Eric, perhaps you know George Moore who lives in your area. He has written
an series of papers on the forces involved in winch launch. He would be
able to provide the exact answers.

Bill Daniels

"Eric Greenwell" wrote in message
news:GBu1h.4529$WB4.3254@trndny04...
Gerhard Wesp wrote:
That sounds a bit frightening - 3500 fpm! What are the stresses on the
glider to get that kind of climb rate? How far away is disaster if the
pilot twitches a bit on the controls or hits some wind shear or a
thermal?

Hmmm, if they are using weak links, I don't see a problem.

Stress (=force) is related to acceleration, not to speed. You can go
straight up at 1000000 fpm with the same force as at 10 fpm. Just takes
you a bit longer to reach the speed.

Of course, the net force on the glider is zero, otherwise it would
accelerate, but the individual forces are much greater and vary during the
launch. We've all seen the wings curve up and stay that way as the pilot
rotates into the climb on a winch launch, indicating much more lift is
being generated to counteract the pull of the cable.

Surely the cable tension must be greater to provide a 3500 fpm launch
instead of a 1000 fpm launch? I'm curious about the amount of tension
needed to provide a 1000 pound glider that 3500 fpm climb.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org