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  #1  
Old 12-22-2017, 07:14 PM
Draker Draker is offline
 
Join Date: Jun 2016
Location: Livermore, CA
Posts: 97
Unhappy Bent top wing skin

Merry Christmas everyone!

Some days it seems like it's disaster after disaster on the RV-7 project. Today's one of those discouraging days. After a mishap with the deburring wheel, I'm left with a pretty badly bent wing skin:





This is the trailing edge of my top right inboard W-702 skin, after a great deal of re-straightening on my part. Maximum deflection in the center of the bend is approx. 1/4 inch. Looking ahead in the plans, it looks like this section overlaps the flap, and there are no rivets going in here that could "aid" in its straightening. The fit against the flap looks pretty tight, so this would probably end up rubbing against that control surface. I'm afraid it looks like I'll need to be ordering a new skin, but before I do, I thought I'd ask if anyone has any good repair ideas.

Best wishes, VAF!

Last edited by Draker : 12-22-2017 at 08:28 PM.
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  #2  
Old 12-22-2017, 07:52 PM
leok leok is offline
 
Join Date: Apr 2013
Location: Clarkston, MI
Posts: 207
Default Nothing to Loose

Since there is no choice except straightening or buying a new skin, I would go at it like there was nothing to loose.

I would put a piece of plywood under the area with a layer or two of soft cloth like a towel in between. Using a small round head bump hammer (body work hammer from HF would be about right) and gently tap back onto shape. The ply and cloth will have enough give when tapping to pull the surface in. Use a straight edge to repeatedly gage when the surface is flat. If it still has a little bit of roughness when finished, a little filler before paint will clean it up.
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  #3  
Old 12-22-2017, 08:24 PM
PilotjohnS PilotjohnS is offline
 
Join Date: Jan 2016
Location: Los Angeles
Posts: 469
Default Wait till others chime in

This kind of repair has been discussed before. I found some of the methods pretty neat and effective. I would wait till other experts chime in, and practice on scrap, before doing it for points. I was surprise some of the stuff that was repaired nearly perfectly.
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WARNING! Information presented in this post is my opinion. All users of info have sole responsibility for determining accuracy or suitability for their use.

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  #4  
Old 12-22-2017, 08:34 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 2,910
Default Skin damage

It's a top skin so what ever you do, it's going to show unless it's perfect. Ultimately it's what you can live with.
For the future, consider using a Vixen file to clean up long straight edges like skins. Much faster and safer. Two or three passes takes out the shear marks.
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I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #5  
Old 12-22-2017, 11:06 PM
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az_gila az_gila is offline
 
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Location: 57AZ - NW Tucson area
Posts: 9,372
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The fact that there are no creases in the damaged area is good.
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  #6  
Old 12-23-2017, 05:10 AM
mturnerb mturnerb is offline
 
Join Date: Apr 2015
Location: Ponte Vedra, FL
Posts: 624
Default

Quote:
Originally Posted by wirejock View Post
It's a top skin so what ever you do, it's going to show unless it's perfect. Ultimately it's what you can live with.
For the future, consider using a Vixen file to clean up long straight edges like skins. Much faster and safer. Two or three passes takes out the shear marks.
My trick here (stolen from Vlad) is to use a drywall sanding sponge, followed by a pass with 400 grit sandpaper. Edges end up really nice!
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  #7  
Old 12-23-2017, 11:30 AM
rockwoodrv9 rockwoodrv9 is offline
 
Join Date: Dec 2011
Location: Meridian ID, Aspen CO
Posts: 2,414
Default

If I am looking at it correctly, the bent end is what goes over the flaps. Since there is no support for the edge like up against the fuel tanks, it will be difficult to repair. You might as well give it a try. Once you get it bent back up and flattened out, you may have to find someone with an air powered stretcher-shrinker to get it straight. They can work wonders.

Best of luck on your repair.
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  #8  
Old 12-23-2017, 12:26 PM
Draker Draker is offline
 
Join Date: Jun 2016
Location: Livermore, CA
Posts: 97
Default

Wow, thanks to everyone so far with such good ideas. Definitely learned something the hard way yesterday: No more deburring large skins with the wheel. I'm also going to write the dollar amount on each part with a sharpie as I inventory from now on

I'm going to have a go at repairing it since there's nothing to lose, but will probably just end up re-ordering. Got another PM suggesting I try a sheet metal shrinker, so I'll be looking around locally for one to borrow (HF has them for more than the cost of a replacement skin). I think I've exhausted all other avenues that involve bending, banging, or squeezing--the metal is warped to the point where when I push on one side, it "pops" out the other. Don't think any amount of hammering is going to help it.

I'm planning to paint the airplane so I'm not concerned about cosmetic scratches, #1 concern is interference with flap.
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  #9  
Old 12-23-2017, 03:35 PM
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az_gila az_gila is offline
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 9,372
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Quote:
Originally Posted by Draker View Post
Wow, thanks to everyone so far with such good ideas. Definitely learned something the hard way yesterday: No more deburring large skins with the wheel. I'm also going to write the dollar amount on each part with a sharpie as I inventory from now on

I'm going to have a go at repairing it since there's nothing to lose, but will probably just end up re-ordering. Got another PM suggesting I try a sheet metal shrinker, so I'll be looking around locally for one to borrow (HF has them for more than the cost of a replacement skin). I think I've exhausted all other avenues that involve bending, banging, or squeezing--the metal is warped to the point where when I push on one side, it "pops" out the other. Don't think any amount of hammering is going to help it.

I'm planning to paint the airplane so I'm not concerned about cosmetic scratches, #1 concern is interference with flap.
Try asking around to see where your local shops/pilots would take planes for extensive sheet metal repair.

If one shop stands out, call them. It's probably a good bet that there is a single employee that is the "expert" at straightening out aluminum parts.

If you can find this guy in N. CA take the skin directly to him. It is a long shot but worth a few phone calls.

There aren't many folks around who can do metal forming/repairs to high standards any more, but if you can find one and watch him work it's an amazing sight.
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Grumman Tiger N12GA - flying
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  #10  
Old 12-25-2017, 06:52 PM
skidookid skidookid is offline
 
Join Date: Mar 2014
Location: ellenburg center ny
Posts: 72
Default skin repair

years ago I see a sheet metal man use a table spoon ( round side down)on top and piece of plywood covered with with 3 shop rags on bottom . re flatten a spot like yours. try on some scrap first . did need sanding to finish. good luck
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