Performance loss versus yaw string deflection

bumper wrote:
"Eric Greenwell" wrote in message
...
I don't recall ever seeing an estimate of the performance loss in a glider
as a function of yaw string deflection. Does anyone know what it is?

Ultimately, I'm wondering how much attention should be paid to deflections
of, say, 1/8", 1/4", 1/2", etc., on the usual 4"-5" long yaw string.

I suppose a professionally manufactured and tested yaw string, like the Mk
IV, comes with a performance correction card (much like compass has), but
I just have a blemished one I got an outlet store - no card.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly


Eric,

I take this yaw string business seriously, though admittedly making MKIV's
is a whole different thing than being able to fly with them straight. No
card is provided with the MKIV, as we have no control over which side of the
equator the MKIV is to be used. And, as I'm sure you are aware, coriolis
effect can wreck havoc upon yaw strings if they are not properly degaussed.

Without glider specific flight testing, we may still assume that in straight
flight and with the yaw string straight back, we have unity or 100%.
With the yaw string 90 degrees off to the side or anything forward of that,
we have a problem, or for our purposes, 0%.

By extrapolation . . . Ummm, what was the original question?

bumper
proudly churning out MKIV and QV's for the unwashed masses.

I've just read on aviationblather.com the FAA is cooking up a new NPRM
to require all MKIV yaw string installations to display a 2" square
placard within 6" of the yaw string. The placard supposedly shows a yaw
string at right angles to the canopy, with a red circle/slash over it.
Not only would this raise the cost of the MKIV, but it would reduce the
pilot's view of the sky and increase the chance of collisions. Another
example of bureaucratic meddling!

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org