Winching - Reverse Auto Tow

On Tuesday, July 19, 2016 at 10:22:07 AM UTC-5, wrote:

I'm not sure I see much advantage of a 2:1 system (assuming you mean the reverse-driving vehicle has a pulley as well). Wouldn't you still be dragging 4,000 ft of rope behind the tow vehicle (from the fixed pulley)? It hardly seems worth the extra rigging trouble...but I've never done it either. My primary concern is rope wear, and I'm not seeing much improvement with that. Please let me know what I am missing.

Stephen

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 glider (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.

Steve Leonard

On Tuesday, July 19, 2016 at 10:25:55 AM UTC-6, Steve Leonard wrote:
On Tuesday, July 19, 2016 at 10:22:07 AM UTC-5, wrote:

I'm not sure I see much advantage of a 2:1 system (assuming you mean the reverse-driving vehicle has a pulley as well). Wouldn't you still be dragging 4,000 ft of rope behind the tow vehicle (from the fixed pulley)? It hardly seems worth the extra rigging trouble...but I've never done it either.. My primary concern is rope wear, and I'm not seeing much improvement with that. Please let me know what I am missing.

Stephen

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 glider (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.

Steve Leonard

Thanks Steve. I was thinking about the rope being fixed at the end of the runway opposite the glider, going around a pulley on the tow vehicle, then back to a pulley next to the fixed end (again...opposite the glider). I was thinking that the only advantage was mechanical (1/2 speed). Now it's clear to me.

On Tuesday, July 19, 2016 at 10:25:55 AM UTC-6, Steve Leonard wrote:
On Tuesday, July 19, 2016 at 10:22:07 AM UTC-5, wrote:

I'm not sure I see much advantage of a 2:1 system (assuming you mean the reverse-driving vehicle has a pulley as well). Wouldn't you still be dragging 4,000 ft of rope behind the tow vehicle (from the fixed pulley)? It hardly seems worth the extra rigging trouble...but I've never done it either.. My primary concern is rope wear, and I'm not seeing much improvement with that. Please let me know what I am missing.

Stephen

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 glider (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.

Steve Leonard

That will probably give the most rope life for UHMWPE or dacron ropes.

http://linearcomposites.net/media/pa...e_study_13.pdf
Used 500m lengths of this for autotow and got 1500ft launches with L-13 and G-103. Doesn't like pulleys I'm told. Another poster said they had frequent breaks. Wasn't my experience. Rather heavy.

Frank Whiteley

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 ?

On Thursday, July 21, 2016 at 8:15:08 PM UTC+12, 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 ?

Exactly the same as with a winch, you mean?

Except in this case the winch is moving.

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 |

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.

That is quite true, except with the winch you have the full runway length
of rope between winch and glider.
With the Car, you can only start with half that distance from car to
glider.

On Thursday, July 21, 2016 at 6:30:04 AM UTC-4, Peter Higgs wrote:
That is quite true, except with the winch you have the full runway length
of rope between winch and glider.
With the Car, you can only start with half that distance from car to
glider.

If OP is at Hobbs, there's no lack of space.
With a payout winch, its possible to drive around the corners
of the huge triangular airfield and keep climbing.
Don't know if anybody that does so with a glider, but I did that
with a hang-glider back when Curt Graham had a hang-glider
operation at Hobbs (kinda weird flying around the corner
on a ground launch).

Payout winch keeps line almost always off the ground,
uses more of available space - anybody doing glider (sailplane)
payout launches these days???

On Thursday, July 21, 2016 at 5:31:35 AM UTC-6, Dave Nadler wrote:
On Thursday, July 21, 2016 at 6:30:04 AM UTC-4, Peter Higgs wrote:
That is quite true, except with the winch you have the full runway length
of rope between winch and glider.
With the Car, you can only start with half that distance from car to
glider.

If OP is at Hobbs, there's no lack of space.
With a payout winch, its possible to drive around the corners
of the huge triangular airfield and keep climbing.
Don't know if anybody that does so with a glider, but I did that
with a hang-glider back when Curt Graham had a hang-glider
operation at Hobbs (kinda weird flying around the corner
on a ground launch).

Payout winch keeps line almost always off the ground,
uses more of available space - anybody doing glider (sailplane)
payout launches these days???

Gary Boggs has extensive experience with this. If his rig is still running strong, a visit to Hobbs may be in order.

On Thursday, July 21, 2016 at 5:31:35 AM UTC-6, Dave Nadler wrote:
On Thursday, July 21, 2016 at 6:30:04 AM UTC-4, Peter Higgs wrote:
That is quite true, except with the winch you have the full runway length
of rope between winch and glider.
With the Car, you can only start with half that distance from car to
glider.

If OP is at Hobbs, there's no lack of space.
With a payout winch, its possible to drive around the corners
of the huge triangular airfield and keep climbing.
Don't know if anybody that does so with a glider, but I did that
with a hang-glider back when Curt Graham had a hang-glider
operation at Hobbs (kinda weird flying around the corner
on a ground launch).

Payout winch keeps line almost always off the ground,
uses more of available space - anybody doing glider (sailplane)
payout launches these days???

Gary Boggs, NW Sky Sports, is the only one I'm aware doing this in recent years. He's now in Peoria, AZ. Not sure his rig made the trip from Oregon.