Jax,
Maybe I didn't word it clearly. I said "A boat goes to windward by
generating lift from its sail, just like an aircraft's wing. If you
understand a wing you are 3/4 of the way there."

I meant 3/4 of the way towards understanding how a boat goes to windward
- not 3/4 of understanding sail airfoils. The other 1/4 being to turn
it on its end and match it with a keel, centreboard etc.

But this isn't helping Axel very much. Do you know of any good online
diagrams we could point him at? I admit I can't be bothered to search
for one...

And.

JAXAshby wrote:

my statement was in respone to the secondary posting that said understanding
wing arifoils was 3/4 of understanding sail airfoils.