S

Stewie

Well Known Member
Patron
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
 
A light pass with a deburring tool works well.

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
 
How did you dimple?

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


Av8torTom said:
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.
Click to expand...
 
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.
 
jimgreen said:
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.
Click to expand...

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...:D
 
Dimpling the hole twice with the DRDT2 give really nice results.
 
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
 
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?
 
Stewie said:
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
Click to expand...
Are you absolutely sure that it was *only* countersunk (not dimpled 1st)? If it was, I don't think I'd want to fly in the plane; there wouldn't be much metal under the head of the rivets.

I was taught that if you use 'springback' type dimple dies, and use enough force to create the dimple, they can look (I won't say perfect) pretty good. Too little force when creating the dimple (whether squeezed or 'hammered' in a C-frame) leaves the edge of the dimple with a rounded edge and the rivet then sits 'proud' of the skin surface. I don't expect the -7 I'm building to win any awards, but I've had complements on smooth rivets from several who have completed & flown RV's. I was fortunate to learn from those who had already been there, done that, & it seemed to pay off for me.

Another trick I *didn't* discover until near the end of riveting: if a rivet seems to sit 'cocked' in the hole, with one edge up, it can usually be corrected by placing a female dimple die in a drilled bucking bar, placing the die over the tail of the rivet (prior to actually setting the rivet), and then hitting the rivet with a few light strokes of the rivet gun with the regular mushroom set. This seems to 'realign' the skin & structure dimples, allowing the rivet to sit flush.

FWIW,

Charlie
 
Yup Mike is right!

clevtool said:
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
Click to expand...

I build with Cleaveland Dies and sell them through our store too.
The best I've seen without a doubt.

Mike even made a friend of mine and myself a special set for -5 shear head countersunk Hi-lok's, they worked perfect too!

Go Cleaveand!
 
rv7charlie said:
Are you absolutely sure that it was *only* countersunk (not dimpled 1st)? If it was, I don't think I'd want to fly in the plane; there wouldn't be much metal under the head of the rivets.
Click to expand...

FYI, the Vans builders manual (at least the very old copies like mine) state that the horizontal stab skin can be dimpled or countersunk. There are probably a lot of RV 3,4,6 out there with countersunk skins. Heck, you may have even flown in one already.
 
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