CASE 24        

Rule 11, On the Same Tack, Overlapped
Rule 12, On the Same Tack, Not Overlapped
Rule 15, Acquiring Right of Way

When a boat becomes overlapped to leeward from clear astern, the other boat must act promptly to keep clear. When she cannot do so in a seamanlike way, she has not been given sufficient room.

Questions
Two boats, A and B, are broad reaching on starboard tack in a light breeze on their proper courses for the next mark some distance away. Initially, B is clear astern of and directly behind A but is travelling slightly faster and establishes an overlap to leeward of A’s stern but inside the end of her boom.

1. When are B's obligations under rule 12 replaced by her rights as leeward boat under rule 11?
2. What are B's obligations under rule 15?

Answers
As soon as B establishes the overlap, rule 12 ceases to apply. A becomes bound by rule 11, and B by rule 15, which embodies the principle in the rules that when the right of way suddenly shifts from one boat to another, the boat with the newly acquired right of way must give the other boat space and time for response and thus a fair opportunity to keep clear. B’s obligation under rule 15 is not a continuing one; it protects A only temporarily, and only if she responds promptly after the overlap begins.

Rule 11 requires A to keep clear and, if this requires her to luff, she must do so. If, in so doing, any part of her hull, crew or equipment touches any part of B’s hull, crew or equipment, B has broken rule 15 by not giving A enough room to keep clear. However, if A luffs higher than is necessary to keep clear of B and,
as a result, causes contact with B, A breaks rule 11.

RYA 1970/2