At 16:35 31 December 2010, sisu1a wrote:

Sure, even more with flaps equipped ships! But yaw control seems to be
more affected than roll. Can we explain that?
Just a little faster please is what doctor ordered here...usually 5
mph more is enough to a more pleasant tow.

I'm going to assume your flying with a nosehook, in which case the big
tether is resisting motion in the yaw axis... whereas for roll the
towrope runs directly down the longitudinal axis, leaving airspeed/AoA
as the dominant external forces affecting roll.


good point - a nose hook would tend to improve yaw and pitch stability on
tow, but have little effect on roll, so it's difficult to split out the
effects of aerodynamics and tow cable dynamics. I did some work years ago
on towed bodies (aerial targets and sonar fish) and the coupling effects
between cable and body motion get really complicated.

The rope also holds the glider at unnatural attitudes for given
airspeeds, which I think contributes a lot to the lack of perceived
(less than usual for that particular airspeed) aileron authority,
contributing greatly to making the glider feel horrible on tow,
despite being well within it's stall speed.

yes - I'm sure there must be a pyschological element as well


Not as an endorsement for or against this arrangement but from an
aerodynamic prospective rather, a CG hook leaves the yaw axis pretty
free to swivel accordingly and likely reduces the rope induced AoA
affecting aileron authority as well *once in a steady climb. (*not to
be confused with the up pitching tendency these hooks are famous for
during the initial acceleration of a launch...)

-Paul


I think the rope effects on stability with a nose hook are generally
favourable - its the aerodynamic effects of the tug wake that cause the
problems