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  #1  
Old 01-05-2010, 02:28 PM
Pilottonny Pilottonny is offline
 
Join Date: Jan 2006
Location: Belgium
Posts: 645
Default Wing skin bulging at skin-lap (with pictures)

I built my wings a long time ago and had them on the wall of the garage since. Now I installed the left one on the plane and noticed something I had not seen before! One bay of the top wing skin, at the lap joint (why could it not have been the bottom skin!?) is bulging out. It is the most visible at the spar. I can push it down, bulging the opposite way. The right wing has it also, exactly in the same place, but not as much as the left wing. It really bugs me now, since this will be very visible ones the wings are painted. I believe it is really only an esthetics thing, because it is not “oil canning”.

I contacted a car repair shop that do “repairs without painting” (that is what they call it over here, it is a way to take dents out of cars without damaging the paint) today. The guy had no idea that I was talking about a real plane (he asked me if I could bring it to their shop to show them!) I do not know how it works, but I figured that if they can get dents out of cars that way, maybe they can “shrink” the skin so it does not bulge anymore. I will send him these pictures and see what they say.

In one way I am lucky that it is exactly at the location of one of the inspection panels, so I have good access.

Some more solutions come to mind:
  • Rivet in two J-stringers and make the skin sit flatter, but this will show very well in the skin and may even make things worse?? I can fill in the rows of rivets before paint, so they do not show. Hhmmm…… I guess the skin will still have some minor bulges that will show very well, ones the plane is painted.
  • Slice the skin, from one corner to the other, to get rid of the tension and make the skin sit flat. Than bond the skin back together from the inside with glass fiber and epoxy and fill in the slit on the outside with micro and epoxy. Hhmmm……. is this acceptable and will it last? A lot of work also!
  • Drill out the rivets on two sides of the area and re-rivet. Hhmmm……. will it not be just the same when I rivet it back? Also a lot of work and maybe enlarge the rivet holes in the process. Not so good.
  • Push it down and glue a skin-doubler on the inside with RTV or the likes. Hhmmm…… that sounds good, a little heavy maybe, and how do I get it to sit nice and flat?
  • Leave it as it is and (try to) forget about it. Hhmmm……. but what if it turns out to be even more horrendous than I think it will be, ones the plane is painted, only the skin doubler can be installed without f%$*&ng up the paint job.
This picture shows the bulge best: I put a piece of wood across, you can see clearly that it bulges out, it is most significant near the spar. The other wing is still hanging on the wall in the background.



This is a view from the top, it does not realy show the bulge in this picture, but it is the bay outboard of the lap joint.

Luckily, there is plenty of access on the inside due to the exact location over the inspection panel.

Any input is appreciated and will be treated as “advice” only, will hold no grudge if it does not work! Thanks in advance. Regards, Tonny.
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"Pilottonny"
Tonny Tromp
Lanaken, Belgium (EU)
RV9A, Registration: PH-VAN
ECI-Titan IOX-320 with dual EI, turning a Whirlwind 200RV CS prop.
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Last edited by Pilottonny : 01-06-2010 at 04:57 AM.
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  #2  
Old 01-09-2010, 02:16 AM
Pilottonny Pilottonny is offline
 
Join Date: Jan 2006
Location: Belgium
Posts: 645
Unhappy Car repair shop can not do it!

I spoke to a guy who takes dents out of cars whithout damaging the paint. He said it can not be done that way, because the bulge is to large (wide). So I have to figure out something else.

Next I will send an email to Van's, see what they say.

Regards, Tonny.
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"Pilottonny"
Tonny Tromp
Lanaken, Belgium (EU)
RV9A, Registration: PH-VAN
ECI-Titan IOX-320 with dual EI, turning a Whirlwind 200RV CS prop.
Sold
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  #3  
Old 01-09-2010, 03:03 AM
Bob Axsom Bob Axsom is offline
 
Join Date: Mar 2005
Posts: 5,685
Default I would not change a thing

I can't think of anything you can do that will not expose you to more problems. It is very smooth and if there is not a real problem I would press on. Many times when building my plane I would get distraught over something that wasn't exactly perfect but in the over all (big picture) perspective it didn't amount to anything. I think I developed a more reasonable perspective as I went along. This probably doesn't apply in your case But I always use a lot of clecoes and work in one direction.

Bob Axsom
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  #4  
Old 01-09-2010, 07:00 AM
rv72004 rv72004 is offline
 
Join Date: Nov 2005
Posts: 452
Default

Maybe you could try removing the row of rivets and bonding the skin down with a long flat angle to squeeze out bumps. Once set you can ream the holes that are slightly out and rerivet. Seen it done on another area and it worked ok.
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RV7 flying
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  #5  
Old 01-09-2010, 09:53 AM
Pilottonny Pilottonny is offline
 
Join Date: Jan 2006
Location: Belgium
Posts: 645
Default The tank is definately part of the problem!

Today I removed the tank (long range, extra long tanks) and the bulge went from 3 mm (approx 1/8) to 1,5 mm (approx 1/16). I will see if giving a bit more clearance between the tank- and the wing-skin, may help keeping it at 1/16 and than leave it as is.

Regards, Tonny.
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"Pilottonny"
Tonny Tromp
Lanaken, Belgium (EU)
RV9A, Registration: PH-VAN
ECI-Titan IOX-320 with dual EI, turning a Whirlwind 200RV CS prop.
Sold
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