Rule 17 On the Same Tack; Proper Course
A boat has no obligation to be on a proper course in anticipation of a proper course requirement that does not yet exist. A new requirement to sail a proper course applies from that time and from the position the boat is then in.
Question
Y and B are reaching, both above their proper courses, with B just clear ahead and one length to windward of Y. B bears away so that the boats become overlapped. Y promptly bears away to a proper course. B protests. What should the call be?
Answer
Rule 17 begins to apply when the boats become overlapped. From that moment on, Y must sail no higher than her proper course from the position she is in when the overlap begins (position 2) - i.e., she must sail no higher than a course that she would sail in the absence of B from position 2 to reach the next mark as quickly as possible. By bearing away promptly, Y complies with this rule.
The answer is the same if the overlap is established through Y sailing faster rather than B bearing away.
A boat has no obligation to be on a proper course in anticipation of a proper course requirement that does not yet exist. A new requirement to sail a proper course applies from that time and from the position the boat is then in.