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Main spar flange bend angle problem

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matronics(at)cencula.com
Guest

Posted: Sat Apr 28, 2007 9:40 am Post subject: Main spar flange bend angle problem

RV-ers,



I'm trying to figure out what to do about a problem with my main spar flanges.  

The problem is detailed at:



http://www.our7a.com/20070426.html

http://www.our7a.com/20070428.html



Essentially, I think I need to tweak the bend angle of the main spar flanges 

in some locations.



The problem is that the material is THICK and I've already riveted on my main 

ribs, so how can I tweak this angle?



I suppose I could remove all the main ribs.  It wouldn't be terrible since 

they're only attached to the main spar at this point, but I'd prefer to avoid 

that hassle if possible.



Any thoughts on how to tweak that spar flange?  Seaming pliers seems like a 

rough way to go.



Also, does anyone know what this angle is supposed to actually be?



Thanks,



Mike Cencula

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wskimike(at)mchsi.com
Guest

Posted: Sat Apr 28, 2007 4:07 pm Post subject: Main spar flange bend angle problem

Use a shim rather than trying to bend the rib because you may crack it. It 

would be better to shim it and don't

even think about bending the wing spar.

Mike

---

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ceengland(at)bellsouth.ne
Guest

Posted: Sat Apr 28, 2007 5:00 pm Post subject: Main spar flange bend angle problem

Michael D. Cencula wrote:

 	  Quote: 	
		   

 

 RV-ers,

 

 I'm trying to figure out what to do about a problem with my main spar flanges.  

 The problem is detailed at:

 

 http://www.our7a.com/20070426.html

 http://www.our7a.com/20070428.html

 

 Essentially, I think I need to tweak the bend angle of the main spar flanges 

 in some locations.

 

 The problem is that the material is THICK and I've already riveted on my main 

 ribs, so how can I tweak this angle?

 

 I suppose I could remove all the main ribs.  It wouldn't be terrible since 

 they're only attached to the main spar at this point, but I'd prefer to avoid 

 that hassle if possible.

 

 Any thoughts on how to tweak that spar flange?  Seaming pliers seems like a 

 rough way to go.

 

 Also, does anyone know what this angle is supposed to actually be?

 

 Thanks,

 

 Mike Cencula

Hi Mike,
	




If the flanges really are bent too much or not enough, you might be able 

to pull the flange down with a bar-clamp (like you'd use in cabinet 

making) and some big stiff angle to spread the load along the spar flange.



Having said that:



What does it look like if you cleco on the nose rib & wrap a strip of AL 

over the rib & spar flange? If that lines up and looks ok, read on.



IIRC, my spar flanges weren't exactly square to the web (but I think 

they were consistent in their bends).



The problem I *did* have, that caused some of the main rib/main spar 

joints to look just like yours, was a few bad ribs. After fighting the 

same gap between the spar flange & rib flange I see in yours, I noticed 

that that the other pair of flanges (top vs. bottom on the same rib) was 

too tight. Closer inspection revealed that the tooling holes in the 

problem ribs were distorted as if they had been dimpled off-center. The 

rib blanks had shifted in the punch press, causing all the holes to be 

punched offset by a fraction of an inch. The ribs' web flange holes 

being offset caused the rib to sit too high (or low, don't remember 

which) in relation to the spar. Further evidence was that the prepunched 

holes on the rib's top flange were a different distance from the edge 

from the holes on the bottom flange. All these holes get punched before 

the rib's flanges are bent.



A call to Van's tech help got the standard 'it's your fault; you're 

doing something wrong', followed by asking for proof (I supplied it), 

followed by the ubiquitous 'we've never seen this before', followed by 

'we'll send you new parts & if the old one really is defective when you 

return it, we won't charge you for the new one'. They didn't charge me 

for the new one.



I don't know if it's relevant to your problem, but it really does look 

like what I saw with mine.



Charlie

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Bob Collins

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

Posted: Sat Apr 28, 2007 5:53 pm Post subject: Main spar flange bend angle problem

I vaguely remember a similar problem here, but I used the O ring (s) trick

around the rivet so that the bucking bar was basically pushing the little

flange of the rib against the flange of the main spar. I'd be VERY reluctant

to try to bend the main spar material in any way. 



Do not archive

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

matronics(at)cencula.com
Guest

Posted: Tue May 01, 2007 8:42 pm Post subject: Main spar flange bend angle problem

For the archive:



After a talking with Scott at Van's, I learned that the spar flange angles 

are:



Top flange 88.5 +/-.5 degrees

Bottom flange 89 +/-.5 degrees

 

Measured between flange and web (in the corner where the main ribs sit)



My spar flanges were definitely out of spec.  Scott indicated that they have 

had several spars with this problem.  Apparently the spar channel is OK until 

it is assembled with the top and bottom bars.  This causes the flanges to 

open up a bit.



Scott recommended the same fix they use at Van's when they encounter this 

problem...cut a slot in a 2x4 and use that as a lever to tweak the flanges 

into positon.  My situation was a bit more difficult because I already had 

all the platenuts attached, so I needed a rather narrow tool to fit between 

the platenuts.  I tried several pieces of wood and composite material all of 

which broke on the first try.  I ended up getting a piece of 1/2 inch thick 

aluminum bar from the scrap tub at work and cut a slot in it.



After removing the main ribs (that was a chore) and  reworking the left spar 

flanges, I'd qualify results as very good.  Not perfect, but it's 95% better 

than it was originally.  Rib #5 was the worst rib with about .090 gap.  After 

reworking the flanges, there is essentially no gap between the spar flange 

and the rib joggle flange.  A similar improvement resulted at all the other 

ribs as well.



Hopefully someone will find this information useful in the future.



Happy building,



Mike



On Saturday April 28 2007 01:39 pm, Michael D. Cencula wrote:

 	  Quote: 	
		   



 RV-ers,



 I'm trying to figure out what to do about a problem with my main spar

 flanges. The problem is detailed at:



 http://www.our7a.com/20070426.html

 http://www.our7a.com/20070428.html



 Essentially, I think I need to tweak the bend angle of the main spar

 flanges in some locations.



 The problem is that the material is THICK and I've already riveted on my

 main ribs, so how can I tweak this angle?



 I suppose I could remove all the main ribs.  It wouldn't be terrible since

 they're only attached to the main spar at this point, but I'd prefer to

 avoid that hassle if possible.



 Any thoughts on how to tweak that spar flange?  Seaming pliers seems like a

 rough way to go.



 Also, does anyone know what this angle is supposed to actually be?



 Thanks,



 Mike Cencula

- The Matronics RV-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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

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