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wrong rivets used in Skin/Spar

N

Neal Trombley

Well Known Member
I am building my 9a HS and somehow used 426AD3 3.5 ( skin to ribs)
than 426ad3- 4 (skin to spar )

I only did the left skin before noticing and I bucked riveted this thing fairly well..
they look great, but you can see on the right side with the correct rivet has more meat to it>>

should I start drilling?
 
Dont do it!

Ok if you have a rivet guage, i would check them with a guage first. If they are still under spec. DON'T PANIC. The real requirement is a mil spec that allows for more tolerance. I would contact Vans if you still think you need to drill out.
What i have found is a drilled out rivet is ugly, especially when you have to do so many. Please psot a picture.
 
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The three pics
First is correct

2nd and 3rd are incorrect
 
No dimples involved so measurements are easy.

Check the ones you think are bad, if they are over 0.038" high and more than 0.122" diameter they are good to go.

If not, since there is a whole row, not just a few interspersed, then they should be replaced. Search VAF for rivet removal procedures.
 
az_gila said:
No dimples involved so measurements are easy.

Check the ones you think are bad, if they are over 0.038" high and more than 0.122" diameter they are good to go.

If not, since there is a whole row, not just a few interspersed, then they should be replaced. Search VAF for rivet removal procedures.
Click to expand...

Thank you Gil
I will measure and take note..
 
There are some go-no go rivet gauges that are very helpful for quick measurements. If you don't have a set you should get one. I might have gotten mine from Avery (which doesn't exist any more), but Cleaveland Tools probably has them.
 
Photos help

Some of these look too thin as best I can tell and probably wont pass the go no-go guages. But listen to Gil, measure them because i believe the Go No-go gauges are very conservative. measuring is the ultimate test. The spec Gil refers to allows for a little more than 1/3 dia shop head height, where most rivet guagez are 1/2 shop head height. ( Please do not take my word for this, but decide on your own)
 
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While the shop heads may be a little thin, I think the majority, if not all of them, would actually be okay from a structural standpoint.

Alcoa (Think it was them) did a bunch of tests way-back-when to determine how much strength was lost from poorly and mis-set driven rivets, where it was determined even what we would view as shockingly bad rivets, rivets with cracked heads, etc, were still within 5% of the strongest properly-set rivet. Can't remember where I read it, but I'll try to find it.

In my mind, you're likely to do more damage drilling out a long line of rivets and replacing all of them than leaving them as-is.


EDIT: Haven't found the article yet, but multiple quotes from it:
Alcoa Aluminum Rivet Book said:
"The standards to which driven rivets should conform are frequently uncertain. In addition to dimensions and perfection of shape, inspection is concerned with whether the drive head is coaxial with the shank (not “clinched”) and whether there is excessive cracking of the heads. It has been determined that even badly cracked heads are satisfactory from the standpoint of static strength, fatigue strength and resistance to corrosion. (Poorly set and cracked) rivet heads were tested in tension to determine how well formed a head has to be in order to develop full strength. The tensile strengths of all the rivets were within five per cent of the strongest. The test indicated that minor deviations from the theoretically desired shape of head are not cause for concern or replacement. The second rivet that is driven in any one hole is likely to be more defective than the first because the hole is enlarged and rivet will be more likely to buckle and form an imperfect head.

Tests have shown that very small rivet heads are sufficient to develop the strength of the rivet shank, even when the rivets are subject to a straight tensile pull….where a large head is not needed for appearance, smaller sizes of drive head should be used to decrease the required driving pressures.
Click to expand...

And a quote from another VAF'er regarding poorly-set rivets:
Michael Burbidge said:
Here's the advice I received from Vans technical support when I asked them whether I should go to the next size rivet or not.

"Our advice is to never drill out a rivet unless you have to take the assembly apart. No matter how ugly it is, it probably has 90% the strength of a perfect rivet."
Click to expand...
 
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