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  #11  
Old 03-03-2015, 07:14 AM
MercFE MercFE is offline
 
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Location: Maple Valley, WA
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Quote:
Originally Posted by gfb View Post
Sig has an interesting idea. I wonder if because the hole is a little offset the rivet is filling under the dimple and cracking from pushing from behind.
I would agree with this... If you are in fact using the right length rivet, the shop head on your "lightly" set rivets doesn't have enough material in order to complete the set. It looks like the taps that you have given them have driven the material back between the skin and channel.
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  #12  
Old 03-03-2015, 07:26 AM
gfb gfb is offline
 
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I'm going to drill these out and see if there is a way to adjust my existing holes/dimples in the j-stringer without removing all ~30 rivets. I'd be happy to remove them but considering they are 95% good I worry about damage to the skin from the extra drilling. This is why I was thinking oops-rivet. It would allow me to open up the hole a bit, helping with the alignment... but now that I think about it, it would not re-align the dimple in the stringer.

Any other ideas?
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  #13  
Old 03-03-2015, 07:38 AM
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To answer your question, replace the J channel.
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  #14  
Old 03-03-2015, 07:43 AM
gfb gfb is offline
 
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Originally Posted by rv6rick View Post
To answer your question, replace the J channel.
Yeah, this is the right thing to do so I should just do it. I'll carefully start drilling out rivets and see if I can do it without making any ovals.

Any pointers on how to position a final drill/dimple on the j-stringer considering the skin it attaches to is already dimpled?
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  #15  
Old 03-03-2015, 07:44 AM
Sig600 Sig600 is offline
 
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Quote:
Originally Posted by rv6rick View Post
To answer your question, replace the J channel.
I would agree, cracks aren't going to get better with age. Especially since you're not sure what is causing them.
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  #16  
Old 03-03-2015, 09:19 AM
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Check your air pressure when you set these. For the small diameter rivets, you should only be using about 35 psi with a 3X gun with a mushroom set. If you are back riveting these with a longer rivet set, then the psi will need to go way up, since there is more metal in the rivet set to move with the air.
I agree it looks like the rivet length is too short for the holes. You should be using AN426AD3-3.5's and 3-4's under the wing walk doubler and where the J-stringers overlap.
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  #17  
Old 03-03-2015, 09:40 AM
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Default Drilling rivets

Drilling #3 flush rivets is no problem.
Center punch the little dimple exactly in the center of the head.
Use a small drill bit like #46 to drill first. Set the bit on the center punched hole and turn it a few turns. Take a look. If it's not centered you can coax it where it needs to go easily. If needed tilt the drill a tiny bit to drill in the direction needed for a few turns then go back to perpendicular.
Run the drill a few turns slowly and look again.
Once satisfied it's going centered, drill the depth of the head.
Use a #40 with a drill stop set to only allow it to drill the depth of the head. Drill the rivet head.
Take an old #40 bit and pop the head off.
Use a small punch to drive the shank with light taps.
If you have access, a pair of side cutters can be used to grab the shop head and pull it.

Wish I knew this trick before doing the Service Bulletin on my HS. I learned it drilling the 500+ rivets to disassemble it to fix one egg shaped mistake.
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  #18  
Old 03-03-2015, 10:18 PM
gfb gfb is offline
 
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Figured it out after drilling out the I-channel. The dimples were slightly offset from the skin which left an odd gap. The rivets had swished themselves into this gap, pushing up on the simple, causing the crack.

New stringer drilled and dimpled, waiting for primer to cure. Thanks all for the help!
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  #19  
Old 03-04-2015, 09:08 AM
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Gregg Brightwell Gregg Brightwell is offline
 
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Default Just checking....

Are you clecoing every other hole? If you are using too FEW clecos, the stringer won't rest tight against skin. If there is a gap, the rivet will try to fill that gap, thus pushing the stringer further away. Likely stating what you already know, just sayin....

GB.
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  #20  
Old 03-04-2015, 09:18 AM
WatkinsT1 WatkinsT1 is offline
 
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Location: Redmond, Oregon
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Default J Channel

I agree with Rick, for what its worth, replace the channel, this does not even look like a close call to me, there is definatly a problem here with the process, that caused this, I would replace it.
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