Section B – Boat on boat
RS CALL B10
Definitions, Mark-Room
Rule 11, On the Same Tack, Overlapped
Rule 18.2, Giving Mark Room
Rule 23.2, Interfering with Another Boat
When boats are required to leave a mark on the same side, the windward outside
boat must keep clear under rule 11 even if the leeward boat cannot fetch the mark.
After passing the mark, the windward boat must continue to keep clear, even if she is
sailing her proper course. If the leeward boat causes the windward boat to alter
course, she breaks rule 23.2.
Assumed Facts
Two boats, L and W, approach the windward mark on starboard tack below the layline
to the mark. The mark is to be rounded to port. L is unable to fetch the mark and
has to sail the wrong side of the mark. W fetches the mark by luffing, rounds the
mark and bears away onto the next leg.
Question
How do the rules now apply between the two boats and what are their rights and
obligations from position 3?
Answer
As the windward boat, W has an obligation to keep clear under rule 11 throughout
the incident. The boats are overlapped when they enter the 4-lengths zone and, from
that moment, W is required by rule 18.2(b) to give mark-room to L. However, L is
unable to fetch the mark and is not entitled to room to tack in order to pass the mark
on the required side. Therefore W's only obligation is to keep clear, which she does.
Neither boat breaks a rule.
After W rounds the mark, the boats are on different legs and both are required by rule
23.2 not to interfere with each other, except when sailing their proper course.
However, while the boats remain on the same tack, W must continue to keep clear of
L under rule 11. This applies even if W is sailing her proper course. If L causes W to
alter course, L interferes with a boat sailing on another leg and she breaks rule 23.2.