CALL UMP 42          

Rule 11 On the Same Tack, Overlapped
Rule 18.2 Giving Mark-Room
Rule 18.5 Exoneration
Rule C2.4 While Tacking or Gybing
Definitions Mark-Room

Question
Blue and Yellow approach the windward mark on starboard tack with Yellow overlapped on the inside of Blue at the zone. After passing the port tack lay-line both boats luff head to wind, at position 3 Blue has given Yellow enough room to tack. Both boats continue forward with the gauge between the boats reducing until, before leaving the zone, Yellow passes head to wind. There is contact as Yellow’s stern swings. Both boats Y-flag. What should the call be?

Answer
Penalize Yellow.
Blue is right-of-way outside boat when she reaches the zone and must give Yellow mark-room. Mark-room includes room to sail to the mark and then room to sail a proper course while at the mark. Mark-room also includes room to tack as Yellow is overlapped to windward and on the inside of Blue.
Blue complied with rule 18.2(b) by giving Yellow room to tack at position 3. When Yellow chose not to tack and continued past the mark; she was now neither sailing to the mark nor sailing her proper course at the mark.
At position 5 while Yellow was subject to rule 13 she did not keep clear of Blue, Yellow cannot be exonerated under rule 18.5(a) or (b) for breaking rule 13.
If, at position 3, Blue did not give Yellow room to tack and there was a Y-flag, penalize Blue for breaking rule 18.2(b) and exonerate Yellow under rule 18.5 for breaking rule 13.