34th America's Cup: multihulls!

34th AC on Foils!

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Tom is right Stephen: Raves have come with a warning sticker saying "Do not exceed 30 knots". One guy who did broke the massive aluminum crosstube.
Boats that have dual, independent altitude control systems(wands or "feelers") have to be managed carefully near the top end because the foil forces developing all the RM for the boat can break the boat. Hydroptere doesn't use this kind of system , in fact, for added stability, she uses waterballast in the amas!

 

That's interesting and I certainly credit Tom with knowing what he's talking about. But in a way that would just make the challenge more interesting; engineering a fail-safe would become part of the design problem. So I wish the rule makers had left the rule for AC72 racing more open. Alas.

Just for kicks lets speculate: couldn't a foil be designed to stall or cavitate and lose its grip before other things fail? Or could it be mounted with a spring allowing it to lose angle of incidence when a certain load is reached? Or might there be sprung flaps on slots that would dump pressure past a certain point? Perhaps trim tabs could be used in some clever way to achieve the effect? Would it be possible to size sheets to break before anything else does? Or perhaps something releases to depower when the load on the shroud hits a certain value. Perhaps it makes sense to limit healing moment by some aero-mechanical device rather than think in terms of limiting righting moment

 

I like multi-hulls, but AC should've stayed mono and traditional.

Maybe a few rules to keep costs down, and boats big.

Maybe all teams get issued the same traditional building materials and tools a set time prior to race, and can only use that, so aside from human talent costs are pretty fixed and you'd see "tall ships".

Call the multi-hull race something else.

 

No, 72 foot multihulls in the AC is absolutely right; this is THE spectacular, expensive show and historically has always been this way (except for the retrograde 12's and the heavy recent old dogs). RC got it absolutely right; no need to fall back on second thoughts because of a few haters and flat earthers. We've never seen such giant developments before: full wing rigs and foils, (that is barring S&S catamaran and the white Kiwi dinosaur).
Next AC will be wider open, no foil restrictions ... but what we're seeing now?? ... that will suffice for the time being.
Steven, Hydroptere has never had negative attack windward foils; they're set at a positive angle so there is lifting load developed to windward - and not much at that because only the lower tip is immersed; far less, no comparison, drag compared to Rave and co. In fact when gusts hit, Hydroptere lifts windward foil completely clear.

 

Add Russell to the list of haters and flat earthers. He has known for some time this was the wrong direction.

If Larry manages to win this time and keeps the same rule, or keeps the basics of size and type, with "wider open, less restrictions" there will be no Next AC.

 

Huhhh? How do you figure, Paul?

I stand corrected about Hydroptere, except - wouldn't a momentary negative angle of attack be possible if the bow pitched down during a turn to windward? I make this odd point only because unless the AC rule making committee was worried about momentary conditions like this I don't see why they'd adopt the rule requiring the windward foil to be up. But you're probably right that this is unlikely with the straight canted foils on Hydroptere.

 

Historically the AC has generally NOT been much, if at all, more spectacular and expensive than the rest of the mainstream big-boat section of the sport. Throughout much of the big cutter era, for example, the AC boats were roughly the same size as the British "Big Class" cutters; for example, the 1893 challenger Valkyrie II was no bigger than Britannia (slightly smaller in fact) and smaller than the similar-vintage cutters Satanita and Meteor II - and that is completely ignoring the vast schooners. The 1893 AC yachts were no more spectacular and expensive than the larger and similar cutters that did NOT race the AC, such as Satanita or Meteor.

Through the next era, that of the J Class, the AC boats were smaller than the last of the great racing schooners and once more not significantly (if at all) bigger or more spectacular than the rest of the UK Big Class such as the 23 Metres or Britannia.

The 12 Metres were of course smaller and often slower than the big offshore boats of their day as were the IACC boats.

Whatever one may think of the 72' cats, the fact is that AC boats have historically not been significantly more spectacular or expensive than the largest non-AC racing yachts of their time. In fact historically the AC boats have almost always been simply fairly large representatives of mainstream big boat racing and therefore the current boats are going against the stream.

