On 8/06/2012 00:37, Bill D wrote:
If you're only getting 33% of the rope length, yours is a low
performance winch operation. If you optimize it, 45% or so is
achievable in no-wind conditions. A 10 knot wind can boost that over
50%. Again, I'm saying this is for gliders with better than 30:1 and
rope tensions equal to the weight of the glider. Below 30:1, achieved
height falls off a lot.

I didn't say it was "my" operation and I don't mind your 'low
performance' putdown, Bill. I've been involved in eight different winch
operations and my judgment overall is, like Chris said - 400m from
1200m, about 1:3 is a normal nil to light wind figure. I've read
previous posts on this from you. I think your 45% minimum is optimistic
and you do winching no favours making those promises.

1. The vast majority of winch operations are hand to mouth. Old
winches launching old gliders. Most of us can't afford professional
winches costing the price of 2 Pawnees. Most winches (outside Europe)
are medium- to low-powered. About 1:3 is what they'll get. An aerotow
operation converting to a winch probably won't be a prosperous, thriving
club setting out buy a $100,000 Skylaunch.

2. The vast majority (ALL, in my experience) of winch operations are
optimistic in their claimed launch heights. "He's not a very
experienced driver". "There must be a tailwind at height". "This is
not our best launching direction". "The engine is due to be serviced".
"The wire's a bit shorter than we usually have". I've heard them all
- including (just now) "...if you optimize it...".

I believe YOUR operation will routinely achieve a little better than 1:3
but will rarely exceed 2:5.

GC