John,

The dry bag material is probably a little heavier than #10 cotton duck 15 oz, coated with Elast-o-Seal and Snow-Roof. It is a lot heavier than the 9 oz polyester coated with Varathane. As far as stetchy vs. non-stretchy fabric the polyester (non-stretchy) was a little harder to work with than the cotton (stretchy), but it makes up for it every time I pick the kayak up. I keep forgetting how easy it is to load that 27 pound kayak on top of my truck.

I have heard of using PVC for the skin, but it does make a heavier kayak. You would also need to seal the fabric at the stems, this would require either heat sealing, or gluing.

As far as the plywood, are you thinking of using it like ribs in a traditional SOF, like a hollowed out form? It would work, but you will get a lot more flex in the frame. The truss cunstruction of the Walrus, stiffens those skinny stringers a lot. To compensate for that, you could use larger dimensions for the gunnels, like a traditional SOF.

Mike

: Bill,
: This material is just like dry bag material come to think of it. How much
: heavier is this compared to a skin and seperate sealing material you
: think?

: Thanks,
: -John
: I'd be leary