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Author Topic: Uniflow Tanks, what gets plugged off  (Read 2462 times)

Offline Allen Eshleman

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Uniflow Tanks, what gets plugged off
« on: June 13, 2015, 11:54:10 AM »
I have a simple question:

With Uniflow tanks - what gets plugged off - the fill tube or the overflow tube?
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Offline Allan Perret

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Re: Uniflow Tanks, what gets plugged off
« Reply #1 on: June 13, 2015, 12:06:10 PM »
Overflow gets plugged.  
There is no dedicated  fill tube, you fill thru the uniflow vent which is then either left open or connected to muffler pressure.
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Offline Allen Eshleman

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Re: Uniflow Tanks, what gets plugged off
« Reply #2 on: June 13, 2015, 12:42:31 PM »
In a three vent clunk tank, one tube is turned up almost to the top of the tank.  One goes straight in as what I would use to fill the tank.  The other one of course goes to the motor.  The one that is turned up to the top of the tank is the one that usually gets hooked to pressure if it is used.   I need some clarification as to which one is the uniflow.

Thanks again!
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Offline EddyR

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Re: Uniflow Tanks, what gets plugged off
« Reply #3 on: June 13, 2015, 12:49:52 PM »
That is not a  uniflow tank
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Offline Allen Eshleman

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Re: Uniflow Tanks, what gets plugged off
« Reply #4 on: June 13, 2015, 12:53:56 PM »
Should it just be filled through the engine feed line?
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Offline Tim Wescott

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Re: Uniflow Tanks, what gets plugged off
« Reply #5 on: June 13, 2015, 03:34:39 PM »
Hey Allen:

Uniflow tanks have an overflow that goes to the front top of the tank, a pickup tube that goes to the rear outside corner of the tank, and a uniflow tube that goes close to the pickup (different people put it different places -- you want it close enough to still work as a uniflow, but far enough away to not pick up bubbles).

You want to plug the overflow.  The whole reason that a uniflow tank works is because the uniflow vent is close to the pickup; this makes the head at the fuel pickup very constant, which in turn means that the tank's characteristics don't change as the fuel is drawn down.
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Offline Allen Eshleman

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Re: Uniflow Tanks, what gets plugged off
« Reply #6 on: June 13, 2015, 04:47:25 PM »
Great explanation Tim.

I was thinking of a Hayes tank that I just retired because I pulled the pickup tube out and the clunk dropped inside.  I can't get it out and the hole isn't big enough to put any other clunks in.  This tank worked wonderfully with a Fox 35 and pressure.  I also tapped off the fill line while flying as I now remember.  The Hayes tank has three vents sticking out straight above each other.  The bottom is the fuel draw line.  The next one is the one I used for fueling.  I used the top one for pressure.

I've had several Brodak tanks with three forward looking tubes. In reading, most people say that the overflow should be capped off but not necessarily the fill line.   

I currently am using a 5 oz.  Magnum tank in a Vector.  So far, I have been capping the top tube, which I think is the uniflow.  At least, I have been putting fuel in through that tube.  I've had sort of good runs.   Brand new LA 46.   I may try capping the other one to see what happens. 
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Offline Tim Wescott

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Re: Uniflow Tanks, what gets plugged off
« Reply #7 on: June 13, 2015, 05:08:14 PM »
I don't know what a Magnum tank is, but if it's a clunk tank it's almost certainly not uniflow (you can make a uniflow clunk tank, but they certainly don't come that way).

Try reaching inside of your Hayes tank with a piece of 1/16" music wire.  If you can get the clunk riding on the wire then you can probably pull it out of the clunk hole.  You could probably shake the thing for a year and not get the clunk out.

Your Brodak tanks may well have been uniflow, but that's not the only sort of CL tank out there.

I use a 4 ounce DuBro clunk tank, not uniflow, on my LA 46.  With muffler pressure it seems to give me a fairly consistent pattern.
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Offline Allen Eshleman

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Re: Uniflow Tanks, what gets plugged off
« Reply #8 on: June 13, 2015, 05:28:39 PM »
According to the Brodak web site, the Magnum tanks are uniflow tanks.   
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Offline Tim Wescott

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Re: Uniflow Tanks, what gets plugged off
« Reply #9 on: June 13, 2015, 06:13:41 PM »
It's not always clear which tube is the fuel feed and which is the uniflow.  The overflow tube, however, should come out of the bottom of the tank (bottom as it sits with respect to gravity -- not the "bottom" as you look at it in an upside-down plane!).

If you can find documentation for the Magnum tank on the Brodak site I suggest you look at it to see which tube is which.  Then cap off the overflow.
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Offline Steve Helmick

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Re: Uniflow Tanks, what gets plugged off
« Reply #10 on: June 13, 2015, 06:35:02 PM »
Is this an "all tubes forward" sort? If so, logically, the fuel feed to NV is most outboard, next is uniflow and last is overflow. Well, that's what's logical, anyway.  D>K Steve
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Offline George Mitchell

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Re: Uniflow Tanks, what gets plugged off
« Reply #11 on: June 14, 2015, 06:52:15 AM »
Hi Allen,
The Magnum tank got its name from the
Magnum airplane. The top tube is the uniflo.
The lower tube is the overflow. Fill thru
 the uniflo then cap the overflo. I leave
 the uniflo open or you can use muffler
pressure.
George

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Offline Allen Eshleman

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Re: Uniflow Tanks, what gets plugged off
« Reply #12 on: June 19, 2015, 05:52:09 PM »
Thanks George,

That helps.  That's what I'm doing now.

Also, I'm getting the different kinds figured out.  See pictures with my understanding with Dwayne's "Hey Allen, edit, piped LA 46"  post.  I took photos of several of the tanks I asked about.  I think I'm getting it untangled.  It's been awhile since I was dealing with all these different tanks. 
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Offline GregArdill

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Re: Uniflow Tanks, what gets plugged off
« Reply #13 on: June 23, 2015, 12:59:45 AM »
Allen,

I hope this pic clears up your confusion.

Here's an image of the "mysterious" uniflow. You can see the feed line in the usual place, and the uniflow (filler) adjacent to the feed line. The overflow is in the usual place, and is blocked off during flight, or else the tank just becomes a standard tank with complicated plumbing.
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Offline Allen Eshleman

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Re: Uniflow Tanks, what gets plugged off
« Reply #14 on: June 26, 2015, 06:10:29 PM »
Thanks,

That is an excellent illustration.  Well explained. 

Allen
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