Cork, rubber or just proseal tank gaskets??

[Bob Axsom]

I thought the cork gaskets supplied by Van's were the proper way to seal the tank access covers. Disaster! The day after calibrating the senders I had a major fuel spill inside the airplane and all over the hangar floor. With tip tanks I had a lake in the general shape of an an airplane without a horizontal stabilizer. Thinking that the cork would provide a sacrificial separation point for maintenance I removed the tanks, cleaned everything up and added proseal to thew process. Still had seeping leaks around the screws. Cleaned this area and added proseal over the screw heads and every thing seems OK after approx. 270 hours of operation but this is one area of my work on the plane that I wish I had to do over with fresh tanks. The cork would be thrown away and I would only use proseal at every joint, penetration and interface.

Bob Axsom

[pecanflyboy]

Proseal ONLY! Van's Float Seal Bending Diagram specifically says to discard the rubber gasket supplied with the sender. I just replaced my 11 year old senders, and I was shocked to find the builder only used the rubber gasket. It was not leaking, but the gasket fell apart as I removed the sender. It was cracked throughout. Just a matter of time before I had big problems. The only good part is the senders came out easily and prep for the proseal was a piece of cake (no sealant to clean up!).

[lr172]

I am sure proseal works well. I didn't have any laying around and made a gasket from felpro gasket material. The stuff engine gaskets are made from. I used an anaerobic sealant on both sides of the gaskets and on the screws (head and upper thread area). No leaks in 5 years and don't expect any problems down the road.

Larry

[OZCleco]

We just opened up the on-wing tanks on our club RV9A prompted by weeping from both covers. Cork + unidentified sealant.

Cleaned off all the old stuff on both sides with a Scotch Brite wheel and Dremel scourer wheel, followed by wax & grease remover then contact cleaner. Access was fun but definitely doable.

Masked up 5mm beyond the circumference on the airframe side and gooped the interfay with a 2mm thick layer on both sides using 1422 B2. Fasteners were installed wet although it wasn't necessary with all the excess oozing into the holes. Fasteners were sealed around the heads as well. Tightened them only enough to ensure there was slight bead forming around the perimeter of the cover and at least a 1mm layer of sealant would remain for the interfay. It was guesswork. Let that sit for a week before filling the tanks.

We've had some bloody warm days on the west side of Australia prompting full tanks filled in the morning to spit fuel out the vents in the middle of the day. That was a welcome leak.

Feels good to know that the buggars are sealed up properly and won't be sending fumes into the cockpit ever again.

[OZCleco]

And a few months on and these tanks have remained completely leak free (where we have sealed).

I'm reposting because we had to go back into the left tank to resolve a leaking BNC connector from the fuel capacitance system, installed prior to our taking ownership.

The tank access cover was removed with great difficulty and revealed a uniform interfay seal between cover and tank rib of about 0.5mm. There was also a consistent bead of sealant around the circumference of the tank rib hole and the outside perimeter of the cover plate.

Coming from the airline world where proseal and AVTUR is the norm, I'm glad to see the results with AVGAS, and our tank is once again sealed tight.

Just have to remember to let it cure fully before chucking fuel in. 30 hours in our case. Very important point.

[scsmith]

I have a different process that has always given great results, and has the added advantage that it is pretty easy to re-open and clean up, then re-seal if needed.

I use the cork (or rubber) gasket, coated on both sides with one of two very similar products. One is called Permatex Hi-tac, the other it Permatex Aviation Form-a-gasket. Both of these products are a chocolate brown syrup that coats and impregnates the gasket, the screws and threads. Both are very resistant to fuels.

I have always done this on my cars. I have done this on two RV wingsets. No leaks. I have had to open one tank up to replace a fuel level sender. Easy. then clean up with solvent (acetone and MEK, I think) and re-seal.

Another pro tip -- use allen-head cap screws to hold the tank plates on. That way the screws can be easily removed with the wings on the fuselage, working in the narrow space.

[agent4573]

We got our QB kit delivered a few weeks ago, and I saw the cork gasket on the drawing, but it wasn't listed in inventory and definitely didn't get delivered. The instructions still mention it too, but I figured a little proseal would be just fine.

[bruceh]

Timely thread! Josh's RV-9A had quite the fuel leak. I pulled off the wing root fairings and found the gasket under the fuel sender leaking like crazy.



Proseal is ordered and on the way from Van's. I got some new, much thinner, Viton gaskets from Aircraft Spruce, but now I'm not sure whether to use them in addition to the proseal.
I looked at what I did on my RV and I did use proseal in addition to the gaskets.

The sender came out easily with the wing root fairing taken off.



No sign of any proseal on the sender except for some under the screw heads.

[OZCleco]

I really like the idea of Allen key bolts!

Would have fitted those had they been available here in Western Australia. Takes too long to ride a Kangaroo to the eastern states where the bounty is plentiful.

The stuff that our fuel sensor was coated in was a tar-like substance that could be scrapped off with a fingernail. When AVGAS permeated through it became yellow and smelt like diesel. Does that sound familiar to anyone?

[Freemasm]

Sounds like old Gasket Shellac. A pic might help if you're that curious.