I did some spin training with Bill Kershner in his Aerobat many moons ago. The guy WAS an aerodynamics wiz and had tons of obscure trivia tucked away. He'd throw all that out during the brief and then just grin ear to ear as he demonstrated a 15 turn "fully developed" spin with an 8500+ fpm descent rate. Good times. He passed on a few years back and is missed.

Oops, sorry for the thread drift - back to lost comm procedures.