An AC34 in multihulls?

No one at the 33rd America's Cup said 'let's not have the 34th in multihulls'. So why won't it happen?

So convinced yet? They may not have the same turn-on-a-sixpence characteristics as the monohulls used on the World Match Racing Tour or even Version 5 AC boats, but the multihulls that competed last week in the 33rd America’s Cup were astonishing in terms of their performance, sailing upwind at four times wind speed and, as James Spithill amply demonstrated, were more than manoeuvrable enough given some practice, even with a 226ft tall solid wing sail demanding constant attention.

During our time in Valencia we didn’t go out of way to find endorsements for the prospect of multihulls being used in future America’s Cups. They were willingly obliged.

Despite feeling he was forced into a Deed of Gift match, Ernesto Bertarelli was already pro-multihull having helmed multihulls on Lake Geneva for more than 20 years. After racing on Sunday he commented: “We came out today and there were a couple of Version 5 boats out. They really looked like models compared to what we were sailing... I think it is one of the few times in recent years we have the fastest possible boats racing each other. So why would you want to go slowly?”

The most succinct endorsement came from his skipper Brad Butterworth, who up until a few months ago we got the distinct impression hated the damned things. When asked whether the America’s Cup should go back to monohulls, he commented: “I think just the fact you do a Deed of Gift match where there are no rules, it shows you that it is the fastest solution on the planet. You can always go back to the classic monohull boats and the racing would be fine, but if you want more exciting stuff, like I think we have shown we can probably have, then with more time you could make the boats more reliable to sail in more wind or whatever. It might be pretty exciting. I’d still be a fan to keep it in the multihulls.”

Fellow Alinghi crewman and ex-Team New Zealander Murray Jones also felt multihulls would be viable for future Cups: “I think that is what this has showed you. You can match race in anything. With the multihulls – there is plenty of scope. These two boats [the 33rd AC multis] are completely different to each other and if you spent a little bit of time on it you could have some very good racing.”

Even Russell Coutts, who when we have spoken to him in the past has firmly held on to the US team’s party line - that for the 34th America’s Cup they would be returning to monohulls - may have cracked: “Although I started off two months ago being pretty strong on the fact that it should return to a monohull competition, I have to say it was pretty spectacular racing and maybe that is something else the America’s Cup community should think about hard,” he said on Monday.

Coutts’ boss Larry Ellison was even more enthusiastic about them when pressed on the point by Cam Lewis: ‘what is the coolest boat you’ve ever raced on in your life?’ “The RC44 is pretty cool!” joked Ellison. “Okay, the coolest is that big trimaran not so far away from here with that amazing wingsail. The amount of power you can generate and how quickly the trimmers can adjust the thing – that is the part that is really remarkable. In very puffy breeze Cheese [Dirk de Ridder] can ease that thing and in a lull he can power the thing up, so it is very responsive to sail. Given a boat that big and the loadings on the boat being that extreme, it makes driving a lot easier. It is far by the coolest boat I have sailed on.”

And his skipper James Spithill is now fully converted: “The only downer [of the 33rd America’s Cup finishing] is that we aren’t going to sail the boat. It is such a cool boat to sail and I’m talking on behalf of the guys – we looked forward to sailing it every single day. It is one of those very special boats. It is so rewarding.”

Spithill added: “When we got the two boats together – we had a bit of a guess on the crossover. For the racing, especially the second race was really enjoyable as a boat race.”

As to the BMW Oracle Racing solid wing rig, Bertarelli was still on a bit of a downer about it: “It is a very good solution, but it is not convenient. I think we are going to have wings once in a while, but I don’t think it is going to mainstream. I think this America’s Cup was about speed - I think that will become more mainstream in the world of sailing. I think that the days of spinnakers are over in my opinion.”

However Alinghi’s mast specialist Murray Jones is convinced it is the future. “You are going to see development in this area a lot more.”

So will the 34th America’s Cup be held in multihulls? Of course not. And the reason for this will mainly be because multihulls are not what most of the decision makers within the Cup community know about or find aesthetically pleasing in a sail boat. There is also a reasonable argument that they are likely to be more expensive than a monohull of a similar length. But as Russell Coutts has repeatedly argued, much more money could be saved in terms of limiting training time than on the cost of the hardware.

Given the democratic way that the boat for the 34th America’s Cup looks likely to be decided, a monohull will inevitably end up being chosen, and we suspect one probably not that dissimilar to the AC33. This will have a lighter displacement than a Version 5 boat, but how much lighter? If the decision makers opt to go the whole hog for an ultra-light and powerful monohull, then the argument against multihulls becomes a thin one as their handling characteristics are similar to ultra-light monohulls.

