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Wing skin crack

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benson(at)mrsl.com
Guest

Posted: Mon Sep 18, 2006 10:51 am Post subject: Wing skin crack

Hello everyone,



I've been monitoring this list for several years now and have found it very

useful while building my -8QB. I have never felt the need to post anything

until now.



I received word that the owner/builder of an -8A in my local area,

(southwest Florida), has found a crack in the top skin of his left wing. The

plane has been flown approx. 500 hours and the crack is located just

outboard of the wing walk doubler, where the top skin is riveted to the rear

spar. Specifically, the crack has started where the top skin overlays the

doubler on the rear spar at the first rivet outboard of the doubler and has

propagated outboard through the next three rivets.



Has anyone else with higher time airframes noticed any skin cracks in this

area? Apparently the builder contacted Vans and they were unaware of any

problems from other builders and suggested that his skin might have

contained flaws in that area.



I am still several months away from final assembly and am wondering if I

should do anything to avoid this potential problem before I hang the wings.



Thanks,



Lonn Benson     RV-8QB (#81666)

Osprey, Florida

Bob Collins

Joined: 11 Mar 2006
Posts: 470
Location: St. Paul, Minnesota

Posted: Mon Sep 18, 2006 4:22 pm Post subject: Wing skin crack

I don't have the answer, but I do have a question. Why would someone wait on

a crack and watch it gobble up three rivets rather than stop drill it right

away?



Bob



Do Not archive 



--

_________________
Bob Collins
St. Paul, Minn.
Letters from Flyover Country
http://rvnewsletter.blogspot.com/

lifeofreiley2003(at)yahoo
Guest

Posted: Mon Sep 18, 2006 5:15 pm Post subject: Wing skin crack

I've seen this happen with holes not being deburred

before being dimpled. A slight tear can occur when the

dimple is set and then the crack can follow the line

of the rivets or take another direction. Also, an

incorrect matching angle issue from the rear spar to

the skin can cause excess stress.



 





      Darrell Reiley

  RV7A "Reiley Rocket"

  N622DR  Reserved 

  N469RV  Reserved

   

  CenTex_RV_Aircraft-owner(at)yahoogroups.com

   

  



__________________________________________________

khorton01(at)rogers.com
Guest

Posted: Mon Sep 18, 2006 5:30 pm Post subject: Wing skin crack

 	  Quote: 	
		   



 Has anyone else with higher time airframes noticed any skin cracks  

 in this

 area? Apparently the builder contacted Vans and they were unaware  

 of any

 problems from other builders and suggested that his skin might have

 contained flaws in that area.



 I am still several months away from final assembly and am wondering  

 if I

 should do anything to avoid this potential problem before I hang  

 the wings.


	


I've been a subscriber to the RV-List since 1997, and the Yahoo RV-8  

list (and it predecessors) since it was first created.  This is the  

first report I can recall of a crack in any of the wing skins.  I  

think there was something unique about this situation.  Either some  

damage, or a builder error, or some other major event that caused  

this.  I wouldn't make any changes in this area.  Trying to add more  

material to beef up the structure may change the load paths, and put  

more stress somewhere else.  You could easily make more problems than  

you solve.



Build on.



Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

chaztuna(at)adelphia.net
Guest

Posted: Tue Sep 19, 2006 9:25 am Post subject: Wing skin crack

It can also happen when the builder dimples directly on the pre-punched #42 size hole. If the hole is below #40 size, small micro cracks can be formed during the dimpling process. The same thing happens when dimpling #19 holes for #8 machine screws. When dimpling for a #8 screw, open the hole up to a #17 size drill. Ask me how I know this!  

 Charlie Kuss



 

 [quote]--> RV-List message posted by: Darrell Reiley <lifeofreiley2003(at)yahoo.com>



 I've seen this happen with holes not being deburred

 before being dimpled. A slight tear can occur when the

 dimple is set and then the crack can follow the line

 of the rivets or take another direction. Also, an

 incorrect matching angle issue from the rear spar to

 the skin can cause excess stress.



  



 



 

       Darrell Reiley

   RV7A "Reiley Rocket"

   N622DR  Reserved 

   N469RV  Reserved

    

   CenTex_RV_Aircraft-owner(at)yahoogroups.com

    

   



 



 



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 [b]

jp_rv2001(at)yahoo.com
Guest

Posted: Tue Sep 19, 2006 4:43 pm Post subject: Wing skin crack

Section 5E of the -7 manual contains a caution about the potential for cracks to develop from pre-punched holes that are not match drilled... drilling removes shear marks left by the punch process.

   

  "... removing the shear marks is important because if left alone, the skin can crack around the hole due to the stretching caused by the dimple dies.  This cracking may not be apparent for several years after many hours of vibrations and flight cycles."

   

  jp



  		Get your email and more, right on the [url=http://us.rd.yahoo.com/evt=42973/*http://www.yahoo.com/preview] new Yahoo.com[/url]   [quote][b]

jp_rv2001(at)yahoo.com
Guest

Posted: Thu Sep 21, 2006 6:20 am Post subject: Wing skin crack

Search the archives on 'match drill' and you will find there have been several lengthy discussions about this (March '04 and April '02, etc.)... in my mind there is a connection, in the mind of others there may not be.  

   

  I will use my judgement, you will use yours...  Perhaps this is why i am committed to building my own RV rather than buying one from somebody else.

