Thinking on from my last post. It is possible to use the same L/D estimation to work out the tail-rotor thrust...
If we assume the main rotor blades have a 10:1 L/D ratio, then they are producing a drag force at half the blade length of 400lbs for a 4000lb helicopter.
This is counterbalanced by the tail rotor, which is about 3 times further out from the main rotor shaft, of 400/3 which is 133lbs.
All these figures are very approximate, but should be somewhere near enough.
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