Wow, thank god it happened at altitude!
Isn't it that virtually all our rudder pedals mechanism are spring loaded,
and if one cable breaks the result is instantaneously full rudder? I always
thought this is a receipt for disaster. A glider without rudder control may
still be flyable and even landable, but not with full rudder!

Ramy

Some powered aircraft have interconnected controls with springs in the
control circuits. Tailwheel birds with steerable tailwheels have springs
connecting the rudder and tailwheel. A broken cable on those aircraft
can result in a rudder hard over. My homebuilt taildragger has a fixed
tailwheel for that reason (and enough rudder to drag that wheel sideways
when needed)

I think most gliders do not have springs in the rudder control circuit.
I can't remember ever flying a glider with a spring-centered rudder.
However, don't we all fly with just a little pressure on both rudder
pedals? A cable break is going to result in the rudder hard over on the
unbroken side. That is going to result in a rapid yaw and air loads that
will tend to hold the rudder hard over with no way to get it back. I can
see that putting the ship over on it's back pretty quickly. Snap rolls
anyone?