Lionclaw

Lionclaw

Well Known Member
Another local builder let me borrow his tank dimple die, and showed me a problem he was having. I dimpled a few scrap pieces in order to get a picture.

tank_dimple.jpg


You can see in the picture there is a gap between the stiffener and the scrap of about 1/16". Is this common? I can't imagine that we're supposed to fill the gap with proseal, are we?
 
This may sound silly, but did you dimple both pieces with the same set of dimple dies?. The two parts should fit together without any gaps, just like any other dimpled parts.
 
Somthings amiss there, should seat just like any other matching dies...the tank set is just a tad bigger (engineer term, T.A.D., thousandths and densum;)) to allow proseal to get in around the head...and let the flush portion remain "flush". I used them on my tanks...not sure if I would again but heck I have them now. Make sure the person who gave them to you didn't get them mixed up with his other #40 dies.
 
What did you put the dies in?

If using a C-frame did he just whack it once really hard or did he do the tap-tap-tap method? If he squeezed them, it should be done with one swift motion and the dies should be adjusted so the dimpler handle closes completely.

Basic stuff but you never know...
 
I don't believe the dies have been mixed up. They fit into each other very well, and both appear to be of the same make. A rivet dropped into the dimple sinks in so that the top of the head ends up about 0.025" below the skin.

I did the dimpling with the pneumatic squeezer. They were done quick, hard and straight. The other builder used his drdt2 with the same results. Both parts were done with the same set of dies.

My other dies are from Avery, and I haven't had any problems like this. At this point I'm wondering if they could be defective, or perhaps mis-matched by cleveland.
 
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Just looked at the picture again...is that stiffener material completely flat or is the test strip bowed? Your clecos may not have the gusto to pull the pieces together. Try a test piece with with some different stock, say two 1" squares...see if you get the same result.
 
Cleaveland Dies

Cleaveland dies are engraved with the part #; in this case it should read "CAT 426-3T" on both the male and female dies.

Cleaveland dies have a lifetime warranty and no restocking fee...if in doubt, call them.

Mike
 
Transporter said:
Cleaveland dies are engraved with the part #; in this case it should read "CAT 426-3T" on both the male and female dies.

Cleaveland dies have a lifetime warranty and no restocking fee...if in doubt, call them.

Mike
Click to expand...

And they put out some really well made dies along with other quality products. That's why I thought they may have mixed a standard with the tank set.
 
I just went and did two more practice pieces. One was two ~1" squares and the other was another strip of stiffener with a piece of scrap. These came out slightly better, but I can still see light coming through between the two pieces.

I also checked the markings on the dies, CAT 426-3T on both.

At this point I'm wondering if it might be best to just use the regular dies.

Any other input you guys have is appreciated.
 
Well many hundreds of tanks have been built with the standard dies...I really couldn't see a difference between my tanks and fellow RV-10 builders who didn't use the dies...still...I'd call Mike at Cleaveland and see what he thinks...I really like those guys, if you can wait I'll bet they will send you a new set to see. They are over $30 a set...should get your money's worth, or your friends money's worth. Have you tried riveting them to see if the gap lessens/closes all together?

This is one of those times you wish you could walk over and take a look see and play with the all the stuff to see what's happening.
 
On Gaps

Andy,
You shouldn't have any gaps; I wouldn't count on rivets pulling things tight...in my limited experience, riveting never improves a bad fit.

I'll second Rick's comment-call Cleaveland (515-432-6794 or 800-368-1822) or email [email protected].

Mike
 
Lionclaw said:
I did the dimpling with the pneumatic squeezer. They were done quick, hard and straight. The other builder used his drdt2 with the same results. Both parts were done with the same set of dies.
Click to expand...
The tank dies should be used only for the bottom part (angled piece) and the top (sheet in your case) should be done with regular dies... :confused:
 
Pirkka said:
The tank dies should be used only for the bottom part (angled piece) and the top (sheet in your case) should be done with regular dies... :confused:
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You use them as any other die, they are just a tad, "little bit"...(see previous post regarding T.A.D) larger to allow the rivet to sit flush versus high when Proseal is introduced into the process.
 
