18.3 Tacking in the Zone
If a boat in the zone passes
head to wind and is then on the same tack
as a boat that is fetching the mark,
rule 18.2 does not thereafter apply between them.
The boat that changed tack
(a) shall not cause the other boat to sail above close-hauled to avoid contact or prevent the other boat from passing the mark on the required side, and
(b) shall give mark-room if the other boat becomes overlapped inside her.