Sunday, 26 February 2012

Seven at the Leeward Mark; Part 2

As promised I would try to explain why I think that the three outside boats don’t have rule 18 rights or obligations between them in this post: Seven at the Leeward Mark, LTW Readers Q&A (60)

To do this I’ve created a much simpler situation involving three boats:

120226 7atwm1a

We have Grey, Purple and Red all sailing toward a leeward mark to be left to port. In position one Red enters the zone. Rule 18 switches on.

Both Grey and Purple have to give Red mark-room because she entered the zone clear ahead (RRS 18.2(b), second sentence.)

However, between Grey and Purple, rule 18 is not yet applicable. Provided she does so with rule 16.1 limitation and has no rule 17 limitation, Purple could luff and keep Grey outside the zone. She does not have to give mark-room to Grey, although rule 18 is switched on between her and Red.


120226 7atwm1b

Now we come to position two.

Both Grey and Purple still have to give mark-room to Red. In position 2 Purple enters the zone so now rule 18 is applicable between her and Grey. Grey has an inside overlap and is entitled to mark-room (RRS 18.2(b), first sentence)








This simplified scenario indicates that although all three boats are subject to rule 18 once Red enters the zone, that rule does not apply between the two outside boats as long as they themselves are not in the zone.

If I apply that principle to our Seven Boat problem:


In position two we have four boats inside the zone and three outside. Red, Purple and Blue all have to give mark-room to the inside ‘four’. But because none of those three have reached the zone themselves, RRS 18 does not apply between them. Red must keep clear of Purple, who must keep clear of Blue, all under RRS 11.

I hope I’ve clarified my view, and now await your punishment.


  1. Your logic is fine Jos for the clear-ahead situation. Applying it to the seven boat situation is a fallacy.

    The reason why 18 it doesn't apply to grey and purple is between they are not overlapped to any boat that is in the zone. 18.2(b) ties grey and red, and (independent from this) purple and red. 18.2(a) does NOT apply between grey and purple.

    In Uli's 7 boat scenario, all 7 boats are overlapped to each other and at least one of them has reached the zone. Thus, 18.2(a) applies to ALL of them, since all of them are overlapped and at least one is inside the zone.

    Let me try another way. Delete Blue for the sake of argument. Case 114 applied absolutely literally to the situation between Purple (A), Red (B), and Light Blue (C), says that "rule 18.2 requires A [Purple] to give B [Red] sufficient space for B [Red] to give C [Light Blue] mark-room." The reason is that A, B, and C are overlapped, and at least one of them (Light Blue) is in the zone. Add dark blue. Now it's four of them. I really fail to see why it is that, according to you, the logic that binds Purple to give Red space for Red to give Light Blue mark-room does NOT extend to Dark Blue giving Purple space for Purple to give Red space for Red to give mark-room to Light Blue.

    1. I do not understand your reference to overlapped.
      It does not make any difference if they are all overlapped or not. Rule 18 does not turn on or off by being overlapped.
      The only criteria for rule 18 to apply between two boats is that one of them must be in the zone.
      For instance Rule 18 applies between Red and Light Blue because LB is in the zone. 18 applies between Red and Green because Green is in the zone. etc for both Yellows
      Purple has the same with the four inside boats
      Purple has no rule 18 with Red because neither of them is in the zone! The same for Blue.
      You cant's use 18.2(a) if 18.1 is not applicable.

      Only after you've fulfilled the basic criteria in 18.1 (and none of the exceptions apply) can you look at 18.2.

    2. Jos, all seven boats are required to leave the mark on the same side, and at least one is in the zone, none of the exceptions applies. So i can't see why 18.1 would not apply, there is nothing in the rules stating that you have to apply that to pairs of boats, as it would then read "...applies between two boats..." But it applies between any number of boats in my view, as it doesn't state any different.

      In your split example, the difference is that the course of grey is not influenced by her need to give room to red, if it would, then purple would have to give enough room to grey for that.

  2. This is not what case 114 says... how can purple give mark room to light blue without giving space for red to give mark room to blue? And we're back to the issue of whether rule 18 applies only pairwise. Nothing in the rule restricts it to applying to only two boats at a time, and case 114 makes it clear that it should not be applies only pairwise...

  3. The problem is, that the rules are written only for pairs of boats (good for umpires and bad for judges). The question is, what should the red Boat do. To her left she has to give mark-room (RRS 18.2(b)) and to her right she has to keep clear (RRS 11). If the boats are Star in winds of 15 knots it end in desaster and no rule other than 14 helps red.
    In the rules of 2009 light blue was an obstruction to red, purple and dark blue, because they had ro give mark-room to light blue. But this part of the definition obstruction was deleted in 2010 because of other good reasons. In my oppinion most of the sailors are not aware to this problem. Thank you Jos for the discussion, and sorry Kidding.

    1. Uli, why do you both keep ignoring case 114? It is explicitly explained there that 18 not only ties two boats at a time, but that it also means that a "sandwiched" boat like red has right to space in order to fulfill her obligations to give mark-room.

      On the pairs of boats issue... what do you base your statement on? I disagree that the rules are written ONLY for pairs of boats.

  4. Jos,


    There are 2 criteria for rule 18 to apply between boats (that is more than one including,but not exclusively, between two boats):

    - boats must be required to pass the mark on the same side;
    - one of them (that is one of two OR MORE) must be in the zone.

    Once these criteria apply, unless one of 4 exceptions apply) rule 18 applies (rule 18.1)to all the boats involved.

    If boats are overlapped then 18.2(a) applies unless 18.2(b) applies.

