Aluminum Hulls

Pros and cons of building with this strong, light metal
Aluminum has been used for the hulls of small boats ever since the power yacht Alumina was built in Switzerland for Prince Wilhelm zu Wied in 1894. This light metal is refined from the mineral bauxite. Although it was discovered early in the nineteenth century, it wasn’t until 1886 that the first practical refining methods were developed in France.Today, aluminum is used to build sailboats and power yachts of all sizes, and it is especially suited to high-speed planing powerboats where weight is all-important.One of its major characteristics, in addition to its light weight, is its ductility; that is, its ability to stretch without breaking. That means it can be deformed in a collision with a half-submerged container or when grounding on rocks without being holed—as a hull made of fiberglass or wood might be.It is also strong, stiff, and—in the right alloys—resistant to corrosion. You don’t need to paint an aluminum hull, except for cosmetic purposes.On the other hand, an aluminum hull costs more to build. The metal is hot in summer and cold in winter. It readily transmits wave noise to the interior and it needs insulation in cold waters to prevent condensation. Aluminum is less forgiving of sloppy welding technique than steel, though easier to weld now than formerly. It is otherwise easy to work. For many cutting and fitting operations, hand tools suffice.Aluminum is low on the galvanic scale—close to zinc, in fact—thus, it is particularly vulnerable to galvanic corrosion, a process by which it is eaten away by more “noble” metals. A copper coin left in the bilge of an aluminum boat and covered with salt water will eventually eat its way through the hull.Special through-hull fittings are needed for aluminum hulls, as is special antifouling paint, because the typical copper-based paint would react with the hull metal.See also Galvanic Corrosion; Steel Hulls; Wooden Hulls.