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  #1  
Old 07-04-2016, 12:38 AM
rdamazio's Avatar
rdamazio rdamazio is offline
 
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Location: Santa Clara, CA
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Default Minor wing drilling screwup

I made a minor mistake when drilling my skins and root ribs today. Plans call for nutplates along the root rib, and just one of them is the one-lug type:



but I got carried away and drilled the screw hole in that one just like the others:



How much trouble am I in?
It seems these nutplates are used in 44-6 for the "wing root fairing support" - can someone tell me if that comes pre-punched and how structural (if at all) that support is? (I don't have the fuselage kit yet)

I think my options are:
  1. put the two-lug nutplate (and have an offset from the original screw location) if the holes don't come pre-punched
  2. secure the one-lug nutplate with a single rivet, if that's not really structural
  3. add a backing piece of aluminum to hold the nutplate, which would require a fourth hole to hold it firmly.
  4. throw away the rib and skin and start over - not gonna happen

Thanks in advance
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Last edited by rdamazio : 07-05-2016 at 04:32 PM. Reason: Broken image
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  #2  
Old 07-04-2016, 07:43 AM
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If it were me, I'd do everything I can to put the #19 hole in the correct location, since the holes in the fairings are pre-punched. The fairing will cover that whole rivet line, so even if there is some kind of ugly kludge it won't be visible once everything is together. Once the screw is in place, everything will be sandwiched together anyway, so I can't possibly imagine a strength or structural problem.

I'd pursue your solution #3 and patch in a small strip underneath the problem area. Maybe use an AN470AD3-4(?) to fasten the nutplate to the strip at the "problem location" so the round head nests into the oops hole? Just an idea.

Build on Rodrigo!!
-Mike
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  #3  
Old 07-04-2016, 08:37 AM
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Carl Froehlich Carl Froehlich is offline
 
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Like Mike said - the #8 screw must be in the correct location.

You have choices to fill the now oversized hole, like doing a double flush AN426AD-5-3 or 5-4 rivet, and then having the nutplate mounted behind it on a piece of aluminum such that one end is riveted by the closest 3/32" rivet, and the other end extends down to the next 3/32" rivet. In other words the piece of aluminum that holds the nutplate would to be over the inside head of the double flush #5 rivet.

Carl
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  #4  
Old 07-04-2016, 08:59 AM
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flion flion is offline
 
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Kind of a cross between #2 and #3. Fill the hole you mis-drilled with strutural epoxy. I'd first drill the correct screw hole and install the 1-lug nutplate with a screw to hold it in position and a rivet in the good rivet hole. Then allow the epoxy to fill the mis-drilled hole and even ooze around the nutplate. Once the epoxy has set, carefully file it flush to the skin. Drilling and adding the second rivet is optional and really not called for if you allowed sufficient epoxy to secure the nutplate so it won't rotate, which is really the major job of the rivets here. Once the flushed side is primed/painted, no one (except all of us reading this thread ) will know you made an error.
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  #5  
Old 07-04-2016, 03:52 PM
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rdamazio rdamazio is offline
 
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Thanks for the replies, I'm going to drill the right hole in a few minutes (but not yet install the nutplate).

flion, I haven't used structural epoxy before, how is it different from regular epoxy? Just stronger? Any reference on when its use is appropriate so I don't try to use it for everything?
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  #6  
Old 07-05-2016, 09:13 AM
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flion flion is offline
 
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You can find it at AC Spruce. There are varieties, mostly intended for wood construction (handy if you are making the wood stiffeners for landing gear). I've had good luck with Loctite Hysol 615 Blue for strength with just a bit of flexibility (brittle epoxy tends to shatter and separate). Bonding to metal is always difficult so you will want to clean the bonding area well and provide some 'tooth' if possible. But in the situation you describe, allowing it to ooze through the hole and surround the lug of the platenut should provide plenty of mechanical strength. I've used this method to correct countersinks that were slightly deep and, yes, to correct a mis-drilled hole on my RV-10.
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