Flange Centerline Location: A Very Basic Question

John R. Graham · #1 03-30-2011, 03:47 PM

Consider the following drawing:

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

az_gila · #2 03-30-2011, 08:57 PM

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.

flion · #3 03-30-2011, 10:55 PM

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.

az_gila · #4 03-31-2011, 12:43 AM

Quote:

Originally Posted by flion

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.

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...

Ironflight · #5 03-31-2011, 07:02 AM

Quote:

Originally Posted by az_gila

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...

Ha! You should see the -3 flanges....they make the 4/6 kits look positively REFINED!

flion · #6 03-31-2011, 09:08 AM

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...

Flying Scotsman · #7 03-31-2011, 10:26 AM

This

has been one of THE most useful tools in the shop...it's saved untold hours of time and frustration of cobbling up "tools" for measuring and marking various distances from edges. Highly recommended.

http://www.averytools.com/prodinfo.asp?number=6352

koda2 · #8 03-31-2011, 12:49 PM

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

n615ks · #9 03-31-2011, 03:32 PM

I had that question many years ago, and so looked at hole locations where they are shown on the plans in several places to confirm. I think I also found the specific answer somewhere as well.....in general, it's 1/2 of 'A' 99% of the time.

ditto on this: http://www.averytools.com/prodinfo.asp?number=6352

az_gila · #10 03-31-2011, 07:17 PM

Quote:

Originally Posted by koda2

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

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.