R

rwshooter

Well Known Member
I'm about to countersink the tank skin to baffle fit on my 7A fuel tank. Should I go a couple thou deeper to allow for the proseal? It would seem to coincide with the logic of using fuel tank dies. right?

Robb 7A
 
If I had it to do over I would.

Several of my rivets on the baffle will need to be shaved before paint due to them being proud of the skin.
 
Robb,

Here's one data point...I didn't go any deeper than recommended by Vans. IIRC, the skins are 0.032", which is the bare minimum for countersinking to accomodate an AN426 rivet. My skin-to-baffle rivets actually sit a little proud because of proseal, and I figured that was better than making deeper countersinks.

There's some good information in this thread...

http://www.vansairforce.com/community/showthread.php?t=2322

about your question.

Hope this helps,

Dave
 
I did, and probably would go a little more still if I did it again...can't tell you precisely how many more thousandths, but I did increase the depth a few...
 
Im afraid of violating the .032 rule Dave thats why I'm asking............but if there is proseal in there do you think it would really matter.....

Brian...... I've never heard of a rivet shaver I dont think.......I remember having to sand down a couple of blind rivets on the emp during fiberglass work....they came out just fine.....but they are under glass work..../so no biggie............so if I get some proud rivets, this rivet shaver will take em down before paint?
 
This is interesting, I dimpled all mine, with proseal on all the rivets. Is this wrong, I don't think so. I know this has been talked about before and I was told this is wrong. But it says in the manual, not the plans, to dimple all tank skins. So I did. It looks good and it doesn't leak. I think dimpleing is stronger and less chance of a crocked hole, or a line in the hole for a leak. I'm not reduing mine, they stay the way they are. I even remember reading one of the tool suppliers having a dimple die for tanks to make the rivet set lower for proseal.
 
I think we are talking about the skin to the baffle rivets. I also dimpled all the others.
 
I didn't on my first tank, and most of the rivets ended up a little proud. I went slightly deeper on the 2nd tank and it came out perfectly.
 
Yes, go slightly deeper

I just did my skin holes for the baffle and I made the countersinks so that the rivets were flush or even slightly indented, but after riveting with Proseal, I have many that are slightly proud and I'll have to smooth them off later. You can see them at mykitlog/sglynn
 
On my 9A, I countersunk the main skins for the baffle rivets in the .032 skin per directions. For my auxiliary outboard tanks, the skin is .025 so I dimpled them with the tank dies. The rivets set beautifully in both, and I will be pressure testing them this weekend. I'll keep all here advised.
 
Brantel said:
I think we are talking about the skin to the baffle rivets. I also dimpled all the others.
Click to expand...

yup, those are what I'm talking about, the only ones I didn't dimple was the trailing portion of the baffles for the last piece to close the tanks, all other parts were dimpled.
 
On my directions for the main fuel tank, it says to countersink those skin-to-baffle rivet holes rather than dimple, as dimpled holes would make it difficult to insert the baffle after the ribs had been riveted. On my auxiliary tanks, I could not countersink them since they were too thin, so I dimpled them and figured I would just have to fight with the baffle when I was closing the tanks - but it was no fight at all! The baffle slid right into place (lubed up with proseal) with only a small bit of coaxing. Given this, I don't see the necessity of countersinking versus dimpling for that rivet line. With the standard .032 skin you have the option to go either way.
 
I believe the other reason they want you to counter sink is that if you dimpled here, the shop head of the rivet would acutally hit the spar when you install the tank. At the root end the spar reenforcements are as thick as z brackets. (on a 7 anyhow).
 
I ended up dimpling both of my tanks. The first one was a mistake, so I did the same to both. No leaks and no problems either installing the baffels or on to the wing.
Rick Maury
RV7 SB
Tail Wings done, Aft fuselege in the mock up stage.
 
Same for me. I dimpled in error but found it works great and for my taste is more esthetic. With proseal it slid in like a dream and the dimples located it positively. Some machine countersunk tanks I've seen end up with slightly tilted rivets. There seemed to be no reason not to dimple.
 
airguy said:
On my 9A, I countersunk the main skins for the baffle rivets in the .032 skin per directions. For my auxiliary outboard tanks, the skin is .025 so I dimpled them with the tank dies. The rivets set beautifully in both, and I will be pressure testing them this weekend. I'll keep all here advised.
Click to expand...

Promised an update on the fuel tank pressure test with regard to the difference of dimple dies versus regular dies, and dimpling versus C/S on the skin-to-baffle rivet line - here it is - all the driven rivets sealed just fine on both tanks, whether dimpled or countersunk. I like the idea of full-strength material for the rivet lines, so I believe I will dimple both my left tanks.

I had one leak, coming through the stem hole in one of the blind rivets used to attach the Z-brackets on the back of my main tank - my fault because I trusted the sealed head of the blind rivet to stay sealed - which it did not. The sealed head must have cracked when I pulled the rivet, because the air was most definitely coming up through the stem hole, not around the head of the rivet. All the pulled rivets on my left tanks will receive a generous dollop of proseal on the external head after setting. Feels good to have two good tanks done - now just two more to go!
 
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