A few weeks ago, Dave Reed, editor of the US magazine Sailing World, interviewed Emirates Team New Zealand technical director Nick Holroyd. We think the story offers an interesting insight into the AC72 design process. Part 1 of his report:
As the 34th America’s Cup draws nearer, the development of the America’s Cup 72 catamaran moves into overdrive. Emirates Team New Zealand hit the water first and fast. Dave Reed interviews Nick Holroyd who admits: “It’s far more complex than anything I’ve ever been involved in.”
Holroyd, who’s been in the America’s Cup game since 1997, oversees the collective brainpower of more than 30 engineers, designers, and programmers —all tied together in a complex web with the AC72 catamaran at its centre.
The end game is to usurp the Auld Mug from its formidable defender, Oracle Team USA, but the playbook is wide open. Wings, hulls, hydrofoils, rigging, electronics, and manpower are the core elements of these new craft, but for each known entity, says Holroyd, there is another unknown.
In an exclusive interview following the August launch of Emirates Team New Zealand’s first AC72, Holroyd explains where they’re at with the first of their two boats, and where they may go before next summer’s Louis Vuitton Cup.
When you were handed the AC72 rulebook, where did the team begin, and where did you put your efforts straightaway
Intuition tells you that there are areas where you think you’re going to find big gains. The wing is an interesting one. Structurally it’s quite complex, but making it easy to use on the water so that you can get optimal shapes easily and repeatedly is important.
The aircraft industry has bequeathed us a lot of knowledge already, so the aerodynamics of the wing is not as complex as you might think. With the platform, what’s important is to quickly get to a level where your velocity predictions are good.
Once you get to that level, you can start looking at the drag breakdown, and that denotes where to put your effort. We have to put more effort into the bigger ticket items like the wings and platforms, which require longer lead times to design and build.
With a compressed racecourse on San Francisco Bay and relatively short legs, how do you weigh straight-line speed versus faster manoeuvres?
A lot of the manoeuvres will come down to the fact that you’re seriously understaffed in terms of the loads involved [with 11 sailing crew], so keeping systems simple is key.
Boats that go fast in a straight line tend to go fast out of manoeuvres as well. Bow volume, from what I’ve seen, is an obvious difference across the fleet so far. That dictates how hard you can lean on the boat coming out of manoeuvres. Also, the ergonomics of the boat and the platform, and being able to handle the loads on the boat efficiently are critical.
What are the defining traits of your first boat?
We’ve gone with a boat that’s relatively sea-kindly and has volume features that allow it to be pushed very hard.
Our boat, in terms of windage, is far from complete. All the fairings are still to come: The boat will look significantly different in race mode. One of the issues with putting all the fairings on the boat is that it makes a lot of the systems difficult to get at and tune, so we chose to put the boat in the water in a raw state to facilitate that development process.
The launch date for our second boat is February next year, so we’re in the middle of tooling up for that boat. We’re later than we wanted to be. I’m sure everyone else is late as well.
A multihull of this scale is a complicated structure; explain what you have going on under the boat.
Our platform and Artemis are on a similar model with a diagonal structure in the back of the boat, which acts as a truss and stiffens it torsionally a great deal.
Tornado sailors will say torsional stiffness is paramount, but the price you pay is more under-rigging and under-structure. A lot of choices come down to stiffness versus windage. Windage is easy to quantify, but torsional stiffness is a lot harder, so this is one of the hardest tradeoffs to put a number on.
How do you spread pedestals and deck gear around?
With the wing on this thing, righting moment is impossible to ignore, so we’ve split all of our deck gear between the two hulls. We sail with 11 up on the weather hull, which makes it crowded, but these boats are righting-moment sensitive.