Technology tacks toward the cup

DN Staff

April 10, 1995

15 Min Read
Technology tacks toward the cup

San Diego,CA-- This year's race for the America's Cup is the most technology-driven in the event's 144-year history, and for one very important reason: Technology reduces the cost of competing.

Few have pockets as deep as America's Bill Koch, who spent $68 million to build four boats while defending the Cup in 1992. This year, all the defending syndicates-PACT 95, Team Dennis Conner, and America3-have budgets of $20 million or less. Each may build only two new International America's Cup Class (IACC) yachts. These limitations put pressure on design teams to find the best possible design before the boat is built.

The way to do that: Use software.

Software lets designers run through hundreds of design iterations before building and testing a model, never mind committing to an actual boat. Says Dennis Conner: "Our designers must consider thousands of variables, from hull shape and sail size to weather conditions. Each minor adjustment could add or subtract 10 seconds from the boat's race time."

"Everything that can be done in a computer simulation saves money and time," states PACT 95 President John Marshall. "Of course, it's also significantly risky, because the more distant from nature and full-scale you are, the more approximations are involved and the more intellectual risks the programmers take. That's what's exciting about the whole process: balancing the risk and reward."

Boat designers must work within the constraints imposed by the International America's Cup Class. They must follow guidelines concerning dimensions, materials, and methods, and live by a formula that balances length, sail area, and weight. Among the design considerations:

Sail area: The larger the area the faster the boat.

  • Hull: Longer is faster. The shape, or waterline length, also affects speed.

  • Keel: When sailing upwind, lift is desirable and drag is not. To optimize straight-line speed upwind, designers look for a keel shape with the highest lift-to-drag ratio. Designers might optimize lift for quick acceleration, but at the expense of drag in the straights.

  • Bulb: The bulb, which may contain 15 tons or more of lead, provides the boat's balance. Winglets on the bulb may provide additional lift for easier maneuvering.

  • Displacement: A heavier boat is more stable, but slower, since it sits deeper in the water, increasing the hull's hydrodynamic drag.

Probably the most critical design component is the 1.5- to 2-inch-thick hull. IACC hulls have inner and outer skins of carbon fiber and low-temperature-cure epoxy. Between the skins is a honeycomb core of Nomex aramid or aluminum. To restrain costs, designers use carbon fiber that's a step down from leading-edge aircraft materials.

Inside the hull. OptiStruct software from Altair Computing (Troy, MI) helped PACT 95 design the internal structure of Young America's carbon-fiber hull. OptiStruct-a mechanical design synthesis program-starts with a maximum allowable envelope of a structure and the loads it is expected to carry. Via a series of successive iterations, the program calculates where material should be placed to carry the load and where it can be eliminated to reduce weight.

PACT 95 used the program to design keel and mast attachment bulkheads. It devised a maze of tubes to supplant the traditional bulkheads and plates. This technique let designers reduce the weight of these hull-reinforcing structures so that more weight could be added to the boat's keel. Such a design will heel a little less in a given wind, making the boat faster.

Designers used Altair's Genesis-a traditional shape and size optimization tool and FEA solver-to refine the design and develop the structural keel area. Additional analysis was done using Ansys.

The America3 team built on the technology it used and researched on the way to winning the America's Cup in 1992. Most of the 1992 design team pitched in again for the 1995 effort, picking up where they left off. They used MultiSurf software from Aerohydro Inc., Southwest Harbor, ME, to design 3-D surfaces, such as the hull, keel, wings, and lead bulb.

Autodesk's AutoCAD let the team make 2-D drafting drawings of deck layout and the boat's lines. Designers also used Autodesk's AutoSurf 3-D surfacing package. AutoSurf can perform volume, area, and mass calculations, which are required for the IACC formula. The software also interfaces to machine shops and NC machines to create boat models.

"Autodesk products were indispensable for designing America3 boats," says Carol Vernon, naval architect for America3. "AutoCAD saved time, money, and gave the design team an edge." The designers also used AutoCAD to geometrically solve force problems, plot data, and create input data for a computerized plywood cutter.

