selnekav

Can someone explaine me what is the tehory that stand behind the need to set the engine 2 degree to the right ?

thanks,

ooooo

It's called "right thrust"..... when the propeller is spinning, it tends to torque to the left. Setting the enine a degree or two to the right will counteract this left torque and the plane should run/fly in a straight line (providing there is no other forces coming into play eg:-bumpy field, cross-winds etc).
Boat props do the same thing also and should be offset the same way to counteract torque.
Having said this though.....torque could be overcome by adjusting your trim in flight or motion.
If on take off and torque is pulling to the left.....input some right rudder control to keep you tracked in a straight line. Hope this helps. I'm sure someone will have more input to help you with your question.

selnekav

Thanks,
My engine is already shift 2 degree to the right but the airplaine still pull to the left
i want to mention that i put 91FX on airplaine that designted to 61 so

1) Do i need to shift it more then 2 degree ?
2) Why do i need to use the rudder to counteract the torque ? why not the ailrune ?

ooooo

I don't believe you can get the engine shifted more that 2 degrees on a normal engine mount if that much. Don't shift anymore though. Use your trim to counteract left torque.
ON the ground.....the ailerons are of no use (except for cross-wind takeoffs)...the Rudder will keep the plane tracked down/up the runway in a straight line for takeoff. In the air...you can use a combination of both trims. A .91 engine in a 60 size plane is a lot of power.....I would have personally use a .78 size engine if I wanted more power for 3D or aerobatic flying. The 91 size engine with a bigger prop will have more left torque which may be contributing to your problem.

Mac-

I agree, the .91FX is too powerful for the model and is producing too much torque!

CafeenMan

Walt Schroeder told me once that thrust settings are not affected by engine size or power. If they need a thrust adjustment then they'll need it for any engine. I don't know if that's true or not, but he knows a lot more about it than I do.

But the way to find out if it's right or not is to get a trim chart and go through all the tests. You can guess all day about whatever, but if you go through the different maneuvers you will know for sure if the plane needs a thrust adjustment or a different trim adjustment. One comes in some of the Futaba manuals and may be available on their website. I think the aircraft proving grounds has a trim chart as well. If not, just do a google search for radio control airplane trim chart and you'll find one.

http://www.geistware.com/rcmodeling/index.htm

TerrellFlyer

On some planes/engine/prop set ups you'll need more right thrust than others to fly the plane the way you want it to fly.On some larger engines with hi torque props you'll need more thrust,in the older days when the engines were spinning 18000 rpm more or less the torque factor was not there,now with low rpm engines and hi torque props the p factor is a biggy. After you have trimmed your plane then if it pulls to the left add more right thrust,one way is to add washers to the engine or motor mount to get the handling you desire. On one of my planes I have a g62 with 22x10 prop,at very low rpm on the runway the plane wants to pull right,normal speed and up its tracts perfect. On some planes I've flown,they had over 6 degrees of thrust to fly great,play with the thrust angles,thats the only way to learn.

Rodney

Almost any model performance can be improved with a slight thrust adjustment. Some may require as much as 5 degrees (rare) right thrust and up to 5 degrees down thrust. A high wing model will almost always require more side and down thrust than a mid or low wing configurations do to fly well at all speed ranges without having to constantly change trim settings when speed changes. Many of your model kits have this offset built right into the firewall so you may not realize how much you have. If you find you are always having to change trim settings with power changes, experiment a little, you may make a pleasing improvement.

KENB85

I NEVER HEARD OF HAVING TOO MUCH POWER - WONDER WHAT THAT COULD MEAN