set on the change of angle between the deck and the topside to prevent wear and tear.
Fiddle-or fiddle rail. A low rail about 40mm high, either of solid wood or lathe turned fiddles that is designed to stop things sliding off a table at sea when the boat is healed.
Frame - the transverse structure that gives a boat its cross-sectional shape. Frames may be solid or peripheral. They may be made of wood, plywood, steel, aluminium or composite materials. They may be removed after construction to save weight or to be reused or left in-situ. In ancient shipbuilding the frames were put in after the planking but now most boats are built with the frames first. This gives greater control over the shape. "Lofting" is the process used to create life-size drawings of frames so they can be manufactured. Today frames can be cut directly from a computer programme by a robot, with extreme accuracy. In old heavily built, square rigged ships, the frames were made up of 4 individual timbers called futtocks, as it was impossible to make the shape from a single piece of wood. The futtock closest to the keel was the ground futtock and the other pieces were called upper futtocks.
Freeboard- the distance between the water line and the deck when loaded. Boats using sheltered waters can have low free board but seagoing vessels need high freeboard.
Furling headsail -a jib or other headsail that automatically rolls around a semi rigid forestay when a line is pulled. The lower section of the furling gear has a spring loaded retrieval system that rolls up the headsail. These are often used in cruising boats or when a yacht is sailed short-handed. The operating lines are operated from the safety of the cockpit avoiding crew working on the exposed foredeck. On very large yachts the furling gear is attached to an electric motor for ease of use.
Garboard - The strake immediately adjacent to the keel in a traditional wooden boat.
Gimbaled stove/compass-a pivoting apparatus that allows a stove or compass to swing in two planes at the same time so that it remains more or less level. This makes the compass needle steady and easier to read and allows food to be cooked (carefully) in seaway.
Gooseneck - a universal joint, usually made of stainless steel, that joins the boom to the mast. Many goose necks can be raised or lowered on a short section of track fixed to the mast.
Grab rail- a length of strong wood, often mahogany, or stainless steel tube, with short legs, through bolted to a cabin top, so that crew making their way forward on a sloping and wet side deck have a firm hand hold.
Gudgeon- a stainless steel fitting, attached to a rudder head, in pairs, with parallel holes in which the rudder pintle pivots .
Gunwale - The upper, outside longitudinal structural member of the hull.
Hatch - A lifting or sliding opening into the cabin or deck for the loading of cargo or people.
Heads - marine toilet. An abbreviation of the term catsheads which was the normal place of toileting in square rigger days. Always used in the plural.
Hull - The main body of a ship or other vessel, including the bottom, sides, and deck.
Hydrofoil-An inverted T or an L-shaped keel/dagger board device, with hydro dynamic lifting ability, that extends vertically downwards under the hull. As boat speed increases the hull lifts completely out of the water so drag is reduced and hull speed dramatically increased. The AC 72 ft catamaran New Zealand reached 40 knots in 17 knots of wind with almost no heeling, using hydrofoils in September 2012. Sometimes called foiling or foil sailing. Most commonly used in 11 feet Moth sail boats. Also used in powerboats.
Inwale - The upper, inner longitudinal structural member of the hull, to which topside panels are fixed. In USA this is usually called the sheer clamp.
Keel - The main central member along the length of the bottom of the boat. It is an important part of the boat's structure which also has a strong influence on its turning performance and, in sailing boats, resists the sideways pressure of the wind
Keelson - An internal beam fixed to the top of the keel to strengthen the joint of the upper members of the boat to the keel.
King plank - A flat, notched (nibbed) timber laid over the foredeck beams between the front of a cockpit or cabin and the stem. The notches or nibbs are designed so that the tapering deck planks do not end in a point which could be a weak point.
Knee - A short L shaped piece of wood that joins or strengthens boat parts that meet at about 60 to 120 degrees. It may be a natural crook (e.g. apple, oak, pohutukawa) or sawn from a larger length of timber or laminated in a wooden vessel. Commonly seen on thwarts to join topsides or keelsons to join transoms. A hanging knee fits upside down e.g. underneath a thwart rather than on top. Hanging knees often support carlins where a full frame would be inconvenient.
Locker - an enclosed space to store sails, anchors, personal effects, tools and supplies
Mast - A vertical pole on a ship which supports sails or rigging. If a wooden, multi-part mast, this term applies specifically to the lowest portion.
Mast step - A socket, often strengthened, to take the downward thrust of the mast and hold it in position. May be on the keel or on the deck in smaller craft.
Moon pool - An opening in the bottom of the hull giving access to the water below, allowing access to the sea
Mizzen-the permanent mast and sail set aft in a sailboat with 2 or more masts.
Newel Post- turned wooden posts, from floor to ceiling, to one side of the cabin in a yacht. Serves as a hand hold when a boat is at sea.
Oar A wooden pole flattened at the outboard-end so it grips the water when pulled. Oars are normally used in pairs to propel a rowboat forward. Differs from a paddle by being longer and gaining leverage by passing through a rowlock which acts as a fulcrum to produce forward motion. Modern oars are often made from plastic or hollow carbon fibre in racing oars. A single oar can be leveraged against a U shape notch in the stern of a row boat to scull. The sculler stands and moves the oar in a sideways motion to produce forward motion in calm waters. A balanced oar is one that has weight added (either by extra wood or lead inside the handle)to the inboard end to balance the additional outboard length. In a rowing dinghy with 7–8 feet oars the balance point is about 12 inches outboard of the rowlocks.
Painter-a short rope tied to the bow of a small boat, which can be held by a person. Used to control a boat while unloading from a trailer or loading/unloading from a beach.
Parrot beak-a stainless steel fitting on the end of a spinnaker pole, consisting of a mounting with a retractable spring loaded pin that is controlled remotely by way of a cord. When the cord is pulled it releases the spinnaker sheet so the spinnaker can be recovered by crew on deck.
Pintle a short section of stainless steel rod, about 6-12mm in diameter, mounted on a stainless steel bracket, that is bolted to the transom of a sail boat, so that the pin is inserted in the gudgeon hole.
Planing Plank - a narrow, flat bottom keel about 150mm wide on a high speed deep or medium V powered planning craft. In flat water the craft would plane on this narrow plank giving increased speed. In choppy water the ride was unsettled. Steering accuracy when cornering was difficult as the craft swung wide. A concept used in power craft in the 1970s and 1980s but replaced by deeper V hulls with angles of more than 21 degrees from the 1990s.
Prod- a very strong, light, hollow tapered pole, often made of carbon fibre, attached to the bow of a modern racing yacht, enabling it to carry a spinnaker or other down-wind sail with the luff in line with the centreline of the boat. In some yachts, such as the modern 49er, the prod is retracted through a hole in the bow when sailing upwind. Larger prods, such as on an AC72, are secured by dolphin strikers to prevent the prod bending upwards or breaking.
Ratlines (sometimes ratlins) - Groups of side stays on a square rigged ship that have horizontal lines placed for feet, enabling crew to rapidly ascend to the yards.
Rib - A thin strip of pliable timber laid athwart-wise inside the hull, from inwale to inwale, at regular close intervals to strengthen the exterior planking. The rib is often steamed to increase flexibility. The rib is traditionally fixed to the planking by rivets or copper nails bent over on the inside. This method is still used in small clinker built dinghies and similar craft. Ribs are attached after the planking is constructed. Ribs differ from frames or futtocks in being far smaller dimensions and bent in place compared to frames or futtocks which are normally sawn to shape, or natural crooks that are shaped to fit with an adze, axe or chisel.
Rigging- wire or rod used to hold up a mast. Since the 1960s stainless steel wire has become universal in the developed world. Elsewhere galvanized wire or even rope may be used because of its availability and cheapness.3 types of stainless steel wire are commonly used. Type 1 x 19 is a non-flexible wire used for standing rigging such as stays. Type 7 x 7 is a semi flexible wire used for luff wires in sails, halyards (sometimes plastic coated) trapeze wires and light halyards. Type 7 x 19 is used for all halyards, wire sheets, vangs and strops that must run through a pulley (sheave). The common way of attaching wire is to form a small loop at the end which is fixed in place by clamping a soft metal swage over the free ends. Talurite is a common brand of swagging. The wire loop is then fastened to a rigging screw with a bow shackle to the chain plate. Kevlar rope is sometimes used in place of wire in small sailboats.
Rowlock - Pronounced Rolick. A 'U' shaped metal device that secures an oar and acts as a fulcrum during the motion of rowing. Sometimes called an oarlock in the USA. The Rowlock is attached with a swivelling pin to the gunwale in a row boat. Commonly made from galvanized steel, bronze or plastic. Before the availability of metal the oar was normally levered against 2 wooden pins called Thole pins inserted in the gunwale. Tholepins are still used in some third world nations. In a narrow row boat the rowlocks are held well outboard in a lightweight outrigger (rigger) which is often equipped with a locking pin to hold the oar securely.
Rudder - A steering device usually at the rear of the hull created by a turn-able blade on a vertical axis
Sampson post - A strong vertical post used to support a ship's windlass and the heel of a ship's bowsprit.
Scuppers - Gaps in the bulwarks which enables sea or rain water to flow off the deck.
Shackle - a small, U shape, stainless steel or galvanized steel secured with a screw type pin at the open end of the U. Some types have spring loaded pins that snap shut.
Sheave box - a plastic or stainless steel box that holds a pulley that is fixed in position such as on a mast head so that the angle of the rope (halyard)is restricted.
Sheer - The generally curved shape of the top of the hull when viewed in profile. The sheer is traditionally lowest amidships to maximize freeboard at the ends of the hull. Sheer can be reverse, higher in the middle to maximize space inside, or straight or a combination of shapes.
Sensor - A small electronic component which can be embedded in a hull skin, keel, rudder, mast, oar or sail of a very-high-performance craft to measure the laminar flow of air or water. Pioneered in New Zealand using technology from Formula 1 racing. Now used in rowing skiffs or racing oars to determine forces such as bending load and optimum angle of attack of the blade. Larger craft such as America Cup boats have readout displays on board so minute changes in sail angle can be related to speed and then duplicated at a later date.
Sheet - A rope used to control the position of a sail e.g. the main sheet controls the position of the main sail.
Skeg - A long tapering piece of timber fixed to the underside of a keel near the stern in a small boat to aid directional stability, especially in a kayak or rowboat.
Spar - A length of timber, aluminium, steel or carbon fibre of approximately round or pear shape that is used to support sails. Such as a mast, boom, gaff, yard, bowsprit, prod, boomkin, pole or dolphin striker .
Sole-the floor of a cabin or cockpit. Often the cabin floor is made in sections that can be lifted quickly to gain access to the bilges in the event of a leak. Cockpit floors on yachts are often self-draining so that water will drain out even when the vessel is sailing at an extreme angle. In many high speed skiffs the craft is fitted with a sole angled aft to rapidly drain the spray through an open transom. Often this type of sole is called a false floor.
Spinnaker- sometimes called a kite in Australia or New Zealand. A large, lightweight, down-wind sail used on fore and aft rigged yachts such as sloops to dramatically increase sail area. The sail is hoisted by a halyard attached by a ring to the head of the sail. The windward, luff, corner is secured by a sheet often called a preventer. The preventer runs through a parrot beak attached to the end of a spinnaker pole. Until recently the pole was usually secured by a parrot beak to a ring on the lower mast. The leeward, clew, corner is controlled by a sheet. In double luff (parallel sided) spinnakers, the 2 sheets are interchangeable. In some very modern racing yachts the pole is replaced by a prod which is fixed in place at the bow. Some spinnakers are single luff, which are flatter and with a longer luff enabling them to be carried more easily on a reach. In small planning sailboats such as 18 ft skiffs, huge spinnakers cause dramatic increases in speed and spectacular, on the edge, sailing.
Spreaders- two angled, metal struts, attached about mid height on a mast, for the purpose of keeping the side stays taunt. Spreaders are usually swept rearwards approximately in line of the side stay between the hounds and the chain plate. They help hold the mast straight (in column) when under heavy load such as when carrying a spinnaker on a tight reach.
Spring - The amount of curvature in the keel from bow to stern when viewed side on. The modern trend is to have less spring in order to have less disturbance to water flow at higher speeds to aid planing.
Stanchions - A series of narrow but strong posts, often made of marine grade stainless steel, designed to hold life lines around the outer edge of a deck. Stanchions are often attached to both the deck and a toe rail or bulwark for added strength.
Stainless steel- mild steel to which small percentages of copper, chromium and sometimes nickel are added to make a very strong steel that is does not rust much. Marine grade stainless steel 316 containing more nickel, is even more rust resistant. Can be made into rod, tubes, sheet or pressed into a wide variety of shapes for marine fittings.
Stays/shrouds - Standing or running rigging which hold a spar in position e.g. sidestay, forestay, backstay. Formerly made of rope, these days usually stainless steel wire.
Stem - A continuation of the keel upwards at the front of the hull
Stern - The back of the boat
Stern sheets a flat area or deck, inboard of the transom in a small boat. It may contain hatches to access below decks or provide storage on deck for life saving equipment.
Strake - A strip of material running longitudinally along the vessel's side, bilge or bottom. Sometimes called a stringer.
Stringer-Batten in USA. A long relatively thin, knot free length of wood, running fore and aft, often used to reinforce planking on the inside of the hull, especially when thin planking is used.See strake
Synthetic rope - There are 4 common ropes in use. Polyester, also called Dacron or Terylene, is a strong, low stretch rope, usually plaited (braided) used for running rigging. Nylon is a strong, but elastic rope, used for mooring lines and anchor warps as it resists shock loads. It is usually laid (twisted) so that it is easier to grip when hauling. Polypropylene is a light, cheap, slippery rope, that floats. It is much weaker than the previous ropes. It weakens when exposed to sunlight. It is usually laid construction. Commonly used on commercial fishing boats using nets. Kevlar is an extremely strong fibre that is now made into ropes with almost no stretch. Expensive. Suited to halyards instead of stainless steel wire. Often used on racing yachts to replace polyester when powerful winches are used. Kevlar ropes can be much smaller in diameter than polyester for the same strength. This saves windage on a racing yacht. Usually braided.
Taff rail-a railing, often ornate, at the extreme stern of a traditional square rigged ship. In light air conditions an extra sail was set on a temporary mast from the taff rail.
Thwart - A seat, usually transverse, that is used to maintain the shape of the topsides in a small boat.
Tiller- A handle made of wood, steel or carbon fibre that is attached to the top of a rudder, often via a post, which enables the helmsman to steer the boat.
Tiller extension-A long, lightweight handle attached to the forward end of the tiller which enables the helmsman to steer from a position from the side deck or outboard of a side deck on a high performance yacht. For example from a trapeze.
Toe rail - A upright longitudinal strip of timber fastened to the foredeck near the sheer. It is placed so that crew working on the foredeck can brace their toe or foot against it especially when the boat is heeled.
Topsides - The side planking of a boat from the waterline to the sheer.
Transom - A wide, flat or slightly curved, sometimes vertical board at the rear of the hull, which, on small power boats, is often designed to carry an outboard motor. Transoms increase width and also buoyancy at the stern. On outboard boats the stern is often the widest point to provide displacement to carry a large outboard and to resist the initial downward thrust of a planning craft. Sometimes the term tuck is used in a sail boat.
Trapeze- a wire and belt device allowing a crew member to lie near horizontal with their feet braced against the gunwhale in order to counter act the healing force of the wind acting on the sails of a centre board racing yacht. A thin stainless steel wire is attached to the mast at about 3/4 height and to a belt worn by the crew member via a hook. When tacking the sailor must swing in, unhook, move to the other side of the yacht and reattach the hook on the opposite tack. Agility is required. The crew holds the tail of the jib sheet for trimming and balance. In a few classes the helmsman and/or helmsman and all crew, use trapezes.
Washboard - a panel that slides vertically in small boat's companionway acting as a removable door
Warp-anchor rope. Traditionally made of natural fibre such as hemp, modern warps are made of stronger, lighter, synthetic fibre, often laid nylon, which is elastic so absorbing shock loads which would otherwise pull out the anchor. Warps are normally at least 3 times the depth of the water. In strong wind and/or current the warp should be at least 6 times the water depth.
Water tank - a large irregular shaped container(s), often made of stainless steel, that is usually fitted into the bilges of a voyaging boat. The tank often has a deck mounted inlet, a vent pipe and a pump to move water to taps, showers etc. Mounted low in the hull, it adds significantly to stability when full.
Winch-a geared mechanical device used on yachts for trimming (adjusting)sail sheets, for hoisting large sails with halyards, for hauling in an anchor or on a boat trailer for hauling a boat out of the water. The normal turret winch is set on the aft side deck for trimming headsails and or a spinnaker. Manual trimming winches are operated by grinding the handle in a circle initially, then pulling back and forwards on a short lever while a second person tails (pulls to keep tension on the sheet)to obtain optimum force. Some winches are self-tailing or the sheet can be cleated to prevent slippage. On larger yachts winches can be operated by electric motors. Typically on America's cup yachts large pedestal winches are used which can be operated by two people at the same time. Because of the force needed, especially in tacking duels, winch grinders are usually very large and strong men.
Wind pennant-a small wind indicator balanced on a pivot, usually fitted to the mast head, to indicate wind direction. Can be made of plastic, stainless steel or sail cloth.
Wheelhouse - a permanent, raised shelter, with large windows, often located midships or aft, from which the helmsman steers. Usually contains all the boats controls, instruments and electronics. It gives the helmsman good visibility 360 degrees and keeps them out of bad weather and spray. The wheelhouse may be open aft or have access to the side decks so when operating short-handed the helmsman can attend lines.
Yard - A heavy spar fitted to a square rigged ship. Each square sail hangs from its own yard. Sails are furled by seamen who bend over the yard and use both hands to haul up the sail. The yard's position is altered by sheets leading from the ends of the yard down to the deck.
Construction materials and methods
Wood - The traditional boat building material used for hull and spar construction. It is buoyant, widely available and easily worked. it is a popular material for small boats (of e.g. 6-metre length; such as dinghies and sailboats). Its abrasion resistance varies according to the hardness and density of the wood and it can deteriorate if fresh water or marine organisms are allowed to penetrate the wood. Woods such as Teak, Totara and some cedars have natural chemicals which prevent rot whereas other woods, such as Pinus radiata, will rot very quickly. The hull of a wooden boat usually consists of planking fastened to frames and a keel. Keel and frames are traditionally made of hardwoods such as oak while planking can be oak but is more often softwood such as pine, larch or cedar. Plywood is especially popular for amateur construction. More recently introduced tropical woods as mahogany, okoumé, iroko, Keruing, azobé and merbau. are also used. With tropical species, extra attention needs to be taken to ensure that the wood is indeed FSC-certified. Teak or iroko is usually used to create the deck and any superstructure. Glue, screws, rivets and/or nails are used to join the wooden components. Before teak is glued the natural oil must be wiped off with a chemical cleaner, otherwise the joint will fail.
Some types of wood construction include:
Carvel, in which a smooth hull is formed by edge joined planks attached to a frame. The planks may be curved in cross section like barrel staves. Carvel planks are generally caulked with oakum or cotton that is driven into the seams between the planks and covered with some waterproof substance. It takes its name from an archaic ship type and is believed to have originated in the Mediterranean. A number of boat building texts are available which describe the carvel planking method in detail.
clinker is a technique originally identified with the Vikings in which wooden planks are fixed to each other with a slight overlap that is beveled for a tight fit. The planks may be mechanically connected to each other with copper rivets, bent over iron nails, screws or in modern boats with adhesives. Often, steam bent wooden ribs are fitted inside the hull.
Strip planking is yet another type of wooden boat construction similar to carvel. It is a glued construction method which is very popular with amateur boatbuilders as it is quick, avoids complex temporary jig work and does not require shaping of the planks.
