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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FPV and Flight Stabilization AMA Revised Policy

It’s important not to fall into the swirling well of panic and paranoia. We so often hear those kinds of reactions from the those less informed whenever the AMA speaks out on a subject. I certainly favor the future development of our hobby to included FPV (First Person View) technologies and flight stabilization capabilities. The AMA is working very hard to avoid having issues with government officials deciding each and every model flying activity needs to be regulated and centrally controlled. PLEASE observe common sense and do your part to help everyone avoid this kind of onerous over reaching oversight that seems to be the trend in America these days. It’s your and my job to do something about it. Check out the revised policy below on the AMA blog site.

AMA Revised FPV Policy

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3D Printed Aircraft Takes Flight

Springfield Ohio’s SelectTech in September of 2011 reports sucessful test flight of the worlds first privately funded 3D printed aircraft. Designed by Frank Beafore and Beth Galang, flown by Jade Lowrey at Springfields Beckley Municipal Airport. Aircraft is powered and guided by electronics from Radical RC. Powered by Himax brushless motor, Castle Creations ESC, and Kypom Lipo battery. The aircraft was manufactured on a Dimension 22 1200 ES Printer which works by fusing together strands of ABS plastic. The printer can make parts up to about 10″ long. The aircraft is an assembly of many sections. The wing panels are made with ribs, skin with a light cross hatch structure under the skin (a Radical RC suggestion) to allow the skin to be made thin and light weight. In each rib with each panel are premade holes to accept the carbon rod spars. Total printing time was about 5 days.

Worlds First Privately Funded 3D Printed Aircraft
Worlds First Privately Funded 3D Printed Aircraft

Generally the 3D printing process is used to make prototype parts to verify designs before making a hard tooling investment. However, SelectTech demonstrates that projects with complex mechanical requirements can be manufactured and put directly into service very quickly.

A story was published in the Dayton Daily News Business section on Nov. 13, 2011.

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