(Mark James Boyd) wrote in message news:412a9f4a$1@darkstar...
Ted Wagner wrote:
yaw string straight.

We've had this discussion on RAS before. I'm still
gonna say that yaw string straight doesn't prevent a spin
entry. Spins are when you're stalled and one wing is more
stalled than the other.

One wing is more stalled than the other if one wing
has less AOA/more airspeed than the other. With the yawstring
straight, this is still true in a steep bank, especially
with long wings. It's also true if you're in a slip and
then with a punchy foot coarsely correct it to
center.

The steeper the bank, the higher the stall speed AND
the greater the difference in wing speeds, even with a straight
yaw string.

When I teach rope breaks, I do them at 300 ft and 30-45
degrees of bank, and best L/D for that bank angle.
http://www.stolaf.edu/people/hansonr/soaring/spd2fly/
is a start. I also caution against super rapid roll rates
and coarse use of rudder.

I'm open to thoughts on this. I didn't do the math to
see how MUCH the factor affects spins (somebody else did and
came up with 3 degrees diff or so for 50 deg and 18m wings),
but it sure surprised me.

Now when I do spins in the L-13, I do them from string centered
flight, and sure enough it always spins in the direction of the
steep bank, and in a hurry too...

P.S. Of course this assumes the rigging is right. If
flaps are lower on one side than the other, hey man, there's
yet another factor...


I disagree with your conclusion about steep bank angles. It is
usually a lot harder to spin from a steep turn, and a lot easier to
recover from an incipient spin, for a simple reason (see Piggott for
more details): a properly flown steep turn is flown at a
significantly higher speed, and the elevator is limited, making it
harder to reach stalling angle of attack, and much easier to reduce
the angle of attack if needed due to the higher speed.

You mention in an earlier post about making shallow, fast turns during
a low save. Why shallow? If the thermal is narrow, you usually need
to be steep (and fast) to stay in the (probably a bit turbulent) core.
A shallow turn is asking for the classic base-to-final spin entry,
unless you fly so fast that any climb is more luck than skill!

Methinks your power background is showing (all those shallow turns!).
Even though I also have a power past going way back, I now find my
glider bias showing when I fly a stinkpot; I find myself whipping into
nice 45 to 60 degree banks, scaring the daylights out of my power-only
friends...

Kirk