Plastic Tank Questions

Stuka Stunt Main Forum · 5 of 5 known posts recovered

Rob Stagis · Mar 25, 2001 08:57 AM

If I set up a plastic tank without uniflow, where would the vent-bubble be? 'Up' or 'out' or 'in'? I'm running one on my Skyray and before converting it to uniflow (I might not convert, depending on the answers here - it runs pretty well) what's the concensus on where the vent should be?

With uniflow: I've soldered brass tubing to the clunk and, for these tanks, will run uniflow. This will be plumbed (unless I'm totally off course here) with clunk to engine, brass-tube to vent-tube-angled-into-the-airflow. Is there a prescribed angle to the dangle? I mean, directly into the airflow is good, right? Is there any advantage to belling the mouth of the tube?

This is mostly new to me - I ran a standard Perfect tank until I got tired of dripping fuel and stuck the plastic clunk tank on the Skyray, having never heard of uniflow. The tanks I'm setting up now are for a couple trainer-planes, one running a Fox .15 vertical plug and one with a McCoy .19.

Thanks in advance - Rob

The Kiwi · Mar 25, 2001 05:06 PM

RE: Plastic Tank (vents) Questions#1 source

The first clunk that I played with, I made with three tubes. The feed line, a filler, and an overflow. The overflow terminated in the top inside corner. The filler was just a short, straight stub that I plugged after filling. It terminated right at the inside edge of the rubber plug.

It worked just fine. I used it on the inboard side of the nose on a plane with far too short of a nose for any tank in a normal location (the hard tank buried in the wing was not feeding the way it was supposed to, and I was too lazy to cut the wing open).

That same tank, mounted on the normal side of the nose, worked OK on another plane. (It should be noted that an inboard tank like the one I set up is going to richen up a lot, so you end up with the engine being launched very lean, and have to experiment some to know where to set the needle for launch. Thus, the next time I wanted an inboard-mounted tank, I used Uniflow vents so I didn't have the extra lean launch situation again.)

Kiwi

Nils · Mar 25, 2001 11:19 PM

#2 source

LAST EDITED ON Mar-25-01 AT 11:20 PM (EST)

The angle of the dangle of the uniflow tube isn't terribly important, point it pretty much into the wind & forget it. Belling the end isn't necessary & probably not desirable.
Btw, fuel will corrode brass tubing after a while, it's better to use K&S copper tubing in fuel tanks, alcohol doesn't attack copper like it does brass.
Nils

Rob Stagis · Mar 26, 2001 05:36 AM

#3 source

I didn't know about the brass-corrosion-with-fuel thing - Hmmm. I've always plumbed the clunk tanks with the supplied tubing. Huh!

Thanks.

LNeumann · Mar 26, 2001 07:37 AM

#4 source

We have used soft brass tubes for years with no ill effects. The hard brass will sometimes split, but it can be heated to a cherry red and cooled normally to soften it and alleviate the problem.

If brass tubing is left in fuel, yes, it will dissolve and disappear (done that). But the minimal amount of time we have fuel in our tanks isn't really a problem.

Copper tubing is a solution, but introduces another problem. If not kept clean, it will grow a nice greenish goo inside that will completely plug the tube over time. Used tanks that have been stored for a while will, sometimes exhibit this problem. If you have a removable tank, no big deal. Put in a new one. If you have the tank permanently installed in the plane, it could be a major problem. I would never want to build another plane with a permanently mounted tank.

Leonard Neumann