In the diagram Blue and Yellow are both on port tack, approaching a leeward mark. Both boats are on a course above the mark. Yellow is to windward and overlapped, and must keep clear. At position 2, Blue enters the zone, with the boats still overlapped. Blue now has to give mark-room to Yellow. If we look at the definition of mark-room, part (a) says that mark-room includes room to sail to the mark. Blue has to bear off and give Yellow room to sail to the mark. She does this from position 3 to position 6.

Part (b) says that Blue has to give Yellow room to round or pass the mark on the required side. Blue does this in positions 7 and 8. Room includes space for Yellow’s stern to swing as she turns. It also includes the space required to take down her spinnaker promptly in a seamanlike way if she is flying one. We see this in the definition of room which says “The space a boat needs in the existing conditions, including space to comply with her obligations under the rules of Part 2 and rule 31, while manoeuvring promptly in a seamanlike way”. You can see in the diagram that Blue gave Yellow room, but not as much as Yellow might like. Yellow doesn’t have room to sail “wide and close”. She has space to manoeuvre promptly in a seamanlike way. She is not entitled to space for a tactical rounding. She also has space to avoid hitting the mark, since hitting the mark would break rule 31.

The final part, part (c), of the definition of mark-room says that Yellow has space to leave it astern. At position 10 Yellow has left the mark astern. Blue is no longer required to give her mark-room and is now entitled to luff Yellow again, which she does at position 11.

You may have noticed that through out this incident Blue is the leeward overlapped boat. Mark-room does not change the right-of-way, so Blue is still the right-of-way boat but Blue is still required to give mark-room and Yellow is exonerated for breaking Rule 11. This is covered in 43.1(b).

Mark-Room Room for a boat

(a) to sail to the mark when her proper course is to sail close to it,

(b) to round or pass the mark on the required side, and

(c) to leave it astern.

Room The space a boat needs in the existing conditions, including space to comply with her obligations under the rules of Part 2 and rule 31, while manoeuvring promptly in a seamanlike way.

11 ON THE SAME TACK, OVERLAPPED

When boats are on the same tack and overlapped, a windward boat shall keep clear of a leeward boat.

18.2 Giving Mark-Room

(a) When the first of two boats reaches the zone,

(1) if the boats are overlapped, the outside boat at that moment shall give the inside boat mark-room;

(2) if the boats are not overlapped, the boat that has not reached the zone at that moment shall give the other boat mark-room.

When a boat is required to give mark-room by this rule, she shall continue to do so for as long as this rule applies, even if later an overlap is broken or a new overlap begins.

43 EXONERATION

43.1

(b) When a boat is sailing within the room or mark-room to which she is entitled and, as a consequence of an incident with a boat required to give her that room or mark-room, she breaks a rule of Section A of Part 2, rule 15, 16, or 31, she is exonerated for her breach.

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