Sheet plywood boat building uses sheets of plywood panels usually fixed to longitudinal long wood such the chines,inwhales(sheer clamps)or intermediate stringers which are all bent around a series of frames. By attaching the ply sheets to the longwood rather than directly to the frames this avoids hard spots or an unfair hull. Plywood may be laminated into a round hull or used in single sheets. These hulls generally have one or more chines and the method is called Ply on Frame construction. A subdivision of the sheet plywood boat building method is known as the stitch-and-glue method, where pre-shaped panels of plywood are edge glued and reinforced with fibreglass without the use of a frame. Metal or plastic wires pull curved flat panels into three-dimensional curved shapes. These hulls generally have one or more chines.Marine grade plywood of good quality is designated "WBP" (which stands for water- and boiled-proof) or more usually BS 1088. Both types of plywood construction are very popular with amateur builders, and many dinghies such as the Vaurien, Cherub, Moth and P class (ply on frame construction) and FJs, FDs and Kolibris[disambiguation needed] (stitch-and-glue method) have been built from it. Another variation is tortured ply where very thin(3mm) and flexible (often Okoume)preshaped panels ply are bent into compound curves and sewn together. Little or no framework or longitudinal wood is used. This method is mainly confined to kayaks.
Cold-Molding is a composite method of wooden boat building that uses 2 or more layers of thin wood, called veneers, oriented in different directions, resulting in a strong monoque structure, similar to a fibreglass hull but substantially lighter. Usually composed of a base layer of strip planking followed by multiple veneers, cold-molding is popular in small, medium and very large, wooden super-yachts. Using different types of wood the builder can lighten some areas such as bow and stern and strengthen other high stress areas. Sometimes cold moulded hulls are protected either inside or out or both with fibreglass or similar products for impact resistance especially when lightweight, soft timber such as cedar is used. This method lends itself to great flexibility in hull shape.
Steel (and before that iron) - Either used in sheet or alternatively, plate for all-metal hulls or for isolated structural members. It is strong, but heavy (despite the fact that the thickness of the hull can be less). It is generally about 30% heavier than aluminium and somewhat more heavy than polyester. The material rusts unless protected from water (this is usually done by means of a covering of paint). Modern steel components are welded or bolted together. As the welding can be done very easily (with common welding equipment), and as the material is very cheap, it is a popular material with amateur builders. Also, amateur builders which are not yet well established in building steel ships may opt for DIY construction kits. If steel is used, a zinc layer is often applied to coat the entire hull. It is applied after sandblasting (which is required to have a cleaned surface) and before painting. The painting is usually done with lead paint (Pb3O4). Optionally, the covering with the zinc layer may be left out, but it is generally not recommended. Zinc anodes also need to be placed on the ship's hull. Until the mid-1900s, steel sheets were riveted together.
Aluminium - either used in sheet for all-metal hulls or for isolated structural members. Many sailing spars are frequently made of aluminium after 1960. The material requires special manufacturing techniques, construction tools and construction skills. It is the lightest material for building large boats (being 15-20% lighter than polyester and 30% lighter than steel). Aluminium is very expensive in most countries and it is usually not used by amateur builders. While it is easy to cut, aluminium is difficult to weld, and also requires heat treatments such as precipitation strengthening for most applications. Corrosion is a concern with aluminium, particularly below the waterline. It is most commonly used in small pleasure and fishing power boats that are not kept permanently in the water.
(Glass-reinforced plastic or GRP
) - Typically used for production boats because of its ability to reuse a female mold as the foundation for the shape of the boat. The resulting structure is strong in tension but often needs to be either laid up with many heavy layers of resin-saturated fiberglass or reinforced with wood or foam in order to provide stiffness. GRP
hulls are largely free of corrosion though not normally fireproof. These can be solid fiberglass or of the sandwich (cored) type, in which a core of balsa, foam or similar material is applied after the outer layer of fiberglass is laid to the mold, but before the inner skin is laid. This is similar to the next type, composite, but is not usually classified as composite, since the core material in this case does not provide much additional strength. It does, however, increase stiffness, which means that less resin and fiberglass cloth can be used in order to save weight. Most fibreglass
boats are currently made in an open mold, with fibreglass and resin applied by hand (hand-lay-up method). Some are now constructed by vacuum infusion where the fibres are laid out and resin is pulled into the mold by atmospheric pressure. This can produce stronger parts with more glass and less resin, but takes special materials and more technical knowledge. Older fibreglass boats before 1990 were often not constructed in controlled temperature buildings leading to the widespread problem of fibreglass pox, where seawater seeped through small holes and caused delamination. The name comes from the multiude of surface pits in the outer gelcoat layer which resembles smallpox. Sometimes the problem was caused by atmospheric moisture being trapped in the layup during construction in humid weather.
Composite - Originally "composite" referred to a timber carvel skin fastened to iron frame and deck beams. This allowed sheet copper anti-fouling to be employed without the risk of galvanic corrosion of the hull fabric. It was employed for fast cargo vessels so that they were not slowed by marine fouling. This use is now obsolete. While GRP
, wood, and even concrete hulls are technically made of composite materials, the term "composite" is often used for plastics reinforced with fibers other than (or in addition to) glass. Cold-molded refers to a type of building one-off hulls using thin strips of wood applied to a series of forms at 45-degree angles to the centerline. This method is often called double-diagonal because a minimum of two layers is recommended, each occurring at opposing 45-degree angles. "Cold-molding" is now a relatively archaic term because the contrasting "hot-molded" method of building boats, which used ovens to heat and cure the resin, has not been widely used since World War II . Now almost all curing is done at room temperature. Other composite types include sheathed-strip, which uses (usually) a single layer of strips laid up parallel to the sheer line. The composite materials are then applied to the mold in the form of a thermosetting plastic (usually epoxy, polyester, or vinylester) and some kind of fiber cloth (fiberglass, kevlar, dynel, carbon fiber, etc.), hence the finished hull is a "composite" of fiber and resin. These methods often give strength-to-weight ratios approaching that of aluminum, while requiring less specialized tools and skills.
Steel-reinforced cement (ferrocement) - Strong, long lasting and very heavy. First developed in the mid 19th Century in France. Used for building warships. Extensively refined in New Zealand shipyards in the 1960s and the material became popular among amateur builders of cruising sailboats in the 1970s and 1980s, because the material cost was cheap, although the labour time element was high. The weight of a finished ferro-cement boat is much higher than most wooden boats. As such they are often built for slower, more comfortable sea passages. Hulls built properly of ferro-cement are more labor-intensive than steel or fiberglass, so there are few examples of commercial shipyards using this material. The inability to mass-produce boats in ferro-cement has led there to there being few examples around. Many ferro-cement boats built in back yards can have a rough, lumpy look, which has helped to give the material a poor reputation. The ferro-cement method is easy to do, but it is also easy to do wrong. This has led to some disastrous 'home-built' boats. Properly designed, built and plastered ferro-cement boats have smooth hulls with fine lines. Amateur builders are advised to use a professional plaster to produce a smooth finish. Most ferro-cement hulls are designed as heavy displacement. See also concrete ship, concrete canoe.
To build a boat, the type of hull used is of vital importance; for example, going to sea requires a hull which is more stable than a hull used for sailing rivers (which can be more flat/round). Some types include:
Smooth curve hull - As its name implies, the hulls of these vessels are rounded and don't usually have any chines or corners.
Chined and hard chined hulls - These are hulls made up of flat panels (commonly made of plywood, or more traditionally with planking) which meet at a sharp angle known as the chine. Chined hulls range from simple flat-bottomed boats where the topsides and bottom meet at about 110 degrees (such as banks dories and sharpies) to skiffs where the bottom is arced rather than flat. Multi-chine plywood hulls allow a round hull shape to be approximated.
Flat-bottomed hull - The flat-bottomed hull has advantages, such as the ability to travel in shallower water and being cheap and easy to build, though it is much less stable in rough waters than other hull types.
Displacement hulls - These are hulls which have a shape which does not promote planing. Displacement hulls are often heavy and lack sufficient power -either motor or sail to achieve planning. They travel through the water at a limited rate which is defined by the waterline length.
Planing hulls - These are hulls with a shape that allows the boat to rise higher and higher out of the water as the speed increases. They are commonly fine bowed. Sail boats that plane are flat-bottomed aft. Because sail boats sail healed the flat surface can be achieved with v or arc bottom shapes. Hydroplanes are very light, flat bottomed, high powered speed boats that plane easily on flat water but quickly become unstable in any waves. Powerboats designed for rough water are usually deep V-bottomed with a deadline angle of about 20-23 degrees. The most common form is to have at least one chine to allow for stability when cornering and for a supportive surface on which to ride while planing. Planing hulls allow much higher speeds to be achieved, and are not limited by the waterline length the way displacement hulls are. They require more energy in the form of large sails or high power motors plus light weight to achieve these speeds.
Boat building tools and use
Boat building uses many or the same tools that are common house tools such as hammers, cross cut saws, power drills, benches and vices. For building small boats under 5m some specialized tools are needed such as clamps (cramps) either G clamps or spring clamps. A minimum of 4 6inch(150mm) and 10 4inch(100mm) G clamps, plus 20 2 inch(50mm) steel spring clamps is need for ply on frame designs. More is better with clamps. Flat and round surform rasps are useful tools for shaping wood and ply. A drill set from 2-10mm, several speedbore drills for larger holes 12-25mm, (1/2inch-1 inch) rotary sanding backing pads and a range of replacement sanding pads from coarse (40grit) to fine (180grit), counter sinking drills for screws, a right angle set square, a set of manual screw drivers with blades to match screws being used are essential. A heavy craft knife, an 8m(25 ft) tape, flat and round files for metal and wood, a short(torpedo) level and a set of 3 chisels from 6 to 25mm are needed. Power tools make a job much easier and are relatively cheap. An 7 1/4inch (185mm) circular saw with a fine 40 tooth tungsten carbide blade, a jigsaw with a dust blower with a set of fine, medium and coarse tooth metal and wood blades is good for cutting plywood panels to shape, a rotary oscillating sander with medium and fine pads and a cordless drill for driving screws all save time and energy. A steam box is excellent for making planks easier to bend although hot wet rags are a messy, but easy substitute. A fine tooth hacksaw is not only essential for cutting metal such as trimming stainless steel bolts to the correct length but is handy for ultra-fine cuts in thin wood. A fine-tooth tenon saw is used to cut across the grain to produce a reasonably fine, accurate cut. Some boat builders have started using Japanese draw saws for fine cuts but while these are excellent they tend to be very expensive. A No 4 smoothing plane is essential but an electric plane is very useful (but extremely loud) for making rudder blades and centre boards. A much longer No. 7 plane is needed if the design calls for a wooden spars as used in many modern "traditional" yachts.
In boat building lots of sanding requires using either dry sandpaper, or wet and dry paper, to achieve a reasonable paint or varnish finish. Sandpaper is graded from 40 (very coarse) to 400 (ultrafine). Wet and dry sandpaper lasts longer than dry sandpaper. Wet and dry is best used on paint finishes, while dry paper is best used on dry wood. About 2 sheets of sandpaper for every foot of hull length is a good guide. Less sheet sandpaper is needed if power sanders are used. Spatula applicators, with a flexible stainless steel blade, are used to apply filler. A knife type and a flat 3"(75mm) type will cover most needs.
Silicon bronze screws are normally used in boat building but can be hard to locate. Brass fasteners are commonly available but apart from being softer and weaker the common brass alloys are much more prone to corrosion through depletion of their zinc content. Stainless steel screws may be used for attaching fittings to the hull above the water line. Type 316 stainless steel is the only stainless steel recommended. Even 316 may get stained with surface rust but this does not penetrate the surface. Staining comes from being in contact with other steels such as the anchor or incorrect cleaning in the factory. Staining near wields should be removed as it can pit. Experienced boat builders are reluctant to use even 316 below the water line in a boat permanently in salt water. This especially applied to long thin fastenings such as screws in boats that have motors. Sacrificial anodes are used to help prevent corrosion underwater but experts will inspect a sample of long thin screws or bolts annually to check for corrosion.
glue with its associated fillers is universally used in boat building due to its far superior holding power and ease of use. In its thickened state it is used as a strong filler and for a range of joints that do away with more traditional fastenings. A large supply of cheap wooden tongue depressors is useful for mixing and applying epoxy resin. The curved ends are useful for shaping coved joints with epoxy. Silicon bronze ring nails are excellent for permanent fastening of wood and ply as they are strong and easily driven. Many small boats are almost entirely fastened by epoxy resin. In stitch and glue construction the hull panels are temporarily held together with either copper wire, nylon fishing line or plastic cable ties, until the epoxy cures, after which the stitching material is removed. Polyester filler is a quick setting (20mts), softer filler, suited to very small holes and scratches and is far more easily sanded to a fair shape than harder, stronger epoxy filler which takes 24 hours to set hard.
requires enough space, under cover, so that the builder can easily move around the hull during construction, or the boat can be built on a trailer so the hull can be moved out of the shelter for construction sessions. It also requires space at the bow and stern not only for working but for sighting down the gunwale and chine lines to check they are fair. Have the bow at the garage door end for this reason. This is especially important in stitch and glue construction where no jig is used, as the ply panels are very floppy until the glue sets.
Water based paint is far easier and cheaper to apply, as undercoat, to produce a good smooth finish with a fraction of the time and effort of enamel paints but harder and slower drying enamel is best for the top coat on the outside of the hull which is subject to a lot of bumps and scraps. Limit varnishing to smaller areas, such as grab rails, hatches, toe rails and trim, unless you have lots of patience and a very dust free environment for varnishing. Use only Marine Gloss varnish on the outside, as interior varnish will peel off very quickly in hot sun and rain. Marine varnish has UV inhibitors to slow down peeling and fading. Never varnish a deck as it is slippery when wet. Even top quality marine varnish is not as water resistant as paint so you must apply at least 4 coats minimum. Often perfectionists will apply 8 coats or more to get a glass like, reflective finish. Never varnish submerged parts like rudders.
Boats take a long time to build as there are almost no right angles. Amateurs working at night or in weekends commonly take a year to build a 12–16 ft (3.6–5m) craft. Builders with handyman skills will find that over time their skills will increase. For amateurs, starting with a boat built on a jig ( temporary wooden frame)is useful as making the jig is all about right angles and basic carpentry skills. Sail boats require about 25% more time than a dinghy type because of the need for built in buoyancy, centreboard case, centreboard, rudder, mast, boom and a range of special fittings such as chain plates, gudgeons, blocks cleats and tracks.
Essential safety gear needed is closed in footwear, very high grade air protectors (especially if using a high revving electric plane or router),eye shields when cutting or grinding metal, disposable gloves when gluing, close fitting clothes that will not get caught in drills. Good light is essential. Boat builders should not work when they are tired and should keep the work floor clean so they don't trip over tools or wood or electric leads. A fan is handy for extra ventilation if the work space does not have many opening windows or doors. Many boat builder like smaller tools to be bright coloured tools so they can see them easily amongst saw dust.
Other useful power tools are a belt sander, especially if using recycled timber or for finishing rough sawn timber. A thicknesser is only needed if building many boats or larger vessels as it is usually cheaper to pay a joiner to do this for a small amount of timber. A bench saw is useful if you buy larger sectioned timber, which may be considerably cheaper and need to saw it to the correct size, but again a timber yard will do this for a small charge
Future boat developments
Two aims of future boat development are fuel efficiency through reduction of drag and protection of the environment against pollution through use of 'cleaner' fuel sources.
Professor James J. Corbett of the University of Delaware has suggested that a 20–30% GHG-emissions reduction for shipping is possible and may occasion economical and health benefits
Reduction in drag may offer significant fuel efficiency. Advancements in technology such as aluminum alloys or carbon-fiber composites may reduce hull weight (and hence displacement and drag) for a given payload
A bulbous bow is a protruding bulb at the bow of a ship. It is positioned just below the waterline to modify the way water flows around the hull. Large ships with bulbous bows have a twelve to fifteen percent better fuel efficiency than similar vessels without them. Drag may be reduced by decreasing the effective wetted area of the hull. In Skjold class patrol boats this is achieved by augmenting the buoyancy by incorporating a fan-blown skirted compartment between the two rigid catamaran-type hulls. This design permits lower displacement and therefore reduced drag at high speeds. A related concept is the Air Cavity System. Creating an air cavity on the underside of a hull may reduce drag by up to 15%
Wind power has been used to propel watercraft since prehistoric times. Classic sails are, however, poorly suited for modern economic conditions. This is because their efficiency depends on the weather and because large crews are required to handle them. Some designs try to overcome these issues. One example is the windmill ship which captures wind energy with a rotor that drives a conventional propeller. Another is the SkySails propulsion system. It is a large foil kite with an electronic control system which can be automatically set. The kites, having an area of approximately 320 square meters (3,400 sq ft), can be flown at altitudes of 100–300 meters (330–980 ft). Due to the stronger winds at these heights, they receive a higher thrust per unit area than conventional mast-mounted sails. A ship equipped with the SkySails could attain an increase in fuel efficiency of 10 to 35%. Despite a number of attempts, Flettner ships have not been successful. However, Jacques Cousteau made improvements in his design, the Turbosail. Unlike simple Flettner rotors, Turbosail is able to produce thrust in the direction of travel, regardless of wind direction. The first turbosail-equipped ship, Alcyone, reported a 1/3 fuel saving. The efficiency of the system has not, however, been subjected to adequate comparison. Only two turbosail-equipped vessels have undergone research
Fuel cell powered boats may benefit from the higher thermodynamic efficiency of fuel cells compared to internal combustion engines (40-60% vs 20-25%). However, fuel cells are costly. In 2009, the United States of America's Department of Energy estimated the cost of an 80-kW automotive fuel cell system in volume production (projected to 500,000 units per year) at US$61 per kilowatt. Solar panels have been also suggested for powering primary and secondary ship systems. Solar powered boats are usually limited to rivers and canals. In 2007, an experimental 14m catamaran, the 'Sun21' sailed the Atlantic from Seville to Miami, and from there to New York
Egyptian, Phoenician, Greek, and Roman cultures along with prior cultures and their contemporaries used sails as propulsion for commercial and military vessels. However, pleasure craft evolved along with practical craft. Even today some primitive vessels can outsail modern sailing yachts when running before the wind with their standard sails (no spinnakers etc.)
The first yachts
The term "yacht
" is a 17th-century English extraction from the Dutch word Jacht; however, royalty and aristocracy enjoyed traveling on the water from time immemorial, with the earliest documentation being in the Egyptian heyday. There is no documentation that these beneficiaries of the enjoyment were participants in the efforts.
The roots of modern yachting come from British royalty, commencing with Charles II, when Kings and Princes commissioned relatively small pleasure craft in which they competed.
Small commercial craft
In the time when water-based industries were dominated by sailing-craft, speed was as crucial to success as it is today, perhaps even more so. Getting fish to market or delivering other perishable goods swiftly could make or break a venture. Having a swifter hull or a superior rig could be the strategic advantage that would provide financial success.
Competition between owners of small commercial craft was the driving force in developing upwind sailing technology. Larger craft were less concerned with maneuverability within harbors or in coastal regions where the geography of the land was an impediment to downwind sailing.
Many of the advances in yachting technology came from the fishing industry and local commercial packets. Even pirates contributed to the advances, because small, fast, and highly maneuverable vessels proved successful.
The huge wealth accumulated by the commercial upper-class in the late 19th and early 20th century allowed commoners to enter the realm of yachting previously reserved for royalty and the peerage. Americans as well as Britons began to vie for international acclaim. The yacht America burst in on British egos and created a national rivalry, which has now grown to be the America's Cup.
Wealthy industrialists such as the Vanderbilts and the Liptons vied with royalty to finance a boom in yachting technology. As the learning curve flattened, less illustrious names were able to finance successful yachts as advance seemed to come from more random successes in design – fine tuning.
World War I dampened the growth in yachting, but the 1920s once again brought a heyday of activity and advancement. The production manufacturing capacity and technology created during the war years catapulted the developments in yachting. However the crash of the international economy at the close of the decade as quickly dampened the demand for large exotic yachts. In order to survive designers and producers had to diversify their efforts and offerings. Once again small commercial craft became the test-beds for technology and the bread-and-butter for the builders in the 1930s. One of the great design teams from this period, Sparkman & Stephens is still influential today.
