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Prop info

CrashRecovery

I'm a care bear...Really?
Mentor
#1
I've looked once again and can't seem to find the info I'm looking for. Why do certain props get used for certain projects? I see motors with suggested props but when it comes time for a project it says to use a different one. Why is that? Like the nutball suggests a 10" prop but why can't a 8,7 or 6 be used? I've broken my 10 & 9 inch props. I think I have a couple 6" left. Oh and is there a reason why it is said to have your motor running counter clockwise? I have a 8" and a 9" pusher prop sitting around, bought the wrong ones. Can they be used and just run clockwise?
 
#2
Nothing wrong with underproping a size or two, matter of fact it will save on current draw....buuuuut dropping from a 10 to 6 is a bit drastic. You will be losing so much thrust I am not even sure the model would stay airborne although the nutball is a different animal and doesn't need much thrust due to its wing loading numbers. Also nothing wrong with using pusher prop in tractor configuration in a pinch so long as you are using a prop saver.....ill advised if using a collet adapter as you may spin the collet and prop off mid flight. As the hobbyking guy says slowfly props are "cheap as chips".....buy a bag full without breaking the bank.
 

pgerts

Old age member
Mentor
#3
Using clockwise or counterclockwise is no problem - just swap 2 of the 3 motor wires to get the motor to run the other direction.
 

Ak Flyer

Fly the wings off
Mentor
#4
Prop and motor size is very difficult to master. Most people go with whatever the motor manufacturer recommends. If you drop a significant amount of prop diameter such as 10" to 6" you will lose a massive amount of thrust. To get that thrust back you have to spin the prop much faster or have a much steeper pitch. Either way it's a compromise. While you may get the same amount of thrust it's going to be different. A larger prop grabs a bigger chunk of the air each revolution where a smaller prop spinning faster might be more efficient at speed. Larger props have more torque effect than smaller props, and a large diameter shallow pitch prop won't stall as easy as a small diameter steep pitch prop. I'm probably just adding more confusion to the pile lol.

If you reduce the diameter, you have to make up for it somewhere. You will never get the same performance unless you change the pitch, or speed up the motor.