When I said straight I meant aligned with the runway axis, and with the
fuselage as well (in a slip).

"T o d d P a t t i s t" escribió en el
mensaje news
"J.A.M." wrote:

Ok... When the sailplane is under crosswind, it's velocity vector is
altered
and it's not folowing a straight course over ground.

If the crosswind is constant and the sailplane is flying
constant speed and heading, the ground track is straight.
The problem is that the straight ground track may not be
aligned with the runway. If it's not, you must turn to a
new heading.

To compensate for this
you change the direction of the lift vector sideways (rolling the wings
with
ailerons) while keeping the nose pointed where you want (opposite rudder,
a
slip).

Banking the wings and changing the lift vector produces a
side force in the direction you are banked. Pointing the
nose opposite the banked wings produces an opposing force
due to the angle of attack of the fuselage. These two
effect balance out and the track remains straight.

This changes the velocity vector of the glider,

The velocity vector changes only if the pilot delays the
opposite rudder enough to allow the uncompensated bank to
turn the glider, change the track and compensate for the
wind. If the pilot was initially crabbing sufficiently,
then he would not delay the opposite rudder and the glider
would not turn, the track would remain unchanged, and the
only difference would be the increased descent rate and the
fuselage would now be aligned with the runway.

making it follow a straight course over ground,

It's always straight, during crab and slip.

but a somewhat uncoordinated flight in the airmass (in a
slip, the velocity vector is not aligned with the fuselage; the glider
does
not flies straight).

Correct.

Wings level means... wings level... angle of bank zero, level with the
horizon, horizontal. I'm sorry I'm unable to explain better. The rudder
goes
where it needs to go to keep the string centered (coordinated)

Are you saying you land wings level in a crosswind, your
wheel is aligned with the runway AND your yaw string is
straight (coordinated flight)? It just isn't possible.

The glider is not skidding, it's just between a skid and a crab.

I have no idea what this is supposed to mean. If your yaw
string is straight, you are crabbed. If it's off to the
side, you are either slipping or skidding.

You seem to be confused about the exact issue that drives
this discussion.