World War II terminated most direct production of yachts, but the tremendous need for increasingly diverse small naval craft stimulated research and development and increased production capacity for the boating industry. Louisiana based Higgins came up with innovative landing craft, and along with Elco, manufactured the majority of PT Boats. Sparkman & Stephens designed the DUKW an amphibious version of the conventional six-wheel-drive Army truck. Of course the military had little need of sailboats.
Fiberglass and yachts
The late 1940s, following World War II, were a time of economic retrenchment, but as the US and international economies boomed in the 1950s the pent-up technology within the boating industry exploded with innovation and production. World War II was the catalyst for development of compact engine systems, mass production of plywood water craft, and advances in hydrodynamic design. Another outgrowth of war production was fiberglass; the first fiberglass boats were made in the 1930s but practical production did not begin until the 1950s and then more as a supplement to wood and plywood than as a structural component.
While the 1950s was a test bed for early fiberglass techniques, the early sixties was when the benefits became directly available to the average sailor, as the fiberglass industry began to mature from one-up to assembly lines and standardization. There was an explosion of entrepreneurial expression in the first half of the sixties, which leapfrogged year after year. Each season brought more options and larger boats to the common man, almost analogous to the rapid expansion of the personal computer in the 1990s. Soon a middle-class family could add a 30 foot sailboat to their Plymouth and hamburger budget.
Some of the prevalent brands in the 1960s were Cal, Coronado, Columbia, C&C, Morgan and Pearson; most of these were outgrowths of entrepreneurial venture. But even large companies such as AMF and Chrysler were making boats. Today's big manufacturers are led by people with their roots in 1960s venture.
However, by the late 1960s there was market saturation and entrepreneurs sold into conglomerates or otherwise merged their efforts. The mid-1970s saw an increase in interest in sailing as oil prices began to climb following the 1973 Oil Embargo; however, with petroleum as a major component for plastic resins manufacturing costs also increased. In early designs the solution to engineering problems was frequently: just add more fiberglass. The early boats were sturdy but heavy. Many of the vessels produced during this time frame are afloat today, and several models still enjoy sold sales demand and exhibit excellent sailing characteristics; the Islander 36 is an excellent example of a boat from this era.
With the increase in materials costs, engineering to a finer standard became critical for financial success. This was a double edged sword as boats became lighter, but in some cases they became weaker. Also some manufacturers turned to less expensive plastics and a form of hull decomposition known as blistering became prevalent.
The economic downturn of the early 1980s reduced demand for sailboats, while manufacturers increasingly competed with the used boat market. Since fiberglass doesn't rot or rust, twenty years of high production had left a huge inventory of boats, and in many areas the number of boats exceeded the marina space to house them.
The boats of the 1960s and 1970s were substantially extensions of classic hull designs which evolved in wood and were influenced by the early rules of racing. There was an emphasis on shorter waterlines at rest that would expand dramatically when the boat heeled (leaned) -- this had to do with the rules of racing, where the boat's handicap was not based on actual performance, but on design attributes.
Modifications of racing rules and changes in consumer demand have influenced recent boat designs. There is also a polarization, where racing boats are more distinct from cruising boats.
Current racing rules for the common sailor are known as PHRF (Performance Handicapped Racing Fleet) rules. The philosophy is to have a dynamic system of handicapping which looks to the performance of a boat model over time, but allows for adjustment to an individual boat based on options and/or modifications. What we consider long lean classic proportions of the boats of the early 1900s were at the time design exercises to manipulate the racing rules. Now our current boats tend to seek optimum performance as the prime criterion.
Boats tend to fall into the categories of (1) racer, (2) racer-cruiser, (3) cruiser-racer, and (4) cruiser; however, there is much subjectivity in the definitions and classifications. Cruising is sailing for the enjoyment of sailing and to reach destinations. Frequently cruisers spend much more time enjoying the amenities of their boats than the sailing aspects, so creature comfort is important. A large pure cruising boat would be likely to have solar panels, wind generated electricity, multiple heads (bathrooms), a complete galley (kitchen), comfortable cabins and even laundry facilities. Many cruiser designs are cutter rigged meaning they carry two headsails, and many have a second mast (mizzen), in the yawl or ketch configuration. Having more sails allows for having smaller individual sails; on a pure cruiser the boats do not change directions frequently, so manipulating multiple sails is not a factor.
Virtually all racing boats today are sloop rigged, which means that they carry one headsail and a mainsail, both from the same mast. Two very large sails mean more work to hoist and handle, but when changing direction, there is less work to be done and it can be done faster; however, sometimes with great effort using massive winch systems. The interiors of serious race boats are often stripped bare with the head being a bucket.
Most cruising boats are produced in large factories; most racing boats are produced in smaller lots by specialty shops or under contract with larger producers. Frequently the name of a race boat is that of the designer not the producer; in some cases multiple manufacturers have produced the same design either at the same or different times.
The majority of market share for production cruising boats is divided among Beneteau, Catalina Yachts, and Hunter Marine. Beneteau has a bit more emphasis on speed; Hunter focuses more on amenities; and Catalina falls in between. Catalina tends to have long running models of boats which evolve over time, but this allows for the development of "one design" fleets, where Beneteau and Hunter tend to change their designs frequently addressing the demands of the market. Both strategies have been successful for the staying power of these three brands.
There is also a strong demand for more specialized cruising boats with a wide range of producers. These boats offer features such as center cockpit, deck salon, pilot-house, cutter rigs, mizzen masts etc. The cabin detail and systems in Beneteau, Catalina and Hunter boats is comfortable but basic; more expensive boats offer a wide range of quality in the wood work, cabinetry, upholstery, and systems. There are also structural improvements beneath the surface and qualitative benefits in systems as the cost of the boat increases. A top-of-the-line cruiser could cost three times the price of a Beneteau, Catalina, or Morgan. The price may not be justified for bay cruising, but heavier shrouds, a thicker mast, and a stiffer hull could be priceless in a force 8 gale.
Kevlar and carbon fiber are among the materials for the new generation of hi-tech sailboat. Multihull boats are capable of 45 knots and monohull boats are exceeding 40 knots. Some of these hi-tech wonder boats cost as much as $10 million.
Strip-built is a method of boat building commonly used for canoes and kayaks, but also suitable for larger boats. The process involves securing narrow, flexible strips of wood edge-to-edge around temporary forms.
These are the most popular among homebuilders. Some professional builders also offered both kits and finished boats. The canoes are constructed by gluing together 1/4" x 3/4" strips of wood over a building jig consisting of station molds that define the shape of the hull. The strips may be square cut, or for a better fit, they are shaped with bead and cove router bits. Once the strips are glued together, the inside and outside are sanded fair, and a fiberglass and epoxy covering is applied to the canoe inside and out. The fiberglass covering is transparent, allowing the wood strips to be seen. The strips are usually cedar, though sometimes pine is also used. Walnut or other contrasting woods are sometimes used as accent strips.
The forms are cut as a series of cross-sections of the final design and set up along a "strong back" or other solid base. Stripping begins at the gunwale and finishes with "the football". The strips are edge-glued to each other, being held in place with nails, staples, or simply clamped to the forms. When the glue has dried, the nails/staples are removed and the rough hull is sanded smooth. It is then covered with a resin/epoxy impregnated overlay of fiberglass cloth, which is sanded and finished before removing the hull from the forms. The inside is then smoothed and similarly reinforced before seats, thwarts, and gunwales, are added to complete the boat.
This process is similarly suited to building kayaks. The strips are stapled onto a number of chipboard forms, the structures is sanded and fibreglassed, then the forms are removed and the hull is attached.
In the 1950s, this process for building canoes was adapted from ship/boat building techniques, and refined by a group of Minnesota canoe racers; primarily Eugene Jensen, Irwin C.(Buzzy) Peterson, and Karl Ketter.
Stitch and glue is a simple boat building method which uses plywood panels stitched together, usually with copper wire, and glued together with epoxy. This type of construction eliminates the need for frames or ribs. Plywood panels are cut to shape and stitched together to form an accurate hull shape without the need for forms or special tools. This technique is also called "tack and tape", or "stitch and tape". Seams are reinforced with fiberglass tape and thickened epoxy
The stitch and glue method was developed by woodwork teacher Ken Littledyke for the manufacture of canoes, later sold as the 'Kayel' in plan and kit form, using plywood panels joined by fiberglass tape and resin. The technique was then popularised by the first TV DIY expert, Barry Bucknell, in about 1964. The method was adopted, substituting copper wire ties rather than fishing line as in the early Littledyke examples, for the construction of the Mirror Dinghy. The Mirror is so named because the design was sponsored by The Daily Mirror newspaper, a fact reflected by the historically red sails. The Daily Mirror apparently wanted to bring cheap sailing to the masses. As such, unlike other construction techniques of the day, which required specialist skills and tools, Stitch and Glue was supposed to put boat-building within the reach of the average public.
Stitch and glue is similar to a traditional form of boatbuilding from northern Europe, particularly Lapland, called sewn boats. It is not known if Littledyke's development of the stitch and glue methods was influenced by the sewn boat technique.
The technique consists of stitching together plywood panels with some sort of wire or other suitable device, such as cable ties or duct tape. Copper wire is popular because the wires can be twisted tighter or looser to precisely adjust fit, and because it is easy to sand after gluing, and it is suitable in a marine environment if left in place. To join, the cut panels are drilled with small holes along the joining edges and stitched. Once together, the join is glued, usually with thickened epoxy and fiberglass on the inside of the hull.
On the outside of the hull, the wire is snipped and the joints filled and sanded over. The outside of the joint, or entire hull, may be fiberglassed and glued as well, providing additional strength. The combination of fiberglass tape and epoxy glue results in a composite material providing an extremely strong joint.
An alternative is to use dabs of thickened epoxy in between the "stitching" to join the panels, and after it has cured, completely remove the copper wires instead of just snipping them off on the outside. With the wires removed, you can go back and apply a fillet of thickened epoxy over the entire length of the join.
True stitch and glue designs generally have few bulkheads, relying instead on the geometry of the panels to provide shape, and forming a monocoque or semi-monocoque structure.
Stitch and glue has become one of the dominant techniques in amateur boatbuilding. While the use of relatively few plywood panels (which minimizes the joints and makes the construction easier and faster) limits the shapes possible, the simplicity and low cost of the stitch and glue technique makes it the method of choice among most amateur boatbuilders. Simple software CAD packages are available for designing stitch and glue boats, and there are many Internet bulletin boards, newsgroups, and mailing lists dedicated to the subject of stitch and glue boats and various popular stitch and glue designs. Stitch and glue is not inherently limited to small designs though, as demonstrated by the boats made by Sam Devlin, who has applied the technique to making boats as long as 45 feet.
The "Instant Boats
" developed by Phil Bolger use simplified framing and stitch-and-glue style plywood sheet joining and bulkhead gluing. Step-by-step building books about the boats and plans for many were sold by Harold Payson of Thomaston, Maine. They range from very small dinghies to power and sailboats 25 to 30 feet long. They are not necessarily designed for light weight, but like the original Mirror Dinghy, for simple construction. The plans predate CAD panel development software so the shapes are extremely simple in some cases.
he one sheet boat, or OSB, is an outgrowth of the stitch and glue technique. The OSB is a boat that can be built using a single sheet of 4 foot by 8 foot plywood (1.22 m × 2.44 m). Some additional wood is often used, for supports, chines, or as a transom, though some can be built entirely with the sheet of plywood. OSBs tend to be very small, since the displacement is limited to a theoretical maximum of about 1500 lb (680 kg), based on the largest hemispherical shape that could be formed with the same surface area as the sheet of plywood. Though forming a hemisphere is possible (see geodesic dome), it is only practical for one person, since most designs have a maximum displacements of under 1000 lb (450 kg).
is the mechanism or system used to generate thrust to move a ship or boat across water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of a motor or engine turning a propeller, or less frequently, in jet drives, an impeller. Marine engineering is the discipline concerned with the design of marine propulsion systems.
Steam engines were the first mechanical engines used in marine propulsion, but have mostly been replaced by two-stroke or four-stroke diesel engines, outboard motors, and gas turbine engines on faster ships. Nuclear reactors producing steam are used to propel warships and icebreakers, and there have been attempts to utilize them to power commercial vessels. Electric motors have been used on submarines and electric boats and have been proposed for energy-efficient propulsion. Recent development in liquified natural gas (LNG) fueled engines are gaining recognition for their low emissions and cost advantages.
Until the application of the coal-fired steam engine to ships in the early 19th century, oars or the wind were used to assist watercraft propulsion. Merchant ships predominantly used sail, but during periods when naval warfare depended on ships closing to ram or to fight hand-to-hand, galley were preferred for their manoeuvrability and speed. The Greek navies that fought in the Peloponnesian War used triremes, as did the Romans at the Battle of Actium. The development of naval gunnery from the 16th century onward meant that manoeuvrability took second place to broadside weight; this led to the dominance of the sail-powered warship over the following three centuries.
In modern times, human propulsion is found mainly on small boats or as auxiliary propulsion on sailboats. Human propulsion includes the push pole, rowing, and pedals.
Propulsion by sail generally consists of a sail hoisted on an erect mast, supported by stays, and controlled by lines made of rope. Sails were the dominant form of commercial propulsion until the late nineteenth century, and continued to be used well into the twentieth century on routes where wind was assured and coal was not available, such as in the South American nitrate trade. Sails are now generally used for recreation and racing, although experimental sail systems, such as the kites/royals, turbosails, rotorsails, wingsails, windmills and SkySails's own kite buoy-system have been used on larger modern vessels for fuel savings.
The development of piston-engined steamships was a complex process. Early steamships were fueled by wood, later ones by coal or fuel oil. Early ships used stern or side paddle wheels, while later ones used screw propellers.
The first commercial success accrued to Robert Fulton's North River Steamboat (often called Clermont) in the US in 1807, followed in Europe by the 45-foot Comet of 1812. Steam propulsion progressed considerably over the rest of the 19th century. Notable developments included the steam surface condenser, which eliminated the use of sea water in the ship's boilers. This permitted higher steam pressures, and thus the use of higher efficiency multiple expansion (compound) engines. As the means of transmitting the engine's power, paddle wheels gave way to more efficient screw propellers.
The development of piston-engined steamships was a complex process. Early steamships were fueled by wood, later ones by coal or fuel oil. Early ships used stern or side paddle wheels, while later ones used screw propellers.
The first commercial success accrued to Robert Fulton's North River Steamboat (often called Clermont) in the US in 1807, followed in Europe by the 45-foot Comet of 1812. Steam propulsion progressed considerably over the rest of the 19th century. Notable developments included the steam surface condenser, which eliminated the use of sea water in the ship's boilers. This permitted higher steam pressures, and thus the use of higher efficiency multiple expansion (compound) engines. As the means of transmitting the engine's power, paddle wheels gave way to more efficient screw propellers.
Steam turbines were fueled by coal or, later, fuel oil or nuclear power. The marine steam turbine developed by Sir Charles Algernon Parsons raised the power-to-weight ratio. He achieved publicity by demonstrating it unofficially in the 100-foot Turbinia at the Spithead Naval Review in 1897. This facilitated a generation of high-speed liners in the first half of the 20th century, and rendered the reciprocating steam engine obsolete; first in warships, and later in merchant vessels.
In the early 20th century, heavy fuel oil came into more general use and began to replace coal as the fuel of choice in steamships. Its great advantages were convenience, reduced manpower by removal of the need for trimmers and stokers, and reduced space needed for fuel bunkers.
In the second half of the 20th century, rising fuel costs almost led to the demise of the steam turbine. Most new ships since around 1960 have been built with diesel engines. The last major passenger ship built with steam turbines was the Fairsky, launched in 1984. Similarly, many steam ships were re-engined to improve fuel efficiency. One high profile example was the 1968 built Queen Elizabeth 2 which had her steam turbines replaced with a diesel-electric propulsion plant in 1986.
Most new-build ships with steam turbines are specialist vessels such as nuclear-powered vessels, and certain merchant vessels (notably Liquefied Natural Gas (LNG) and coal carriers) where the cargo can be used as bunker fuel.
New LNG carriers (a high growth area of shipping) continue to be built with steam turbines. The natural gas is stored in a liquid state in cryogenic vessels aboard these ships, and a small amount of 'boil off' gas is needed to maintain the pressure and temperature inside the vessels within operating limits. The 'boil off' gas provides the fuel for the ship's boilers, which provide steam for the turbines, the simplest way to deal with the gas. Technology to operate internal combustion engines (modified marine two-stroke diesel engines) on this gas has improved, however, so such engines are starting to appear in LNG carriers; with their greater thermal efficiency, less gas is burnt. Developments have also been made in the process of re-liquefying 'boil off' gas, letting it be returned to the cryogenic tanks. The financial returns on LNG are potentially greater than the cost of the marine-grade fuel oil burnt in conventional diesel engines, so the re-liquefaction process is starting to be used on diesel engine propelled LNG carriers. Another factor driving the change from turbines to diesel engines for LNG carriers is the shortage of steam turbine qualified seagoing engineers. With the lack of turbine powered ships in other shipping sectors, and the rapid rise in size of the worldwide LNG fleet, not enough have been trained to meet the demand. It may be that the days are numbered for marine steam turbine propulsion systems, even though all but sixteen of the orders for new LNG carriers at the end of 2004 were for steam turbine
In these vessels
, the nuclear reactor heats water to create steam to drive the turbines. Due to low prices of diesel oil, nuclear propulsion is rare except in some Navy and specialist vessels such as icebreakers. In large aircraft carriers, the space formerly used for ship's bunkerage could be used instead to bunker aviation fuel. In submarines, the ability to run submerged at high speed and in relative quiet for long periods holds obvious advantages. A few cruisers have also employed nuclear power; as of 2006, the only ones remaining in service are the Russian Kirov class. An example of a non-military ship with nuclear marine propulsion is the Arktika class icebreaker with 75,000 shaft horsepower (55,930 kW). Commercial experiments such as the NS Savannah have so far proved uneconomical compared with conventional propulsion.
In recent times, there is some renewed interest in commercial nuclear shipping. Nuclear-powered cargo ships could lower costs associated with carbon dioxide emissions and travel at higher cruise speeds than conventional diesel powered vessels.
Most modern ships use a reciprocating diesel engine as their prime mover, due to their operating simplicity, robustness and fuel economy compared to most other prime mover mechanisms. The rotating crankshaft can be directly coupled to the propeller with slow speed engines, via a reduction gearbox for medium and high speed engines, or via an alternator and electric motor in diesel-electric vessels. The rotation of the crankshaft is connected to the camshaft or a hydraulic pump on an intelligent diesel.
The reciprocating marine diesel engine first came into use in 1903 when the diesel electric rivertanker Vandal was put into service by Branobel. Diesel engines soon offered greater efficiency than the steam turbine, but for many years had an inferior power-to-space ratio. The advent of turbocharging however hastened their adoption, by permitting greater power densities.
Diesel engines today are broadly classified according to
Their operating cycle: two-stroke engine or four-stroke engine
Their construction: crosshead, trunk, or opposed piston
Slow speed: any engine with a maximum operating speed up to 300 revolutions per minute (rpm), although most large two-stroke slow speed diesel engines operate below 120 rpm. Some very long stroke engines have a maximum speed of around 80 rpm. The largest, most powerful engines in the world are slow speed, two stroke, crosshead diesels.
Medium speed: any engine with a maximum operating speed in the range 300-900 rpm. Many modern four-stroke medium speed diesel engines have a maximum operating speed of around 500 rpm.
High speed: any engine with a maximum operating speed above 900 rpm.
Most modern larger merchant ships use either slow speed, two stroke, crosshead engines, or medium speed, four stroke, trunk engines. Some smaller vessels may use high speed diesel engines.
The size of the different types of engines is an important factor in selecting what will be installed in a new ship. Slow speed two-stroke engines are much taller, but the footprint required is smaller than that needed for equivalently rated four-stroke medium speed diesel engines. As space above the waterline is at a premium in passenger ships and ferries (especially ones with a car deck), these ships tend to use multiple medium speed engines resulting in a longer, lower engine room than that needed for two-stroke diesel engines. Multiple engine installations also give redundancy in the event of mechanical failure of one or more engines, and the potential for greater efficiency over a wider range of operating conditions.
