A better question might be, "which is better, a slight slip or a
slight skid?" Since we try to hold the yaw string at 0 degrees in
wings level flight, holding it at 5 to 10 degrees shouldn't be any
more difficult. As others have alluded, there are safety advantages to
holding slip rather than skid in a turn, therefore, it seems
worthwhile to at least make an effort to keep the nose a little
slipped for the sake of the airflow over the wings.

As for the angle of the yaw string, first, there is no one angle. It
will change directly proportionally to increasing bank and inversely
with increasing speed. The position of the yaw string relative to the
cg is significantly different for different models. And as you have
noted, individuals' abilities to distinguish small angles varies. This
is why I suggested a broad range of 5 to 10 degrees, rather than a
single case optimization. 5 degrees is about 2 minutes sweep of the
minute hand of a clock; 10 degrees is not quite 4. These are
discernable and useful.

"JS" wrote in message ...
Measured with a cad-program, for a turn radius of 30 m, the thread angle
should be 3.6 degrees, if the distance of the thread from cg is 2 m. Tighter
turn, wider angle. How precisely you can keep your thread in a 3-4 degree
angle?

js

"Chris OCallaghan" wrote in message
om...
Jim,

There was a thread on this subject a year or two ago, you might want
to search the archives.

The simple aerodynamic answer goes like this: The circle is traced by
the glider's center of gravity, which means that your nose extends
beyond the edge of the circle. To visualize, draw a circle, then draw
a line tangent to it. You can see that the nose and tail of your
fuselage transcribe larger circles. A yaw string forward of the cg
will show a slight slip for a coordinated turn (that is, coordinated
at the cg, or wing). If your yaw string is straight, then you are, in
fact, slightly skidding the turn. This effect also exists at the tail,
requiring you to hold a little bit of rudder into the turn (but not so
much that you straighten out the yaw string). Obviously, the longer
the arm, the greater the effect.

I've tried to observe the difference between the front and rear yaw
strings on a G103, but the canopy edge generates too much turbulence
to mark any clear difference.

For practical purposes, the slip is small (5 to 10 degrees).