Be careful when drilling top wing skin inboard nutplate holes

I am waiting for word from Vans Support, but I think finally I made the mistake that is going to require some expensive re-ordering... Red arrow on the attached picture is the hole I drilled #19 by accident.

Veteran builders already know this, but building when you are tired and it is late at night is just begging for disaster.

Witness the mistake I made Friday night:



There is even a note which says to be careful drilling the middle nutplate screw hole. I believe what is going to attach to this is a fairing against the fuse and I assume that is fiberglass so I am unclear fixing this is going to work other than replacing skins, doublers, and the rib below.

The way I did this by the way, for the next person is that I had all the clecos in place and the way I had them in there made this look like it was just another cluster of three holes rather than a cluster of four holes. In other words the hole that was supposed to be drilled #19 had a cleco in it. I looked at it, and drilled the top most hole of the three that were exposed which was correct for a one leg nutplate. Only problem is that it is the top most hole of the FOUR holes not the three. So as you see in the diagram I am off by one hole. I really was on a roll before this, hopefully it is fixable in some other way, but I am at a loss as to how right now.

Jeff

If you cannot find a different nutplate that is longer so you can move the holes out farther into undrilled hole, just get someone to weld a tab to the one you have and extend it down to the next hole which is supposed to hold the skin to the rib. You could also enlarge the #19 hole and place a washer inplace of the skin and rivet the nutplate to the washer, sandwitching the rib. All these rivets are doing is holding the nutplate til you get the fairing screw in place, and will be hidden by that fairing. I'm sure you will come up with a solution other than new skins.
Ron

I agree with what Ron B has stated.

Thanks Guys.

Sterling over at Vans even went further and suggested that I just install the nutplate with a single rivet instead since as you mentioned the only purpose here is to hold this in place while the screw goes in and there are MANY other nutplates drilled correctly holding on the fairing. Phewww.... Back to paying more attention. Hopefully it helps someone avoid the same mistake.

That's a 'gotcha' on the RV-10 wings, as well. Since you're going to need to fill that hole anyway, here are a couple of approaches. First, tape the back of the hole and fill with epoxy (structural epoxy, liquid aluminum, etc.; just not some light filler) slightly more than full. Let cure, then file/sand flush with the top of the skin. When the nutplate is in place, you can back-drill, countersink, and install a rivet. There will be plenty of strength since, as is already mentioned, it is a shear application meant to keep the nutplate from rotating when a screw is not installed. Alternatively, you can install the nutplate and then fill with epoxy, being sure to let some ooze through the nutplate's unused rivet hole. The only advantage to using a rivet is to keep the patterns consistent if you are not over-filling at paint time and the rivets will show through. Either way, using some epoxy to help with the anti-rotation of the nutplate is, IMHO, better than just filling over the hole and letting a single rivet do all the work.

JDBoston said:

Thanks Guys.

Sterling over at Vans even went further and suggested that I just install the nutplate with a single rivet instead since as you mentioned the only purpose here is to hold this in place while the screw goes in and there are MANY other nutplates drilled correctly holding on the fairing. Phewww.... Back to paying more attention. Hopefully it helps someone avoid the same mistake.

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I agree with him, except that I wouldn't install it that way.
A nutplate installed with a single rivet will push away and bend when you put pressure on it to start the screw. Even the single leg nutplates can have this happen (which is why I only use them if I absolutely have to)
I personally would make a small doubler strip (.025 or .032 thick would be fine) to bridge the over sized hole.
Pre-rivet the one end of the nutplate to the hole associated with the one drilled over sized, then rivet the doubler in place with slightly longer rivets at the rest of the holes.