Under the skin of the AC33

Alinghi Design Co-ordinator Grant Simmer talks us through the new rule

Obviously the America’s Cup is on hold awaiting the decision of the New York Appeal Court over the fate of the 33rd America’s Cup. BMW Oracle Racing think there could be news anytime after this Thursday.

In the meantime, Grant Simmer, one time Australia 2 navigator, now Alinghi’s Design Co-ordinator, talked us through the new class rule published at the end of January, that they and the potential competitors in the 33rd America’s Cup have been beating out and that will become reality should the court ruling go in their favour.

The complete rule is here

	AC Version 5		AC33 boat
	Metres	Imp	Metres	Imp
Length overall	24.5m typical	80.36ft	26m max	85.28ft
Length waterline	18-20m	59-65.6ft	26m max	85.28ft
Beam	3.3m typical	10.8ft	4.8m max	15.74ft
Draft	4.1m	13.45ft	5.0m	16.4ft
Weight in
measurement
condition	24T		17.5T
Mast height
from sheerline	32.5m	106.6ft	33.6m	110.2ft
Spinnaker area	512sqm maximum		unlimited
Mainsail area	214sqm typical		225sqm max
I from sheerline	26.1m	85.6ft	28.5m	93.48ft
J	8.3m	27ft	10m	32.8ft
Spinnaker tack
from mast	11.6m (pole)	38ft	13.65m (to end of bowsprit)	44.77ft

While obviously much work into the development of the AC90, the new boat may be the ‘credit crunch’ version, but is still whopping at 85ft long (26m), slightly bigger than a V5 boat. Significantly it won’t look anything like its forebears, with much more modern lines and significantly no overhangs - LWL was around 18-20m on a 24.5m typical LOA with the V5 boats. The new rule allows it to be as long overall as it is at the waterline. Given that the new boats, if they are ever built, may also compete in regattas such as the Maxi Yacht Rolex Cup or the Voiles de St Tropez, length-wise they also fill a hole between the Alfa Romeo/ Wild Oats/ Leopard/ Speedboat-sized supermaxis and the Mini Maxis. Ernesto Bertarelli envisages them becoming the new maxi class.

According to Simmer - and also an indicator of the genuinely democratic process that the development of this rule seems to have followed between defender and challengers - Alinghi were keen on the new boat having overhangs, but this wasn’t accepted. “We wanted a boat that didn’t look like an IRC boat. We were a bit nervous that these boats would look like every other boat, but measuring overhangs and having a simple overhang rules - we had a proposal, but we couldn’t really sell it. So we ended up with a box rule. That was a big issue.”

Simmer reckons that, as is the case with TP52s, the big issue with designing and sailing these boats will be how much you can afford to immerse the transom upwind - something they obviously didn’t have to address with V5 boats. “Moving the weight in the boat will be critical, the same as it is in an IRC boat - depending upon your speed, where you put your weight. The boat will be designed for different wind speeds - that is one reason why the beam is a little bit restricted at 4.8m Maybe people might go narrower than that. We didn’t want to have a huge range of beam to start with. We think that is fairly close to optimum.”



One of the interesting issues with going to this more modern beamy hull shape - the new boats will be some 50% wider than V5 boats - is that its evolution has come from the offshore world and is a million miles away from the narrow, angular slab-sided V5 boats. Reaching seems unlikely to be suddenly introduced to the Cup racing format so is this really a good hull shape for windward-leewards? Modern design thinking seems to be that upwind speed can be achieved less through monster bulb weight and a narrow hull and more through more efficient appendages and hull form stability, while a fatter hull shape and an enormous sail plan result in a boat much more likely to plane at times off the breeze.

“Because they are longer in the waterline, these hulls are very shallow,” states Simmer. “And with some flair in the topsides they are still picking up stability from the waterline plane when the boat is heeled, so they won’t be as U-shaped as the Version 5 boats, they won’t be as extreme. These boats won’t want to heel as much. The Version 5 boats you can heel them to 32° and they keep going fast upwind with a lot of heel. These boats, we think, will only heel to 25° or so. Once you get overpowered the V5 boats you just kept sheeting on and letting it heel more. Here you are going to have to be a bit more subtle, blading the sail, twisting the sail without adding too much drag. I think it will be quite interesting when they are fully powered up and they getting powered up quite early. In anything over 14 knots it will be quite interesting sailing upwind! But then also in anything under 7 knots they have got quite a lot of wetted surface so they will be quite sticky. So a bit like a TP52, they are really great boats in 8 knots and suddenly they get very sticky.”

