On Tuesday, November 12, 2013 9:47:33 AM UTC-6, Geoff Brown wrote:
Having gone through all the posts on this thread, I'm amazed that no-one
has stated the obvious. the difference in handling between flying at 40
knots on tow and flying at 40 knots off tow.



In the first case you are trying to get the glider to climb so you have a
high angle of attack so you can follow the tow plane. The wings are
pulling more than 1g, you just can't fell it in the cockpit. In the second
you are descending, and you might even be pulling less than 1g.

Or did someone mention it and I missed it?

Alas, this is not true. On tow, you are pulling exactly 1 g and flying at exactly the same angle of attack. If anything, in fact, the slight upward pull of the towrope means a slightly lower lift from the wings. Imagine if it were pulling you straight up -- zero angle of attack, zero lift on the wings.

You are flying in an upward trajectory. The wings have a slightly higher angle relative to the horizon, but not relative to the oncoming air.

The discomfort may be because the nose is pointed higher. But since the glider is going up, this higher nose angle does not mean higher angle of attack.

Similarly, an earlier poster suggested releasing from tow and maintaining pitch attitude relative to horizon. This will not work, as now the air is coming at you in a descending direction. In fact, a major fault of many students after a rope break is NOT promptly lowering the pitch attitude so they can maintain the SAME angle of attack and airspeed.

I think we're down to the downwash effect.

The one time you need temporarily more angle of attack is if the towplane climbs suddenly. I think this is why it's particularly annoying to be close to the ground and the towplane takes off, then climbs abruptly while losing speed while the glider is still basically on the ground.

John Cochrane