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Author Topic: Help - Torque roll & prop design  (Read 306 times)
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ghcrash
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« on: February 05, 2017, 12:02:08 PM »

What can I do to the prop to reduce torque roll?

I made a Mini-stick to use as a test bed for learning about prop design.  It flies well enough on about half power (turns) but torque rolls into the ground if I try for max turns on the rubber.   I know that I can do things to the airframe (washout, wing offset and such) to minimize the tendency to roll under high torque launches.  What I’m curious about is if, and what, can be done to the prop design to reduce the torque felt by the airframe.

 Will reducing the prop’s diameter, pitch or blade area have any effect on the tendency to torque roll?   Which would have the most effect, altering the diameter, pitch  or blade area?

I will take any and all advice.
     George
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Olbill
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« Reply #1 on: February 05, 2017, 12:06:41 PM »

I don't fly ministick but all of them will torque roll. I think your best bet is to start with one of the successful designs. The only ones I'm familiar with are the Poonker and Nick Rays's mini which also flys very well.
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ghcrash
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« Reply #2 on: February 05, 2017, 12:55:57 PM »

I don't fly ministick but all of them will torque roll. I think your best bet is to start with one of the successful designs. The only ones I'm familiar with are the Poonker and Nick Rays's mini which also flys very well.

While this is very true if I was trying to come up with a 'winning' plane.    Again, the intent here is to learn something about rubber prop design .
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frash
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« Reply #3 on: February 05, 2017, 01:18:28 PM »

Two possible hints:

If you can reduce rubber thickness, try to do so.

An expert that I timed for in Ministick, suggested warping the inside (left) wing down about 1/4 in or so 2 or 3 times just before launching. It looks like none of the warp stays in, and you don't want it to stay in for much of the flight, just for the first half minute or less to get you past the troublesome torque roll.

Fred Rash
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dslusarc
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« Reply #4 on: February 05, 2017, 01:35:43 PM »

The way I have reduced the rolling is by model design. Tall wing posts,polyhedral wing and stab, wing offset and stab offset. The model will lean left. Only in high ceilings will I get one or two rolls after launch. I do think higher pitch props , over 2:1 P/D roll less. The reason being at launch I think the lower pitch props have more excess thrust so the excess thrust makes the model climb so steeply the nose comes up then the model starts to stall then rolls on about a 45 degree axis. The higher pitch props at launch seem to have less excess thrust and climb slower so they do not nose up so much so can pull through. When my model does roll it is more a horizontal axis. The model starts to bank left after launch and after about half a circle it may bank more then finally it will complete the roll when it gets close to knife edge, then start to climb out. By then the torque has fallen off a little then climb out is normal. Most of the time it rolls left and stays banked and never rolls. I attribute that to the tall wing posts so the motorstick and rubber have a pendulum effect counteracting the torque.  

Don
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