Tank Skin Die produces space between skin and rib

The Cleveland Aircraft Tool website has this to say about the Tank Skin Dimple Die Set for 3/32" Rivet:
  • Tank dies make deeper dimples to allow for the layer of tank sealer between the rivet and skin.
Note that the Tank Skin Dimple Dies are for the tank skin only. The rib is dimpled with the regular die. The deeper skin dimple results in a space between the skin and the rib to allow for the layer of tank sealer.

The gap you are seeing in the photo of your test pieces looks exactly like what they are describing.
 
Rick S. said:
Somthings amiss there, should seat just like any other matching dies...the tank set is just a tad bigger (engineer term, T.A.D., thousandths and densum;)) to allow proseal to get in around the head...and let the flush portion remain "flush".
Click to expand...

Possibly a dumb question, but did you dimple both parts with the tank die set------- if the dimple is a "tad" larger, you would have to use the same die set for all parts to be joined. If you used the tank die for the skin, and a regular die for the rib----then things would sit up just like in your photo.
 
It's not a problem, it's the objective

Mike S said:
--- If you used the tank die for the skin, and a regular die for the rib----then things would sit up just like in your photo.
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And that is exactly how the tank dimple dies are supposed to be used. The objective of using the tank dimple dies is to create space for the sealant between the skin and the rib.
 
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I went ahead and called Cleaveland this morning. They said for the tank parts both pieces should be done with the tank dies. Elsewhere on the airplane, you can use the tank die on the substructure and a regular die on the skin to make better fitting dimples.

They said the tank dies should produce dimples that fit just as well as those made by regular dies. The analogy of a stack of cups was suggested, where one cup doesn't fit perfectly into another, and that any space left between the pieces should be taken up once a rivet is installed.

The last batch of test pieces I did came out pretty good, although I didn't set rivets into them. I think part of the problem with my first test piece may have been due to misalignment.

If I continue to have problems I'll report back.
 
5000+ flying RVs!!

Okay guys, there are over 5000 flying RVs currently. This seems pretty basic, but now there seems to be some question on the proper technique.

Dave, you mention tank dies only on the outer skins and regular dies on the substructures. I understand your reasoning, but did that technique come from someplace "official"? Did everyone else or anyone else do it this way also?

It just seems to make more sense to me to have matching dies for both sets of dimples...regardless of Proseal.
 
My wife and I just had our first experience with the black death. We installed the stiffeners and the drain fitting.

Going with the tank dies on the skin and stiffener really didn't work well for us. After back riveting a few, we found that the rivets were flush with the skin, but the dimple was too big and left space between the rivet head and the skin.

I can understand the theory that sealant would get between the rivet and the skin, but that wasn't really happening for us. After the problem with the first few, i took the rest of the rivets out and purposely put some sealant in the dimple before riveting the rest. They all look fine now, just with small circles of sealant around the head.

I'm going to redimple the rest of the skin with the regular dies and see how that goes. I think doing the substructure with the tank dies makes more sense, as the sealant should be between the two parts, and not necessarily between the rivet head and the outside of the skin.
 
Perhaps try some test pieces before trying something new on your tanks. The tanks I helped rivet, the heads would stand proud with regular ties. It sounds like you were'nt putting sealent in the dimples before installing the rivet? You defintaly need to, or put a blob under the rivet before you insert it. Every surface of metal that mates should have a layer of sealent on it. After you buck or squeeze the rivet, run a rag moist with MEK or laquer thinner over the outside of the rivet line and the proseal should all clean off.

Lionclaw said:
My wife and I just had our first experience with the black death. We installed the stiffeners and the drain fitting.

Going with the tank dies on the skin and stiffener really didn't work well for us. After back riveting a few, we found that the rivets were flush with the skin, but the dimple was too big and left space between the rivet head and the skin.

I can understand the theory that sealant would get between the rivet and the skin, but that wasn't really happening for us. After the problem with the first few, i took the rest of the rivets out and purposely put some sealant in the dimple before riveting the rest. They all look fine now, just with small circles of sealant around the head.

I'm going to redimple the rest of the skin with the regular dies and see how that goes. I think doing the substructure with the tank dies makes more sense, as the sealant should be between the two parts, and not necessarily between the rivet head and the outside of the skin.
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