This article is written to give you an understanding of the minimum requirements for motorised 7 cell electric gliding and to help prevent the beginner from buying the wrong equipment.

Why a glider? This article assumes that the type of flying that you seek is "soaring", ie floating around the sky looking for thermals and enjoying the long flight times (15-30+ minutes) that these can often provide. This is as opposed to an electric "aeroplane" which is a scale version of the real thing. A lightly loaded polyhedral glider has very forgiving flying characteristics and is a suitable trainer for the raw beginner.

A "scale aeroplane" or an aerobatic model with ailerons will generally require greater flying skills (that the beginner would not attain for some time) and have a greater risk of crash. A scale aeroplane is also designed to run with continuous motor, thus flying times will also be far less - about a third of your glider.

If you are a beginner seeking a glider, you will need a beginner's glider which is stable and forgiving. This means one with a polyhedral wing. Ie, with wings bent about half way out and usually also in the middle.

The evolution of the electric glider. A brief history lesson is worthwhile here to help you understand some of the reasons why what I am suggesting is a good starting place.

The most popular form of electric flight has been based on the "540" motor and 6 - 7 cell battery pack of the types used in radio control model racing cars, or buggies as they are more commonly known. ("540" refers to the length of the motor ie 5.4 cm long.) Out of the buggy hobby came the supplementary equipment including a good range of motors and fast charge/discharge nickel cadmium (NiCd) battery units in that size with plenty of punch and decent on field chargers to support them.

The radio gear that has been used for unpowered gliders, cars and internal combustion engined planes is also of a size, weight and price which matches the needs of the electric glider pilot.

The size, weight and price of the necessary equipment dictates the size and design of the plane most suitable for the beginner. It is also of a size that can fit in the car and can be easily seen 100 metres up, ie thermal territory.

Wingspan will be 1800mm to 2 metres (a little over 6 feet), being the minimum required to carry the required weight at a manageable pace and with an acceptable sink rate. Good size for still being seenat ceiling height.

Construction. Because of the weight of the battery, the rest of the glider must be light to compensate. Otherwise it will not climb steeply enough under power and it will sink too quickly when gliding. It must also be strong enough to cope with a hard landing and, if broken, must be easily repairable. This leads us to a glider made of balsawood with harder wood for the spars and possibly a little light plywood in strategic places. The covering will be of plastic heatshrink such as coloured Solarfilm or Oz Cover (which is paintable). Fibreglass gliders are not recommended as they are hard to fix if broken and are heavy.

ARF (Almost Ready to Fly) kits are readily available but are usually heavy for their size. They look beautiful but so often fly very disappointingly, because of the lack of climbing ability caused by a combination of their weight and the lack of a gearbox to increase the performance in the climb.

Successful training gliders. Kit gliders which meet the required specifications and which I have seen fly successfully include the Defender from Astropower Leisure (03 9763 1632) and from selected hobby shops and the Electra by Carl Goldberg - available from hobby shops. Glider kits which lend them themselves to conversion to electric include the Quiet Advancer, which has a good amount of room in the fuselage for battery and gear.

I have owned an Electra until I crashed it badly at full power (but with no damage to the wings) caused by me not checking that up was still up and down was still down. It could have been repaired but it had been crashed many times before and by then I was ready to move on. My first crash was under full power into the Yarra river! My second, third, forth, fifth, sixth ..... crashes prove that it is a resilient glider and that I was a lousy pilot. Both of these planes are the right size, construction and weight, allow the removal of the battery without removing the wings and are readily available.

This article will now proceed on the assumption that your plane is a 6 foot (1800m) to 2 metre polyhedral glider made of balsa and a little light ply, covered with heatshrink covering and weighing under 1.4 kilograms.

Batteries. From our history lesson above you will have noted the use of the same cells for electric gliders as for cars. These are fast charge/fast discharge batteries combined into packs of 6 or 7. You may be encouraged by shop keepers to purchase a 6 cell pack, as readily available for cars. Don't! 6 cells are usually found to be insufficient in power. 7 cells (ie 8.4 volts) are the better choice and well matched to an 7.2 volt motor. The cells are generally referred to as "sub c's" because they are generally a little smaller than C size batteries. The 7 cells are soldered together and wrapped in heat-shrink plastic wrap with the two wires sticking out of the end. Sanyo is generally considered to be the best. Leave the experimenting to the experts and stick with Sanyo.