As modern ships' propellers are at their most efficient at the operating speed of most slow speed diesel engines, ships with these engines do not generally need gearboxes. Usually such propulsion systems consist of either one or two propeller shafts each with its own direct drive engine. Ships propelled by medium or high speed diesel engines may have one or two (sometimes more) propellers, commonly with one or more engines driving each propeller shaft through a gearbox. Where more than one engine is geared to a single shaft, each engine will most likely drive through a clutch, allowing engines not being used to be disconnected from the gearbox while others keep running. This arrangement lets maintenance be carried out while under way, even far from port.
Dual fuel engines are fueled by either marine grade diesel, heavy fuel oil, or liquefied natural gas (LNG). Having multiple fuel options will allow vessels to transit without relying on one type of fuel. Studies show that LNG is the most efficient of fuels although limited access to LNG fueling stations limits the production of such engines. Vessels providing services in the LNG industry have been retrofitted with dual-fuel engines and have been proved to be extremely effective. Benefits of dual-fuel engines include fuel and operational flexibility, high efficiency, low emissions, and operational cost advantages. Liquefied natural gas engines offer the marine transportation industry with an environmentally friendly alternative to provide power to vessels. In 2010 STX Finland and Viking Line signed an agreement to begin construction on what would be the largest environmentally friendly cruise ferry. Construction of NB 1376 will be completed in 2013. According to Viking Line, vessel NB 1376 will primarily be fueled by liquefied natural gas. The cruise ferry will have an emission reduction comparison to diesel-fuelled engines of approximately 90%. Vessel NB 1376 nitrogen oxide emissions will be almost zero and sulphur oxide emissions will be at least 80% below the International Maritime Organization's (IMO) standards. Company profits from tax cuts and operational cost advantages has led to the gradual growth of LNG fuel use in engines.
Many warships built since the 1960s have used gas turbines for propulsion, as have a few passenger ships, like the jetfoil. Gas turbines are commonly used in combination with other types of engine. Most recently, the Queen Mary 2 has had gas turbines installed in addition to diesel engines. Because of their poor thermal efficiency at low power (cruising) output, it is common for ships using them to have diesel engines for cruising, with gas turbines reserved for when higher speeds are needed however, in the case of passenger ships the main reason for installing gas turbines has been to allow a reduction of emissions in sensitive environmental areas or while in port. Some warships, and a few modern cruise ships have also used steam turbines to improve the efficiency of their gas turbines in a combined cycle, where waste heat from a gas turbine exhaust is utilized to boil water and create steam for driving a steam turbine. In such combined cycles, thermal efficiency can be the same or slightly greater than that of diesel engines alone; however, the grade of fuel needed for these gas turbines is far more costly than that needed for the diesel engines, so the running costs are still higher.
Marine propellers are also known as "screws". There are many variations of marine screw systems, including twin, contra-rotating, controllable-pitch, and nozzle-style screws. While smaller vessels tend to have a single screw, even very large ships such as tankers, container ships and bulk carriers may have single screws for reasons of fuel efficiency. Other vessels may have twin, triple or quadruple screws. Power is transmitted from the engine to the screw by way of a propeller shaft, which may or may not be connected to a gearbox.
The paddle wheel is a large wheel, generally built of a steel framework, upon the outer edge of which are fitted numerous paddle blades (called floats or buckets). The bottom quarter or so of the wheel travels underwater. Rotation of the paddle wheel produces thrust, forward or backward as required. More advanced paddle wheel designs have featured feathering methods that keep each paddle blade oriented closer to vertical while it is in the water; this increases efficiency. The upper part of a paddle wheel is normally enclosed in a paddlebox to minimise splashing.
Paddle wheels have been superseded by screws, which are a much more efficient form of propulsion. Nevertheless, paddle wheels have two advantages over screws, making them suitable for vessels in shallow rivers and constrained waters: first, they are less likely to be clogged by obstacles and debris; and secondly, when contra-rotating, they allow the vessel to spin around its own vertical axis. Some vessels had a single screw in addition to two paddle wheels, to gain the advantages of both types of propulsion.
The purpose of sails is to use wind energy to propel the vessel, sled, board, vehicle or rotor.
An early uncommon means of boat propulsion was the water caterpillar. This moved a series of paddles on chains along the bottom of the boat to propel it over the water and preceded the development of tracked vehicles. The first water caterpillar was developed by Desblancs in 1782 and propelled by a steam engine. In the United States the first water caterpillar was patented in 1839 by William Leavenworth of New York.
Underwater gliders convert buoyancy to thrust, using wings, or more recently hull shape (SeaExplorer Glider). Buoyancy is made alternatively negative and positive, generating tooth-saw profiles.
A slipway, also known as boat ramp or launch, is a ramp on the shore by which ships or boats can be moved to and from the water. They are used for building and repairing ships and boats. They are also used for launching and retrieving small boats on trailers towed by automobiles and flying boats on their undercarriage.
The nautical term ways is an alternative name for slipway. A ship undergoing construction in a shipyard is said to be on the ways. If a ship is scrapped there, she is said to be broken up in the ways.
As the word "slip" implies, the ships or boats are moved over the ramp, by way of crane or fork lift, prior to the move the vessel's hull is coated with grease, which then allows the ship or boat to "slip" off of the ramp and progress safely into the water. Slipways are used to launch (newly built) large ships, but can only dry-dock or repair smaller ships. Pulling large ships against the greased ramp would require too much force. For dry-docking large ships, one must use carriages supported by wheels or by roller-pallets. These types of dry-docking installations are called "marine railways". Nevertheless the words "slip" and "slipway" are also used for all dry-docking installations that use a ramp.
In its simplest form, a slipway is a plain ramp, typically made of concrete, steel, stone or even wood. The height of the tide can limit the usability of a slip: unless the ramp continues well below the low water level it may not be usable at low tide. Normally there is a flat paved area on the landward end.
When used for building and repairing boats or small ships (i.e. ships of no more than about 300 tons), the vessel is moved on a wheeled carriage, which is run down the ramp until the vessel can float on or off the carriage. Such slipways are used for repair as well as for putting newly built vessels in the water.
When used for launching and retrieving small boats, the trailer is placed in the water. The boat may be either floated on and off the trailer or pulled off. When recovering the boat from the water, it is winched back up the trailer.Whaling ships are usually equipped with a slipway at the back, to assist in hauling harpooned whales onto the main deck, where they are usually flensed.
To achieve a safe launch of some types of land-based lifeboats in bad weather and difficult sea conditions, the lifeboat and slipway are designed so that the lifeboat slides down a relatively steep steel slip under gravity. It is winched back up afterward.
For large ships, slipways are only used in construction of the vessel. Normally they are arranged perpendicular to the shore line (or as nearly so as the water and maximum length of vessel allows) and the ship is built with its stern facing the water. Modern slipways take the form of a reinforced concrete mat of sufficient strength to support the vessel, with two "barricades" that extend to well below the water level taking into account tidal variations. The barricades support the two launch ways. The vessel is built upon temporary cribbing that is arranged to give access to the hull's outer bottom, and to allow the launchways to be erected under the complete hull. When it is time to prepare for launching a pair of standing ways are erected under the hull and out onto the barricades. The surface of these ways are greased. (Tallow and whale oil were used as grease in sailing ship days.) A pair of sliding ways is placed on top, under the hull, and a launch cradle with bow and stern poppets is erected on these sliding ways. The weight of the hull is then transferred from the build cribbing onto the launch cradle. Provision is made to hold the vessel in place and then release it at the appropriate moment in the launching ceremony, these are either a weak link designed to be cut at a signal or a mechanical trigger controlled by a switch from the ceremonial platform.
The process of transferring the vessel to the water is known as launching and is normally a ceremonial and celebratory occasion. It is the point where the vessel is formally named. At this point the hull is complete and the propellers and associated shafting are in place, but dependent on the depth of water, stability and weight the engines might have not been fitted or the superstructure may not be completed.
On launching, the vessel slides backwards down the slipway on the ways until it floats by itself.
Some slipways are built so that the vessel is side on to the water and is launched sideways. This is done where the limitations of the water channel would not allow lengthwise launching, but occupies a much greater length of shore. The Great Eastern built by Brunel was built this way as were many landing craft during World War II. This method requires many more sets of ways to support the weight of the ship.
In both cases heavy chains are attached to the ship and the drag effect is used to slow the vessel once afloat until tugboats can move the hull to a jetty for fitting out.
The practice of building on a slipway is dying out with the very large vessels introduced from about 1970. Part of the reason is the space requirement for slowing and maneuvering the vessel immediately after it has left the slipway, but the sheer size of the vessel causes design problems, since the hull is basically supported only at its end points during the launch process and this imposes stresses not met during normal operation.
(also commonly dry dock) is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. Drydocks are used for the construction, maintenance, and repair of ships, boats, and other watercraft.
According to the ancient Greek author Athenaeus of Naucratis (V 204c-d), the drydock was invented in Ptolemaic Egypt, some time after the death of Ptolemy IV Philopator
But after that (the reign of Ptolemy IV Philopator) a Phoenician devised a new method of launching it (a ship), having dug a deep trench under it, equal to the ship itself in length, which he dug close to the harbour. And in the trench he built props of solid stone five cubits deep, and across them he laid beams crosswise, running the whole width of the trench, at four cubits' distance from one another; and then making a channel from the sea he filled all the space which he had excavated with water, out of which he easily brought the ship by the aid of whatever men happened to be at hand; then closing the entrance which had been originally made, he drained the water off again by means of engines (organois); and when this had been done the vessel rested securely on the before-mentioned cross-beams.
Since Athenaeus recorded the event 400 years later (around 200 AD), there is sufficient reason to believe that drydocks had been known throughout classical antiquity. The Roman shipyard at Narni, Italy, which is still being studied, may have served as a dry dock.
The use of drydocks
in China goes at least as far back the 10th century A.D. In 1088, Song Dynasty scientist and statesman Shen Kuo (1031–1095) wrote in his Dream Pool Essays:
At the beginning of the dynasty (c. +965) the two Che provinces (now Chekiang and southern Chiangsu) presented (to the throne) two dragon ships each more than 200 ft. in length. The upper works included several decks with palatial cabins and saloons, containing thrones and couches all ready for imperial tours of inspection. After many years, their hulls decayed and needed repairs, but the work was impossible as long as they were afloat. So in the Hsi-Ning reign period (+1068 to +1077) a palace official Huang Huai-Hsin suggested a plan. A large basin was excavated at the north end of the Chin-ming Lake capable of containing the dragon ships, and in it heavy crosswise beams were laid down upon a foundation of pillars. Then (a breach was made) so that the basin quickly filled with water, after which the ships were towed in above the beams. The (breach now being closed) the water was pumped out by wheels so that the ships rested quite in the air. When the repairs were complete, the water was let in again, so that the ships were afloat once more (and could leave the dock). Finally the beams and pillars were taken away, and the whole basin covered over with a great roof so as to form a hangar in which the ships could be protected from the elements and avoid the damage caused by undue exposure.
The first early modern European and oldest surviving drydock still in use was commissioned by Henry VII of England at HMNB Portsmouth in 1495 (see Tudor navy). This drydock currently holds the world's oldest commissioned warship, HMS Victory.
Possibly the earliest description of a floating dock comes from a small Italian book printed in Venice in 1560, called Descrittione dell'artifitiosa machina. In the booklet, an unknown author asks for the privilege of using a new method for the salvaging of a grounded ship and then proceeds to describe and illustrate his approach. The included woodcut shows a ship flanked by two large floating trestles, forming a roof above the vessel. The ship is pulled in an upright position by a number of ropes attached to the superstructure.
The Alfredo da Silva Dry Dock, of the Lisnave Dockyards in Almada, Portugal, was the largest in the world until 2000, when it was closed after the moving of Lisnave operations to Setúbal.
Currently, Harland and Wolff Heavy Industries in Belfast, Northern Ireland, is the site of the largest drydock in the world. The massive cranes are named after the Biblical figures Samson and Goliath. Goliath stands 96m tall, while Samson is taller at 106m.
12 at Newport News Shipbuilding is the largest drydock in the Western Hemisphere. The Saint-Nazaire's Chantiers de l'Atlantique owns one of the biggest in the world: 1,200 by 60 metres (3,940 ft × 200 ft). The largest graving dock of the Mediterranean
as of 2009 is at the Hellenic Shipyards S.A. (HSY S.A., Athens, Greece). The by far largest roofed dry dock is at the German Meyer Werft Shipyard in Papenburg, Germany, it is 504m long, 125m wide and stands 75m tall.
The classic form of drydock, properly known as graving dock, is a narrow basin, usually made of earthen berms and concrete, closed by gates or by a caisson, into which a vessel may be floated and the water pumped out, leaving the vessel supported on blocks. The keel blocks as well as the bilge block are placed on the floor of the dock in accordance with the "docking plan" of the ship. More routine use of drydocks is for the cleaning (removal of barnacles and rust) and re-painting of ship's hulls.
Some fine-tuning of the ship's position can be done by divers while there is still some water left to manoeuvre it about. It is extremely important that supporting blocks conform to the structural members so that the ship is not damaged when its weight is supported by the blocks. Some anti-submarine warfare warships have protruding sonar domes, requiring that the hull of the ship be supported several metres from the bottom of the drydock.
Once the remainder of the water is pumped out, the ship can be freely inspected or serviced. When work on the ship is finished, water is allowed to re-enter the dry dock and the ship is carefully refloated.
Modern graving docks are box-shaped, to accommodate the newer, boxier ship designs, whereas old drydocks are often shaped like the ships that are planned to be docked there. This shaping was advantageous because such a dock was easier to build, it was easier to side-support the ships, and less water had to be pumped away.
Drydocks used for building Navy vessels may occasionally be built with a roof. This is done to prevent spy satellites from taking pictures of the drydock and any ships or submarines that may be in it. During World War II, fortified drydocks were used by the Germans to protect their submarines from Allied air raids (see submarine pen); however, their effectiveness in that role diminished towards the end of the war as bombs became available that could penetrate them. Today, covered drydocks are usually used only when servicing or repairing a fleet ballistic missile submarine. Another advantage of covered drydocks is that work can take place independently of the weather; this is frequently used by modern shipyards for construction especially of complex, high-value vessels like cruise ships where delays would incur a high cost.
A floating drydock is a type of pontoon for dry docking ships, possessing floodable buoyancy chambers and a "U"-shaped cross-section. The walls are used to give the drydock stability when the floor or deck is below the surface of the water. When valves are opened, the chambers fill with water, causing the drydock to float lower in the water. The deck becomes submerged and this allows a ship to be moved into position inside. When the water is pumped out of the chambers, the drydock rises and the ship is lifted out of the water on the rising deck, allowing work to proceed on the ship's hull.
A typical floating drydock involves multiple rectangular sections. These sections can be combined to handle ships of various lengths, and the sections themselves can come in different dimensions. Each section contains its own equipment for emptying the ballast and to provide the required services, and the addition of a bow section can facilitate the towing of the drydock once assembled. For smaller boats, one-piece floating drydocks can be constructed, potentially coming with their own bow and steering mechanism.
operate floating drydocks
as one method for hauling or docking vessels. The advantage of floating drydocks is they can be moved to wherever they are needed and can also be sold second-hand. During World War II, the U.S. Navy used such (floating) drydocks extensively to provide maintenance in remote locations. One of these, the 850-foot AFDB-3, an Advance Base Sectional Dock, saw action in Guam, was mothballed near Norfolk, Virginia, and was eventually towed to Portland, Maine, to become part of Bath Iron Works' repair facilities.
The "Hughes Mining Barge", or HMB-1, is a covered, floating drydock that is also submersible to support the secret transfer of a mechanical lifting device underneath the Glomar Explorer ship, as well as the development of the Sea Shadow stealth ship.
Alternative drydock systems
Apart from graving docks and floating drydocks, ships can also be drydocked and launched by:
Marine railway — For repair of larger ships up to about 3000 tons ship weight
Shiplift — For repair as well as for newbuilding. From 800 to 25000 ton shipweight
Slipway, patent slip — For repair of smaller boats and the newbuilding launch of larger vessels
Naval architecture also known as Naval engineering is an engineering discipline dealing with the design, construction, maintenance and operation of marine vessels and structures. Naval architecture involves basic and applied research, design, development, design evaluation and calculations during all stages of the life of a marine vehicle. Preliminary design of the vessel, its detailed design, construction, trials, operation and maintenance, launching and dry-docking are the main activities involved. Ship design calculations are also required for ships being modified (by means of conversion, rebuilding, modernization, or repair). Naval architecture also involves formulation of safety regulations and damage control rules and the approval and certification of ship designs to meet statutory and non-statutory requirements.
The word "vessel" includes every description of watercraft, including non-displacement craft, WIG craft and seaplanes, used or capable of being used as a means of transportation on water. The principal elements of naval architecture are:
Hydrostatics concerns the conditions to which the vessel is subjected to while at rest in water and its ability to remain afloat. This involves computing buoyancy, (displacement) and other hydrostatic properties. Trim – The measure of the longitudinal inclination of the vessel. Stability – The ability of a vessel to restore itself to an upright position after being inclined by wind, sea, or loading conditions.
Hydrodynamics concerns the flow of water around the ship's hull, bow, stern and over bodies such as propeller blades or rudder, or through thruster tunnels. Resistance – resistance towards motion in water primarily caused due to flow of water around the hull. Powering calculation is done based on this. Propulsion – to move the vessel through water using propellers, thrusters, water jets, sails etc. Engine types are mainly internal combustion. Some vessels are electrically powered using nuclear or solar energy. Ship motions – involves motions of the vessel in seaway and its responses in waves and wind. Controllability (maneuvering) – involves controlling and maintaining position and direction of the vessel
Structures involves selection of material of construction, structural analysis of global and local strength of the vessel, vibration of the structural components and structural responses of the vessel during motions in seaway.
Arrangements involves concept design, layout and access, fire protection, allocation of spaces, ergonomics and capacity.
Construction depends on the material used. When steel or aluminium is used this involves welding of the plates and profiles after rolling, marking, cutting and bending as per the structural design drawings or models, followed by erection and launching. Other joining techniques are used for other materials like fibre reinforced plastic and glass-reinforced plastic.
Traditionally, naval architecture has been more craft than science. The suitability of a vessel's shape was judged by looking at a half-model of a vessel or a prototype. Ungainly shapes or abrupt transitions were frowned on as being flawed. This included rigging, deck arrangements, and even fixtures. Subjective descriptors such as ungainly, full, and fine were used as a substitute for the more precise terms used today. A vessel was, and still is described as having a 'fair' shape. The term 'fair' is meant to denote not only a smooth transition from fore to aft but also a shape that was 'right.' Determining what is 'right' in a particular situation in the absence of definitive supporting analysis encompasses the art of naval architecture to this day.
Modern low-cost digital computers and dedicated software, combined with extensive research to correlate full-scale, towing tank and computational data, have enabled naval architects to more accurately predict the performance of a marine vehicle. These tools are used for static stability (intact and damaged), dynamic stability, resistance, powering, hull development, structural analysis, green water modelling, and slamming analysis. Data is regularly shared in international conferences sponsored by RINA, Society of Naval Architects and Marine Engineers (SNAME) and others. Computational Fluid Dynamics is being applied to predict the response of a floating body in a random sea.
Due to the complexity associated with operating in a marine environment, naval architecture is a co-operative effort between groups of technically skilled individuals who are specialists in particular fields, often coordinated by a lead naval architect. This inherent complexity also means that the analytical tools available are much less evolved than those for designing aircraft, cars and even spacecraft. This is due primarily to the paucity of data on the environment the marine vehicle is required to work in and the complexity of the interaction of waves and wind on a marine structure.
