: Every butt joint I've seen pictures of have an overlapping piece of ply
: across the joint, which is not really possible in the V of the keel. I was
: just curious why this didn't seem to be such a big issue with the keel. I
: guess something like a shear clamp piece could be added along the keel
: seam also but I guess it is because of the water pressure against the hull
: which makes the difference between the keel and the shear chine.

No, in this case the water pressure is not great enough to cause the keel seam to be pressed together.

The sheer clamp is also called a sheer chine by some people, and like most chine pieces (also called chine logs) they are fitted into seams for reinforcement. In a few designs the deck is secured by using nails or screws to pull it onto the hull. These mechanical fasteners pull the deck material into contact with the sheer chine, and "clamp" it in place until the glue or sealant hardens.

A designer who calls for using a sheer clamp is trying to make it easier for a builder to attach the deck. If you did not want to use a sheer clamp, you could remove this piece of wood and secure the deck to the hull with wire ties, just as the hull panels were assembled. Of course then you would have to crawl inside the tight space of the kayak to create teh fillet, and put fiberglass tape or glass along the length of the seam. This can be a big hassle.

Some people make "hybrid" boats with hulls of plywood and decks from wood strips. These are called "hybrids" as they combine stitch and glue techniques with stripp building ones. People who make decks from strips generally do not attach those decks using sheer clamps.

Hope this helps

PGJ