Most new fliers, and those who transfer from gliders, think of additional grams of weight in terms of a percentage of the total weight of the plane. What I want to introduce you to is something different, which I call "Profit".

 In business – there is (a) EXPENDITURE and (b) INCOME. If your business expenditure equals your income then you are breaking even and making no profit. To make more profit you need to increase your income or decrease your expenditure. If your profit margin was normally 1% of income then achieving a 1% decrease in expenditure would mean a doubling in profit. Reduce expenditure by a further 1% and you have now tripled your profit from 1% to 3%!! If you also managed to increase income by 1% then you now have a profit of 4 times what you started with.

 In powered aircraft there is (a) WEIGHT and (b) the amount of POWER required to maintain LEVEL FLIGHT. If the amount of power that you have is only about 1% more than that required to maintain level flight then your flying is not going to be much more than puddling around at full throttle, trying to gain height.

 In fact you are probably already flying with several percentage points of profit but with a little effort you could make it more.

 So what will this extra profit do for you? It means your climbs can be steeper – or you can retain the same climb angle but do it faster – or at lower throttle. It means your sink rate will be less, meaning less motor required to regain lost height. You’ll have more battery power available for longer flights and/or simply hooning around the sky.

For a glider, thermals will have a greater effect because the rising air is more able to maintain or raise a lighter craft. Alternatively, you can install a heavier more powerful battery pack and/or a more efficient or powerful power train, if increased speed or climb rate is your aim.

As a rough rule of thumb, if your static thrust is 30% of the weight of your plane, you are probably have very very little of what I have described above as "profit". (Static thrust is the forward trust measured whilst the plane is being held still. It is not a true reading of the plane’s performance as the dynamics are different while the plane is stationary.)

I have a light ARF (Almost Ready to Fly) indoor model and, at the suggestion of a fellow Australian Electric Flight Association flier, I left off the rubber tyres and stickers to gain about 5 grams more "profit" and can now fly longer and have a greater speed range, ie I can fly both faster and slower.

Lighter equipment is usually more expensive and the dollar cost of those smaller lighter servos (weighing 5 to 9 grams instead of 45 grams for a standard sized servo) may at first may seem steep. But the change can make a considerable difference in profit margin and resultant enjoyment of the plane. Receivers also come in different weights. (Obviously both servos and receivers must meet the performance requirements of your application.)

On my Speed 400 model I am using a simple cheap push-on propeller which pushes straight onto the shaft, instead of a propeller adaptor and standard propeller, a saving of some 6 grams. This may not suit all models and it’s a bit noisy, but it happens to suit this one quite well.

Newbies may think that overengineering an aeroplane will mean that it last longer because it is less likely to be broken. This is not always the case, for the following reasons. Firstly, a heavy plane has plenty of mass to crush the bits that hit the ground first. A lighter plane will bounce. Think of dropping an egg, as against dropping just the eggshell, from a certain height. The momentum of the heavy egg will crush the shell to the extent that not even all the king’s men with litres of CA glue would bother trying to fix it. But if you just dropped the shell only, without its heavy contents, the damage would be far less.

Secondly, a light plane can be more reactive to the controls so you can pull out easier. Finally, a heavy plane will fall out of the sky if flown too slowly so it has to be landed faster. A lighter plane can land slower, meaning less speed on the final touch down and less that the brain has to take in.

 In addition, on launch the lighter plane will move away from that dangerous thing called "the ground" earlier, with fewer accidents as a result.

The above makes the assumption that you use common sense in your building – and that you are not going to build a craft that is so fragile that it is damaged at the slightest touch. Also be aware that a highly powered craft, or one that is to be subject to violent manoeuvres in flight, must be strong enough to withstand the stresses imposed. A pull-out after a steep dive is the worst, as is wing flutter.

If the plan calls for sheer webs (vertical strips of balsa between the upper and lower spars), don’t leave them out! Carbon fibre strips and rods can be used effectively in the right places and if you are using epoxy, grab a small container of microballoons – also called Q-Cells. They are in the form of an extremely light powder which you mix with your epoxy to bulk it up without adding any detectable weight or reducing the strength below what is required for most applications in a light plane. (About $10 for a container which will last a very long time.)

For some unpowered gliders the carrying of a little extra weight is fine to some extent as although the weight increases the sink, it also increases the penetration – the speed that it can go through the air – meaning not flying backwards in a stiff breeze, being able to penetrate the wind at the slope or make good headway from one thermal into the next. In fact for some gliders weight is mandatory. But for most hand launch gliders (HLG’s) and light floaters, the preference is to retain the lightness.

At this point I must add an important note. The above was written for those flying within the natural parameters that beginner and middle ground electric flying dictates. Those who fly internal combustion must remember that the higher power of these motors places extra strains on the airframes which brings them outside the scope of this article. In short – ask your local internal combustion experts and don’t take a risk.