A naval architect is an engineer who is responsible for the design, construction, and/or repair of ships, boats, other marine vessels, and offshore structures, both commercial and military, including:
Merchant ships – oil tankers, gas tankers, cargo ships, bulk carriers, container ships
Passenger/vehicle ferries, cruise ships
Warships – frigates, destroyers, aircraft carriers, amphibious ships
Submarines and underwater vehicles
High speed craft – hovercraft, multi-hull ships, hydrofoil craft
Workboats – barges, fishing boats, anchor handling tug supply vessels, platform supply vessels, tug boats, pilot vessels, rescue craft
Yachts, power boats, and other recreational watercraft
Offshore platforms and subsea developments
Some of these vessels are amongst the largest (such as supertankers), most complex (such as Aircraft carriers), and highly valued movable structures produced by mankind. They are typically the most efficient method of transporting the world's raw materials and products. Modern engineering on this scale is essentially a team activity conducted by specialists in their respective fields and disciplines. Naval architects integrate these activities. This demanding leadership role requires managerial qualities and the ability to bring together the often-conflicting demands of the various design constraints to produce a product which is fit for the purpose.
In addition to this leadership role, a naval architect also has a specialist function in ensuring that a safe, economic, environmentally sound and seaworthy design is produced. To undertake all these tasks, a naval architect must have an understanding of many branches of engineering and must be in the forefront of high technology areas. He or she must be able to effectively utilize the services provided by scientists, lawyers, accountants, and business people of many kinds.
Naval architects typically work for shipyards, ship owners, design firms and consultancies, equipment manufacturers, Classification societies, regulatory bodies (Admiralty law), navies, and governments.
Offshore construction is the installation of structures and facilities in a marine environment, usually for the production and transmission of electricity, oil, gas and other resources.
Construction and pre-commissioning is typically performed as much as possible onshore. To optimize the costs and risks of installing large offshore platforms, different construction strategies have been developed.
One strategy is to fully construct the offshore facility onshore, and tow the installation to site floating on its own buoyancy. Bottom founded structure are lowered to the seabed by de-ballasting (see for instance Condeep or Cranefree), whilst floating structures are held in position with substantial mooring systems.
The size of offshore lifts can be reduced by making the construction modular, with each module being constructed onshore and then lifted using a crane vessel into place onto the platform. A number of very large crane vessels were built in the 1970s which allow very large single modules weighing up to 14,000 tonnes to be fabricated and then lifted into place.
Specialist floating hotel vessels known as flotels are used to accommodate workers during the construction and hook-up phases. This is a high cost activity due to the limited space and access to materials.
Oil platforms are key fixed installations from which drilling and production activity is carried out. Drilling rigs are either floating vessels for deeper water or jack-up designs which are a barge with liftable legs. Both of these types of vessel are constructed in marine yards but are often involved during the construction phase to pre-drill some production wells. Other key factors in offshore construction are the weather window which defines periods of relatively light weather during which continuous construction or other offshore activity can take place. Safety is another key construction parameter, the main hazard obviously being a fall into the sea from which speedy recovery in cold waters is essential.
The main types of vessels used for pipe laying are the "Derrick Barge (DB)", the "Pipelay Barge (LB)" and the "Derrick/Lay barge (DLB)" combination. Diving bells in offshore construction are mainly used in water depths greater than 120 feet (40 m), less than that, the divers use a metal basket driven from an "A" frame from the deck. The basket is lowered to the water level, then the divers enter the water from it to a maximum of 120 feet (40 m). Bells can go to 1,500 feet (460 m), but are normally used at 400 to 800 feet (120 to 240 m).
Offshore construction includes foundations engineering, structural design, construction, and/or repair of offshore structures, both commercial and military, including:Subsea oil and gas developments
Offshore platforms – fixed platforms, semi-submersibles, spars, tension leg platforms (TLPs), floating production storage and offloading (FPSOs), etc.
Floating oil and gas platforms – semi-submersibles, spars, TLPs, FPSOs, etc.
or sailing boat
is a boat propelled partly or entirely by sails. The generic term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in the size are not strictly defined and what constitutes a sailing ship, sailboat, or a smaller vessel (such as a sailboard) varies by region and maritime culture.
Further information: Sailplan
See also: List of sailing boat types
At present, a great number of sailboat-types may be distinguished. Apart from size, sailboats may be distinguished by a hull configuration (monohull, catamaran, trimaran), keel type (full, fin, wing, centerboard etc.), purpose (sport, racing, cruising), number and configuration of masts, and sail plan. Although sailboat terminology has varied across history, many terms now have specific meanings in the context of modern yachting.
The following sub-sections outline the most popular monohull sailing vessels. Additional types of vessels, such as multi-hull
Traditional sloop - Catalina 470
Today, the most common sailboat is the sloop, which features one mast and two sails: a normal mainsail, and a headsail. This simple configuration is very efficient for sailing into the wind. The mainsail is attached to the mast and the boom, which is a spar capable of swinging across the boat, depending on the direction of the wind. Depending on the size and design of the headsail it can be called a jib, Genoa, or spinnaker. When sailing directly downwind, a common configuration is to have the headsail sailed to one side of the boat, and the mainsail sailed to the other; this configuration is called "wing on wing".
The forestay is a line or cable near the top of the mast to a point near the bow. In Bermuda, where a rig design influenced by the Latin rig appeared on boats and came to be known as the Bermuda rig, a large spinnaker was carried on a spinnaker pole when running down-wind. An example of a typical sloop can be seen on the Islander 36.
Fractional rig sloop
On a fractional rig sloop the forestay does not run to the top of the mast, rather it connects at some point below. This allows the top of the mast to be raked aft by increasing the tension of the back stay, while arching the middle of the mast forward. Without great explanation, this gives a performance advantage in some conditions by flattening the sails. The big mainsail provides most of the drive, and the small headsail is easier for a short-handed crew to manage.
Gaff cutter - Kleine Freiheit
Main article: Cutter
The cutter is similar to a sloop with a single mast and mainsail, but generally carries the mast further aft to allow for the use of two head sails attached to two fore stays, the head stay and the inner stay, which carry the jib and stay sail respectively. This is rarely considered a racing configuration; however, it gives versatility to cruising boats, especially in high wind conditions, when a small jib can be flown from the inner stay.
Importantly, the traditional and most accurate definition of a true cutter, however, is not in the number of headsails, but rather that the outermost sails are set on stays that are not strictly structural to the rig itself. This in itself is a function of a much more complicated design set, involving mast placement, mast height, rig, boom length and fore-triangle size.
A catboat has a single mast mounted fairly forward and does not carry a jib. Most modern designs have only one sail, the mainsail; however the traditional catboat could carry multiple sails from the gaff rig. The designer of the Catboat is Brian Husband, master sailor of the early 1940s.
Ketches are similar to a sloop, but there is a second shorter mast astern of the mainmast, but forward of the rudder post. The second mast is called the mizzen mast and the sail is called the mizzen sail. A ketch can also be Cutter-rigged with two head sails.
A schooner can have two or more masts, the aftermost mast taller or equal to the height of the forward mast(s), distinguishing this design from a ketch or a yawl. Top sail schooners are rigged to carry a square sail near the top of their foremast, but generally modern schooners are gaff or marconi rigged.
A yawl is similar to a ketch, with the mizzen mast shorter than the main mast but the mizzen mast is carried astern of the rudder post. Generally the mizzen on a yawl is smaller than the mizzen on a ketch, and is used more for balancing the helm than for propulsion.
Dhoni or Doni (Dhivehi: ދޯނި pronounced Dōni) is a multi-purpose sailboat with lateen sails that is used in the Maldives. It is handcrafted and its use within the multi-island nation has been very important. A dhoni resembles a dhow, a traditional Arab sailing vessel.
A dinghy is a type of small sailboat. The term can also refer to small racing yachts or recreational open sailing boats. They are most common in youth sailing because of their shorter LOA, simple operation and minimal maintenance. They have three (or fewer) sails: the mainsail, jib, and spinnaker. Sailing dinghies have an overall length of seven to sixteen feet. This category of sailboats is split up into several subcategories such as: skiffs, high performance dinghies, cruising dinghies, classic dinghies, catamarans and racing dinghies.
Traditional sailboats are monohulls, but multi-hull catamarans and trimarans are gaining popularity. Monohull boats generally rely on ballast for stability, and usually are displacement hulls. This stabilizing ballast can, in boats designed for racing, be as much as 50% of the weight of the boat, but is generally around 30%. It creates two problems; one, it gives the monohull tremendous inertia, making it less maneuverable and reducing its acceleration. Secondly, unless it has been built with buoyant foam or air tanks, if a monohull fills with water, it will sink.
rely on the geometry and the broad stance of the multiple hulls for their stability, eschewing any form of ballast. Indeed, multihulls are designed to be as light-weight as possible, yet maintain structural integrity. They are often built with foam-filled flotation chambers and many modern commercial trimarans are rated as unsinkable, meaning that, should every crew compartment be completely filled with water, the hull itself has sufficient buoyancy to remain afloat.
This absence of ballast also results in some very real performance gains in terms of acceleration, top speed, and maneuverability.
The lack of ballast makes it much easier to get a multihull on plane, reducing its wetted surface area and thus its drag.The absence of drag improves wind precision, giving it its great handling.
Compared to a monohull
, acceleration to top speed is near-instantaneous.
Reduced overall weight means a reduced draft, with a much reduced underwater profile. This, in turn, results directly in reduced wetted surface area and drag, yielding higher top speeds.
Without a ballast keel, multihulls can go in shallow waters where monohulls can't.
There are some tradeoffs, however, in multihull design:
A well designed ballasted boat can recover from a capsize, even from turning over completely. The Swan 65 Sayula II won the 1973-74 Whitbread Round the World Race after doing a 180 degree capsize in the Southern Ocean. Righting a multihull that has gotten upside down is difficult in any case and impossible without outside help unless the boat is small or carries special equipment for the purpose. Several round the world racing multihulls have been lost after they capsized.
Multihulls often prove more difficult to tack, since the reduced weight leads directly to reduced momentum, causing multihulls to more quickly lose speed when headed into the wind.
Also, structural integrity
is much easier to achieve in a one piece monohull than in a two or three piece multihull whose connecting structure must be substantial and well connected to the hulls.
All these hull types may also be manufactured as, or outfitted with, hydrofoils.
All vessels have keels, it is the backbone of the hull. In traditional construction it is the structure upon which all else depends. Modern monocoque designs include a virtual keel. Even multihulls have keels. On a sailboat the word "keel" is also used to refer to the area that is added to the hull to improve its lateral plane. The lateral plane is what prevents leeway and allows sailing towards the wind. This can be an external piece or a part of the hull.
Most monohulls larger than a dinghy require ballast, depending on the design ballast will be 20 to 50 percent of the displacement. The ballast is often integrated into their keels as large masses of lead or cast iron. This secures the ballast and gets it as low as possible to improve its effectivness. External keels are cast in the shape of the keel. A monohull's keel is made effective by a combination of weight, depth and length.
Sailing yacht with a fin keel
Most modern monohull boats have fin keels, which are heavy and deep, but short in relation to the hull length. More traditional yachts carried a full keel which is generally half or more of the length of the boat. A recent feature is a winged keel, which is short and shallow, but carries a lot of weight in two "wings" which run sideways from the main part of the keel. Even more recent is the concept of canting keels, designed to move the weight at the bottom of a sailboat to the upwind side, allowing the boat to carry more sails.
Multihulls, on the other hand, have minimal need for such ballast, as they depend on the geometry of their design, the wide base of their multiple hulls, for their stability. Designers of performance multihulls, such as the Open 60's, go to great lengths to reduce overall boat weight as much as possible. This leads some to comment that designing a multihull is similar to designing an aircraft.
The centreboard or daggerboard is in essence a very lightweight keel, which is not permanently mounted and can be pulled up to accommodate shallow water. Some sports boats are designed to plane on top of the water since they feature centerboards or light keels. A centreboard is used to provide lift to counter the lateral force from the sails. This is required for sailboats to move in directions other than downwind, since the force of the sail is never closer than 45 degrees to the apparent wind.
A yacht /ˈjɒt/ is a recreational boat or ship. The term originated from the Dutch Jacht meaning "hunt".[note 1] It was originally defined as a light fast sailing vessel used by the Dutch navy to pursue pirates and other transgressors around and into the shallow waters of the Low Countries. After its selection by Charles II of England as the vessel to carry him to Britain from Holland for his restoration in 1660, it came to be used to mean a vessel used to convey important persons.
In modern use the term designates two rather different classes of watercraft, sailing and power boats. Yachts are different from working ships mainly by their leisure purpose, and it was not until the rise of the steamboat and other types of powerboat that sailing vessels in general came to be perceived as luxury, or recreational vessels. Later the term came to encompass motor boats for primarily private pleasure purposes as well.
Yacht lengths generally range from 10 metres (33 ft) up to dozens of metres (hundreds of feet). A luxury craft smaller than 12 metres (39 ft) is more commonly called a cabin cruiser or simply a cruiser. A superyacht generally refers to any yacht (sail or power) above 24 m (79 ft) and a megayacht generally refers to any yacht over 50 metres (164 ft). This size is small in relation to typical cruise liners and oil tankers.
Construction materials and techniques
Until the 1950s, almost all yachts were made of wood or steel, but a much wider range of materials is used today. Although wood hulls are still in production, the most common construction material is fibreglass, followed by aluminium, steel, carbon fibre, and ferrocement (rarer because of insurance difficulties). The use of wood has changed and is no longer limited to traditional board-based methods, but also include modern products such as plywood, veneers, skinned balsa and epoxy resins. Wood is mostly used by hobbyists or wooden boat purists when building an individual boat. Apart from 'space-age' materials like carbon fibre and aramid fibre, spruce veneers laminated with epoxy resins have the best weight-to-strength ratio of all boatbuilding materials. Many classes of small racing dinghies can only be built in wood to conform to class rules.
A small sailing yacht
Sailing yachts can range in overall length (Length Over All—LOA) from about 6 metres (20 ft) to well over 30 metres (98 ft), where the distinction between a yacht and a ship becomes blurred. Most privately owned yachts fall in the range of about 7 metres (23 ft)-14 metres (46 ft); the cost of building and keeping a yacht rises quickly as length increases. In the United States, sailors tend to refer to smaller yachts as sailboats, while referring to the general sport of sailing as yachting. Within the limited context of sailboat racing, a yacht is any sailing vessel taking part in a race, regardless of size.
Modern yachts have efficient sail-plans, most notably the Bermuda rig, that allow them to sail close to the wind. This capability is the result of a sail-plan and hull design.
Day sailing yachts are usually small, at under 6 metres (20 ft) in length. Sometimes called sailing dinghies, they often have a retractable keel, centreboard, or daggerboard. Most day sailing yachts do not have a cabin, as they are designed for hourly or daily use and not for overnight journeys. They may have a 'cuddy' cabin, where the front part of the hull has a raised solid roof to provide a place to store equipment or to offer shelter from wind or spray.
Weekender yachts are slightly larger, at under 9.5 metres (31 ft) in length. They may have twin keels or lifting keels such as in trailer sailers. This allows them to operate in shallow waters, and if needed "dry out"—become beached as the tide falls.This is important in the UK waters where many moorings are in tidal creeks. The hull shape (or twin-keel layout) allows the boat to sit upright when there is no water. Such boats are designed to undertake short journeys, rarely lasting more than 2 or 3 days. In coastal areas, long trips may be undertaken in a series of short hops. Weekenders usually have only a simple cabin, often consisting of a single "saloon" with bedspace for two to four people. Clever use of ergonomics allows space in the saloon for a galley (kitchen), seating, and navigation equipment. There is limited space for stores of water and food. Most are single-masted "Bermuda sloops", with a single foresail of the jib or genoa type and a single mainsail. Some are gaff rigged. The smallest of this type, generally called pocket yachts or pocket cruisers, and trailer sailers can be transported on special trailers.
An offshore sailing yacht
Cruising yachts are by the far the most common yacht in private use, making up most of the 7–14-metre (23–46 ft) range. These vessels can be quite complex in design, as they need a balance between docile handling qualities, interior space, good light-wind performance and on-board comfort. The huge range of such craft, from dozens of builders worldwide, makes it hard to give a single illustrative description. However, most favour a teardrop-planform hull, with a fine bow,a wide, flat bottom and deep single-fin keel with ample beam to give good stability. Most are single-masted Bermuda rigged sloops, with a single fore-sail of the jib or Genoa type and a single mainsail. Spinnaker sails, are often supplied for down-wind use. These types are often chosen as family vessels, especially those in the 8 to 12 m (26 to 39 ft) range. Such a vessel will usually have several cabins below deck. Typically there will be three double-berth cabins; a single large saloon with galley, seating and navigation equipment; and a "head" consisting of a toilet and shower-room. The interior is often finished in wood panelling, with plenty of storage space. Cruisers are quite capable of taking on long-range passages of many thousands of miles. Such boats have a cruising speed upwards of 6 knots. This basic design is typical of the standard types produced by the major yacht-builders.
Aside from this fairly standard design, built in numbers and using methods approaching mass production by the large yacht-building firms of Europe and North America, there are some common variations to suit a yacht for a more particular role or to emphasise one aspect of performance rather than the wide range of abilities needed in a standard design. The classic "long keel" yacht, where the keel is integrated into the lower portion of the hull and extends for all or most of the hull's length, rather than being a single fin attached to the hull at the centre, is still being built in small numbers. The long keel generally provides better directional stability, especially in rough weather, at the cost of greater weight, a narrower hull which decreases interior space, and poorer handling when under engine power or in tight conditions such as a marina.
The Twister is an example of a long-keeled yacht designed in the 1960s.
Whilst the cutter rig with twin foresails was once the standard rig for most cruising yachts until the 1960s (when it began to be replaced by the two-sail sloop rig) it is now only commonly found on larger cruising yachts (usually around 15 m (49 ft) and over). Other rig variations are found on many different sizes of yacht such as the yawl, ketch, schooner and even unusual sail plans such as the junk rig.
A yacht may also be a "cruiser-racer", which as the name implies is a blend between the cruiser and racing variants. This is often a builder's existing design with changes to the rigging, sails, keel and controls to provide better performance. Some of the interior appointments may be reduced or removed to save weight.
The fixed fin keel is most commonly found on modern cruising yachts world wide but some are still built with twin 'bilge' keels or with lifting fin keels which retract into the yacht's hull. In both cases these allow the yacht to sit upright on the seabed in shallow water or on areas that dry at low tide.
Most large yachts, 16 m (52 ft) and up, are also cruisers, but their design varies greatly as they are often "one off" designs tailored to the specific needs of the buyer.
Luxury sailing yachts
These yachts are generally 25 metres (82 ft) or longer. In recent years, these yachts have evolved from fairly simple vessels with basic accommodation into sophisticated and luxurious boats. This is largely due to reduced hull-building costs brought about by the introduction of fibreglass hulls, and increased automation and "production line" techniques for yacht building, especially in Europe.
On the biggest, 40 m (130 ft)-plus luxury yachts, every modern convenience, from air conditioning to television, is found. Sailing yachts of this size are often highly automated with, for example, computer-controlled electric winches controlling the sails. Such complexity requires dedicated power-generation systems. In recent years the amount of electric equipment used on yachts has increased greatly. Even 20 years ago, it was not common for a 7 m (23 ft) yacht to have electric lighting. Now all but the smallest, most basic yachts have electric lighting, radio, and navigation aids such as Global Positioning Systems. Yachts around 10 metres (33 ft) bring in comforts such as hot water, pressurised water systems, and refrigerators. Aids such as radar, echo-sounding and autopilot are common. This means that the auxiliary engine now also performs the vital function of powering an alternator to provide electrical power and to recharge the yacht's batteries. For yachts engaged on long-range cruising, wind-, water- and solar-powered generators can perform the same function.
Racing yachts try to reduce the wetted surface area, which creates drag, by keeping the hull light whilst having a deep and heavy bulb keel, allowing them to support a tall mast with a great sail area. Modern designs tend to have a very wide beam and a flat bottom aft, to provide buoyancy preventing an excessive heel angle and to promote surfing and planning. Speeds of up to 35 knots can be attained in extreme conditions. Dedicated offshore racing yachts sacrifice crew comfort for speed, having basic accommodation to reduce weight. Modern racing yachts may have twin rudders because of the wide stern. Since about 2000 water ballast transfer pumps have become more common as have transversely swinging keels. Both these stiffen the yacht and allow more sail to be carried in stronger winds. Depending on the type of race, such a yacht may have a crew of 15 or more. Very large inshore racing yachts may have a crew of 30. At the other extreme are "single handed" races, where one person alone must control the yacht.
