K

Kato's 8

Well Known Member
Hello all,
Can I get your opinion on why some builders choose to seal their tank access panels with proseal only instead of using the vans supplied cork gasket? Also, has anyone used both? I'm a bit nervous with using the proseal alone because I don't know how tight to tighten down the screws. I guess It would be possible to squeeze out most all the seal and then have near zero gasket. What say Ye?
Thanks, and good weekend everyone!
Bill
 
When I installed the float and sending unit I used just proseal and through out the cork, no issues. When I tighten the screws it left a nice bead of proseal inside an out.
 
I used both by coating the cork gasket on both sides and coating both mating surfaces with proseal. I had no leaks in 4.5 years. Sold the plane in 2008, but I assume the seals held for the new owner.

This has been debated ad nauseam.

Roberta
 
Pro-seal only. My tanks are done that way.................and have no leaks at all. Search back through the archives, and you'll find it's the best method.

L.Adamson --------RV6A
 
It has been done all three ways by many people, and probably successfully in most cases. However, I have heard of more leak problems (in my time in the RV world) with nothing but cork, and also with cork+pro seal. I went with nothing but pro seal on the RV-8 because that is how tanks were sealed in the Grumman world that I came from, and have had no leaks in 1350 hours.
 
And now for an opposing view. I used cork with Fuel Lube (ACS is now selling a Fuel Lube equivalent, the quart is a lifetime supply). After testing my tanks I found I had to pull it apart to do the service bulletin, so prosealing could potentially have left me building new tanks - proseal is dang difficult to get apart. I put new cork gaskets and fresh Fuel Lube on, retested, and 4 years later have no leak issues plus my inspection ports are easily removable if need be. As in so many other instances, Van knew what he was doing.
 
flion said:
And now for an opposing view. I used cork with Fuel Lube (ACS is now selling a Fuel Lube equivalent, the quart is a lifetime supply). After testing my tanks I found I had to pull it apart to do the service bulletin, so prosealing could potentially have left me building new tanks - proseal is dang difficult to get apart. I put new cork gaskets and fresh Fuel Lube on, retested, and 4 years later have no leak issues plus my inspection ports are easily removable if need be. As in so many other instances, Van knew what he was doing.
Click to expand...

Recently I removed both access plates which had been pro-sealed in with no cork back in 2002. They were stuck together all right but a very thin flexible putty knife with a sharpened edge cut the sealant without damaging the rib or plate. I had to use a hammer to get the knife through the sealant but once it was most of the way cut, it popped right off.

I cleaned up the plates and installed them likewise in the new tanks with the SB finally complied with, which IMHO is a CYA SB. There's no way that pick up tube will come loose if it is properly tightened. The safety wire is in to satisfy the lawyers if need be in the future.

Another subject which may interest some, the right fuel indication has been intermittent since day one and I figured out what the deal was. The fuel gage pick up device was not adequately grounded. Those plates had the rubber gaskets. This time there are no gaskets, just metal to metal pro-sealed in and the ground seems to be very adequate. At least both sensors tested in ohms very well.
 
I did what Patrick did but used gasket seal so it would be easier to remove if necessary. I also used the allen-head screws. Works well so far (2.5 years, 350 hours).

Greg
 
Proseal only

Proseal makes a leak proof bond. If you have to remove the plate for any reason a putty knife and a little warm-up from a heat gun will soften it enough to remove the plate without destroying anything.
 
NYTOM said:
Proseal makes a leak proof bond. If you have to remove the plate for any reason a putty knife and a little warm-up from a heat gun will soften it enough to remove the plate without destroying anything.
Click to expand...

Yep................my prosealed only covers had to be removed for the SB. At first it seamed like a bear, but then went easy. No damage at all.

L.Adamson --- RV6A
 
flion said:
And now for an opposing view. I used cork with Fuel Lube (ACS is now selling a Fuel Lube equivalent, the quart is a lifetime supply). After testing my tanks I found I had to pull it apart to do the service bulletin, so prosealing could potentially have left me building new tanks - proseal is dang difficult to get apart. I put new cork gaskets and fresh Fuel Lube on, retested, and 4 years later have no leak issues plus my inspection ports are easily removable if need be. As in so many other instances, Van knew what he was doing.
Click to expand...

