Friday, 19 February 2010
AC 33 | Rules and explanations – part 4
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):
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
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.
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.
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:
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.
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
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
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)
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?