N

N674P

Well Known Member
I ask because I'm about to dimple a tank skin, and I can't reach the forward most holes with a C-frame (DRDT-2), so I countersunk them. I can't (won't) C/S the whole skin, since I already dimpled the ribs, but it sure makes for a perfectly smooth surface! Would a wholly countersunk tank be strong enough?
On the one hand, the skin is plenty thick for countersinking, and then it would be "glued" (pro-seal) and riveted. On the other, you have the locking action of the dimples...
For those 10 countersunk holes I plan to flatten the rib dimples out tomorrow by squeezing with flush sets. Is there any reason I shouldn't, and would be better off leaving the dimple?
 
N674P said:
I ask because I'm about to dimple a tank skin, and I can't reach the forward most holes with a C-frame (DRDT-2), so I countersunk them. I can't (won't) C/S the whole skin, since I already dimpled the ribs, but it sure makes for a perfectly smooth surface! Would a wholly countersunk tank be strong enough?
On the one hand, the skin is plenty thick for countersinking, and then it would be "glued" (pro-seal) and riveted. On the other, you have the locking action of the dimples...
For those 10 countersunk holes I plan to flatten the rib dimples out tomorrow by squeezing with flush sets. Is there any reason I shouldn't, and would be better off leaving the dimple?
Click to expand...
If you've already countersunk the skin, I'd mash the rib dimple flat.
As an aside, I use a drdt-2 and had no problems at all reaching all the holes in the skins. I assume you had the male die in the ram and the female die on the anvil. That way the tank skin is dimpled with the outside of the skin facing upwards. The other way does cause a lot of interference with the handle.
-mike
 
I dimpled all the holes in the tank skin with the DRDT-2 with no trouble ... ditto on the male die on the top...

Thomas
 
work bench dimple machine

I had a few that I couldnt reach on different skins so what I did was drill a 3/16 hole in my particle board work bench and then I stuck a the male die in it and I had a piece of 1/2 round stock with a 3/16 hole in it line it up and hit it with a hammer worked good. I also had the pop rivit dies for some hard to get to areas

Jim Knight
Burlington Iowa
RV-6
130 hours
 
Tank Dimple Die

I'm getting close to dimpling my tank ribs and skin. I bought new tank dimple dies and would like your experience to confirm that I should use this die set for both the skin and the ribs.
 
Speaking of Tank Dies

Bob Avery of Avery Tools took a tank die and welded it to a set of vice grips for me. I use this for that little extra indentation on the underside of flaps and related ribs for areas that require blind rivets. This helps the rivets sit flush to the skin. I have heard others just ream the hole a little.
 
Johnny,
A thread I posted a few weeks ago illustrates an easy way to access the forwardmost holes on the fuel tanks with the dimpler.
http://www.vansairforce.com/community/showthread.php?t=13700

That said, because the tank skins are .032 I DID machine countersink the upper surfaces of the fuel tank skins on my 6A. I took a slightly different tack using a rivet shaver because .032 is barely thick enough to accept a machine countersink. http://www.vansairforce.com/community/showthread.php?t=2322
 
Talking to a guy two did CS some of his skins, he told me not too. After 1000hr or so, they started smoking a little and stuff. Looked realy good initially though. I therefore won't be CS any of my skins.
 
Tank Skins...Dimple or Countersink

I rebuilt a wrecked 20year old RV4 that had all machine counter sink rivets including the tanks. The original workmanship was good but 1400 hrs & years of Alaskan gravel strips did take its toll but the wings & tanks did escape the accident damage. The tanks had leaks from the cs rivets and as soon as I fixed one another appeared somewhere else. All appeared to be of the same cause which is the cs holes did not have enough rivet grip surface to seal with the proseal. Some of this could have been caused by the accident as the entire airframe always takes a shock on impact but this had no visible effect on these wings. A dimple with a set rivet coated with proseal would have held better. Now, the vast majority of rivets did hold well even though cs but a small percent were definitely a headache and they are still problematic a year later. On my own RV I have and will dimple EVERY tank rivet.

I would use the pop rivet dimple dies or even a piece of steel drilled slightly oversize and countersunk with a drill bit as a female die and an actual rivet as the male die. Next drive the rivet into the homemade steel die with your flush rivet set in the air hammer. Remove the rivet from the slightly over size hole (also drilled deeper than the rivet length) and you now have a dimple hole where you cannot reach with other methods. If you feel the hole is not good enough you can lastly run the cs bit in the dimple which should remove a few thousandths of the metal but still leave a good amount of surface. Try this with some scrap first but it works surprisingly well.

Dick DeCramer
N500DD RV6
N149KC RV4
Unnamed RV8 wing kit
Northfield, MN
 
Rick6a said:
A thread I posted a few weeks ago illustrates an easy way to access the forwardmost holes on the fuel tanks with the dimpler.
Click to expand...
Thanks Rick - I saw that thread after I posted this, and I'll know what to do next time!
osxuser said:
Talking to a guy two did CS some of his skins, he told me not too. After 1000hr or so, they started smoking a little and stuff. Looked realy good initially though.
Click to expand...
I'll bet if you wanted a show plane that would last, machine countersink with a thin smear of ProSeal on the ribs would look good, and last a long time.
 
Tank Skins...Dimple or Countersink

I rebuilt a wrecked 20year old RV4 that had all machine counter sink rivets including the tanks. The original workmanship was good but 1400 hrs & years of Alaskan gravel strips did take its toll but the wings & tanks did escape the accident damage. The tanks had leaks from the cs rivets and as soon as I fixed one another appeared somewhere else. All appeared to be of the same cause which is the cs holes did not have enough rivet grip surface to seal with the proseal. Some of this could have been caused by the accident as the entire airframe always takes a shock on impact but this had no visible effect on these wings. A dimple with a set rivet coated with proseal would have held better. Now, the vast majority of rivets did hold well even though cs but a small percent were definitely a headache and they are still problematic a year later. On my own RV I have and will dimple EVERY tank rivet.

I would use the pop rivet dimple dies or even a piece of steel drilled slightly oversize and countersunk with a drill bit as a female die and an actual rivet as the male die. Next drive the rivet into the homemade steel die with your flush rivet set in the air hammer. Remove the rivet from the slightly over size hole (also drilled deeper than the rivet length) and you now have a dimple hole where you cannot reach with other methods. If you feel the hole is not good enough you can lastly run the cs bit in the dimple which should remove a few thousandths of the metal but still leave a good amount of surface. Try this with some scrap first but it works surprisingly well.

Dick DeCramer
N500DD RV6
N149KC RV4
Unnamed RV8 wing kit
Northfield, MN
 
I just dimpled a 9A tank skin tonight - worked well with the DRDT-2. I'm not sure why you have a problem.
 
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