An obligation to give mark-room continues until the entitled boat has passed the mark, leaving it on the required side. The definition Mark-Room defines the space a boat is required to give, and the other boat is exonerated under rule 21 only if she is sailing within that space.
Facts Boats A and B are sailing downwind approaching a mark they are required to leave to port. The course to the next mark is a beam reach. A reaches the zone clear ahead of B and rounds the mark wide. At position 3 B becomes overlapped with A. At position 4 A is more than one length to leeward of the mark when B, alongside the mark, luffs around the mark inside A.
After position 4 A luffs quickly; B responds promptly but at position 5 is unable to keep clear. Both boats protest.
Question 1 Is B required to continue to give A mark-room after position 3, and does she fulfill this requirement?
Answer 1 Yes.
B is required to give A mark-room under rule 18.2(b). This includes room for A to leave the mark on the required side, which she has not completed at position 4.
Between positions 4 and 5 B gives A room to complete her passing of the mark, and also gives her room to sail her proper course in compliance with rule 18.2(c)(2).
Question 2 Which boat is penalized and which boat is exonerated at position 5?
Answer 2 A is penalized and B is exonerated.
After position 3, A’s proper course is no longer to sail close to the mark. Therefore the mark-room to which she is entitled no longer includes room to sail to the mark and, when she luffs between positions 4 and 5 without giving B room to keep clear, she breaks rule 16.1 and is not exonerated under rule 21(a).
Before A luffs, B is keeping clear. When A luffs, B is entitled by rule 16.1 to room from A to keep clear. B is therefore exonerated under rule 21(a) for breaking rule 11 at position 5.
The answer would be the same if B had been able to keep clear of A at position 5, but only by making contact with the mark. A would have broken rule 16.1 and B would have been exonerated under rule 21(b) for her breach of rule 31.
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