Jon,
My wing joints have a very small gap in the 'sandwich' built up for these fittings. I read in some instructions I had that a small (.010 - .015" ?) shim is used in front of the 315 at bottom, and behind it at top. The idea was to guarantee a very small clearance for pitch rotation around the rear support tube as you separate. Can't say it really works that way or not; my wings are still kind of tight.
What seems to be most significant in my case is matching the dimension between front and rear spars. If that's not right, it won't matter much about the fittings anyway. To be honest, it wouldn't bother me terribly to have an 'easy' slip fit for the 315 and 215 fittings. Here's what really matters to me the most for that joint: Match drill the holes for the two pins and be certain the pins fit very snug. I reamed mine after the heat treatment of the fittings to account for dimensional changes. I again built up the sandwich to 'match ream' with 215 & 315 fittings, spacers, and shims as described above. This was before spar assembly. I tried to attach an image, but you can always look at my photo album. Getting the dihedral angle right between spars was also easier to do afterward. When going to attach these fittings to spars I laid out the spars which because of size are easier to measure. Ask around how much wobble (induced by the pins) that you can feel up and down on various projects at the wing tips. I think most guys would agree about 1/8" maximum. Hope this helps.
Les Krumel,
Albuquerque
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