Offshore Log: America’s Cup Technology

From the cutting edge to the mainstream-at the apex of the racing scene, sailors break things until they get them right. Eventually, the refined parts trickle down to the rest of us.


From the preamble to the America’s Cup Class Rule, the set of rules governing the design and construction of the boats used in the Cup: “The America’s Cup Class is intended to produce wholesome daysailing monohulls of similar performance while fostering design elements that will flow through to the mainstream of yachting.”

Offshore Log: America’s Cup Technology

My job, as part of the four-man international committee that oversees the creation and implementation of the rules that control the design and construction of these boats and their equipment, is to make sure that designers and builders play by a fairly strict and complex set of rules. Our goal is to make sure that speed on the water is derived from legitimate development rather than manipulation of the rules.

It is an elusive goal. We often go head-to-head with the smartest people in the world of marine design and construction, and it’s not always an even match. We’re in a constant struggle to stay up with the game, if not ahead of it.

Unlike most sporting events, where most of the activity takes place in the public eye, the only public part of the America’s Cup is the sailing competition on the water. The design and construction of the boats is a highly proprietary process. At this level, gains of a small fraction of a second per mile around the race course are huge. Any design or construction feature that has the potential to gain even the slightest edge is protected by a veil of secrecy worthy of the secrets of the atomic bomb.

Fortunately for the rest of us, many design innovations of the America’s Cup do in fact trickle down to the rest of sailing. Details jealously guarded by Cup competitors this year may show up in the general sailing marketplace within a few years.

The closest analogy that can be drawn is with Formula One auto racing, where many innovations have in fact made their way into automobiles driven by the rest of us. Fuel-saving lightweight construction, high-performance tire designs that increase traction in marginal driving conditions, improved braking, and driver/passenger protection systems are just a few of the automobile racing developments that in one form or another are now folded into the design of everyday automobiles.

In the sailing industry, a number of innovations in design and construction that saw their genesis or perfection in the America’s Cup are now on virtually every cruising or daysailing boat. We’ll look at just a few of these here.

Computer-designed, lightweight, high-strength sails, such as North’s 3DL series of molded sails with oriented fibers, are America’s Cup developments that have vastly improved the sails that all of us use. You may not have the carbon-reinforced 3DL sails used on an America’s Cup boat, but you have much of that technology aboard if you have high-end cruising sails built in the last three years.

The first sail of molded one-piece construction to appear in the America’s Cup was a genoa used in 1992 aboard Dennis Conner’s Stars and Stripes. I remember looking at that fairly primitive sail on the floor of North’s San Diego loft late that spring night with North president Tom Whidden, not fully realizing that I was seeing the future of performance sail design and construction.

By 1995, the vast majority of the headsails and mainsails used in the America’s Cup utilized 3DL technology. In 2002, every headsail and mainsail aboard every competing America’s Cup boat is a fiber-oriented North 3DL molded sail.

While North holds patents on 3DL technology, other sailmakers have created their own oriented-fiber sails that are lighter and stronger than their conventional predecessors. Special 3DL sails using long-life fibers and membranes have been developed particularly for cruising boats.

If Dacron sails were an enormous leap forward from cotton sails, the low-stretch, lightweight fibers used even in “conventional” modern sailcloth have enabled similar giant steps to be made in sails. In particular, the use of lighter, stronger sail fabrics has helped make feasible the huge cruising yachts built today, whose sails would have been impossible to handle just a decade ago.

The trickle-down to the rest of us is obvious. Yes, you can still buy conventional Dacron sails for your 35-footer. But they are likely to be lighter and more dimensionally stable than the sails you could buy just a few years ago. They will perform better for a longer period of time, thanks in part to the America’s Cup.

If you own a larger boat, the advantage of higher-tech sails is enormous. Lighter sails mean lighter boats that can be sailed efficiently with a smaller crew.

The 60-footer that we raced offshore not that many years ago weighed over 60,000 pounds, and required a crew of 12 to sail efficiently. Lifting a Kevlar genoa on that boat took at least four of us. Changing headsails in severe weather was both exhausting and dangerous.

Today, we know a number of husband-and-wife teams who are cruising the world aboard 60-footers. A well-designed modern cruising 60-footer with carbon fiber spars and lightweight sails will weigh less than 45,000 pounds. Thanks to lightweight construction and equipment, the husband-and-wife crew can average 175 miles per day or more on a 60-footer with less effort than we expended to achieve 150-mile days aboard our conventional 40-footer.

Carbon Spars
While carbon mast, booms, and spinnaker poles were not invented for the America’s Cup, the design and construction technology that brought them to today’s level of achievement was perfected in the Cup.

The complete rig for an America’s Cup boat-mast, standing and running rigging, boom-weighs just 2,000 pounds. An aluminum rig of similar properties would probably weigh at least 50 percent more.

This same spar technology completely dominates the custom cruising and racing sailboat market. Less weight aloft means lighter keels are required. Saving 100 pounds at an average height of 25 feet off the deck of a 40-footer translates into roughly 500 pounds off the keel of the same boat to maintain the same righting moment.

