Fuel Tank skins: dimple or countersink?

N674P · #1 11-13-2006, 05:42 PM

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?

mlw450802 · #2 11-13-2006, 05:55 PM

Quote:

Originally Posted by N674P

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?

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

bullojm1 · #3 11-13-2006, 06:25 PM

A pop rivet dimple die set works well in these hard to reach spots:

https://cart.averytools.com/pc-24-20...t-dimpler.aspx

TShort · #4 11-13-2006, 06:27 PM

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

N24YW · #5 11-13-2006, 07:18 PM

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

dbuds2 · #6 01-21-2007, 05:24 AM

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.

TShort · #7 01-21-2007, 05:37 AM

I used them for both the ribs and the skin and all turned out well.

T.

beechrv9a · #8 01-21-2007, 07:53 AM

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.

Rick6a · #9 01-21-2007, 08:15 AM

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/communit...ad.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/communit...ead.php?t=2322

osxuser · #10 01-21-2007, 11:37 AM

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.