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America's Cup: Two feet

by John Curnow, Editor, Sail-World AUS 28 Mar 2021 14:00 PDT
America's Cup match day 1 - Luna Rossa Prada Pirelli luff Emirates Team New Zealand soon after the start of race 1 © YachtBot / ACE

It can be a unit of measurement. Also the very extremities you use for balance when standing up. Then on March 5 this year, we saw that they can even belong to an avatar assisting you and your cause via reinforcement learning in the most recent iteration of the America's Cup.

Speaking of binary, and out on the racetrack for Race One we saw digital power at the fore when the umpires could physically see the couple of feet involved in a major luffing manoeuvre soon after the start. This is of course where our hero graphic came from.

Indeed listening to people who have actually won the Auld Mug before highlights many things, most particularly that the fastest boat always wins. Yet it is in behind that, that there are some gems about what it takes to be that fastest boat, from crew to design, sails to mindset. Often it can be mere centimetres, or in the case of the games of the mind, complete paradigm shifts.

One word that does seem to be omnipresent, however, is relentless: striving for the goal, pursuit of performance gains, opening a new realm. To that end, I have not heard one of those winners express anything but remorse at the notion of a Deed of Gift match reappearing once more. "If you want to race it on your own home waters, first you have to win it!" seems to be the resounding cry...

Now some of our most popular stories of late have looked at these and even more subjects, for no matter what anybody says, people tune into the Cup, and AC36 drew in more non-sailing souls than many a match preceding it. Indeed, watching our Managing Editor, Mark Jardine, on the BBC explaining how racing AC75s on a tight course is akin to F1 cars at Monaco, speaks volumes about the tractability of sailing in the modern sports world. Going back to 12s? Forget it. Ain't going to happen...

Reason being, thankfully the Defenders have said the AC75 will be the weapon of choice, and stability in this regard is good for the Cup. The next, is that as in Pushing the boundaries, the vessels have already morphed significantly from the 'weird looking' insects that appeared but a few years ago. Borrowing a Beneteau nickname for their Sense line (not the description thereof), they are now a monomaran - two distinct pods or nacelles with a flat trampoline holding them together. We've seen other iterations of this notion in Comanche and the Syra 18.

Alas we were promised sail changes and crew work, but the fact that the Code Zeros remained in their bags when they were becalmed put paid to all that. Bet there are a few for sale now for large racing and even cruising yachts...

Yet it was Mark's reference to Homer's Wonder Bat that pretty much had me going straight off to keels of unobtanium. No doubt this was a direct result of a far reaching conversation with Iain Murray AM, and the 1987 defence of the America's Cup off Fremantle, of which we had the first instalment in Sliding Doors. Indeed that answered a lot of things, but there is more, and for that I am truly indebted to Iain, who has carried this burden forward with great distinction for his nation, and very much shown how he is yachting's da Vinci.

Now the keels of the Kookaburras looked a lot like a whale tail, but in reality were described as a delta wing. In that regard, the best reference is really to an F-111 with her wings swept fully back. They were definitely unique, and by all accounts, efficient too.

Murray commented, "It was a really good keel. When the identical one went on Steak'N'Kidney (Aussie rhyming slang for Sydney), she went from nothing to a pretty good boat. We built one for Azzura too. It was a Kookaburra keel that went on them, as it was the Kookaburra boat builders that built the plug for the mould of that keel."

"When the plans went to the pattern makers to build them, they brought them up and said 'this is the same as your keel.' And what was the common source? What was common across all three teams?"

Regarding Kookaburra III herself, Murray said, "If we knew we were going to sail in that much wind, we would have sailed with smaller wings." Yet as we discovered earlier, the real deal was in taking Kookaburra II's LWL out by two whole feet to 47' and LOA to 67', which is what Murray had really wanted to do.

However, a protest was not heard (Murray informed me Kookaburra II had already won most of their protests), a secret contract revealed and upheld, as well as a team patron full of belief in his warriors that all conspired to make a proper defence unachievable. "Doesn't matter. We'll just come and beat you next week," was how Murray relived the late Kevin Parry's words.

Now who could forget Dennis Conner having to face the press on his own, but later the crafty skipper would train his Stars & Stripes crew in relatively obscurity in Hawaii before heading to Perth. "Dennis just made it into the Challenger semi finals, and it was then that he made changes to the wings, displacement, and riblets on the boat. In the windier conditions he got to light speed, up from just making it there. It was obvious that the Kiwis were a class act, but he toppled them to make the final. Dennis was on a charge in the longer and heavier boat."

Star & Stripes 87 did not sail well in the light, as seen a year later in Sardinia, where he even sailed her four up to try and reduce weight. Murray explains, "Typically a 12m has a prismatic coefficient of .55, but Star & Stripes had .61, due to her really full stern. They were pressed up against the wave drag of the boat, but needed a lot of wind both up and downhill." Hello Fremantle Doctor. Remember too that the US boat had a heavy displacement and reduced sail area to account for her 'huge' LWL.

The 12m Rule is effectively a series of compromises, and indeed tradeoffs, in terms of length, sail area, overhang, and displacement. For instance, a heavier boat has less sail area than a lighter one - go figure? It is kind of a weird arse box rule, where the box is somewhat amorphic. Don't believe us, have a look at this image of the rule.

As for the prismatic coefficient it's, (Cp) = V/(AxL), where V is the immersed volume of the hull in cubic feet, A is the maximum cross-sectional area in square feet, and L is the waterline length in feet. It also appreciates the fore and aft sections effects on drag and wave generation, and gets into pocket protector level pretty quickly after that. Whereas understanding the 12m rule may require you to actually live the Hangover movie for real... Dangerous stuff.

"As it finished in Fremantle, Dennis was the fastest, then the Kiwis, and we were probably third." How much do you believe a modified KII would have put you in the same league as S&S? "We could not resolve the prismatic coefficient side of things, but I think the extra LWL, and reduction in sail area would have put us into the point where we could have made a race of it."

"The situation was he could just make a timed run at the start, start to leeward of us, go out to the lay line, tack, and cross in front of us. If we could have started to windward and got to the lay line, then he would have entered into a match race with us, and I reckon we were a chance, because we could race the boat well. As it was, we weren't even in the race - that was the problem!"

In addition to the mystery and intrigue associated with the Cup, along with the armada of lawyers usually involved, the dogged, brilliant drive that had brought such glory to Australia was now forced tragically and fruitlessly inward. If they knew, it must have been an awkward, and sad moment for the fine sailors of the opposing Australian (Bond) syndicate, among them Colin Beashel, also one of the heroes of 1983.

If Australia dares once more to back our own and form a dream team from the likes of Glenn Ashby, Jimmy Spithill, Tom Slingsby, and Nathan Outteridge, along with the design and technical expertise for which Australia is well known, perhaps we could shake off the demons of the past to again possess sport's most illustrious and coveted prize. The challenge this time around will be to fight the opposition however, and not ourselves.

Right oh - there is plenty of information on the group's websites for you to review when you can. Please avail yourself of it.

Now if your class or association is generating material, please submit your material. Got this newsletter from a friend? Would you like your own copy next week? Just follow the instructions on our newsletter page. Whilst there, you can also register for other editions, like Powerboat-World.

Finally, many thanks for making Sail-World your go-to choice. We're always here to keep pumping out the news. Stay safe, and have the happiest time possible depending on your level of restrictions.

John Curnow
Editor, Sail-World AUS

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