Calculating Torque on a Turbine

[JT673]

So I have a turbine falling through the air such that the free-body diagram for each of its rotor blades would look like:

http://img444.imageshack.us/img444/2504/freebodypy6.png

And the whole turbine spins counterclockwise

I understand that for this case you can split drag into form drag and skin friction, but how is torque being done on the turbine if there's no net force done in the horizontal direction?
Does skin friction apply to the torque?

Thanks,
JT

 

[rcgldr]

The whole turbine spins counterclockwise. How is torque being done on the turbine if there's no net force done in the horizontal direction?

The air is being accelerated clockwise via interaction with the turbine blades, and reacts to this clockwise acceleration with a counter-clockwise torque on the turbine. Eventually the turbines rate of rotation reduces the effective angle of attack and clockwise acceleration of air, reducing the torque until all torques cancel, and the rate of rotation stabilizes.