Perpendicular Scarf Joints

[Ron Hotchin]

Can two pieces of 3/8" okoume plywood about 2 ft wide for the side of a boat be satisfactorily scarfed with epoxy if the grain of the surface layers are at 90 degrees to each other. Are there any structural concerns? The joint will be toward the stern, with only a small amount of curve. The outer sides will be epoxied with 6 oz fibreglass and painted, and the inside will be epoxy primed, then painted. I'm working out my cutting patterns, and if this is suitable, it will save a sheet of ply for two pieces about 2 ft x 2 ft.

[Tom Lathrop]

What you propose is often done when a stiffer panel is wanted by placing the long grain of the outer plywood layer transverse to the hull. Unless there is a lot of bend in the panel (not in your case), there is not likely to be a problem. The layer of glass eliminates that possibility anyway.

The joint may be weaker under bending stress but should be fine the way you are using it. I have not heard of tests which settled the issue.