Ok, maybe a big block of salt :-)

In practice, my takeoff performance check is: If I'm not flying by X
distance down the runway, pull the release and land straight ahead.

Toad

On Apr 13, 8:56 am, Gary Nuttall
wrote:
And keep a note of how much fuel the tug has on board.
How heavy the glider pilot is. How clean the glider
wings are. What time of day it was. Outside Air Temperature,
pressure and moisture content. Local CAPE and Lifted
Index. Length of rope (and its elasticity). Power
setting of tug. What mood each of the pilots were
in. Stick position on ground run. Local thermal and
wave activity. All can have an effect on take-off
distance and climb rate.

There's so many variables that I'd be dubious of any
metrics developed beyond the fact that high altitude,
high temperature and heavy gliders do not make a good
combination.

Anybody who comes up with a set of explicit numbers
and sticks to them is likely to discover how often
theory doesn't work in practice!

Happy soaring
Gary Nuttall