On Sun, 9 Mar 2008 07:43:23 -0400, "Roger Long"
wrote:

Aluminum is not theoretically as strong but aluminum
boats tend to deform and stay watertight in accidents where steel will
fracture.

For equal weight Al and steel are equal in strength. Considering
weldability and panal stiffness aluminum is better because it is
thicker. Note that the alloys used for boatbuilding are not the
strongest available in either material. In the case of aluminum, the
usual alloys do not need paint, Every fifty year old al boat I know
has been out in the weather without paint and no sign of corrosion.
Most aluminum commercial boats, for example Alaskan fishing boats are
left unpainted in salt water and don't corrode. My 22 foot cuddy is
bare Al, and I wouldn't consider any other material.

You are correct about the fact that steel will tear in cases where
aluminum will just get a big dent. Think shipping container. 10 000 a
year get washed off the boxboats,

Casady