CALL MR 41         

Rule 10 On Opposite Tacks
Rule 11 On the Same Tack, Overlapped
Rule 18.2(b) Giving Mark-Room
Rule 18.5 Exoneration
Rule C2.4 While Tacking or Gybing
Definitions Mark-Room and Proper Course

Question
Yellow and Blue are approaching the windward mark on port tack. Yellow enters the zone clear ahead of Blue. Yellow then luffs above her proper course before rounding the mark. Blue bears away to a course between Yellow and the mark. Yellow gybes onto starboard. When next to the mark and while sailing her proper course, Yellow was forced to bear away to avoid Blue. There is a Y-flag. What should the call be?

Answer
When Yellow enters the zone clear ahead, rule 18.2(b) applies and requires Blue to thereafter give Yellow mark-room. Shortly after position 2, when Yellow’s bow is abreast of the mark, Yellow is ‘at the mark’ and from that time on, Blue is then required to give Yellow ‘room to sail her proper course while she is at the mark.’ Between position 2 and 3, Yellow’s course is not consistent with rounding the mark on her proper course so when she luffs she will not be exonerated if she breaks rule 16.1.
At position 4, when Blue overlaps Yellow to leeward she is still required to give Yellow mark-room. If, while taking that mark-room Yellow breaks a rule of Part 2 Section A or rule 15 or 16, she will be exonerated under rule 18.5. Blue has not given Yellow mark-room. Penalize Blue.