YACHT TYPES, ROUND BILGE / HARD CHINE:
Generally, we prefer round bilge yachts for their better looks and performance (no sharp corners to create turbulence). Metal hard chine hulls may be 15-25% cheaper than round bilge ones of the same material, however, since with a custom built yacht the hull represents only about 30% of the value of the complete boat, the hard chine saving is only approx. 5-8% of the overall value, but the resale value of the whole yacht may be reduced by 25 % or more, compared to the round bilge counterpart.
BOAT BUILDING MATERIALS:
Metal boats are the safest for serious long distance cruising, since unfortunately there is a lot of debris floating around, even lost containers. When you hit one of them with a GRP boat, you are in trouble. Hence, with solid GRP or Sandwich-constructed boats (see Speedstrip below), it is advisable to reinforce the inside (this is where the tension occurs) of the hull with Kevlar and/or provice watertight compartments, preferably at the bow.
SPEED STRIP SANDWICH CONSTRUCTION (see YACHTS / MIURA 31) :
The best and fastest results for amateur built yachts are achieved with Western Red Cedar Speed Strip construction, sheathed inside and outside with Epoxy/glass. Western Red Cedar is of a much higher quality than the usual Balsa core material, since it is highly rot-resistant and much stronger. Therefore the result is superior to ordinary Balsa or foam core sandwich hulls.
Very strong yachts up to 140 ft are professionally built this way. The manufacturers claim that with Speed Strip, two ecperienced workers can plank up a 40ft hull in just 4 days, but good amateurs should not take much longer since no special skills are required. As long as the strip ends are staggered over the hull, they do not even need to be scarfed but can be butt-joined where the hull is reasonably flat.
Another advantage of Speedstrip is the fact that the shape of the hull is in no way restricted by the building method, such as with hard chine or rounded hard chine hulls. Therefore, complicated hull shapes, such as clipper bows or wineglass transoms can be built by amateurs.
A great help for amateur builders are CAD - files for molds and bulkheads, which can be supplied by many designers. With these files, modern workshops can extremely accurately prefabricate these items for the builder, thereby avoiding all his previously required lofting, hand-tracing and -cutting.
The net result is a hull with a completely unscattered inside, where the CAM-cut bulkheads or completely prefabricated interior sections are easily fastened with thickened Epoxy (exact fit of the components is not even wanted), with Epoxy-fillets in both sides of the bulkheads, which makes the bonding extremely strong.
Speed Strip represents a significant step beyond the previous bead-and-cove concept. Each strip is tongue-and-groove in cross-section. The advantages offered by this system include: "snap-fit", which reduces the numer of fastenings; a reduced number of mold stations and frames; reduced glue squeeze-out; and improved overall fairness, both inside and out. The net-result, as claimed by the manufacturer, is a time saving in fairing and cleanup of 70% over earlier methods.
Aluminium nowadays is the most popular building material with custom built long distance cruisers. You can leave it unpainted. Claims about electrolysis problems with Aluminium hulls are mostly exagerated, however, this aspect should be observed and proper protection installed.
The following comparison will show the pros and cons of Aluminium versus steel:
- Weight: Aluminium is lighter than steel for the same strength. Hence the available displacement can be utilized for carrying water, equipment and provisions, rather than a heavy steel structure.
- More stable and faster: Due to their lighter weight, Aluminium boats have a lower centre of gravity and are therefore more stable and faster.
- Appearance: In order to keep the weight of steel hulls down, plating is thinner than with Aluminium yachts. Therefore, over the years, steel hulls will often acquire a buckled appearance, with reduced resale value.
- Labour saving: Light weight means labour saving during the construction of the hull. Also, Aluminium can be cut abt. 3x as fast as steel and it can be cut with normal woodworking equipment. Aluminium welds approc. 2x as fast as steel, even considering the thicker plating to be welded in the case of Aluminium construction.
- Safety: Aluminium deforms or stretches beyond its elastic limit more than steel before rupturing. This is of particular importance when hitting floating objects ( it is estimated that approximately 10 00 containers are going overboard annually ).
- Safety: Aluminium is non-sparking and non-magnetic.
- Price of material: Aluminium is more expensive than steel, however, it does not require a very elaborate paint system for corrosion protection and the resale value of Aluminium yachts is the highest of all boatbuilding materials.
COMBINATION ALUMINIUM / WOOD:
Aluminium hulls with wooden decks (inside: natural wooden deckbeams supporting a white painted plywood deck) combine the warmth of wood with the safety of Aluminium hulls. Furthermore, a lot of time is saved with this building method, since labouriously covering up deckbeams and stringers at the inside of an Aluminium deck can take the same time as building the deck in plywood accoring to the WEST (Wood Epoxy Saturation Technique) system.
Steel is the traditional material for metal boatbuilding. However, in spite of all claims that steel can be 100% corrosion protected, it still needs care and when you see a rusty spot on an exposed surface, you will have uneasy feelings about the hidden parts which will rust away undetected. Moreover, steel adds approx. 20% to the displacement as compared to Aluminium hulls, which could be better utilized by way of supplies. The resale value of steel boats is low