Adding ballast

[Christopher Mayers]

Could anyone shed some light on the reason that ballast would be added to a model glider.

I have a 2m electric glider (built up) and just got back into the hobby but have previously flowe rc planes not gliders.

Does ballast increase speed or control in wind?

Edited By Christopher Mayers on 17/12/2012 21:14:18

[Tom Satinet]

Yes it helps on windy days, but it is a bit more complicated than that. It is to do with lift to drag ratios and such. Ballast makes a glider flying on the same glide path, if you like, faster than if the same glider was lighter. I.e it can achieve it's best lift to drag ratio at a higher speed. Good glider flying is not about minimum sink rate only, it is about moving from lift to lift and moving out of sink. Ballast helps you move about the sky from one bit of lift to another. one windy days you notice the benefit a lot for obvious reasons.

Search google for ballast in gliders and you will throw up some stuff. E.g. Proper experts can put it in better words than I could.

http://www.5c1.net/Glider%20Performance%20Airspeeds.htm

That's all great and everything, but if you flying an electric glider from the flat field you need to be careful as the power train might not be able to lift the extra weight. Say if you have a 1kg glider that only has a reasonable climb rate, adding about 300g could make the climb rate really bad.

Also yes ballast can make the model easier to fly in bumpy conditions, although it somewhat depends on the location of the ballast and the nature of the model. If it is all around the centre line (i..e fuselage ballast tube), it doesn't always help smooth out the wings too much if they are very light (e.g on a built up glider).

[Martyn Johnston]

I remember many, many moons ago, when I was first learning to fly a Zagi in high winds, it was blowing about like a paper bag. Another flyer nearby, with a lot more experience than me, came over and helped me tape a lump of lead right on the CoG. The difference was amazing, it was much more stable, much faster, and had much better penetration through the wind.

I remember thinking that the weight ought to go right at the front (to push the nose down !) but he correctly told me to keep the CoG where it was, and he was right.

[Erfolg]

With the advent of electric gliders,ballasting is no longer as popular for non competitive flying.

As Tom has stated, it is all about increasing flying speed, by maintaining the same AoA, which has previously been determined as the best distance set up. This will not be the longest duration AoA.

Now with power, if down wind, the motor is just switched on, coming back, with an inefficient angle of attack, which would have you sinking to the ground without the power. Probably landing out without that power.

Competition pilots still ballast though, even when practising, as this ensures that they can wring out the most from their models, in the time in air. plus they can move about, especially down wind, without using the motor.

[Erfolg]

I should have mentioned that all the modern gliders I now see, can change the airfoil by reflexing the TE. Which seems to be more used than increasing camber. Most good pilots are confident that they can climb in a thermal without needing to increase the L/D ratio.

Movement, is what modern pilots want, and can use.

Plus, the use of crow braking makes hitting the spot, far more certain than the previous braking methods,