Countersink following dimpling?

[Stewie]

Hi all-
Was impressed by the extremely smooth countersunk HS skin I saw on a neighbor's -4 last week. It was so smooth, it looked like it had been back riveted. I know it is not recommended to CS aluminum that thin, but I was wondering: could a person dimple the skins, then run a CS in the dimple? You'd get the shear stress benefit of dimpling, and the aesthetics of a CS hole without taking away much material. My emp is finished, and I was told the slight undulations along the rivet line are typical, but I thought I might try this on the wing.
Searched the forums for this but couldn't find anything, please redirect me if this has been previously discussed.
Thanks, everyone have a good weekend.
Eric

[Steve Ashby]

George Orndorf (who made many construction education videos in years past) recommended a light pass with a hand deburring tool after dimpling. Just a few light turns will do the trick. If you produce significant shavings, then you are doing too much. This method has worked well for me, producing nice flush rivetted assemblies. YMMV

[Av8torTom]

Hey Eric, do you use a DRD2 dimpler or the C-frame wack-a-mole method? IMHO the C-frame makes a crisper dimple resulting in a smoother final finish.

[aerhed]

I do that all the time when I want just a little more squareness. As stated, don't even cut through the alclad.

[Stewie]

Tom-
I've got a DRDT2. I suspect that some of the rivet line ripple is coming from the dimpling itself, in addition to the impact of the rivet gun...

Originally Posted by Av8torTom

Hey Eric, do you use a DRD2 dimpler or the C-frame wack-a-mole method? IMHO the C-frame makes a crisper dimple resulting in a smoother final finish.

[jimgreen]

I back riveted the last 2 skins on the rear fuse of my 7 . For me, c frame dimpling and back riveting has produced the best finish.
But don't forget you are not building a Glasair. Rivets don't have to look super smooth.

[Stewie]

Originally Posted by jimgreen

I back riveted the last 2 skins on the rear fuse of my 7 . For me, c frame dimpling and back riveting has produced the best finish.
But don't forget you are not building a Glasair. Rivets don't have to look super smooth.

At least once a day I have to (to quote someone else on VAF) tell myself: it's not a Swiss watch, it's an airplane...

[9GT]

Dimpling the hole twice with the DRDT2 give really nice results.

[clevtool]

Good dimple dies make all the difference in the world! If you take only .002" out of the dimple on .020" skin that is 10%. With good dies you won't have to take any out. If you are not using our dies, buy some, try them, if you don't think they are better than what you are currently using we will give you your money back including the shipping.

http://www.cleavelandtoolstore.com/products.asp?dept=48

[aerhed]

Mike, I've used dies from the worst (ATS) to the best (maybe yours). I'll match my rivet lines against anyone's. Loser buys dinner. Any takers?