Join Date: Jun 2006
Location: Hong Kong
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I read a piece about this a while ago that I think put the blame at the feet of coriolis forces and the different angles of attack that this creates with the wind hitting different heights on the sail.
Basically, assuming that you tune the sails to draw cleanly at the point of greatest belly in the sail - or between 1/3 and halfway up the sail, on one tack the slight difference in wind direction at the top of the sail will give you a beneficial increase in lift, whereas on the other tack it'll do the reverse - there's a diagram, but I don't remember just now where it is - does anyone else remember seeing or reading this?
I guess the effects are small, but with all else being equal, and particularly for a taller rig, perhaps it could create this 1/2 knot extra...?