The end result will be at the new America’s Cup yacht that will go equally as quick as V5 boat upwind and will blow them away downwind. They will look like IRC boats (consider how bizarre that statement sounds for a moment) but as they won’t require reaching ability, probably won’t be as wide. The sheer is dictated by the rule and is quite straight although Simmer foresees it having curved freeboard forward to reduce windage when the boat is heeled, although tumblehome is prohibited.

Rather than simply limiting bowsprit length, as they have in other such classes, with the new AC boat this is limited by the 13.65m JSP (base of spinnaker foretriangle) measurement and the J limit (base of foretriangle) of 10m. “So the bowsprit could be a different length depending upon how long the hull is in front of the forestay,” says Simmer, although it will be somewhere between 3 and 3.5m.

“There was a big debate about whether bowsprits should be retractable,” he continues. “At the moment they are mechanically fastened, so that if you have a collision and bust one you can put a new one on over night and you can’t claim redress. They were also very concerned about collecting the runners in a serious collision, because the runners could be right on the back of the boat, but there is a rule now so that the runners are 0.5m from the back of the boat.”

Although not featured in the rule yet, an added safety, anti-collision feature is that the boats may also have permanent battens of around 1m long, sticking out from the aft quarters of the boat and this will form part of the boat if another touches it. “Because we only have one boat, but also we used to have a scoop out of the back of the boat and if you had a collision and smashed into that, it wasn’t a major structural issue, but now if you crash into the back corner of the boat with the bowsprit, it could cause some serious problems. And if you hook up a runner at the same time then you really have a major on. So we want to put the battens out the back and we also see it as an opportunity for the event authority to put some branding on it. I think it should be substantial, although it won’t look that significant, but the whole idea is that if there is an error of judgement, you are always missing that batten. We do it a lot when we are training and we think it makes sense when we are racing.”

The sail plan is also very different. The mainsail area at 225sqm is only slightly more than a V5 boat and Simmer reckons that mainsail profiles with their giant square heads won’t change that much. “Gradually I think we’ll become more and more extreme with our mainsails because aerodynamically it is good. I don’t see any other reason why we won’t have that.” But here similarity ends – the spinnaker for example is unrestricted, or restricted solely by the physical size of the boat.

The J measurement has increased from 8.3 to 10m compared to V5. Simmer reckons headsail won’t be as high aspect as one sees on IRC boats but significantly they will be non-overlapping. “There are limits on the girth to prevent that and to prevent heavily hollowed leeches fitting around the spreaders for instance.”

So no flippers? “Yes, but the spreaders are in line on the boat. So you can vary the rake [by moving the mast step and adjusting the forestay strop] and you will a little bit, but the spinnaker area is unrestricted. It is interesting because it will be limited by the amount of sail area you will be able to fit on the boat. I don’t think the rigs are going to go a long way forward downwind because you will start losing luff length on your gennaker."



As a credit crunch AC boat, the developers of the new rule were keen to limit costs and one aspect that was scrapped was the AC90’s lifting keel. “That added a huge complexity to the AC90 and a few of the designers said this could be the Achilles heel of this new class,” admits Simmer.

Still with no lifting keel, the draft is set at an exciting 5m (compared to 4.1m for V5s) with the displacement down to 17.5 T from 24 of the V5 boats with a 100kg variation to allow for some tolerance in measurement.

There is no bulb or fin weight restriction. There are scantlings which control the hull laminate – conjured up by Alinghi’s own engineering guru Dirk Kramers and Emirates Team NZ’s Giiovanni Belgrano, but no controls on the structure inside the boat. “There is a rule that says that the keel fin has to be solid," says Simmer. "There was quite a lot of debate about what ‘solid’ meant as you might imagine given what had happened with the Volvo. But the idea is that we don’t spent a fortune on machining hollow keels which all of us got into a bit last time, because it is an expensive process.”

