Cetacean
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Flight distance : 2528264 ft
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Oldmaninwva Posted at 2018-2-28 16:07
Smaller radius prop footprint would also require a change in the speed of the motors that control them, they would most likely have to be cut back a bit.. I have on occasion had high RPM warnings, a smaller prop setup without motor speed changes could cause some problems I would think.
Aloha Oldmaninwva ,
Oh yes, there will have to be quite a bit of engineering but once the goal is set, the engineering is pretty straight-forward. A smaller radius prop footprint with just two blades will require a change of speed of the motors as you note. But, adding an third or more blades also adds more lift surface (or propulsive force if horizontal) to the propeller design. That increase in lift surface area with an added blade at the same rotational speed as the original two blade design can be balanced by further engineering.
You can think of it as the surface area removed from the original two blade design could be added as a third propeller. Then modify the root to tip twist for lift properties to balance the motor speed. Then there are lift efficiencies with airfoil configurations from root to tip that have to be considered beyond the surface area and twist. In the design process, intractable inefficiencies will inevitably show up (the three "ins", LOL). These will become deadweight but with lightweight material, like plastic, the deadweight will not amount to enough to discourage production.
Just thinking about it is fun and that is what guys our age need, more creative thinking and analysis. Great for our brains. (That is our advantage over these young whippersnappers!)
Aloha and Drone On!
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