Hello mark36ph,

The fact that you are asking that question makes me assume that you do not have a table saw to trim at 45 degrees.

The only other reliable method is to use a hand held wood plane and if you do not have one I would encourage your to buy a small one. They are roughly 6 inches long.

It can be done wth sandpaper glued on a long flat straight piece of wood about 8 to 12 inches long and a couple of inches wide but it is not recommended. It is much sanding and lots of wood dust.

If your Robarts hinges are the 1/8" dia size you can locate the rotation axis 1/16" below the top wing surface and make notches to eliminate any gap between the spars (aileron spar of the wing and front spar of the ailerons).

Regards from Zor