Rule 16.1, Changing Course Rule 18.1(b), Rounding and Passing Marks and Obstructions:
When This Rule Applies
When a boat changes course to a new proper course, this may break rule
16.
Question
S on starboard tack and P on port tack were on a leg from the leeward
mark to the finishing line. S has overstood and bears away to clear
the stern of the committee boat at the starboard end of the line.
P can cross S clear ahead if S maintains that course, and P hails
S to hold her course. As she passes the stern of the committee boat,
her proper course becomes a close-hauled course. S comes up to a close-hauled
course at which point there is less than a hull length between S and
P. Both then go head to wind, and they manage to avoid contact by
the narrowest of margins. What rules govern the relationship between
the two boats?
Answer
S is not entitled to room from P under rule 18.2(a) because, as stated
in rule 18.1(b), the boats are on opposite tacks on a beat to windward,
and so rule 18 does not apply. P is subject to rule 10, which requires
her to keep clear of S, but S is subject to rule 16.1, which prohibits
her from changing course without giving P room to keep clear, even
when S is changing to a new proper course. In this situation when
S changed course just after passing the stern of the committee boat,
she did not give P enough room to keep clear and, therefore, broke
rule 16.1. P broke rule 10, but was compelled to do so because S broke
rule 16.1, and so is to be exonerated under rule 64.1(b)