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Fitting Wing Tabs

K

Keith Williams

Well Known Member
Have plane together, PAP mostly done, taxi tests done. Wing pins are in, wings solid (no play) but the pins are tighter than they should be. The wing skins are clear.

Left wing pins fit nicely. Right wing is the issue. At first, it would not go all the way in. Measured all four tabs and found that the aft tab on right wing was about .003 wider (taller?) than the others - trimmed it to match the others. All now 1.5002". Used a 1.5002" washer to check the four sockets. All were good at that dimension - no "play" with the washer. But right wing would still not go quite all the way in. Then did some very light trimming of the ends of the right wing tabs to get to the present situation (wings go on but tight pins).

Called Van's. They told me to just keep trimming and fitting until wing pins go in easily. I want to figure out which tab to trim. I do not want to trim from the tab that is already OK and wind up with pins that go in easily but some fore and aft play in the installed wing.

Wondering what others have done to identify the offending tab.
 
An old machinist's trick is to use layout blueing dye (Dyecom Blue sp?) To paint the ends of the fore and aft spars. Put the wing in position and wiggle the end up and down a little and pull the wing off to check the spars. It will wear the coloring off where it is touching. You should be able to see which spar is "offending".

In a pinch a blue magic marker will work also. ;)
 
Keith, my advice would be to very CAREFULLY smooth down the spar stub ends that go into the spar recptacles. If you take off too much you'll end up with fore/aft play in the wings.

That's a fixable situation by ordering oversize spar stubs from Van's, but it will set your schedule back some because you'll have to drill out the stub rivets and rivet on the new oversize spar stubs.

When you say the right wing pin will go in but is very tight, I assume you mean the spar pin, not the stub. If this is the case just trim the right rear stub ever so little at a time until the spar pin goes in - I use lubriplate on
my spar pins and tap them with a rubber hammer while my wife wiggles the wing.

Walt Shipley
 
Fitting Wings

Walt and Larry - yes, it is the spar pin that is tight. I expect either the fore or aft tab is too long. I will use the dye to identify the offender, trim it "ever so little at a time", and try Lubriplate on the pins. Thanks for the input. This should do it.

I was surprised when I came to appreciate the tolerances involved here - maybe should not have been but I surely was.
 
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