Thursday, 26 August 2010

LTW Readers Q&A | 043; Approaching a mark?

Send in by Brad this readers Q&A is about rule 18 and approaching a mark.

Here’s what he wrote:


I have searched for ISAF rules interpretations in the past and have been directed by Google to your blog on many separate occasions.
I am not sure if you answers questions.  In case you do I will send you my question about a windward mark rounding below.  If you do not answer questions, can you recommend a  good site or blog where I might be able to get an answer from ISAF judges?

Thank you in advance for your help,

I overheard this situation that took place recently at my yacht club.  I was asked my opinion.  I gave my opinion but after I heard what the PC decided and re-read the rule book, I have some questions.  This is what happened:

Two 28 foot E-scows are sailing on port. They are sailing to windward, towards a mark to be rounded to port. Boat A is clear ahead and 1+ boat length to leeward of boat B.  They both enter the zone on port, boat A ahead of boat B. Boat A tacks onto starboard (according to the protest approximately 60 feet from the mark).  Boat  A arrives at a close hauled course and Boat B has enough time and room to respond.  Boat B tacks directly in front and slightly to leeward of A.  Boat A has to take avoiding action and heads up to avoid contact with B.  (Boat A was able to avoid in a seaman like way).   It is in question as to weather boat A had to sail above close hauled, as she was reaching slightly towards the mark at the time.

Boat A protested boat B under rule 18.3(a)

The protest was denied since boat A neither hailed protest or flew a flag.  However they heard the protest and decided if the protest had been filed properly that under rule 18.3(a) boat B would have been given a DSQ.
I question this ruling.  How would you rule in this situation?

Rule 18.3 has language that seems ambiguous.
If two boats were approaching a mark on opposite tacks and one of them changes tack is it possible for a boat to enter the zone on port, tack onto starboard, and still be considered to be approaching the mark on starboard?

If you tack in the zone from port to starboard is your tack considered part of the rounding procedure and therefore you are approaching from port, or as soon as you tack are you then approaching the mark from starboard?

Is there a definition of approaching the mark?

Is it ever possible to be on port and approaching the mark from starboard; or on starboard and approaching the mark from port?

APPROACH is not in the definitions so I am not 100 percent sure about rule 18.3. Also if a boat enters a windward mark and 18.2 is in effect is it possible for 18.3 to come into effect at that same mark without that boat leaving the zone?

Thank you in advance for either trying to answer my questions and/or directing me to where I can get the question answered.


Dear Brad,

I'll try to give you my opinion as best as I know, but your questions are all, so to speak "to the heart of the matter". The logic of rule 18 is sometimes hard to find.

Lets begin with some ground principles:
Boats are approaching a mark until they have reached it. In my opinion that is when they are AT the mark. There is no definition about this, but I have yet to find a situation that needed one.

Rule 18.2 is off, when they are on opposite tacks on a beat to windward to a windward mark... even if one of the boats is in the zone, or is at the mark and the other still approaching, or even both boats are in the zone.
In the situation you describe, the leading boat enters the zone clear ahead and besides being right of way boat, also gets mark room from that moment. None of the exceptions in rule 18.1 apply - both boats still have to tack to round the mark - so rule 18.2(b) is in effect.

As soon as boat A passes head to wind - rule 18.2(b) is switched off - she's now keep clear boat under rule 13 until she's on a new close hailed course, then she again becomes right of way boat under 10 (starboard) and has a restriction under 15.

You can have a look at Case 88, which deals with this – although the boats are on starboard tack, the principle applies.

Rule 18.3 is not activated, because boat A, after being subject to rule 13 in the zone, is now on an opposite tack then boat B. The first sentence of rule 18 does not 'fit'

Then boat B also passes head to wind. As soon as she does that, she's on the same tack as boat A (starboard) but still keep clear boat under 13. Rule 18.3 is now (also) active. They were approaching on a different tack and one of them changes tack (now both boats are on the same tack) ... The first sentence of rule 18.3 'fits'

Boat B may not cause boat A above close hailed to have to avoid her or etc... Rule 18.3 burdens the boat with a couple of extra obligations because she tacks within the zone. In your scenario we need to find as fact if boat A had to go above close hauled to avoid her or not. Otherwise we cannot conclude that B broke rule 18.3

In the zone, when boats are on different tack and one of them passes head to wind - rule 18.3 must be considered. Regardless of what happens before or regardless of the distance to the mark.

