Customer asks a good prop question with implications…..

Hi Dave,

Quick question about the APC props. I note that for multi-rotor the sizes seem to be with 4.5 pitch. Is there a reason why I should not use say, 9×6 with 9x6R for multi rotor craft?

Thanks
David

Answer:
Hovering props or props that produce best thrust in static air tend to be pitched about 1/2 of diameter or less. As you add more pitch, they can fly faster, but have less bite in static air. They can actually be stalled and have less lifting force until the prop gets to moving forward. This is also why props which are the same otherwise make more noise with lots of pitch. Initially they are stalled or partially stalled. So, if you need more prop than a 9-4 to apply the power to the air you have available in your system, you go to 10-4, not a 9-6. Certainly a 9-7 would be such a bad choice as to be worthless.

All this is considering the model is essentially hovering all the time. Even forward flight isn’t quite as forward as an airplane. Other types of flying and machines can have other considerations that make higher pitch (relative to diameter) correct but this is unlikely in all multi-rotors except maybe a racer.

What we call these props is 1/2 square. Meaning pitch is about 1/2 the diameter. A pattern aircraft or war bird might use a 3/4 square (like a 10-7 or 11-8) or even a square prop (like 12-12) because hovering is not a required and speed is more desirable. These setups are poor on hole shot, but once they get moving they really go.

Dave
Hi Dave,

Quick question about the APC props. I note that for multi-rotor the sizes seem to be with 4.5 pitch. Is there a reason why I should not use say, 9×6 with 9x6R for multi rotor craft?

Thanks
David

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First Manned Multicopter Takes Flight!

Check it out, see if you can figure out the controller logic to make this safe as possible. A step beyon fly-by-wire for certain. Maybe with some aluminum, rivits and 4 quad boards you too could be seated above a blender. 😉

Dave

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The CrashCast

Check out “The Crash Cast”, a fun and informative RC podcast from the big ol’ state of Texas. I met Micheal “Crash” Hancock at 2011 SEFF. He’s a real RC junkie. His show shares a lot of good information. He is a scratch builder, home CNC expert and has a fondness for Multi Rotor aircraft. His complete support site for show topics can be found at: All Things Crash.

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Quad Copter Designers Kit Gets 4 Massive Motors – 1.6kw

Photo by Mark Harrison / Motor Mounted

Mark Harrison in San Francisco East Bay posts up a build log and test flights of the Quad Copter Designers Kit.  Project is dubbed Arcticopter II.   Check it out.

http://eastbay-rc.blogspot.com/2011/05/arcticopter-ii-build-part-1.html 
http://eastbay-rc.blogspot.com/2011/05/arcticopter-ii-build-part-2.html 
http://eastbay-rc.blogspot.com/2011/05/arcticopter-ii-test-videos.html 
Thanks for the feedback Mark!

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Stinger Quad Copter Test Flying Today

Did a flight test on the soon to be released Stinger Quad Copter.  However, I failed to properly secure a set screw, losing a motor on a Quad copter is a problem.   After airing it off (landed in a puddle) I’ll wait for it to dry completly and remount the motor.  More flying Wednesday.

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