I don't think it's quite as simple as that. You need a lot of torque and
power to accelerate the glider up to flying speed,

Lets see, you have an engine from a 7000 pound road vehicle and you
are accelerating a 1,500 pound glider without even the possibility of
wheel spin and you claim you need "at lot of torque"? That doesn't
even pass a smell test.

1st and 2nd gears can/will develop so much torque at the drum you'll
break the weak link or worse. Simple arithmetic shows the GM big
block will develop 3000 pounds or more of rope tension in 3rd gear.
1st and 2nd gears are just a nuisance requiring the winch operator to
gently advance the throttle to avoid trouble.

That's just one of MANY issues related to using automotive components
in a glider winch.


then a slight reduction
to allow for the safety climb and rotation and then lots of torque and
power again for the full climb. As the glider nears the top of the launch,
the climb flattens out and you need less power and torque. The cable speed
reaches a maximum as the glider starts the rotation and then drops quite a
lot as the glider enters the full climb, due to the water-skier effect, and
then continues to drop thoughout the rest of the launch.

The water-skier effect means in effect that the vertical speed is being
added to the horizontal speed, so that the maximum winch launching
airspeed would be vastly exceeeded if the cable speed is not reduced in
some way. BTW, the water-skier effect is used by water skiers themselves,
only in the horizontal axis, to gain speed for jumps and other tricks
while the ski boat continues on at a constant speed.

Oddly enough, the Skylaunch throttle stop system and automatic gearbox
seems to automatically compensate for all the above effects, except *that
you have to back the throttle off near the top of the launch to avoid
overspeeding the glider.

Derek Copeland *