8 cell packs are recommended by some fliers but some chargers will not charge these in fast charge mode and they are also a bit heavier to carry around the sky, leading to a faster sink rate. I find 7 cells a good compromise and this is the most popular, particularly for the beginner. Because 7 cells was found to be a good base standard, they are popular and there are competitions for 7 cell gliders

How many MAH? Battery capacity is measured in milli-amp hours (MAH). A 1,000 MAH battery will in theory give 1,000 milli-amps, ie 1 amp, for one hour, or 2 amps for 30 minutes or 20 amps for 3 minutes.

The initial voltage of the newly charged battery is higher in the first 20% or so of its discharge. This is handy because it gets you away from the ground faster and the first climb is generally the longest.

A 1700 pack does not usually provide 1.7 times the flight time of a 1000 MAH pack. The reason for this is the 1700 pack (at 410 grams) is 100 grams heavier which means there is a greater weight to lift in the climb and a faster sink rate (and speedier landings). This is more pronounced in a 6 foot (1800mm) plane than one which is a little bigger.

Battery technology is improving, with Sanyo's new CP cells, which are smaller and lighter. My old 1700 SCR pack weighed 409 grams, my new 1700 CP pack weighs 330 grams and a 1300 CP pack weighs about 80 grams less.

All this means a lighter weight to carry up and then around the sky - which leads to a docile plane and gentler landings.

Thus 1300CP cells are an excellent choice for the beginner, with a 1700 CP pack as your next purchase for a change.

How many packs? In your early days it is to your advantage to have a good break between flights. Tiredness combined with a lack of experience causes crashes. One may be sufficient for a start, later you may wish to move to two packs and perhaps ultimately three - one flying, one cooling (don't recharge a hot battery) and one recharging.

The power train - a good climb rate is essential. Firstly - when you crash, you generally crash into the ground(!!). The sooner you can get away from this dangerous geographical feature, the sooner you can relax and venture into various manoeuvres and the catching of thermals. Secondly, a shallow climb rate allows little margin for error. A couple of degrees too steep and you will lose speed and your glider will fall from the sky. A couple of degrees too shallow and you will not be climbing at all, simply moving around the lower regions expending valuable battery power, leading to a short flight. The lack of a decent climb rate is the major disappointment of most electric gliders that I see.

Power train - Gear Boxes vs Direct Drive. Electric motors are designed to rev at a high speed. However most motors will not have the power to turn at that speed with a propeller on the front. Many gliders appear at the field with a direct drive propeller and give a very disappointing performance with both a low climb angle and a short motor run.

Like your car, the motor needs to be geared down to combine optimum motor speed with most efficient propeller speed. A well matched motor, propeller and gearbox will give a greater thrust for the same power draw on your battery as a direct drive unit. This provides steeper climbs (with more margin for error in your climb rates) and a quicker escape from the dangerous area near the ground. With more or higher climbs you get much longer flights.

From my experience, direct drive is the most common mistake and its initial cheapness is false economy. Go straight to the gearbox with the matching bigger propeller.

(The partial exception to this for some planes is some particularly efficient cobalt motors, but most experienced fliers stick with the gearbox.).

Motors. Strange as it may seem, your basic cheap 540 motor often does quite well when combined with a quality gearbox and propeller. You can start out with a "hotter" motor which will increase your flying parameters but this is not essential as you can always upgrade later when you can manage the faster speeds.

Folding Propellers. A fixed (non-folding) propeller will continue to whiz around after the motor has been turned off, causing drag on the model. More importantly, it will hit the ground and may be damaged or cause damage to shaft, gearbox or mountings. It is possible to have an undercarriage to protect it but that is more drag and weight. A folding propeller assembly generally consists of blades, an aluminium centre piece and a spinner. The spinner helps keep the dirt out of everything, apart from making the plane look better. These items may be sold separately or together. Ensure they all match or you will have some alterations (or re-purchasing) to do.

This goes with this... - matching propeller, gearbox and motor. Propellers are measured in both length and pitch. A 13 x 7 propeller is 13 inches long and when turned one revolution it should in theory pull the plane forward 7 inches. (In fact it actually pulls much of the air backwards, at less than 100% efficiency, against the drag of the plane.) The trick is to match the size and pitch of the propeller with the gearing and motor to meet the weight, drag and climb requirements of the particular plane and also have a reasonable run with the battery. Too much of one without compensation in another will lead to the motor and propeller not working at best efficiency and insufficient climb rate and/or too much power draw. To add to the confusion, the beginner needs an appropriate climb rate or the plane will react too viciously to the controls. This generally means a biggish propeller around 12-14 inches, giving plenty of thrust but not too much speed.

