Well, I would try a hotter or fresh plug first. Enya #3 or TBolt BigBore would my choice. Outside's tend to clear the plug on inverted engines, and if it's not up to snuf, you'll see some leaning on outsides.

If the above doesn't work, clunks they can sometimes fool you, as inverted/upright will be ok and maneuvers wont. Is this a round clunk? Or rectangle with the cap and tubing straight out the front? Then loosen the set screw in the stopper and rotate the cap 1/16" Clockwise (should raise the tank for inverted flight effectively) and just try it and see. That's how I tune my 4-stroke ships that have clunks, works great.

As a matter of fact, I replace the Phillips course screw with a socket head course screw so I can turn it with a ball driver and don't have to pull the engine/tank to make adjustments. Easy peasy!

Hope that helps,
EricV

Tim,

If those suggestions don't solve your problem I'd consider disconnecting the uniflow from the clunk and replacing it with a solid piece of tubing ending at the outside edge of the tank about halfway back.  I've never understood the concept of a moving uniflow vent because it adds a significant variable to the fuel system.  The engine thinks the end of the uniflow vent "is" the tank.  When you allow the uniflow vent to move up and down it is the same thing as moving the tanks up and down.  Variables that you don't need!

A bazillion "hard" uniflo tanks have been successfully used by stunters for decades.  I would almost certainly start with a fixed vent and only experiment with options if it didn't work the way you hope.  My best guess, however, would be that if it didn't work as desired the problem would probably be elsewhere and not the fixed uniflow location.

FWIW

Ted Fancher

Ted is absolutely correct,  sorry I didn't catch it... I tend to take it for granted. By all means, a hard uniflow would be the next step.

Plus, since fuel tends to pool up to the outside of the tank, just short of the back (unless you canted the tank) you can run the unifow short enough to have the clunk well clear of it and still have everything in the proper place with the added bonus of keeping any uniflow air bubbles further away from the pickup. I kinda "swedge" the hard uniflow to the outside of the tank as soon as it passes the neck up front so that it's running parallel and flat against the side of the tank as much as possible. It's kinda like herding cat's, but a little fiddling and you will get it.

You can still rotate the stopper with the hard uniflow config for minor tank height adjustments, as a matter of fact, this way I find it more effective than with a soft uniflow.

As Ted stated, I would still try the easy stuff first - HotPlug(try a couple different kinds)/Rotate stopper/then re-plumb the uniflow.

EricV

Guys,

I am trying to get my 60 machine sent up with a consistant run and am having some issues, Here is my current setup:

inverted ST G60, barker reworked
Clunk tank with stunt setup. (pickup with uniflow line soldered to clunk) Running Pressure
12-5 zinger prop, I have tried everything from a 13-6 bolly, 13-6 zinger, 13-6 TF powerpoint,13-5 zinger pro, 13-4 zinger, 12-5 seems to fly the best
68 foot lines

Here is what is happening:
Very consistant 4 cycle upright
Very consistant 4 cycle inverted
breaks into a c cycle in vertical
slight acceleration in inside maneuvers
rapid RPM pickup in outside maneuvers.

I am close to having a flyable setup but the outside maneuvers are just still flying to fast.

Any ideas? Please help??

Hi Tim

Your have some good advice, next thing you should do is take it off of pressure, pressure will and DOES  magnify any problem you have with fuel delivery. Just look at the white foaming mass that you have in your tank when the pressure line is hooked up to the muffler. 
Pressure also kill off or retards the 4/2 break, and makes the engine "dumb" as to when to break, pressure will also cause problems if you have things like very tiny leaks or holes in tubing , seals, etc.
Another thing the engine will cycle back and forth much faster if you are NOT running pressure. One of the best setups if your using plastic clunk tanks is to run the hard uniflow vent line in a  U  shape right into the front inside of the tank. many times a hard tubing set partway into the tank will change speeds as soon as the tank gets low enough on fuel to uncover the tank. We tried this on several engines and the plane would pickup 2 tenths everytime the vent was uncovered with fuel.  We  slide the hard vent back and forth and could make the change happen anywhere from the first, middle, and near the end of the pattern. it was very predictable where the speed up would happen.