Carbon masts for cruising boats under 50′ are still significantly more expensive than their aluminum counterparts. In larger boats, which may require custom aluminum mast sections, the carbon/aluminum price differential diminishes quickly.

Even a traditional small cruising boat like our 40-foot Calypso can benefit from carbon technology. Our Hall Spars carbon spinnaker pole weighs just 20 pounds. A 20-foot aluminum pole would weigh more than twice that amount.

While the handling advantage of the lighter pole is obvious, there’s another big advantage as well: The carbon pole can be stowed vertically on the mast, which both keeps the decks clear and makes deployment simple. A heavy aluminum pole stored on the mast would have a much bigger negative impact on righting moment.

A great deal of research has gone into the development of lightweight, low-stretch running rigging for America’s Cup boats, and that technology is immediately accessible to every sailor.

When we rigged Calypso prior to setting off on our circumnavigation, Phil Garland of Hall Rigging-one of the world’s experts on standing and running rigging-recommended Technora/Spectra blend running backstays rather than conventional stainless steel wire. While these cost slightly more than wire runners, they reduced chafe on the mainsail, are much lighter, and have similar stretch properties.

With their multiple sets of running backstays and checkstays, America’s Cup boats have potentially huge amounts of weight and windage aloft. This weight has been cut dramatically in just the last few years. You can buy the same stuff for your boat off the shelf at any decent chandlery.

Offshore Log: America’s Cup Technology

In New Zealand after the last America’s Cup, we replaced our original low-stretch polyester halyards with new halyards of Spectra or Vectran, materials widely used in high-performance racing yachts and huge cruising boats, but rarely seen on a traditional 40-footer.

The performance difference was immediately noticeable. In heavy going, our old polyester halyards, even though of low-stretch construction, would elongate significantly. Our new Vectran halyards of the same diameter and similar weight show about half the stretch of polyester halyards, and look like new after 20,000 miles of use.

Aboard America’s Cup boats, the low-stretch halyard has been augmented by halyard locks. Halyard load is transferred to a fixed lock at the head of the sail, and the halyard is unloaded. This halves the compression load of the halyards on the mast, and eliminates halyard stretch completely.

Most halyard locks are custom-made for a specific mast and boat. In the America’s Cup, these locks must be operable from the deck for safety reasons. They range in complexity from a small trip line on a snap shackle to beautiful, complex mechanisms costing thousands.

On big cruising boats with in-mast mainsail reefing and roller-furling (reefing) headsails, halyard locks can dramatically reduce compressive load on a mast and increase safety margins. The problem, of course, is that halyard locks need to be 100 per cent reliable-which they are not, in many cases-to be used on a cruising boat. On a day-racer, a broken halyard lock is an inconvenience that might cost you a race. On an offshore cruiser, a non-functional halyard lock could be a disaster.

Construction Methods
Custom racing boats such as an America’s Cup yacht are generally one-off hulls. Traditionally, these boats have been built over a male mold, or “plug,” which is a fast and cheap way to build a one-off boat.

The disadvantage of male mold construction is that the finished hull exterior must be faired and painted. This not only means a lot of labor, but a lot of additional weight compared to a boat built in a female mold.

The average production sailboat actually has a lighter-weight exterior finish than the typical America’s Cup boat, which may have several hundred pounds of fillers, primers, and paints on the hull.

In a reversal of technology, several America’s Cup syndicates have built boats using female molds-similar technology to that used by production boatbuilders. The catch, of course, is that the female mold process is expensive for one-off construction. As no more than two boats can be built from an America’s Cup mold, the cost of a female mold is amortized over only two hulls, rather than the dozens or hundreds of hulls pulled from production-boat tooling.

In addition, because America’s Cup boats must fit precisely into a dimensional envelope that is measured by us to half-millimeter accuracy, the mold must be very, very precise. This means that the male “plug” used to create the female mold must be accurately built.

Generally speaking, the male plug is machined by a computer-driven multi-axis miller capable of producing a finished 80-foot dummy hull to an accuracy of a few thousandths of an inch. Over this plug, a female mold is built, inside which the actual hull will be laid up.

But that’s not all. America’s Cup hulls are built of carbon fiber, epoxy resins, and honeycomb cores of either aluminum or resin-impregnated paper (Nomex). The hull and deck structure is allowed to be cured under vacuum, and to a temperature of about 200 Fahrenheit. Because carbon fiber has a different coefficient of expansion from the fiberglass materials used in the construction of a female mold for production boatbuilding, the female mold for an America’s Cup boat must be built of the same carbon fiber that will be used to create the final hull. At the end of the day, the female molding process for an America’s Cup boat requires building a hull three times: the male plug, the female carbon mold, and the final carbon hull laid up inside the female mold.

The additional step of creating the female mold adds significantly-we’re talking hundreds of thousands of dollars here-to construction costs.

What exactly are the gains? The female-molded hull (the “part,” in trade jargon) has precise exterior dimensions and a shape that can be exactly replicated in a second hull. More importantly, the hull comes out of the female mold with absolutely no filling or fairing, saving anywhere from 50 to 200 pounds in the hull, depending on the skill of the boatbuilder at minimizing filling, fairing, and painting a conventional boat.