It's quite similar to the gearing requirements of your car - enough thrust (torque) to get you moving without stalling, enough speed to get you into the traffic stream without being jerky and the right balance to match the power of your engine, the weight of your car and the preferred fuel economy. Unlike your plane, in your car you can change gear as you go along.

Fortunately you do not need to know all the gearing requirements of your car to drive. Nor do you have to in your plane, provided you have bought a reasonable match.

I need to add a further item in the equation, being weight. Including all gear, you glider should weigh no more that 1.4 kilograms. The less the better - some builders can bring this down as low as 1 kilogram, which makes for a very docile machine and possibilities of a good power to weight ratio.

A 6 feet to 2 metre glider around 1.3 kilograms should go well with a 3:1 gearbox with a 12 x 8 or 13.5 x 7 propeller. On my Electra I had a 3:1 gearbox with a 12 x 8 prop but after I became a better flier I wasn't happy with the climb rate so with a couple of shifting spanners I twisted the aluminium centre piece a little to increase the pitch. I have since been told this is dangerous and so cannot recommend it.

I then moved to a 2.5:1 gearbox with a 13.5 x 7 prop on a 2.25 metre glider weighing 1.4 kilograms with a Speed 600 motor (being slightly more powerful than a 540). I later upgraded to a "hotter" 23 turn double wind buggy motor, supposedly giving 50% more thrust with 1.6 times the static power draw. This made climbing quicker and steeper and gave me greater parameters for my climbing angle. But by then I could manage the higher speed under power.

The 2.5:1 seemed like a good idea at the time, but this ratio of gearbox limited what I could do to further enhance the performance.

I recently moved to a 3.8:1 gearbox, and a 14x8 prop. Using a 23 turn double wind motor I draw 20 amps, get a 30 degree climb and 25 minute flights. With a 16 turn double wind hot buggy motor I get vertical climbs. Plane weighs 1250-1300 grams and span is now 2.15 metres. Battery is 1700 CP. I then changed to a 15 x 8 prop, which gave no appreciable difference in current draw, but an improved climb rate to 35% or more.

I would recommend a 3.8:1 gearbox because it gives you the torque to turn a big prop, allows the motor to turn at a more efficient speed and can accommodate hotter motors that you may subsequently purchase.

Speed Controller or Off/On switch - Soft Starts and Motor Brake. A Speed controller provides a variable amount of power to your motor as a result of you moving the throttle stick on your transmitter. An on/off switch simply turns your motor on or off when you move the throttle, there is no middle ground. On/off switches sometimes have a "soft start" function so that the motor is not given a sudden burst of current which could damage things. The "soft" starting is almost instantaneous but soft enough to protect the equipment. A speed controller does not need a "soft" function as essentially this is built in by your use of the control stick.

Although most gliders are flown with either power fully on or power fully off, the speed controller (controlled by your throttle stick) allows more flexibility and can also be used later in aerobatic models which require control over speed. As they are only a few dollars more than the on/off switch and are safer they are worth the expense.

It is important that the controller or switch has sufficient capacity to handle the load for your current motor and model and very highly desirable that it can carry the additional load of any subsequent motor or model upgrade. A 40 - 50 amp unit will set you back about $100-$150 and (personal opinion again) I would not want to go much lower in capacity than that. The heavier duty unit will also provide you with greater protection against accidental overloading.

It is recommended that the controller / switch has a "brake" which briefly shorts out the motor terminals when the power is stopped so as to encourage the propeller to stop spinning and to fold back along the fuselage.

BEC (Battery Eliminator Circuit) This is a facility in your speed controller or on/off switch. It allows you to use the power from the main battery to also power your receiver, this saving the weight and expense (and possibility of battery failure) of a separate receiver battery. On most units the power will be completely cut off from the motor after the voltage drops below a certain level, leaving sufficient power for your receiver and servos for a reasonable flight.

There are two schools of thought, those that swear by BEC and those that swear about them. Some pilots feel there are problems with interference but from my experience, provided you have appropriate capacitors installed across your motor (see below) and your motor and controller are at least 6 inches from your receiver and aerial, BEC should not be a problem. I fly with BEC and my opinion is that there is a greater danger from the running down of a separate receiver battery and flying a heavier plane has disadvantages of its own.

It is important that your controller/switch has a definite BEC cut-off. I recently learned of a unit which allows the motor to completely drain the battery, so that the pilot is obliged to throttle off when a reduction in motor power is noted. The drop in power is not easy to detect 300 feet into the air and has the potential to leave you without any control whatsoever. This seems like a recipe for disaster sooner or later so avoid these.

