2007 Scale & Non-Scale Events

 

Electrifying Larger Models

Do you want to build a 25%, 30%, 40% or larger Park Flyer?  Do you know how large of a motor you're going to need or how/what to power it with? If you're not sure read more ...Most modelers use the watts/pounds ratio to ballpark the power requirements for their electric model projects. The following power/weight ratios are fairly appropriate for matching flying styles to your various flying projects. 

Using the guidelines below, Scott Stoops used the following to electrify his 77” wing span Carl Goldberg Edge 540; 3D style or 150 watts/pound was his target performance.

Slow Flyer Trainer  - 50 watts per pound

Scale Aerobatics - 100 watts per pound

3D Aerobatics - 150 watts per pound

So if you work backwards, the Edge is advertised at 12.5 lbs – 13.5 lbs if you used a 1.10 – size glow motor. Knowing that he’d add some weight using an electric power system, he estimated that that his final project would be in the 15.0 lbs range. Using that weight as a baseline he knew he would need at least 2250 watts/pound, so set his goal to be 3000 watts. 
 

There are many ways to achieve the 2200 – 3000 watts, so start with this basic equation and build backwards.

Watts = Volts x Amps

  

Knowing he wanted roughly 3000 watts, he first looked for a battery pack that could deliver that level of power. A Duralite 10S 5000mAh Li-Poly pack could deliver 100amps while still maintaining around 38volts under load. Knowing the available Volts and desired Watts, we solve the equation above to determine the rough amp load required to deliver that power.

In this case we can see the 79amps (3000W/38V) is well within the capability of the Duralite cells. The final combinations was the Duralite 10S batteries, Castle Creations Phoenix 110HV brushless speed controller and the Astro 120 which is advertised to be a 1.20 – 1.40 – size replacement, most think its closer to a 50cc gas motor with its ability to deliver up to 4000 watts. With a Kv (RPM/Volts) of 275, this combination gave him a set-up turning a 20x10 APC E in the low 7000 rpm.

Good luck with your large electric project!

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