On the engine If your running a little rich in cool weather, this makes the glo plug even more critical to heat changes from the fuel charge being loaded up on the glo element on inside maneuvers (making the engine go richer-slower) and the fuel charge being pulled away from the glo element on outsides (making the engine run cleaner and faster). If you have a weak or cooler glo plug this will show up much faster in cooler weather, and will make any tank alignment issues much more critical.  The fix for this is to make sure you have the tank perfectly setup for even inside outside runs, and run a good hot glo plug.
Another caution is when you change the venting inside the tank the tank height will many times act as if it were moved, also if you go on and off of uniflow pressure the tank will many times act as if it has a height change.

A question is this a ringed or  ABC  G 60?

Regards
Randy

Good luck with your  setup

Wouldn't it be nice if someone like Sullivan would mold a tank that is shaped like a typical metal wedge tank but with the stopper located in the front just like the square tanks?

Problem I have from an "eyeball" point of view is that the fuel inventory in level flight for example, in a square tank is at an angle to vertical  against the outside of the circle due to accelerations of centrifugal and gravity forces. While the clunk will follow the fuel pretty well during the sloshing in maneuvers, the uniflow tube, if it is ridged and on the outside tank wall can become uncovered when the fuel level drops to something on the order of a quarter tank.

If we had the plastic wedge tank, it would be relatively easy to plumb with rigid tube trough the stopper and provide a whole bunch of positional adjustments to the tubes with an added bonus of being able to see the "tweaks. JMHO

Dick, it would be nice, but from my experiences the shape differfence isn't a problem.  Placing the uniflow towards the middle of the tank doesn't logically seem right. One imagines there's going to be a problem at some point.
 
I can tell you from my experience, using this type of tank for the last ten years, is that it isn't the problem one might think it would be.

Perhaps it's because of the manuevers we are flying. at the middle of the manuevers, we are doing the Eights. For the most parts, for the rest of the flightwe are flipping back and forth between insides and outsides. The fuel is really getting moved around, but not really stacked up agianst the outside wall as it would be in level flight.

It's easy to set a tank up, and they are cheap enough, that I'd urge you to try one, despite the "logic". I especially like the ability to adjust the tank height by rotating the uniflow, without having to raise or lower the tank.

All,

Thanks for all of the input, I have a lot to chew over and there are a lot of points of view.

Randy,

To answer your question, it is a ringed engine, I have experimented with and without pressure, I do not run pressure on some of my other planes and I agree I get a more consistent run, but for some reason the ST 60 seems to like it and calms it down. This is the second airplane I have had it in and besides a little burble when it went over the top of the eight back to upright, it was very consistant.

I have not tried the engine without pressure on this plane and I will try the uniflow not tied to the pickup. I have to admit being an Old RC guy, I never really quite understood tying the uniflow to the pickup line anyway, but someone older and wiser than me said that is the way it was done for stunt with a clunk tank so I gave it a try, it seemed to work on the last plane.

The plug seems to be a possible solution as well, I cant tell you how long I have been using the one I am and just for note it is a Sig Plug. I have also tried K&B with success.

If you have any other suggestions based on this info please feel free

Thanks again.
 

Hi Tim

If the pressure calms it down you may have a venturie that is too large. try a smaller one, on the plugs  try one or more of these, these seem to be the hottest and work best for stunt runs
T Bolt RC long
T Bolt big bore
Enya # 3
Glo Devil 300  RC long
OS # 8
SIG RC long
FOX  Miriacle plug
Pay close attention to the RPMs  inverted and right side up. you can check this on the ground before you fly it also, Then pay attention to the break inside and outside, getting the break the same is more important that having an exact lap speed both ways within reason

Randy
Also keep the tank as close as possible  to the engine.