Derek,

You may want to review some videos on my website. I am continuing
flight testing to determine the minimum slip angles and control inputs
to produce spin entries in several different ships. I expect, however,
that an open class glider would be especially subject to the condition
I've described.

http://ocglider.com/Grob_spin_avis.htm

I would prefer that you not share this link with the group. You may
distribute it to others who may backchannel you on this subject. That
will keep interest within my bandwidth limits.

Thanks

Chris O'Callaghan




Derek Copeland wrote:
There have been several incidents and accidents over
the last few years when gliders, especially big span
ones, have suddenly spun or spiral dived when entering
or manoevring in strong narrow thermals. I am therefore
wondering if pushing a wing down into a strong thermal
core could cause a momentary tip stall? Wing going
down plus air coming up could cause the stalling angle
of attack to be exceeded.

Derek Copeland