Rivet selection for back-riveting aileron skin stiffeners

I started to back-rivet the aileron skin stiffeners to the skins and came up with a problem. The drawing calls for a AN426AD3-3.5 rivets. I had the first stiffener all set up and noticed that the rivets look awful long for this application. I tried to drive one and of course it folded over (not literally of course). I then tried a -3 length rivet and it drove beautifully. The problem though with the -3 is I did not have enough height on the formed shop head. Diameter was good.

I did some searches and found someone had a problem on the rudder. I then looked at the rudder drawing and it calls for a -3 length to back-rivet the stiffeners to the skin. I don't know for sure, but I bet the skins and stiffeners are the same thickness between the aileron and rudder.

Anyhow, I'm frustrated at this point so I welcome all suggestions.

Are you checking the shop head with the spec Van's links to, or a rivet gauge? The spec, MIL-R-47196A, here: http://vansaircraft.com/public/Specs.htm should be used to assess the shop head. It might allow a thinner shop head than you expect.

Dave

Thanks Dave. I was using the standard 1.5Xdia for shop head diameter and 0.5Xdia for the shop head height.

I believe, but still have to verify, that I might achieve minimum height to the Mil spec limit using a -3 length rivet.

Dan

aeroaddict said:

I don't know for sure, but I bet the skins and stiffeners are the same thickness between the aileron and rudder.

Click to expand...

PART NUMBER NOMENCLATURE # PER A/C RV-7 PLAN PG # PART TYPE MAKE FROM MATERIAL SUB-KIT

R-901-L RUDDER SKIN 1 7 MANUFACTURED .016 2024-T3 ALCLAD EMPENNAGE
R-901-R RIGHT RUDDER SKIN 1 7 MANUFACTURED .016 2024-T3 ALCLAD EMPENNAGE

A-801PP-L AILERON SKIN 1 9,12,13A MANUFACTURED .020 2024-T3 ALCLAD AILERON
A-801PP-R AILERON SKIN 1 MANUFACTURED .020 2024-T3 ALCLAD AILERON

They're different thicknesses.

I had a similar issue when riveting the rudder stiffeners using the C frame. I found that I was applying a slight pressure to on side of my gun than another when I pulled the trigger. With a little change in pressure on the rivet gun handle, the rivets smashed down just right.
Hope this helps.

Thanks guys. I went with the -3's and measured almost every one and all were with limits of the Mil spec. (thanks Dave).