Monday, 6 February 2012

(pillow)Case of the week (06/12) – 24

(This is an instalment in a series of blogposts about the ISAF Case book 2009-2012 with amendments for 2010. 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
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. If she takes unnecessary action that causes contact, she fails to keep clear as required.
Assumed Facts
Two boats, A and B, are on a broad reach 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 becomes overlapped close to leeward of A’s stern.
  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?
  3. What are A’s obligations under rule 11?
Answers As soon as B becomes overlapped, 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 promptly. If A does so in a seamanlike way but some 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.

Although B obtains right of way under rule 11 as soon as the overlap begins, her right of way is limited during the time that rule 15 applies.

RYA 1970/2


In these low number cases we get back to the basics. The rules have been set up to clearly define the right-of-way boat and the keep clear boat, by giving four BASIC row rules.
If those four were the only ones sailors had to apply, the game would drastically change. The right-of-way boat would be master in all things, could change course as she pleased and the keep clear boat would be forced to anticipate and stay far away.

If we would not have a couple of LIMITATIONS on the right-of-way boat, the situation described in this case would quickly become very ‘unfair’ to the keep clear boat. As soon as B gets the overlap A would break rule 11. Anticipating this and trying to luff to create more space wouldn’t help much, because B would simply chase and head up as well.

This is the reason we have those LIMITATION rules; RRS 15, 16 and 17. To give the keep clear boat a fair opportunity to fulfil it’s obligation. These rules do not negate (switch off) the basic row rules, they only limit them. The keep clear boat must respond quickly and in a seamanlike manner. If she does that, but still fails to keep clear, it is usually because the right-of-way boat didn’t apply one of the limitation rules.

If the argument in the hearing between two boats hinges on the balance between 11 and 15, you can ask the helmsman of the keep clear boat where he was looking, at the moment the boat started to change course. If the answer is: “at the bow of the leeward boat” that might be a good indication it must have been very close. If the helmsman was looking ahead, that usually indicates he felt comfortable changing course without immediately hitting the leeward boat.


  1. I knew we should have protested at the Club afterwards!

  2. I knew we should have protested those bums!


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