DWG 12, area E-9, calls for AN426AD3-3 rivets to secure the W-724 aileron gap fairing to the W-703 upper wing skin. These are clearly too short on my project -- barely one rivet diameter in length protrudes through the other end of the hole. AN426AD3-3.5 would seem to be much more appropriate. Are these rivets intentionally called out a bit short to ensure there's no interference with the aileron or something?
Van's Air Force
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Aileron gap fairing to skin - intentionally short rivets?
- Thread starter smiller
- Start date
-3.5 work perfectly
Well, I was reluctant to set -3 rivets (as the drawings call out), so I asked Van's. They replied that -3.5 is fine as long as they don't fold over, which of course they didn't. They were the perfect size. (I squeezed them all.) It's interesting that this [apparently] hasn't come up in the forums before. I suppose a -3 would work if the skin/gap fairing were countersunk, but that would seem to be a bad idea (I dimpled both).
Anyway, they're all set now (-3.5), look beautiful, and there seems to be no issues at all with regard to interference or anything like that.
Since it looks like I can't delete my post (which generated no replies), I figured I'd post this follow-up for the record.
Building on!
Well, I was reluctant to set -3 rivets (as the drawings call out), so I asked Van's. They replied that -3.5 is fine as long as they don't fold over, which of course they didn't. They were the perfect size. (I squeezed them all.) It's interesting that this [apparently] hasn't come up in the forums before. I suppose a -3 would work if the skin/gap fairing were countersunk, but that would seem to be a bad idea (I dimpled both).
Anyway, they're all set now (-3.5), look beautiful, and there seems to be no issues at all with regard to interference or anything like that.
Since it looks like I can't delete my post (which generated no replies), I figured I'd post this follow-up for the record.
Building on!
BSwayze
Well Known Member
I agree with Steve, Shannon. I always measure with my little rivet gauge and I have often ended up using rivets the next size longer. Funny... I don't recall ever measuring and using a shorter one... I just wanted to make sure I had enough length to form a good solid shop head. Sounds like you're making some excellent progress on those wings!
longranger
Well Known Member
I installed my left aileron gap seal about a month ago, and don't recall rivet length being an issue. If I had noticed the rivets being a tad short, I would have written off as being for clearance of the aileron. I haven't built the ailerons yet, but it looks like the nose might come pretty close to the upper skin.
Unlike the flap brace, the aileron gap seal is more of a fairing than a structural part, and even if all the rivet heads are a bit thin I don't think it would be a problem.
Unlike the flap brace, the aileron gap seal is more of a fairing than a structural part, and even if all the rivet heads are a bit thin I don't think it would be a problem.
Agreed. Had I not received an answer I would have gone with what the plans called out, short or not, since it appears the aileron gap fairing is not for any significant structure purpose. But when Van's said I could go with the -3.5's I proceeded to use them, as I wrote above.
I'm wondering if there are differing interpretations of how it "should" be. All my references (AC 43.13 Figure 4-6, etc.) say that the exposed rivet shank, before set the rivet, should be 1.5 times the rivet diameter. I have other books that say the same. And in all of them, they show an illustration where the lower piece of aluminum being riveted (the piece further from the rivet's manufactured head) is other than dimpled.
Like you, I dimpled both the wing skin and the fairing flange that attaches to it (and I used tank dimple dies on the latter, like you). Now, if I place my handy dandy rivet gauge over the shank, it sits flush with the skin, and appears to show the proper rivet length. See "B" in the figure below. But my interpretation of "the book" is that the rivet gauge should be set up on the dimple, so that we're measuring the rivet shank length from the lowest part of the dimple, as shown in "A" below.
The rivet will expand to fill in the gap between the two dimples and the shop head will form up against the lower dimple in the above figure.
In my case, where I'm wondering whether to use a -3 or a -3.5, the difference is only 15 thousand's of an inch, which is awfully close to what the lower dimple protrusion is.
At any rate, the -3.5 worked well and it doesn't look like there will be any interference issue at all. The shop heads are perfect (.5D tall and 1.5D in diameter). But I agree with you that it likely doesn't matter in this particular area... and I wouldn't lose any sleep whatsoever had I used the -3.0's here.
Alright, I guess I've beat this horse to death... unless I should be using measurement "B" in the above situation/figure, in which case I would appreciate someone setting me straight!
I'm wondering if there are differing interpretations of how it "should" be. All my references (AC 43.13 Figure 4-6, etc.) say that the exposed rivet shank, before set the rivet, should be 1.5 times the rivet diameter. I have other books that say the same. And in all of them, they show an illustration where the lower piece of aluminum being riveted (the piece further from the rivet's manufactured head) is other than dimpled.
Like you, I dimpled both the wing skin and the fairing flange that attaches to it (and I used tank dimple dies on the latter, like you). Now, if I place my handy dandy rivet gauge over the shank, it sits flush with the skin, and appears to show the proper rivet length. See "B" in the figure below. But my interpretation of "the book" is that the rivet gauge should be set up on the dimple, so that we're measuring the rivet shank length from the lowest part of the dimple, as shown in "A" below.
The rivet will expand to fill in the gap between the two dimples and the shop head will form up against the lower dimple in the above figure.
In my case, where I'm wondering whether to use a -3 or a -3.5, the difference is only 15 thousand's of an inch, which is awfully close to what the lower dimple protrusion is.
At any rate, the -3.5 worked well and it doesn't look like there will be any interference issue at all. The shop heads are perfect (.5D tall and 1.5D in diameter). But I agree with you that it likely doesn't matter in this particular area... and I wouldn't lose any sleep whatsoever had I used the -3.0's here.
Alright, I guess I've beat this horse to death... unless I should be using measurement "B" in the above situation/figure, in which case I would appreciate someone setting me straight!
az_gila
Well Known Member
Actually, this is what the Mil-Spec says -
The rivet grip lengths shown on drawings shall be verified prior to installation. Grip length shall be changed as material thickness dictates as required to achieve minimum head dimensions as shown in Table III without buckling or bending or other driving difficulties.
The 1.5 D protrusion is not in any part of the specification. The correct amount is that which gives you the correct formed shop head.
The 1.5 D is only a guideline before driving the rivet.
http://mybearhawk.com/MIL-R-47196A_MI.pdf
The rivet grip lengths shown on drawings shall be verified prior to installation. Grip length shall be changed as material thickness dictates as required to achieve minimum head dimensions as shown in Table III without buckling or bending or other driving difficulties.
The 1.5 D protrusion is not in any part of the specification. The correct amount is that which gives you the correct formed shop head.
The 1.5 D is only a guideline before driving the rivet.
http://mybearhawk.com/MIL-R-47196A_MI.pdf
az_gila
Well Known Member
