Wednesday, December 30, 2009

Trimming Wing Rib Gussets

The gussets on the wing ribs are mostly triangles and rectangles. They are glued on with the corners of the gussets sticking out past the curved upper and lower sticks.

In the factory photos you can see that they trimmed the corners of the gusset with a belt sander to create a smooth contour on the edges of the ribs. That actually works very well with soft glues like they used in the mid 1920s. Resorcinol is very hard once it cures and is not as easy to trim with the belt sander.

What really works well is a straight sided router bit with a roller bearing for trimming Formica.

You need a sole plate for the router with a very large radius on the edges so the gussets and any stray nail heads do not hang up on the edge. I made this one with a scrap of plywood and rounded the edges on the belt sander. I've lost my little table/router stand so I just clamp it in a work mate.

Adjust the height of the roller so it is near the top of the stick. This assures you get any glue which may have dripped down a stick. Also you need to rout each side of the rib once the gussets on that side are dry. Otherwise the roller will follow the gusset or glue from the first side or be adjusted so low it won't clean up all the glue.

Remember to rout in the spar openings as well. You'll need to touch up the inside corners with a mill file.

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