The problem is this. In order to have an aluminum boat that compares in weight to a plywood boat you must use aluminum that is fairly thin. Unfortunately, aluminum of the appropriate thickness does not have the stiffness of plywood. If you look at commercially available aluminum recreational boats you will notice they are made from stampings. The stamped panels can be curved in all three axis which stiffens the panel greatly.

: Hi there, as I always suffer deeply when launching and scratching
: my kayak I started wondering wether an aluminium S&G would be
: possible? Volume to weight ratio depending on thickness? Does
: anybody have come across this question? Regards and happy
: paddling from Bonn germany.