skin gap between rivets

[Wendell111]

I am practicing before I rivet the skins to the Longerons. The problem I have is the .002 +or= gap between the skin and the angle aluminum. Is this normal? It appears to me that the skin should be flush with the longeron. I use a DRDT-2 C Frame and I have used both Cleave land and Avery dimple dies. I install the dimple die and tighten until it touches but I can still turn the male die by hand- it is almost tight. When I loosen the gap my rivets set proud but the skin still has the gap. This question may come without pictures; since I am new, I have not figured out how to attach.

http://wendell111.smugmug.com/photos/63 ... BbY7-L.jpg
http://wendell111.smugmug.com/photos/63 ... DyJT-L.jpg
http://wendell111.smugmug.com/photos/63 ... pJzW-L.jpg
http://wendell111.smugmug.com/photos/63 ... pJzW-L.jpg

[Spike]

Let me help you out a bit here with the pictures:






By the way there is a thread under site support near the top that explains how to post images in threads.


As for your skin issue, it looks to me like you have not countersunk the longerons enough. When countersinking to accept a dimple you need to go deeper than you normally would for a rivet because there is extra material to fit into the countersunk hole.

Spike

[Wendell111]

Spike, Thanks very much for your response. I guess it would be better to have my own web site to post pictures I am currently using a commercial site on a 14 day trial.
I have posted a couple more pictures
I am using a 3/8 x 100’x # 40 cr Countersink I have used both single and triple flute.
The depth is .0400 (+) leaving .0750 (-) bar stock.
The part that bothers me is the Dia at the top of the countersunk cavity is .226 and the rivet is only .0169.
I guess the question is how deep is to much depth?

[img] http://wendell111.smugmug.com/Airplanes ... 8625_2oHTX [/img]

[img] http://wendell111.smugmug.com/Airplanes ... 8589_FoV36 [/img]

[bullojm1]

Wendell-

I can think of two things that could cause your problem. The first is what Spike pointed out, which is not countersinking the longeron deep enough. The second problem is you may not be applying enough pressure when your dimpling your skins. With the DRDT-2, there should be enough pressure applied to the dimple dies that the frame deflects slightly. If it doesn't, you are probably not creating a proper dimple, and that can cause the issue you are having. Just remember you cannot over dimple.

My suggestion is to get some scraps skin material and longeron material and practice on that. You definitely don't want any gaps like you have now. Everything should be very tight.

If you are still concerned, find a local RV builder or EAA chapter and get a second opinion.

[TomNativeNewYorker]

Lots of cleco clamps help. Always start riveting from the center and work your way to the outboard ends whenever possible.

[dons]

Hi Wendell,

In addition to what has been said above, I normally use about 0.007 to 0.009 deeper than flush for 0.025 or 0.032 skins, in cases like you show. In other words, I countersink so that if I drop a rivet in the counter sunk hole, the head is seven to nine thou below the surrounding surface. The dimple on the skin will seat better a bit when you rivet, so it doesn't have to be completely flat prior to riveting. This works for me, but you have to be happy with what you do.