Most modern, electric-powered RC airplanes utilize brushless motors for propulsion. And why not? Brushless motors are much more efficient than their brushed cousins (not to mention lighter and sometimes even less expensive). Similarly, airplane models that were designed to use brushed motors can enjoy a huge boost in performance with an upgrade to brushless power.
Some brushed-to-brushless upgrade projects are just a simple matter of swapping out the relevant components (motor, Electronic Speed Control (ESC), propeller). Others require a bit more planning and modification. My most recent brushless upgrade is a good example of the more-complex type. I'll show you the hurdles I encountered during this project and how I cleared them.
The recipient of this power system transplant is a small electric sailplane called the Skimmer 400. Kits for this balsa airplane were popular during the late 1990s and early 2000s. Like other electric-powered models of that era, the Skimmer 400 was designed around the brushed "can" motors and NiCad batteries of the day. There was never a surplus of power with that gear. So models that performed well, did so by virtue of excellent airframe design. I've found that these types of model airplanes adapt particularly well to brushless upgrades.
My Skimmer appears to have led a hard-knock life. I bought the airframe in very-used condition at a recent RC event. Despite model's wrinkled and tattered covering, the balsa structure seemed to be built relatively well and I did not notice any obvious crash damage. It may be an ugly duckling, but the asking price was only $5. What was I supposed to do…just leave it there?
As originally designed, the Skimmer 400 was powered with a Speed 400 brushed motor spinning a 6-inch propeller. "Speed 400" is just an RC-centric term for the generic Mabuchi RS-380 motor that is used in all types of different applications around the world. It has a diameter of 28mm (1.1"), is 38mm (1.5") long, and weighs 65 grams (2.3 ounces). The intended battery pack for the Skimmer 400 consists of seven 2/3A-sized NiCad cells of 600mAh capacity. Altogether, this system produced about 60-80 watts of power…enough to fly the Skimmer 400 in a leisurely fashion.