Wing skin dimple damage

[Bearhawk024]

Hey guys. On the project I purchased, one of the dimples appears to have been done a little to hard and caused a small crack, which the original builder tried to drill out. Of course it is one of the top wing skins, and of course it's already mostly riveted in place, and of course this particular rivet dimple is to attach the skin to the rear spar. I would like to avoid removing the entire skin (lots of rivets to drill out), so I've been reading Aviation Maintenance Technician Handbook—Airframe from the FAA website which shows methods for repair. Two methods I'm considering are adding a doubler, vs cutting out the damaged dimple and patching with a doubler. To complicate things, this dimple is also right next to a rib. I miss the days when I could email a DAR (like Joe Norris) at EAA and they could tell me what they would like to see on inspection. Any advise would be appreciated.

[cub builder]

That's a tough one to decide how to treat. If you want perfection, you replace the panel. If you want functionality, you add a doubler. If you want symmetry, you add a doubler to the same place on the other wing. If you are really creative, you find something you need to mount over top of that spot (gopro mount, stall fence, GPS antenna mount, etc) so you can pretend the doubler is there to support whatever you're gonna mount there. Good luck with the repair.

-Cub Builder

[planecrazzzy]

Seems to me a TIG Aluminum Spot weld would be easy...

Or... since you've drilled it... stopping the crack from traveling...

"Bondo" is a very good choice... it flexes , Bonds to Aluminum very good...

Your only using a tiny dab... It's a better choice than 5 min epoxy...

Just give it a slight dimple... and make sure a little pushes thru the hole...

I've even fixed Car and Heavy Equipment RADIATORS with Bondo...
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YMMV..... Just "MI TOO SENSE"
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Gotta Fly...
JAM
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Buttercup - STOL - Aircraft
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"Buttercup" Building Log

Buttercup in EAA Article



Sometimes you just have to take the leap and build your wings on the way down...

[Dana]

2024 should never be welded! Even if you did succeed, the welded area would be susceptible to stress corrosion cracking, and it'd destroy the heat treat in the affected area.

The less said about bondo on an aircraft, the better...

If it was my plane, it'd get a doubler.

[cub builder]

And this is why AC 43.13 exists and is readily available to purchase in book form or can be readily accessed or downloaded by anyone with an internet connection.

-Cub Builder

[Bearhawk024]

Seems to me a TIG Aluminum Spot weld would be easy...

Or... since you've drilled it... stopping the crack from traveling...

"Bondo" is a very good choice... it flexes , Bonds to Aluminum very good...

Your only using a tiny dab... It's a better choice than 5 min epoxy...

Just give it a slight dimple... and make sure a little pushes thru the hole...

I've even fixed Car and Heavy Equipment RADIATORS with Bondo...
.
.
YMMV..... Just "MI TOO SENSE"
.
.
Gotta Fly...
JAM
.
.

Buttercup - STOL - Aircraft
.
"Buttercup" Building Log

Buttercup in EAA Article



Sometimes you just have to take the leap and build your wings on the way down...

Bearhawks are made with 2024, and it can't/shouldn't be welded. It falls apart even at brazing temps, which I found out after duplicating the damage in a piece of scrap and tried to fill it with aluminum brazing rod.

[Bearhawk024]

I'm tending to lean toward a doubler because replacing the panel would be a huge setback in terms of the amount of rivets that would need to be drilled out. I'm also concerned that with the number of rivets that would need to be drilled, there is an additional risk of damaging the structure further when drilling the rivets out.

[Bob H]

If the original hole has a crack or rough sites to initiate one, then normal skin loads will extend the crack. By applying a doubler, the intention is to reduce the skin loads/stresses thru the doubler and keep the underlying cracked skin from degrading by crack extension. I would smooth out the damaged hole(s) to remove existing crack sites and bond on a doubler with a structural adhesive. The doubler bonding will provide a greater contact area than a riveted doubler and will reduce skin stresses to keep the main skin from crack propogation. Do not use a 5 min epoxy but rather a good Hysol structural adhesive for peel resistance and shear strength. Surface prep is critical to a good bond so sanding with 120 grit and acetone wipe just before adhesive application is required.
Bob H

[Richard Warner]

Its on top of the wing, so really, more than likely won't be visible from ground level unless the person looking is a basketball player, if its on a Bearhawk or other high wing plane. It think the idea of a good structural adhesive, maybe combined with a few rivets would be the way to go. I agree with Bob H.

[ldmill]

I recognize that one - I did it myself. It's the result of having clecos in and resting the weight of the wing on the cleco's - then moving the wing around. It puts little smiley faces in the aluminum. I did the exact same thing to my Sonex/Waiex. I ended up with about 15 or so on my skin and in the end I just bought a new wing skin from Sonex. I didn't want to question it in the future.