Due to the increased beam of the boats, twin rudders are allowed and like the VO70 rule there is a limit on the number of moving appendages. Of course, as ever the boats will be allowed to fit trim tabs, something that has featured on Cup boats since the 12m days. “These boats will have negative leeway,” says Simmer. “You can create enough lift to do that and you could do that in a Version 5 boat. And now this keel fin is higher aspect again, so it is more efficient. So you could have negative leeway if you want to. It affects the sails… But typically with the Version 5 boats we sail with very low leeway angles, about half a degree.”

While scrapping the lifting keel has helped, one of the greatest cost savings is in the sails. In the class rules it states that only one Cuben fibre sail can be on board at any one time, as Simmer says these are typically 2.5x the price of a nylon or polyester sail. The Competition Regulations will stipulate the size of the sail wardrobe, but here too drastic changes are afoot.

“The concept is that every sail you build has to be registered, even experimental sails, even before you are in competition, because we figured that that is the only real way that you can control the cost. Every sail you put up has to have quite a big registration number on it and we see it as being policed by the other competitors, because we will all be sailing in Valencia and we will all be watching the other boats…”

So the number of sails not just in the competition, but significantly also the number of R&D sails beforehand, are to be limited with the end result that big teams will be allowed to test perhaps one third the number of sails they were last time.

With this first iteration of the rule, the consensus was to the limit the potential for new development, given the shortness of the cycle and the advent of a new class of boat and the present economic climate.

Simmer provides an example: “One of the strong teams wanted to allow wingmasts basically and to tell you the truth we thought it was quite a nice development but we are introducing a new class and we need to make sure that the racing is interesting and close and we didn’t want the event to be dominated by one feature like a wingmast the first time around. We didn’t want to see the Cup won with a wing keel or a hula or a wingmast. We wanted to try and make the rule tight enough, so that it means that the boats will be fairly close. But there is a clause somewhere that Schnack [Tom Schnackenberg, who spearheaded negotiations over the new rule] put in there that long term we see that development happening.” Such developments also included inflatable sails and canting masts.

Another area where they intend to limit cost is in hull finishes. “Even in the 12m days we had wrigglets on the surface of the boat, like the surface of an LP record," continues Simmer. "They are just trying to organise the turbulent boundary layer a little bit - so really really small grooves in the surface, aligned with the flow - that was the concept. It was a vinyl coating we put on. That was in the late 80s everyone was putting them on the boat. Now you are not allowed to have textured finishes any more and because of the rule we haven’t done a lot of research, but there are people are saying it should heat up the surface, or some vibration in the surface. But in commercial aeroplanes you don’t see a lot on the surface. The front of the appendages all have a certain amount of laminar flow and trying to extend that percentage of laminar flow is something we’d all like to do, but at the moment it is small, something like 15-18% of the cord length of the foils in ideal conditions and then the more vibrations you have in the boat the less it is.”

So hence the rule states that ‘electric, magnet, sonic and thermal or other methods’ are prohibited as way of reducing this. “Every America’s Cup they come out of the woodwork with fancy ways of reducing the viscous drag of the hull and appendages,” groans Simmer.

Crew numbers are set to be same as before - 16 and one extra, and there is a crew weight limit of 1300kg.

As to IRCing the boat and racing it outside of the AC arena, Simmer reckons they will have a fairly rotten rating under IRC as it is a shallow hulled boat with a deep cockpit and so space below is likely to be confined to say the least, with no room for ‘accommodation’. Most likely is that in events outside of the AC these boats will race in their own class under their own class rule. They are looking at fitting an engine to the boats for reasons of safety and practicality for these regattas, but don’t see themselves, for example, fitting guard rails. Instead they will be allowed to have chase boats following them around the race course.

At the end of it, Simmer is excited by the prospect of the new boat and particularly the potential for the next AC33 if it goes their way. “The one thing that really saves your money is the short cycle, so for a team that has just started, like the JoeFly team for example, this will be the cheapest, cheapest entry into the America’s Cup that you could ever get. I really think that for 20 million Euros you can do a really credible campaign. 20 million today is a lot of money, but for the last Cup it would have been a bit of a joke.”