Bill Daniels wrote:

Many pilots who have tried the "pitch strings" report that they give advance
warning when entering an area of lift. When you enter the edge of a
thermal, the strings show a sharp increase in AOA several seconds before the
vario shows lift. This improves the efficiency of "dolphin flying" by
providing an earlier signal of when to start a zoom. One pilot on a
marginal final glide told me, "Without them, I wouldn't have made it home."
An ASI gives the same signal but it's weaker and harder to interpret.

And yet, I never see any gliders with "pitch strings" on them, not even
on contest winners' gliders, presumably the pilots most interested in
getting the most from their efforts. If it's effective, why hasn't
something so cheap and easy spread throughout the fleet?

I did try these on a Std. Cirrus 30 years ago, and eventually concluded
they didn't help in any way. Maybe it's time to repeat the experiment,
but I'm skeptical about the string's value.

--
Eric Greenwell - Washington State, USA
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* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org