Friday, 19 February 2010

AC 33 | Rules and explanations – part 4

There have been a lot of comments on the match winning move of USA-17 in the second match. The tactician on the boat (John Kostecki) called a perfect lay-line according to helmsman (James Spithill) and that, together with his skill as match racer, cumulated in USA being able to round the mark first. Lets have a look at the rules involved in this situation and what SUI could have done. Or could she?

In the drawings SUI is the yellow boat and USA the blue boat. I regret I cannot draw a trimaran, but as both boats are almost the same dimension, it should be more or less to scale, nevertheless.

This is what happened (as far as I can reconstruct from videos):
Picture: AC33 SUI-USA M2 Layline Cross.png
GIF- Animation: AC33 SUI-USA M2 Layline Cross.gif
Boat Scenario file: AC33 SUI-USA M2 Layline Cross.xbs

Position one
SUI to windward and a little in front; USA to leeward approaching on the lay-line.
SUI is keep clear boat either under rule 12 or 11

Position two to three
USA tacks from Starboard to Port a couple of boat lengths above the lay line. SUI continues.
USA is now keep clear boat under rule 10

Position three to four
Boats are four or five lengths apart. SUI is crossing USA.
USA bears away slightly to gain speed and to discourage SUI to go for a dial-down.
USA is still keep clear boat but SUI must give her room to do this IF she changes course, which she does not.

Position four
SUI has crossed in front of USA and starts to luff to go into a tack above the lay-line
USA has full speed and keeps clear.

Position five
While SUI is slowing in her tack, USA passes to leeward of her and luffs to her higher course to fetch the mark.USA becomes right of way boat initially by SUI tacking (rule 13) then as leeward boat (rule 11) en then as clear ahead boat (rule 12)

Position six, seven to eight (a little later)
SUI has completed her tack and is gaining speed. She's slightly to windward but clear astern of USA
USA gained five or six boat lengths in the stretch to the mark and enters the (4 hull-lengths) zone clear ahead of SUI. She's now not only right of way boat but also entitled to mark-room

What could SUI have done to prevent USA from gaining the upper hand?

Put yourself on the big Alinghi 5 Catamaran and convince Brad Butterworth and Ernesto Bertarelli what to do:

Option 1:
Between position two and three you could have gone for a dail-down. A risky move, because by changing course you are subject to rule 16 and have to give USA room to keep clear, but perhaps it can be done.
You have to set this up, knowing boat-speed and manoeuvrability of the other boat as well as your own. Since this was only the second time these boats raced (against each-other), I would not blame you if you have serious doubts about having that knowledge.
Best outcome of this move would be, to be able to force USA back into a tack. Then you would be able to sail on to a position where you wanted and tack first to go to the mark.

But even if the second best thing happened - that is USA being able to bear away quickly enough to keep clear of you - there would have been a big chance that USA could no longer fetch the mark. As soon as the cross was done, go into a tack and gain the upper windward position (making sure you fetch the mark yourself.). If USA must tack again (and again) to round the mark you will be long gone and in front.
If USA is able to fetch the mark, you are no worse off. You needed to give him mark-room and now you will have to do that also. At least you are still close by.
Picture: AC33 SUI-USA M2 Layline Cross Dial down.png
GIF- Animation: AC33 SUI-USA M2 Layline Cross Dial down.gif
Boat Scenario file: AC33 SUI-USA M2 Layline Cross Dail down.xbs

Option 2:
Tack below USA.
You want to try to get a lee-bow position. There are two drawbacks: Tacking that low would mean that you do it barely on the lay-line, perhaps you are even not yet on the lay-line. With that shifty wind and still 2 miles to go, you might not fetch the mark. And secondly there's a big chance that USA - with her superior speed - simply would pass to windward and roll you.

