On Jul 12, 8:45*am, Don Johnstone wrote:
At 00:07 12 July 2009, bildan wrote:



If a glider encounters a thermal during a launch, the rope tension
will increase which the automatic transmission will see as a "hill"
causing it to increase torque to the drum. *This increases rope
tension still more as it tries to pull the glider down through the
thermal. *If the glider hits sink, the automatic transmission will
slack off the torque just when the glider needs more power. *A good
winch operator can overcome these to a degree with constant throttle
adjustments - if he can tell what is going on in the glider but it's
hard, skilled work. *It's definitely not "set and forget".

A tension controlled winch will do the opposite - decreasing power in
thermals letting lift do the work and increasing it in sink leaving
the pilot to control speed with pitch. *The pilot sees a very smooth
launch regardless of wind or thermals. *The winch operator doesn't
need to do anything at all.

It's wonderful to never need speed signals again.

I think the difference in design concept between Europe/ USA is that over
the years we have leaned to design things which work for a minimal cost.
We have tried to avoid the expensive solution designed to kill you. I can
think of nothing more dangerous in a winch design than a tension sensitive
drive.

It may be wonderful to not need signals again, which if you are dead of
course you don't need, we prefer the safe option over here even if it
means a little more work.

Check your geography. Tension controlled winches were developed in
Europe. Check your engineering facts. Tension controlled winches are
FAR safer than any other alternative.

How can a winch be safe when the operator must control glider airspeed
with throttle WHEN HE HAS NO KNOWLEDGE OF IT? Actually, Skylaunch
indirectly acknowledges this by offering airspeed telemetry as an
option.

The only reason for this loud controversy is a single English winch
manufacturer in who uses cheap American auto parts and sells the
product - essentially a 2-drum Gerhlein - for $145,000 USD at last
check. It's a great business model as long as there are suckers.
People tend to get upset when you point out the Emperor has no
clothes.

Yes I know it's a MARINE GM V8 but that's the same engine core as used
in a pick-up trucks with a few different accessories. Last check,
they wholesale for about $2,500. The stock GM TH400 sells for about
$1200 USD.