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Weight Shift and Centering in Thermals

by Jorg Fedler (updated 5. December 2010)

Pilot weight shifting

Introduction

Before paragliders saw the dawn of light, weight shift was a topic which where mainly a hang gliding "thing". Until the delta (hang glider) was the only aircraft that was supremely controlled by weight shift.
Very soon paraglider pilots experienced the great advantage of weight shift. And today nearly every experienced paraglider pilot controls his/hers canopy not only with breaks but applies weight shift in all kind of flying maneuvers.

Ok, The aerodynamics of Paragliders are mainly ruled with the left and right brakes. However if we apply weight shift, the climb can be improved, especially if we are cruising in "zeros".

Cross braces and chest belt

Cross braces on your harness do make weight shift nearly impossible and you have to do without them if you want to control your glider using weight shift. Simple adjustable braces are much more versatile.
After you've wrestled on your harness, make sure that your braces are fairly loose so they won't interfere with your body movements. The chest belt from your harness should also be in a fairly loose position. This enables you to shift your body freely to either side.

Different gliders behave differently

If your body weight is shifted to the left side the lifting conditions on your wing are altered in such a manner, that the canopy is starting to turn to the left. Not all gliders respond to weight shift in the same way: some models are very sensitive, others behave quite stubborn, trying to fly straight. If you have one of those “bulls” stay calm and think about an exchange.



Deformed Canopy

The advantage of weight shift

Idealistically you should fly at a minimum sink rate while climbing in thermals, which does mean you pull the brakes down 10 to 15%.

Because the outer wing encounters a faster airflow when turning, we apply much less or no brake on that side. With most canopies pulling 15% brake it is not always possible to achieve the necessary turn radius in thermals. Therefore we are forced to pull the brake even further.... On the other hand if we use our body weight to supplement the turn, we have a much better chance to core cleanly and keep the relative turn-sink-rate to a minimum.

An important side effect

As mentioned before, to fly effectively with weight shift it is important to loosen your chest belt. By doing so you will reduce the amount of tucks and collapses in turbulent conditions. Before a collapse takes place there is nearly always an exoneration of the lines, that is, the lines are not tight. With a loose chest belt your body will fall uncontrollable towards the collapse side, putting pressure on the lines.
Flying with an „open” chest belt may feel a bit awkward at first but the tendency for collapses is distinctively reduced.

Be aware though that if it comes to a collapse while flying with a very loose chest belt, than you will be turning very fast into the direction of the collapsed side. Take your pick but be prepared.

When you've flown in the „loose chest belt setup” for a while you will feel comfortable at one stage and appreciate the maneuverability, especially in scratchy conditions. Your body will sense your gliders „life” more directly and you can respond much more controlled to your glider's feedback.



Exoneration

Application of weight shift - wing over

A wing over is a perfect learning experience for weight shift.
It's characteristic is to climb into a steep turn ending in a dive. It is an altitude-losing, spectacular maneuver and very popular.

How is it done?

Quickly pull one of the break handles to make a fast turn and assist the turn with weight shift. Before the turn ends apply opposite weight shift and reverse pressure on the brakes. If you do this repetitively you will dive left and right performing a figure eight.
Important: You may loose height rapidly.
Another type of wing over can be performed with a sharp application of both brakes followed by abrupt, complete release. As you dive you can begin initiating the turn, using your body weight to assist.

Remember

This maneuver requires perfect control and coordination on your part and you may reach the boundaries of what a paraglider can do according to its design and manufacture.
To practice this maneuver, start with small turns and increase the speed when you are familiar with the behavior of your paraglider.


Pilot weight shifting forward

How to center in thermals

When your vario is talking to you with a fast climb tone you may have ran into a thermal.
Now you will have to decide:
1. in which direction do I have to turn and
2. is the thermal strong enough for a circle. Normally you react instantly and decide to use the elevator by feeling it out with your body or hearing it out with your vario.

Your decision in which direction to turn makes all the difference between failure and success.
Quite often you may not hit the center of the thermal (but who claims to be perfect?).
When your are in a thermal, be aware that the side of your wing that is nearest to the center of the thermal is lifted. Shift your body to this side and initiate the turn and apply the brake on that side immediately after your weight shift. The aim is to keep the center of the thermal clean in the middle of the circle you fly. This process is called centering. When centering you have basically two choices:
1. if the climb rate increases - good pilots feel this with on bums - the circle has to be widened and
2. in a decreasing climb rate you circle nearer to the center of the thermal.
These continuous changes of your circle diameter can be achieved with supplementary weight shift to a great advantage.
It will enable you to optimize the brake position (lowest turn sink rate). During the climb you have to estimate continuously the thermal diameter and the change in climb rate to adapt your circle radius. If you have a strong and narrow thermal it is important that you increase the bank angle. Otherwise you will be thrown out and start all over again.

Weaker and wider thermals with low climb rate potential demand wider circles with the lowest relative turn sink rate. In this case weight shift is on top of the list. While thermalling, it is important to apply smooth actions, either with your body or brakes or both.
Hastily applied changes in weight shift and brake application will increase the chances of turbulence on your wing (interruption of the laminar airflow along your canopy). This will automatically decrease your chances for an optimized climb.
Note: Thermalling is the opposite from chopping timber! Just observe an eagle or pelican:
It will center anew in each circle he flies with smooth and controlled movements.
For us, this demands full concentration but over time and after lots of thermalling you will do all this automatically as your brain, your body and your glider grow together into a perfect flying machine.

Besides there is something else which demands our full attention, that is other pilots. So for your own and your fellow pilot's safety, don't get too absorbed in your training, watch the air traffic.

Jorg Fedler can be reached under jfe@bigpond.net.au or visit the web site http://www.clip1080.com



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