Patching up the wing on the RV-4

Each year we experimental aircraft owners have to put our aircraft through what’s called an annual condition inspection.  Those of us who built our own airplanes are authorized by the FAA to perform the inspection ourselves.  During my last annual, I found some cracking on the top wing skin running along the line of rivets that connect the top skin to the rear wing spar.  The cracking came from careless feet not stepping directly on the reinforced portion of the wing.

This week I finally got around to repairing that crack.  It was only 3 inches long but I ended up drilling out about 2 feet of top wing skin.  That equates to about 200 rivets to drill out!  I had the week off and my wife and kids are vacationing so it was the perfect time to attack the wing.  I spent Tuesday, drilling out all the rivets.  Wednesday was spent fabricating the new top skin a doubler plate (which goes under the skin to give it support).  Thursday I match-drilled the holes in the new skin and reinforcing plate using the old skin as a template.  I also trimmed the plate and the skin to fit the wing.  Friday (today) was spent riveting the wing skin on.  I wasn’t able to completely rivet the skin on however.  I used regular driven rivets where the new wing skin / old wing skin overlap joint is.  I then used pulled rivets (Cherry Max structural rivets) to fasten the skin to the front spar and ribs.  I have to use pulled rivets because I can’t get a bucking bar under the wing skin in most places to drive rivets.  The Cherry Max rivets look fine and are just as strong as regular rivets.

The only reason I wasn’t able to finish today is because I ran out of Cherry Max rivets.  More are on the way and when they arrive I’ll be able to finish that wing off.  There are just a few more things to do to adjust the skin where it meets the flaps and then I’ll be done!  Just one of the many joys of aircraft ownership. 🙂

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