Lockheed Space Systems helped Team Dennis Conner create Stars & Stripes' structural design. Cadillac had GM's R&D center do the finite-element analysis to optimize the hull's outer skin. GM ran the proprietary software on a Cray supercomputer. Team Dennis Conner also used Cosmos/M FEA software from Structural Research and Analysis Corp.

"We analyzed how to orient carbon and Kevlar(TM) fibers in layers, which determines how the hull will perform," says David Howarth, senior administrator for GM's R&D Center and Cadillac's technical liaison with the team. Different parts of the hull have different numbers of layers. The goal: to make the hull as stiff and light as possible.

Bring in the water. Two separate Boeing teams did CFD-computational fluid dynamics-analysis for both Team Dennis Conner and PACT 95. CFD predicts the flow of water over the boat and the resultant pressures and forces its components will feel.

Engineers used Boeing CFD software, software developed with NASA for airplane design, and in-house geometry programs. Ed Tinoco, a senior principal engineer with Boeing, says yacht design and Boeing's interests have quite a bit in common: "These boats have gotten so sophisticated that 1% in performance can be the difference between winning and losing. In the commercial field, 1% of fuel flow in an airplane is hundreds of thousands of dollars a year. In that sense, we're playing the same game whether it's a plane or a sailboat." Boeing is also learning more about drag and gaining this knowledge from a different perspective.

Ford worked with Boeing and Cray Research to do the CFD for PACT 95's Young America. After doing the software analysis, Ford did wind-tunnel and tow-tank tests to validate its software. Ford uses CFD for the exterior automotive surfaces of each new design to make aerodynamic cars that get better fuel economy and reduced wind noise. Ford also uses the technology to analyze engine-compartment airflow for better cooling and less resistance. They validate those results-surprisingly enough-by dragging an engine compartment through a tow tank.

PACT 95 built Young America without first building a prototype. Using "modular refinement," designers focused on computer-aided design, analyzing thousands of design configurations on Cray's supercomputers. This approach was an efficient and cost-effective way to evaluate many designs without building expensive scale models. PACT 95 selected only the most promising designs for model testing.

They merged all the best simulated and tested components into one design. Result: "The final hull design was not tank tested-something we're proud of," says Naval Architect John Kuhn of Science Applications International Corp. (SAIC). His company played a leading role in managing the overall design program.

In past years, Team Dennis Conner used a $200,000 custom computer system to help make critical design decisions. For the 1995 race, designers looked for a more flexible and less costly solution that would let them write their own custom application while still providing the powerful analytical capabilities required in yacht design. Their choice: Microsoft's Excel version 5.0 spreadsheet.

Each design variation was "raced" in Excel against a benchmark boat to determine which was faster under various conditions. Excel also generated "targets," or ideal boat performance, to maximize speed while sailing. When the boat hits the water, the team gathers information on weather, speed, and performance, real time, through a sophisticated sensor system on the boat. The crew can modify racing techniques to try to hit the target goals set forth by Excel.

Still top secret. Secrecy is key. The boats are shrouded in plastic "skirts" to hide the keel, bulb, winglets, and underbody-parts that are subject to fewer design rules and can give a boat a decided edge. Design work continues on the interchangeable parts such as the keel, fins, bulbs, rudder, and mast. Once the race is down to two defenders and two challengers, the skirts come off.

After the race is won, secrecy is moot. North Sails and Boeing will be able to talk about what they learned working for the different syndicates. And new technology will take to the air and the highways, as well as the seas.

Rules of the game

In 1992, the America's Cup rules changed to require that all boats be International America's Cup Class (IACC) yachts-no more catamarans. These 75-foot-long boats are lighter, longer, and have 70% more total sail area than their 12-meter predecessors.

The rules defining the class balance the speed-producing parameters in the design-length, sail area, and weight-in a formula. Changing one variable requires designers to modify one or both of the other variables to ensure the formula yields a value of less than 24. For example, if designers increase length, they must increase weight or decrease sail area. If they take on weight, they can increase length or sail area.

The bottom line: Decide which corner of the design envelope is the fastest.


