Working without a kit- it would be fairly easy to make a jig to cut interlocking puzzle-type scarfs in plywood like kits use. There can be advantages over a through-the-thickness scarf. In a through-the-thickness scarf there is much more surface area for gluing, but this also makes an area stiffer than the surrounding plywood, so it is easy to have an unfair curve. In a puzzle scarf the glue area is greatly increased over a butt joint, but it is nowhere near as great as a through-the-thickness scarf. On the other hand, it will not introduce any unfair curves.

Obviously, a CNC router can cut a puzzle scarf, and having it cut in this manner will greatly increase the ease and accuracy of construction for a home builder buying a kit. This is probably the point of a joint like that. In the case of either type of joint, the scarf will be covered by fiberglass. So how critical is strength? How strong is strong enough? How critical is joint flexibility? Has anyone had a joint failure or fiberglass stress (turn white) at a puzzle joint? Is anyone with a puzzle joint subjecting their kayak to high stress paddling like surf and rock gardens with plenty of wipe-outs?

Inquiring minds want to know.

m