"Eric Greenwell" wrote in message
news:AFg1h.4183$WB4.3314@trndny04...
Bill Daniels wrote:
Good show!

Dyneema/Spectra winch cable allows for launches to approximately 50% of
the original cable length. Calculations show that there is really no
upper limit to the amount of Dyneema that can be used.

90 seconds to 5200 feet AGL on a winch beats the hell out of 20 minutes
on aero tow. That's especially true when the typical cost is $10 for the
launch.

That sounds a bit frightening - 3500 fpm! What are the stresses on the
glider to get that kind of climb rate? How far away is disaster if the
pilot twitches a bit on the controls or hits some wind shear or a thermal?

--
Eric Greenwell - Washington State, USA

There is a lot about modern winches and operating proceedures that will seem
counter-intuitive to US pilots trained in aero tow.so it's easy to
mis-interpret the danger signs. You can be assured that the Europeans are
at least as concerned about safety as we are and that they have carefully
worked out how to do this safely.

The glider manufacturer has carefully specified a weak link accurate to plus
or minus 5% that is the ultimate protection for the glider airframe. In
addition, modern winches are constant tension with computer controlls that
prevents the winch from applying enough force to break the weak link. The
tension is set at about 70% of the weak link strength for the main part of
the climb.

For the pilot it's just like a takeoff in a powerful airplane. Just pitch
up for desired climb airspeed. If the airspeed is high, just raise the nose
a bit more and the airspeed will decrease. If it's a bit low, lower the
nose a bit and the airspeed will increase.

If the glider hits a thermal or gust, the winch senses increasing tension
and cuts power just enough to maintain the selected tension. This pretty
much guarantees a perfect launch every time.

Make no mistake, this is a LOT of fun.

Bill Daniels