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Old Jun 26, 2013, 06:34 AM
always looking for clouds
socommk23's Avatar
Joined Aug 2010
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thrust angle?

hey guys. just completed the tiger trainer brushless conversion.
massive motor and 15" prop.
the combination creates a massive torque reaction while on power.
the motor is set straight and I believe changing the thrust angle could help eliminate or at least reduce this. but in what direction?

from behind the prop, the prop rotates clockwise and the a/c turns to the left on power.

thanks for your help in advance.

this is the a/c in action.

tiger tug (4 min 3 sec)


it has been converted from tri gear to tail dragger now.

tiger tug maiden towing flights (3 min 59 sec)
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Old Jun 26, 2013, 06:49 AM
Fueled by Arabica Beans
ChillPhatCat's Avatar
United States, NY, Syracuse
Joined Oct 2008
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Thrust angle won't help you with torque, right thrust is primarily to counteract the spiral slipstream which twists around the body and hits the side of the rudder, causing the plane to yaw. What you need is a smaller propeller or longer wings.
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Old Jun 26, 2013, 10:07 AM
always looking for clouds
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Quote:
Originally Posted by ChillPhatCat View Post
Thrust angle won't help you with torque, right thrust is primarily to counteract the spiral slipstream which twists around the body and hits the side of the rudder, causing the plane to yaw. What you need is a smaller propeller or longer wings.
cheers....longer wings may be a possibility. hmmm

would the thrust angle change help it stop climbing when powering up in flight?
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Old Jun 26, 2013, 01:44 PM
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typically you wnat 2 or 3 degrees of right and down angle on the motor. Yes down thrust will help control the climb on throttle up. Also some throttle to elevator mix will help also. good luck
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Last edited by robbthepilot; Jun 26, 2013 at 01:45 PM. Reason: spelling
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Old Jun 26, 2013, 02:31 PM
Fueled by Arabica Beans
ChillPhatCat's Avatar
United States, NY, Syracuse
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Quote:
Originally Posted by robbthepilot View Post
typically you wnat 2 or 3 degrees of right and down angle on the motor. Yes down thrust will help control the climb on throttle up. Also some throttle to elevator mix will help also. good luck
Yeah, sounds like you're packing plenty of power, so 3 degrees of down probably would be a good idea.
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Old Jun 26, 2013, 02:39 PM
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+1 on down thrust it should not climb under power that gets old real fast and it makes landing a PITA.
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Old Jun 26, 2013, 03:40 PM
Grumpy old git.. Who me?
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Joined Mar 2006
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Gonna disgree with some of the previous posts.. Right thrust WILL help, that's why you find it on most RC planes. try about three degrees to start with and i guarantee it will redudce the tendancy to turn left under power.

For the avoidance of doubt right thrust is when if you look at the plane from above the motor is angled to the right (i.e. the thrust line projected forward is off to the right)

While it's true that right thrust does not directly counter torque it does counter spiral slipstream effect and it counters torque indirectly in the same way as the rudder on your plane produces roll. Bottom line.. right thrust works!


Also a little down thrust will help with the excessive climbing, though some climbing is perfectly normal.
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Old Jun 26, 2013, 04:16 PM
Fueled by Arabica Beans
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United States, NY, Syracuse
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Originally Posted by JetPlaneFlyer View Post
Gonna disgree with some of the previous posts.. Right thrust WILL help, that's why you find it on most RC planes. try about three degrees to start with and i guarantee it will redudce the tendancy to turn left under power.

For the avoidance of doubt right thrust is when if you look at the plane from above the motor is angled to the right (i.e. the thrust line projected forward is off to the right)

While it's true that right thrust does not directly counter torque it does counter spiral slipstream effect and it counters torque indirectly in the same way as the rudder on your plane produces roll. Bottom line.. right thrust works!


Also a little down thrust will help with the excessive climbing, though some climbing is perfectly normal.
I'm not disagreeing that it won't help counteract adverse yaw, but using it to counteract roll caused by too big of a propeller won't do much... That is, if he's already experiencing a roll when he applies power, right thrust is not going to "fix" it. I do believe that he should have a little right thrust in general just for a proper setup regardless of having too big of a propeller.
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Old Jun 26, 2013, 04:21 PM
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Yes, put a few degrees of right thrust on the engine along with down thrust.
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Old Jun 26, 2013, 05:41 PM
always looking for clouds
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thanks guys. I will be playing with the thrust line setup.

just been out and aerotowed my brothers radian and the torque steering shall we call it does make it a handful. so ill be looking to sort it somehow.

towing the line (3 min 28 sec)
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Old Jun 26, 2013, 06:37 PM
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You could also try not using full throttle on take-off. Rather, ease up on the throttle and use enough to ROG, but not so much that it wants to ground loop.
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Old Jun 26, 2013, 10:00 PM
222 km/hr Parkjet flyer
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Latvia, Ventspils pilsēta, Ventspils
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Few degrees RIGHT and DOWN thrust ..... yep - most have it .. it works

BUT

reading the OP - as another says - the torque is too much and really the model needs to have a smaller prop ....

Large diameter creates torque ... pitch creates thrust / speed.

So careful reduction of prop can improve throttle response, reduce torque, still give the speed / thrust ...

Matching prop / motor / model is not only about going UP in prop ... it's both ways ...

Trying to fly a mis-matched model can be a disaster looking for a place to happen ... match it up and then enjoy the flying.

Nigel
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Old Jun 27, 2013, 02:52 PM
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Taking off at 3/4 throttle and letting model lift off with little or no up-elevator may help avoid torque/spiral airflow reaction . Model should be able to fly level at 1/2 throttle, gain altitude at 3/4 to full throttle and lose altitude at around 1/4 throttle as in landing. Right thrust, plus gentle jabs of right rudder help to control yaw to left during takeoffs. Some down thrust helps to control nose-up tendency when applying sudden full throttle.
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Old Jun 28, 2013, 12:02 AM
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Prop doesn't look over-size to me? I don't see anything odd about the model that couldnt be adequately sorted by a few degrees of thrust offset. Often if we are used to prop sizes from i.c power then electric props seem huge. In fact it's not so much the electric props being huge as the i.c. props being ridiculously small (as is required to suit high revving engines)

FWIW I've got a 15" prop and about 1000-1100W or power on my 51" span AJ Slick 3D model and prop effects are no problem. Just add right thrust until the 'torque steering' goes away.. it will be fine.
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Old Jun 28, 2013, 12:18 AM
222 km/hr Parkjet flyer
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Latvia, Ventspils pilsēta, Ventspils
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Quote:
Originally Posted by JetPlaneFlyer View Post
Prop doesn't look over-size to me? I don't see anything odd about the model that couldnt be adequately sorted by a few degrees of thrust offset. Often if we are used to prop sizes from i.c power then electric props seem huge. In fact it's not so much the electric props being huge as the i.c. props being ridiculously small (as is required to suit high revving engines)

FWIW I've got a 15" prop and about 1000-1100W or power on my 51" span AJ Slick 3D model and prop effects are no problem. Just add right thrust until the 'torque steering' goes away.. it will be fine.
The OP himself says in first post that the motor is massive and prop is 15" .. they match each other but based on his saying massive - indicates too big for the model.

As we know - it's not a case really of matching prop to motor ... but the combo to the model. As motor is already fitted - then prop needs to be reduced ... get the torque down to manageable level.

Nigel
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