After all there is the argument that the America’s Cup is the supposed pinnacle of our sport and typically the best resourced. So - referring back to Brad Butterworth’s point – surely whatever is the most state of the art in yacht design at the time should be used?

In the hope that the America’s Cup community does go multihull, Californian naval architects Morrelli & Melvin, who were involved with the design of the BMW Oracle Racing trimaran, have come up with what an America’s Cup multihull could look like for a multi-challenger event. Their AC90 appears to be a half-way house between the Alinghi and BMW Oracle Racing multihull designs with a similar platform to the Swiss cat, albeit with a single spine running aft from the maststep to the rear cross beam (rather than Alinghi 5’s preferable Y-configuration) and the same shallow C-curve foils as the American tri. The design also inevitably features a solid wing. We feel that if a boat such as this were chosen then some work would have to be put in to find a more practical solution for handling the wing, in particular being able to step or unstep it.

The vital statistics of the AC90 are:
LOA  27.4m  (90 ft)
BOA 19 m (62.3 ft)
Displacement 7.1 T (15,700 lb)
Mast height 51m (167’)
Upwind Sail Area (wing + jib)    752 m2 (8091 ft2)
Downwind sail area (wing + gennaker)     996 m2 (10,717 ft2)
Crew 8-12
Righting moment 70 TM (500,000 ft*lb)

Pete Melvin writes: The AC90 is a concept created to explore the design parameters for an America’s Cup class. The cornerstone of the design was a maximum righting moment of approximately 70 tonne-meters. This righting moment was chosen as a starting place for a yacht that was smaller and less expensive than the yachts used in the 33rd AC, but that still offered spectacular size and performance, and that could be sailed efficiently and aggressively using manual winches.

Righting moment is perhaps the best indicator of loads and cost for a multihull. For instance, the Alinghi cat generates approximately 150 tonne-meters of righting moment, not including water ballast. The AC90 generates less than half the estimated righting moment of Alinghi so the cost and loads should also be less than half that of Alinghi.

The catamaran configuration for the AC90 was chosen for the initial concept but the actual rule and sailing conditions anticipated would undoubtedly require a re-think of this initial concept.

So we put it to Pete Melvin - wouldn't this be a more expensive option? "I’m not so sure it would be. We looked at that. Obviously it depends on the monohull, if it is something with canting keel, certainly I don’t think the cost would be any more. And is the cost of the boat in the AC really a major factor? I’m not really sure it is. And you can scale the concept up and down to get the cost in line with where you think it should be.

"Essentially the righting moment and cost and weight are all closely linked and since they tend to go as the cube of the length then you don’t have to scale the thing down very far at all to get the thing down to half the righting moment or half the cost. So that is why it is 90ft overall rather than 110ft or whatever Alinghi was. Just scaling down that much gets the boat to half the righting moment and cost."

Obviously the AC90 is the example of what a multihull box rule for the America's Cup might be. Melvin reckons that rather applying physical limits to a rule, instead you could more or less just limit it to a righting moment number.

"That would be quite interesting because that physically limits the size of the boat. You could define a righting moment rule fairly simply, being the weight of the actual boat times half its beam essentially, plus whatever crew weight and ballast you might put out on the weather hull. It could be fairly easily controlled and really I think that would make an interesting rule because you wouldn’t be constrained by some sort of fixed dimensions. Then depending on the venue, whether it is a windy or a light air venue, the configuration, the ratio of length to beam and mast height could change accordingly and it would produce boats optimised for their intended task instead of fixing some dimensions and making something work within those dimensions even though it may not be optimum."

By doing this the solution could be a cat, a tri, a hybrid or even a long skinny monohull. "I think that would produce more wholesome boats rather than forcing it into a corner like formula rules always tend to. You always get pinned into some tangent that doesn’t really lead to a better boat in the end."

And what about a solid wing? Despite his AC90 having one, Melvin reckons that in reality it might be best to prohibit them, simply for reasons of managability. "The wings are a pain to deal with. Some beach cats prohibit them by specifying the maximum chord of the mast. You could do something like that. But these teams are pretty big and they already have some tent to keep the boat up. The C Class guys do it and Oracle did it but it was a gargantuan task for them to monitor the boat at the mooring all the time. So it might be better to forego the wing."

Couldn't someone come up with a better solution for stepping and unstepping it? "Possibly," responds Melvin. "The solution the Oracle guys came up with was pretty ingenious. You stepped the wing on the boat sideways and there was  a gin pole to raise the wing with the boat’s own winches and power. You needed a crane to get the wing to the boat, but to tilt it up or down you didn’t need a crane. Maybe there is a better solution out there for raising or lowering the wing, if someone has a brilliant idea. For now it is a logistically quite hard."

A multihull for the 34th America's Cup debate is already underway in our forum.