I am almost done with a carbon fiber framed Yost Sea Tour 15. Its taken me a year, not due to any difficulties, but because I kept stopping to work on other projects. The goal was to build an under-20 pound kayak that would be strong enough for the Chesapeake Bay and similar protected coastal waters and have a strong rip-resistant skin. With a few coats of varnish left to go, the kayak weighs 12 pounds, so I am very hopeful of meeting my goals.

Gunwales are 1/2 inch outer diameter pultruded carbon fiber tubing, all other stringers are 3/8 inch.
Frames are 3/8 inch plywood placed every foot. I wanted frames every foot to stiffen the structure and provide plenty of support for the carbon fiber. Offsets for the additional frames were calculated using a graphing program.
Frames for the front and the center of the cockpit were cut from 1/2 inch plywood, wrapped in carbon fiber fabric, and epoxied. The frame in the center of the cockpit is a half-frame, obviously.
Kevlar roving diagonals, as used in Geodesic Aerolite boats, were run between gunwales and chines to help hold the sheerline and further stiffen the structure. I am not convinced that these were necessary, but they weren't much trouble and can't do any harm.
All lashings were epoxied, as were the Kevlar diagonals where they wrapped around the frame-stringer joints.

The skin is 8 ounce nylon coated with G/flex epoxy. It will receive a few coats of Epifanes varnish before I'm done.
I still need to provide support for the cockpit coaming and then outfit with foam, floatbags, decklines, etc.

While this construction method is not suitable for expeditions, rock gardens, or surf landings, I think it will prove more than adequate for the kind of paddling my wife and I actually do. I'll report back after we've used it a while, or sooner if it suffers a catastrophic failure!

Pictures are provided here: http://www.flickr.com/photos/buyerj/sets/72157636300630926/

Jeff