Thermal Velocities

I have been test flying my new self-launching ultralight sailplane
design this fall, and it is going well. The Red Tail Hawk so far looks
like it has a glide ratio of around 21/1 at about 60 mph, which is at
the low end of the range of what was expected. But it has a minimum
sink of about 250 fpm at around 50 mph, which is worse than I had
hoped.

I have subscribed to XC Skies and have been watching the soaring
forecasts for tops of useable lift and thermal velocity for about a
month now, and seeing some 300 to 400' thermal velocities predicted
these fall days. That rate does not leave a lot left for climb at the
250 fpm sink rate of the Red Tail Hawk.

I'm in the central Illinois area. What I was wondering is what kind of
thermal velocities might I expect for next year during the prime part
of the soaring season. Is there some easy to read historical data
somewhere I could go thru? Or does anyone here have any anecdotal data
they could provide?

Thanks in advance,
Jerry Booker
http://groups.yahoo.com/group/RedTai...ightSailplane/