On Jan 6, 9:50*pm, Doug Greenwell wrote:
A winch launch is very different because (a) the angle between the cable
and the direction of motion of the glider is large, and therefore unlike a
tow the downwards component of the cable tension is no longer negligible,
and (b) the motion is not steady. *

In this case the lift is greater than the weight because it is partially
counteracting the cable tension and weight. *The precise balance depends
on pilot and winch driver technique. *Even so, it is still the forward
component of the cable tension force that is doing the work required to
raise the glider to its release height. *

It's pretty easy to show that in the early part of full climb on a
winch launch when the cable is horizontal and neglecting cable weight:

tension in the cable = glider weight * tan(climb angle)

lift required from the wings = glider weight / cos(climb angle)

The latter is identical to the lift required in a turn with the same
bank angle as the winch launch climb angle.

Thus at 45 degrees the tension is the same as the weight and the lift
is 1.4
At 60 degrees the tension is 1.73 times the weight and the lift is
twice.

When using a tension-controlled winch, what tensions are actually
used?