MATERIALS: ALUMINUM ALLOYS
Aluminum Alloys are a fine medium for the construction of all types of marine vessels. Being a metal, almost any vessel that can be built in steel can also be built in aluminum alloys. There are a few glaring exceptions such as a Dory, which depends on a heavy bottom for a large portion of her stability. The reverse is not true for vessels designed in aluminum because the lesser weight of aluminum alloys permits a lesser displacement for the same type of steel hull.
In practice, to achieve the same strength as steel, it is mandatory to increase the scantlings approximately 50%, thus 1/8” steel = 3/16” aluminum; framing is also proportionally greater in sectional area. While the theoretical difference in material weight of aluminum is 1/3 that of steel, in actual practice the difference in structural weight as built gives only about a 30% savings over the steel hull. This must not be translated directly as a reduction to displacement as the engine, fuel, water, all other equipment, and joiner work remain virtually the same. I was at one time the Consulting Naval Architect for Kaiser Aluminum Company and can cite hundreds of reasons for and benefits of choosing aluminum alloys. Unfortunately, it is not a trickle-down effect that has much meaning in small vessels. Instead I prefer to think about some of the benefits as well as the demerits of aluminum construction.