RRS 21.3 states that a boat moving sideways through the water shall keep clear of one that is not. This maneuver, often called crabbing, is very common at high levels of ILCA racing, and sailors are coached on how to do it. (See this video:
https://www.youtube.com/watch?v=avH7S9ayFrI)
But what if two boats are crabbing, i.e., moving sideways through the water. This is very common on the starting lines of major ILCA regattas.
In those situations, my guess is that Rules 10-13 come into play; specifically, Rules 10-12 if the boats don't cross
head to wind, and Rule 13 if they do.
But here's here's the rub: is "head to wind" based on
true wind direction (the wind a boat sees when luffing, net of current) or the
apparent wind direction? This matters because crabbing is most often done in light air, and moving sideways adds an apparent wind vector that pulls a boat's wind direction 10-20 degrees to the right (assuming they're starting their crab on a starboard close-hauled course and push their boom to the port side).
Here's the edge case that is especially challenging: both crabbing boats are pointed 10 degrees right of true wind, but are 10 degrees left of apparent wind. (This comes up all the time as boats attempt to increase their hole to leeward, while reducing the hole of the boat to windward of them.) If head-to-wind is based on true wind direction, the boat on the right is right of way per Rule 13; if apparent wind, the boat on the left is right of way per Rule 11. The HTW definition switches the right-of-way boats.
Thanks in advance for your clarification.
It is extremely interesting to watch the video Al has provided. Do take a look while thinking about Al's question.
I have no doubt that he'd get a yellow flag from me. My only doubt is which breach I'd write down in my notebook.
The head to wind question: the phrase apparent wind does not occur in the rules. the phrase true wind appears in the clear astern/ahead definition and a number of appendices. None of the occurences involve head to wind. I suppose one could interpret it two ways, one being that if true wind must be specified in specific rules then it must otherwise mean apparent wind, and the other that apparent wind isn't a concept in RRS so may never be meant.
Seems to me that its probably best to apply last point of certainty. If its unclear whether a boat changed tack then she did not. In the video he does in fact pass head to wind, and then sculls forcefully back.
A defence, I suppose, for the windward of two boats crabbing, is to stop crabbing, at which point leeward must keep clear. However I suppose if windward stops crabbing then RRS 15 applies. Its a bit of a mess isn't it?
The matters to consider are, principally, the boom push has no associated sculling so it is not in breach of the interpretations.
On the rock, if it propels the boat it is always a breach, we cannot usualy see this, so it does not get penalised.
As to the roll, i think there were at separate times, so not linked, so i go back to whether you are sure it propelled the boat if so penalise
The above depends on where you are viewing from, if behind, you cannot be sure, if alongside, then you can be sure.
Can be ok therfore, but always a risk of a penalty.
On true or apoarant wind.
Not easy and a contradictory answer.
I go for apparant wind caused by outside factors affecting all boats such as tide.
Wind generated by the boat does not count as it compromises wjen to an outside observer you are such as tacking.
(1) body movement
Repeated means more than one in the same area on a leg, this definition is found in the Interpretations of Rule 42. I sent a question to the US Sailing Appeals Committee concerning "the same area on a leg":
Question 2
If a boat behind the starting line rocks once 5 seconds after prep down and then rocks again 2 seconds before go, is that repeated?
Answer 2
Your questions reveal an issue with the WS Interpretations of Rule 42, Propulsion definition of the term “repeated” in that it is only relevant when a boat is on a leg. That definition does not address boats in the starting area before or shortly after their starting signal.
We will be informing the WS Rule 14 Working Group of this situation. With regards to boats in the starting area before their starting signal and shortly after they have started, until such time that World Sailing updates its Interpretations of Rule 42, Propulsion, we think it is typical and reasonable that Appendix P observers, umpires and judges interpret the term “repeated” in rule 42.2 to mean the action was performed more than once in the same area of the starting area in a relatively short period of time. It will be up to the observers, umpires or judges to determine if an action has been “repeated,” based on the type of boats, the wind and wave conditions, and what the actions of the boats were.
If I observed the the actions of the boat in the video during the pre-start while the boats were racing, I would penalize the boat for rocking, 42.2(b)(1).
I have often observed boats making violent movements with the rudder to both cause the boat to accelerate and also turn the boat. This is often combined by a move similar to the final body movement of a roll tack. (EG: bow-down to a reach, start rapidly sculling to start turning to windward (tiller not crossing the centerline), body to leeward, then once the boat has turned to just before head to wind, a violent body movement to windward combined with a single extended pull of the tiller to windward.) Perhaps my understanding of "sculling" is out of date or mistaken, I thought that if the repeated motion of the tiller didn't cross the centerline it was consider a way to change course and allowed.
Then is there a pause while the boat moves forward and the process is repeated approximately every 5-10 seconds.
And in an attempt to respond to Al's question, I'm pretty confident most judges are using a combination of apparent and actual wind direction. At the time of the incident, most judges are watching the sail. If the boat is moving at 5 knots and goes head to wind, they are head to wind in the apparent. But when they stop, head to wind is going to be actual. Compass course would be very difficult for a judge to try to use. Thus, 13 is only at play when the judge is confident the main is laying on the starboard side. If the competitor is holding the main, there are dozens of other boats not holding their sails that the judge can use for comparison. This video doesn't provide the kind of feedback that a judge sees on a real start line.
