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  #1  
Old 11-30-2008, 09:23 PM
kcameron kcameron is offline
 
Join Date: Jan 2005
Posts: 210
Default How to fix wing skin crack?

I was thinking that my RV-4 is within a couple of weeks or so of being ready to fly after its makeover. Unfortunately, I've hit a snag that could delay me. After 13 months without a flying airplane this smarts a bit.

I found this wing crack on my top right wing skin just behind the tank:


Anyone seen a crack like this on an RV before? I'm guessing I'll need to add a doubler plate but it's the details that are stumping me. What thickness? How big? Do I drill out the existing rivets into the spar and re-rivet the doubler through those holes? There's no backside access so I guess I'll need to use pulled rivets; but which ones? And so on...

Thanks in advance.

Kev
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Kevin Cameron - Fresno, CA - E79
N493DB RV4 Flying
IO-360-A1B, 10:1, Straight-Bore cylinders, Gapless Piston Rings, Hartzell CS Prop,
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  #2  
Old 12-01-2008, 01:01 AM
kcameron kcameron is offline
 
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Default

The plane has about 800 hours of Hobbs time.

I thought about just stop-drilling the crack but I don't know what kind of stress it sees. I guess it would only be an issue during negative-g loads?

I had been thinking of just adding an external patch. Do I really need to cut out the bad spot to have an effective repair?
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Kevin Cameron - Fresno, CA - E79
N493DB RV4 Flying
IO-360-A1B, 10:1, Straight-Bore cylinders, Gapless Piston Rings, Hartzell CS Prop,
AFS3400-EE, TruTrac DFII VS, Aera 660, GTX 335, GDL 52R,
XM Radio, SL30, SL40, PMA9000EX, MicroTrac 300 APRS
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  #3  
Old 12-01-2008, 02:08 AM
kiwipete kiwipete is offline
 
Join Date: Oct 2007
Location: Birmingham United Kingdom
Posts: 374
Default

Kev

Firstly I would check with Van's.
I can't see any reason other than looks that you couldn't put a patch over the top. Material of the same thickness and large enough to take in the rivets either side of the crack. I've done and seen this enough times before on Cessna's etc.

Peter
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  #4  
Old 12-01-2008, 04:03 AM
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Fredrik Fredrik is offline
 
Join Date: Apr 2007
Location: Stockholm, Sweden
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I could be absolutely wrong here, but is that a crack? It looks like a fine thread/hair caught under the rivet, before painting.

/Fredrik
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  #5  
Old 12-01-2008, 10:19 AM
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fl-mike fl-mike is offline
 
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Default

Quote:
Originally Posted by Fredrik View Post
I could be absolutely wrong here, but is that a crack? It looks like a fine thread/hair caught under the rivet, before painting.

/Fredrik
Yeah, sorta looks like a fiber from a scotchbright pad to me as well. Get out the magnifier.
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  #6  
Old 12-01-2008, 02:11 PM
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wingtime wingtime is offline
 
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Location: Clearwater, FL
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Default Now that you...

I'd have agree that it looks like a fiber of some sort under the paint too. Almost looks like it was caught under the rivet head before painting.
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  #7  
Old 12-01-2008, 02:20 PM
Sid Lambert Sid Lambert is offline
 
Join Date: Jul 2005
Location: North Atlanta
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I had something that looked like this on the right tank of my -4. I thought it was a crack but after I used a scotch bright wheel to knock the paint off I found it was just a paint defect. Luckily it's on the bottom of the wing where no one notices it.
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Last edited by Sid Lambert : 12-01-2008 at 02:34 PM.
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  #8  
Old 12-01-2008, 02:31 PM
kcameron kcameron is offline
 
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Posts: 210
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I'm pretty sure it's a crack but since you guys have raised the doubt, I'll take a closer look when I get back to the hangar.

Thanks.
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Kevin Cameron - Fresno, CA - E79
N493DB RV4 Flying
IO-360-A1B, 10:1, Straight-Bore cylinders, Gapless Piston Rings, Hartzell CS Prop,
AFS3400-EE, TruTrac DFII VS, Aera 660, GTX 335, GDL 52R,
XM Radio, SL30, SL40, PMA9000EX, MicroTrac 300 APRS
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  #9  
Old 12-01-2008, 02:43 PM
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rocketbob rocketbob is offline
 
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If it is a crack, leave it alone unless you put a patch over it. In my experience stop-drilling almost never works in stopping a crack from propagating. In this case if it is a crack, you really can't stop drill it without getting into the spar. Since this is on the top skin I wouldn't worry too much, I've seen several older RV's with cracks around the wingwalk area. Most of those cracks are cosmetic from the paint flexing when someone steps in that area.
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  #10  
Old 12-01-2008, 06:15 PM
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Andrew M Andrew M is offline
 
Join Date: Aug 2006
Location: Secluded Lake,Alaska (AK49)
Posts: 359
Default Stop drill it!

If it were mine I would take the paint off that spot and see how far it really goes with a magnifier. Stop drill with a 30 or larger, (spot facer?)ream if possible. Put some sealant under it to dampen vibrations and keep an eye on it. I'm certain it will give you LOT'S of warning before it lets go completely. Good chance that it has relived itself and won't propagate. (look at the direction the crack is taking) How far is the crack from a chordwise line of rivets?
I've been working on aluminum aircraft for 20 years, I think you will be fine.

AWM
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