I have very little practical knowledge of winching and I
still do not understand what the theoretical factors are
that determine max launch height.

Neglecting wind speed and wind gradient for the moment, as
well as safety concerns relating to rope breaks down low,
what is the technique to max out height given the changing
climb and tow line angles and geometry?

Derek Piggot writes in his book "Ground Launches , 1996, pg
34.):

“The optimum speed on the launch depends to some extent on
the wind strength with a slightly higher speed giving the
best launch height in calm conditions. Best L/D speed is
close to the optimum, with the minimum cruising speed or
speed for minimum sink being the lowest safe speed.”
Derek Piggott, Ground Launches , 1996, pg 34.

If the speed for best L/D is close to optimum, what is optimum?

The American Soaring Handbook, Vol 3, Ground Launch, 1980,
pg 32 says the following about auto tow

“The factor which determines the towing speed of the
automobile is the indicated air speed (IAS) of the
sailplane. It has been shown that the launching forces on
the sailplane are at a minimum just below the IAS for
maximum L/D of the sailplane”

Just how far below the best L/D IAS is the point of minimum
stress on the airframe?

Once we have derived the factors to max out launch height,
how do you then balance efficiency versus climb rate after
that point in the launch when you have enough altitude for
a safe recovery from a low rope break?

Pete

--

Peter D. Brown
http://home.gci.net/~pdb/
http://groups.yahoo.com/group/akmtnsoaring/