Tom Jordin's Spline Joint
A friend of mine, Tom Jordin, has developed a process to make light, strong butt joints in 4 mm plywood. This is really about a cosmetic issue. His procedure avoids the color banding problems typical to the Pygmy joint taping process. Below are the highlights on how to go about this. Doing it the Pygmy way will result in nice strong boat and most people never notice the color banding that results. Some people go an extra step and sand off the outside tape once the boat is assembled. But sanding can cause light or dark areas unless all of the surfaces are sanded in an identical manner. This is not easy to do.
(Thumbnails have links to larger pictures in a separate window)
The cut is made using a small diameter thin kerf blade mounted on a shaper table. Not everyone has such a tool. Perhaps there are alternatives, like using a slot cutting head on a table mounted router.
Make a jig to hold panel as it slides by saw blade.
Views of panel on the table.
Make cut slightly wider than 1/16 and slightly deeper than width of spline. Cut adjoining panels with matching sides facing the same direction so that an off-center cut does not mater.
The spline is made from 1/16 aircraft grade 3 layer plywood found at a hobby shop. Spline grain should run same direction as panel grain.
Make spline longer than width of panel and trim off excess once pieces are glued together. Outside area around the joint should probably be masked off to avoid epoxy squeeze out from discoloring the joint area.
Finished deck showing spline joined butt seams.