First line of your reply is the wrong way round, the full power signal is
given and about 1-2 seconds stretching later the glider accelerates very
rapidly
and is airborne 1-2 fuse lengths, depending on which glider and winch
power setting has been used you have a very short initial climb phase
and have to rotate to full climb or you will overspeed ,the winch reduces
his
power setting as you rotate into the full climb arc.
We are not talking a huge effect here and your reference to your use of
nylon
as a launch rope ,if I am correct nylon has far more spring in it than poly.
Autotow we do here for fun every now and again and the acceleration is
slower
The other thing to remember is this club and other clubs have dialed up
many
thousands of launches on this poly rope and it has shown to be consistant
and predictable in the bungee effect
gary
"Bill Daniels" wrote in message
link.net...
How about this "bungee effect" scenario:

You accelerate the glider smartly and stretch the rope. The glider lifts
off normally but encounters a strong headwind layer at 100 feet AGL. The
pilot frantically signals for less speed and the winch driver promptly
reduces power, but the "bungee effect" just keeps pulling the glider
faster
until the stored energy is depleted. Then the glider airspeed sags as the
reduced winch engine power is felt. The pilot signals for more speed and
the winch engine throttle is again advanced, but the additional power is
absorbed in stretching the rope before the glider sees the additional
speed.
Then repeat cycle.

I once tried auto tow with 3000 feet of 5mm nylon and this is what I
encountered. We never did tame the launch so we went back to steel wire.
_______

This is a very bad way to control a launch unless the winch power is set
very low so the glider pilot controls airspeed with pitch attitude. I
don't
like the idea of winch rope that stretches any more than needed to damp
vibrations. I like the idea of instantaneous airspeed response to
throttle
changes. Spectra stretches less than 1% at the failure point. Spectra is
pretty much a "drop in" replacement for steel wire except that it is 90%
lighter.

It's much better to have reserve power from a large, high torque engine
and
a winch line with little stretch. My dream winch is a powerful one that
has
a telemetry link to the glider. The winch pulls the glider to the desired
airspeed at the maximum safe acceleration and holds it precisely there
while
the pilot pulls up to tension the rope to 80 - 90% of the weak-link
breaking
point. That is the definition of an optimized launch.

Bill Daniels