: Here is a link of interest.

There are aircraft foams that might work for a foam cored kayak. There are PVC foams that are very thin and are heat formable and quite light as well as damage resistant. Downsides are you have to cover both sides with glass which like a wood strip boat and you generally spend a fair amount of time getting the foam flat enough to glass. Also the foam isn't cheap. I'd recommend looking at Aircraft Spruce as a supplier as most commercial dealers will only sell per case. Looking at 1/8" Divinycell foam it's $18.50 for a piece 32" x 48".

I've done, or at least helped, building a couple large boats using this process and while it works and results in a fairly light boat it's also quite a lot of work and can be really messy to work with. The dust from sanding this stuff gets everywhere and is nearly impossible to clean up. Unlike a wood core (stripper) the foam isn't as stiff and requires a much heavier glass skins (on both sides) for reasonable damage resistance. Still, there have been foam cored kayaks built that are very light.

Bill H.