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Electric Stunt => Gettin all AMP'ed up! => Topic started by: Charles Hofacker on June 28, 2015, 09:06:55 AM
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Here is a fascinating article on propeller efficiency that is directly applicable to our model airplane. I Hope this is not a duplicate post of somebody else. This will take some time to study but it looks to be very worthwhile.
http://m-selig.ae.illinois.edu/pubs/BrandtSelig-2011-AIAA-2011-1255-LRN-Propellers.pdf
Note from the conclusions: "The results showed significant Reynolds number effects with degradation in
performance with lower RPM’s...". But read the whole paper. y1
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Interesting study. But the RPM is off the low end of the chart.
The test RPM's varied from 1500 to 7500 RPM.
These props need to run 14,000 to 20,000 RPM to get into the design range. The test range was at low idle, not flying speed.
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Here is a fascinating article on propeller efficiency that is directly applicable to our model airplane.
I repeat something that's been said here numerous times: for stunt, at least, efficiency is not what is most important. Exceedingly low efficiency is bad because it increases power system weight, but the most important thing for stunt is that the airplane behave well. A magic setup that keeps the aircraft at a constant speed is probably far more important than efficiency.
Interesting study. But the RPM is off the low end of the chart.
The test RPM's varied from 1500 to 7500 RPM.
These props need to run 14,000 to 20,000 RPM to get into the design range. The test range was at low idle, not flying speed.
Some do -- the GWS slow flyer props certainly shouldn't be run that fast.
The biggest takaway from that paper, I think, is that you shouldn't build yourself a really small UAV and just slap a prop on it thinking that you're done -- instead, you should give some thought to the best prop for the job, and you may find that the best prop is not the most "normal" looking.
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Obviously, this was a student paper aimed at getting a grade and finishing the course. The test method and data collection look OK. But the ultra-low RPM renders the data useless for modelers.
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But the ultra-low RPM renders the data useless for modelers.
Uhh, sure.
https://www.youtube.com/watch?feature=player_detailpage&v=pPUtKZ6UCB8 (https://www.youtube.com/watch?feature=player_detailpage&v=pPUtKZ6UCB8)
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Tim Wescott's propellers are always efficient.
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Tim Wescott's propellers are always efficient.
Pbthbthbthbthbthb.