Why did you use Fuel Lube on your cork gaskets. Is this a technique used on certificated aircraft? Did you speak to a Licenced Maintenance Engineer about this? Does Vans recommend it? Or did it just seem like a good idea at the time.

Fuel Lube is not soluble in fuel and therefore it can potentially carry downstream and cause serious problems. I think builders need to be particularly circumspect about what they do on the fuel supply side. Logic dictates that it is not a good area to be making "intuitive" design decisions.
 
Bob, what are you assuming I did, glob it on like proseal? I lubed the gaskets with it, just a film on the cork surfaces to help them seal. On automotive applications where cork gaskets are used, I've always used fuel lube or Vaseline. Just a thin smear or you will deform the cork. As for whether it's a technique in certificated aircraft, it is in this experimental certificated one. I don't know about a Licensed Maintenance Engineer (could you mean an A&P?) but several A&Ps, including IAs, know what I did and my DAR passed it.

I don't mean to sound smart-arsed in response; your point about indiscriminate design decisions is sound. But I think you made some undue assumptions about my application.
 
it's common pratice

Captain Avgas said:
Why did you use Fuel Lube on your cork gaskets. Is this a technique used on certificated aircraft? Did you speak to a Licenced Maintenance Engineer about this? Does Vans recommend it? Or did it just seem like a good idea at the time.

Fuel Lube is not soluble in fuel and therefore it can potentially carry downstream and cause serious problems. I think builders need to be particularly circumspect about what they do on the fuel supply side. Logic dictates that it is not a good area to be making "intuitive" design decisions.
Click to expand...
Not sure if it?s ?approved? but I can tell you it?s common practice to put a thin film of fuel lube on cork gaskets used in fuel systems in every GA shop I ever worked in.
 
I used the cork gasket with a thin layer of permatex 2. Left wing started leaking (weeping). Replaced with proseal only and ok so far (just a few months). Waiting for the right wing to see if it will need the same repair. I'd stay away from the cork!
 
I originally installed the plates with the cork gaskets and Fuel Lube. One lasted about a year before it started leaking and the other lasted about two years. When each was replaced it was with Proseal only. There have been no further problems for about 10 years. I did have to remove both plates for an unrelated issue and they were no problem to remove.
 
I did the cork and fuel lube job and used allen screws. Had some leaks and was able to tighten them up with the tank on the wing.

Later the fuel level in one tank quit working and I had to remove the tank. Turned out there was a tiny leak in the float solder joint and it had filled with fuel! Glad the cork was there. The cork has not leaked for about 6 years now.

I used to work on a Reno Super Sports racer that had horrible problems with leaks in the metal wing. We had access ports on the tanks and used to remove them quite often. They were put on with ProSeal, but could be removed easily by just using the sharpened scraper. The covers were .060 alum, so they were quite stiff.

Bruce Patton
 
Cork

Just removed my tank in March to proseal around a cork leak on the fuel sender. Plane was built and sat in the desert for 5 years. The cork dried out and I was able to re-torque the bolts easily....too easily.
 
flion said:
so prosealing could potentially have left me building new tanks - proseal is dang difficult to get apart.
Click to expand...

It is indeed annoying, but not impossible. I pulled mine a while back in order to fix a tank leak. There is no way prosealing the access cover on is going to lead someone to building new tanks.
 
All the methods work

Kato's 8 said:
Hello all,
Can I get your opinion on why some builders choose to seal their tank access panels with proseal only instead of using the vans supplied cork gasket? Also, has anyone used both? I'm a bit nervous with using the proseal alone because I don't know how tight to tighten down the screws. I guess It would be possible to squeeze out most all the seal and then have near zero gasket. What say Ye?
Thanks, and good weekend everyone!
Bill
Click to expand...

