sail-world.com -- America's Cup: Nick Holroyd on Emirates Team NZ's design gains + Video
America's Cup: Nick Holroyd on Emirates Team NZ's design gains + Video
Fri, 18 Jan 2013
'These boats have a long gestation', explains Nick Holroyd.
'The designs for the tooling up at Cookson Boats, were delivered after just four or five days sailing in Boat 1.'
'At that point we had confirmed foiling, and we were able to move the hull geometry into the more upwind speed, trim and performance areas.
'We also have a huge amount of load of data from Boat 1,' says the Emirates Team NZ Technical Director.
The design team have added weight in some areas and reduced it in others - all of which is focussed on achieving greater reliability as the program heads more into a regular race mode. Something which is relatively easy in a monohull, but much more difficult in the brave new world of the AC72.
'The third aspect for improvement is realising that we really have to be able to push hard is really critical to performance. Features which make the boat easier to sail, or push the boat harder when the conditions warrant it, have all been factored into this boat.'
Holroyd won't be drawn when questioned has to how much quicker Boat 2 will be than Boat 1. Obviously the team will have 'raced' them in the design computer. Instead he lists the areas they expect to see gains - improvements in the hulls. (Despite being open with the media, cameras were asked to be averted from the bow and stern areas - indicating that these are probably the areas that have been tweaked between design versions).
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Next he points to the changes taking place next door in the wingsail shop - another area of expected improvement, and then there is the second generation of foils. Changes in systems, and the ways the crew are able to handle the boat are another point of improvement from Boat 1 to Boat 2.
'Across the board we are looking for improvement', is about as close as Holroyd gets to putting a number on the degree of gain.
He's equally coy on the changes in the foils. Bigger or smaller? Another sidestep. 'Some dimensions shrink and others grow. Span always works, but structurally that is very very difficult to achieve.
'We're looking a more effective cross-over for the stability to be able to foil well, but achieve low drag to go upwind.'
Whether the Boat 2 will foil upwind is still a matter of conjecture. 'The VPPs (velocity prediction program, used for modelling relative design performance) suggest that might be possible, but I'm not so sure that's necessarily the fastest solution, yet. That's an open area for investigation, I guess.'
Downwind the emphasis is going on getting onto the foils quickly, and to begin foiling at lower wind-speeds. Achieving that goal is a matter of collaboration between the design and sailing teams. 'A lot of the discussions we have been having with Dean and the guys is how their technique works with the controls we have given them - and whether they need a finer control in some aspects or whether they need to be able to move things faster. All those things add up as well as the shape of the foils.' explains Holroyd.
'Control of the shape of the wingsail across the windrange, and being able to achieve twist profiles quickly and reliably are the main thrusts,' he says of this stage of the wingsail program.
Interestingly Holroyd says they can develop significantly more twist with a wingsail than they can with a softsail. 'you also have the ability with wingsails to move the Centre of Effort up and down the sail much more easily. That is the main benefit of them in this class. In over powered conditions you can continue top bring the centre of effort down
'We are also looking to change gears really quickly,and how the control systems in the wing allow you to do that. We are looking to be at close to optimum performance 100% of the time.'
While the design objective has been aimed at developing straight speed, as Emirates Team NZ moves into race mode they will also look at trading off some aspects of their boat to get an gain in other areas relative to their competitors. 'We trying to best optimise our chances against the other team's boat', says Holroyd.
Accuracy in the team's ability to hit their performance prediction numbers has been one of the hallmarks of the campaign to date. 'Dan Bernasconi (head of VPP) has a remarkable track record in this campaign in terms of performance prediction and going beyond that and being able to tell the sailing crew before launch what the settings should be for the expected wind range.'
'Every time we get to marry real world data back to what we find in our computer is a golden opportunity for us to improve our skills and ability to predict these things. that's been one of the things that has worked really well for us from early on in the campaign', he says in conclusion.