Balancing a Buggy

Is the rear end of your buggy braking / slipping out.?

The Problem

Is your tow point (effective center of pull from the kite your center of lateral resistance (CLR) so you have a yawning moment.
The CLR is approximately the same as your longitudinal CG – although there are 2 wheels at the back the downwind one always grips more than the upwind one on account of the overturning effect due to the tow point being above the ground, but usually the effect is insignificant and finding your CG can help but requires a bit of maths and some scales. This also assumes you have the same tyres all round
If you have a turf tyre on the front and slicks on the back, then your CLR will be a long way forward of your CG, it will be pretty close to the front wheel!
Also changing to turf tyres all round won’t actually cure the basic problem – it may well be that you get enough grip not to notice it, but it could still be slowing you down.

There are 2 ways to fix the rear end slide:

To move the CG/CLR you can either add weight to the back of the buggy, or shorten the downtube, or a combination
To move the tow point you need to move the seat, which might mean you also need to move the downtube.

If you understand moments calcs you can use some maths to work out roughly (usually quite close) where to position everything.
If you hate maths try moving one item at a time and see how it affects the slide.
I would suggest first move the seat forwards a bit – this will move your tow point and your CG. It often balances things up quite quickly.
You will probably need to move your downtube as well so try that next
To get the tow point forward, shorten the DT – this may mean you need to ride with your knees quite bent when going straight
If this is the case and you prefer to ride straight legs, look to add rear extenders at a future date so you move the back away from the tow point as well as the front, you want to lengthen the buggy keeping the ratio of front and rear distance to the tow point the same.
As a last resort add weight to the back of the buggy.

But I am the heaviest thing in the buggy

Yes, but moving you back also moves the tow point back, and trial and error has generally shown that moving the tow point around has more effect than moving the CG around probably because the rear tyres don’t give equal grip meaning the CLR is always a bit forward of the static CG.

So to summarise:

First try moving the seat forwards, then shorten the downtube. When you find a good balance sit in the buggy and get a friend to measure from your front axle to your harness tow point (or if you don’t use a harness it will be to your hand position when actually flying so try and look at how much you twist round and how far back your hands are due to the rotation) and the distance from your back axle to them same point. Keeping the ratio of these distances the same lengthen the DT until it is comfortable, and have a pair of extenders made for the back to get the right distance.

When working out if your back end is still a bit frisky

Don’t just go by feel, get onto a beam reach well powered (wind about 90 degrees to buggy), and try to hold a straight line, if you find you have to turn the front wheel towards the kite, the back end is a still a little loose, if you have to turn away, then you have gone a bit too far. If you can go straight and steer straight you will be perfectly in balance and when a gust hits you will go sideways in line not spin around. Most people don’t like to be perfectly balanced, but find that point first and then see which way you feel more comfortable – if the back is a little loose tacking is easier and some people like a slight tendency to turn upwind, also a lot of people like to make the rear break out when gybing, but clearly yours breaks too much at present!

Did I mention the balance point can change with different tyres or surfaces?

Beach balance and grass balance might be slightly different so be prepared to think about it again when you move onto sand
It will never be as much of an adjustment.

Jim aka Boater