The sailor does change course, but the change of course is not linked to wave patterns - "ROCK 7 Repeated rolling not linked to wave patterns is rocking prohibited by rule 42.2(b), even if the boat changes course with each roll."
I cannot find a rule or interpretation that states "Repeated rocking not linked to waves or steering is prohibited." Rather, Rock 7 tells us that repeated rolling not linked to wave patterns is rocking prohibited by Rule 42.2(b), even if the boat changes course with each roll.
The sailor in the video breaks rule 42.2(b), Rock 7.
I also have some issues with what he is saying as far as the rules go. At 2:23 of the video, he says that if you don't go beyond head to wind you don't 'surrender your leeward rights'. This is simply not true. If you are moving astern or sideways to windward as a result of backing a sail (and it doesn't have to be backed at the time, just that you are going backwards/sideways because you backed your sail), you are required by RRS 21.3 to keep clear of other boats that are not. Once you start going backwards RRS 15 will not apply to any of the other boats and you are in a high risk position as a windward boat doesn't have to keep clear of you, a boat to leeward could tack right in front of you, or a boat from clear astern can establish an overlap to leeward as close as they wish as none of them are going backwards or sideways. Then once you start going forward again you will have a RRS 15 obligation, so even a tacking boat gets room to keep clear.
A windward boat could simply bear off into the space that he is leaving as he goes backwards and then prevent him from going forwards and turning up as he has a RRS 15 obligation.
Overall, this could be a very risky move on a crowded starting line.
With respect to: "As far as the rocking goes, I actually think that he breaks the basic rule when he flattens the boat as he is going faster than he would have otherwise. This is BASIC 4/ROCK 6."
Wouldn't this logic also result in a boat executing a roll tack breaking a Rule? The boat executing a good roll tack certainly leaves the tack going faster than they came in when sailing in light winds. I question using exit speed as the criteria.
I agree that once a boat is going sideways or backwards it has lost its rights accrued by being "leeward boat". My observations on the water are that the crabbing boat will quickly accelerate forward to maintain rights over the windward boat. Of course, they have to provide time for windward to keep clear, which they often do. In my experience, the high level ILCA fleet in particular is quite accomplished at this high-risk dance of acquiring-losing-acquiring these rights.
In light air ..boats are putting along at 3kts and comes out of roll/tacking at 5kts .. then slows back to 3kts ... that's propelling the boat.
In the video, it appears to me (with MUCH less experience than all of you with ILCA's) .. this move seems to clearly propel the boat beyond just flattening and accelerating to my eyes.
1) Wikipedia repeatedly references "true wind" in their entry on Point of Sail: https://en.wikipedia.org/wiki/Point_of_sail#No-go_zone
2) when foiling boats are going downwind and their apparent wind angle is a near reach, we do not describe them as near-reaching, nor as being on a beat to windward. If they briefly point directly downwind, and their sails luff from the bow due to the apparent wind, we would never suggest they were head-to-wind.
Worth noting the video is 5 years old. The author's rule analysis might be different under current guidelines .
I read that differently - 21.3 A boat moving ... or sideways to windward, through the water by backing a sail shall keep clear of one that is not. So must be moving sideways AND to windward for me to see it as keep clear boat.
On the rolling/RRS42 - I'm with Paul Z. on his note above - A boat may be rolled to facilitate steering. Clearly, it needs to be proportional, etc. etc. but what I saw in that video would not give me cause for concern in an ILCA fleet. Is the acceleration due to the flattening effect or natural acceleration & sheeting on through the luff up to weather? In other words - does it clearly propel the boat? Hard to see without a comparative boat not doing the same action without the rock.
I see no sculling to offset - there is a clear astern movement with steerage - so no yellow from me there either. In fact the tiller is steadier than most ILCA sailors on a start line.
I would also argue it is not possible to determine from footage whether the ILCA goes past head to wind at any stage - the boom is clearly over the corner of the cockpit rather than centreline so any backwinding is not indicative of HTW for me.
Differing viewpoints is one reason why we observe in pairs, and rarely from the perspective of this camera angle at the start.... !
Angelo, you are correct on the 42, but the problem for the judge generally behind the boat is he cannot see the boat accelerate or decelerate. He cannot penalise as he cannot be sure.
A judge can, however, count so if he sees a second rock (now a roll) he can penalise.
Yes, if done correctly a roll tack can accelerate a boat substantially, but that kinetic seems to be acceptable in general practice if not linked to another immediate roll tack.
I was trying (and not succeeding) in asking: Using the roll tack example, is it "ok" to do one crab? Is the foul when a competitor does multiple linked crabs?
When watching ILCAs from the signal boat, there are lots (sometimes all) of the boats performing various maneuvers constantly for the last 20 seconds before the start. Bows are going up and down, sails are going in and out, and body weight is being moved inboard and out. None of that looks like crabbing to me. It's only when I see a boat backing its mainsail and skulling to get the bow down that I think it's a crab, and only when it's repeated do I think the boat is crabbing, similar to repeated and linked roll tacks. (All this said with the proviso that Rule 42 is not my strong suit as I'm more of a Race Officer vs Umpire.)
Call it just a conservation-of-energy analysis instinct .. I'd have to break it down to each dynamic segment to see if I'm missing something.