S

Sig600

Well Known Member
Putting the aileron fairing in (RV-7), driled, deburred and dimpled everything, installed the rivets per the plans on the callouts, however this looks like **** and I can't figure out what I did wrong. None of my skin work has ever come out looking like this. I was hand squeezing them and didn't notice this until I was about 2/3 done with this row, and it REALLY didn't stand out until I looked at it this morning with some sunlight coming in.

333vhjb.jpg

1izgwx.jpg
 
Used the same ones on both pieces.... welded to a set of vice grips (from Avery). It had been a while since I did any dimpling too, so I practiced first on some scrap and it came out ok.
 
Good news

Looking at sheet metal stuctures using light from the side will reveal a multitude of sins. I think the fix is to back up the flush side using a 2x4 with a thin piece of white high density foam. Then hit the shop side with a large punch and bump it out (hand tools for control).
It looks like what happened is this:
1.The flange on the fairing is not 90 degrees, so the supprt is not pependicular to the force to install rivets.
2.To much force to drive rivets, or not enough mass/momentum in the bar to keep the skin from straining. Stress the skin, strain the rivits. A balance between force holding the gun against the skin, air pressure, bar mass, and how much you let the bar bounce (momentum).
Go slow, I think it will dress out O.K.
Good luck.
 
Thanks Andrew, I'll see if that works out. I used a hand squeezer on everything for just that reason (control).

Part of the problem is the flange isn't quite the right width to cover the distance between the skin and the spar, so when I cleco'd the bottom portion to the spar, it really pulled down on everything and pulled the trailing edge of the skin tight.

I'm also thinking I may not have been aggressive enough on the dimples. i.e. I didn't squeeze them terribly hard to get a nice sharp depression. Figured this out when I went back and tried to figure out what I did wrong redoing a few pieces of scrap with varying degree's of "squeeze" with the dimpler.

I'll see if I can tap them flush, I don't want the shop heads to pound too flat though.

Is this something that can be rectified in paint later with some filler?
 
I was never able to get a very good dimple using the Vise Grip dimpler. It didn't have enough force to fully form the dimple in my experience.
 
Another experience datapoint.

Kevin Horton said:
I was never able to get a very good dimple using the Vise Grip dimpler. It didn't have enough force to fully form the dimple in my experience.
Click to expand...

I use vice-grip dimpler everywhere it will reach and have had nothing but perfect results.
 
Mine looks the sam, but not as bad.

Hello ?

The I riveted the upper wingskin with backriveting, so everything is very smooth and flat. The last row by the ailerons, I was dimpling with the pneumatic squeezer and also riveted with the squeezer.

They look now different then the rest of the wing. I should have riveted them with the gun instead the pneumatic squeezer, then they would look more the same.

I made then the other wing the same, so it looks like it has to be like this. So it is symetrical and maybe the skin roughness helps the airflow to stay attached to the aileron longer than with a absolute plane one, who knows ... (The glider builder put thick zig-zag tape in this area (top and bottom) to make the airflow turbulent, so it stays longer)

After painting it will be much less visible.

Regards, Dominik
 
Under dimpled

It looks like the dimples are not very crisp. Perhaps you could use the technique I used when dimpling the skin for the flap brace. It should work just as well in the aileron area:

Use a combination of dies...female pop rivet die with male regular die:
20071209-08-tn.jpg


Then squeeze the skin dimples thusly:
20071209-09-tn.jpg


My flap brace flange had been countersunk previously. Since your aileron fairing is dimpled, you may need to put a nut behind the flange or just redimple both parts together using regular dies.

When using the squeezer, I often squeeze the same hole twice...once with the yoke lying over as far as possible on it's left side, and again with the yoke laying over as far as possible on it's right side. It makes crisper dimples that way. I don't recall if I used that technique in this case or not.
 
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I was never able to get a very good dimple using the Vise Grip dimpler. It didn't have enough force to fully form the dimple in my experience.
Click to expand...

I agree with Kevin. We have received grief because we have never sold the vise-grip dimpling tool, and it is just for this reason. I designed this tool: http://www.cleavelandtoolstore.com/prodinfo.asp?number=DIE4263DF seen in the EAA videos to replace it. The rivet gun or hand hammer tap gives enough pressure to activate the springback of the dimple die. Mike C.'s idea is a great one that I have never seen before, but even the pneumatic squeezer just barely gives enough pressure to do a good dimple.

We hit many rivets from behind to fix them, but I am not sure that it will work in this case as there is just too much material stretched around each dimple. I would try to tap a few out from behind and if that doesn't work, drill them out and re-dimple them. I have only used a bucking bar on the outside, but the foamboard may be a trick.

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