By Matthew Sheahan
February 3-4, 2003
Source: www.lvcup.com

Part I

Upturned bows, bat wings and square spinnaker poles all fell from the AC toy cupboard.

Explaining where the money goes in an America's Cup campaign is a tricky business, but totting it up is easy. Even a conservative guess would put the total amount of money spent on this season's America's Cup campaigns at a staggering US$550million.

With the top teams employing 100 people or more, the wages, accommodation and subsistence bills are huge and account for a large proportion of the overall costs. And while the boats themselves don't come cheap, research and development costs aren't far behind when it comes to the big bills. So what does the 2002/3 America's Cup circus have to show for all this time, effort and money?

While Team New Zealand's hula has stolen the show recently, the previous five months have revealed plenty of design innovations – some new and some simply developments of earlier ideas.

After the 2000 Cup, Team New Zealand's narrow hull, double knuckle bow and Millennium rigs were the details that most of the Challengers seemed keen to incorporate into their designs this time around. The outstanding NZL-60 may have provided a starting point for many of the design teams, but not everyone's hulls looked like the infamous black boat of 2000.

Alinghi and Oracle BMW Racing were among the most distorted hull shapes, especially when it came to their sheer lines forward. Both boats sport foredecks like Canadian canoes as they sweep vertically towards the bow. Slab-sided topsides have been another common feature this time, allowing the boats to sink down into the water when heeled, providing an increased sailing waterline length.

Many of the idiosyncrasies of America's Cup hull design are just that, a peculiarity and a means of exploiting the ACC measurement rule. But while hulls, keels and hulas have taken the limelight, many of the developments for this Cup have been in the details.

First out of this season's America's Cup toy box were the unusual looking top spreaders – ‘bat wings’ – as they became known. Within weeks of the start of the event, many of the teams were sporting these swivelling top spreaders in an attempt to achieve larger headsail areas by extending the roach of the genoas.

Under the ACC Rule, battens are forbidden in overlapping genoas. Broadly speaking, most of the sail area outside the triangle between the head, tack and clew is not measured and therefore free, so designing the leech of the genoa to run more vertically from the clew to the head achieves more sail area. The problem is then how to support this oversized leech without battens. The bat wings do just this.

Because ACC boats only race windward/leeward courses, the headsail is either sheeted fully home or sitting on the deck, so upwind the leech can be supported as the sail presses against the upper spreader. The device also allows the slot between mainsail and jib to be held open towards the hounds too, which improves the airflow through it. The spreaders rotate so that their tips point skywards when sailing downwind to prevent them from bursting through the mainsail when the it is squared away.

Also helping the aerodynamics in the upper part of the rig, independently adjustable jumper struts allow the leeward jumper stay to be swept further aft when the strut itself is swung back. This also allows the roach of the genoa to be larger and to be sheeted home without clashing with the jumper stay. Although this particular development isn't altogether new, (many of the 12-Metre yachts and some of the modern ACC boats in previous Cups were fitted with these), the detail goes hand in hand with the bat wing development.

While looking at the sail plans, mainsails have changed shape too with square heads being favoured by teams like Alinghi, Oracle BMW and Prada. The idea is a familiar one in many catamaran and skiff classes. Aboard America's Cup class boats the detail helps to reduce the drag of the sail, while also helping to support the leech of the mainsail itself.

Developing faster downwind sails has occupied plenty of design, construction and testing time, but from a spectator's point of view it is difficult to identify specific details in the spinnakers themselves. While significant progress has been made in the design and construction of asymmetric spinnakers in particular, most teams and sailmakers have remained tight-lipped on the detail. However, the use of staysails is far more difficult to conceal.

Here, Oracle BMW’s crew were the first to reveal their additional downwind sail and seemed keen to hoist their staysail whenever they could. Initially, at least, this boat was thought to have less upwind sail area than her competitors, which in turn meant that she flew smaller spinnakers too. Hoisting a staysail helped to make up the downwind sail area deficit. But as the team tweaked its boat to set more sail area upwind, the downwind habit seemed to stick. In the finals against Alinghi, both boats flew staysails at times.

Spinnaker poles have seen big changes too. Prada's square section spinnaker pole achieved greater stiffness without adding weight, when compared to a circular section. The square section shape allows more of the material to be positioned further away from the neutral axis (centreline) of the section and hence made the pole stiffer. Simple but smart.

Alinghi have remained with a more conventional circular section pole but have chosen to seek an advantage in reducing the windage of the pole when it is stowed on deck. They have achieved this by building a recess along the length of the foredeck in which the pole sits when it's not being used. (Windage has been an issue when it comes to the spinnaker pole tracks too, with a variety of solutions ranging from bolt rope type slots in the front of the mast, to pole track fairing devices.)