 Connectors. The battery is connected to the speed controller using connectors, ie plugs and sockets. Tamiya plugs are often sold with kits, batteries and charging equipment and may be used for lighter load requirements. I flew my Electra on them without problems however the consensus amongst the flying fraternity seems to be that these are not solid enough to carry the required current loads of a hotter motor or more demanding power train so when I moved up I changed over to the 2 pin Deans Plugs which are readily available and highly recommended. You may choose to go straight for the Deans. Get the 2 pin plugs, not the 4 pin which are designed for lighter loads.

Solder the female plug onto the battery and ensure that your positive and negative are appropriately wired up. You will note the pins are laid up in a "T" so that it is not possible to plug them in backwards. The top of the "T" is positive. It is important that you are consistent with other fliers on this or any sharing of equipment may lead to expensive damage.

Using ordinary automotive spade lugs is dangerous as you will risk blowing your controller if the polarity is reversed and they are hard to undo for recharging. Obviously you will need a male plug on your charger to plug into the battery. The speed controller will require a male connector for "battery in".

If you solder a female Deans plug to the controller's output and a male plug on the back of the motor, your speed controller becomes easily removable and there is no risk of spinning your motor backwards.

A Fuse is important to protect your speed controller/switch from overloading. Some controller/switch units have a thermal cut-out which will supposedly protect the unit from overload, but I am happier to risk a $1.50 fuse than a $150 speed controller or my motor. I have blown a few fuses in my time, due to crashes and accidents in handling the plane on the ground. A simple 20 - 30 amp "spade" type fuse is easy to attach using spade connectors. Ensure that the connectors are soldered to the wires and are insulated, preferably with heat-shrink tubing. Make sure the fuse is accessible so that if it is blown you can get to it through a hatch and do not have to cut into the fuselage and remember to carry spares.

Note that if you are drawing much more than 25 amps you will have to live without the fuse, because you have too much power loss at higher amperage and also the thing will keep blowing.

If you are running your receiver on your power battery, it is deadly important that your fuse be between your controller/switch and your motor, not between your battery and controller/switch. Get this wrong and your blown fuse will cut power to your receiver, leaving you in the air without control.

Capacitors must be installed across the motor to stop interference with the radio equipment. These are essential to stop the electrical "noise" from your running motor upsetting the reception of your receiver. You will need 3 capacitors, one goes from the positive motor terminal to the metal outer of the motor, one from the negative terminal to the metal outer and the third from the positive terminal to the negative terminal. Capacitors of 0.1 micro-farad, available cheaply from Dick Smith Electronics, are appropriate for the job. They have "104k" printed on them.

Use thin heat shrink on the wires to avoid short circuits, My first crash was attributed to the lack of capacitors. To further reduce the risk of interference, speed controllers and motor wires must be at least 6 inches from receiver and aerial.

Can I convert my two channel glider into electric flight? In theory you can but you will generally need to do a lot of renovating including shifting your servos back and moving bulkheads to enable you to get your battery in. The whole front will require a rebuild to carry your motor and have a safe home for your speed controller and you'll have to be careful to get the balance correct. For all the work that is required (and even more so if you are a beginner), buying a new kit that has been designed for the job seems a better alternative.

If you do enjoy building and a bit of a challenge, you might think of building just a new fuselage and tail, copying the dimensions from your existing glider and allowing for the extra requirements and balancing of a powered glider. You can use your current wing if it is the right size and has reasonable strength. Most wings from gliders are built reasonably strong to cope with a bungee launch. Save your existing fuselage for when your motor glider is out of action, for the slope or you just feel like getting back to unpowered gliding.

The large propeller that is required for a geared motor does not lend itself to mounting on a pod on top of the plane and the extra drag does no good either.

Can I fly electric with a 2 channel radio? You must have control of your elevator and rudder and will also wish to have control over your motor so 2 channel has limitations. The first alternative is to run with a BEC (see above) so that your battery will take you into the sky and when it cuts out you can glide from there. This gives you one climb only, so you better get plenty of height for a decent length flight, but not so much height that you lose the plane. In view of what you are trying to achieve, this is too much of a compromise.

The second alternative is a toggle switch triggered by your down elevator. This allows you to climb, give a flick of full down to turn the motor off, and then glide. When you want to climb again, give another flick of full down then up you go. The problem with all this is that it relies on some good mechanical linkages and some good flying techniques to ensure you don't lose control of you plane when you give it full down. On no account attach the switch to your full up elevator or you when saving your plane from a crash you may turn on your motor and lead yourself into more trouble. You will still need a BEC switch. (Hitec make a model suitable but you may have to arrange for your model shop it to order it in for you.)

