On Thu, 10 Jun 2021 07:40:01 -0700, AS wrote:

What are your
prevailing winds on that field? How many days a year would you really
launch to the north? All these things would have to be analyzed before
making the decision to go for a winch.

Good points. I'd add a couple more, from the way my club normally
operates.

1) the rule of thumb says that generally launch height is 1/3 the
distance between launch start point and where the winch is placed on our
main run (04/22 with 22 being the prevailing wind direction).
We normally place out winch (a Skylaunch with a truck's V8 running on LPG)
4000 ft from the winch) and typically launch to 1400-1600 ft regardless
of wind speed, though we can hit 2800ft in a strongish wind with a good
speed gradient.

2) despite having a wide grass main run (475ft wide) we typically place
the launch point 500 ft from the downwind boundary so landing gliders can
stop before or just after they reach the launch point. Yes, this adds to
the required runway length, but it makes the launch rate a lot faster
since theres no wait while the landed glider is moved back out of the
danger zone for failed launches.

3) Our other run (16/320, 2800 ft x 300ft) is shorter and narrower with
no landing area behind the launch point. The result is a very low launch
rate because almost every landing stops well past the launch point, so
launching stops while a golf buggy gets the glider and puts it on the
back of the launch queue. Launches on it seldom exceed 900 ft.

HTH


--
Martin | martin at
Gregorie | gregorie dot org