Answer: Right here, Al can tack and block Sue from tacking for the finish line until both have overlaid the finish line (see finish line in the previous panoramic pic) and Al, the first to be able to tack, should be in a position to easily beat Sue to the line. What would more likely happen here is that Sue would tack almost simultaneously to avoid overlaying the line, only to hear Al yell "Tacking!!!" At which time Rule 13 would apply, the part that says "If two boats are subject to this rule at the same time, the one on the other’s port side ... shall keep clear. " And Sue, being on Al's port side would have to abort her tack (slow) or foul Al. And as soon as Sue was committed to tacking back, Al could tack for the line with far better speed than Sue, and beat her across the line. All this crossed my mind in the second or two shown above, but Richard and I had discussed the possibilities before this race and realized it did not matter which of the two of us won this race because if there was a tie-breaker, it would come down to who beat whom in the last race, i.e. even if we beat Sue in this race, we'd have to beat her again in the finale or lose tie-breaker.