Yacht races may be over a simple course of only a few miles, as in the harbour racing of the International One Design; long-distance, open-ocean races, like the Bermuda Race; or epic trans-global contests such as the Global Challenge, Volvo Ocean Race, Clipper Round the World Race and Mini Transat
The motive force being the wind, sailing is more economical and environmentally friendly than any other means of propulsion. A hybrid type of vessel is a motor sailing yacht that can use either sail or propulsion (or both) as conditions dictate.
Many "pure" sailing yachts are also equipped with a low-power internal-combustion engine for use in conditions of calm and when entering or leaving difficult anchorages. Vessels less than 7 metres (23 ft) in length generally carry a petrol outboard-motor of between 3.5 and 30 kilowatts (5 and 40 hp). Larger vessels have in-board diesel engines of between 15 and 75 kilowatts (20 and 101 hp) depending on size. In the common 7–14-metre (23–46 ft) class, engines of 15 to 30 kilowatts (20 to 40 hp) are the most common. Modern sailing yachts can be equipped with electric inboard motors in order to reduce consumption of fossil fuel. The latest technology are outboard electric pod drives that can also regenerate electricity (motogens). These motogens can be made retractable to increase the efficiency of the yacht. Some of these yachts are extremely efficient and do not need additional diesel generators. This technology is called Green Motion. Tests can be seen and read in the following magazines: Yachting Monthly, November 2010; the German magazine Yacht, January 2011;the Water kampioen from the Netherlands, May 2011 and in Voile magazine in December 2011 in France. The Mansura Trophy was awarded for this new propulsion system in May 2011.
Monohull yachts are typically fitted with a fixed keel or a centreboard (adjustable keel) below the waterline to counterbalance the overturning force of wind on the vessel's sails. Multihull yachts use two (catamarans) or three (trimarans) hulls widely separated from each other to provide a stable base that resists overturning.
Yachts moored at Rowe's Wharf in Boston Harbor
Motor yachts generally fit into the following categories:
Day cruiser yacht (no cabin, sparse amenities)
Weekender yacht (one or two basic cabins, basic galley appliances and plumbing)
Cruising yacht (sufficient amenities to allow for living aboard for extended periods)
Sport fishing yacht (yacht with living amenities and sporting fishing equipment)
Luxury yacht (similar to the last three types of yachts, with more luxurious finishings/amenities)
Motor yachts typically have one or two internal combustion engines that burn diesel fuel or gasoline. Depending on engine size, fuel costs may make motor yachts more expensive to operate than sailing yachts.
The shape of a motor yacht's hull may be based on displacement, planing, or in between. Although monohulls have long been the standard in motor yachts, multihulls are gaining in popularity.
Fiberglass (or fibreglass) (also called glass-reinforced plastic, GRP, glass-fiber reinforced plastic, or GFRP) is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. It is also known as GFK (for German: Glasfaserverstärkter Kunststoff).
Fiberglass is a lightweight, extremely strong, and robust material, and is used for many products. Although strength properties are somewhat lower than carbon fiber and it is less stiff, the material is typically far less brittle, and the raw materials are much less expensive. Its bulk strength and weight properties are also very favorable when compared to metals, and it can be easily formed using molding processes.
The plastic matrix may be a thermosetting plastic (most often epoxy, polyester or vinylester) or thermoplastic.
Common uses of fiberglass include high performance aircraft (gliders), boats, automobiles, baths, hot tubs, septic tanks, water tanks, roofing, pipes, cladding, casts, surfboards and external door skins.
Glass reinforcements used for fiberglass are supplied in different physical forms, microspheres, chopped or woven.
Unlike glass fibers used for insulation, for the final structure to be strong, the fiber's surfaces must be almost entirely free of defects, as this permits the fibers to reach gigapascal tensile strengths. If a bulk piece of glass were to be defect free, then it would be equally as strong as glass fibers; however, it is generally impractical to produce bulk material in a defect-free state outside of laboratory conditions.
The manufacturing process for glass fibers suitable for reinforcement uses large furnaces to gradually melt the silica sand, limestone, kaolin clay, fluorspar, colemanite, dolomite and other minerals to liquid form. Then it is extruded through bushings, which are bundles of very small orifices (typically 5–25 micrometres in diameter for E-Glass, 9 micrometres for S-Glass). These filaments are then sized (coated) with a chemical solution. The individual filaments are now bundled together in large numbers to provide a roving. The diameter of the filaments, as well as the number of filaments in the roving determine its weight. This is typically expressed in yield - yards per pound (how many yards of fiber in one pound of material, thus a smaller number means a heavier roving, example of standard yields are 225yield, 450yield, 675yield) or in tex - grams per km (how many grams 1 km of roving weighs, this is inverted from yield, thus a smaller number means a lighter roving
These rovings are then either used directly in a composite application such as pultrusion, filament winding (pipe), gun roving (automated gun chops the glass into short lengths and drops it into a jet of resin, projected onto the surface of a mold), or used in an intermediary step, to manufacture fabrics such as chopped strand mat (CSM) (made of randomly oriented small cut lengths of fiber all bonded together), woven fabrics, knit fabrics or uni-directional fabrics.
A sort of coating, or primer, is used which both helps protect the glass filaments for processing/manipulation as well as ensure proper bonding to the resin matrix, thus allowing for transfer of shear loads from the glass fibers to the thermoset plastic. Without this bonding, the fibers can 'slip' in the matrix and localised failure would ensue.
An individual structural glass fiber is both stiff and strong in tension and compression—that is, along its axis. Although it might be assumed that the fiber is weak in compression, it is actually only the long aspect ratio of the fiber which makes it seem so; i.e., because a typical fiber is long and narrow, it buckles easily. On the other hand, the glass fiber is weak in shear—that is, across its axis. Therefore if a collection of fibers can be arranged permanently in a preferred direction within a material, and if the fibers can be prevented from buckling in compression, then that material will become preferentially strong in that direction.
Furthermore, by laying multiple layers of fiber on top of one another, with each layer oriented in various preferred directions, the stiffness and strength properties of the overall material can be controlled in an efficient manner. In the case of fiberglass, it is the plastic matrix which permanently constrains the structural glass fibers to directions chosen by the designer. With chopped strand mat, this directionality is essentially an entire two dimensional plane; with woven fabrics or unidirectional layers, directionality of stiffness and strength can be more precisely controlled within the plane.
A fiberglass component is typically of a thin "shell" construction, sometimes filled on the inside with structural foam, as in the case of surfboards. The component may be of nearly arbitrary shape, limited only by the complexity and tolerances of the mold used for manufacturing the shell.
Fiberglass is an immensely versatile material which combines its light weight with an inherent strength to provide a weather resistant finish, with a variety of surface textures.
The development of fiber-reinforced plastic for commercial use was being extensively researched in the 1930s. It was particularly of interest to the aviation industry. Mass production of glass strands was accidentally discovered in 1932 when a researcher at the Owens-Illinois directed a jet of compressed air at a stream of molten glass and produced fibers. Owens joined up with the Corning company in 1935 and the method was adapted by Owens Corning to produce its patented "Fiberglas" (one "s"). A suitable resin for combining the "Fiberglas" with a plastic was developed in 1936 by du Pont. The first ancestor of modern polyester resins is Cyanamid's of 1942. Peroxide curing systems were used by then.
During World War II, fiberglass was developed as a replacement for the molded plywood used in aircraft radomes (fiberglass being transparent to microwaves). Its first main civilian application was for building of boats and sports-car bodies, where it gained acceptance in the 1950s. Its use has broadened to the automotive and sport equipment sectors as well as aircraft, although its use there is now partly being taken over by carbon fiber which weighs less per given volume and is stronger both by volume and by weight. Fiberglass uses also include hot tubs, pipes for drinking water and sewers, office plant display containers and flat roof systems.
Advanced manufacturing techniques such as pre-pregs and fiber rovings extend the applications and the tensile strength possible with fiber-reinforced plastics.
Fiberglass is also used in the telecommunications industry for shrouding the visual appearance of antennas, due to its RF permeability and low signal attenuation properties. It may also be used to shroud the visual appearance of other equipment where no signal permeability is required, such as equipment cabinets and steel support structures, due to the ease with which it can be molded, manufactured and painted to custom designs, to blend in with existing structures or brickwork. Other uses include sheet form made electrical insulators and other structural components commonly found in the power industries.
Because of fiberglass's light weight and durability, it is often used in protective equipment, such as helmets. Many sports use fiberglass protective gear, such as modern goaltender masks and newer baseball catcher's masks.
Several large fiberglass tanks at an airport
Storage tanks can be made of fiberglass with capacities up to about 300 tonnes. The smaller tanks can be made with chopped strand mat cast over a thermoplastic inner tank which acts as a preform during construction. Much more reliable tanks are made using woven mat or filament wound fibre with the fibre orientation at right angles to the hoop stress imposed in the side wall by the contents. They tend to be used for chemical storage because the plastic liner (often polypropylene) is resistant to a wide range of strong chemicals. Fiberglass tanks are also used for septic tanks.
Glass reinforced plastics are also used in the house building market for the production of roofing laminate, door surrounds, over-door canopies, window canopies and dormers, chimneys, coping systems, heads with keystones and sills. The use of fiberglass for these applications provides for a much faster installation and due to the reduced weight manual handling issues are reduced. With the advent of high volume manufacturing processes it is possible to construct fiberglass brick effect panels which can be used in the construction of composite housing. These panels can be constructed with the appropriate insulation which reduces heat loss.
GRP and GRE pipe systems can be used for a variety of applications, above and under the ground.
Cooling water systems
Drinking water systems
Waste water systems/Sewage systems
Fiberglass hand lay-up operation
A release agent, usually in either wax or liquid form, is applied to the chosen mold. This will allow the finished product to be removed cleanly from the mold. Resin—typically a 2-part polyester, vinyl or epoxy—is mixed with its hardener and applied to the surface. Sheets of fibreglass matting are laid into the mold, then more resin mixture is added using a brush or roller. The material must conform to the mold, and air must not be trapped between the fiberglass and the mold. Additional resin is applied and possibly additional sheets of fiberglass. Hand pressure, vacuum or rollers are used to make sure the resin saturates and fully wets all layers, and any air pockets are removed. The work must be done quickly enough to complete the job before the resin starts to cure, unless high temperature resins are used which will not cure until the part is warmed in an oven. In some cases, the work is covered with plastic sheets and vacuum is drawn on the work to remove air bubbles and press the fiberglass to the shape of the mold.
The fiberglass spray lay-up process is similar to the hand lay-up process but the difference comes from the application of the fiber and resin material to the mold. Spray-up is an open-molding composites fabrication process where resin and reinforcements are sprayed onto a mold. The resin and glass may be applied separately or simultaneously "chopped" in a combined stream from a chopper gun. Workers roll out the spray-up to compact the laminate. Wood, foam or other core material may then be added, and a secondary spray-up layer imbeds the core between the laminates. The part is then cured, cooled and removed from the reusable mold.
Pultrusion is a manufacturing method used to make strong, lightweight composite materials, in this case fiberglass. Fibers (the glass material) are pulled from spools through a device that coats them with a resin. They are then typically heat-treated and cut to length. Pultrusions can be made in a variety of shapes or cross-sections such as a W or S cross-section. The word pultrusion describes the method of moving the fibers through the machinery. It is pulled through using either a hand-over-hand method or a continuous-roller method. This is opposed to an extrusion, which would push the material through dies.
Chopped strand mat or CSM is a form of reinforcement used in fiberglass. It consists of glass fibers laid randomly across each other and held together by a binder.
It is typically processed using the hand lay-up technique, where sheets of material are placed in a mold and brushed with resin. Because the binder dissolves in resin, the material easily conforms to different shapes when wetted out. After the resin cures, the hardened product can be taken from the mold and finished.
Using chopped strand mat gives a fiberglass with isotropic in-plane material properties.
One notable feature of fiberglass is that the resins used are subject to contraction during the curing process. For polyester this contraction is often of the order of 5-6%, and for epoxy it can be much lower, about 2%.
When formed as part of fiberglass, because the fibers don't contract, the differential can create changes in the shape of the part during cure. Distortions will usually appear hours, days or weeks after the resin has set.
While this can be minimised by symmetric use of the fibers in the design, nevertheless internal stresses are created, and if these become too great, then cracks will form.
Air flow test for the extraction and filtration of styrene vapors in a production hall for GRP yachts
The National Toxicology Program ("NTP"), in June 2011, removed from its Report on Carcinogens all biosoluble glass wool used in home and building insulation and for non-insulation products. However, NTP classifies as Fibrous Glass Dust "Reasonably anticipated to be a human carcinogen (Certain Glass Wool Fibers (Inhalable))". Similarly, California's Office of Environmental Health Hazard Assessment ("OEHHA"), in November 2011, published a modification to its Proposition 65 listing to include only "Glass wool fibers (inhalable and biopersistent)." The U.S. NTP and California's OEHHA action means that a cancer warning label for biosoluble fiber glass home and building insulation is no longer required under Federal or California law. All fiber glass wools commonly used for thermal and acoustical insulation were reclassified by the International Agency for Research on Cancer ("IARC") in October 2001 as Not Classifiable as to carcinogenicity to humans
The European Union and Germany classify synthetic vitreous fibers as possibly or probably carcinogenic, but fibers can be exempt from this classification if they pass specific tests. Evidence for these classifications is primarily from studies on experimental animals and mechanisms of carcinogenesis. The glass wool epidemiology studies have been reviewed by a panel of international experts convened by the International Agency for Research on Cancer ("IARC"). These experts concluded: "Epidemiologic studies published during the 15 years since the previous IARC monographs review of these fibres in 1988 provide no evidence of increased risks of lung cancer or mesothelioma (cancer of the lining of the body cavities) from occupational exposures during the manufacture of these materials, and inadequate evidence overall of any cancer risk." Similar reviews of the epidemiology studies have been conducted by the Agency for Toxic Substances and Disease Registry ("ATSDR"), the National Toxicology Program, the National Academy of Sciences and Harvard's Medical and Public Health Schools which reached the same conclusion as IARC that there is no evidence of increased risk from occupational exposure to glass wool fibers.
Fiberglass will irritate the eyes, skin, and the respiratory system. Potential symptoms include irritation of eyes, skin, nose, throat, dyspnea (breathing difficulty); sore throat, hoarseness and cough. Scientific evidence demonstrates that fiber glass is safe to manufacture, install and use when recommended work practices are followed to reduce temporary mechanical irritation.
Fiberglass is resistant to mold but growth can occur if fiberglass becomes wet and contaminated with organic material. Fiberglass insulation that has become wet should be inspected for evidence of residual moisture and contamination. Contaminated fiberglass insulation should be promptly removed.
While the resins are cured, styrene vapors are released. These are irritating to mucous membranes and respiratory tract. Therefore, the Hazardous Substances Ordinance in Germany dictate a maximum occupational exposure limit of 86 mg/m³. In certain concentrations may even occur a potentially explosive mixture. Further manufacture of GRP components (grinding, cutting, sawing) goes along with the emission of fine dusts and chips containing glass filaments as well as of tacky dust in substantial quantities. These affect people's health and functionality of machines and equipment. To ensure safety regulations are adhered to and efficiency can be sustained, the installation of effective extraction and filtration equipment is needed.
Examples of fiberglass use
Kayaks made of fiberglass
Surfboards, tent poles
Gliders, kit cars, sports cars, microcars, karts, bodyshells, boats, kayaks, flat roofs, lorries, K21 Infantry Fighting Vehicle
Pods, domes and architectural features where a light weight is necessary
High end bicycles
Bodyparts for and entire automobiles, such as the Anadol, Reliant, Quantum Quantum Coupé, Chevrolet Corvette and Studebaker Avanti, and DeLorean DMC-12 under body
Antenna covers and structures, such as radomes, UHF broadcasting antennas, and pipes used in hex beam antennas for amateur radio communications
FRP tanks and vessels: FRP is used extensively to manufacture chemical equipment and tanks and vessels. BS4994 is a British standard related to this application
Most commercial velomobiles
Most printed circuit boards used in electronics consist of alternating layers of copper and fibreglass FR-4
Large commercial wind turbine blades
RF coils used in MRI scanners
Sub sea installation protection covers
Re-enforcement of asphalt pavement, as a fabric or mesh interlayer between lifts
Protective helmets used in various sports
Fiberglass Grating is used for walkways on ships, oil rigs and in factories
Fiber reinforced composite columns
Carbon-fiber-reinforced polymer, carbon-fiber-reinforced plastic or carbon-fiber reinforced thermoplastic (CFRP, CRP, CFRTP or often simply carbon fiber, or even carbon), is an extremely strong and light fiber-reinforced polymer which contains carbon fibers.
The binding polymer is often a thermoset resin such as epoxy, but other thermoset or thermoplastic polymers, such as polyester, vinyl ester or nylon, are sometimes used. The composite may contain other fibers, such as aramid e.g. Kevlar, Twaron, aluminium, or glass fibers, as well as carbon fiber. The properties of the final CFRP product can also be affected by the type of additives introduced to the binding matrix (the resin). The most frequent additive is silica, but other additives such as rubber and carbon nanotubes can be used. CFRPs are commonly used in the transportation industry; normally in cars, boats and trains, and in sporting goods industry for manufacture of bicycles, bicycle components, golfing equipment and fishing rods.
Although carbon fiber can be relatively expensive, it has many applications in aerospace and automotive fields, such as Formula One racing and wherever high strength-to-weight ratio and rigidity are required such as sailing boats and rowing shell hulls, top-end bicycles and motorcycles, As manufacturing techniques improve and costs reduce it is becoming increasingly common in small consumer goods that require strength, lightness and stiffness such as: laptop bodies, tripod legs, tent poles, fishing rods, hockey sticks, bows and arrows, racquet frames, stringed instrument bodies, drum shells, golf clubs, crash helmets and billiards cues.
The material is also referred to as graphite-reinforced polymer or graphite fiber-reinforced polymer (GFRP is less common, as it clashes with glass-(fiber)-reinforced polymer). In product advertisements, it is sometimes referred to simply as graphite fiber for short.
are composite materials. In this case the composite consists of two parts: a matrix and a reinforcement. In CFRP the reinforcement is carbon fiber, which provides the strength. The matrix is usually a polymer resin, such as epoxy, to bind the reinforcements together. Because CFRP consists of two distinct elements, the material properties depend on these two elements.
The reinforcement will give the CFRP its strength and rigidity; measured by stress and elastic modulus respectively. Unlike isotropic materials like steel and aluminum, CFRP has directional strength properties. The properties of CFRP depend on the layouts of the carbon fiber and the proportion of the carbon fibers relative to the polymer.
Despite its high initial strength-to-weight ratio, a design limitation of CFRP is its lack of a definable fatigue endurance limit. This means, theoretically, that stress cycle failure cannot be ruled out. While steel and many other structural metals and alloys do have estimable fatigue endurance limits, the complex failure modes of composites mean that the fatigue failure properties of CFRP are difficult to predict and design for. As a result, when using CFRP for critical cyclic-loading applications, engineers may need to design in considerable strength safety margins to provide suitable component reliability over its service life.
Carbon fiber reinforced polymer
The primary element of CFRP is a fiber. From these fibers, a unidirectional sheet is created. These sheets are layered onto each other in a quasi-isotropic layup, e.g. 0°, +60° or −60° relative to each other. From the elementary fiber, a bidirectional woven sheet can be created, i.e. a twill with a 2/2 weave. The process by which most carbon-fiber-reinforced polymer is made varies, depending on the piece being created, the finish (outside gloss) required, and how many of this particular piece are going to be produced. In addition, the choice of matrix can have a profound effect on the properties of the finished composite.
