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RS Sailing 2021 - LEADERBOARD

America's Cup - Dan Bernasconi on shaping the AC75 'Beast'

by Richard Gladwell, on 5 Oct 2017
Comanche by VPLP/Verdier - 100ft LOA with 25ft beam is the fastest monohull in the world, and a possible template for the AC75. Lauren Easley /
Dan Bernasconi, Technical Director of Emirates Team New Zealand, has turned his hand from leading the team charged with developing the quickest America's Cup multihull on the planet to performing a similar feat with a monohull.

First step in the process is coming up with a concept boat, and then writing a class rule to accommodate that type. The 75ft monohull has been given various monikers, but the reality is that several design concepts are still under evaluation.

'We started at about three, then it grew to around 10, but now we have narrowed it down again. It is really exciting for the small group of designers that we have to be able to start with a clean sheet', he told Sail-World after the main media session concluded last Friday at which the Protocol for the 36th America's Cup was revealed.

'It is a weird process for us. We are so used to pushing hard against a rule and trying to make the boat faster. It feels strange when you don't have a rule to work to, as we usually try to work the edges to make the boat faster and faster.

'We want to have a boat that is really good for match racing, while still being a really high-performance boat. But there is a lot of other criteria as well.'

Bernasconi wouldn't play the guessing game by naming an existing boat or class that was close to the design and rule group's thinking.

'At the moment it is open. We have been looking at trying to super-charge a conventional displacement boat, as well as looking at semi-foiling boats, and also to see whether it is possible to develop a fully foiling boat that will be suitable for the America's Cup.

'We have got a wide range on the drawing board. We are having discussions with the Challenger of Record while they are down here, and will work towards a final concept for the end of November.'

Comanche benchmark?

Does Comanche (the extreme 100ft supermaxi, designed by VPLP and ETNZ design group member Guillaume Verdier which also holds the monohull 24-hour speed record) come close?

'I can't say,' replies Bernasconi. 'At one end of the scale it might look very similar but at the other, it wouldn't. We are going to have to wait and see, but it is not far away', he responds without giving even a non-verbal clue.

As with multihulls the key to getting high performance in a monohull is righting moment with light weight. An AC50 tips the scales at around 2400kg and 8.5metres beam and drawing 2.4 metres. A Comanche scaled down to 75ft weighs around 20000kgs has 6.0metres beam and draws 4.5metres. Quite a different proposition from the lightweight AC50 foiling catamaran which carries 575kg of crew weight to add to the righting moment. With 10-12 crew and a similar average weight restriction, the movable ballast in crew weight for the AC75 will come in the range of 875-1050kg.

There are two ways of improving righting moment in a monohull - one is a canting keel. The other is to use racks to get the crew weight further outboard - which allows a reduction of the weight required in the keel bulb, equating to an all up weight reduction and performance improvement.

'We have looked at both those options,' he responds. 'Some have had racks, some have had canting keels. We have covered the whole range.'

Canting keels beg the question as to how these are swung to the windward side during a tack or gybe. Will manual or motor power be used?

'It is really difficult to make a good match racing boat with a completely manually powered canting keel. You have to be able to do tacks with a small tack loss. If it takes two minutes to grind a keel from one side to the other, then you're always going to be tacking on the boundaries [i.e. trying to minimise the number of tacks on a beat and gybes on a run].'

'If we have a canting keel, battery power will be an option,' he adds. As with some supermaxis, it is likely that some form of computer [PLC] control will have to be permitted to control the rate of swing of the canting keel.

Some have surmised that an AC50 wingsail is an option for the AC75 monohull, but that would appear to be off the table for several reasons.

'We are looking a lot at soft sails. I think the wings are great and in terms of aerodynamic performance, you can't beat the kind of wing we had in an AC50.

'On the other hand, it is not that applicable to guys sailing boats outside the America's Cup because you need a crane to get the wing in and out every day. It will depend on the boat concept, but we are looking at options that aren't wings.'

Is a dry lap possible in a monohull?
Some visions for the new AC75 class have it that the monohull will be capable of foiling constantly in the same sailing style as the AC50. Will the most extreme versions of the AC75 be capable of sailing a dry lap?

'I think we are not far enough advanced in our modelling to be able to know the answer to that,' explains British-born Bernasconi, who has a PhD in Mathematical Modelling and Aerodynamics, spending six years with McLaren Racing before moving across to the America's Cup teams. 'For sure you can make foiling monohulls, the Moths have proved that. Whether you can make that a practical boat to get around the course is something that we are still looking at.

'It is one end of the scale we are looking at,' he adds.

Another way of getting a steer on the current thinking for the AC75 class is the number of appendages. 2-3-5 or 7?

'At one end of the scale', Bernasconi explains, 'there are two appendages - a keel and a rudder.

'At the other end of the scale, we have had all sorts of numbers of appendages. But again cost containment is one of the requirements. So is trying to make a really high-performance boat - and the exercise has become quite open-ended.'

There has also been a lot of speculation on the type of foils likely to be used in the new class, nicknamed “The Beast” by those who have seen some of the concept drawings. But what effect will the foils have on the speed of the boat? Will there be a big speed difference between foiling and non-foiling mode in the monohull, or will it be only a couple of knots difference upwind?

'Again it depends on where we end up. If it is a foil assisted boat then there will be a windspeed at which the foils become beneficial upwind, and there are a lot of parameters that control that - and that is one of the things we are looking at,' he explains.

