Fuel Tank Access Panel & Debris

[krw5927]

After a failed leak check on one fuel tank this weekend I decided to cut an access hole in the baffle, seal the leak, and fabricate a doubler and cover plate similar to the access plate on the root rib. However, in cutting and shaping the new hole in the baffle, lots of aluminum chips/dust were created and seemed to really like to stick to the still slightly tacky proseal fillets inside the tank. I cleaned up the area pretty well using wet cloths and a vacuum, but I'm concerned that debris may have made its way into the adjacent rib bays where I'm unable to see/clean it.

Interested in getting some expert opinions on how best to deal with this. Right now I'm thinking seal up the tank, pressure test again, and upon passing fill with water and drain several times. Perhaps standing the tank on end, full of water, will let any debris make its way down to the drain valve, whereupon I can remove the drain and flush out the debris. Wondering though if fuel might not be a better flushing medium/solvent.

Thoughts? Thanks in advance!

[terrye]

Don't know how long you let the proseal cure before leak testing, but my opinion is that it should not be in the "sticky" in the least. Mine feel like cured rubber and I don't think aluminum shavings/chips would stick to them.

[krw5927]

Probably should have clarified. In my experience, Proseal takes at least 2 weeks to get to the point it feels like cured rubber. This tank was no different from the last in that regard. I'm mixing the components 10:1 by weight on a gram scale, as per the instructions, and have used 2 different lot numbers from two different vendors, so I don't suspect the Proseal is bad. Maybe the Kansas humidity slows it down or something.

Waiting until it had cured to that point probably would have been wise, but I guess I messed up. To clarify though, I was able to clean the Proseal fillets in the affected bay quite well. Just afraid (assuming) there's debris in the other bays as well.

If there's no way to confidently flush the tanks then I could always make some more doublers and plates, and cut access panels in every bay of the tank to clean it thoroughly.

[David-aviator]

Originally Posted by krw5927

Probably should have clarified. In my experience, Proseal takes at least 2 weeks to get to the point it feels like cured rubber. This tank was no different from the last in that regard. I'm mixing the components 10:1 by weight on a gram scale, as per the instructions, and have used 2 different lot numbers from two different vendors, so I don't suspect the Proseal is bad. Maybe the Kansas humidity slows it down or something.

Waiting until it had cured to that point probably would have been wise, but I guess I messed up. To clarify though, I was able to clean the Proseal fillets in the affected bay quite well. Just afraid (assuming) there's debris in the other bays as well.

If there's no way to confidently flush the tanks then I could always make some more doublers and plates, and cut access panels in every bay of the tank to clean it thoroughly.

Kurt,

I must 'fess up - I had 2 leaks doing the balloon test before declaring the tanks held air (and hopefully fuel).

One was a bad rivet at the drain fitting, the other a lack of sealant along a couple inches the aft baffle flange.

The rivet was drilled out a replaced with one of blind rivets used with the Z brackets. Problem solved.

The aft flange leak could have been sealed externally but I decided to open the bay and get to in from the inside. I was also concerned about cutting debris inside the tank. I vacuumed out what I could, fixed the leak and installed a plate from Vans for such jobs, no doubler required. Both leaks fixed, no more soapy water bubbles.

To get rid of any debris in the tank and not contaminate the tank with water, I bought some mogas and rinsed it out with it. The fuel was strained going into a funnel coming out the open drain valve hole with no fitting and there was no debris at all. I think the tanks are mostly debris free but will check the filters after about 25 hours of operation.

The sealant was about 2 weeks old when all this transpired.

[krw5927]

Thanks, David. So that's one vote for the "rinse it out and keep a keen eye on the filter/gascolator" approach. Definitely the way I'd like to go, but felt a need to ask the advice of all the experienced folks here. Thanks for your "confession".

Anyone else?