: I like your idea of building up a sharp edge ON TOP of the rounded,
: fiberglassed 90 degree joint. Clever, and obvious in hindsight.
: Not sure it needs to be overengineered beyond that.
: John

Simple as it looks, it probably IS overengineered.

1) The fillet may look cosmetic, but it can fill the gap for aerodynamic (or would that be hydrodynamic?) form.

2)The strength of the bond would be similar to the bond strength of a proper fillet of the same dimension. The base of that fillet has a relatively huge surface area in relation to the amount of weight or pressure applied to it. A fillet of the same size holds the boat's panels together--this one just fills a gap.

On second thought, someone could make it simpler still and replace it with a bead of caulk as shown in the illustration below. The idea would be to put a release layer (wax, grease, saran wrap, or tape) on one of the surfaces and have something to limit the depth of the bead of caulking material which is applied. That would keep you from putting in too much. The boat parts would be assembled, but not drawn together to full tightness, the caulk applied and smoothed with a wet finger or squeegee, then allowed to set. The boat would be disassembled and the release material cleaned off. The bead of caulk remains glued to the other part as a cast-on-place gasket. One could use a flexible silicone or urethane, or an inflexible caulk for this.

More ideas. Who'd have thought.

PGJ