Motors, Batteries, Speed Controls

Most kit-supplied motors are of the tin-can variety and feature ferrite magnets. They are cheap and are essentially throw aways since there are no replaceable parts. They generally are 70-110 watt motors, roughly equivalent to .049-.09 glow engines. If a kit is built lightly enough, one can usually have sufficent power to fly reasonably.

Most high-performance electrics use rare-earth cobalt-magnet motors, depicted above. These motors are fully serviceable and yield much more torque per ounce than their tin-can brethren. They can be gotten in sizes from 90 watts to nearly 2000 watts, roughly equivalent to .049 - .90 2-cycle glow engines. The cobalt motors are more expensive, but do not require maintainance and are built to last forever.

As an intermediate solution, there are some manufacturers of cheaper ferrite-magnet "can-type" motors with good power performance (the Graupner Speed 400, 500, and 600 series is a good example).

Direct-drive motors are the electric counterparts to 2-cycle engines. They spin small props at very high RPMs. Many sport and aerobatic planes will opt for this route, as should every pylon racer.

Gear-drive motors allow one to spin BIG props at lower RPMs, which loosely corresponds to much higher thrust at lower flight speeds. This is especially useful for slower-flying planes, or planes where top-end speed is less important than vertical climbing ability. Gear-drive motor systems are the extreme electric counterparts of 4-stroke engines.

A word on flight duration: Motor run times are calculated assuming 1700 mAH cells. Flight times are estimated for sport planes by assuming that 1/2 of the motor run time will be at full throttle; the remainder will be at 1/2 throttle for sport-wind cobalt motors and 1/3 throttle for FAI-wind cobalts. 2 minutes of glide time is assumed at the end. This is a conservative estimate -- most sport planes will do better than this, and certainly all sailplanes should do remarkably better!

On target model weights: All suggested model weights are for sport and aerobatic planes. Sailplanes and other low-drag, high-lift designs can easily add 50% more weight than suggested for sport planes.