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I am looking for any information concerning variable diameter propellers for outdoor duration free flight. I have read several mentions of such a beast which have piqued my interest. Any informtaion is greatly apprecciated!
Derek
@Dan Berry wrote:
Well, in a technical way of speaking, isn’t a folding propellor a variable diameter prop as well?
Mmmmmmmm, maybe. But then again, it does not rotate when it folds.
> isn’t a folding propellor a variable diameter prop as well?
Not in my view. The blade folds only after it has stopped rotating, at which point it’s no longer a propellor ….
I recall seeing one drawn up a number of years ago. Maybe in a Zaic yearbook. The problems with a variable diameter prop are numerous. You have to extend the blades a significant amount to accomplish any benefit and the efficiency of the blades drop when extended. Too much blade area at the tips and none near the hub. You also mess up the pitch distribution because the blade angle of attack doesn’t change, just the blade position.
Bill, The issues you bring up are the reason that I am looking for information. I remember reading in several articles ( I think they were in the Sympos) that a Variable Diameter Prop could be an area for exploration for the 30 gram wake motors. The articles did not go into any details though.
I have several ideas on how I could build a hub that would change the diameter by 1 – 2 inches. It would be a challenge to build and even more of a challenge to adjust for propeller speed, so I was wondering if there were any articles exploring the concept in detail.
I know that they are very effective in indoor, but how about outdoor?
Derek
Just a thought. Perhaps you mean variable pitch, rather than diameter?
Some of the indoor models do use vari. pitch as mentioned, controlled by the torque.
Gos said:
Just a thought. Perhaps you mean variable pitch, rather than diameter?
Thank you Gos for the reply. I am familier with variable pitch. I am looking for information on variable diameter. JIm Richmond has used one in indoor, and I have see references to them for outdoor. One thing you learn pretty quickly in Freeflight is that just about everything you can think of has been tried by somebody in the past. I am hoping somebody would remember an article or to concerning variable diameter props, if indeed articles about them actually exist.
Derek
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