Kind of a newbie question on fuel tanks.

I recently assembled a fuel tank that came with a relatively
cheap 'chinese' ARF. Fuel tank went together OK but during
pressure test some bubbles escaped through the screw. This
happened at 'high' pressure, which is about as hard as I can
blow into the tank. Continued regardless of how much I tightened
the screw.

Is it necessary to make fuel tanks 100% sealed, or can some
leakage occure.

PS> I've assembled dubro tanks before without getting any
bubble leakage.

Thanks for the input!

It's always better to be 100% sealed for peace of mind. That way if you have engine tuning problems, you can eliminate the fuel tank as a source. Your tank will probably work okay if it takes that much pressure to make bubbles. But, I would either try to seal the threads on that screw or toss the tank and put in a good one.

Dubro, Hayes, Sullivan and Tetra are all quality tanks that you will experiance very little problem with.

Actually a majority of the cheap tanks included with many ARF's range from barely usable for a short while to totally useless. Among the worst are the ripoffs of the Hayes tanks, ironic as the real hayes tanks are among the best.

If your tank has the rubber bung with a tightening screw in the middle about all you can do is try tightening it a little. Chances are it will eventurally fail and yes I would use no tank that show any signs of weeping in my opinion.

John

That tends to indicate that either the backplate is not "squeezing" the stopper enough to plug the leak, or that the hole drilled out in the center has a cut or crack in it.

I'd replace the stopper in your shoes.

Hi! This Sullivan Kit will also get rid of your bubbles!

[link]http://www2.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=S478[/link]


Keep Flying
Alex

As the others above have indicated, you have a problem. If you can blow air out of the stopper then fuel can leak out of it. Any fuel leakage out of the tank is unacceptable no matter what. That fuel will leak into the tank compartment which on most ARF's doesn't have the wood properly sealed. The fuel will soak into the wood and weaken the structure of the plane, which can/will result in failure of the airframe in flight. If you can't get the tank to seal you either have to fix the problem or replace the tank. If it's just around the screw that it's leaking I would put a little bit of silicon caulking/sealant into the hole in the stopper and reassemble the tank. See if that fixes the leak. If it still leaks then you should just replace the tank.

Ken

Alex that is a quality unit and if the tank itself is a quality one it will work very well.

The problem is with the very poor tanks is a mold seam that goes right up to the rim with very little mateing surface with they plug. These will weep no matter what you plug the hole with and the seam will get progressively worse.

I have assembled a lot of ARF's for a lot of people but will not use the arf tanks. If that is not acceptable then I don,t do the project. New quality tanks are cheap, new airplanes are not.

I used to have a wall full of new Cheezy tanks and occassionally gave them away untill it dawned on me what a disservice I was doing to the folks I was giving them too and got real guilty. So they are always discarded now.

Just my opinion.

John

Thanks for the input all!

Just wanted to make sure that I wasn't being overly anal about
stopping 100% of the leakage, since I'm not sure how pressurized the
tank actually becomes when the engine is running.

BTW John, this tank does look like a ripoff of a rectangular Hayes tank lol.
When I get home I'll have to check if there is a seam like you spoke about
up to the rim.

The muffler pressure can put a good bit of pressure into the tank. Well over 12 PSI.

I've measured as much as 20 PSI.

The easiest recognition point on the Hayes ripoffs is the the missing 'O' ring. The genuine Hayes has an O ring on the hard plastic insert plug in a proper ring grove and the ripoffs don,t bother with this or any ring at all, They never seal