How would you decide this?

Dave Perry’s 100 Best Racing Rules Quizzes highlights specific aspects of the racing rules in a fun format designed to help you become more familiar with The Racing Rules of Sailing. Here is one of the quizzes:

Quiz 48
Boats A and B are approaching a mark to be left to port on starboard tack. The boats need to gybe around the mark to sail on a reach on port tack to the next mark. A reaches the zone clear ahead of B, sails to the mark and gybes. After her gybe, B has to luff to avoid A and hails, “Protest!” You are on the protest committee; how would you decide this?

You are on the protest committee…how would you decide this? Answer below.

Quiz 48 Answer:
B’s protest is disallowed. A reached the zone clear ahead of B, and was therefore entitled to mark-room under rule 18.2(a)(2), Giving Mark-Room.

From position 1, A’s proper course was to sail close to the mark; therefore she was entitled to room to sail to the mark, room to round the mark in a seamanlike way leaving it to port, and room to leave it astern (see the definitions Mark-Room and Room). “Room,” as defined by the definition Room, is “the space a boat needs…while maneuvering promptly in a seamanlike way,” which includes space to avoid touching the mark and to comply with her obligations under the rules of Part 2 with respect to the boat required to give her mark-room as well as any other nearby boats (see World Sailing Cases 21 and 118).

Because the boats needed to sail on port tack to sail directly to the next mark, mark-room included room for A to gybe and sail on port tack during her rounding maneuver. Therefore, she is exonerated (freed from penalty) by rule 43.1(b), Exoneration, for her breach of rule 10, On Opposite Tacks. B complied with her obligation to give A mark-room under rule 18.2(a)(2).

Source: US Sailing