Monday, 21 May 2012

(pillow)Case of the week (21/12) - 12

(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 12

Rule 11, On the Same Tack, Overlapped
Rule 18.1, Mark-Room: When Rule 18 Applies
Rule 18.2(b), Mark-Room: Giving Mark-Room
Rule 18.5(b), Mark-Room: Exoneration
Definitions, Clear Astern and Clear Ahead; Overlap

In determining the right of an inside boat to mark-room under rule 18.2(b), it is irrelevant that boats are on widely differing courses, provided that an overlap exists when the first of them reaches the zone.


Summary of the Facts
OL and IW were approaching a mark to be left to starboard. The wind was light and there was a 2-knot current in the same direction as the wind. IW, which had sailed high on the course to the mark to offset the effect of the current, approached it with the current, almost on a run. OL, on the other hand, had been set to leeward and, at position 1, about three hull lengths from the mark, was sailing close-hauled slowly against the current. IW twice hailed for water, and OL twice replied ‘You can’t come in here.’ At the last moment, shortly after position 4 in the diagram, as IW luffed to begin her passing manoeuvre OL tried to give her room but the two dinghies made
contact. There was no damage or injury.

OL protested under rule 11 but was herself disqualified under rule 18.2(b). She appealed, asserting that it was illogical and beyond the intention of the definition Overlap and of rule 18 to consider as overlapped two boats whose headings differed by 90 degrees. She also asserted that the purpose of rule 18 was to protect a boat in danger of hitting the mark that was unable to go astern of the outside boat. She further argued that throughout IW’s approach to the mark until she finally luffed, she was easily able to pass astern of OL, and that IW was not an ‘inside’ boat until a moment before contact.

OL’s appeal is dismissed and her disqualification is confirmed.
The boats were required to leave the mark on the same side and were on the same tack, and so rule 18 applied after position 1 when OL reached the zone. The boats were overlapped from that time until contact occurred, and therefore the first sentence of rule 18.2(b) applied, limiting OL’s rights under rule 11 by requiring her to give IW mark-room. OL did not give IW mark-room, and so is disqualified under rule 18.2(b). It should be noted that OL also broke rule 14, as she could have avoided contact, but, because OL was the right-of-way boat and the contact caused neither damage nor injury, she could not have been penalized had rule 14 been the only rule she broke. As a result of OL’s failing to give IW mark-room to which IW was entitled,
IW broke rule 11 while trying to take that mark-room, and therefore is exonerated under rule 18.5(b). IW also broke rule 14, as she too could have avoided contact, but is not to be penalized, because she was a boat entitled to mark-room and the contact caused neither damage nor injury.

RYA 1964/19

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Many sailors have a hard time understanding that they can be overlapped with a boat far away on a hugely different angle. This case makes it clear once and for all and has been doing it since 1964!

The most common example is not with two boats, but with multiple boats who stack up behind each other to go round the mark and are surprized by a later incoming boat who claims mark room.

120521 case12

When the pink boat enters as fourth boat, the light blue is overlapped on the inside. Before we had the three length zone, this was even more seen as unfair.


  1. Pink can at least be thankful for 18.4 :)

  2. I dont understand theses decisions in light of the definition of Overlap - which admittedly is given in the context of Clear Astern and Clear Ahead. But in my reading, "overlap" is when neither boat is Clear Astern and that depends on a line drawn from the aftermost point of a hull, which does not seem to work in this case. What have I misunderstood? Does overlap mean something different approaching a mark?

    1. The definition of overlap is covering boats on different tack if they are sailing at an angle lower than 90 degrees from true wind.
      If you draw a perpendicular line trough the stern of the pink boat to the left, the blue boat is in front of that line. Hence they are overlapped.

  3. Thanks - I see that for pink and blue, but how does it apply to IW1 and OL1?

    1. IW1 and OL1 are on the same tack. So they are overlapped.

    2. Thanks - I think I get it - the definition applies since they are on the same tack and overlap means that neither is clear astern - which is the case for IW1 and OL1. That is what the rule says but it is not what most people would understand as overlapped.

    3. Not sure which "most people" you are talking about... They are overlapped.

  4. I think a related situation is when the pink boat bears away just before entering the zone so as to break the overlap. It can sometimes seem unfair to the blue boat that does't understand she is no longer entitled to mark room even though when she arrives at the mark she is clearly inside of the pink boat.


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