SS7 wing tanks and RTV

[MotReklaw]

I installed the left wing tank in my KF and used the supplied RTV sealant. I applied the sealant in the zigzag pattern described in the manual. I let the wing set for a week, then turned the wing over to work on Rib 2 and get it trimmed to fit. I put a foam cushion out of an old couch underneath the tank "just in case."

Bet you can't guess what happened?

after about an hour, the tank fell out of the wing onto the cushion, a drop of about 3 feet. Lucky me having put that cushion under it.

My question is, has anyone had this happen? When I started inspecting the sealant, I found that it had not cured and was very soft and not an adhesive at all. Anyone know what I did wrong?

Thanks,

[jtpitkin06]

The RTV sealant is very strong when applied to a clean surface.



Everything on the Kitfox needs cleaning prior to bonding. That goes for ribs, spars, false ribs, and tanks.


Because the tanks are made in a mold they have residual release compound on the surfaces. It is possible the release compound did its job and prevented a good bond on your tanks.


Clean everything off and do it again. When used on a clean surface you can hang a truck from the tanks without them pulling away from the spars.


Be sure to use the same type RTV if you have run out. Do not use RTV from the big box stores. If it smells like ammonia, it is corrosive to aluminum and will eat your spar.


You should also clean the tops of the tanks before you cover to ensure the fabric will bond to the tank.


John Pitkin

[t j]

Check the date on your RTV tubes. If it gets old it won't cure.

I removed a tank from my wing and after cutting the rear RTV tried to twist the tank out. I couldn't budge it. I had to cut the front too. That stuff is amazingly strong.

I think the shelf life is about 15 months.

[cap01]

When I replaced my tanks , I tried to buy the rtv locally , I found no one stocked it due to it being dated and having a shelf life . Ended up ordering from kitfox , they had to bail me out again . Also right on about it really sticking when it cures . Tried the fishing line trick to cut the rtv when I was removing the old tanks with no luck , had to use safety wire to cut it

[MotReklaw]

Well I guess I should have checked the expiration date before I got myself into this fix. It expired on 8/11 which I guess is my problem. I will check to find some from Spruce and order it. I can get one-day deliver from them.

BTW, I did the prep work since I'm a stickler about that and have suffered the consequences on past builds....

Thanks guys....

[jdmcbean]

Careful with what you use.. Not all is compatible. Some Silcones are corrosive to aluminum.

[MotReklaw]

I ordered a new tube of the Dow Corning 739 Silicone Sealant and licked my calf over. Here's a pic.