Author: Webby
The use of glide bar has significantly improved the performance characteristics of our wings and bar is now an important component of our glider equipment. The R&D invested in it’s design and effect on our wings represents some 20% of the total value of our glider.
Another way to express this is that if you paid $5,000 for your wing and are not using the glide bar correctly then you are probably wasting $1,000.
When not to use the glide bar
The glide bar should not be used when using it constitutes an unacceptable risk, when it is dangerousUnacceptable risks include:
- Crashing into the ground
- Losing control of the wing
- Colliding with other pilots
How does using the glide bar increase risk?
The application of the glide bar generally flattens the camber of the wing and decreases it’s angle of attack (AoA). Our wings are already set with a relatively low AoA so any further decrease means that we are more likely to experience some form of tuck, a direct consequence of a negative AoA.A tuck represents an increased risk of losing directional control and height. If you are close to terrain then you need a very compelling reason before deciding to use glide bar.
Avoid using the bar when close to terrain
Thermals, rotor and terrain induced turbulence are some examples of disorganised air with varying directional flows. These varying air flows can add to a low AoA when using bar, resulting in some form of tuck.
Avoid using the bar when in disorganised or unpredictable air flows
The added focus required to actively use glide bar can distract us from our customary responsibilities of piloting and observation.
Avoid using the glide bar when close to other pilots
How to use the glide bar
Setup
The bar needs to be set up so that after launching you can find and rest your foot on it without causing it to extend, this is the lower limit of it's range of extension. You also need to be able to fully extend the bar so that the glide bar pulleys on the riser are pulled together giving the upper limit of extension, “pulley to pulley”. These two limits represent the full potential range of the bar. We can further divide the range of extension to approximately ⅓rd and ⅔rds extension.Some bars require multiple steps to allow us easier access to that full range. It is well worth practicing with each step to get an idea of how much bar is in play when using one step or two. Using the bar, particularly with one foot, can easily lead to uneven application of the bar and riser which can be difficult to observe. Check the risers and distance of the pulleys from each other as a quick visual guide to see how evenly you are applying bar across the two risers.
You should regularly check the glide bar line through the multiple pulleys within the harness and on the risers for wear. In time you will begin to use the glide bar more and a broken glide bar line mid flight is a frustrating distraction.
Application
Do not use the glide bar tactically when it increases your risk unacceptably. Losing control of the wing may be dangerous and is inefficient. Provided that the risk of using the glide bar is acceptable then let's consider when to use it tactically.The most complete answer here means coming to terms with the polar curve relevant for your wing; an interesting and illuminating exercise.
In summary the more glide bar you use then the greater your airspeed but also the greater your sink rate. The combination of these two values defines when and how much bar to use. Gliders are getting progressively flatter polars which means you can use the glide bar sometimes to maximum, without losing too much performance by increasing your sink rate.
Tactically many pilots know to use the glide bar in head wind and think they should use it a little in sink. Reality is that sink is the prime case for using glide bar then followed by headwind.
When you run the figures the polar curve graph shows this very clearly. The rules of thumb here are:
- When in sink of 2m/s then use ⅓rd bar
- With more sink then use up to ⅔rd bar
- Sink and head wind, then use as much bar as you can manage up to maximum
- In headwind only use a little bar up to ⅓rd, unless the headwind is strong.
Our gliders are getting faster, bar increases that speed further which increases parasitic drag; think thin, reduce harness and pilot profile.
- Apply and release the bar smoothly, not jerkily or quickly unless necessary
- Try to maintain a steady, constant bar pressure
- Apply pitch adjustments via the bar rather than brakes where safe
With experience you will begin to appreciate pressure feedback from the bar similar to what you can already sense through the brakes and the harness. Develop and appreciate this feedback as it is the atmosphere talking to you and will lead you towards being able to use the bar more in variable conditions.
Summary
Provided it is safe from a risk management perspective then:- In sink, then bar aggressively
- In headwind, use bar but more conservatively
- In both sink and headwind, bar as much as you can
Consider using the bar whenever you are not climbing or searching for lift.
On glide routinely ask yourself what speed should you be flying and adjust your bar position accordingly