    In the scenario with 7 boats the criteria for applying rule 18 are met. Red is required to give mark room to Light Blue (18.2(b)). This includes room for Light Blue to give mark room to the other boats inside.

    Purple is overlapped outside Red. Because 18.2(b) does not apply between Purple and Red, but rule 18 does apply to all the boats involved (because (more than) one is in the zone), then, because they are overlapped, rule 18.2(a) applies between Purple and Red. Purple must give Red mark room, which includes room to give mark room to the boats inside.

    Now consider your 3 boat scenario:

    If Red were to stop at position 1 Grey and Purple would have to give mark-room because rule 18 applies and Red had entered the zone clear ahead (18.2(b)) . If both Grey and Purple become overlapped outside Red, but before Purple enters the zone:

    - rule 18 applies for the 3 boats
    - rule 18.2(b) does not apply between Purple and Grey;
    - they are overlapped

    Therefore 18.2(a) applies and Purple must give mark-room!

    The key point is that there is nothing in rule 18.1 that limits the application of rule 18 to pairs of boats. Once rule 18 applies it applies to all boats involved (even though it has no practical effect). Thus a boat that has just started a leg is bound by rule 18.2(b) if a boat ahead enters the zone of the next mark, even though this may be some distance away. This only of relevance for wierd forms of racing, like team racing, where the oat ahead may decide to wait for the trailing boat.


  5. I agree with Jos' logic. And may I added follows.When one part(for example group A, four inside boats) has relations between them and another group B (three outside boats) has same relations with group A it is not mandatory that they have same kind of relations between them.It is basic Theory of sets.

  6. @ Gordon,

    I think the point is that in "applying" the rules, it is customary to examine boats in pairs. So that if there are more than two boats, it helps to analyze the applicable rights and obligations by taking the boats in pairs. That said, it seems to me that Rule 18 does apply to the boats outside of the zone because as outside overlapped they owe the inside boats "mark room" just as do the outside overlapped boats that are inside the zone. Therefore, if a luff by dark blue will deprive yellow(1) of mark room by forcing windward boats to luff too close to yellow(1), foul on dark blue. In addition, 16.1 prohibits dark blue from changing course without allowing a burdened boat room to keep clear. Room is a defined term and means:

    The space a boat needs in the existing conditions while manoeuvering promptly in a seamanlike way.

    The boats to windward of dark blue all owe one or more boats to their respective windward sides either mark room or room to keep clear. I feel (and there are appeals cases to support me) that a boat which maneuvers so as to cause a second boat to collide with or infringe on the rights of a third boat (by definition this is unseamanlike by the second boat) fails to give the second boat room to keep clear. Therefore, any luff by dark blue that would cause the boats to her windward to luff in an unseamanlike manner would be a foul by dark blue. violation of 16.1 and/or 18.

  7. This is getting hopeless... let me keep trying anyway. Preamble of part 2:

    "The rules of Part 2 apply between boats that are sailing in or near
    the racing area and intend to race, are racing, or have been racing.
    However, a boat not racing shall not be penalized for breaking one
    of these rules, except rule 23.1."

    There is no such thing as "apply between pairs of boats" mentioned. "Between" implies that the rules of part 2 implies to sets of at least 2 boats. But it may apply to larger sets. Consider for another example rule 15. It says "When a boat acquires right of way, she shall initially give the other
    boat room to keep clear, unless she acquires right of way because of the other boat’s actions." The typical application is when a boat acquires ROW to leeward from clear astern. If the windward boat has another boat to windward herself, then 15 means that not only does the new ROW boat have to give room to keep clear as if only the two of them were on the water, but taking into account that when maneuvering to keep clear, the "sandwiched" boat has to change course in such a way that the windward boat can in turn keep clear. Following your logic, then "no rule other than 14 helps the sandwiched boat," and she would have to either break 11 against the leeward boat or 16.1 against the windward boat. This makes no sense.

  8. Jos, maybe you can append the following note to the 15 example that I used... I feel like I'm being trolled at an internet forum! LOL

    Note: the fact that the new leeward boat has to give room for the "sandwiched" boat to keep clear while at the same time holding to rule 16.1 towards the windward boat has nothing to do with the windward boat being an obstruction to the sandwiched boat (she is not). Likewise, the red boat giving mark-room to light blue has nothing to do with light blue being an obstruction to her. But red is bound by rule 18 to give mark-room to light blue. If an outside boat leaves no space for red to give this mark-room to light blue, she is breaking rule 18 against blue by doing so.

  9. To latindane:
    I would be happy to agree with you, but in rule 18.2(a) and 18.2(b) first sentence is written: .... shall give the inside boat.. with boat (singular) not boats (plural). I agree also with case 114, but in case 114 the sandwiched boat is entitled to mark room to the outside boat.
    I think the situation is worth for an Q&A with the hope, that your oppinion is right.

  10. I think the first part of case 114 applies no matter whether boat B is entitled to mark room or not. B is entitled to space to give C mark-room, whether or not she's got right to mark-room from A yet.
    To clarify: I don't argue that the outside sandwiched boats B are entitled to mark-room under rule 18. But under rule 18, the outside boats must give the boats inside the zone mark-room. This includes giving space to the sandwiched boats (without right to mark-room yet) to give mark-room to the inside boats. This, I believe, is the main point of case 114.

  11. So responding to Uli's question:

    The dark-blue boat, you will agree with me, has to give mark-room to the light-blue boat. This includes giving the sandwiched boats space to give light-blue mark-room. Case 114.


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