Dan, I need to lean it out because it runs so darn rich in the air and I was trying to fix that with needle setting. Come to think of it, if I could reach out and adjust the needle just right in flight then it wouldn't even run on the ground.
I think on the ground the vent in the tank is spraying bubbles on the feed line then, in the air, the bubbles go somewhere else and the feed line gets full fuel.
I'll try smaller tubing on the vent and re-positioning the spray bar, those things can't hurt but, I'm going to pop the tank apart and have a look.
Thanks for all the help,
Motorman
The first time you had to do that should have been the last time you tried it. That should have told you volumes about your problem. Especially if you repeatedly use the same tank set up as on other airplanes you have success with, and you experience problems on a new airplane. If you made the tank, and something ain't right, a simple tank change should answer the question. If the problem persists, it's something in the engine or fuel delivery parts between the tank and the engine. Trying to effect a major change in an erratic engine run with just a drastic needle change is a real crap shoot, and it sounds like you are making a lot of assumptions about the condition of the engine that aren't correct. If you have a known, good engine of the same kind that is performing well on another model, bolt that sucker on while keeping everything else the same. If the problem persists, it ain't the engine. If the problem goes away, you need more break in on the engine. Prop pitch and/or diameter may be too high and over loading the engine, especially if it's still a little shy of being fully broken in. Someone mentioned spray bar orientation. Some where here on the forums is the results of some one doing a flow bench test on the best position for the spray bar hole, and the results were pointing slightly back towards the engine. That is the area in a restricted venturi that has the highest vacuum. It's how I always set mine up, because it always works. If I try to do one thing in this hobby, it's strive for consistency. You get consistency by doing the same things that you know work well every time you build a new airplane, especially while you are starting out in competition and working your way up the ladder. If the engine, plug, tank, prop, fuel line, filter and fuel are the same that you have used in the past, and you have this problem, then isolating it by simple interchanging of parts is easy and can be done right at the circle at one flying session. The last stunt model I built was a profile stunt/scale model of the real Dusty crop duster airplane. The model is basically a Twister with a few dimensional changes and shapes to achieve the look I wanted to fly scale. To fly stunt, I take the carb and electronics off, put on a venturi and needle valve and go fly. I installed everything from the engine back to the tank that I had success with in the past. That is tank, tank plumbing, tank location, fuel line and filter, prop, plug, and fuel. The model was built and bench trimmed primarily as a stunt model, with controls, settings and alignments that I know worked well for me in the past. The result was I was able to do the pattern with the airplane on the very first flight, including the reverse wing over, with a pretty good degree of confidence. That is what I try to impress on newcomers that have these kinds of problems. Find something that works and stick with it. It's a whole lot more fun at the flying field flying your airplanes than it is trying to diagnose a problem because you used a Heinz 57 variety of new and different components that you are not sure of. You also spend a lot less time at the computer asking the internet community to diagnose your problem, and then you have to wade through all the different replies and try to figure out which one is correct! Finding consistency will help you really enjoy the differences between the WORK SHOP and the FLYING FIELD!!!
Type at you later,
Dan McEntee
Topic: blank (Read 2876 times)
