Help! Spar flange damage

[nichzimmerman]

It's quite nice when someone volunteers to help in the shop, especially when it comes time to dimple and deburr the wing assembly. Little did I know how the many ways that could go very wrong.

In a few places on the rear spar, the yoke of the squeezer caught on a protruding rivet or substructure and caused the squeezer's dimpler to pull into the aluminum without the opposing force of the dimple die. My volunteer did this several times before mentioning it to me, and the damage ranges from minor dents to significant gouges to a complete tear of the aluminum at the root end. I (barely) managed to keep my cool, but now I have a lot more work to do before skinning these wings. Ideas to make these parts airworthy? Thanks in advance.

- Nic
4-place plans #1217

tear.png
tear2.pngtear3.png

[Peter Girard]

doubler 2024t.3 0.40

[whee]

That really really sucks. My initial thought was a simple flat doubler on the flange but I don't see how you could get one in there that will do any good. You need to rivet the doubler to the flange on both sides of the tear and that isn't possible here.

Options I see:

1) Drill stop the tear and clean it as much as possible. Massage the dents out of the flange. Dimple and move on. Add the tear location to your annual checklist. (I don't know if I could accept this or not. It would forever be in the back of my mind). Maybe using a structural adhesive to bond a doubler to the flange would put ones mind at ease.

2) Disassemble the spar enough to properly install an 'L' shaped doubler that sits inside the 'U' of the spar. Of course you'll still need to drill stop and clean the tear and remove the dents from the flange. This would be the option I would chose.

2)New Spar...

[Chris In Milwaukee]

I'm no A&P, so this is just my opinion. But that's at the attach end of the wing, and I doubt it has any structural affect at that point other than a place to attach the skin. I lean towards Whee's option #1. Drill stop the tear and massage the dents out of the flange. Add a little Peter Girard action in there with an .040" L-shaped doubler on the back side if you desire. Drill out those three wing attach bracket rivets in your third photo, fit the doubler, rivet it all together.

2018-12-20_10-24-52.jpg

[stinger]

Nic , To me you're making a mountain out of a mole hill! . Straighten the area and install a doubler on the inside only, re-drill and dimple with a nail dimpler or vice-dimpler. you are on the root end, no big deal plus you will have a gap seal over most of it. the repair will be plenty strong. Good Luck Stinger.

[whee]

I'm no A&P, so this is just my opinion. But that's at the attach end of the wing, and I doubt it has little structural affect at that point other than a place to attach the skin. I lean towards Whee's option #1. Drill stop the tear and massage the dents out of the flange. Add a little Peter Girard action in there with an .040" L-shaped doubler on the back side if you desire. Drill out those three wing attach bracket rivets in your third photo, fit the doubler, rivet it all together.

Yes. This is what I would do. I also agree with his assessment of the structural affect. Placing the doubler as he described would remove any load from the tear and would put my mind at ease. I'm sure this is what Peter meant also.

[Archer39J]

Agreed, drill stop hole, flatten dents as best you can, doubler if you really feel like it. A call to Bob couldn't hurt to get his take, but it looks pretty minor.

[nichzimmerman]

Thanks for the encouragement all. I probably let my emotions get the better of me as these wings have been a work in progress for 8 years now. After considering the load paths, I agree it's not a high stress area.

After measuring, I don't think I can rivet an angled doubler to the spar plate because the bend radius must be too large to flatten out before the holes in the spar flange, and I really don't like the idea of drilling out those -5 AD rivets and replacing them now that the wing is assembled. Unless anyone has significant reservations, I will stop-drill the crack, flatten out the dents, smooth out the small gouges in the -5 rivet shop heads, and put in a flat .040 doubler that spans a few good rivets and move on.

[BravoGolf]

A moment of reflection is always good before getting into repair work. The flange that was bent, maybe cracked, does not carry any load except for the skin attachment. So slowly reshaping that area slowly would probably correct the bends. A hand flanging tool would work great. The issue that remains is to determine if there is sufficient edge distance between the drilled crack and that first rivet. I am not sure you need to place an angled doubler in that location. If there is insufficient edge distance placing a doubler on that flange would provide the edge distance required.

I agree with your assessment of the AN5- rivets. If any of them are cracked you may very well need to drill them out. But the potential of damaging that area or creating an over-sized hole is just as great as getting a nice sized hole.

[fairchild]

I would say drill out those bad rivets. DONT get in a hurry. Spring punch the dimples first to establish a good well centered place to pilot drill. Sometimes the rivet set will move the material in the
head around laterally ----so visually try to get the spring punch divet centered over the head. Use the usual technique-- drill down even with sheet surface up to just below shank size. Insert
punch into hole--- rock punch and head will pop off. Punch out shank using heavy back up behind rivet area.

Should be able to carefully massage out the dents. The tear is the nastiest problem ------ Maybe this is too drastic--- could that last part be simply cut away and the cut line kind of
angled up as it goes up to the bend line--- that is just amputate the cracked area ? That would seem to mean that the skin would be missing 1 rivet there..... I think I would rather
sacrifice 1 skin rivet than have a crack in the spar flange hiding and waiting to propagate up inside the layers where it later couldn't be seen. Bob might have the most wisdom on this
I bet ----- since he is the Momma of the thing----

PS--- Im thinking -- NOBODY will be touching my spars-- not even an A+P IA.....
I am also thinking that when it comes time to flush rivet all that skin on--- Id rather not even have a helper.
I made a tool once to be a robot bucking bar. May try to do that again. But thats down the road a ways.
The spars are maybe a couple months off though.

T

[way_up_north]

I`m just repeating what ive read on the yahoo list....a builder contacted Bob about about the wing metal weld mount where this part attaches. Bob commented that the forces on this joint are pushing towards the fuselage and downward. so this part feels mostly compression forces...if this makes you feel better