Wow, my question generated some great responses, thanks everyone.
I wish I could have contributed, but I was suddenly invited out sailing, so I took that option instead
In any case, between all your answers I certainly understand better what's happening now. I also happened to stumble across another reference to "Performance Sailing" so I've ordered a copy for my amusement.
mortyd - I fully agree with what your saying. No amout of theory alone will make me a better sailer, for that I need to spend time in a boat. Nevertheless, I find the theory interesting and having a better understanding of the physics of what's happening can't do me any harm. It's the engineer in me.