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Old 10-21-2010, 05:42 PM   #11
Marin
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RE: Operating a twin on one engine and fuel economy

Quote:
Bendit wrote:
Re spinning rather than fixed,*think of*a helicopter in auto rotate mode. If the blades are locked, it will drop like a stone, (not much drag) but if allowed to rotate, they provide sufficient lift (and drag) to reduce the rate of descent.

That's an apples and oranges comparison.* The reason the helicopter "drops like a stone" with the rotor stationary is not because of drag or lack of it but because the stationary rotor blades are producing no lift whatsoever.* When the blades are turning, they can be used to develop lift at the end of the drop when pitch is applied to stop the drop.

A stationary boat propeller generates a huge amount of turbulence behind it, and turbulence is drag.* A freewheeling boat propeller does not generate as much turbulence behind it, thus less drag.* The MIT study made this very clear.



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