A tacking boat does not establish her rights until she has completed her tack.

RULE 

Part 2 - When Boats Meet

Section A - Right of Way

Rule 13.  After a  boat passes head to wind, she shall keep clear of other boats until she is on a close-hauled course.  During that time rules 10 (starboard/port), 11(windward/leeward) and 12 (clear ahead) do not apply.

If two boats are subject to this rule at the same time, the one on the other’s port side or the one astern shall keep clear.