Bill,
It's just a matter of fixing a flaw in the design of the fuel tank access cover attachment system. You can find a lot of info at the web links below. I used NAS1473-A08 "sealed" fuel tank nut plates. I did this so that I would not have to resort to ProSealing the covers on. I wanted to maintain "ease of maintenance". I did not know about the existence of pan head screws with O-rings under their heads, at that time. There is no right or wrong way to seal this area. The methods put forth will all work. My method was more complicated than the others suggested.
The actual problem is caused because the common K1000 nut plates allow fuel to seep between the threads of the nut plates and the #8 screws. The fuel oozes out under the pan head of the screws. Folks "assumed" that the leak was at the sealing surface of the access cover. See the two links below for more info and photos. Info starts with the PS section of post #16 below. Following posts also give info regarding using the self sealing #8 screws with O-rings built in.

http://www.vansairforce.com/community/showthread.php?t=42681&highlight=fuel+tank+cover&page=2

Fourth photo shows the NAS1473-A08 nut plates and access cover installed on the fuel tank. See

http://www.vansairforce.com/community/showthread.php?t=42764&highlight=fuel+tank+cover

Charlie Kuss
 
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flion said:
Bob, what are you assuming I did, glob it on like proseal? I lubed the gaskets with it, just a film on the cork surfaces to help them seal.
Click to expand...

Patrick, many qualified and experienced aviation maintenance engineers will not use Fuel Lube (or it's equivalent) anywhere in the fuel system. The concern is that even very small quantities can travel downstream and block filters, or lodge in small apertures such as fuel injectors.

Incidentally, the reason cork gaskets often do not form a good seal is that they are often OVER tightened.

Possibly a better solution than cork gaskets at tank inspection ports is PPG Access Port Sealant. This is a fuel resistant polysulphide "proseal" but with reduced adhesion to facilitate ease of removal.
For further details on this product readers can go here:
http://www.ppg.com/coatings/aerospace/sealants1/pr_1428_class_b.pdf
 
Captain Avgas said:
aviation maintenance engineers
Click to expand...

Again that term, so I looked it up and it really exists. I learned something new today; I thought you were just using a jumped-up term for A&P. Ok, so you have some anecdotal evidence against using fuel lube while elsewhere we have other equally anecdotal evidence for using it. My own experience says it works but I agree that it can cause the problems you describe. This is caused by overusing it (easy to do, the stuff is gooey and difficult to work with). Used properly, there should not be enough extra to go anywhere. You just want to lubricate the gasket, not saturate it. I also agree that a common problem with cork is overtightening; I've done this myself.

The compound you linked is interesting, sounds like a good alternative to Proseal. My objection to the sealing method is not that it doesn't work or even that it can't be removed. It's just messy, especially if you separate the parts - then you have to carefully clean both surfaces before re-sealing it again. Plus there's the difficulty in controlling how much you use and preventing excessive ooze while trying to ensure a good seal. Gaskets are a much neater solution, which is why you see pre-manufactured gaskets pretty much everywhere. That said, I'm not wild about the cork gasket used there and I don't blame people for sealing the plate shut. I'd prefer to have a seal similar to the one provided with the fuel senders. I also note that they did away with the inspection plates in the RV-10.
 
flion said:
Gaskets are a much neater solution, which is why you see pre-manufactured gaskets pretty much everywhere. That said, I'm not wild about the cork gasket used there and I don't blame people for sealing the plate shut.
Click to expand...

Patrick, glad to be of assistance.

In reality, apart from fuel tank access ports, you don't see many (if any) cork gaskets in modern aircraft engine fuel systems. They've largely been replaced by gaskets made from other media.

Sometimes people use Fuel Lube on "rubber-type" gaskets as well. That only serves to INCREASE the potential for leakage because it reduces the gasket's coefficient of friction thus allowing the gasket to displace under pressure.
 
Yep, agreed. Never use fuel lube on other types of gaskets. And, yes, there are about 0 gaskets in the rest of the fuel system (save a couple of O-rings); I was talking about all systems in general (no one goops an oil filter or sump or head cover but the case halves, being 'permanent' get gooped, and so on). So the question, to me, is 'will the plate be permanent or not?' I gasketed because I planned to treat the plate as removable but I have no argument with those who decided to seal the plate in. To paraphrase another post, there's more than one way to skin this cat.;)
 
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