18.3 Tacking at a Mark
If two boats were approaching a mark on opposite tacks and one of them completes a tack in the two-length zone when the other is fetching the mark, rule 18.2 does not apply. The boat that tacked
(a) shall not cause the other boat to sail above close-hauled to avoid her or prevent the other boat from passing the mark, and
(b) shall give room if the other boat becomes overlapped inside her, in which case rule 15 does not apply.