Many carbon-fiber-reinforced polymer parts are created with a single layer of carbon fabric that is backed with fiberglass. A tool called a chopper gun is used to quickly create these composite parts. Once a thin shell is created out of carbon fiber, the chopper gun cuts rolls of fiberglass into short lengths and sprays resin at the same time, so that the fiberglass and resin are mixed on the spot. The resin is either external mix, wherein the hardener and resin are sprayed separately, or internal mixed, which requires cleaning after every use. Manufacturing methods may include the following:
One method of producing graphite-epoxy parts is by layering sheets of carbon fiber cloth into a mold in the shape of the final product. The alignment and weave of the cloth fibers is chosen to optimize the strength and stiffness properties of the resulting material. The mold is then filled with epoxy and is heated or air-cured. The resulting part is very corrosion-resistant, stiff, and strong for its weight. Parts used in less critical areas are manufactured by draping cloth over a mold, with epoxy either preimpregnated into the fibers (also known as pre-preg) or "painted" over it. High-performance parts using single molds are often vacuum-bagged and/or autoclave-cured, because even small air bubbles in the material will reduce strength. An alternative to the autoclave method is to use internal pressure via inflatable air bladders or EPS foam inside the non-cured laid-up carbon fiber.
For simple pieces of which relatively few copies are needed (1–2 per day), a vacuum bag can be used. A fiberglass, carbon fiber or aluminum mold is polished and waxed, and has a release agent applied before the fabric and resin are applied, and the vacuum is pulled and set aside to allow the piece to cure (harden). There are two ways to apply the resin to the fabric in a vacuum mold.
The first method is manual and called a wet layup, where the two-part resin is mixed and applied before being laid in the mold and placed in the bag. The other one is done by infusion, where the dry fabric and mold are placed inside the bag while the vacuum pulls the resin through a small tube into the bag, then through a tube with holes or something similar to evenly spread the resin throughout the fabric. Wire loom works perfectly for a tube that requires holes inside the bag. Both of these methods of applying resin require hand work to spread the resin evenly for a glossy finish with very small pin-holes.
A third method of constructing composite materials is known as a dry layup. Here, the carbon fiber material is already impregnated with resin (pre-preg) and is applied to the mold in a similar fashion to adhesive film. The assembly is then placed in a vacuum to cure. The dry layup method has the least amount of resin waste and can achieve lighter constructions than wet layup. Also, because larger amounts of resin are more difficult to bleed out with wet layup methods, pre-preg parts generally have fewer pinholes. Pinhole elimination with minimal resin amounts generally require the use of autoclave pressures to purge the residual gases out.
A quicker method uses a compression mold. This is a two-piece (male and female) mold usually made out of fiberglass or aluminum that is bolted together with the fabric and resin between the two. The benefit is that, once it is bolted together, it is relatively clean and can be moved around or stored without a vacuum until after curing. However, the molds require a lot of material to hold together through many uses under that pressure.
For difficult or convoluted shapes, a filament winder can be used to make CFRP parts by winding filaments around a mandrel or a core.
CFRP is widely used in micro air vehicles (MAVs) because of its high strength to weight ratio.
Ultralight aircraft (see SSDR) such as the E-Go, rely heavily on CFRP in order to meet the category weight compliance requirement of less than 115 kg (254 lb) without pilot or fuel.
Honeycomb structure made of carbon-fiber-reinforced polymer on a BMW i3
Carbon-fiber-reinforced polymer is used extensively in high-end automobile racing. The high cost of carbon fiber is mitigated by the material's unsurpassed strength-to-weight ratio, and low weight is essential for high-performance automobile racing.
Race-car manufacturers have also developed methods to give carbon fiber pieces strength in a certain direction, making it strong in a load-bearing direction, but weak in directions where little or no load would be placed on the member. Conversely, manufacturers developed omnidirectional carbon fiber weaves that apply strength in all directions. This type of carbon fiber assembly is most widely used in the "safety cell" monocoque chassis assembly of high-performance race-cars.
Many supercars over the past few decades have incorporated CFRP extensively in their manufacture, using it for their monocoque chassis as well as other components.
Cast vinyl has also been used in automotive applications for aesthetics, as well as heat and abrasion resistance. Most top-of-the-line cast vinyl materials such as 3M's DiNoc (interior use) and SI's Si-1000 3D (exterior use) have lifespans of 10+ years when installed correctly.
Until recently, the material has had limited use in mass-produced cars because of the expense involved in terms of materials, equipment, and the relatively limited pool of individuals with expertise in working with it. Recently, several mainstream vehicle manufacturers have started to use CFRP in everyday road cars.
Use of the material has been more readily adopted by low-volume manufacturers who used it primarily for creating body-panels for some of their high-end cars due to its increased strength and decreased weight compared with the glass-reinforced polymer they used for the majority of their products.
Use of carbon fiber in a vehicle can appreciably reduce the weight and hence the size of its frame. This will also facilitate designers' and engineers' creativity and allow more in-cabin space for commuters. The new BMW i3 is made with a carbon fiber that not only reduces weight in the car, but reduces the amount of water and electricity used to make it.
Further information: Structural applications of FRP
Carbon-fiber-reinforced polymer (CFRP) has become a notable material in structural engineering applications. Studied in an academic context as to its potential benefits in construction, it has also proved itself cost-effective in a number of field applications strengthening concrete, masonry, steel, cast iron, and timber structures. Its use in industry can be either for retrofitting to strengthen an existing structure or as an alternative reinforcing (or pre-stressing) material instead of steel from the outset of a project.
Retrofitting has become the increasingly dominant use of the material in civil engineering, and applications include increasing the load capacity of old structures (such as bridges) that were designed to tolerate far lower service loads than they are experiencing today, seismic retrofitting, and repair of damaged structures. Retrofitting is popular in many instances as the cost of replacing the deficient structure can greatly exceed its strengthening using CFRP.
Applied to reinforced concrete structures for flexure, CFRP typically has a large impact on strength (doubling or more the strength of the section is not uncommon), but only a moderate increase in stiffness (perhaps a 10% increase). This is because the material used in this application is typically very strong (e.g., 3000 MPa ultimate tensile strength, more than 10 times mild steel) but not particularly stiff (150 to 250 GPa, a little less than steel, is typical). As a consequence, only small cross-sectional areas of the material are used. Small areas of very high strength but moderate stiffness material will significantly increase strength, but not stiffness.
CFRP can also be applied to enhance shear strength of reinforced concrete by wrapping fabrics or fibers around the section to be strengthened. Wrapping around sections (such as bridge or building columns) can also enhance the ductility of the section, greatly increasing the resistance to collapse under earthquake loading. Such 'seismic retrofit' is the major application in earthquake-prone areas, since it is much more economic than alternative methods.
If a column is circular (or nearly so) an increase in axial capacity is also achieved by wrapping. In this application, the confinement of the CFRP wrap enhances the compressive strength of the concrete. However, although large increases are achieved in the ultimate collapse load, the concrete will crack at only slightly enhanced load, meaning that this application is only occasionally used.
Specialist ultra-high modulus CFRP (with tensile modulus of 420 GPa or more) is one of the few practical methods of strengthening cast-iron beams. In typical use, it is bonded to the tensile flange of the section, both increasing the stiffness of the section and lowering the neutral axis, thus greatly reducing the maximum tensile stress in the cast iron.
When used as a replacement for steel, CFRP bars could be used to reinforce concrete structures, however the applications are not common.
CFRP could be used as pre-stressing materials due to their high strength. The advantages of CFRP over steel as a pre-stressing material, namely its light weight and corrosion resistance, should enable the material to be used for niche applications such as in offshore environments. However, there are practical difficulties in anchorage of carbon fiber strands and applications of this are rare.
In the United States, pre-stressed concrete cylinder pipes (PCCP) account for a vast majority of water transmission mains. Due to their large diameters, failures of PCCP are usually catastrophic and affect large populations. Approximately 19,000 miles of PCCP have been installed between 1940 and 2006. Corrosion in the form of hydrogen embrittlement has been blamed for the gradual deterioration of the pre-stressing wires in many PCCP lines. Over the past decade, CFRPs have been utilized to internally line PCCP, resulting in a fully structural strengthening system. Inside a PCCP line, the CFRP liner acts as a barrier that controls the level of strain experienced by the steel cylinder in the host pipe. The composite liner enables the steel cylinder to perform within its elastic range, to ensure the pipeline's long-term performance is maintained. CFRP liner designs are based on strain compatibility between the liner and host pipe.
CFRP is a more costly material than its counterparts in the construction industry, glass fiber-reinforced polymer (GFRP) and aramid fiber-reinforced polymer (AFRP), though CFRP is, in general, regarded as having superior properties.
Much research continues to be done on using CFRP both for retrofitting and as an alternative to steel as a reinforcing or pre-stressing material. Cost remains an issue and long-term durability questions still remain. Some are concerned about the brittle nature of CFRP, in contrast to the ductility of steel. Though design codes have been drawn up by institutions such as the American Concrete Institute, there remains some hesitation among the engineering community about implementing these alternative materials. In part, this is due to a lack of standardization and the proprietary nature of the fiber and resin combinations on the market.
Carbon fiber microelectrodes
Carbon fibers are used for fabrication of carbon-fiber microelectrodes. In this application typically a single carbon fiber with diameter of 5-7 μm is sealed in a glass capillary. At the tip the capillary is either sealed with epoxy and polished to make carbon-fiber disk microelectrode or the fiber is cut to a length of 75-150 μm to make carbon-fiber cylinder electrode. Carbon-fiber microelectrodes are used either in amperometry or fast-scan cyclic voltammetry for detection of biochemical signaling.
A carbon-fiber and Kevlar canoe
CFRP is now widely used in sports equipment. For the same strength, a CFRP bicycle frame weighs less than one of steel, aluminum, or titanium. The type and orientation of the carbon-fiber weave can be designed to maximize stiffness and minimize the chance of failure. The variety of shapes it can be built into has further increased stiffness and also allowed aerodynamic tube sections. CFRP frames, forks, handlebars, seatposts, and crank arms are becoming more common on medium as well as higher-priced bicycles.
CFRP is used in squash, tennis and badminton racquets, sport kite spars, high quality arrow shafts, hockey sticks, fishing rods, surfboards and rowing shells. Amputee athletes such as Oscar Pistorius use carbon fiber blades for running. It is used as a shank plate in some basketball sneakers to keep the foot stable, usually running the length of the shoe just above the sole and left exposed in some areas, usually in the arch.
In 2006, cricket bats with a thin carbon-fiber layer on the back were introduced and used in competitive matches by high-profile players including Ricky Ponting and Michael Hussey. The carbon fiber was claimed merely to increase the durability of the bats but were banned from all first-class matches by the ICC in 2007.
Although lighter and stiffer than items made of traditional metals, CFRP may, under some circumstances, show significant rates of cracking and failure. This can occur as because of impact or if components are over-torqued or improperly installed but it is possible for broken carbon frames to be repaired.
The fire resistance of polymers and thermo-set composites is significantly improved if a thin layer of carbon fibers is moulded near the surface because a dense, compact layer of carbon fibers efficiently reflects heat.
CFRP is also finding application in an increasing number of high-end products that require stiffness and low weight, these include:
Laptop cases by an increasing number of manufacturers.
Audio components such as turntables and loudspeakers.
Musical instruments, including violin bows, guitar pick-guards, bagpipe chanters and entire musical instruments such as Luis and Clark's carbon fiber cellos, violas and violins.
Kite systems use carbon fiber reinforced rods to obtain shapes and performances priorly not possible.
Firearms use it to replace certain metal, wood, and fibreglass components but many of the internal parts are still limited to metal alloys as current reinforced plastics are unsuitable.
High-performance radio-controlled vehicle and aircraft components such as helicopter rotor blades.
Consumer items such as the handles of high-end knives.
Carbon-fiber-reinforced polymers (CFRPs) have a long service lifetime when protected from the sun. When it is time to decommission CFRPs, they cannot be melted down in air like many metals. When free of vinyl (PVC or polyvinyl chloride) and other halogenated polymers, CFRPs can be thermally decomposed via thermal depolymerization in an oxygen-free environment. This can be accomplished in a refinery in a one-step process. Capture and reuse of the carbon and monomers is then possible. CFRPs can also be milled or shredded at low temperature to reclaim the carbon fiber, however this process shortens the fibers dramatically. Just as with downcycled paper, the shortened fibers cause the recycled material to be weaker than the original material. There are still many industrial applications that do not need the strength of full-length carbon fiber reinforcement. For example, chopped reclaimed carbon fiber can be used in consumer electronics, such as laptops. It provides excellent reinforcement of the polymers used even if it lacks the strength-to-weight ratio of an aerospace component.
Carbon nano-tube reinforced polymer
In 2009, Zyvex Technologies introduced carbon nanotube-reinforced epoxy and carbon prepregs. Carbon nanotube reinforced polymer (CNRP) is several times stronger and tougher than CFRP and was used in the Lockheed Martin F-35 Lightning II as a structural material for aircraft. CNRP still uses carbon fiber as the primary reinforcement, but the binding matrix is a carbon nano-tube filled epoxy.
Epoxy is the cured end product of epoxy resins, as well as a colloquial name for the epoxide functional group.
Epoxy resins, also known as polyepoxides are a class of reactive prepolymers and polymers which contain epoxide groups. Epoxy resins may be reacted (cross-linked) either with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols, and thiols. These co-reactants are often referred to as hardeners or curatives, and the cross-linking reaction is commonly referred to as curing. Reaction of polyepoxides with themselves or with polyfunctional hardeners forms a thermosetting polymer, often with strong mechanical properties as well as high temperature and chemical resistance. Epoxy has a wide range of applications, including metal coatings, use in electronic and electrical components, high tension electrical insulators, fibre-reinforced plastic materials, and structural adhesives. Epoxy resin is employed to bind gutta percha in some root canal procedures.
Epoxy resins are low molecular weight pre-polymers or higher molecular weight polymers which normally contain at least two epoxide groups. The epoxide group is also sometimes referred to as a glycidyl or oxirane group.
A wide range of epoxy resins are produced industrially. The raw materials for epoxy resin production are today largely petroleum derived, although some plant derived sources are now becoming commercially available (e.g. plant derived glycerol used to make epichlorohydrin).
Epoxy resins are polymeric or semi-polymeric materials, and as such rarely exist as pure substances, since variable chain length results from the polymerisation reaction used to produce them. High purity grades can be produced for certain applications, e.g. using a distillation purification process. One disadvantage of high purity liquid grades is their tendency to form crystalline solids due to their highly regular structure, which require melting to enable processing.
An important characteristic of epoxy resins is the epoxide content. This is commonly expressed as the epoxide number, which is the number of epoxide equivalents in 1 kg of resin (Eq./kg), or as the equivalent weight, which is the weight in grams of resin containing 1 mole equivalent of epoxide (g/mol). One measure may be simply converted to another:
Equivalent weight (g/mol) = 1000 / epoxide number (Eq./kg)
The equivalent weight or epoxide
number is used to calculate the amount of co-reactant (hardener) required when curing epoxy resins. Epoxies are typically cured with stoichiometric or near-stoichiometric quantities of curative to achieve the best physical properties.
As with other classes of thermosetting polymer materials, blending different grades of epoxy resin, as well as use of additives, plasticizers or fillers is common to achieve the desired processing and/or final properties, or to reduce cost. Use of blending, additives, and fillers is often referred to as formulating.
Bisphenol A epoxy resin
The most common and important class of epoxy resins is formed from reacting epichlorohydrin with bisphenol A to form diglycidyl ethers of bisphenol A. The simplest resin of this class is formed from reacting two moles of epichlorohydrin with one mole of bisphenol A to form the bisphenol A diglycidyl ether (commonly abbreviated to DGEBA or BADGE). DGEBA resins are transparent colourless-to-pale-yellow liquids at room temperature, with viscosity typically in the range of 5-15 Pa.s at 25°C. Industrial grades normally contain some distribution of molecular weight, since pure DGEBA shows a strong tendency to form a crystalline solid upon storage at ambient temperature.
Structure of bisphenol-A diglycidyl ether epoxy resin: n denotes the number of polymerized subunits and is typically in the range from 0 to 25
Increasing the ratio of bisphenol A to epichlorohydrin during manufacture produces higher molecular weight linear polyethers with glycidyl end groups, which are semi-solid to hard crystalline materials at room temperature depending on the molecular weight achieved. As the molecular weight of the resin increases, the epoxide content reduces and the material behaves more and more like a thermoplastic. Very high molecular weight polycondensates (ca. 30 000 – 70 000 g/mol) form a class known as phenoxy resins and contain virtually no epoxide groups (since the terminal epoxy groups are insignificant compared to the total size of the molecule). These resins do however contain hydroxyl groups throughout the backbone, which may also undergo other cross-linking reactions, e.g. with aminoplasts, phenoplasts and isocyanates.
Bisphenol F epoxy resin
Bisphenol F may also undergo epoxidation in a similar fashion to bisphenol A. Compared to DGEBA, bisphenol F epoxy resins have lower viscosity and a higher mean epoxy content per gram, which (once cured) gives them increased chemical resistance.
Novolac epoxy resin
Reaction of phenols with formaldehyde and subsequent glycidylation with epichlorohydrin produces epoxidised novolacs, such as epoxy phenol novolacs (EPN) and epoxy cresol novolacs (ECN). These are highly viscous to solid resins with typical mean epoxide functionality of around 2 to 6. The high epoxide functionality of these resins forms a highly crosslinked polymer network displaying high temperature and chemical resistance, but low flexibility. 100% solids hybrid novolac epoxy resin systems have been developed that contain no solvents and no volatile or organic compounds. These hybrid novolac epoxies have been documented to withstand up to 98% sulfuric acid.
Aliphatic epoxy resin
There are two types of aliphatic epoxy resins: glycidyl epoxy resins and cycloaliphatic epoxides.
Glycidyl epoxy resins are typically formed by the reaction of epichlorohydrin with aliphatic alcohols or polyols to give glycidyl ethers or aliphatic carboxylic acids to give glycidyl esters. This reaction is normally done in the presence of an alkali, such as sodium hydroxide, to facilitate the dehydrochlorination of the intermediate chlorohydrin. The resulting resins may be monofunctional (e.g. dodecanol glycidyl ether), difunctional (diglycidyl ester of hexahydrophthalic acid), or higher functionality (e.g. trimethylolpropane triglycidyl ether). These resins typically display low viscosity at room temperature (10-200 mPa.s) and are often used as reactive diluents. As such, they are employed to modify (reduce) the viscosity of other epoxy resins. This has led to the term 'modified epoxy resin' to denote those containing viscosity-lowering reactive diluents. However, they are also used without other epoxide ingredients along with anhydride curing agents such as hexahydrophthalic anhydride to make molded objects such as high voltage insulators. This is in fact the main use of the diglycidyl esters.
The cycloaliphatic epoxides contain one or more cycloaliphatic rings in the molecule to which the oxirane ring is fused (e.g. 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate). They are formed by the reaction of cyclo-olefins with a peracid, such as peracetic acid. This class also displays low viscosity at room temperature, but offers significantly higher temperature resistance and correspondingly better electrical properties at high temperatures to cured resins than the glycidyl aliphatic epoxy resins. Another advantage is the complete absence of chlorine, since no epichlorohydrin is used in the manufacturing process. This is particularly useful for electronic applications such as the encapsulation of light emitting diodes. However, room temperature reactivity is rather low compared to other classes of epoxy resin, and high temperature curing using suitable accelerators is normally required.
Glycidylamine epoxy resins are higher functionality epoxies which are formed when aromatic amines are reacted with epichlorohydrin. Important industrial grades are triglycidyl-p-aminophenol (functionality 3) and N,N,N,N-tetraglycidyl-4,4-methylenebis benzylamine (functionality 4). The resins are low to medium viscosity at room temperature, which makes them easier to process than EPN or ECN resins. This coupled with high reactivity, plus high temperature resistance and mechanical properties of the resulting cured network make them important materials for aerospace composite applications.
Curing epoxy resins
In general, uncured epoxy resins have only poor mechanical, chemical and heat resistance properties. However, good properties are obtained by reacting the linear epoxy resin with suitable curatives to form three-dimensional cross-linked thermoset structures. This process is commonly referred to as curing. Curing of epoxy resins is an exothermic reaction and in some cases produces sufficient heat to cause thermal degradation if not controlled.