Where do you see that cross-over?

'We have got a range of options. I can't give you a number for that.'

Boat-park practicalities
Will the boats able to be carried in a travel-lift?

'It is one of the things we are looking at in terms of the logistics. It would be great if we could have a single point lift for the boats. A travel lift is another option. Sorry, it is difficult to give you answers because we have so many different boats on the table - but it [being carried in a travel lift] is one of the considerations.'

The design and rule drafting group is currently all drawn from the ranks of Team New Zealand and are based in Auckland. The same group was challenged to 'throw the ball out as far as we can, and then work out how to reach it' with their AC50 program - coming up with several design and sailing innovations which gave their campaign a crucial edge in Bermuda.

'At the moment it is 50% of the designers from Team New Zealand's last campaign. There is a group of about 10 of us - all Team NZ designers. With the Challenger of Record's visit to Auckland this week we have been having a lot of discussions and talking about concepts with them.'

Currently, there is no input from other teams from the last Cup on the boat concepts. Currently only one, Land Rover BAR has said they are committed to compete in the 2021 America's Cup.

'We have had discussions with them [35th America's Cup teams] about what sort of boat they are interested in and what the factors are for them. But as yet they haven't been involved in the actual concepts of the boat.

'When we get into details of the rule, certainly we will benefit from a lot of roundtable discussions. Although we are planning to publish the rule at the end of March, it is hoped that we can have discussions with other teams about developing drafts before that.'

Inside running
One of the areas of concern with any class and design rule development in the America's Cup is that those involved in its creation have the inside running and a head start on other teams. How is the design group communicating progress to other teams - so they are seen to be running the process fairly and aren't seen to have inside knowledge?

'Today [the announcement of the Protocol] is the start of that process,' explains Bernasconi. 'We have had informal discussions with members of our team, and various members of other potential teams. We are aiming to have the concept completed for the class of boat in November which is only eight weeks away. Hopefully, we will get all the teams together, have a lot of discussions on the class, what our vision is and start to draft a rule around that.

'The rule is not going to be out at the end of November what will be available then is a presentation of the concept of the boat, so it will be pictures of the boat, a vision for how it will sail, ideas of what will be one-design or supplied components.

'That will be a good time to get all the potential teams together and get input from them and start putting a rule around that boat.

'For sure it will have aspects of a box rule about it. All America's Cup Rules do to some extent,' he adds.

Even though it was a one-design class - in terms of the hulls, wingsail profile, and platform the class rule for the AC50 or America's Cup Class used in Bermuda ran to 26 pages plus Appendices. Bernasconi says that the document produced at the end of March will be similar to that used for previous editions.

'The structure of the rule will be similar to previous America's Cups. Probably it will have a maximum draft a rig height, and probably a maximum beam and if there are foils, the maximum length of foils - or the maximum beam with foils extended; weight; construction materials and so on.

Cost cutting pragmatism
One design options, pioneered in the last America's Cup are definitely on the table. While that might not please the traditionalists, pragmatism is very influential.

'I think there will definitely be some one design components. It is really important for us to keep the costs down,' says Bernasconi.

'With the AC50 it made complete sense for the hull to be one design. There is no point in the teams spending vast amounts in R&D to make a hull slightly faster that is out of the water 99% of the time.

'It makes sense to have one-design parts of the boat that don't have a huge amount of performance potential in them. It also makes a construction saving. If you leave something open design, then you are forced to make multiple iterations of it.

'If it is something you can lock in early and doesn't have a massive performance hit, then if it is an expensive one design component you only build one of them. Or one and a spare', he adds.

The probability of one design components, maybe even hulls, raise the question of the design challenges in the new class for new teams? With the AC50, despite having one design hulls, platform and wingsail profile the foiling multihull proved to be a design race - even more so than the monohull days.

Before the AC50, in the keelboat days, the International America's Cup Class had five versions of its rule in the 15 years between the 1992 and 2007 Cups. How much design scope will there be in the AC75 class?

'It does depend very much on where we end up on that spectrum', explains Bernasconi. 'At one end of the scale, the challenge would be in hull design and sails predominantly - that's at the [heavier] displacement end, as well as appendages.

'At the other end of the scale with a boat that is foiling some of the time, the design challenge will put more emphasis on the foils and on sails that have a lower apparent wind angle.'

Teams react, or not, to new Protocol

The new Protocol has received a lukewarm response from the existing America's Cup teams aside from Land Rover BAR. The way things stand of eight teams expected to enter the 2021 event only two of those would have sailed in the previous America's Cup regatta and would have know-how from that event that could be transferred into the new class.

'As an engineer or yacht designer you develop a lot of tools and processes in a number of different areas be it in hydraulics, electronics, computational fluid dynamics, structural analysis and all of that is applicable', Bernasconi predicts.

'I think all teams will be looking for a mix of designers that have got expertise in those areas - a lot of which will come from Cup teams. But there is always benefits from bringing in new talent.'

The concept for the new AC75 Class is expected to be unveiled at a (potential) Competitors Meeting in Auckland at the end of November 2017. Those attending will have the ability to have input into the development of the class rule to be published at the end of March 2018. The first AC75's can hit the water 12 months later and will race in a regatta three months after that.

Entries open in January 2018 and close six months later, or late entries will be accepted until November 30, 2018, with the payment of a US$1million late entry fee.

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