Depending on which kit you're building, you'll probably need to buy most of the electric flight system separately. Some kits include the motor, propeller and a switch, while you'll need to buy a complete system for others. So in this guide to electric power systems, we'll start of by looking at a typical electric flight system included in a kit. Then we'll show you a more commonly used system that is much simpler and lighter. Finally we'll list some examples of proven motor/propeller combinations to get you started.

Kit Power Systems
Many electric powered model kits include a motor, a propeller and a switch. You will need to supply a rechargeable battery pack and a charger. This system requires your plane to use two battery packs (one for the motor and one for the receiver), and enables you to turn the motor on and off in flight using a servo plugged into your receiver's throttle channel. However this system has two big disadvantages: it requires two battery packs (one for the motor, one for the receiver) and an extra servo, and it only provides on/off control of the motor. The result is that planes powered by this system are almost invariably underpowered and overweight. This is easily overcome by using the system below.

The Typical Electric Power System

A setup such as the one shown here is a much better way to set up your electric power system. It uses a speed controller instead of the switch to provide full control of the motor (not just on or off, but a proper throttle), while allowing you to operate your receiver from the motor batteries, saving considerable weight! For this setup you will need a motor, a propeller, a speed controller, a battery pack and a charger. If your plane is a slow-flying model such as a glider, you might also consider using a gearbox to your motor.

The Motor

Despite being the least efficient and least durable type of electric motor, ferrite cans are the most popular motors used in electric model aircraft. The reason for their popularity is because they are so cheap. Ferrite can motors are actually industrial motors relabelled as R/C aircraft motors. Common examples include the Graupner Speed series and the Great Planes Goldfire. For more information on the other types of motors commonly used, see below.
The Propeller
The propeller you use should be matched to the type and size of motor and the aircraft you intend to fly. There are also a couple more types of propellers apart from the standard "fixed" propeller. If you're building a powered glider, for example, you should use a folding propeller which folds back against the fuselage - this reduces drag when the motor is off. It's also possible to buy electric ducted fan units for use in electric powered scale models of jets!
The Speed Controller
Some form of switch is needed to control electric motors - a fully charged battery could easily take a model out of sight! The standard device used in electric flight is the speed controller. The speed controller has two big advantages over using a switch: They operate like a throttle so you have full control of the motor, and they allow the receiver to be run from the motor batteries, meaning you'll end up with a much lighter model with better performance.
The Battery Pack
Electric flight packs are usually made up of 1.2V Nickel Cadmium (NiCd) or more recently the lighter Nickel Metal Hydride (NiMh) cells. Most battery packs use 6 or 7 cells. When you buy a battery pack, you'll need to choose the size of cell you plan to use. The size of battery refers to its capacity. When choosing your batteries you'll need to compromise between flight time and weight.
The Charger
The most common chargers used in electric flight are peak detect chargers that plug onto your car battery. Peak detect chargers detect a small voltage drop in the battery once full charge is reached, then automatically stops charging. Note that NiMH cells have a much smaller voltage drop that an ordinary NiCd charger will not detect, so the best choice of charger is one that can handle both NiMh and NiCd cells.

Extras
A very simple way of dramatically improving the climb rate of your powered glider is to add a gearbox. Gearboxes slow the motor down, allowing you to fit a much bigger propeller. A glider that struggles to climb at all with a standard ferrite can motor be made to climb almost vertically by adding a gearbox and a bigger propeller! It's not just gliders that benefit either, a gearbox can improve the performance of just about any slow-flying aircraft.

If you would rather have a more durable, more powerful motor than the ferrite can, then the next step up is the ferrite R/C car motor, followed by the rare-earth motor and the brushless motor. These are much more efficient than ferrite can motors, and give greatly increased power. The extra power can be used to improve thrust or flight time. Alternatively, you could reduce weight by using a smaller motor or battery to improve performance.

Electric Flight Setups
The table below provides a rough guide as to which size ferrite can motor you should use in your plane, and what accessories are suitable. The size of these motors refers to the length of the motor (eg. the Speed 400 is 400mm long).

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