New rule 18 cleans up some confusion caused in the previous rule 18.

In the previous rule 18, if a boat on port-tack (P) reached the two-length zone clear ahead of a boat on starboard-tack (S), P became the right-of-way boat while they were in the act of rounding the mark. Having the port-tack boat be the right-of-way boat was very confusing. Under the new rules, S remains the right-of-way boat but must give P “mark-room” (see rule 18.2(b)). Also, under the previous rules, if a boat outside of two others entered the zone but then needed to sail back out to give the inside boats room, it was not clear whether rule 18 turned off for that boat (call it X) when it left the zone, such that boats astern that became overlapped on the inside when X reentered the zone were entitled to room. Under the new rule 18, it turns off when a boat leaves the zone for any reason, including giving room to inside boats (see rule 18.2(c)). However, with the new larger zone, it will be possible to remain in the zone longer while still giving room.