Case 7
Rule 11, On the Same Tack, Overlapped
Rule 14, Avoiding Contact
Rule 15, Acquiring Right of Way
Rule 16.1, Changing Course
Rule 17, On the Same Tack; Proper Course
When, after having been clear astern, a boat becomes overlapped to leeward within two of her hull lengths of the other boat, the windward boat must keep clear, but the leeward boat must initially give the windward boat room to keep clear and must not sail above her proper course. The proper course of the windward boat is not relevant.
Boats L and W were dinghies, 15 feet (5 m) in length. About 200 yards (200 m) from the mark, L became overlapped to leeward of W from clear astern. L was less than two of her hull lengths from W. The two boats then sailed alongside each other, about one-and-a-half hull lengths apart, until they were 80 yards (80 m) from the mark. At this point, L luffed slightly to sail directly to the mark, a luff that did not affect W. W maintained a steady course. L never became clear ahead. W's boom touched L's shroud, without damage or injury, and L protested under rule 11. L's protest was dismissed, and she was disqualified on the grounds that she had not allowed W enough room to fulfill her obligation to keep clear as required by rule 15. L appealed.

(Note: Diagram is not to scale. Distances shown are approximate distances from the next mark. At the time of contact, neither boat had reached the zone around the mark.)

L's appeal is upheld. When L became overlapped to leeward of W, W became bound by rule 11 to keep clear of L. At the same time, L was bound by rule 15 to allow W room to keep clear, but that obligation is not a continuing one, and in this case the overlap had been in existence for a considerable period during which W certainly had room to keep clear.

Rule 17 applied to L because, as the diagram shows, she had been clear astern before the boats became overlapped and was within two of her hull lengths of W when the overlap began. L was justified in changing course to sail directly to the mark, provided that she did not sail above her proper course; it is L's proper course that is the criterion for deciding whether she broke rule 17. According to the agreed diagram, L at no time sailed above her proper course.  Therefore L did not break rule 17. Just after position 3 L luffed slightly. Clearly there was room for W to keep clear, and so L did not break rule 16.1. L broke rule 14 because she could have avoided contact with W, but she is exonerated under rule 14(b) because there was no damage or injury. W is disqualified under rule 11, and L is reinstated.