Winch launch speed versus height gain

As I have never winch launched I would like to know.
At which 'point" do you let the cable out and what would be the wind
speed to carry the extra load of the cable and still climb.
Would it be, wind speed = glider stall speed, plus safety margin,
plus some extra speed to carry the cable and cable drag, hence 55m/h
would be the wind speed for a 15 meter class glider. Could the wind
speed be less and still climb?
An other question.
In the early launch phase would the winch have to generate at least
the load that corresponds to the lifting force for a given speed of
that glider, plus the winding-in speed of the cable to sustained
flight?
If it is windy the take-up speed of the cable is less but the load is
it still the same is that assumption correct?
Udo


On Nov 6, 9:25 am, "Mike Schumann"
wrote:
At high enough wind speeds, the maximum altitude is actually achievable by
letting cable out, rather than winching it in.

Mike Schumann

"John Galloway" wrote in message

...





At the risk of stating the obvious, assuming that the
winch/cable angle at the top of the winch launch is
a constant, then the height gained by the top of the
launch is simply related to the length of cable left
unwound.

You can work out the effects of different wind speeds,
glider climb angles, cable pulling in speeds etc but,
in the end, the highest possible launch will always
result from a steep climb at a high glider airspeed
but with a low cable speed. That scenario requires
a significant headwind and a winch that is capable
of pulling with sufficiently powerful, but also controllable,
torque at the required, lowish, cable speed.

John Galloway

"Udo" wrote in message
ups.com...
As I have never winch launched I would like to know.
At which 'point" do you let the cable out and what would be the wind
speed to carry the extra load of the cable and still climb.
Would it be, wind speed = glider stall speed, plus safety margin,
plus some extra speed to carry the cable and cable drag, hence 55m/h
would be the wind speed for a 15 meter class glider. Could the wind
speed be less and still climb?
An other question.
In the early launch phase would the winch have to generate at least
the load that corresponds to the lifting force for a given speed of
that glider, plus the winding-in speed of the cable to sustained
flight?
If it is windy the take-up speed of the cable is less but the load is
it still the same is that assumption correct?
Udo

It could work like this. Obviously, the wind has to be very strong aloft
for it to work.

The pilot is mid-launch on a very windy day and he's on the radio yelling
for less speed from the winch. The winch driver slows down the drum but the
pilot keeps asking for less speed - it seems there is a strong wind layer
aloft.

Eventually, as the winch driver keeps slowing the drum it comes to a
complete stop yet the pilot is still asking for less speed. The winch
driver shrugs, puts the winch in reverse and starts paying out cable. The
pilot hangs on to the cable since he sees he is still climbing. This can
continue until the winch runs out of cable - which, hopefully, is well
attached to the drum.

The trick is for the winch driver to maintain a constant tension on the
cable and for the pilot not to release just because he has reached the usual
release height. In fact, if the winch computer controls the cable tension
automatically, the winch may reverse without driver intervention.

Bill Daniels