On Thu, 21 Jul 2016 08:06:34 +0000, Peter Higgs wrote:

End of rope is anchored to the ground. Rope goes around pulley on the
launch car, then back to the glider. Car travels half the speed of the
glide r (2:1 system). The only rope moving relative to the ground during
the launch is the rope between the pulley and the glider. And similar to
a winch =
launch, all that rope becomes airborne pretty quickly.

There may be a snag to that....

The amount of rope between the glider and the car is shortening all the
time, and the pilot is alive at the start of the tow ?

That looks similar to the winch situation to me: in both cases the
effective rope gets shorter during the launch.

- with a winch you get roughly 1/3 the height of the rope length
in calm conditions, so 2/3 of the cable has been wound in at
release, and a lot more if there's wind to help the glider kite
while the winch slows down.

- on a 2:1 factor auto tow the height:rope length ratio must depend
on where the anchor peg is along the runway. If its at the launch
point the height gain will be poor, but if its half-way down the
run, the worst case would be launching to 1/2 the height of the
rope length and, like the winch, a lot higher with wind to help.

The main disadvantages compared with a two drum winch is that the launch
rate will be lower (cable must be retrieved after every launch vs after
every two launches) and each retrieve will be slower because the tow car
needs to:

- detach from the cable
- find the end
- tow that back to the launch point
- go back up the field and put the cable back on his pulley

compared with:

- drive the cable truck to the winch (or follow the first launch down)
- hook both cables on
- drive back to the launch point

Did I miss anything?


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |