Forgot to dimple for screws

[PIN 37]

So I have finally put the wings on my 7. I "thought" I had everything covered. Anyway, after the usual amount of sweat and tears all the bolts were in. I climbed underneath to put the screws in the skin that connects the fuse to the wing and I have forgotten to dimple the fuse skin, dumb I know, but is there any suggestions on a fix short of taking the wings off again, which I am not going to do. I did think of using pan head screw which I will do if I have to, but knowing there are a lot of smart people here I was wondering if there is a fix?

[Robin8er]

Ive never tried it, but why not just put a little oil on the screw and let it dimple itself by screwing it in?

[rockwoodrv9]

That is pretty thick skin down there. Maybe you could countersink it? I don't know enough about structural engineering on how much strength you lose with a countersink over a dimple so run it by Vans. In real life, you probably won't lose more than 10 knots using pan head screws there!!

My skin edge there is so dented from being banged up while building, I am going to have to take a body repair hammer and fix it up a bit. It is always something!! Good luck.

[rv7charlie]

I haven't put my wings on yet, but I've run into similar issues elsewhere.

Have you already mounted countersunk style plate nuts on the underlying skin? If so, I'd probably vote for the lube & screw technique mentioned. If it scares you, find a piece of scrap the same thickness, & do a practice run.

You can also form a dimple in place with a female die in a bucking bar, & the male die in a set for your rivet gun. Just start with very low pressure & work your way up until you're happy with the dimple. If the nut plate is already in place, you can make a 'custom' bucking bar to go over the back side of the nut plate. Just taper the outside, too, so you don't destroy the rivets holding the nut plate.

I'd be cautious about trying to countersink a skin for a #8 screw; I don't think there'll be much left to hold the head.

Charlie

[RV7A Flyer]

You've come an awful long way to mess things up now. I'd reconsider taking the wings off in order to do the job right, rather than risk messing something up that will a) look horrible, b) weaken some structure, and/or c) bug you every time you look at it because it's not as good as it could/should be.

Just my two cents. I'd take them off and do the job correctly, but I'm a perfectionist.

[PIN 37]

Hi Charlie, c/s nutplates are in place on the wing, however at that position on the aircraft there is very little gap between the fuse and the inboard rib, so bucking would be problematic though maybe not impossible. I agree countersinking is out of the question. I have tried the screw method on a piece of scrap .032 and it worked fine, just cant remember if that skin is 32 or 40 thou.

[rv7charlie]

I'll try to measure for you when I go down to the hangar in the morning. Do y'all have the equivalent of Harbor Freight Tools down under? You can get 'good enough' digital calipers for less than $20 US; often much less. Old style dial are often under $10.

But I seriously doubt it will be an issue, even if they're .040.

[MikeyDale]

I guess there is an advantage to putting the wings on and of three times!

[alpinelakespilot2000]

I would almost never voluntarily pull the wings off unless it was REALLY necessary. The close tolerance bolts are going to be a bear to get out. I would worry more about scarring of the spar holes or doing other damage than I would about a few low profile pan head screws that no one would ever see unless they get down on their hands and knees. They're not going to slow you down.

[BobTurner]

Can an assistant access the back side from inside the cockpit? If so, have him hold the female dimple die, backed by the heaviest bucking bar you have. Use a low pressure rivet gun to tap the male dimple die on the outside.