At 20:23 31 December 2010, bildan wrote:
On Dec 31, 1:06=A0pm, Todd wrote:
I too agree with the real or perceived tow handling characteristics.

Looking at things =A0from and aerodynamics standpoint (and I am about
as
far from and aerodynamicist as you can get) it should seem that part
of the empirical data would suggest an experiment where you fly a
glider equipped with and Angel of Attack meter at your typical tow
speeds and record the AoA at various speeds. =A0Then fly that glider
on
tow at those same speeds and record the results.

Done that - and as nearly as I can see, there's no difference in AoA.

I've flown some pretty heavy high performance gliders behind some
pretty bad tow pilots - one of them stalled the tug with me on tow.
If I'm careful not to over-control the ailerons, there's no problem at
all.

Heavily ballasted gliders respond sluggishly in roll just due to the
extra roll inertia. A pilot trying to hold a precise position behind
a tug needs and expects crisp aileron response. When he doesn't get
it, he increases the amount and frequency of aileron with a
corresponding increase in adverse yaw. If he's less than equally
crisp with rudder to oppose the adverse yaw, it gets wobbly.


Where did you mount the AoA meter?

It's not the angle of attack that's the problem, but the change in local
incidence along the wing. The overall lift may not change by very much
when near to the tug wake, but its distribution along the wing does, with
increased lift at the tips and reduced lift at the root - putting the
aileron region close to the stall and hence reducing control
effectiveness.

I agree that increased roll inertia due to ballast is a factor, but since
the same factor applies to maintaining bank angle in a thermalling turn I
don't see how it can account for a significant difference in handling
between tow and thermalling?