uniflo tanks

[Bootlegger]

 Where does the uniflo vent have to be inside the tank to get the best engine run? Is it in exact line with the feed line and how far forward from the rear of the tank should it be?
 I know that if it isn't far enough forward it will "feed" air into the engine feed line and sure make the engine run "goofy".

  I have been trying to keep it at least 1/2" forward for this purpose.
 Any suggestions/help??

[Mike Griffin]

Gil when I make a uniflow tank out of a plastic Sullivan or Dubros tank.  I try to keep the uniflo tube just slightly shortery than the fuel pickup...I think the clunk is about 1/4" shorter on the uniflow tubing.  I also try to angle both ot the tubes toward to back outboard corner of the tank.  Not saying this is right but it works for me...

Mike

[Randy Cuberly]

In general terms the uniflo line should be terminated about 1/2 inch forward of the fuel pickup line to prevent "short circuiting" the air bubbles from the uniflo line directly to the pickup line.  If that happens the uniflo effect is lost and inconsistant runs will result.  It's vertical position relative to the pickup line isn't really critical but it's position will affect the position of the tank vertically relative to the engine to get an even run from upright flight to inverted flight.  In fact typically the position of the uniflo line's relative position is more important in terms of effect on upright vs inverted flight than the pickup line.  But both are important.
I think it's important to have the uniflo line as near the outside wall of the tank as practical because there is a slight richening of the fuel mixture when the uniflo line is uncovered and I don't like this occurring in the middle of the overhead eights or four leaf clover.

In a plastic tank setup the same is true.  Either a system with separate clunks or one clunk with the uniflo line affixed forward of the fuel inlet can work well...Personally I prefer the single clunk because I think it's easier to set up and tune but both can work.  With a single clunk the tank position can be tuned within a small range by simply rotating the plug to affect the position of the uniflo in the tank.  The only thing important with this setup is to use very flexible tubing and a fairly heavy clunk so the clunk responds easily to flight regimens.

I have come to the personal conclusion that all metal tanks are more reliable and therefore have decided to use only them on competition airplanes.

Randy Cuberly

[Bootlegger]

  Thanks fellow's I sure do appreciate the help, think that I have it together correctly, again thanks a lot...

  Ty and Mike sure am lookin forward to seein y'all this week end here in Baton Rouge for thr contest...

[Kim Mortimore]

I understand that back in Paul Walker's IC days, he ran a test of 5 different uniflow vent positions:  one at the common position ~3/8" ahead of the back wall of the tank, one at the front wall of the tank, one halfway between the front and back walls, one 1/4 of the way back, and one 3/4 of the way back from the front wall (all at or very near the outboard wall, of course).  His best results were with the vent halfway between the front and back walls.  I have used the halfway position with very good results, and there is very little chance of picking up air bubbles.  Hope this helps. 

[Jim Thomerson]

I have made and flown uniflow tanks with the uniflow in front, like the Bob Palmer tank, and various positions back to the usual.  I have also separated the uniflow vertically from the pickup.  All ran to suit me. 

[Bootlegger]

 Kim, was the uniflo that was at the center of the tank on the same level as the feed line, and was it soldered to the feed line so that it would not move??

 Again guy's I shore do 'ppreciate the hep..

  " Shore"  is Southern for sure, 'hep' is short for help, and 'ppreciate is understandable on it's on...     

[Kim Mortimore]

 Kim, was the uniflo that was at the center of the tank on the same level as the feed line, and was it soldered to the feed line so that it would not move??

Gil, I think any long tube in a metal tank needs to have the end soldered to prevent vibration.  I like to solder it both to the top of the pickup tube and the outboard wall of the tank.  Of course this places the uniflo 1/8" higher than if it is soldered alongside the pickup, and this 1/8" must be taken into consideration when planning the vertical placement of the tank in the plane to provide room for shimming the tank up and down to even out any differences in upright/inverted and inside/outside RPM.  Randy's reply #2 above is very helpful here.  I also like to mount the tank with the rear end 1/4" farther outboard than the front to get a clean shutoff.  Just out of curiosity, can I ask what plane you're planning on using this tank in, or is your question for general information?

 Again guy's I shore do 'ppreciate the hep..

  " Shore"  is Southern for sure, 'hep' is short for help, and 'ppreciate is understandable on it's on...     

This reminds me of a funny story a coworker here in California told after returning from his first trip to Texas.  The folks there explained "y'all" to him.  If a Texan is talking with one person, he says "y'all".  If he's talking with more than one person he says "all y'all".  They also explained "fixin' to", "tump" and "malnar" (miles per hour).