On Jul 12, 6:30*pm, Don Johnstone wrote:
At 23:01 12 July 2009, bildan wrote:



In fact, tension control is relatively new technology based on vastly
increased knowledge of winch launch dynamics. *It certainly has the
potential to increase safety in those cases where unexpected weather
or a human winch operator creates unexpected conditions.

In fact it has the potential to be the most dangerous suggestion ever
encountered in glider winching.
Why is it that for years winches have been developed and used in the UK
and Europe with no real problems and all of a sudden someone *comes up
with probably the most moronic suggestion ever and that is that if the
tension on the cable is increased the winch slows down to compensate.
So I leave the ground and the glider starts to rotate to the climb,
increasing the tension on the cable so it slows down. Brilliant, it takes
a real towering intellect to think that one through. I suppose the
explanation will be that there is some clever electronic gizzmo to
compensate. The problem with high technology systems is they do not tend
to be robust and they require regular maintainace to ensure their correct
operation, (MVG Winch is a perfect example, most of the advanced features
don't work) whereas a well trained winch driver can do the necessary
compensation using good old fashioned judgement far more safely.
I would far rather place my trust in a basic winch with a well trained
driver that rely on dubious untried engineering solutions driven by the
unknowing.
Skylaunch, Tost, Supercat and MVG winches perform very well with very few
problems. Skylaunch, or Skylaunch re-engined winches are probably now the
most popular winch in use in the UK. We like them and the many years of
experience that has gone into them.

PS We do not have deserts in the UK, and we don't cancel comps just
because 2 or 3 people don't get away either.

Don, you have so utterly misunderstood the concept, it's difficult to
start a reply.

A tension controlled winch maintains tension, the pilot controls
speed. He does that in exactly the same way as in free flight - nose
up to slow, nose down to speed up. No matter what he does, the
tension remains at the same high percentage of the weak link
strength. The pilot cannot change the tension, only the speed. The
tension cannot exceed the weak link strength.

It's exactly like an airplane. Rope tension is the equivalent of
thrust. The winch provides the power and the pilot flies the glider.
The beauty is that no mater the turbulence wind layers or thermals,
airspeed remains under the pilots total control.

With an airplane on takeoff, even a powerful one, if you raise the
nose, the airspeed will decrease. If you lower the nose, the airspeed
will increase. It's how it works - hundreds of thousands of times a
day. A tension controlled winch does exactly the same thing.
Airplane pilots understand the concept instantly.