sails always worked as sails work. the thinking about them has changed, but
airfoils are airfoils, and have been since birds learned to fly a bit back.

Thanks a lot for the illuminating answers. I read somewhere that the
"sail-as-airfoil" trick is a rather recent one, and that formerly
people would just let the wind push them around. Is that true, and if
yes, how recent is the invention?

Thanks,
Axel