In theory you can make Al hulls as light as GRP hulls as the two materials have similar specific stiffness (stiffness to weight). However in practice the aluminium does become very thin and so difficult to work with, i.e. weld and easier to dent. Also GRP is easy to work into a very efficient sandwich structure, Al is more difficult. Aluminium is more suited to boats that are larger than the average beach cat.

That said there are lots of new ways of forming Al so while you might not get a weight advantage you could have a significant cost advantage if you could sell enough of them!

Gareth
www.fourhulls.com