Oh, and abusing those with opposing views does not change the facts.

 

Is this really necessary this argument was going in the http://www.boatdesign.net/forums/sailboats/americas-cup-whats-next-31489.html thread no need to rehash the same arguments here. Apart from anything else the people who have been posting in this thread did not write the protocol so it's no point getting angsty about it maybe you should contact the guys running the AC show if you dont like it. Hopefully then we can have a discussion in the "multihull design forum" about multihull designs and their usage in the Americas Cup?

 

OK, so here's one of the largest non-AC racing yachts of our time. (For more click here.) Your point ...?

 

Without being too picky and pedantic, there are always larger and more expensive design yacht examples around compared to the AC boats ... but the AC is the media apotheosis of yacht racing, the big one, has extensive libraries of expensive reference books written about it, no other class or yacht type comes close ... and most would agree with this.

 

I'm not sure of the relevance of the MOD 70 in this context. If you are trying to say that the MOD 70 is the non-AC big-boat mainstream, then it seems a big call - there's only about 5 of them, sailing in one class in one corner of the world. The "real big boat mainstream" is arguably the mono classes like the 30m maxis, mini maxis, Wallys, and Volvo 70s. Note that there are many active boats that are much larger than MOD 70s, too.

But even if the 5 or so MOD 70s are somehow classified as the mainstream, the comparison between them and the AC 72 - wingsailed foiling cat v wingmasted tri - may still just show that the AC boats are further removed from that mainstream than earlier AC boats have been.

The IACC boats were not clearly more spectacular, faster or higher-tech than the contemporary ORMA 60s, G Class or IMS maxis, the 12 Metres were not clearly more spectacular, faster or higher-tech than the contemporary boats like Apricot, Club Med, IOR maxis, Vendredi Trieze, VSD, Manureva etc, the J Class were not clearly more spectacular or faster than Westward, Atlantic, Britannia, etc.

It seems clearly relevant to the topic since it underlines the fact that there is no great tradition of AC boats being miles ahead of other craft in terms of design, development or speed. That has been changed by the AC 72s. Whether one cares about tradition or not is one question, but the point is that it seems hard to use tradition as a reason to opt for the AC 72s as some people do.

The point is that there is simply no great tradition of the AC boats being the biggest, baddest, fastest, most advanced of sailing classes, as some have claimed. Therefore any call that the current boats represent a tradition is false.

There has always been, as Gary points out, a lot of media hype about the AC but to what extent media hype (and especially incorrect hype, as much of it has been in some respects) should effect what AC yacht design "should" be about is surely a very open question.

 

34th AC on Foils!

Lets keep this thread on the current America's Cup, ok?

 

OK by me as long as that doesn't mean limiting it to TNZ and Oracle. What're the other teams doing to stay in the game? Who are their key designers?

Also the Laurie Davidson business with TNZ vs One World, and to a lesser extent other episodes including but not limited to Coutts departure from Alinghi, make me wonder whether the teams have some sort of contractual lock on talent or their ideas once this America's Cup is over. Say James Spithill and Glen Ashby wanted to get together to challenge from Australia, or Coutts return to Team New Zealand, or Magnus Clarke to Canada, or Morelli/Melvin to a U.S. team, Botin to Spain, Verdier to France. Would there be any contractual impediment to that? Would there be an impediment were they NOT returning to their nations of origin, but just joining a different team?

 

This logic is hard to beat, then again it could still be a form of experimentation, to see if there is any merit in controlling twist for a future design / foil arrangement. Still, looks from the videos and lee hull movement that if the intention is to control twist then it isn't working too well.

I would of thought that the best argument against a 'twisty' design is purely on the basis of conservation of energy. If the power of the rig is being expended/absorbed by a bendy platform then it is not being used for forward acceleration.

 

All this sort of stuff is getting discussed on SA. It would be good to keep this thread focussed on the designs themselves rather than AC politics. Maybe start a new thread if you want to discuss that here?