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Help! Gas to electric

I have a Great Planes Perfect Trainer 20 that I started building in the mid-1990’s and did not finish. I had a Fox 25 that I planned to install. It came from a plane I did a figure 9 with. Three moves (or more later) I am ready to finish and fly. BUT, I don’t want to power this with the FOX any more. I want to fly it electric. I need advice on how to buy the right motor, ESC and battery. This will not be my primary trainer. I will be buying an Apprentice or Carbon Cub for that. The idea for the PT 20 is to simple things with it, nothing extreme.

So I am looking for the right stuff to run on. Anyone with ideas to do this right?



Well-known member
I dont know that plane specifically but just to give to you an idea.

I had a Hangar 9 40 size trainer with a 60" wingspan that I converted to electric. I used a 620kv motor, 80A ESC, 10x6 prop, and 6S 5000Mah battery. Actual amp usage was about 40A at full throttle so I had plenty of headroom. I have heard guys using about 4S batteries on these size trainers. I never did try it but I bet mine could've went vertical with that setup. It had plenty of power. I'd say a similar motor and ESC (maybe a 60A) would work well.


Old and Bold RC PILOT
To select an electric motor to replace an IC motor there is a simple rule. Take the gas engine capacity in Cubic Inches and multiply by 2000.

So an IC motor of .20 cu in would be replaced with an electric motor of 400 Watts. Now the Original prop for the IC motor should be used or one the same diameter and pitch. Now the motor KV for the replacement electric is determined by the battery voltage you wish to use and the prop selected. Just sort through the massive number of offerings and find a motor that develops its full output power on the propeller you have selected using the voltage you have also selected.

It is also quite OK to select a motor that can exceed the output power that the maths dictates but NEVER select a prop either smaller in pitch or diameter than the prop originally specified for the original motor.

It works and works quite well!

Have fun!