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11 On the same tack, overlapped
18.2 Giving Mark-Room

Question 1
Blue and Yellow are approaching a mark to be left to starboard. Rule 17 does not apply to Blue. What is the latest time that Blue may luff?

Answer 1
Rule 18 begins to apply when any part of the hull of either boat is in the zone. From this moment, if Blue luffs and thereafter has to bear away in order to give Yellow mark-room, then Blue breaks rule 18.2. Blue does not break rule 18.2 if she is able to luff while giving mark-room. Yellow is required to keep clear under rule 11. However, she will be exonerated under rule 18.5(a) if she breaks rule 11 because Blue fails to give her mark-room.

Question 2
If Blue will have to bear away to give mark-room, when is she required todo so?

Answer 2
Blue is required to bear away promptly from the moment the first of the boats is in the zone.