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Old December 12th 06, 09:26 PM posted to rec.aviation.soaring
Bill Daniels
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Posts: 687
Default How to get maximum height on a winch launch?

If you join the Yahoo group "winchdesign" and look in the files section,
there are a series of truely excellent papers in the folder "Winch Dynamics
and Performance" by George Moore. (soargsm)

Essentially what George determened is that the major sensitivities a
1.Field length
2. Headwind
3. Cable tension as a percentage of glider flying weight.
4. Weight & drag of the cable

There is very little extra height to be gained by agressive technique beyond
just hitting your target airspeed and holding it there with smooth control
inputs. This gives an angle of attack just slightly greater than that for
best L/D. If you want help with this, put some AOA strings on the canopy
sides and calibrate them for L/D max and Vmin sink. Of course, it goes
without saying that you should never put yourself in danger by rotating into
the climb so quickly that a recovery from a rope break is impossible.
Smooth and accurate flying are what you want.

So, if you want to get higher, get a longer field with more wind, replace
steel with high strength Dyneema and get a winch that can accurately hold
tension at 80 - 90% of the weak link.

Bill Daniels

"Dan G" wrote in message
ups.com...
I'm interested in learning how to get the maximum possible height on a
winch launch, without compromising safety in any way.

This question has two parts really - how should the pilot fly the
launch (pretty much how should he operate the elevator during the
launch), how fast should the glider fly, and how should the winch
driver feed the power in? For the sake of argument, let's assume the
glider is a K13.

For reference, I fly from an airfield with a 3,300' long cable, and the
maximum height I achieve repeatedly is 1,700'. Headwind typically goes
from around 10kts at the ground to something like (I estimate) 20kts at
height.