In a big boat series, Class A started their race in a light breeze. One boat didn't have a great start, tacked and was heading slightly above the anchorline of the race committee boat on port tack. When she was almost to the anchorline, a boat in Class B came around the committee boat on starboard tack. If both boats maintained their heading there would have been a collision -- so the port tacker (in Class A) tacked and kept clear. This happened about 40 seconds after the Class A start (which was 4:20 before Class B's start). Did either boat break a rule?
Correct Answer: The Class B boat broke a rule
Both boats were racing or intending to race and therefore the Racing Rules of sailing applied between them. Rule 10 says that a port tack boat shall keep clear of a starboard tack boat. Since the Class A boat (A) tacked to avoid a collision with the starboard tack boat, A did not break a rule.
The incident occurred at 4:20 minutes before the start of Class B, which was 20 seconds before Class B's preparatory signal. This meant that the Class B boat (B) was not racing (because the definition of "Racing" says that a boat starts racing at her prep signal). So even though B was on starboard tack, according to rule 23.1 she was not permitted to 'interfere' with a boat that was racing. Since B caused A to tack, she interfered with A and therefore broke rule 23.1.