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I've seen some posts about people spacing their rivets closer than the recommended 2" to 3". I would think that drilling the extra holes in the frame for closer spacing would weaken the metal. I call it the swiss cheese effect. I am not sure that closer spacing is the best course of action. I'm sure there is an optimal spacing that gives you good panel holding but doesn't weaken the frame members. Any thoughts?
 

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Go with what is recommended. I put some rivets on the passenger footbox 1" apart, and it doesn't look good.

Keith
 

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Discussion Starter · #4 ·
Thanks guys, I was planning on following the factory recommendations, but was curious...

This board is an excellent resource.

[ September 19, 2002, 04:33 PM: Message edited by: FrankenCobra ]
 

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Aaron:
With the 2" spacing, how many extra rivets did you have to buy??? Just curious.

alc
 

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Originally posted by FrankenCobra:
I've seen some posts about people spacing their rivets closer than the recommended 2" to 3". I would think that drilling the extra holes in the frame for closer spacing would weaken the metal. I call it the swiss cheese effect. I am not sure that closer spacing is the best course of action. I'm sure there is an optimal spacing that gives you good panel holding but doesn't weaken the frame members. Any thoughts?
I don't think the frame would be adversly effected, since the rivets would be filling the space up anyways.
 

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In general, rivets placed in the center of tubing will not adversely effect anything. Those near the edges of tubing will provide stress risers which may (but most likely not) propogate into a crack over time. This is why you see all of your house plumbing run through the center of the joists.

The good news is that the frame members which see large enough loads where this may have an effect have been sized appropriately in addition to the compressed rivet helping to transfer the load.

When laying out my rivets I would put one at each end, one in the middle and then repeatedly split the differences until I ended up with ~ 2 to 2/12" spacing.

I also put in offset double rows on the larger square/rectangular tubing.
 

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The distance between rivets is called the Pitch Distance. As a rule of thumb for aircraft, the pitch distance should be 8-10 times the diameter of the rivet. For a 1/8 rivet, that makes it 1 to 1 1/4" between rivet bodies. Double rows should only be used if the edge distance (flap width) is greater than 1".

But for our use, hundreds of folks have used the 2-3" guideline with excellent results. So I guess it's up to you. For my car, I'll use a 1.5" pitch distance, and a #30 wire drill.

Another good tip is to dip each rivet body in epoxy before installing. It seals the hole and makes for a stronger bond.

And I think Cleco's are invaluable for this kind of thing.
 

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I looked at my trusty Aircraft Handbook and determined 1.25" - 1.5" to be the proper spacing for the 1/8" rivet and settled with 1.5". I've seen small rocks, debris, work itself into panel seams with the wider spaced rivets.
 

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Now when you guys approach Mach 1 you won't have to worry about the aluminum lifting and peeling back! ;)
 
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