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Newbie here and need some advise about Engine sizing


Junior Member
So, I have been in and out of the hobby for years. I recently stumbled across Flite Test's show and was floored on how cheap it has become. So I am taking my two sons and starting scratch builds (in addition to my new plane). My question is with electrics how do you size an engine to a plane? Is there some sort of weight to thrust calculator than one can use? Do I look for amps or volts?


Old age member
Amps AND Volts.

For smaller planes you will normally use 3 cell lipo. Calculate with 11 or 12 volts when getting your amps (for the motor rating).
Try not to get more than 50 Amps (for normal planes) - get more cells and higher volts to keep the amps down.
That gives 12*50 = 600 Watts - 6 pounds 3 kg plane normally maximum for a 3 cell LiPo, but in the higher range i would go for a 4 or 5 cell battery.

Lost of other things to concider - KV - rpms combined with the battery voltage to get the prop diameter fitting your needs.

Better to start with a plane.
Find the total weight.
Determine what prop size you want.
Select a proper motor
Select speed controller and battery.

Check the recommended motor and things for an ARF/RTF of the similar type of plane as you want to build.
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