A BASIC GUIDE TO SUCCESSFUL
ELECTRIC FLIGHT

Range Check. As per normal radio control practice always perform a range check before flying, but the electric flyer must also remember to include motor on checks. Any interference caused by motor 'electrical noise' may not be evident at close range when the transmitter signal is strong. If you do experience servo twitching only when the motor is running check the motor suppression.

Rating. Motors, speed controllers, switches, cells, wire, connectors, all are rated as regards the current (amps) that they can safely handle. The current in an electric flight drive system can be measured with an ammeter and is principally controlled by the motor/gearbox/propeller/voltage combination. The speed controller or switch can then be chosen to safely handle this current (allow a generous margin, at least 50% extra). Bear in mind that the motor maximum current should not be exceeded. The fuse chosen should of course be able to handle the expected current. A high rated speed controller will work fine in a low rated system.

Read. 'Queit & Electric Flight International' magazine. A superb UK magazine dedicated to electric flight and gliders. The publishers 'Traplet' deserve our support for such commitment to the cause. BMFA News, the journal of the UK national body has a regular electric flight column, along with most of the glossy monthlys.
'Electric Flight UK' the quarterly booklet produced by BEFA (see BEFA). 'Old Buzzard's Soaring Book' by Dave Thornberg. The best book ever about model thermal soaring. Available mail order from Pony X Press 5 Monticello Drive, Albuquerque NM 87123, USA. Tel. (505) 299 8749.
'Just For The Fun Of It' by William (Bill) Winter, magazine columns in old (up to mid-1980's) 'Model Aviation' magazines (American) . Bill can move you beyond the mere hardware of model aircraft to the pure joy of flying and the realisation that 'strange things can happen out there.'
'Biplane', 'Jonathan Livingston Seagull', 'Illusions' and others by Richard Bach. For enlightenment and pleasure.
'Birdman' by Alan Stewart for an insight into how not to do it, with commitment.

Rules of Thumb. In a typical successful sports model (as opposed to a rules restricted model): The power system (motor/flight battery) will weigh approximately 50% of the all up weight. In the range of 40 to 60% is acceptable.
The drive battery will weigh approximately 33% of the all up weight.
In a sports type model situation (model with a limited glide) for a given motor, battery and model, if you change the size of the propeller, use a gearbox or direct drive, climb fast and glide or cruise around low and slow the overall flight time will remain approximately the same, only the flight characteristics will change.
More volts.... less amps is always better.
Any model that is designed to survive a crash, will crash and not survive.

Running In. The brushes that run on the commutator will benefit from running in, increasing the area of contact. Two dry "D" cells (3v) are sufficient with no propeller fitted. Obtain a cheap battery holder and fit small crocodile or spade connectors to the leads, clip to the motor and leave it running until it stops! If the motor is intended to be used in a single stage gearbox remember to run it in the "wrong" way.

Series & Parallel. With respect to battery packs, cells are always connected together in series to produce the required voltage. Do not connect cells or complete battery packs together in parallel in an attempt to increase their capacity. That is, do not connect two 700mAh battery packs in parallel to produce a 1400mAh pack. Buy the appropriate capacity cells.

Soft Fly. A curious phrase which appears to be used to describe any model drawing at a guess (subjective stuff this) less than 15 amps. Although the advent of SPEED400 racers drawing less than this and being anything but 'soft fly' confuses the matter. The description which originated in Germany perhaps better applies to gentle flying in general, be it powered, powered glider or vintage model types.

Suppression. Electrical "noise" from an electric motor can cause interference of the radio control link with catastrophic results. Three suppression capacitors of 0.1 to 0.47uf capacity will normally cure the problem. Solder one from each motor terminal to the motor case and one between the motor terminals. Keep the wires as short as possible. Some 400 and 600 size motors come with two suppressers already fitted internally (you can see a wire clipped into the motor terminal from within). Often these are sufficient but a third across the terminals is recommended.

Timing. Some motors can be 'timed' others cannot, those that can are generally of the 'buggy' or 540 type or higher quality 'Cobalt' motors. Timing consists of turning the whole back plate and hence the brushes of a motor in relation to the magnets housed in the can. This has the effect of supplying current to the rotating coils to magnetise them either sooner or later, sooner (advanced timing) creates a 'hotter' motor, drawing more amps and running for a shorter time on the same battery pack but producing more revs. on the same propeller. As supplied, motors are timed neutrally so that they can be used in either direction. Timing is not essential for successful electric flight, in several years of flying I have never adjusted the timing of a motor.

