Case 15
Definitions, Mark-Room
Rule 12, On the Same Tack, Not Overlapped
Rule 13, While Tacking
Rule 18.1(b), Mark-Room: When Rule 18 Applies
Rule 18.2(b), Mark-Room: Giving Mark-Room
Rule 18.2(c), Mark-Room: Giving Mark-Room
In tacking to round a mark, a boat clear ahead must comply with rule 13; a boat clear astern is entitled to hold her course and thereby prevent the other from tacking.

case_15.png 42.9 KB
A and B are approaching the windward mark which they are required to leave to port. They are close-hauled on parallel courses with A clear ahead. A expects B, when she can tack and fetch the mark, to tack to round it and head for the next mark. Instead, B holds her course as shown in the diagram and sails on well past the mark.

Has B the right to hold her course in this way and, thereby, prevent A from tacking?

Yes. While A remains on port tack, B is required to keep clear by rule 12 and, as A was clear ahead when she reached the zone, B is required by rule 18.2(b) to give A mark-room as well. Provided B keeps clear of A and gives A mark-room if A luffs (even if A luffs as high as head to wind), B is entitled to sail any course she chooses, including holding her course. However, B is no longer required to give A mark-room after A leaves the zone (see rule 18.2(d)).

The mark-room to which A is entitled does not include room for her tack (see the last sentence of the definition Mark-Room). If A were to pass head to wind, then at that moment all parts of rule 18 would cease to apply because the boats would be on opposite tacks (see rule 18.1(b)). In addition, A would no longer have right of way under rule 12, and B would become the right-of-way boat under rule 13.
Cookies help us deliver our services. By using our services, you agree to our use of cookies. Learn more