Torque Roll on take off.

[dav84]

I understand how to combat torque rollon take off using rudder etc and I am led to believe that the size of the prop can effect the amount of torque roll (correct me if i am wrong).

My question is if i change to a three blade prop and go down a diameter size will this reduce the amount of torque roll or will it still be the same as power is roughly the same and there is an extra blade?

My thinking is that as Torque = Force x Radius the smaller radius of the 3 blade will reduce the torque.

[PatMc]

If the reaction can be controled by rudder then the cause isn't torque, the cause is the rotating slipstream.

Re changing the prop - if a 3 blade gives the same power as a 2 blade at the same rpm then the torque must be identical. Power = torque x rpm.

[dav84]

Right ok. Further questions.

If it is torque, what can be done to reduce it?

If it is controllable with rudder and it is the slipstream, how can this effect be reduced?

Thanks

[cymaz]

You can build in some right thrust into the engine. As you look from the pilot seat add some washers or a shim on the left side. This pushes the angle of the engine to the right. Also open the throttle more slowly and gradually.

Hope that is ok

[PatMc]

Use the rudder during take off. If the model's a tail dragger be ready for it to swing left as the tail comes up whilst the wheels are still on the ground. Also don't start at full throttle from a standing start, open up smoothly from the TO run commencing. This makes any swing, whatever the cause, to be more manageable.

[Simon Chaddock]

As PatMc points out

Power = Torque x RPM

So the only way to reduce torque is to use a smaller prop running at higher RPM but you are likely to need a different motor to do it.

Then you have to consider that the overall propeller efficiency decreases with RPM so you have to use a more powerful motor to get the same performance and that means more torque...........

Of course if you have two propeller rotating in opposite directions there is no overall torque.

Edited By Simon Chaddock on 07/05/2013 01:18:24

[ben goodfellow 1]

if its possible bend some toe in to the u/c ie front of wheels closer to each other than rear of wheels

[Peter Miller]

Just to clarify this. The swing on take off is torque induce BUT it is a swing. A torque roll is where the aircraft actually rolls round its longitudinal axis.

If you model lifts off and then rolls and hits the ground it could be tip stalling.

[Piers Bowlan]

Off-setting the engine/motor thrust line by three to five degrees to the right relative to the aircraft centerline will reduce your torque roll to the left after T/O. If the aircraft is just pulling left during your take off run plenty of right rudder should be enough to counter a turn to the left, however check that the geometry of your landing gear is correct, i.e. symmetrical and that one wheel is not binding. Also check the springing on your landing gear is not too soft/weak.

Ensure that you have adequate flying speed before you rotate to take off, as if you unstick at too low an airspeed this will exacerbate your torque roll. A little more airspeed before you rotate will give you more rudder authority.

Just my 2p worth.

[dav84]

Thanks for the feedback so far. It is the rolling once the wheels leave the ground that is the issue.

From what people have said so far I need more airspeed before take off and maybe a bit more side thrust. Airspeed maybe the key as i have been able to "catch the roll" a few times.

[Peter Miller]

Sounds like a tip stall when you take off too soon.

We had a very heavy model in the club, bags of power but if it wasn't really flying fast it would just flick and go in.

This is caused by one wing tip stalling aided by torque.

[dav84]

Thanks Peter, would adding more side thrust help to reduce the torque effect so I am only fighting the war on one front.