Paul,

This is a very elegant solution, IMO. I'm trying to think of ways to integrate this with the virtually indestructable, lightweight, and very easy to make PVC cross sections I played around with on my failed PVC walrus. Here's a possibility:

Picture your stringer method joined to my PVC cross sections with a 1" wide section of the 1" PVC. This would be cut along one side to make a "C" shape with a narrow opening, and is fastened to the cross section with a bolt/PVC glue/fiberglass/epoxy or some such at a 90* angle. Then you could snap your stringer into the "C" which holds it securely to the PVC rib.

I've also been playing with the idea of rehabilitating the other good idea I used on that boat - the I-beam. I think it could be done just as well with coroplast between two PVC stringers as it did with plywood. It would be an option to increase rigidity and save weight.

In the meantime, I'm progressing well on a Tom Yost folding baidarka made with HDPE cross sections and aluminum tubing stringers.

ad delirium,
Wayne