Theoretically, when reefed (and
only when reefed), the sail and mast combination presents an asymmetrically profiled foil to the wind. The starboard tack presents the best profile, due to the sail furling clockwise. On this tack, the spar forms a leading edge with a contiguous flow along the low pressure side - the windward side of the sail.
On port tack however, the semi-furled spar interrupts the flow along that crucial low pressure side, creating turbulence and non-laminar flow. Contrary to what may seem logical, a sail is actually 'pulled', not 'pushed', by the low pressure gradient to windward.
This is why some high-performance sailing craft, eg the Farrier 31R trimaran, use a teardrop shaped mast that can be manually swiveled to windward, thus creating a more optimum foil profile.
Well, that's the theory... if anyone cares to get into that in great detail, check out C.A. Marchaj's "
Aero-Hydrodynamics of Sailing".
I'd love to hear if some of our experienced AI/TI sailors can confirm this: higher pointing (reefed only) on starboard tack. Bob? A challenge for you, mate...
(Tip: change the furling action from clockwise to anti-clockwise, and try both tacks again?)