Thanks Bill, that document is very interesting.

There is one thing in particular I am unsure about however - how much
up elevator I should be putting in. With the K8, I fly the launch at
50-55kts with the stick fully back for perhaps the last 30% of the
launch after smoothly transitioning from full forwards on the ground
run through neutral once in the full climb, until I feel the glider
being pulled level, when I relax the aft pressure in anticipation of
putting the nose down to reuce cable tension prior to releasing. (This
later movement often results in quite an increase in speed, which I
convert to height after releasing. Is this an indication I'm releasing
back pressure too early, or the winch driver not backing off the
throttle enough?)

With a K21, which winch drivers here (which includes me) are told to
give "full power all the way up" from our Oldsmobile V8. Climb speed is
at lesst 65kts and I'm reluctant to pull back too hard. Why? A K21
launches on a black weak link (1,000kg). I imagine full up elevator in
a K21 would produce enough lift to break that at well below max winch
speed, 81kts.

Is there a way to calculate how much lifting force full up elevator
should produce for any given airspeed? Or should I not be putting full
up in? If not, just how far should I bring the stick back, and when?


Bill Daniels wrote:

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.