Monday, 25 June 2012

(pillow)Case of the week (26/12) - 07

(This is an instalment in a series of blogposts about the ISAF Case book 2009-2012 with amendments for 2011. All cases are official interpretations by the ISAF committees on how the Racing Rules of Sailing should be used or interpreted. The cases are copied from the Casebook, only the comments are written by me.)

(pillow)Case picture

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.

Summary of the Facts

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, although 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 fulfil her obligation to keep clear as required by rule 15. L appealed.

Case 7 diagram


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. 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 cannot be penalized because there was no damage or injury. W is disqualified under
rule 11, and L is reinstated.

RYA 1963/10


Like I have stated in previous posts, it is the right of way (leeward) boat that decides what the proper course is. If she has a reasonable argument why she sailed that course, she does not break rule 17. Only when it is absolutely crystal clear that she would not have done the same – in absence of the other boat – then rule 17 might be broken.

This certainty becomes greater the closer to the mark the boats are.


  1. If we accept the drawing as submitted, which both boats did, the boats are each about 15 yards long, so W is slightly more than one length from the mark. Since she is owed mark room by L, does she not have the right under rule 18 to sail "to the mark" and L improperly luffed her while in the zone?

    1. DKS, I think you are right.
      The drawing needs to be changed to accommodate the 3 BL Zone.
      I'll pass that on to the people who do the Casebook.

      The principle of the case however does not change. Just picture the collision happening outside the zone.


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