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Proppng Down?????

I have heard the phrase "propping down" many times in many videos. What does this mean? I know that this is when using a larger battery, but how do you know how far to go? Example, using the Turnegy 500mAh 2s 20c battery w/ 8X4e propeller. Now changing to a Turnegy 500mAh 3s 20c battery and having to prop down to a ????? size prop. I have no idea what this means. Can anyone please explain what this means?

Many Thanx

Ak Flyer

Fly the wings off
it's the voltage times your kv rating of the motor that determines the prop rpm. example:

2s = 7.4v x 1000 kv = 7,400 rpm at full throttle.
3s = 11.1 x 1000 kv = 11,100 rpm at full throttle.

Each time you go up a cell on your battery you essentially add 3.7 x motor kv = XXX to your rpm. Therefore, you need to change the prop accordingly because it's going to spin faster at all throttle positions. If you try to spin a larger prop with the same speed, you will draw a lot more power and your battery esc and motor will all get much warmer. If you change the prop to match the new speed then everything works as designed.

Hope that helps, if not let me know and we'll hit 'er again.


Old age member
I am normally using an 8*4 and 350 mAh 2 cell for indoor flying and a 7*4 or 7*6 with a 3 cell 500-800 mAh for outdoor flying (delta type wing).