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Old Feb 23, 2011, 07:39 AM
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Jack
USA, ME, Ellsworth
Joined May 2008
18,096 Posts
Quote:
Originally Posted by rgoble View Post
After dusting off the old math books and re-learning stuff I forgot ages ago I was able to figure out how to use the power law to come up with the best fit lines.

Attached are 2 screen shots of graphs for two different props. It will take me a few more days to get this to a point where everybody can use it on the site.

Robert
Robert,

I'm not very smart about the math and process that results in those graphs but, for me, those are the kinds of graphs that I would really like to see when I was contemplating motor and prop choices.

One question I have is about the larger number of points in the APC curve and the fact that the points deviate less from the line than the points in the GWS curve.

Is that a reflection of having more samples for the APC prop and there being less variation in the RPM as the prop was tested? Or is it combination of both of those things?

I think in the end, when I am deciding prop choices, one of those two props will be chosen for use based entirely on my "seat of the pants" impressions from flight testing.

I would tend to choose props for flight testing based on curves like those. And then finalize a choice with flight testing.

Jack
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