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Old 09-22-2008, 06:24 AM
  #78  
dk_aero
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Join Date: Nov 2006
Location: Bakersfield, CA
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Originally Posted by Larry3215 View Post

My question is - how much of that 50 watt drop is due to the prop unloading and how much is due to the battery voltage dropping?

The second question is: How does that vary from one setup to another?

The third question is: Are there cases when the static power level is LOWER than the inflight power? The corolary being - can a prop load UP in flight, relative to the static condition.
I haven't done or read up on this type of testing, but here's my thoughts (for what it's worth)...

1. Prop unloading vs. battery voltage drop. Need to isolate the two. I think this can be done via static testing. Preferably with a low pitch prop so that static thrust should be fairly constant (i.e., prop is not near stalled condition). Precise measurement of speed, voltage and current... Problem may occur since inadequate cooling will cause an increase in current (increased motor coil resistance). You may be able to correlate voltage drop with current draw over time, thus isolating voltage drop.

2. I would think that battery, motor and prop effiency would affect each setup. Correlations are only possible among one variable.

3. As BEC said, one condition where static power level would be lower is in the case of high pitch props which are stalled at static incoming flow.
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