I built a CC 18 from 1/8" birch plywood I found at the lumber yard. I boiled a sample to make sure the glue was water resistant. For the hull, I laminated two plys with epoxy. The outer lamination was per CLC's drawings, and the inner ply about an inch smaller all around. I figured the fillet and glass tape in the seam would make up for the thinner edge. I covered the bottom with 6oz. glass cloth, overlapping the chine by an inch or so. For the deck I used just one thickness of 1/8" plywood. The hull is quite rigid, and the only failure so far is an above-the-waterline puncture (don't know how THAT got there). The boat weighs about 52# on my bathroom scale, with rudder, 1/4" ply bulkheads, and a foot pump.

All in all, I would stand the wait and expence and use marine plywood next time. All the extra bother is not worth the savings. Also, although my boat was coated with epoxy before finish, I wonder if I will have moisture problems someday. I made a kayak for my daughter of the same stuff, but without the epoxy coating, and am getting delamination.