On Mar 7, 5:47*pm, Mike the Strike wrote:
On Mar 7, 2:14*pm, Eric Greenwell wrote:





On 3/7/2011 7:24 AM, Mike the Strike wrote:

We have discussed this many times before. *The nose-up attitude of the
glider results in extra forces that have to be overcome by the wings
and tail surfaces. *In particular, modern standard-class ships with a
low angle of incidence of the wing have a pronounced nose-up attitude
that results in loss of control at speeds well above free-flight stall
speed.

I'm having trouble picturing the influence of a low angle of incidence
of the wing (I assume that's compared to the fuselage) on loss of
control. Why would the wing be affected by the fuselage attitude being a
few degrees higher, relative to the air, than on an older glider?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

The angle of incidence of the wing (relative to the fuselage) is a lot
lower on modern standard class ships. *The result is that they have a
pronounced nose-up attitude when flying slowly - you can see this both
on tow and when thermalling. *On aero-tow, a nose-mounted tow hook
will result in a downward force on the nose that has to be compensated
by an upward force from the tailplane and extra lift from the wings.
The point at which you lose control under these dynamics is at a lot
higher speed than the free-flight stall speed. *The effect doesn't
seem to be as strong with older gliders or flapped ships, but
definitely is a lot less in low tow.

Mike- Hide quoted text -

- Show quoted text -

I suspect you intended to say the tail was generating more down force
to over come the down vector on the nose.
Simple math based on a guess at tow rope tension of, say 50 lb or so
( 1000 lb glider/40 to 1 and double for sake of discussion), would
lead me to guess the down force on the nose to be not more than a few
lb.(maybe 10?). Assume a tail moment arm of 3 times the nose arm and
the extra lift the wing needs to generate is maybe 15 lb. at the most.
Your observation that the glider flies better in low tow makes sense
in that you are in cleaner air.
FWIW on a rainy winter night.
UH