Team New Zealand appears to have opted for the most radical approach and has developed triangular section spinnaker poles. The reason for this unusual configuration is less clear, but the theory as to getting more material away from the neutral axis and creating a stiffer pole, could still be along the right lines. This idea is supported further with the unusual corrugated bottom surface to the triangular section. Presumably this is to increase the stiffness of the panel which suggests that the poles do indeed gain their strength from having the bulk of their structural material positioned out towards the points of the section.

The home team has employed a similar principle for at least one of their mainsail booms. Instead of opting for the more conventional rectangular section shape boom, the more radical boom is wider at the top than it is at the bottom, creating a triangular shape. Beneath the cladding, the boom appears to consist of a lattice work structure, similar to the AucklandHarbourBridge but upside down with the sides and top clad in lightweight panels.

The idea is to get the structural parts of the boom as far away from the neutral axis as possible, which allows less material to be used in a more efficient manner.

Part II

In the search for speed, teams have strived to lower windage from the mast, standing rigging and sail plan.

Part 1 of our America's Cup technical feature discussed developments from bat wings to unconventionally shaped spinnaker poles. But teams have also strived to lower windage to streamline a boat’s movement through the wind.

Since winning the America’s Cup in 1995, Team New Zealand has been a leader in technical developments. Having shown the Cup world a thing or two in 2000 with its three-spreader Millennium rig, Team New Zealand appears to have tweaked the set up by moving back to a four-spreader mast while still utilising the Millennium configuration of double diagonal stays.

"There's still a long way to go with rigs, the induced drag from the sails remains an enormous part of the total drag," said Team New Zealand's Tom Schnackenberg. "Induced drag comes down to sail shape and rigs are a part of that. So it's probably still one of the areas that has the biggest possible opportunities."

In building a mast with four sets of spreaders the sideways support is improved allowing the mast to get skinnier in the athwartships plane. This reduction, along with an Increase in the fore and aft dimensions of the tube, has helped to further reduce the windage. Having said that, there is an increase in windage from the extra rigging, but it would appear that even with this extra drag, the net drag of the complete rig is still less than for a three-spreader rig.

Other teams have also been looking at reducing the windage generated by the rig. Prada, among others, experimented with the use of double rods for some of the primary shrouds.

The idea is based on the principle that a circular section is one of the most inefficient shapes when it comes to drag. Elliptical or aerofoil shapes produce less drag but rigging with a profiled shape is banned under the class rules. (In the 1980s profiled rod rigging or lenticular rigging, as it was known, was common aboard 12-Metres but was expensive to produce.) Spreading the load onto two smaller diameter stays that present a smaller frontal area to the oncoming breeze is one way of reducing the drag although there are further limitations under the class rules. The stays cannot touch each other and the gap between them cannot be closed off.

Nevertheless, this rule does not apply to running backstays or checkstays, which are considered to be part of the running rigging package. The most recent example of drag reduction was seen aboard Oracle BMW's USA-76 in her last race of the Louis Vuitton Cup Final. Aerofoil section covers were fitted around the running backstay for its entire length. In order to keep the foil aligned with the airflow, a set of four weathercock-type tabs kept the foil balanced into the breeze.

Even without these drag reducing covers, minimising drag from the rigging has become part of the regular routine for the crew as well a task for the designers. When the boats are sailing upwind, the top mast backstays are frequently detached and taken forward to the mast to keep them out of the airflow. A trick employed by Team New Zealand in the last Cup match and since copied by most.

While making your own boat go quickly is one thing, keeping tabs on how your competition's doing is another extremely important aspect. Here the rules are tight once again, indeed so tight as to eventually clamp down on several teams who were using laser range finding devices among other systems designed to track the performance of others.

The issue had come about after the controversy and confusion surrounding Oracle BMW's so-called goose. To date little is known about what, if anything was inside and what it was doing. But as the American team bowed out of the racing, a few more details came to light, suggesting that the system was not, as many had thought, a radar device.

Instead, one of the more plausible theories was of a sophisticated tracking system that locked onto the communications loop aboard a competitor’s boat. All the top AC teams were using radio links between key members onboard, which could have provided a means for locating and tracking the opposition.

For all the technology and effort that has gone into the detail, as the big match approaches, attention will be drawn to what lies beneath the waterline as the final reveal day draws closer.

Team New Zealand's hula has been widely debated as has, albeit to a lesser extent, Alinghi's so called J-Low, their version of the same concept. Few people doubt that Team New Zealand will use their innovative device come the match, but there is more speculation as to whether Alinghi will chose to use theirs.

Also on the list of unknowns is whether TNZ will use their radical torpedo-style keel bulb. Time will tell on both these scores and the next few weeks will no doubt reveal even more ACC tweaks and tricks from the world's most expensive toy cupboard.

But for all the money time an effort that goes into developing the world's most advanced and refined racing yachts, it's comforting to know that even at this level, some America's Cup innovations can still be bought at your local gardening centre.

As GBR Challenge boss and regular 17th man Peter Harrison found out, the view from a plastic patio chair costing just a few dollars can be worth millions.