At 21:55 13 March 2009, The Real Doctor wrote:
How much extra lift do you think is required to climb?

Without going into the math (euphemism for I'm not sure how to!).

If you are in a free 60 knot glide sinking at 1.5 knots and you want to
climb at 4 knots you have to increase the angle of attack ie pitch up to a
more nose high position to achieve that.

That of course causes a corresponding increase in drag and the glider
starts to slow down immediately.

On tow the tug produces the necessary force to keep the glider flying at
the same speed while climbing but for a given IAS (ignoring any position
error) surely the angle of attack and thus the stall speed must be higher
than in free flight.