NEW KIDS ON
THE BLOCK
AC45 on the fly with Australian Crew.
the AC 45 and AC72 catamarans
Putting all the shirt fronting, litigation and future speak aside, ORACLE Racing has started to reinvent the America’s Cup from the waterline up. To give the event continuity and its sponsors round the clock coverage, a new class of boat and a new event has been created, this being the AC45 and an annual America’s Cup World Series. Following on from the AC World Series and becoming the main attraction will be the ‘real’ America’s Cup sailed in the ‘AC72 Class’ a large, exceptionally powerful wing-sailed catamaran. by P E T E R S C H WA R Z E L p i c s by G I L L E S M A RT I N - R AG E T
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bits are easily replaced and this also solves the containerisation problem. If all goes well to the AC45 plan, there will be races in August 2011 in Cascais, Portugal, September – Plymouth, England, November – San Diego and other venues to be announced for 2012. Sydney and Perth are currently actively pursuing venues as well ...
HE AC45 AND AC72 encapsulate all the past and present go-fast technologies. Larry Ellison said “The Cup is to be for the fastest boats with the fastest sailors”. So be it ... Australia has the fastest sailors and can build the fastest boats so all you potential supporters out there now’s your chance!
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The AC45 guff The AC45 is a one-design 45ft highperformance catamaran. It is very fast and manoeuvrable, easy to pull apart, M U LT I H U L L W O R L D
stack into a container and freight to the many international venues envisaged for the World Series. A trimaran was considered but since the craft would be sailed on one hull only, the trimaran design was dropped. I’m sure the designers took a long look at the Extreme 40’s and their successful history before implanting the AC-DNA into the design. So how do we put a 45ft boat into a 40ft container? Well the rear 1.5m of the boat is bolted on. This means in the case of the inevitable impacts these
The wing The most visually different feature is the wing. Wings have been the weapon of choice for the C-Class cats for quite a while. They have appeared briefly in A Class Cats and the Moth Worlds as well. Wings are easier to control than large soft sails as their shape is fixed. Soft sails change shape with the wind pressure and good trimming lies somewhere between science and art. Wings can produce up to twice the lift of a soft sail with much less drag. This reduces the lift/drag ratio so they can sail closer to the wind than a soft sailed boat. Close hauled they can sail under 20° to the wind. Wings control twist by having several flaps just like an aircraft does. Each flap can be individually controlled or they can be controlled as a bank. This also allows the top flaps to be feathered to reduce the heeling loads as the wind gets stronger or as the boat sails faster. It’s expected that the AC45 will be raced at speeds of 20-30kts with sprints up to 40kts possible. The wing is made from carbon fibre and plastic shrink film. They are fairly robust but if damaged are easily fixed. Just like we carry spare tyres in our car, the teams will have an on shore spare wing. Wing words • Leading and trailing edges rather than luffs and leaches; • Panels – Panel one is the leading panel, panel two is the next aft panel, wings can have three or more panels • Slot – Just like a sloop rig, the wing slot is very important to improve the wing’s drive. On some wings, an extra flap is used to control the slot air dynamically • Camber – The amount the wing is bent or curved. A two-panel wing sail can
be cambered considerably more than a soft sail can. More camber means more power • Leading edge twist – unlike conventional masts, some wing sails can twist their leading edge and their trailing edge, improving the angle of attack of the sail and generating more lift than a non-twisting rig can. AC materials Standard modulus, intermediate modulus and some high modulus carbon fibre is allowed in the AC72 rules. Titanium is allowed and will be popular for small highly stressed parts. Since the AC45 is a one-design boat we actually don’t know what it is made of. The AC45 is made by Core Builders and Cookson Boats in New Zealand. If the class takes off, it’s intended to license builders in other countries as well. Master plugs have been built so licensed moulds can be supplied to suitable builders. There are many very good AC45 construction photos on http://www.americascup.com/ The hulls The hulls have a reverse sloping bow which helps in preventing the boat from tripping on waves and pitch poling. The
forward part of the hulls are very full which also helps in avoiding ploughing. Some of the current boats have submarined the lee hull with no pitchpoling. The bow knuckle is designed to pass over the water rather than through it, which reduces spray drag. The rudders are under the hull to further reduce drag and to remove them from the impact zones. A recent wipeout in the Extreme 40’s saw a boat get its stern mounted rudders sliced off and its crew bailed out as it careened across the fleet and into the dockside! Great TV! Another feature of the AC72 hulls is they have gybing daggerboards allowing the crew to steer the boat upwind. This will introduce some very interesting race tactics. Hull words • Cp – The Prismatic Coefficient, modern multihulls have high Cp’s (Cp>0.7) thus minimising pitchpoling and allowing the hull to travel very steadily in the water • Wetted area – Multihulls have a very small wetted area and therefore have much less skin friction than a monohull • Form stability – A multihull uses its large beam to resist the heeling forces of the sail. The AC72 is one third the
weight of a Volvo 70 yet has a bigger righting moment. Movable ballast or water ballast is not allowed under the current AC rules • Submerged rudder – Unlike beach cats, the new boats use submerged rudders which increase the foils efficiency as they do not pierce the surface creating surface waves or suffering from ventilation • Fn – The Froude Number, the Fn is a mathematical expression describing the ratio of a boat’s waterline length to the ‘wavelength’ of its associated hull waves. Wave making drag is one of the major components of overall drag and is minimised by using slender hulls such as catamarans have. The AC past The original 1851, ‘£100 Cup’ and ‘International Race’ was sailed in 200 tonne working boats that sailed on their own bottoms to and from England and America to challenge and defend the Cup. We now have eight tonne racing thoroughbreds that get flown around the world in the battle for the oldest sporting trophy. Times do change! M U LT I H U L L W O R L D 3
The future The AC45 World Series is intended to be a training ground for the main event, the ‘America’s Cup’. The AC45’s will become the boat for Youth Sailor Development and have its own Youth Series. The next America’s Cup will be raced in 72ft supercharged versions of the AC45 called the AC72 Class. These will have 38m (125ft) high wings and will be sailed by 11 crew. Race speeds are expected to be in the 25-40kt range and who knows how fast the top end will be. Americas Cup management hope to create two long term annual events with the fastest boats and the fastest sailors. The Youth boat will be the AC45 and the Senior boat the AC72. Every two or three years, a suitable, challenge will result in an America’s Cup event. Given the long, complicated and colourful history that the chase of the Auld Mug has given us I say long live the Americas Cup.
Footnote At the time of writing this article Team Yachting Australia, the fifth Challenger for the 34th Americas Cup received confirmation that their AC45 would be delivered on May 30, 2011. Team Yachting Australia intend to contest the AC45 World Series and then continue onward to contest the AC72 Louis Vuitton Series and obviously the Cup itself. They are looking for major and minor sponsors. Have a look at ausac34.com.au and sailcam.tv for more interesting stuff.
About the author Peter Schwarzel is a registered engineer in Queensland Australia. His company CarbonWorks designs and analyses yacht structures for naval architects and boat builders. He sails as much as possible and looks forward to seeing Australia back in the America’s Cup competition.
AC45 statistics Two boats per team max LOA 13.45m Beam 6.9m Displacement 1400kg Mast Height 21.5m Sail Area Upwind - Wing+ Gennaker 133m2 Downwind - Wing + Reacher 210m2 Operation five crew, one guest or camera operator Cost $1M AUD plus
AC72 Statistics Two boats per team max LOA Beam Displacement Wing Area Jib Code 0 Gennaker Operation Cost
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22m 14m 8500kg 260m2 185m2 255m2 200m2 11 crew, 1 camera person and 1 guest $10M AUD plus