Chris,

Put a "Z" bend in the feed line and twist it down (right side up) and/or up when the plane is upside down. I learned this trick from Jim Aron and it works!

Hopefully you have enough room to do this.

Good luck, Jerry

Chris,

Put a "Z" bend in the feed line and twist it down (right side up) and/or up when the plane is upside down. I learned this trick from Jim Aron and it works!

Hopefully you have enough room to do this.

Good luck, Jerry

Do you have a picture of this?

Chris,
You didn't mention the engine/prop/plug/fuel. If it runs away but comes back after say 1/2 a lap it is likely getting to hot (happens a lot on older mufflered non ABC engines). One thing that works is to reduce the prop diameter by 1/2" or up the nitro % a bit.

The rich inverted is the tank being mounted to low (when the ship is sitting upright). The tank uniflow may be off center causing the condition you describe and will also contribute to the lean run on the inside loops. You would need to move the tank up toward the mounts (upright ship position) or do the uniflow bend trick.

Best,   DennisT

LA 46, 11.5x4, os#6 plug, 10%

I can't move the tank up it is already up as high as it will fit.

I don't know, sounds simple but not for me...

No, it's not simple.  So don't worry about that part.

The "Z-bend in the uniflow" method is for when you have a solid uniflow (which I recommend).  The effective height of the tank is the height of the uniflow outlet inside the tank (which is why I don't like the "uniflow clunk" notion -- it's not really uniflow, IMHO).  So if you can adjust the fixed uniflow's outlet up and down, then you're effectively adjusting the tank.

and there will be literally hundreds of people at Brodaks who can help you sort it out, and most of them would RELISH THE CHANCE to help

What?  Control line folks are helpful?

   If you can't raise the tank, lower the engine. If your Nobler is the ARF version, this is kind of a common problem. Mount the engine on 1/8" aluminum pads, and test fly with out the cowl. If it reacts the way you want, you may try thinner pads, or shim the tank with 1/32" shims.
  A round 4 ounce Sullivan tank may work for you, fits up between the motor mounts a bit more, and you can rotate the stopper a bit also in the direction you need to go. This is what I did on one of my son's ARF Noblers to get the run correct. Once you have teh run even, than you can re-work the cowl or make a new one.
  Type at you later,
   Dan McEntee

It's an old green box Noble.  I don't know how much different it is from the ARF. Good ideas though.

I just had a light bulb moment.  The Z-bend is in the VENT line, specifically the uniflow vent, so it is controlling tank head via where the air gets into the tank (think about hand washing a glass in the sink and lifting a glass of water with the glass upside down)  By adjusting the vent location (turning the bent pipe) it is like taking a flex drinking straw and hooking the rim of the glass to slowly let air in.  (OK, if you don't have kids and occasionally do hand washing this might be an experiment that needs planned and setup instead of just happening)

I am still a little fuzzy about the exact geometry.

On my clunk uniflow setups I try to arrange the rigid uniflow vent even with the spray bar.**  The clunk should be free moving.  The third line is optional if you don't mind standing the plane on the wingtip to fill the tank.  The third line is a standard tank top vent and gets plugged after the tank is full.

Phil

** I did not realize this is what I was doing until now.  This is the light bulb moment arranging the vent to be even with the spray bar.

Use ze hard uniflow tube.

Make Z-bend in ze hard uniflow tube, so that ze tube just clears ze outer tank wall when ze uniflow tube is straight back.

Ze height of ze outlet of ze uniflow tube inside of ze tank is ze effective tank height from ze perspective of ze engine.

Because of Z-bend, if you rotate ze end of ze uniflow tube outside ze tank, ze outlet of ze uniflow tube inside ze tank will move up or down -- zis is how you effect ze adjustment of ze uniflow with Z-bend.

Thank you for that cool drawing! I'll give that a shot! Is the end/lenght of the Z tube critical to the pickup? I'm glad I didn't try to literally shove a Z shaped tube.in Ze tank! I guess this is just a different variation to that John Miller picture you gave me many topics ago? (I can't view that picture anymore since the crash)

Just a comment:  If your goal is to fly Beginner, and if your run is good enough that you can stunt in the beginning, stunt at the end, have enough time, and don't destroy the engine in the process -- then your run is good enough for Beginner.  If you really belong in Beginner then you're not going to be held back that much by a mediocre engine run.

I'm not saying to stop working on the problems -- just don't let any minor problems keep you from going to a contest and flying.