On Jul 20, 8:15*am, Don Johnstone wrote:
At 11:50 20 July 2009, brian whatcott wrote:

Don Johnstone wrote:
... *a "tension controlled" winch is about the craziest idea I have
ever
heard, not least because, thankfully, it would never work.

Why not?

Brian W

Because there is no direct relationship between the tension experienced at
the winch and that experienced at the glider release using wire rope.
Even with plastic rope the relationship is tenuous at best, the rope does
have some mass and in addition has an elastic quality as well. The
tensions experienced at each end of the cable can be vastly different and
are different more often than they are equal, so measuring at the winch
end tells you very little about what is happening at the glider, it may
indicate what has happened but even this is not likely to be very
accurate.

Lets see, you pull on a rope but the force is "vastly different" at
each end? I can hear millions of teenage science students laughing at
that.

The weight of steel cable does have an effect but not it's
elasticity. Plasma rope has neither a lot of weight nor elasticity.
The tension at the winch and glider are the same to several
significant digits.