Curing may be achieved by reacting an epoxy with itself (homopolymerisation) or by forming a copolymer with polyfunctional curatives or hardeners. In principle, any molecule containing a reactive hydrogen may react with the epoxide groups of the epoxy resin. Common classes of hardeners for epoxy resins include amines, acids, acid anhydrides, phenols, alcohols and thiols. Relative reactivity (lowest first) is approximately in the order: phenol < anhydride < aromatic amine < cycloaliphatic amine < aliphatic amine < thiol.
Whilst some epoxy resin/ hardener combinations will cure at ambient temperature, many require heat, with temperatures up to 150°C being common, and up to 200°C for some specialist systems. Insufficient heat during cure will result in a network with incomplete polymerisation, and thus reduced mechanical, chemical and heat resistance. Cure temperature should typically attain the glass transition temperature (Tg) of the fully cured network in order to achieve maximum properties. Temperature is sometimes increased in a step-wise fashion to control the rate of curing and prevent excessive heat build-up from the exothermic reaction.
Hardeners which show only low or limited reactivity at ambient temperature, but which react with epoxy resins at elevated temperature are referred to as latent hardeners. When using latent hardeners, the epoxy resin and hardener may be mixed and stored for some time prior to use, which is advantageous for many industrial processes. Very latent hardeners enable one-component (1K) products to be produced, whereby the resin and hardener are supplied pre-mixed to the end user and only require heat to initiate curing. One-component products generally have shorter shelf-lives than standard 2-component systems, and products may require cooled storage and transport.
The epoxy curing reaction may be accelerated by addition of small quantities of accelerators. Tertiary amines, carboxylic acids and alcohols (especially phenols) are effective accelerators. Bisphenol A is a highly effective and widely used accelerator, but is now increasingly replaced due to health concerns with this substance.
Epoxy resin may be reacted with itself in the presence of an anionic catalyst (a Lewis base such as tertiary amines or imidazoles) or a cationic catalyst (a Lewis acid such as a boron trifluoride complex) to form a cured network. This process is known as catalytic homopolymerisation. The resulting network contains only ether bridges, and exhibits high thermal and chemical resistance, but is brittle and often requires elevated temperature to effect curing, so finds only niche applications industrially. Epoxy homopolymerisation is often used when there is a requirement for UV curing, since cationic UV catalysts may be employed (e.g. for UV coatings).
Structure of TETA, a typical hardener. The amine (NH2) groups react with the epoxide groups of the resin during polymerisation.
Polyfunctional primary amines form an important class of epoxy hardeners. Primary amines undergo an addition reaction with the epoxide group to form a hydroxyl group and a secondary amine. The secondary amine can further react with an epoxide to form a tertiary amine and an additional hydroxyl group. Kinetic studies have shown the reactivity of the primary amine to be approximately double that of the secondary amine. Use of a difunctional or polyfunctional amine forms a three-dimensional cross-linked network. Aliphatic, cycloaliphatic and aromatic amines are all employed as epoxy hardeners. Amine type will alter both the processing properties (viscosity, reactivity) and the final properties (mechanical, temperature and chemical resistance) of the cured copolymer network. Thus amine structure is normally selected according to the application. Reactivity is broadly in the order aliphatic amines > cycloaliphatic amines > aromatic amines. Temperature resistance generally increases in the same order, since aromatic amines form much more rigid structures than aliphatic amines. Whilst aromatic amines were once widely used as epoxy resin hardeners due to the excellent end properties they imparted, health concerns with handling these materials means that they have now largely been replaced by safer aliphatic or cycloaliphatic alternatives.
Epoxy resins may be cured with cyclic anhydrides at elevated temperatures. Reaction occurs only after opening of the anhydride ring, e.g. by secondary hydroxyl groups in the epoxy resin. A possible side reaction may also occur between the epoxide and hydroxyl groups, but this may be suppressed by addition of tertiary amines. The low viscosity and high latency of anhydride hardeners makes them suitable for processing systems which require addition of mineral fillers prior to curing, e.g. for high voltage electrical insulators.
, such as bisphenol A or novolacs can react with epoxy resins at elevated temperatures (130-180°C), normally in the presence of a catalyst. The resulting material has ether linkages and displays higher chemical and oxidation resistance than typically obtained by curing with amines or anhydrides. Since many novolacs are solids, this class of hardeners is often employed for powder coatings.
Also known as mercaptans, thiols with the (S-H) functional group, contain an electron poor hydrogen which reacts very readily with the epoxide group, even at ambient or sub-ambient temperatures. Whilst the resulting network does not typically display high temperature or chemical resistance, the high reactivity of the thiol group makes it useful for applications where heated curing is not possible, or very fast cure is required e.g. for domestic DIY adhesives and chemical rock bolt anchors. Thiols have a characteristic odour, which can be detected in many two-component household adhesives.
The first commercial attempts to prepare resins from epichlorohydrin were made in 1927 in the United States. Credit for the first synthesis of bisphenol-A-based epoxy resins is shared by Dr. Pierre Castan of Switzerland and Dr. S.O. Greenlee of the United States in 1936. Dr. Castan's work was licensed by Ciba, Ltd. of Switzerland, which went on to become one of the three major epoxy resin producers worldwide. Ciba's epoxy business was spun off and later sold in the late 1990s and is now the Advanced Materials business unit of Huntsman Corporation of the United States. Dr. Greenlee's work was for the firm of Devoe-Reynolds of the United States. Devoe-Reynolds, which was active in the early days of the epoxy resin industry, was sold to Shell Chemical (now Momentive Specialty Chemicals, formerly Hexion, Resolution Polymers and others).
The shelf life of unmixed two-part epoxies is long. There are many anecdotal reports of epoxies mislaid for decades and then used successfully.
The applications for epoxy-based materials are extensive and include coatings, adhesives and resin matrices for composite materials such as those using carbon fiber and fiberglass reinforcements (although polyester, vinyl ester, and other thermosetting resins are also used for glass-reinforced plastic). The chemistry of epoxies and the range of commercially available variations allows cure polymers to be produced with a very broad range of properties. In general, epoxies are known for their excellent adhesion, chemical and heat resistance, good-to-excellent mechanical properties and very good electrical insulating properties. Many properties of epoxies can be modified (for example silver-filled epoxies with good electrical conductivity are available, although epoxies are typically electrically insulating). Variations offering high thermal insulation, or thermal conductivity combined with high electrical resistance for electronics applications, are available.
Two part epoxy coatings were developed for heavy duty service on metal substrates and use less energy than heat-cured powder coatings. These systems generally use a 4:1 by volume mixing ratio, and dry quickly providing a tough, protective coating with excellent hardness. Their low volatility and water cleanup makes them useful for factory cast iron, cast steel, cast aluminium applications and reduces exposure and flammability issues associated with solvent-borne coatings. They are usually used in industrial and automotive applications since they are more heat resistant than latex-based and alkyd-based paints. Epoxy paints tend to deteriorate, known as chalk out, due to UV exposure.
Polyester epoxies are used as powder coatings for washers, driers and other "white goods". Fusion Bonded Epoxy Powder Coatings (FBE) are extensively used for corrosion protection of steel pipes and fittings used in the oil and gas industry, potable water transmission pipelines (steel), and concrete reinforcing rebar. Epoxy coatings are also widely used as primers to improve the adhesion of automotive and marine paints especially on metal surfaces where corrosion (rusting) resistance is important. Metal cans and containers are often coated with epoxy to prevent rusting, especially for foods like tomatoes that are acidic. Epoxy resins are also used for decorative flooring applications such as terrazzo flooring, chip flooring, and colored aggregate flooring. Epoxy flooring has been proven to be an environmentally friendly alternate to other types of flooring, reducing the facility's impact on the environment through less water consumption and less pesticides needed.
Special epoxy is strong enough to withstand the forces between a surfboard fin and the fin mount. This epoxy is waterproof and capable of curing underwater. The blue-coloured epoxy on the left is still undergoing curing.
Epoxy adhesives are a major part of the class of adhesives called "structural adhesives" or "engineering adhesives" (that includes polyurethane, acrylic, cyanoacrylate, and other chemistries.) These high-performance adhesives are used in the construction of aircraft, automobiles, bicycles, boats, golf clubs, skis, snowboards, and other applications where high strength bonds are required. Epoxy adhesives can be developed to suit almost any application. They can be used as adhesives for wood, metal, glass, stone, and some plastics. They can be made flexible or rigid, transparent or opaque/colored, fast setting or slow setting. Epoxy adhesives are better in heat and chemical resistance than other common adhesives. In general, epoxy adhesives cured with heat will be more heat- and chemical-resistant than those cured at room temperature. The strength of epoxy adhesives is degraded at temperatures above 350 °F (177 °C).
Some epoxies are cured by exposure to ultraviolet light. Such epoxies are commonly used in optics, fiber optics, and optoelectronics.
Epoxy systems are used in industrial tooling applications to produce molds, master models, laminates, castings, fixtures, and other industrial production aids. This "plastic tooling" replaces metal, wood and other traditional materials, and generally improves the efficiency and either lowers the overall cost or shortens the lead-time for many industrial processes. Epoxies are also used in producing fiber-reinforced or composite parts. They are more expensive than polyester resins and vinyl ester resins, but usually produce stronger and more temperature-resistant composite parts.
An epoxy encapsulated hybrid circuit on a printed circuit board.
The interior of a pocket calculator. The dark lump of epoxy in the center covers the processor chip
Epoxy resin formulations are important in the electronics industry, and are employed in motors, generators, transformers, switchgear, bushings, and insulators. Epoxy resins are excellent electrical insulators and protect electrical components from short circuiting, dust and moisture. In the electronics industry epoxy resins are the primary resin used in overmolding integrated circuits, transistors and hybrid circuits, and making printed circuit boards. The largest volume type of circuit board—an "FR-4 board"—is a sandwich of layers of glass cloth bonded into a composite by an epoxy resin. Epoxy resins are used to bond copper foil to circuit board substrates, and are a component of the solder mask on many circuit boards.
Flexible epoxy resins are used for potting transformers and inductors. By using vacuum impregnation on uncured epoxy, winding-to-winding, winding-to-core, and winding-to-insulator air voids are eliminated. The cured epoxy is an electrical insulator and a much better conductor of heat than air. Transformer and inductor hot spots are greatly reduced, giving the component a stable and longer life than unpotted product.
Epoxy resins are applied using the technology of resin dispensing.
Consumer and marine applications
Epoxies are sold in hardware stores, typically as a pack containing separate resin and hardener, which must be mixed immediately before use. They are also sold in boat shops as repair resins for marine applications. Epoxies typically are not used in the outer layer of a boat because they deteriorate by exposure to UV light. They are often used during boat repair and assembly, and then over-coated with conventional or two-part polyurethane paint or marine-varnishes that provide UV protection.
There are two main areas of marine use. Because of the better mechanical properties relative to the more common polyester resins, epoxies are used for commercial manufacture of components where a high strength/weight ratio is required. The second area is that their strength, gap filling properties and excellent adhesion to many materials including timber have created a boom in amateur building projects including aircraft and boats.
Normal gelcoat formulated for use with polyester resins and vinylester resins does not adhere to epoxy surfaces, though epoxy adheres very well if applied to polyester resin surfaces. "Flocoat" that is normally used to coat the interior of polyester fibreglass yachts is also compatible with epoxies.
Epoxy materials tend to harden somewhat more gradually, while polyester materials tend to harden quickly, particularly if a lot of catalyst is used. The chemical reactions in both cases are exothermic. Large quantities of mix will generate their own heat and greatly speed the reaction, so it is usual to mix small amounts which can be used quickly.
While it is common to associate polyester resins and epoxy resins, their properties are sufficiently different that they are properly treated as distinct materials. Polyester resins are typically low strength unless used with a reinforcing material like glass fibre, are relatively brittle unless reinforced, and have low adhesion. Epoxies, by contrast, are inherently strong, somewhat flexible and have excellent adhesion. However, polyester resins are much cheaper.
Epoxy resins typically require a precise mix of two components which form a third chemical. Depending on the properties required, the ratio may be anything from 1:1 or over 10:1, but in every case they must be mixed in exactly the right proportions, and thoroughly to avoid unmixed portions. The final product is then a precise thermo-setting plastic. Until they are mixed the two elements are relatively inert, although the 'hardeners' tend to be more chemically active and should be protected from the atmosphere and moisture. The rate of the reaction can be changed by using different hardeners, which may change the nature of the final product, or by controlling the temperature.
By contrast, polyester resins are usually made available in a 'promoted' form, such that the progress of previously-mixed resins from liquid to solid is already underway, albeit very slowly. The only variable available to the user is to change the rate of this process using a catalyst, often Methyl-Ethyl-Ketone-Peroxide (MEKP), which is very toxic. The presence of the catalyst in the final product actually detracts from the desirable properties; just enough catalyst to harden fast enough is preferable. The rate of cure of polyesters is controlled by the amount and type of catalyst, and the temperature.
As adhesives, epoxies bond in three ways: a) mechanically, because the bonding surfaces are roughened; b) by proximity, because the cured resins are physically so close to the bonding surfaces that they are hard to separate; c) ionically, because the epoxy resins form ionic bonds at an atomic level with the bonding surfaces. This last is substantially the strongest of the three. By contrast, polyester resins can only bond using the first two of these, which greatly reduces their utility as adhesives and in marine repair.
Liquid epoxy resins
in their uncured state are mostly classed as irritant to the eyes and skin, as well as toxic to aquatic organisms. Solid epoxy resins are generally safer than liquid epoxy resins, and many are classified non-hazardous materials. One particular risk associated with epoxy resins is sensitization. The risk has been shown to be more pronounced in epoxy resins containing low molecular weight epoxy diluents. Exposure to epoxy resins can, over time, induce an allergic reaction. Sensitization generally occurs due to repeated exposure (e.g. through poor working hygiene and/or lack of protective equipment) over a long period of time. Allergic reaction sometimes occurs at a time which is delayed several days from the exposure. Allergic reaction is often visible in the form of dermatitis, particularly in areas where the exposure has been highest (commonly hands and forearms). Epoxy use is a main source of occupational asthma among users of plastics. Bisphenol A, which is used to manufacture a common class of epoxy resins, is a known endocrine disruptor.
A passenger ship
is a merchant ship whose primary function is to carry passengers
. The category does not include cargo vessels
which have accommodations for limited numbers of passengers, such as the ubiquitous twelve-passenger freighters once common on the seas in which the transport of passengers is secondary to the carriage of freight. The type does however include many classes of ships designed to transport substantial numbers of passengers as well as freight. Indeed, until recently virtually all ocean liners were able to transport mail, package freight and express, and other cargo in addition to passenger luggage, and were equipped with cargo holds and derricks, kingposts, or other cargo-handling gear for that purpose. Only in more recent ocean liners and in virtually all cruise ships has this cargo capacity been eliminated.
While typically passenger ships are part of the merchant marine, passenger ships have also been used as troopships and often are commissioned as naval ships when used as for that purpose.
Passenger ships include ferries, which are vessels for day or overnight short-sea trips moving passengers and vehicles (whether road or rail); ocean liners, which typically are passenger or passenger-cargo vessels transporting passengers and often cargo on longer line voyages
; and cruise ships, which often transport passengers on round-trips, in which the trip itself and the attractions of the ship and ports visited are the principal draw.
An ocean liner is the traditional form of passenger ship. Once such liners operated on scheduled line voyages to all inhabited parts of the world. With the advent of airliners transporting passengers and specialized cargo vessels hauling freight, line voyages have almost died out. But with their decline came an increase in sea trips for pleasure, and in the latter part of the 20th century ocean liners gave way to cruise ships as the predominant form of large passenger ship, with the main area of activity changing from the North Atlantic Ocean to the Caribbean Sea.
Although some ships have characteristics of both types, the design priorities of the two forms are different: ocean liners value speed and traditional luxury while cruise ships value amenities (swimming pools, theaters, ball rooms, casinos, sports facilities, etc.) rather than speed. These priorities produce different designs. In addition, ocean liners typically were built to cross the Atlantic Ocean between Europe and the United States or travel even further to South America or Asia while cruise ships typically serve shorter routes with more stops along coastlines or among various islands.
For a long time, cruise ships were smaller than the old ocean liners had been, but in the 1980s, this changed when Knut Kloster, the director of Norwegian Caribbean Lines, bought one of the biggest surviving liners, the SS France, and transformed her into a huge cruise ship, which he renamed the SS Norway. Her success demonstrated that there was a market for large cruise ships. Successive classes of ever-larger ships were ordered, until the Cunard liner Queen Elizabeth was finally dethroned from her 56-year reign as the largest passenger ship ever built (a dethronement that led to numerous further dethronements from the same position).
Both the RMS Queen Elizabeth 2 (QE2) (1969) and her successor as Cunard's flagship RMS Queen Mary 2 (QM2), which entered service in 2004, are of hybrid construction. Like transatlantic ocean liners, they are fast ships and strongly built to withstand the rigors of the North Atlantic in line voyage service, but both ships are also designed to operate as cruise ships, with the amenities expected in that trade. QM2 was superseded by the Freedom of the Seas of the Royal Caribbean line as the largest passenger ship ever built; however, QM2 still hold the record for the largest ocean liner. The Freedom of the Seas was superseded by the Oasis of the Seas in October 2009.
By convention and long usage, the size of civilian passenger ships is measured by gross tonnage, which is a dimensionless figure calculated from the total enclosed volume of the vessel. Gross tonnage is not a measure of weight, although the two concepts are often confused. Weight is measured by displacement, which is the conventional means of measuring naval vessels. Often a passenger ship is stated to "weigh" or "displace" a certain "tonnage", but the figure given nearly always refers to gross tonnage, which in this context has nothing to do with weight.
While a high displacement can indicate better sea keeping abilities, gross tonnage is promoted as the most important measure of size for passengers, as the ratio of gross tonnage per passenger – the Passenger/Space Ratio – gives a sense of the spaciousness of a ship, an important consideration in cruise liners where the onboard amenities are of high importance.
Gross tonnage normally is a much higher value than displacement. This was not always the case; as the functions, engineering and architecture of ships have changed, the gross tonnage figures of the largest passenger ships have risen substantially, while the displacements of such ships have not. RMS Titanic, with a gross register tonnage of 46,329 GRT, but a displacement reported at over 52,000 tons, was heavier than contemporary 100,000 – 110,000 GT cruise ships which displace only around 50,000 tons. Similarly, the Cunard Line's RMS Queen Mary and RMS Queen Elizabeth, of approximately 81,000 – 83,000 GT, but displacements of over 80,000 tons, do not differ significantly in displacement from their new 148,528 GT successor, RMS Queen Mary 2, which has been estimated to displace approximately 76,000 tons With the completion in 2009 of Oasis of the Seas, the first of the Oasis Class ships, the Cunard Queens of the 1930s have clearly been passed in displacement, as the Oasis vessels were projected to displace about 100,000 tons.
However, by the conventional and historical measure of gross tonnage, there has been a recent dramatic increase in the size of the largest new ships. The Oasis of the Seas measures over 225,000 GT, over twice as large as the largest cruise ships of the late 1990s.
are subject to two major International Maritime Organization requirements : to perform musters of the passengers (...) within 24 hours after their embarkation and to be able to perform full abandonment within a period of 30 minutes from the time the abandon-ship signal is given.
Passengers on ships without backup generators suffer substantial distress due to lack of water, refrigeration, and sewage systems in the event of loss of the main engines or generators due to fire or other emergency. Power is also unavailable to the crew of the ship to operate electrically powered mechanisms. Lack of an adequate backup system to propel the ship can, in rough seas, render it dead in the water and result in loss of the ship. The 2006 Revised Passenger Ship Safety Standards address these issues, and others, requiring that ships ordered after July, 2010 conform to safe return to port regulations; however, as of 2013 many ships remain in service which lack this capacity.
After October 1, 2010, the International Convention for the Safety of Life at Sea (SOLAS) requires passenger ships operating in international waters must either be constructed or upgraded to exclude combustible materials. It is believed some owners and operators of ships built before 1980, which are required to upgrade or retire their vessels, will be unable to conform to the regulations. Fred Olsen's Black Prince, built in 1966 was one such ship, but was reported to be headed for inter-island service in Venezuelan waters.
off shore repairs
fiberglass passenger boats
custom design yachts
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