Tuesday, 24 November 2009

How instantaneous is Mark-room?

During an iShares Cup event I had a discussion about mark-room. Particularly about how fast an outside boat has to act when she has the obligation to give mark-room.

Here’s how see this.
One of the basic changes in this rules cycle is the deletion of ‘about to round the mark’ principle. Rule 18 now has a very sharp on/off switch.
Provided they are approaching a mark they are required to leave on the same side, rule 18 is applicable if one of the boats is in the zone. The moment the hull of one of them passes the three-lengths circle, rule 18 is on. You can compare it with passing head to wind. As soon as a boat is one degree passed head to wind, rule 13 is on. She is tacking boat and must keep clear. No ifs, buts or maybees. No ‘beginning to keep clear’ or ‘must start acting to keep clear’. Instantaneous.
If you pass head to wind and a row boat must change course, you’ve broken rule 13. Even if – for instance in a dail-up in a match race – a gust of wind makes you pass head to wind involuntary.
The same is true for rule 18.
Imagine two catamarans approaching a mark at a reaching angle on different tacks. Yellow wants to force the other passed the mark. Rule 18.4 is not applicable – it’s a gate mark – and Yellow can sail as far as she wants.

Yellow misjudges the angle and one of her hulls enters the zone. She’s still reaching and it takes her a couple of seconds to realize she’s too close and to bear away to give the other boat room to sail to the mark – as she is now required to do.
From the moment rule 18 is on she is required to give mark-room. From that moment the inside boat must be able to sail TO the mark.

Like you can see yourself, in position three and four Blue cannot sail to the mark. Because of Yellow, Blue is not able to point its bow toward the mark until position six.
For all what it is worth, Yellow has done everything seamanlike to give mark-room from the moment she realized she was in the zone. She reacted reasonably prompt and kept well clear once she’d gybed.
Nevertheless she broke rule 18.2(b) in my opinion. Like with passing head to wind – there is no ‘grace period’. From the moment her port hull entered the zone she was required to give mark room – and she did not do that. Blue could not sail to the mark, but had to wait until Yellow was pointing away.
This is one rule were Yellow needs to anticipate the situation and act accordingly. Stay well clear of the zone if you want to luff another boat or be prepared to take a penalty for breaking rule 18.2(b).

I’ve heard different opinions, but up until now no arguments why I should change my mind.
Perhaps you can?


  1. I think your boat is ok here and the rule does not apply as instantly as you say. I have looked atMatch Race Call UMP 24, where it says If Blue has to bear away to give Mark Room she is required to do so promptly from the moment the first of the boats is in the Zone.

    As a matter of interest what if yellow went round the other mark, there would then be no 18 on the first mark and yellow would escape in any event. What do you think?

    Mike Butterfield

  2. Why is it different from rule 17? Imagine 2 boats running downwind. A is clear ahead. B is clear astern and sailing above her proper course. B then establishes a rule 17 overlap on A. Does B instantly break rule 17, or does she avoid breaking the rule so long as she promptly bears off to proper course?

    Also, in team and match racing we have an answer to this question, and its the opposite of the one you posit... see call Ump24...

  3. @ Anonymous & Mike,
    Ump Call 24 shows boats who practically do not have to bear away to give the other boat mark room. Only a very slight course correction is needed. Something they can do very prompt.
    In the situation above the angle is more then 90 degrees. I still think that the rule - as it is written at this moment - indicates that yellow breaks 18.2, because of the sharp on/off border.
    Because of the angle entering the zone, Yellow is not in a position to bear away promptly?

  4. Jos,
    It's an interesting question. Call UMP 24 gives a clear answer though. I understand this call in the same way Mike does.

    There is, in my opinion, a significant difference between this situation and your comparison to the rule 13 situation. It's about the difference between right of way and room.

    Rule 13 says that a tacking boat has to keep clear of another boat. So the other boat has right of way (according to the preamble of section A) and is entitled to "sail her course with no need to take avoiding action [...]" (definition of Keep Clear).

    In the rule 18 situation, when yellow enters the zone, blue is entitled to mark-room, but it is not a ROW boat. So it is not entitled to "sail her course with no need to take avoiding action". It must only be granted mark-room, which is, according to its definition, some kind of room (and not ROW).

    Room is "the space a boat (blue) needs to in the existing conditions [...]".

    To me, this is less strong and this might be the key to Call UMP 24.

    Anyway, something like rule 15 can't apply in this situation, because the blue boat doesn't acquire ROW. So blue can't give room to keep clear. It would rather be giving room to give room.

    What's your opinion on that?

    Concerning yellow going round the other mark, IMHO rule 18 would still apply at the first mark (18.1 first sentence).


  5. I have to disagree that the implication of Rule 18 turing on when the first reaches the zone requires an outside ROW boat to instantaneously allow the boat entitled to mark room to point right at the mark. The definition of room says it is the space required to "maneuver promptly in a seaman like manner". Maneuver implies changing course and promptly is not instantaneously, it implies a reasonable amount of time, which depends on the conditions and the boats being sailed.

    If I were Yellow, I would show that at the speed we were traveling, to maneuver promptly required about a boat length to turn, and the maneuver that I and Blue made was seaman like. Therefore, I provided the mark-room required to sail to the mark. I will agree that if the conditions are such that Blue cannot maneuver in a seaman like manner to the mark, Yellow might have to begin to turn sooner than the moment she reaches the zone. But, under no circumstances will I agree that Blue must be able to point directly at the mark the instant that Yellow reaches the zone.

  6. On the 18.1 are you sure the rule would apply if you went round the other mark. The boats are not required to leave this mark on a required side as they may choose to leave the other mark on a required side.

    Mike B

  7. Rule 18 applies to both marks of a gate mark. You can no longer pass on the wrong side of a gate mark but must sail between them. Read the new Rule 28 "Sailing the Course".

  8. Mike,
    I'm not sure about 18.1, but as far as I understand it, both gate marks have a required side.

    28.1, the string rule, says in (c) that the string shall [...] "pass between the marks of a gate from the direction of the previous mark."

    So my understanding is that both marks have a required side (mark 1 shall be left on starboard and mark 2 on port), irrespective of which mark is actually being rounded.

    But - honestly - I'm not an expert on that. These are just my thoughts about this issue. Please correct me if I'm wrong.

    Any comments are welcome!

  9. I disagree, RRS 28.1(c) says "pass between the marks of a gate from the direction of the previous mark. Therefore, assuming that the boats were coming from directly from the previous mark, they are going through incorrectly.

  10. Could aquiring the right to room also be interpreted in the same was as acquiring ROW ? There are several examples quoted in rules, scenarios etc that a boat does not have to anticipate that another boat will acquire ROW and so does not have to do anything until ROW is acquired. I would interpret this situation in a similar way, the Yellow boat is on Stbd and is ROW boat - she does not have to do anything to give room until the blue boat is due it, when yellow enters the circle. In this example she did everything reasonable to give room once it was due and so is OK. Yellow doesn't have to anticipate that blue wants to or is going to sail directly to the mark.


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