Eric,

Point of interest: did you let the spin fully develop after the
coordinated turning stall? There is an aerodynamic tipping point --
that is the self-righting tendency of the tail that would typically
favor a spiral over a spin assuming that the only deflected control
surface was the elevator. Of course a wing drops when in a turning
stall, but without aileron deflection generating drag my guess would
be that designed yaw stability would prevent spin development.

There is a significant difference in the assymetric drag profile with
and without aileron deflection. Remember that most modern aircraft
begin their stall at the root. That means less torque and less
disposition to overpower yaw stability and enter a spin. Slapping an
aileron down to pick up the low wing adds significat drag at the tip.
Add some rudder (cross-controls), and now you have a greater
disposition to get the aircraft spinning rather than spiralling.

I'll give this a try over the weekend -- that is, making no recovery
to a coordinated turning stall to see how it develops. My Ventus spins
happily if aggrevated. It should prove a good test bed.

Eric Greenwell wrote in message ...
Ian Forbes wrote:

On Thu, 06 Nov 2003 00:02:30 +0000, Colin wrote:


- Spins occur when you stall and the glider is not "co-ordinated" ie
either slipping or skidding.

I used to think this, but I soon discovered our club Blanik would
happily spin from a coordinated turn by using a shallow bank and simply
reducing the airspeed. Since then, I've done this with other gliders.

A coordinated turn doesn't prevent the inner wing from flying at a
higher angle of attack than the outer wing, which is why it stalls
first, and a spin can begin. I haven't experimented with it enough to be
certain, but I suspect a slipping turn would reduce the tendency for the
inner wing to stall first.