bildan wrote:

- limited in height and distance, i.e. you can't tow to that thermal 10 miles away if there's none nearby

The practical reality is that you rarely actually know there is a
thermal 10 miles away. If there's lift around, you can find it with a
2000'AGL winch launch - if there's no lift around, why consider an
aero tow?

This depends on the location. At our site, we seldom can reach a thermal
from the winch, and even on those rare days not reliably. So as much as
we'd like to use it for cross country launches (heck, it *is* cheaper
and more fun!), winch launches are pretty much limited to student
instruction.

On the other hand, we often *do* know that there's that thermal 10 miles
away. First, because it is always there, and second, because of the
forming cumulus. But between our site and that thermal, there are 10
miles of sink. Agreed, on most days there eventually will grow thermals
near the airfield, but only at noon, when those pilots who did a aerotow
have already 2 hours under their belt and are 100 miles away. Agreed,
you can fill that gap with a sustainer, but then, you can as well
aerotow. Most airports weren't planned by glider pilots!