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Tank Leak and Green Peanut Butter

Fuel Tank Repair

The Fuel tank repair looks great!

Would have been a great time to do the Service Bulletin :(
http://www.vansaircraft.com/pdf/sb06-2-23.pdf

TankSB.jpg
 
I believe that the line of sealant on the bottom exterior of the rib shown here, would have been better if applied to the inside of the tank while you had the access cover off.

DSC00257.JPG
 
Maybe too late for you, but I covered the nutplates on the inside of the sender with proseal (and I mean completely covered) as added insurance.

Greg
 
You must have done something wrong...

because your resealing job looks too clean and tidy.

GOOD JOB

Steve Barnes "The builders Coach"
 
Why would fuel leaks turn Proseal into a gooey mess, as described? It IS supposed to seal the fuel in after all.

Also, in past threads it has been recommended to let the Proseal partially cure for 24 hrs before placing the cover plate back on, installing the screws, and letting it fully cure. For next time, I guess.

Erich
 
Why would fuel leaks turn Proseal into a gooey mess, as described? It IS supposed to seal the fuel in after all.

Erich

That is what I was wondering. Bad batch of proseal? Out of date proseal? Poor mix ratio? Ethanol in the fuel?

If fuel will turn the proseal around the sender plate to goo, it'll do the same to the proseal that forms the fillets on the ribs and seals the rivets. That's a nasty thought.
 
I can live without it if need be as the general consensus is that's a lawyer contrived CYA SB anyway. With my luck, the tank will probably leak and I'll have to go back in anyway...
I recently had to have my left tank resealed due to a very similar problem - I made the same decision re: the SB. I openly disclose that in the For Sale posting I have for my RV-6 and it may be affecting resale value - no one seems to call back after reading the spec sheet.
 
Sender Ground

You might consider adding a fuel tank level sender ground wire as you're reassembling the tank to the wing. At least check the continuity between the tank sender flange and the airframe. If no continuity add a ground wire between one of the screws of the tank sender flange and an inboard Z bracket AN3 attach bolt.
 
I can tell you three years submerged in ordinary household hydrogen peroxide solution hasn't degraded a Flamemaster sealant sample.

I am not a chemistry person.
 
I'll be curious to read the results once you're back in operation -- particularly since you did not use any gaskets. I am chasing a similar leak in my RV. I suspect the leak is coming from the rubber gasket around the sender, but I'm debating whether or not to remove the T408 access plate as well while I'm at it.

My real dilemma is whether or not to just replace the standard cork gasket on the access plate and the standard rubber on the sender per plans or do something different. On my existing setup, the rubber gasket for the sender seems to mushroom out when I tighten the screws and the screws never seem to be really tight. An A&P friend suggested that no lubricant be placed on the this rubber seal as it weakens the gasket.

An alternative I suppose would be to use a cork gasket for the sender as well.

So please let us know how your setup works. I'll be watching.

Chris
 
My real dilemma is whether or not to just replace the standard cork gasket on the access plate and the standard rubber on the sender per plans or do something different. On my existing setup, the rubber gasket for the sender seems to mushroom out when I tighten the screws and the screws never seem to be really tight. An A&P friend suggested that no lubricant be placed on the this rubber seal as it weakens the gasket.

Hey Chris, I'm on airplane number 2 with no gaskets for either the access plate or sensing unit - just pro-seal. When we removed the sending unit the other day, it took about five minutes to get it off the pro-seal after taking the screws out. No leaks - ever.

I had the same problem with the mushrooming gasket when I tried it the first time on my -8. Others said "no gaskets", so I tossed them in a box and never looked back....

Paul
 
There has been some discussion in the past about proseal softening when exposed to fuel and an oxygen source, as would be the case in a slow seeping leak. It was covered in the great tank rivet blister debate some years ago.
http://www.vansairforce.com/community/showpost.php?p=366342&postcount=260

You can count me amongst the true belivers after seeing the gooey mess on my tank.

MC
MC

I wonder if we're just seeing the result of sealant that is mis-mixed here. I suspect that a batch that is under catalysed might be more prone to degrading.

You'd think someone here would have a good bead on this.
 
Hey Chris, I'm on airplane number 2 with no gaskets for either the access plate or sensing unit - just pro-seal. When we removed the sending unit the other day, it took about five minutes to get it off the pro-seal after taking the screws out. No leaks - ever.

I had the same problem with the mushrooming gasket when I tried it the first time on my -8. Others said "no gaskets", so I tossed them in a box and never looked back....

Paul

Thanks Paul, that really helps. I'll follow your lead.

Chris
 
I can live without it if need be as the general consensus is that's a lawyer contrived CYA SB anyway.

I very much doubt that there's any consensus (everyone agrees) that the SB is a lawyer contrived SB. I believe it is a fundamental safety issue that was addressed by Vans in good faith following the identification of specific failures. But whatever makes you feel good. ;)
 
I missed something

I may have missed another post somewhere, so I may be missing some context. But I love the idea of Dan testing RV components for their compatibility with peroxide. Rockets are awesome, but this is something completely different.

Who is going to put the first RV in space?
 
David,
I don't think it was a bad batch of sealant or mis-mixed sealant. The proseal around the screws and parts of the cover plate that were not leaking were normal. Where the fuel had been leaking and where it had pooled around the bottom of the tank the proseal was goo. I can't imagine that the guy that built the plane used 2 different batches of proseal in random areas of the tank cover plate.
MC

Hmmmm
Hard to say what going on here.
 
I let the proseal cure and tested, no leaks! This weekend we reinstalled the tank. Pulling and reinstalling the tank was no big deal. I originally thought it would be. It made it much easier get to everything and do a neat job and properly test the tank. There is just so little room to work with the tank still on the wing. I'm not saying that you could not do it with the tank on the wing, just that it made things much easier with the tank off. Especially with the gooey mess I had to deal with. TJ (my wife) is a teacher and spring break starts next weekend. Time to plan a trip somewhere. We are probably going to go up to Columbus and watch Team RV perform again, but that's just a day trip. Any other ideas?
MC

DSC00268.JPG

Now that is a good looking plane with a diligent owner as it is tied down in the hanger.

Good job with the fixing the leak.
 
I wonder if gooey proseal is causing paint blisters

Very nice job on the repair.

There is another thread(s) where the top surface of painted gas tanks are getting blisters around the rivets. Could gummy proseal be the culprit or has that mystery been solved?
 
I think the rivet blister thing is a whole different issue and that the jury is still out on that one......What I came away with from that thread was that some QB tanks built in or around 2005 had the issue.

Quick fact correction....blisters are not just a QB tank problem. Blisters have appeared on QB tanks from the PI contractor, kit tanks built by individual builders, and kit tanks built by a qualified US professional.
 
Dan,
So was there ever "generally agreed upon" cause?
Mardy

The Mooney folks have been dealing with this for years. I think the bottom line is that all "wet wing" tanks will eventually leak. The causes might be inadequate prep work, too little proseal, bad fuel, mechanical failure (vibration, loose rivets), or just the luck of the draw.

By the way, the Mooney folks pay $7-8k for a "Strip and reseal" job. Ouch!
 
If an ag plane doesn't leak fuel, it's not an Air Tractor!:)

Every annual, mine has to have added proseal.

Best,
 
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