I started with two channel and my first day of flying was with a BEC only. I quickly realised this was not working and built a switch attached to down elevator. I managed but some of my crashes might not have happened (or have been less damaging) if I had throttle control, so it was false economy and I really should have gone for the four or more channel unit, as I have since done.

What Radio? For throttle control you will need a radio with 3 or more channels. 3 channel radios are rare, so it is generally 4 or more. If there are only a few dollars in difference between the computer and non computer radio, go with the computer radio as you won't regret it.

Talk to other fliers about their successes and failures in radios then check out the hobby shops when you know what questions to ask. Unless you have access to lots of money, a 4 or 5 channel radio is very satisfactory and to buy bigger may be excessive until you know what direction you will head. If you do decide to buy bigger (over $500), I would recommend moving up to something that includes plenty of model memories.

Transmitter settings - control stick functions. Be consistent with other fliers so that an experienced pilot can help you with your flying and your plane. Elevator on left stick, pull stick back towards you to give up elevator and away from you for down. Left and right is on the right stick. Throttle is also on the right stick, with no throttle back towards you and full throttle being with the stick away from you.

Your battery must be removable or you will have to continually hang around the field waiting for a re-charge while everyone else is busily putting their bungee launched gliders into the air.

If you can, avoid having to remove the wing to get at your battery because having to remove the wing can be a pain. This will require you to have a hatch in the underside of the plane or an opening which allows you to slide the battery in from above and in front to under the wing. Make a triangular "ejection ramp" out of very firm foam for your battery so that on a heavy landing/crash the battery will eject and have somewhere to go other than into your electronic components.

Motor offset - pointing 10⁰ down and 2⁰ right reduces changed flying characteristics when motor is turned on.

Wings with joiners vs wings permanently joined. This will depend in your transport and storage arrangements. A single wing can be stronger and lighter but may be more prone to "hanger rash", ie damage at home or in transport. This is therefore a matter of personal preference.

I like a flat centre section with removable outer panels.

Attaching the wings - Wings that are rubber banded on (6 number 64 bands) are easily removable and in the event of a cartwheel or a heavy landing you might only damage a couple of rubber bands instead of wings and fuselage. Too many bands will not have enough "give" and a crash will pull the dowels through the fuselage or damage the wings. A bolted on wing can easily damage both wing and fuselage on an unfortunate landing. Leave these until you are a better flier.

I have seen the wing fall off an internal combustion plane because the pilot re-used last weekend's rubber bands. A LOT of damage for the sake of 12 cents!!!

Vee tail vs contemporary. The normal tail (elevator and rudder) is said to be the more stable, which is better for the beginner. (However I suspect they are less stable only because they are so often under-sized,)

I like a Vee tail because it is less prone to damage when landing. Vee tails require mechanical or onboard mixing, or a computer mixing function to provide elevator and rudder.

Ventilation/cooling is essential for your motor and speed controller and preferable for your battery. Vent cowls can be built from plastic spoons which have had the handles ground off.

• Change to lighter servos - I fly with 2 Naro servos weighing 9 grams each instead of the standard 45 gram units - a saving of 72 grams. (Use the 1.4 kilogram torque units, about $55 to $65 each.)
• Build a lighter plane
• Upgrade your motor, experiment with different gearing (I suggest a 3.8:1 with a big prop) and experiment with different propellers - but be careful not to overload your speed controller.
• Experiment with different capacity batteries - or go with the Sanyo CP cells which are lighter.

If you own a direct drive plane and fitting in a gearbox is difficult, go for an "in line" gearbox.

Safety First - This cannot be overstated. Think of the danger that a fast one and a half kilogram object with a rapidly spinning knife edged propeller could cause if out of control amongst innocent bystanders (or even guilty bystander for that matter).

Fly and land well away from people. ALWAYS turn off your receiver before your transmitter. Make the assumption that your motor may start at any time without warning and disconnect your power battery when you are on the ground. Fly only where authorised and, to ensure that you are fully insured, join a club.

Moving on to other electric planes - You may wish to move on to planes which are prettier, scale, more aerobatic or of a different size. Most components are reusable in your next plane, including electrics and radio. Obviously smaller and larger planes will require some changes to some of your equipment but by then you will have learned enough to ensure you buy what is suitable. There are even indoor models.