All you guys seem to really need to know is that a lower pressure is generated on the leeward side of the sail than that on the windward side and the sail is “trapped” in between. Nature, hating such types of imbalances use her (nature is a woman by the way) little invisible “fairies” to continuously “push (or pull which ever the case may be –maybe both?)” the sail towards the lower pressure until equalisation occurs. Thank you Mother Nature for bringing such joy into my life as “a tall ship, and a star to guide me by”.
(shouldn't we look at the effect that "black matter" or at least "black energy" has on the applications of these "theories"???)