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Old 07-31-2019, 07:44 AM
DanH's Avatar
DanH DanH is offline
Join Date: Oct 2005
Location: 08A
Posts: 9,336

Originally Posted by PhatRV View Post
There is another thread talking about Proseal turning into mush when the tank is leaking. This gets me worried because I thought the Proseal is fuel proof and the leaking is caused by improper sealing instead of Proseal disintegrating over time. Were you using the 10:1 mix ratio in your build or did you vary the mix ratio to compensate for the temperature?
We know it happens. We don't yet know why it happens, not in the chemical sense. It is not mix ratio; the manganese dioxide is a catalyst, not a component. Full reversion appears to be linked to evaporation of fuel in free air. Some older technical papers suggest a link to the formation of peroxides in fuel.

Most would be surprised to learn there is no mil spec or standard specific to polysulfide sealant use with avgas or mogas. All tests are done with JRF, a standard fluid emulating jet fuel. Does it matter? Clearly the sealant works under normal circumstances, inside the tanks. Avgas is standardized. Mogas is always a wild card.

Entirely aside, I'm not aware of any manufacturer's instruction which suggests mix ratio should be varied for temperature.
Dan Horton
Barrett IO-390
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Old 07-31-2019, 12:32 PM
PhatRV PhatRV is online now
Join Date: Mar 2018
Location: Buena Park, California
Posts: 246

Thanks for the info. I don't vary the mix but other mentioned they used a hotter mix while working in colder climate.
RV8 standard build: Empennage 99% completed
Wing -- Closed
Fuselage -- On Gear
Avionics Installation -- started

Donation paid through 2020
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Old 07-31-2019, 11:46 PM
Yen Yen is offline
Join Date: May 2010
Location: Benaraby Queensland. Australia
Posts: 206

I used the standard ratio. Will have to find the other post about proseal.
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Old 08-01-2019, 06:35 AM
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agirard7a agirard7a is offline
Join Date: Aug 2009
Location: Newport, RI
Posts: 698
Default Tank test

I used the bubble test and it was evident where leaks appeared to be. However, it did not get all of them. I highly recommend the fuel test. Put the tank on concrete. The concrete will stain or just be wet. Weeping rivets did not bubble test well. I learned the hard way after installing and then having to remove my tanks. Find some 100 LL somewhere. Not to hard.
Al Girard, Newport, RI
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Old 08-01-2019, 09:31 AM
JDA_BTR JDA_BTR is offline
Join Date: Dec 2013
Location: Baton Rouge, LA
Posts: 1,034

Nobody mentioned Snoop. Cheap at about 4 dollars a bottle. Super sensitive to slightest leak. Has a little glycerine in it with the soap. Get it at a swaglok distributor most towns have one. If it doesn?t bubble with Snoop there is no leak.
Ser 104142, RV-14A flying - N1463
Ser 83825, RV-8 building - N8638?
USN Ret, Urologist, AME, Repeat Offender
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Old 09-02-2019, 08:43 PM
coffeeguy coffeeguy is offline
Join Date: Jul 2015
Location: Lake in the Hills, IL
Posts: 156

I was thinking about the comment about using snoop. My initial thought, was cool, a better way to flush out bubbles. My concern would be what if there was a leak? Would the ingredients in snoop interfere with bonding new sealant to the existing sealant? Yes, you can clean the surfaces, but in this case I would be hesitant to mess with what has always worked.
Jeff Dingbaum
RV-14A empennage, wings, fuselage
Cherokee 180
2020 dues paid
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Old 09-03-2019, 01:16 AM
Yen Yen is offline
Join Date: May 2010
Location: Benaraby Queensland. Australia
Posts: 206

Follow up on my problem. I am sure the leak was caused by mogas as the tank which only ever had avgas still does not leak. My bodgy job didn't work, so I removed the tank again and found a leak at the rear of the wing closest to the fuselage, where rib, top skin and aft wall of the tank meet. Much probing and I managed to find the leak, right in the corner. Eventually I got a 3/32 drill right through and with much probing and scraping was able to fix the problem with proseal. The cost of proseal was less than the cost of freight. So far all seems well, It tested OK and has been filled twice since repairing it.
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