Flushing older wing tanks coated with Bill Hirch sealant

[Birdseyeview]

I need to flush my 2001 vintage fiberglass wing tanks that are assembled in the wings. I have had a bad case of the Brown Sticky Stuff (BSS) issue discussed in past threads which is gumming up my carburetors and causing rough idling. I'm removing my wings to better enable the rinsing/sloshing of the tanks. In reading the Kitfox service bulletin #60 it suggested options for aggressively rinsing the tanks, all using acetone and some options acetone mixed with AVGAS. However, at the end of the service bulletin it states that fiberglass tanks manufactured before 2007 should not be rinsed with acetone and that they should only be rinsed with AVGAS alone. Does anyone know what will happen to these older tanks if they come in contact with acetone? Any opinions on whether the AVGAS rinse alone is good enough to completely eliminate all the release agent?

I have another potential complication in that my tanks were coated with the Bill Hirch sealant that was also discussed in past forum threads. I put this in the tanks prior to installing them in the wings and believed at the time it would help "seal" the fiberglass from any possible future fiberglass release agent coming out of the tanks. I also expected that it might "seal" the tanks from any future possible exposure to ethanol laced fuel if I was forced to use some in an out of gas scenario somewhere. It's painfully obvious to me now that the Bill Hirch sealant is not working to seal out any fiberglass release agent outgassing. But it probably won't prevent the AVGAS from rinsing the release agent out of the fiberglass either. Once my flushing is done I'm wondering if I should use AVGAS exclusively for a while before switching back to MOGAS. Any opinions on that though?

[N14ND]

Bummer Larry. Sorry to hear that. I feel your pain. I have a 1995 S5 that I removed the top of the tanks due to sealant/sloshing issues. There are some threads on various tank clean out methods. I removed my tank lids. To clean out the sloshing. Made new tops. Sealed the inside with Jeffco 9700 (now Rhino Linings 9700). Polyester Resin (my tanks) and Acetone don’t play well together when soaked. But that may be your only choice. Buy or borrow a borescope to view in the tank. I bought one for $250 that Bluetooths to a phone/pad. Worth the peace of mind and helps with strategy. Good luck.

[Birdseyeview]

N14ND,

For what its worth to anyone using the Bill Hirch sealant - I ran a little test with a coating of this sealant in a small steel cup - let it dry for 24 hours and then put a little acetone in the bowl. The tech sheet on the Hirch website says it is immune to fuels and alcohol but it will dissolve with exposure to MEK. My test demonstrated that acetone also thins it out dramatically, and almost instantly. After the acetone evaporated the sealant did harden right up again. They also say that their "type" of sealant is widely used in aircraft tanks but they will not knowingly sell their sealant for use in aircraft because they can't control the application process or the end result. Sounds like their lawyers wrote that line. This sealant really sounds like it is best used to plug tiny pin holes but I wouldn't use it again in my Kitfox tanks since it doesn't seal out anything leaching out of the fiberglass. I'm hoping that the AVGAS flush per Kitfox service bulletin #60 flushes out all the BSS in my vintage tanks. I hate to think about replacing some or all of my finished tanks. I could do that but as I'm sure you found out its a giant pain the rear, especially on finish painted wings.

[avidflyer]

Maybe the company will have some advice that helps you out when you call them. JImChuk

[buckchop]

Well im going to keep an eye on this also, as i need to remove the sealant on the KF5 with a 0235/115hp i just picked up, it has one 13 gallon and one 6 gallon tank in each wing so i have my work cutout for me. Hahahahaaaaa

[buckchop]

Well scratch that tanks setup. Hahhaaaaa i have two 13gallon tanks in each wing. 52 gallons total plus whats in the headed. Does anyone eles have that much fuel storage? Guess at 5gph it have about 10 hrs flyin time.

[Denalifox]

Well scratch that tanks setup. Hahhaaaaa i have two 13gallon tanks in each wing. 52 gallons total plus whats in the headed. Does anyone eles have that much fuel storage? Guess at 5gph it have about 10 hrs flyin time.

I WISH I had that setup with my 320. Fuel bags are standard equipment for me. Considering building a 15ish gal header tank. I don't have the legs like my Super Cub friends. lol

[buckchop]

I WISH I had that setup with my 320. Fuel bags are standard equipment for me. Considering building a 15ish gal header tank. I don't have the legs like my Super Cub friends. lol
Well u could but it makes more work and less flyin time for a little while. Hahahahahaa yea the pa12 with 0320/160hp is hard on fuel also compared to the KF, y i love to fly them in winter when most my flyin time is. Damm gold mining is cuttin into my flyin/building time hahahahaaa but not for much longer this yr.