America's Cup - Bernasconi on expected winning factors in Bermuda

by Richard Gladwell, Sail-World NZ on 18 Apr 2017 Emirates Team New Zealand's Technical Director, Dan Bernasconi has let out a few clues as to where he thought the differences might lie once the six teams entered in the 35th America's Cup shaped up in Bermuda.

'We have had a great run. We've had a few hiccups along the way, as always. But the boat is going really well. We are getting through manoeuvres very well. And we think our straight line speed is good.'

'But until we line up with the other guys, it is hard to know where we stack up on that,' adds the team's Technical Director, who holds a PhD in Mathematical Modelling and Aerodynamics, backed up with a Masters from Cambridge University.

Having spent six years in the heady world of F1 and the McLaren Racing team, Bernasconi came to Emirates Team New Zealand after the break-up of team Alinghi in 2010.

'There are a lot of very complex systems on the boat - wing control systems, daggerboard systems, rudder systems and obviously we are pushing all of those as hard as we can. We haven't made life easy for ourselves, and there were always going to be some teething problems, but nothing too major. We are happy where we are at the moment.'

Addressing the trade-off between reliability and boat performance, Bernasconi says performance comes first. 'Our main goal is to make a fast boat that will get us through the manoeuvres. We can't afford to be relaxed on reliability but ultimately if we lost one race because of reliability and won all the others because we had a faster boat, we’d be in good shape. Speed is more important,' he adds.

Asked to comment on the video footage coming out of Bermuda (on Youtube via MyislandhomeBDA), Bernasconi says he has been mainly focussed on what Emirates Team New Zealand are doing, they are watching footage from Bermuda, and the primary information source has been a recon team that Emirates Team New Zealand have been running in Bermuda.

'We have to keep abreast of the other teams.'

'I think the teams are converging,' he says. 'The daggerboards and rudders are a massive part of the design to us, but probably not as visible to those watching. The teams are definitely moving in the same direction regarding shapes, thicknesses and probably the structures, probably.

'But there are subtle differences, it something that we are watching very closely on our competitors.'

With the hull shape being one design, and to a minimum construction specification; and with a fixed profile wing sail, some believe the design options have become more restricted in the AC50 class. Others closer to the design team action disagree commenting that there is more to play with in these boats than there ever was in the monohulls.

That prognosis seems to be borne out in the three longer duration Practice Sessions in Bermuda, where one boat has been dominant. Artemis Racing had a bad opening day in Practice Session 2, but after that scored two wins over the America's Cup Defender and took another four wins off Oracle Team USA in the third session - often coming from behind.

Lighter air performance is yet to be really tested in the Practice sessions.

Surprisingly with just a month or so to run to the start of the America's Cup Qualifiers, teams do not seem to be on their final daggerboard and rudder configurations - which will cause a further shift in the America's Cup paradigm once those new foils come into play.

Bernasconi believes there will be several factors in play to determine the relative speeds of the six teams contesting the America's Cup Regatta.

'The appendages will definitely be a part of that. The real questions will be how accurately you control those appendages; how accurately you control the rudder; how accurately you can control the daggerboards and how well you can control the wing.

'Those items all tie in with power and the more power you have, the more adjustments you can make.'

'It is a matter of getting those pieces of the puzzle together and getting through the manoevres.

'Each manoeuvre takes a huge amount of power - getting the daggerboards up and down, big rake changes on the daggerboard and again having more power available helps in that situation.'

Looking at the nuances of daggerboard design, Bernasconi says the chord length (the overall length measurement from the front to back of the daggerboard, or profile width) 'is a really important performance number.

'That is something which teams have been iterating on. The chord length you chose is a trade-off between how soon you get foiling and how fast you go once you are foiling. There is a difference between the teams on that.'

'Some teams are at the higher end of the scale on that, and that maybe some of the reason why they have a slower performance in some conditions, but can be better in manoeuvres.'

Bernasconi compares the simple theory of hydrofoil performance to that of a aircraft wing. At low speeds, you are looking for a wider wing to assist with quick take-off, and at higher speeds, you want a smaller wing for lower drag and faster speed.

'It's a trade-off we look at very carefully. In the AC50, at lift-out, you need a lot of area, and as soon as you are foiling and flying, you would rather have much less area.

'In an aircraft, you have flaps which extend for the take-off and landing. We don't have that ability, so we have to work out how to take-off with the least amount of area and then in a straight line make the best performance we can given that we have too much surface area.'

Bernasconi says the team design development plan has run pretty much to expectations. That is despite not having the multiple AC45S test platforms available. Two teams have launched four such boats ahead of their single AC50. Emirates Team New Zealand made do with a single AC45S but used a rule loophole to get the same sailing geometry as the 1.5metre longer AC50 - and were sailing their AC50 configured test boat six months ahead of the allowed launch date for the real thing.

Which begs the question as to whether the Kiwis have been able to achieve more with less?

'Everything has gone pretty much in line with our expectations. We worked very hard on simulation tools in the first part of this campaign, rather than try to develop on the water.

'So everything on this boat has been developed through simulation - and it has tested on the water in line with our expectations.'

The initial call on the accuracy of that design, simulation and test program is expected to be answered later this week when Emirates Team New Zealand's AC50 sets sail for the first time on the waters of the Great Sound in Bermuda.