Picture: AC33 SUI-USA M2 Layline Cross Lee-bow.png
GIF- Animation: AC33 SUI-USA M2 Layline Cross Lee-bow.gif
Boat Scenario file: AC33 SUI-USA M2 Layline Cross Lee-bow.xbs

Option 3:
To tack in front of USA. Now this move is even more riskier. The distance between the boats and the fact that - like in all cats - tacking takes an eFFing long time, would make it highly likely that while your are tacking (and are keep clear boat under rule 13) USA would have to take avoiding action. And even if you manage to complete your tack - i.e. turn your catamaran on a new close hauled course - then rule 15 would kick in and you would have to give USA initially room to keep clear. No doubt a Yankee flag from USA would follow and for you a great risk of getting penalized. That would make this a match-losing move. Another penalty on top of the one you already had, equals loosing the match (bar acts of God)
Picture: AC33 SUI-USA M2 Layline Cross Front tack.png
GIF- Animation: AC33 SUI-USA M2 Layline Cross Front tack.gif
Boat Scenario file: AC33 SUI-USA M2 Layline Cross Front tack.xbs

You can be sure that all these three options have been anticipated by USA-17. JS&TK will take advantage of every possibility that you open up for them.

You choose, there's no more time.
USA is luffing to tack.....

Next time in AC 33 | Rules and explanations, reflections on the rules for Race Committees, Organizing Authority and Interested Parties. Or was it about the Bounty?

Stay tuned.


  1. I would have gone for the dial-down.

    Ernesto, if you want me as skipper for AC34 please email me at tillermeister at gmail dot com.

  2. @ Tillerman
    I sort of got the impression that was exactly what James Spithill was expecting A5 to do, in one of the interviews. One of the reasons USA bore off a little, to force SUI to go lower then they might perhaps wanted to do. That and closing speed...
    I think you have a better chance perhaps asking your neighbour Larry E?

  3. Team BO already has a winning skipper. Team A does too, but he did not get to steer the boat!

  4. Jos,

    After having watched the video repeatedly, I came to the same conclusion that Tillerman did - Dial Down and take your chances if you're SUI. Every other option results in loosing the race, at least with a Dial Down there is some (although small) chance of success.

    Of course we all now know how much faster USA is on a reach than SUI, so with perfect hindsight we realize that almost nothing could have defended SUI against a boat that is 12.5% faster on the first reaching leg! Yikes!

    All that said, it is always better to take a chance which allows you to win, vs sailing in a way that guarantees that you loose. This was, after all, the second race in a best of 3 with SUI down one, so there was absolutely everything at stake with the maneuver. With SUI knowing that USA was faster, from the first race, there was nothing they could count on other than to force a tactical battle.

    Then, they chose not to engage.

    I find that very very odd, and from what I saw of the interviews with the crew of USA, they found it odd too. Perhaps SUI was hoping USA would break - there are some stories that USA had convinced SUI that their boat was far weaker than it actually is. But that is an extremely risky strategy to employ, particularly against a boat that has vastly more hours on the ocean under her keel than you do.

    Dial Down for the win or go home would be my recommendation, you're going home anyway if you don't win.


  5. The truth of matter is both boats took the only approach they could. USA has noticeably better pointing ability (as proven in the first race) than SUI which enabled her to tack inside SUI. If you look carefully at the USA approach to the weather mark you will note that she steered a little high of the mark (at least one or two widths of the boat) and came down to the mark in the last three hundred feet as a good tactician should.

    Contrary to the babbling announcer, it should be very clear that although SUI was closer to the mark on the starboard tack before the tack to the layline, USA was further up course (ahead) and when she tacked over on her layline and ducked SUI’s stern both boats were in essence very close in terms of actual distance to the mark. That means that SUI wasn’t really that far ahead on the starboard tack before tacking onto the layline. The announcers for the last three or four America’s Cup races have been terrible. They don’t really understand sailboat racing, the rules, or the tactics.

  6. Option 4: Alinghi holds her course but starts dumping her sails and slows down right in front of USA forcing a (crash) tack.

    1. Yes Dennis, your option four is a very good one. Because reducing speed does not have a limitation rule (like changing course has limitation rule 16.1) it would have been completely protected by rule 10. The problem is however that if the timing is even a little bit off, USA would have just gone downwind a little more and passed behind, gaining speed. Then SUI has to tack with even less initial speed and that would have cost her seconds in the tack.

      SUI must make sure that she slowed down enough to close the door behind and not so much that she couldn’t catch a luffing USA in front.
      Only a skilled match racer – like Loick - would have had the skill to do this. I’m not sure Bertarelli has enough MR experience to pull it off, but I could be wrong.
      It would have been a great manoeuvre!

      I’m not sure it would have been a winning manoeuvre – considering the superior reaching speed of USA. But it would have been at least exciting to watch.


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