For sponsor-driven programs in the America’s Cup, it is an agonizing decision just to paint the boat or apply sponsor logos, as this inevitably adds to the weight of the hull. Every kilogram that goes on the boat in the form of paint comes directly out of the keel bulb. In these narrow, deep boats, weight in the bulb is a major input into upwind performance. In the America’s Cup, the boat that gets to the first weather mark before the other boat wins the race about 80 percent of the time.

Construction Material
The use of laminating fabrics pre-impregnated with catalyzed epoxy resins allows precise control of resin-to-fiber ratios in a Cup yacht. Because the resin itself adds little to the mechanical properties of the laminate, builders want to maximize fiber content and minimize resin.

Until heat is applied, the resin in the pre-preg laminates does not begin cross-linking-curing to a solid state. The laminators can take their time with precise fiber orientation in the creation of the hull, giving the exact mechanical properties sought by the laminate engineers.

A conventional open-mold fiberglass boat is built using “wet” layup. In this process, catalyzed resin is rolled into the cloth as it is laid in the mold, yielding a relatively short “open” time for hull layup before the whole thing cures to a solid mass.

Don’t expect your next 40-foot cruiser to be built of the same carbon fiber used in America’s Cup boats. Carbon is still more expensive than glass, and pre-preg carbon requires greater skill in application than conventional fiberglass layup, meaning higher labor costs. Unfortunately, it’s not easy to combine carbon fiber with other materials such as fiberglass to create laminate reinforcements that would incorporate the positive properties of the different materials for use in more conventional boats.

Carbon is used almost everywhere in the America’s Cup-from hulls, to fittings, to sail reinforcement-where its cost and labor-intensive construction methods are less important than the positive properties of stiffness and dimensional stability.

The honeycomb core materials used in America’s Cup boats are unlikely to provide the longevity that most of us expect in our boats. While the light weight and stiffness of these cores is a big plus in an America’s Cup boat, you have to remember that these are essentially throwaway boats, designed for less than a year of sailing before they’re obsolete.

If this seems wasteful to you, you should read the past history of the America’s Cup. A hundred years ago, Nat Herreshoff blew America’s Cup competition away with a boat that incorporated a lead keel, steel interior framing, bronze bottom plating (which could be burnished to as perfect a racing finish as you see on today’s boats), aluminum topsides plating to save weight, and light white pine decks. That floating battery of a boat was ready to be scrapped by the end of her Cup match. The difference in electrical potential between the aluminum and bronze, neatly and effectively electrically tied together by steel, caused the boat to begin to disintegrate the day it was launched. Throwaway boats for the Americas Cup are hardly a new concept.

The Numbers
While the exact dimensions and construction details of any America’s Cup boat are proprietary, we can give you a general sketch of the modern IACC yacht.

On a length overall of about 83′, the boat will have a static waterline of about 60′. Heeled at 15, the entire aft overhang is immersed, giving a dynamic waterline length of close to 80′.

Beam is largely controlled by the headsail sheeting angles. A beam of less than 12′ would not be unusual. These modern boats approach both the beam-length ratios of the “plank-on-edge” cutters of late 19th century America’s Cup boats and the waterline-to-overall-length ratios of J-class yachts.

Because of the narrow hull, the boats have relatively little form stability. Stability comes from a lead keel bulb weighing well over 40,000 pounds, suspended from the hull on a fin of high-tensile steel. The bulb and fin constitute about 85 percent of the all-up weight of the boat.

When you subtract the weight of keel and rig from the total allowable weight of 55,000 pounds, you’re left with about 7,000 pounds for the hull, deck, and all the hardware for an 80-footer.

It’s no wonder that both Harken and Lewmar have developed special ranges of ultralight carbon winches and deck hardware for use in these boats. Fortunately for the rest of us, this specialized hardware technology translates directly into the mass sailing market.

While the only pieces of deck hardware on these boats that look exactly like the stuff on your boat today may be the winch handles-honestly, these are off the shelf-a large percentage of the technology in the boats will be in marine catalogs next year, if it’s not already there.

As extravagant as the America’s Cup seems, it’s still true that racing improves any breed, whether it’s horses, cars, or sailboats. And the America’s Cup boats are definitely thoroughbreds.

Nick Nicholson
Nick Nicholson is a boatbuilder, racing sailor, and circumnavigator. He began his career at Practical Sailor as an Associate Editor in 1979, and has been Editor-at-Large since he left full-time work in the early 1990s to finish building a 40’ cutter in his backyard, and subsequently sail it more than 40,000 bluewater miles. The voyages of Calypso were chronicled in the Offshore Log section of Practical Sailor during that circumnavigation. He has also raced from the US east coast to Bermuda more than 20 times, winning numerous navigator’s trophies in the process. In recent years, he has primarily worked as a race official and technical rules advisor in the Volvo Ocean Race and the America’s Cup. He also chairs the Technical Committee for the Newport Bermuda Race.