Rule 18 is written to clear inside - outside roundings. As soon as there is tacking involved the rule gets a lot more complicated.

The factor that further complicates things, is the exception that is written in the definition of mark room.
ONLY IF a set of special circumstances are met, the inside boat gets "something extra", she gets the room to tack. Only if she's inside boat entitled to mark room AND is overlapped to windward of a boat that has to give mark room, she's is entitled to room to tack.

Rule 18.2(b) normally is switched off as soon as the boat entitled to mark room passes head to wind, but only in these circumstances it still 'lingers' on.

On a side note: I had a very hard time – actually I couldn’t – draw your situation with any kind of consistency in boat speed. Also I have doubts about the distance of 60 feet. That would place boat A outside the zone (again) when she first tacked from port to starboard.

Perhaps you or someone else can do it. If so please send me an Email with the diagram.

I hope this answers your questions,



  1. Here is a youtube link I made. At least two witnesses said this is nearly what happened. Notice the boats are 2 boat lenths apart approaching on port. There was no contact between boats between position 5 and 6.

  2. This makes it a lot clearer. I tried to make a drawing with the leading boat entering the zone first.

    With this diagram you can all but forget the final tack by B and subsequent luff by A as relevant for rule 18.3

  3. I am glad that the video made it more clear. Thank goodness for Boat Scenario. It makes up for my poor attempt at detailed writting.

    I do not understand your last comment "With this diagram you can all but forget the final tack by B and subsequent luff by A as relevant for rule 18.3"

    Does this mean that B broke rule 18.3?
    Thank you for clarifying.

  4. I am but a mere “Judge in Training” but these rules scenarios give me an opportunity and practice to see if I have any idea on how to interpret and apply the rules.

    Your scenario is a bit confusing because you say both blue and yellow entered the zone on port and the you tube video shows blue entering on port and yellow probably entering on Starboard.

    But first lets go by the you tube video and find fact that yellow entered on starboard and blue entered the zone on port, clear astern of yellow at position 3.

    Initially 18 applies when blue and yellow are both on port tack. But when Yellow tacks to starboard (she has passed head to wind) rule 18 does not apply per 18.1(a) or (b) (not sure which) When blue tacks to starboard 18.3 is turned on and blue is subject to 18.3(a) and so blue would break 18.3(a) if facts are found that yellow had to sail above her proper course. Which seems to look like the case in the video. Also in the video, it looks like blue has not broken 13 or 15.

    Suppose that yellow and blue both enter the zone on port with yellow to leeward and blue the inside boat and overlapped with yellow.

    Now 18 does apply and specifically 18.2(b) kicks in and blue is entitled to mark room. However, 18.3 does not apply because the boats are now approaching the mark on the same tack. If yellow tacks to starboard first blue is still entitled to mark room but is also required to comply with the Part 2 Section A and B rules when taking the mark room she is entitled to. But, if she breaks any of those rules she has the possibility for exoneration under 18.5.

    And with the change to rule 18.2(c) 18.2 is turned off when blue tacks. But then, 18.3(b) applies to blue, as well as the rules of Part 2 Section A and B applying to both boats.


  5. Here's my analysis based on your diagram.

    Rule 18 begins to apply @3-delta when B first reaches the zone.

    @4-2xdelta A passes head to wind (HTW), boats are no longer on the same tack and rule 18 (in its entirity is OFF, rule 13, then rules 10 and 15 apply.

    @4-delta, A reaches close hauled, rule 10 applies, B has enough room to keep clear so rule 15 is not a problem.

    @5-delta, B passes HTW, both boats are now on same tack, Rule 18 comes ON, A is fetching, so, specifically, rule 18.3 is ON, Rule 13 is ON.

    @5 B reaches close hauled, Rule 18.3 remains ON, rule 12 and rule 15 are ON.

    Apparently there was no question that B reached close hauled before A needed to take avoiding action, therefore B did not break rule 13. There is no lack of room for A to keep clear so B did not break rule 15.

    @6 A changes course to keep clear of B. It will be a question of fact, decided on the evidence whether A sailed above close hauled, and whether this was caused by B.

