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Old Dec 31, 2012, 11:03 AM
Martyn McKinney is offline
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Toronto Canada
Joined Dec 2002
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Quote:
Originally Posted by Bruce Abbott View Post
Most props achieve best propulsive efficiency at about 70% of pitch speed.
This is not correct.

Props are designed to have the best lift-drag ratios at Geometric Pitch Speed (RPM X Pitch).

Props might develop their best efficiency at 70% of VIRTUAL PITCH SPEED or Zero Thrust Speed which is 20 to 40% higher than Geometric Pitch Speed depending on the P/D ratio.
Quote:
Originally Posted by Nereth View Post
Which would be more energy efficient from the battery at the same speed?.
My interpretation of this question was that the aircraft in both cases was flying at the same speed.

Doesn't this imply that the power dissipation in both cases is the same and if the motor were being operated in the flat portion of its efficiency curve that the power requirement would be approximately the same?
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Last edited by Martyn McKinney; Dec 31, 2012 at 11:16 AM.
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