General HULL TYPES - Pros/Cons?
Frankly I went with aluminum. I believe it''s the best choice for hulls.
Wood is rapidly disappearing as the number of highly skilled carpenters willing to work for relatively low wages declines, but modern incarnations such as West system cold-molded construction still have advantages where low weight and moderate cost are considered more important than ability to sail safely in the rougher parts of the World''s oceans, and take the knocks on coral, ice or granite that are inevitable in extensive cruising.
Fiberglass boats make extensive use of balsa wood or foam sandwiched between two layers of glass reinforced plastic. The structural engineer and the racing sailor, like the superior strength and stiffness to weight ratio attainable with this sandwich construction. However, if not very carefully built and maintained, the boat will have a short life, or require considerable maintenance, since water will find its way in between the laminations.
Poor workmanship when adding or replacing deck equipment after launching is a major cause of failures. It can be very expensive to do a good job or installing a new winch on the coachroof, or a sail track on the deck, if the necessary structural reinforcements were not foreseen when the glass was laid up.
If you want good fiberglass, then stick with a hull produced in reasonable quantities, so that the builder can minimize his mold costs, leaving enough money for good quality labor. Epoxy resins and vinyl-ester are normally best, and are used in the better hulls. As usual, the best is expensive. If you want the boat to last through extensive cruising, insist on foam in preference over balsa wood.
The negatives of ferro are high weight, and relatively low reserve strength in event of collision. It is not feasible to take advantage of modern hydrodynamics in ferro-cement, so performance suffers relative to the better modern cruising designs. Resale value is low, although this is attractive if you are a buyer.
The status value is ferro is rock bottom, and ferro is rarely seen around the exotic marinas.
Ferro must be insulated, and this can be accomplished easily with blown polyurethane foam. Exterior paint often falls off, but this can be avoided by using the right paints and painting the inside as well as the outside. This latter point cannot be overemphasized.
Ferro is most attractive to the amateur, and most ferro boats are amateur built. If buying one, the only effective quality control is to know the building technique well, or to buy a boat that has crossed oceans, and has NOT been recently painted.
The strength to weight ratio of aluminum is excellent, particularly when considering the ability to withstand accidental impact loads. Aluminum yachts are more resistant to grounding, collision and similar abuse than plastic, they are immune from osmotic blistering, they can be left unpainted if desired, and are extremely resistant to corrosion.
The old bugaboos of electrolytic corrosion are easily controlled with to-day''s know-how.
The correct grade of marine alloy is essential, with 5086 and 5083 being preferred by most experienced builders for the wetted parts. This alloy is not quite so strong as the 6000 series alloys normally used for masts, but is much more corrosion resistant.
Welding skills play a part in making the most of aluminum. Rigorous attention to preparation and the welding alloy used is essential, and it is easier to maintain quality in a shop that builds only aluminum structures for marine use than in a shop that also works with steel and other alloys.
A highly skilled yard can build aluminum hulls so fair that they can be left unpainted, except for antifouling. Apart from the aesthetics, this has the advantage of guaranteeing welds free of pin-holes which can lead to corrosion problems. If painted, a good aluminum hull will not require any filler, and the paint will last much longer than on a steel or wooden hull.
Since the metal is inherently resistant to sea water, the inside can be sprayed with two to four inches polyurethane foam; keeping the crew cool in the tropics, while keeping warm and eliminating condensation in cold waters.
Aluminum hulls are much stiffer than fiberglass or wood, so leaks at any bolted on fittings are much less likely than with fiberglass. The interior carpentry can be made to fit well without any problems from doors jamming or opening unexpectedly in a seaway.
The greatest advantage of steel is that it is very strong. However, as discussed by Michael Kasten, aluminum yachts are normaly somewhat more robust than steel ones in practice. Particularly in the first half dozen years of their life, steel yachts often have considerable reserves of strength because they are normally designed with a margin on the thickness of the metal to allow for expected corrosion.Cost will be similar to aluminum, for equal quality.
If well designed, with fabrication details well thought out to minimize corrosion, and if the paint is applied perfectly, corrosion is not uncontrollable in steel, although maintenance costs will normally exceed those for aluminum.
Virtually any hull form can be built without any compromise in strength. However, I have not yet seen any steel yachts that are so fair that they look good with paint only on the hull. Filling is required, and this is liable to have to be sandblasted off and redone every five to ten years.
Insulation is a problem. If uninsulated, a steel boat will run with condensation in the cold water, and cook the occupants in the tropics. If insulated, there will always be the worry of corrosion under the insulation.
Take your choice but all in all, I voted for aluminum.