> If you want a lighter boat, I built a similar design (11' X 20")with
> 1/8" plywood, but added a layer of 6oz glass on the bottom,
> overlapping the chine. It has plenty of strength; a 160# man paddled it
> and, for the ultimate toughness test, the kids play in it on the lawn. I
> think it weighs about 20#, so the kids can help carry it to the water and
> such.

There probably wasn't a lot of availablity of 1/8th inch plywood when this plan was first published about 40 years ago. I suspect that 1/4 inch material was specified for it's convenience and availabilty. The basic frame would probably be strong enough to work with just a fabric skin on it, so using 1/8 inch ply would probably work just fine -- even without covering it with glass cloth and resin. And, yes, you would save some weight on it -- but it is not a particularly heavy boat in the first place, so why bother?

PGJ