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Old 06-13-2009 | 02:22 AM
  #26  
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From: Middletown, CT
Default RE: Too much thrust angle

No problems, I'm glad you found it now rather than later, nothing is worse than spending weeks building a plane just to find out at the field that it flies like a pile of dog poop just because you overlooked something as simple as thrust or worse yet, CG. I've been keeping tabs on the build thread, and I must say, you two are doing a good job so far, just remember, slow down and think before putting the glue down, it will pay dividends to study not only the instructions, but the plans as well. I got caught with my pants down on the extra, in one place, I ended up riping off the bottom rear ply plate and cutting a new one because I screwed up, live and learn I say.
Old 06-13-2009 | 06:15 AM
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From: Perth Australiaaustralia, AUSTRALIA
Default RE: Too much thrust angle

as long that you got 2 degress min right thrust to counter the torque
Old 06-13-2009 | 07:16 AM
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Default RE: Too much thrust angle

hi  in 24 years of building -i have never put any -right thrust into my aircraft-  just feel it is more efficient if the engine is at  zero degress with the stab and wing at zero degrees  - my instructor building for another 30 years felt the samemy planes fly unrealjust my  2 cents-i have been told that some down thrust will help fly a plane invertedthat is tail heavy-which is required for 3 D flying -but have never done that to datethe   friend that told me that- is resposible for inventing three -3D manouvers YURI HIGUCHI
Old 06-14-2009 | 10:59 AM
  #29  
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Default RE: Too much thrust angle

An airplane will fly with zero-zero thrust set-up, but they usually fly better with thrust adjustments.  Unfortunately, there is no simple answer of what the best thrust angles are, but if they suggest a certain amount on the plans, then you have a good starting point.

It is very typical to have a degree or two of right thrust, but this depends on the flying speed, prop size, and configuration of the model.  A slow biplane with lots of power with a big prop usually takes a whole bunch of thrust and incidence adjustments to perform well, while a fast clean design like a pylon racer may not. 

The common method to determine right thrust requirements is to pull the airplane into vertical flight to watch the track on a calm day.  If it just goes straight up, you have it right.  If it start pulling to the left, then you may need to add right thrust.
Check it by doing the same manouver at full power, and by chopping the throttle to idle just before pulling up.  This way you can differentiate thrust problems from rudder trim problems.

Even with the correct thrust adjustments of the engine and the rest of the airframe, you still have to fly the airplane.  What this means is it takes a touch of right rudder to do inside loops and a touch of left rudder to do outside loops so that they track.

As they say in full size - step on the ball.  There is quite easy to see the need for rudder with the increase of pitch(you pull back and the nose goes left).  The reason it happens in prop driven airplane is due to the prop blade having different angles relative to the air it is moving throught.  The downward traveling blade is at a higher angle than the upward traveling blade when the aircraft pitches up.  So (with the conventional direction of engine rotation) the right side of the prop is pulling more than the left side of the prop (if you are in the cockpit looking forward).
Old 06-14-2009 | 01:50 PM
  #30  
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From: Hemderson, NV
Default RE: Too much thrust angle

Old time pattern trimming HP. After building a number of the SS planes Ihave found them in need of around two degrees of right thrust so to keep the crank at center that means about 1/8 or so to the left when mounting the engine. Depends on the length of the thrust plate from the fire wall.
Istill have my pattern trimming charts on my wall and still use them with every new plane I build. Iset things at zero but then move stuff around as needed. A lot just depends on the plane though.

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