On 3/26/2021 5:13 PM, waremark wrote:
On Friday, 26 March 2021 at 16:25:39 UTC, ProfJ wrote:

It's kind of fun to have all the experts invalidate my actual lived
experience, and also physics. Let's go watch some videos of winch
launches, shall we?

Here's Bruno Vassel launching
https://www.youtube.com/watch?v=VrUT...el=BrunoVassel . Due
to the wonders of actual video evidence, we see the glider taking seven
seconds from first roll to airborne. Here's one from Oxford Gliding -
https://www.youtube.com/watch?v=-eTU...nel=GreatFlyer - nine
seconds from first movement to airborne. Here's one from Mount Beauty -
https://www.youtube.com/watch?v=SE5J...=GeorgeSkarbek -
five seconds to airborne. Here's one - called "Rather fast winch launch"
! - https://www.youtube.com/watch?v=-eTU...nel=GreatFlyer -
five seconds to airborne.

I didn't cherry-pick these, they were the first four I found where you
could see the glider roll. If anyone can find one showing a two-second
roll, go ahead and show us.

Yes, it seems like it's two seconds. That's the problem of sensory
overload. Apparently even the experience of 1500 launches on a variety of
airfields doesn't overcome it.

This one at my club shows the glider in the air after about 2 seconds:

https://www.youtube.com/watch?v=f_ASzIsviAE


Reality is what a person experiences; camera views aren't 100% representative
(cf: Hollywood).

A beady-eyed look at several of the Mt. Beauty launch views-from-afar show
multiple launches with ~2-sec ground rolls *after* the line slack is removed
and the ship is beyond wing-runner assistance...which by my reckoning is "when
the winch launch begins". Everything prior to that is preparation.

YMMV.

Bob W.