There's been a new spate of discussion about when, in the definition of mark-room, a boat is "sailing to the mark" and when she's "at the mark".  Unlike the earlier discussion of this topic when the new rules first came out, most of this recent discussion comes out of match racing.  In that discipline, in many races there are more umpires than skippers and tacticians combined, to decide when precise transition points have been reached; and for consistency of calls, everybody wants the umps to have as little latitude of interpretation as possible.  Of course, in fleet and team racing, which do not have such resources, such precision is impossible to achieve; but it still might be helpful to try to define what is meant.

I've argued before in the UK-Halsey blogsite that the distinction between the rights of a boat "sailing to the mark" and "at the mark" is not important for the purpose of rule 18.2, Giving Mark Room, because when a boat is nearly at a mark, her course "to the mark" and her proper course around it are essentially the same, so the exact moment when she ceases to be sailing to the mark and is now at the mark is irrelevant.  But there's a related issue, where the distinction might be important:  Rule 18.5 says,

"When a boat is taking mark-room to which she is entitled, she shall be exonerated

(a) if, as a result of the other boat failing to give her mark-room, she breaks a rule of Section A, or

(b) if, by rounding the mark on her proper course, she breaks a rule of Section A or rule 15 or 16."

The rules of Section A deal with keeping clear, so both parts of the rule exonerate a boat for failing to keep clear if she's simply taking mark-room to which she's entitled, and the other boat gets in her way; this makes sense, as the other boat wasn't supposed to do that.

Rules 15 and 16 are a different matter.  Rule 15 requires a boat that gains right of way by her own actions to initially give the other boat room to keep clear, and rule 16 requires a right-of-way boat that changes course to give the other boat room to keep clear.  Exonerating a right-of-way boat from breaking these rules puts a mighty weapon in her hand.  She can now carry out actions against the boat that owes her mark-room, which she could not do anywhere else on the racecourse.

The opportunity to take such aggressive actions without penalty is, of course, the grist of the match racing mill, so naturally match racers and umpires want to know exactly when a boat is "rounding the mark"; seeing that this is in some way related to "at the mark", they want to know if"rounding the mark" in rule 18.5 is the same as the transition in the definition of mark-room from "sailing to the mark" to "at the mark".

My answer is "Being at the mark is related, but not identical, to rounding it." To see why I say they're related, consider the situation at a port-rounding leeward mark, where the inside boat (S) is on starboard tack, with right of way over the port-tack boat (P) outside her.  Suppose S is just entering the zone and she's not at that moment sailing toward the mark.  If she turns to her course to the mark in such a way that P cannot keep clear, she breaks rule 16. Does she get exonerated for that breach?  I think we'd all say, no, she didn't change course "by rounding the mark", she did it while sailing to the mark.  So she would get exonerated if she broke a rule of Section A (which she can't do, she's the right-of-way boat) but not for breaking rules 15 or, as in this case, 16.

On the other hand, suppose S has sailed to the mark and, for whatever reason (maybe there's a current she misestimated) she ends up aiming at the wrong side of the mark and needs to turn to starboard at the last second, to get to the correct side of the mark.  She has right of way, so she doesn't need her mark-room to turn to pass on the right side of the mark; but if she turns so fast that she fails to give the other boat room to keep clear, ordinarily she'd run afoul of rule 16.  In this case, however, I think such a turn is exonerated by rule 18.5.  She broke rule 16 "by rounding the mark".  In effect, her right to exoneration is the same as under the 2005-2008 RRS.

Note that the turn of the boat at the edge of the zone might have pretty much the same radius at that of the boat at the mark – the difference is that at the mark she turns sharply by rounding the mark, whereas at the edge of the zone she's turning sharply to sail to the mark, and that's not an exonerated action.

So "at the mark" and "by rounding the mark" are not synonymous, but they're related by the fact that a boat boat cannot be rounding the mark when she's still sailing to it, only when she's at it. (On the other hand, even if she's at the mark, a sharp turn that's not to round the mark would still get her into trouble if she breaks rule 16 when she does it.)

This gets us back to the question of when a boat is at a mark.  Unfortunately, it turns out to be difficult to define the moment of arrival "at the mark" precisely (which is why the rule-writers didn't put a more precise definition into the rules).  For example, we might be tempted to say that a boat is "at the mark" when the mark is alongside her, i.e., the mark is abeam of some part of her hull and equipment in normal position.  But that clearly doesn't work – consider a boat like the one in the scenario above, which arrives at the mark with the mark directly in front of her.  Surely if she's only inches from the mark she's "at" it in any reasonable sense of the word; yet she's not alongside the mark.  Conversely, a boat approaching the mark might turn away from the mark so that the mark is abeam of her bow, but if she's two of her lengths from the mark with nothing but water between her and it, she's surely not "at" the mark in any reasonable sense. 

Another approach to defining "at the mark", which I think I like, is to look at the boat's proper course.  If a boat's proper course is to sail toward the mark in preparation for rounding it (taking into consideration other boats she needs to give mark-room to or keep clear of), then she's sailing "to the mark"; if her proper course is to turn to round the mark (even if that turn is counter to the direction to the next mark, and even if she's some distance from the mark), she's "at" it.  And, if she does turn to round it while taking mark-room to which she's entitled and she thus breaks rule 15 or 16, she's exonerated for doing so.

And that, I'm afraid, is the best we can do for the match racers.

Posted on: 5/30/2009 at 5:20 PM
Tags: at the mark, rounding, mark-room, exoneration
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