    The narrative says A was 'reaching slightly'. That is not necessarily inconsistent with having to sail above close hauled: A could have been 'reacing slightly' and still needed to 'head up a lot' to keep clear of B.

    To look at some of the questions.

    If two boats are approaching a mark on opposite tacks and one tacks they are than approaching the mark on the same tack. If one of them tacks once more, then they are again approaching the mark on opposite tacks. This does not affect whether rule 18, in particular rule 18 applies or not: rule 18 switches off and on as each boat passes HTW. The first sentance of rule 18.3 "If two boats _were_ approaching a mark on opposite tacks ...", refers to a condition immediately before rule 18 switches on.

    It is irrelevant whether a tack is 'part of the rounding procedure'. Where Rule 18 applied between boats on the same tack, it switches off when a boat passes HTW so as to satisfy the conditions of rule 18.1(a) or (b).

    Why would you need a definition of the simple english word 'approach' in the rules? RRS Introduction - Terminology tells us "words and terms [not defined in the RRS] are used in the sense ordinarilyunderstood in nautical or general use".

    "Is it ever possible to be on port and approaching the mark from starboard; or on starboard and approaching the mark from port?"

    Sort of depends which direction you are looking from. But why do you ask: nothing in the rules depends on whether you are approaching a mark from port or from starboard.

    "if a boat enters a windward mark and 18.2 is in effect is it possible for 18.3 to come into effect at that same mark without that boat leaving the zone?"

    Yes, but rule 18 would probably have to switch off and on in the zone by means other than the entitled boat leaving it. Consider two boats overlapped, L leading, but with W on or above the stbd tack layline for a port rounding mark. L tacks towards the layline (rule 18 OFF when she passes HTW), then tacks back immediately below W: rule 18 ON when she passes HTW, they were approaching on opposite tacks, she is subject to rule 13 in the zone: rule 18.3 applies, but now to the advantage of W.

  6. Based on the diagram there was no foul. If 'A' had been forced to sail above close hauled to keep clear then 'B' would have broken 18.3. However, it appeared from the diagram 'A' over-stood the mark and that she only sailed up to close hauled not above. Also, if 'A' had chosen to duck below 'B' and obtain a late overlap then 'B' would owe 'A' mark room. This assumes that this is fleet racing and not a match race with the changes to 18.3 in Appendix C.

  7. Speaking of sailboat racers and marks, on my blog (Desert Sea on blogspot) I have tried to address the common mis-conception or confusion about navigation marks, which came up recently as a Sailing Anarchy question / debate.

  8. my opinion re "all but forget" as per the diagram:
    1. rule 18 only kicks in when B-blue passes head to wind as is subject to 13 in the zone while a-yellow is fetching the mark. when B enters the zone she is clear astern so no part of 18 applies. when A enters the zone they are on opposite tacks so again 18 does not apply.
    I think that is what Jos meant - "you can forget all but..."
    2. the question is if A-yellow HAD to luff up. If she HAD to do so to avoid B, then B broke 13.
    if not, then A could have to continued sailing her course clear astern of B and still fetched the mark.

  9. This rule used to be simple. It said, in effect, that you couldn't tack from port to starboard inside the circle if doing so would force a starboard-tack boat to alter course. Adding "above close-hauled" made the situation more ambiguous, which encouraged more port-tackers to take their chances. Why did the rule-writers make this change, and why don't they change it back?

  10. I think this is a classic 18.3 situation. The animation shows that A completed her tack before B was obligated to alter course. Note that Rule 18 applied before A tacked because B was in the zone, but did not apply when A and B were on opposite tacks. But after A tacked, she was fetching the mark (e.g., steering a course to pass the mark on the required side without tacking again), and when B tacked, she was subject to Rule 18.3. The dispute will be whether A complied with Rules 13 and 15 when she tacked, and whether or not A sailed above close-hauled after B tacked. I think the animation shows that A was on a close hauled heading before B was obligated to alter course, and A did sail above a close-hauled course. If A can establish that to the judges' satisfaction, B will lose the protest.

    Although there is no presumption that A sailed above close-hauled, in a protest this situation is usually a losing proposition for B.

    The reason for the modification from the previous rule was that in the opinion of the rule-makers, the old rule gave too much power to the boat already on the layline.


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