The NACA foil formula results in a foil with a blunt edge instead of a point, so that the point can be made of something that's not wood (i.e., whatever resin one is using). That way there's less chance of the edge breaking, and water getting into the wood. Here's how I did it (John's idea):
Clamped a straight-edge to one side of the trailing edge of the foil, and filled in the triangle with resin thickened with chopped strand and cab-o-sil. Put packing tape on the straight-edge for easy release, as resin doesn't stick to it.
After the triangle is hard, the fibreglass goes on and overlaps the resin. Then one has a blade with a pointed glass trailing edge that the water will just slide off of:
The rudder is almost done. (I think I said that before.) The top groove is glassed, and the blade is glassed. Just need to (wait until Monday for the shop to be open and) glass the upper part, drill the pivot hole, attach the lines, and put the rudder back together again.
Didn't quite know how to treat the change from the point to the rounded after edge. It'll be whatever it comes out as. Notice that I've drilled and filled a large hole for the pivot bolt, so the final bolt hole will be isolated from the wood.
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