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  #11  
Old 02-05-2007, 01:43 AM
rv72004 rv72004 is offline
 
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Vans has been promising to speak to their supplier to get me the facts. I have been patiently waiting for a answer ,but none yet. The clearly told me they mixed it correctly and that it was my fault it went soft.[fuel shouldnt leak on it]

I dont want to make a issue about it, but feel a bit short changed at the moment. Vans has always been great about sorting out issues. I wonder why they are avoiding this one ??
As I said before, if its my fault ,so be it. However everyone I speak to says its not, and Vans doesnt seem to agree.
What should I do ?
EJ

ps if I could figure out how to post pictures I could show how it looks.
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  #12  
Old 05-21-2011, 09:43 PM
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TroyBranch TroyBranch is offline
 
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Any result on this? The rv10 in am working on has had a fuel leak and the pro seal is all soft where the fuel has run on it. Going to drain the tank tomorrow and investigate where it is leaking. The plan was to clean it up and spread fresh pro seal over the area. The leak could end up being just the fittings. The pro seal is fine where the fuel is not on it, so it seams like vans could be right. Strange that that would be the case though.
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  #13  
Old 05-22-2011, 08:52 AM
Wayne Gillispie Wayne Gillispie is offline
 
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Default I always buy prc proseal from acs

You get what you pay for. Vans is all about saving us a few dollars. I also used only 5052-O tubing.
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  #14  
Old 05-22-2011, 06:33 PM
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TroyBranch TroyBranch is offline
 
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After cleaning up the soft pro seal today, the only area that was soft was where fuel was running onto the pro seal and sitting. As soon as I got out of the blue stain area the stuff was fine. I do not see this as an improper mixture of the product as the area would have all been placed at the same time. The product deffinately does not hold up to fuel and air at the same time. Pretty strange as there are lots of this kind of a situation inside the tank, but never an issue I have heard of in there. I assume that the line of fuel and air is constantly changing so it does not have enough time to do anything. Not sure why the stuff vans sells would be any different than the prc that is sold elsewhere. The key, keep up your maintenance and inspect everything regularly. If you have a leaky fitting fix it ASAP. I am amazed at all the problems I am finding on this import.
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  #15  
Old 05-22-2011, 07:12 PM
mbetti mbetti is offline
 
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So i wonder what is going on inside my fuel tank of the airplane i have sitting in my hanger for the past month unmoved, that is at the level line? Wouldn't this be the same problem?
Mike
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  #16  
Old 05-22-2011, 08:38 PM
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TroyBranch TroyBranch is offline
 
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Quote:
Originally Posted by mbetti View Post
So i wonder what is going on inside my fuel tank of the airplane i have sitting in my hanger for the past month unmoved, that is at the level line? Wouldn't this be the same problem?
Mike
Not flying for a month, your poor airplane. I wish I knew.


I may just test that. Put some pro seal on the side of container and pour fuel in so there is a line to the pro seal. Then check it every month to see if it starts to deteriorate the pro seal at the "line". Maybe it takes six months? Maybe it only does it of there is a small film of fuel weeping on it. I always liked science projects as a kid.
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  #17  
Old 05-23-2011, 07:58 AM
David-aviator David-aviator is offline
 
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Quote:
Originally Posted by mbetti View Post
So i wonder what is going on inside my fuel tank of the airplane i have sitting in my hanger for the past month unmoved, that is at the level line? Wouldn't this be the same problem?
Mike
The inside of the tank probably has a lot more fuel vapor than oxygen. Could be there are not enough O2 molecules to support what goes on outside the tank when 100LL drips on the exposed sealant in an O2 rich environment, well at least relatively rich at 16-17%. It is much less inside the tank.

I've read the tech data supporting the tank sealant we use and it says nothing about its properties outside the tank. Inside the tank it is quite durable.

I have also experimented with "thinning" the stuff with MEK. It got thinner but as soon as the MEK evaporated, it was back to its original stiffness. I did not use it on the tank. I also figured out the stuff we use is Class B, designed to be applied with a gun or popsicle stick, it won't run or sag. The same product comes as a Class A which is a brush-able material... I am certain that is what was used building my QB tanks in 2002. It will run and sag.
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  #18  
Old 05-23-2011, 08:27 AM
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DanH DanH is offline
 
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There was a good bit of discussion about this particular issue, both here and elsewhere, back in 09. I'm not aware of any clear explanation.

Basics.....this from a very qualified individual who is not allowed to speak online:

.....the liquid pre-polymer molecules each contain 2 or 3 SH-groups (sulfur-hydrogen). SH groups in each molecule react in the presence of a peroxide (contains oxygen), split out water, and form an S-S bond (sulfur-Sulfur). This produces the chain extension or crosslinking. The curing agent (catalyst-accelerator) in the case of common aerospace sealants is manganese dioxide (MnO/2).

.....the following reference is suggested: Concise Polymeric Materials Encyclopedia, Joseph C. Salamone (ISBN 9780849322266)


A VAF contributor located a technical paper linking elastomer deterioration to peroxides. However, a careful read of the polysulfide sealant conclusions finds:

....From the available data it is uncertain whether catalyzel oxidation or acid catalyzed hydrolysis at the formal linkage is the primary degradation process. The latter mechanism is favored....

The manufacturer's rep discounted peroxides, but did report sensitivity to paint strippers.

Just of the heck of it I mixed sealant samples in correct and incorrect proportions. After cure, three samples were immersed in a 50/50 mix of MEK and lacquer thinnner. A fourth was immersed in ordinary drugstore 3% hydrogen peroxide. They've been there a long time now (since 11-16-09); none show any obvious change, certainly not reversion to goo. I am a chemistry idiot, so I'll leave conclusions, if any, to others. For sure 3% peroxide will reduce a new paint can to rust:



FWIW, there is no specification requiring the manufacturer to test sealant in avgas. The test fluid is called "JRF", for "jet reference fuel".

Nobody has ever offered evidence (a chemical process, physical mechanism, a measurement or test) to validate the "dripping avgas" theory. We can safely assume most of the avgas components evaporate, and thus concentrate the remaining component(s). That remaining component should be obvious if someone would simply hire a lab to run a softened sample through a GC/MS for comparison to a good sample.

Or you can debate a few more years
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Last edited by DanH : 05-23-2011 at 08:39 AM.
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  #19  
Old 05-23-2011, 09:59 AM
algrajek algrajek is offline
 
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I must agree. It is NOT a Proseal problem.
I had the same thing happen on my old 8. Where the leak was present for almost a year, the sealant became very sticky. Upon opening up the tank, ALL of the proseal on the inside was just fine. the only place it softened up was right where the leak was, so I have to Defend Vans on Their Answer.
Nordo
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Last edited by algrajek : 05-23-2011 at 10:00 AM. Reason: mis spelling
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  #20  
Old 05-23-2011, 10:16 AM
asav8tor asav8tor is offline
 
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ASSUMING the tank seal used was MC 236-B2, the black part is oxygen accelerator. It speeds up the process of hardening the white part, which when EXPOSED to air would eventually harden on its own without the the black part.

Once the seal is hard oxygen or the lack of it does not soften it. Once hard, the accelerator or mix does not matter. This is not epoxy.

Vans statement that the dye without fuel attacks hardened seal could in fact be true. I doubt oxygen has anything to do with it. Oxygen is what cures the seal in the first place. Perhaps if you filled the tank with 100% blue dye used in Avgas all the seal would melt. The dye while suspended in 100LL might not be strong enough to attack.
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