On Mar 11, 11:07*am, Mike the Strike wrote:
Some gliders definitely will fly slower in free flight than on aero-
tow. *The Discus 2 is a good example of this. *I have run out of
elevator authority several times on tows slower than I'd like and
ended up slipping into low tow position or losing control altogether
and releasing.

I believe this is related to the angle of incidence of the wing, which
requires the Discus to adopt a high nose-up attitude at slow speeds.
Under aero-tow, the rope pulls the nose down, which requires extra
lift from the tailplane. *At slow tow speeds, the tailplane cannot
develop enough lift to maintain the proper angle of attack of the wing
because of this pull from the rope.

When dry, my Discus 2 stalls below 40 knots and will thermal happily
between 40 and 50. *I cannot safely aero-tow at 50 knots and usually
call for at least 65.

This effect is most notable with high performance standard class ships
whose angle of incidence is more optimized for high-speed flight.
Flapped ships by and large do not suffer from this problem, nor do
most training ships or lower performance single-seaters.

We are not imagining this!

Mike

If this is the case (and I think it is, combined with downwash
effects), then might low tow alleviate some of the low speed problems,
by changing the angle of the towrope at the glider end?

I agree that my LS6 sure feels "iffy" when the tow gets slow, even
though well above stall speed. I'll have to try to see if this effect
is as noticable at low tow next time I get a tow.

As far as vertical tows, I seem to remember they did a glider acro
routine at the NZ WGC that involved hanging a glider from it's nose
hook under a Hughes 500 in hover, then releasing for a tailslide to
start the routine. I recall the transition from normal tow to the
hover described as "interesting" in the glider (!!).

Kirk
66