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  #41  
Old 06-23-2012, 04:16 PM
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Pmerems Pmerems is offline
 
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Default Cracks in rivet head

Gents,

I believe the cracks shown on the rivet head are cracks in the anodization not the base material. The aluminum is very malleable, if it wasn't you couldn't form the shop head.
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  #42  
Old 06-24-2012, 01:30 PM
SledDog SledDog is offline
 
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Location: Lac du Flambeau, Wisconsin
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Default

Thanks to everyone who is posting on this topic. The information is invaluable. I am getting ready to assemble my fuel tanks and am experimenting with different combinations of dimple dies and assembly techniques before I do it for real.

So far, the combination that has produce the best looking results is spring back dimple dies on the skin and tank dies on the substructure.

I also sliced some of the samples to see what is going on under the rivets and was surprised by what I found. Here's a typical picture:



The porous structure of the sealant is evident, and it is very easy to see how leaks are going to develop if the shop head of the rivet is not sealed properly. After looking at this, I'm not sure how much added leak protection is provided by the sealant that is under the rivet.

In fact, it looks like the added sealant under the rivet may just temporarily mask a faulty shop head / fillet job that will end up leaking after a few hours service.

Please share any observations, insight, and experience you have. I'm trying to do this right.
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  #43  
Old 06-25-2012, 08:43 AM
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cka357 cka357 is offline
 
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Default Dimple Dies

Let me preface these images a bit:

0.032" tank skin material was used for the top skin.
0.025" rib thickness was used for the bottom skin to simulate rib thickness.

The top skin was formed with Cleveland's "Tank Die". The bottom skin was formed with Cleveland's "Sub-Structure Die". I used a red high temp sealant for contrast in the photos. You guys can be the judge. Multiple die combinations were tested and photographed. It appears that this combination provides support for the rivet head as well as room for the proseal. Also, the tank die did a good job in providing a sub flush rivet in the top skin. The combination of using a tank die for the top skin and the tank die for the bottom skin provided a pleasing result as well.

I hope this helps,

Chuck




Last edited by cka357 : 06-25-2012 at 08:51 AM. Reason: Images were not inserted properly into forum.
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  #44  
Old 06-25-2012, 09:31 PM
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Now we need the pratical load and cyclic reversal testing .....
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  #45  
Old 06-26-2012, 08:07 AM
SledDog SledDog is offline
 
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Default Thanks!

Chuck,

Thanks for posting the pictures and information. I ordered a set of substructure dies from Cleaveland and will give the tank die / substructure die combination a try. It looks like part of the secret sauce is to use a combination of dies that allows parts to nest better. Thanks again for the info.
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  #46  
Old 06-26-2012, 08:12 AM
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Quote:
Originally Posted by JanRV6UK View Post
Now we need the pratical load and cyclic reversal testing .....
I need an aspirin. Motoring along happy with my tank die dimpled tanks. I don't think they will be falling off the airframe anytime soon. Neat pictures really show what a dimple sandwich looks like. Cool!
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  #47  
Old 06-26-2012, 11:31 AM
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Quote:
Originally Posted by JanRV6UK View Post
Now we need the pratical load and cyclic reversal testing .....
Quote:
Originally Posted by JonJay View Post
I need an aspirin. Motoring along happy with my tank die dimpled tanks. I don't think they will be falling off the airframe anytime soon. Neat pictures really show what a dimple sandwich looks like. Cool!
Yeah...really.....experienced builders exploring esoteric stuff just for entertainment (or ego inflation ) is ok, but we have to consider the anxiety a prospective or novice builder is feeling when they read about joints failing or not developing sufficient strength because the "wrong" dies were used. I can also sympathize with Mike Lauritson (Cleaveland Tools) who sees business income jeopardized in a tough economy due to idle chatter tossed around on internet forums.

Thousands of tanks have been built with both types of dies and no evidence of problems due to standard or tank dies has been circulated in the vast RV community. Both types of dies can make good tanks. If there was an actual safety issue with tank dies we would have known about it years ago.
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Last edited by Sam Buchanan : 06-26-2012 at 11:37 AM.
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  #48  
Old 06-26-2012, 12:04 PM
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Quote:
Originally Posted by Sam Buchanan View Post
Yeah...really.....experienced builders exploring esoteric stuff just for entertainment (or ego inflation )..... If there was an actual safety issue with tank dies we would have known about it years ago.
Sam, cut the personal stuff....you know better. And anyway, who said there was a safety-of-flight issue?

In Key West since last Friday. I'm currently stuck south of TS Debby and away from my home computers (this is an FBO machine). More later.
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Last edited by DanH : 06-26-2012 at 12:07 PM.
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  #49  
Old 06-26-2012, 12:35 PM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by DanH View Post
Sam, cut the personal stuff....you know better. And anyway, who said there was a safety-of-flight issue?

In Key West since last Friday. I'm currently stuck south of TS Debby and away from my home computers (this is an FBO machine). More later.
Dan, I realize you aren't on your computer, but please don't use selective editing of my post. You chopped off my sentence where I stated "experienced builders exploring esoteric stuff just for entertainment (or ego inflation ) is ok, but we have to consider the anxiety a prospective or novice builder is feeling when they read about joints failing or not developing sufficient strength because the "wrong" dies were used.".

(Hope Debby is just an irritating memory soon and you can head homeward.)

And if there are no safety concerns about the tank dies, and if it is indeed just cosmetic concerns....then why all the fuss about joints not reaching design strength? The builders calling Mike aren't concerned about cosmetics, they are worried about structural issues.

Raising questions about structural strength may not have been the intention when this thread started (but there were the photos showing poor dimples and cracked rivets??), but that is certainly where it has resided for the past several pages.
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Last edited by Sam Buchanan : 06-26-2012 at 12:49 PM.
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  #50  
Old 06-26-2012, 07:47 PM
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JanRV6UK JanRV6UK is offline
 
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I am not at all worried about my tanks that I made with thank dies I bought from Cleveland - True I am not flying yet .. :-( ... But as Sam has pointed out ... thousands and thousands of miles have been flown with tanks made using this type dies.

I remember when the discussion was about anodised spars and fatigue life being cut in half due to the process of anodising. I also remember as a novice builder I worried about lots of things during the early build. Then over time you get more and more confident and you read and see a lot. I agree with Sam that it is a shame if Mike has to spend time answering calls from worried builders who has bought his dies, that is time that could be better spent designing new and better tools! After all, if tanks are not falling out of the sky, whats the problem ? Looking at pretty pictures of rivets cut in halves from tanks that has not failed ... what does that really tell us ?
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