SeismicCWave, on 10 October 2011 - 05:03 AM, said:
If spacing is not an issue there is absolutely no reason to use a three bladed propeller. A three bladed propeller is LESS efficient than a two bladed propeller.
Yes they are less efficient, math does not lie, however, you are wrong saying there is no other reason than space, The Master Airscrew 3 blade props I have started using provide two additional benefits that you are not considering,
First, becuaese the are less efficent, they require more RPM to produce the same amount of thrust, this coupled with the fact that these props pretty much do not flex, this adds a type of stability to the prop plane, reducing a great deal of the vibration, or perhaps to be correct raising the frequency of the vibrations so that it is less noticable to the sensors, to use an analogy, its like driving faster on a bumpy road so that you feel the washboard effect less, Sorry if this does not make sense, but it is 100% reproducable and observable, especially on the Kinjal frame you used.
second, there is a more than significant weight difference between the two styles of prop, in the case of the MASTB the hub is HUGE and all of ths mass is centered around the prop shaft, and the hacker style motors are alsomst the same diamater of the MASTB hub, this is adding a large amount of mass that is rotating to each arm, and rotating much faster too, this also adds even more stability. T
His can be increased even further but inverting the motor and mounting it UNDER the motor mount and the Prop above. Another analogy, imagine you are holding a spinning bycicle wheel and try to move the axel , the gyro scopic forces stabalize the wheel making it hard to move from its spinning plane, now imagine that instaed you have two bike whees spinning and the axel in between is 12 inches (30cm) if you try and move this rig, it will be even more resistant becuase you cave created a second gyroscopic stabilization plane. I dont know the correct terms for what I am saying, but I know I can repeat the effect in an experiment, and therefore I know it is valid. I have taken many differnt flight controllers on default and applied this trick, and it is like pid tuning, it smooths out fliught, reduces jittters and increases stbility, admittedly, this may not have a dramati effect for some aiframes, but it has made the critical difference on many of mine, going from unflyable to flyable.
Bottom line is, at the expence of efficiency you can reduce noise, virbations and increase stability, by using these speciic 3 bladed props. I admit, my cheap gws 3 blade props did not exhibit this tendancy as much if at all. They are two light and flexible to give the added benefits.
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