Figure this out

[Phil Coopy]

Twister, 46oz, LA40 muffled, nonpressured uniflow tank 1/4" above thrustline, 60ft lines, and 11-5 prop.  The engine runs straight 2c from take off thru the inside loops, then during the outsides it settles into a nice 4-2-4 for he rest of the the flight. If I set the needle richer it runs sloppy all through the flight and if I set it leaner it runs away. Can this be tank height or something like that?

Phil

[Richard Grogan]

If I may ask, why did you set the tank above the thrust-line? Try to center the pickup line with the venturi and see what that does...

[Steve Helmick]

Tank height may need more adjustment, but I'd bet on a problem with the tank itself, like a cracked uniflow tube inside the tank.

I'd bet that you'll also find a better prop, if you keep trying. Prop load is an important part of getting the setup to work. The 10.5 x 4.5 APC is one of the best standard props for OS .40LA, .40FP and B.40's. If your LHS doesn't stock them, they can get 'em for you.    Steve

[Lynn Weedman]

I agree with what steve is saying about tank hight
and posable uni-flo tubing cracks or even the end of the uni-flo tube breaking the solder joint at the pick-up
tube. you might even look at the filter your using, it could be fine enough to restrict the fuel flow to cause the 2c condition at crank-up and during flight centrifical force and venting help to richen the fuel flow. Just a theory but it's probably the tank! 

[Will Davis]

Phil,
   First guess would be tank problem, Change tank or check inside for loose  or cracked tubing .

William Davis

[Paul Taylor]

I am taking the "Shot-Gun " effect with my Twister.
Changing out the metel tank with a Clunk, new NVA, and backplate.

10.5x4.5 is a FF prop, and not sure it did much last time I tried one. But maybe after the changes I may try it again.

Paul

[L0U CRANE]

Phil,

Somewhere in here, I wrote up my pre-first-flight tank height check procedure. B.Little likes it, too. (He says   )

Mainly, it is a way to prevent a setting that will flame out on you on the first flight. Such flameouts always seem to be at the worst possible place, time and attitude.

Works for me, and Bear, too, apparently. See if you can find it, and give it a try.

As we all seem agreed it is likely a tank height thing, my wig-wag process should narrow things down a lot.

[Bill Little]

Phil,

Somewhere in here, I wrote up my pre-first-flight tank height check procedure. B.Little likes it, too. (He says  )

Mainly, it is a way to prevent a setting that will flame out on you on the first flight. Such flameouts always seem to be at the worst possible place, time and attitude.

Works for me, and Bear, too, apparently. See if you can find it, and give it a try.

As we all seem agreed it is likely a tank height thing, my wig-wag process should narrow things down a lot.

Hi Lou,

Yes it does work, I do use it, and I do like it!! 

Bill <><

[Jim Pollock]

If it were mine......

I would take the OS needle valve out and replace it with an ST needle valve.  I bet that just might cure it!

Jim Pollock

[Phil Coopy]

Well I moved the tank down even woth the venturi.  The engine already has a Carl Shoup head, ST NVA, and a little larger venturi.  We'll try 'er out tomorry.

Thanks guys,

Phil

[john e. holliday]

Make sure you have checked the whole fuel systems.  So far I have had a leaky fuel filter on one plane.  On another it was brand new peice of fuel line that I kinked enought that it cut thru at the fuel pick up tube.  Last of all you you beleive a needle valve assembly that leaked at the engine venturi.  In all three cases the fuel tank passed the pressure test.  DOC Holliday