   

  jp



  [quote][b]

jjessen

Joined: 22 Apr 2006
Posts: 285
Location: OR

Posted: Thu Sep 21, 2006 7:43 am Post subject: Wing skin crack

I've matched drilled and deburred and dimpled and I still don't see a  smoothness around the hole.  I often see little nibbles or some such  thing.  Not cracks, but it does make me wonder if I'm doing things  correctly.  Should be smooth, should it not?  

  

 John Jessen

   #40328



   From: owner-rv-list-server(at)matronics.com  [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Jim  Peoples

Sent: Thursday, September 21, 2006 7:20 AM

To:  rv-list(at)matronics.com

Subject: RE: Wing skin  crack

 

 Search the archives on 'match drill' and you will find there have been  several lengthy discussions about this (March '04 and April '02, etc.)... in my  mind there is a connection, in the mind of others there may not be.  

  

 I will use my judgement, you will use yours...  Perhaps this is why i  am committed to building my own RV rather than buying one from somebody  else.

  

 jp

 

[quote]



com/Navigator?RV-List



[b]

Hopperdhh(at)aol.com
Guest

Posted: Fri Sep 22, 2006 5:23 am Post subject: Wing skin crack

John,

  

 Like you, I have looked closely at the holes after dimpling, and see a  roughness -- even though the holes were deburred before dimpling.  For  sure, a smaller hole would be more likely to have stress cracks after dimpling  than a bigger hole, so no. 40 is the right drill to use, not 41 as some have  done, or no drill at all.

  

 Maybe the best thing to do is to deburr the hole AFTER dimpling.  But  many airplanes have been built without doing this and none (that I know of) have  fallen out of the sky due to skin cracks.  Aluminum does fatigue and  eventually all of the RV's will start cracking!  Maybe in 50,000  hours?

  

 Dan Hopper

 RV-7A

  

  

 In a message dated 9/21/2006 11:45:52 A.M. Eastern Daylight Time,  jjessen(at)rcn.com writes:

  	  Quote: 	
		     I've matched drilled and deburred and dimpled and I still don't see a    smoothness around the hole.  I often see little nibbles or some such    thing.  Not cracks, but it does make me wonder if I'm doing things    correctly.  Should be smooth, should it not?  

    

   John Jessen

     #40328



         From: owner-rv-list-server(at)matronics.com    [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Jim    Peoples

Sent: Thursday, September 21, 2006 7:20 AM

To:    rv-list(at)matronics.com

Subject: RE: Wing skin    crack

   

   Search the archives on 'match drill' and you will find there have been    several lengthy discussions about this (March '04 and April '02, etc.)... in    my mind there is a connection, in the mind of others there may not be.     

    

   I will use my judgement, you will use yours...  Perhaps this is why    i am committed to building my own RV rather than buying one from somebody    else.

    

   jp

   

 	  Quote: 	
		  



com/Navigator?RV-List







="http://www.matronics.com/Navigator?RV-List">http://www.matronics.com/Navigator?RV-List

.matronics.com/">http://forums.matronics.com

ronics.com/">http://wiki.matronics.com

://www.matronics.com/contribution">http://www.matronics.com/contribution



	
	


 

  

  [quote][b]

jjessen

Joined: 22 Apr 2006
Posts: 285
Location: OR

Posted: Fri Sep 22, 2006 7:25 am Post subject: Wing skin crack

Just makes one a little  quizzical after all the preparation, but something has to happen with the  deformation.  

  

 John Jessen

  

 do not  archive



   From: owner-rv-list-server(at)matronics.com  [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of  Hopperdhh(at)aol.com

Sent: Friday, September 22, 2006 6:22  AM

To: rv-list(at)matronics.com

Subject: Re: Wing skin  crack

 

   

 John,

  

 Like you, I have looked closely at the holes after dimpling, and see a  roughness -- even though the holes were deburred before dimpling.  For  sure, a smaller hole would be more likely to have stress cracks after dimpling  than a bigger hole, so no. 40 is the right drill to use, not 41 as some have  done, or no drill at all.

  

 Maybe the best thing to do is to deburr the hole AFTER dimpling.  But  many airplanes have been built without doing this and none (that I know of) have  fallen out of the sky due to skin cracks.  Aluminum does fatigue and  eventually all of the RV's will start cracking!  Maybe in 50,000  hours?

  

 Dan Hopper

 RV-7A

  

  

 In a message dated 9/21/2006 11:45:52 A.M. Eastern Daylight Time,  jjessen(at)rcn.com writes:

  	  Quote: 	
		     I've    matched drilled and deburred and dimpled and I still don't see a smoothness    around the hole.  I often see little nibbles or some such thing.     Not cracks, but it does make me wonder if I'm doing things correctly.     Should be smooth, should it not?  

    

   John    Jessen

        #40328



         From: owner-rv-list-server(at)matronics.com    [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Jim    Peoples

Sent: Thursday, September 21, 2006 7:20 AM

To:    rv-list(at)matronics.com

Subject: RE: Wing skin    crack

   

   Search the archives on 'match drill' and you will find there have been    several lengthy discussions about this (March '04 and April '02, etc.)... in    my mind there is a connection, in the mind of others there may not be.     

    

   I will use my judgement, you will use yours...  Perhaps this is why    i am committed to building my own RV rather than buying one from somebody    else.

    

   jp

   

 	  Quote: 	
		  



com/Navigator?RV-List







="http://www.matronics.com/Navigator?RV-List">http://www.matronics.com/Navigator?RV-List

.matronics.com/">http://forums.matronics.com

ronics.com/">http://wiki.matronics.com

://www.matronics.com/contribution">http://www.matronics.com/contribution



	
	


 

  

[quote]



com/Navigator?RV-List



[b]

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