J

John R. Graham

Active Member
Consider the following drawing:
Flange-Center-Question.jpg

For the purposes of determining where to draw the centerline on a flange, where should I start measuring from on the left?
  • A: From the outer face of the web?
  • B: From the inner face of the web?
  • C: From the end of the radius?
  • Something else? (I don't really think so.)
If it's C, then I think there are sometimes minimum edge distance issues, so I don't think that's right either. Thanks in advance for the education. :)

- John
 
Even if you use C, that should not get you into edge distance problems for the typical 3/32 rivets.

I did use "other" and split B and C....:)

If your line drifts too far towards the web it can cause dimpling problems.
 
I made a flange marking tool by cutting a Popsicle stick in half crosswise. I drilled a #40 hole in one piece (which fits a fine Sharpie) and glued the other piece to the underside so the end was 5/16" from the hole. That bottom piece is my stop and I run it along the edge side of the flange, not the web side. That gives me a mark that is always the right edge distance. The flanges are pretty straight (even on my pre-pre-punched RV-6A kit) and I've never had a problem with being unable to line up the mark under pre-drilled rivet lines in a skin. So there's another vote for 'other'; I'd rather be sure of edge distance than try to establish a 'center' line.
 
flion said:
I made a flange marking tool by cutting a Popsicle stick in half crosswise. I drilled a #40 hole in one piece (which fits a fine Sharpie) and glued the other piece to the underside so the end was 5/16" from the hole. That bottom piece is my stop and I run it along the edge side of the flange, not the web side. That gives me a mark that is always the right edge distance. The flanges are pretty straight (even on my pre-pre-punched RV-6A kit) and I've never had a problem with being unable to line up the mark under pre-drilled rivet lines in a skin. So there's another vote for 'other'; I'd rather be sure of edge distance than try to establish a 'center' line.
Click to expand...

The flanges on the earlier RV4/6 kits were not that even - if anything they were slightly oversize at some locations.

I drew my line from the web side, checking for edge distance after marking.

Glad to hear the rib stamping got better...:)
 
az_gila said:
The flanges on the earlier RV4/6 kits were not that even - if anything they were slightly oversize at some locations.

I drew my line from the web side, checking for edge distance after marking.

Glad to hear the rib stamping got better...:)
Click to expand...

Ha! You should see the -3 flanges....they make the 4/6 kits look positively REFINED! ;)
 
I've heard horror stories, but the flanges on my 1994 tail kit and 1995 wing kit weren't bad. The wing kit was one of the earlier 'pre-punched' kits - actually, only the skins were punched, so you had to draw your center lines on the ribs and match them to the holes in the skin. The lines were usually straight enough that if you got the ends positioned right the lines showed up in all the intervening holes. Of course, it's not even an issue with the -10; we're getting so spoiled these days. Ok, cue the "I started my kit with a rubber plant and a deed to a bauxite mine" stories... ;)
 
MIL-R-47196A(MI)

In reading the above document, there is a sketch and description(p 13), relating to rivet edge distance in a flange. Although it refers to a universal rivet, it would seem the shop head would apply as well and the .3" should apply.

I have offset my rivet lines ever so slightly to strike a happy medium between "preferred" edge distance for flush rivets and the center of the mating surface of the sheet and flange, because of this.

I doubt that it really makes that much difference.

Dave A.
6A build
 
koda2 said:
In reading the above document, there is a sketch and description(p 13), relating to rivet edge distance in a flange. Although it refers to a universal rivet, it would seem the shop head would apply as well and the .3" should apply.

I have offset my rivet lines ever so slightly to strike a happy medium between "preferred" edge distance for flush rivets and the center of the mating surface of the sheet and flange, because of this.

I doubt that it really makes that much difference.

Dave A.
6A build
Click to expand...

The dimension is the specification is 0.03 - you are 10x out...:)

Assuming a 3T bend radius in 0.025 material and a 1.5x shop head, this gives a dimension of 0.163 to the hole center from the far side of the web - it should not come into the equation here.
 
Dimensions

Gil,
You are correct in calling out my typo error, but depending on the flange, the bend radius and the rivet size, there may not be much margin for error. Some of the flanges I have had to work with were not 5/8, plus with a fairly generous bend radius. The flat was significantly less than the mold line.

I understand the drawing as showing the side of the rivet head beginning at a minimum point .030 from the edge of the bend radius.

By picking a line that allows a little extra margin than the minimum on each side, I am still in good shape if my drill point errs a bit, or God forbid, I screw up the rivet and have to go up a size. It has happened. :D

Centering the rivet hole, more or less, on the flat, seems to work best for me and meets the minimums with a little to spare.

Dave A.
6A build
 
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koda2 said:
....Centering the rivet hole, more or less, on the flat, seems to work best for me and meets the minimums with a little to spare.

Dave A.
6A build
Click to expand...

OK... so you are a vote for "C" in post #1.

I think we have the entire spectrum covered in the responses...:)
 
I went ahead and made measurements on two representative prepunched flanges from my RV7 kit. First, here's a slightly updated drawing:
Flange-Center-Question3.jpg


The two parts were:
  • A wing rib. D turned out to be exactly half of A: (D = A / 2).
  • The vertical stabilizer spar. Here the observed centerline was moved towards the flange edge by about 2/3 of the radius, resulting in the rather ugly D = (A / 2) + 2*(A - C) / 3.
I'd note that the bend radius on the rib was rather tight whereas the bend radius on the spar was considerably greater. So far, I don't see an elegant, general rule that covers both. I guess I have my answer, though.

- John
 
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