<div style="margin: 0in 0in 0pt">HELP WANTED:</div><div style="margin: 0in 0in 0pt">I am new with electric rc flying, with park flyer experience, and want to covert two balsa planes from glow to electric and need advice for electric power and controls selections.</div><div style="margin: 0in 0in 0pt">Plane 1: glider, empty weight of 18 oz., wing span of 70&rdquo;, wing area 540 sq. in. 38&rdquo; over all length.</div><div style="margin: 0in 0in 0pt">Plane 2: high wing trainer: 37&rdquo; wing span, 296&rdquo; wing area, empty weight 14.5 oz., 30&rdquo; over all length</div><div style="margin: 0in 0in 0pt">Both planes have elevator and rudder only but want a 4 channel transmitter for the future.</div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt">I need equipment selections for a radio, receivers, flight batteries, esc, servos, motors, props and adaptors (prop savers), etc.</div><div style="margin: 0in 0in 0pt">THANKS</div><div style="margin: 0in 0in 0pt"></div><div style="margin: 0in 0in 0pt">Jim</div>

Welcome to the RCU forums!

Some general information can be found here:

http://homepage.mac.com/kmyersefo/sitetoc.html

And at the bottom of the header bare is a site called Watt Flyer, one of the best electric plane sites I have seen.

One of the most interesting and challenging parts of the conversion is power selection. Probably not for the glider, but for the trainer, well, it can be. The easist part of that is already done for you, it's a trainer, so you won't be going with a high torque high power (meaning high wattage) power system. The power system is the battery, the ESC, and the motor.

You will have to choose if you want brushed or brushless power. There are some web sites, and I believe Wattflyer is one, that has conversion info that can help you with the power to weight or watts per pound ratio. This is important, and, as I said, challenging because you have to consider the entire weight of the plane, which includes the motor with prop, esc, battery pack, receiver, servos, and fuselage.

Here are some guidelines:

1. Power can be measured in watts. For example: 1 horsepower = 746 watts

2. You determine watts by multiplying ‘volts’ times ‘amps’. Example: 10 volts x 10 amps = 100 watts

Volts x Amps = Watts

3. You can determine the power requirements of a model based on the ‘Input Watts Per Pound’ guidelines found below, using the flying weight of the model (with battery):

50-70 watts per pound; Minimum level of power for decent performance, good for lightly loaded slow flyer and park flyer models
70-90 watts per pound; Trainer and slow flying scale models
90-110 watts per pound; Sport aerobatic and fast flying scale models
110-130 watts per pound; Advanced aerobatic and high-speed models
130-150 watts per pound; Lightly loaded 3D models and ducted fans
150-200+ watts per pound; Unlimited performance 3D and aerobatic models

4. Determine the Input Watts Per Pound required to achieve the desired level of performance:

Example:

Model: E-flite Brio 10 ARF
Estimated Flying Weight w/Battery: 2.1 lbs
Desired Level of Performance: 150-200+ watts per pound; Unlimited performance 3D and aerobatics
2.1 lbs x 150 watts per pound = 315 Input Watts of total power (minimum) required to achieve the desired performance

5. Determine a suitable motor based on the model’s power requirements. In this case, you will need a motor/esc/battery combination for 30 amps continuous... 3 cell LiPo at 11.1 volts (nominal) is 315/11.1=28.xxx amps, round out to the higher 30 amps.

So, get your paper and pencil out and work out the details. Let us know if we can help.

CGr.

Based on what CG retired posted, you'll need about 100 watts for your trainer, and can get away with a bit less for the glider if all you're using it for is to get up to altitude and find a thermal. Check what engine was originally recommended for the trainer and what props were recommended, then pick a motor with a KV rating to turn that prop with near 100 watts of power. Then you'll need an ESC that can handle the amps, and a battery with a capacity that will let you get about 5 minutes of flight at max amp draw. So if you need 15 amps, you'll need a battery around 800 mah in the right voltage for your motor specs.