At 01:30 28 March 2005, Fred wrote:
Terry: That's the way I explained it too, (& BTW,
the phenomenon is
noticeable in the east too). There should be a more
elegant (or
simplistic) explanation, don't you think? One that
doesn't require
diagrams of lift vectors? Fred


If you're flying a child's kite in a steady breeze
and give a quick yank on the string, the kite goes
up.

A glider is designed to convert the vertical pull of
gravity into nearly horizontal motion. The uprush of
air (change in AoA) on entering a thermal has an effect
similar to a sudden increase in gravity (if that were
possible) pulling the glider downwards through the
air. The glider converts that to an increase in forward
motion.

You are, in effect, getting a brief winch launch every
time you enter a thermal.

Ed.