Kelly McMullen
Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ
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 Posted: Wed Sep 22, 2021 1:22 pm Post subject: Tank Leaks |
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My experience from owning a Mooney for 18 years before the RV build: The version of sealant used 50 years ago is very different from what Vans specifies and supplies.
With current Pro-seal or other brand mil-spec equivalent, shocks are very unlikely to cause a leak. If you have ever had to remove the stuff, you will know what I mean.
On the other hand, if the skin isn't perfectly clean, as in no fingerprints, no other contaminants; the adhesion can be imperfect. Vans only specifies and uses in the quick build wings the B-2 compound. Mooney on the other hand specifies a layer of B-2, a layer of A-2, and a sealer on top of that. I've seen leaks in relatively new Mooneys, even with those extra layers.. I fully stripped and cleaned a Mooney tank (a nasty job) and resealed it. After 9 years and several hundred hours it was leak free. One of the tough requirements of any of the Pro-seal compounds is the number 2 means it is supposed to have a 2 hour pot life at 75 degrees. IMHO, you will be lucky to go 1 hour before it starts getting tacky and doesn't want to spread smoothly. While I used cartridges and a pneumatic gun on the Mooney, with the RV, I would mix only enough to cover what you can rivet in 30 min, then make a new batch. After application let it cure minimum 2 days and preferably double that.
Mooney main gear is attached directly to the wing spar that serves as the back of the fuel tank. Doesn't matter how hard you land, if it doesn't damage the gear, it won't cause the tank to leak either. That wasn't true with the 50 year old gunk that got hard, dry and brittle. The current Proseal does not harden beyond the initial cure. It stays flexible, and it takes a lot of force to make it separate.
So either there were contaminants on the skins going together, or a gap in the sealant as it was applied. Personally I would use B-2 followed by a brush coat of either A-2 or thinned B-2 spread at least an inch beyond the B-2. The quick build wings have way too much sealant at the end ribs, I guess to make it look smoother and to try to prevent any damage to the sealant.
Kelly
On Wed, Sep 22, 2021 at 7:42 AM dlm <dlm34077(at)gmail.com (dlm34077(at)gmail.com)> wrote:
| Quote: | One thing I have noticed for a long time is that some pilots sit on their wing tanks on the ground while talking with other pilots. i.e AirVenture. It seems to me that this torgues the tank downward and may contribute to leaks.
| Quote: |
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1. 07:04 PM - Re: [External] RV10-List Digest: 1 Msgs - 09/20/21 (Wyatt Prunty)
________________________________ Message 1 _____________________________________
Time: 07:04:56 PM PST US
From: Wyatt Prunty <wprunty(at)sewanee.edu (wprunty(at)sewanee.edu)>
Subject: Re: [External] RV10-List Digest: 1 Msgs - 09/20/21
Just for the record, my factory tanks in factory wings set off leaking only
a few years after the completed build, 2007, I sealed and then had
resealed following all the wisdoms recommended then. And new paint. The
paint bubbled, broke open, ect. The leaks had continued. Knowing little,
I suspect bad use of bucking bars during the factory build, something to do
with bad riveting sent in the original quick build of the tanks/wings.
Now, my RV-10's tanks have been sent to someone who works with Mooney tanks
and also RV-10s, I am starting over. new paint, new hope.
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD |
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