"Bob Johnson" wrote in message
...
Hi Bill:

You have flown our winch and must have felt me ease back on the throttle
to keep you from exceeding 55 kt. I'll readily concede to you and
Andreas that our winch at 6000 ft or hitched to a 2000 lb glider is not
going to perform as well as it does at Odessa's 3000 ft pulling the
Blanik.

Absolutely. Your winch has far more power than needed for the L-13 at
Odessa. Craig is one of the few winch builders in the USA that put enough
power in his winch. It'll be interesting to hear your comments about
launches on a 100+ degree day with no wind.

There's an issue that I don't have a good understanding of which is why you
and I keep fiddling with these power formulas. I think it's the density
altitude effects. DA has a very pronounced negative effect on power output
of a normally-aspirated engine combined with the need to accelerate the
glider to a higher speed. These two effects combine to really sap the
energy from a winch launch.

I find an unexpected power shortage to be quite alarming. I'd like the
power margin to be large so that under the worst imaginable conditions there
is still a considerable power reserve. Just because the power is there,
doesn't mean you have to use it.

Bill Daniels