Trainers. Not solely an electric subject but worth consideration here as electric power is attractive to, and ideal for, beginners to radio control flying. The title 'trainer' is used, abused and mis-used, probably due to personal opinion, here is mine. Trainers should be split into three categories, primary, intermediate and advanced (or names to that effect), as is the case in full size aviation...

Primary... A high wing design with lots of natural stability both in pitch (elevator) and roll (rudder in this case), rudder/elevator/motor control. As a rudder command is released the model will level its wing quickly, if dived and released it will probably stall but after a few undulations the model will settle back into level flight. If guided on rudder alone when gliding it will make a safe landing without elevator input. Limited to calm conditions but you should not be flying at this stage in anything but. Primary trainers get you into the air, teach basic control and build confidence but do move on to the intermediate trainer before tackling an aerobatic sports model. Examples. High wing cabin vintage model (pre.1950 design) converted to R/C rudder/elevator/motor control, many kits available (Junior 60, Black Magic). Powered glider with polyhedral wing, rudder/elevator/motor control. Specially designed high wing trainer of light weight probably with open structure fuselage and built up wing, preferably with an undercambered wing section built for slow flight, a rare bird unfortunately.

Intermediate... A high wing design with some natural stability both in pitch and roll. Still rudder/elevator/motor control. As a rudder command is released the model will remain in the turn longer and may require application of opposite rudder to bring it back to level flight, similarly elevator control will require corrective action once a dive or climb has been initiated. However the model should still maintain straight and level flight without any control input. Landing will require more precise control of the elevator to control the speed of approach. Intermediate trainers do need controlling and therefore this is really where you begin to learn to fly. Limited to calm or light winds. Examples. High wing cabin model probably with a sheet built fuselage and foam wing although a built up wing is still preferable for light weight. Flat bottomed wing section to give plenty of lift and fairly slow flight. The 'IRONIC' fits into this category and electric conversions of types like the Sig Kadet Seniorita.

Advanced... Still generally of high wing design or perhaps shoulder wing. The model will have a little natural stability but will pretty much go where it is pointed and continue to do so upon release of the control input. Aileron/rudder/elevator/motor control to teach full axis control. Usually of built up fuselage construction with a foam wing of semi-symetrical section making for a faster flying more aerobatic model. The advanced trainer will generally be very similar to fly to the average sports model so can be skipped if this is your next goal.

Above all, find an instructor through your local club.

Velcro. 'The electric flyer's friend'. Velcro is ideal for securing receivers, speed controllers and flight batteries, it's grip is strong enough to keep a battery in place during flight and yet allow it's easy removal for charging. Do not however, use it to fix servos. Radio components do not need protection from vibration in an electric model so foam packing is unnecessary, a little can be used in front of the receiver or switch to protect them in a crash but be careful not to obstruct the cooling air flow.

Voltmeter. The common digital voltmeter is suitable for our purposes. Although not as useful or essential as an Ammeter a voltmeter can be used to measure the voltage present in an operating electric flight system. Hold the probes across the motor terminals as shown in the drawing on the rear cover. For calculation of Watts as described earlier we usually assume a voltage of 1 volt per cell (NiCads) in an operating system rather than try to measure any exact figure.

Watts per Pound. This is a way of looking at the likely power required to fly a particular model at various levels of performance. It is only really valid when applied to a sports, scale or aerobatic type of model, very clean glider type designs are more efficient aerodynamically and can manage with much less power. We have seen how to calculate the watts produced by a particular motor/battery /propeller combination, divide the watts by the total model weight (or proposed weight) in pounds to arrive at 'watts per pound'. Refer then to the following table.

25 - 30 watts per pound. Level flight
40 - 50 watts per pound. Take off from sealed surfaces, reasonable climb. 50 - 60 watts per pound. Take off from grass, sports aerobatics.
70 - 100 watts per pound. Pattern aerobatics, prolonged vertical climbs. The higher value is required for a more 'draggy' aircraft shape.

Wire. Not any old bell wire is good enough for electric flight use. Like the wire wound around the armature of the motor the thicker the connecting wire, or rather the greater the cross sectional area, the easier the current can flow, i.e. with less resistance. Less resistance means less loss in the circuit. Buy only wire sold for the purpose, it has a very high strand count, is very flexible and generally has silicone rubber insulation. Typical cross sectional area required for use below 20 amp is 1.5 sq.mm. Up to 30 amp use 2.5 sq.mm. Above 30 amp use 4 sq.mm.

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