Overall length......................75 feetWaterline length..................57 feetBeam (width)........................18 feetDraft (depth)........................13 feetMast height........................110 feetSail areaMain/jib..............3,000 square feetSpinnaker...........4,500 square feetDisplacement..........45,000 poundsCrew............................................16

New materials capture the wind's power

Sail technology for upwind sails-the main sails and genoas-is developing rapidly. Team Dennis Conner and PACT 95 used 3DL molded sails for the first time in an America's Cup race, and America3 used a sail fabric called F3, developed for its winning 1992 campaign. Light and strong, both types of sail use carbon fiber and Mylar(TM) film.

3DL technology, developed by North Sails, Milford, CT, produces a sail in one continuous piece. Traditional sails consist of panels sewn together.

North molds sails on a computer-controlled mold by first putting down a sheet of Mylar that's trimmed to be a little bit bigger than the actual sail. Then a computer-controlled gantry with a pod comes down and applies carefully tensioned adhesive-coated Kevlar threads to the film. For the America's Cup teams, says Smith, North first lays down Kevlar threads and then carbon fiber.

After applying the fiber, the system places another piece of Mylar on top of it. A high-intensity heat lamp then moves over the sail-which remains on the mold-to heat-cure it.

Until this race, 3DL sails just used Kevlar fibers. "Kevlar acts as a safety net to hold the sail together if the carbon fails," notes Marshall.

Team Dennis Conner and PACT 95 each have their own sail-design team. Many of the designers on these teams are North personnel, and they're sworn to secrecy. "After the cup, the North people get together and share their secrets and it benefits North immensely," says Smith.

One advantage of 3DL is that for its strength, it's lighter than traditional sails. A boat can cover the wind range more effectively with 3DL sails because they're lighter and assume their design shape better in less wind than does a panel sail.

America3's sail fabric is called Cubinfiber-the trade name is F3. It's made by F3 Technologies, while Sobstad Sailmakers produces the sails. The materials used are Mylar film, carbon fiber, and Allied Chemicals' Spectra fiber.

Like 3DL, F3 fabric is not woven. It's laid out with layers of Spectra in the vertical, horizontal, and off-threadline directions. On top, carbon fiber runs in the horizontal and off-threadline directions. Next the sailmakers place fabric laminated with thin Mylar film on each side. In 1992, they autoclaved the fabric--a more expensive process. The 54-inch-wide material is cut on a laser cutter, and workers assemble the sails like conventional panel sails.

Advantages of Cubinfiber include its light weight and good weight/strength ratio. "In 1992, some teams had problems with the carbon fibers in the sails breaking, but the way we cure the fabric makes it very durable," notes Per Anderson, director of sail development for America3.

Both sail technologies are available for other sailboats, and the companies hope to ramp up production after the race.

Electronics keep data flowing

Both the boats and the land-based compounds of the three defending syndicates teem with electronics. Products used include sensors, laser rangefinders, GPS receivers, computers, fax modems, cellular phones, radios, and lots of other communications equipment.

Team Dennis Conner and PACT 95 use sensors from Ockam Instruments, Milford, CT. (America3 uses custom instrumentation.) These devices scope out boat speed, apparent and true wind speed, wind direction, apparent wind angle, heading, opposite tack, target speed, time, waypoint bearing, waypoint range, and opponent bearing and range.

PACT 95 also uses an Ockam data collection system. Boat sensors send data to an on-board Ockam computer that interfaces to an on-board telemetry system from Ford. The system transmits data to a tender boat for analysis and tactical planning, to the VIP spectator boats, and to PACT 95 Mission Control for storage, analysis, and display.

Open to the public, Mission Control is a tent outside PACT 95 headquarters. It shows live onboard camera footage and real-time displays of racing progress via telemetry. Based on Ford's racing telemetry, the setup includes a 60-inch screen for video and four other screens for graphics that show target speed, boat speed, wind direction, and boat heading.

Incremental improvements. "The kinds of instruments and sensors are basically the same as in 1992, but they're all being incrementally improved," observes Robert Hopkins, navigator for Young America and a veteran of four America's Cup races.

PACT 95 started with Ockam's sensor package, then added other high-tech goodies such as differential GPS (Global Positioning System) receivers from Trimble that can peg the boat's position to within one meter. The team studies boat maneuverability by looking at the track the GPS says the boat sailed. Results can aid keel or rudder design.

Litton Industries loaned PACT 95 a $200,000 inertial navigation unit with gyroscopes and accelerometers. Airliners have used this technology for 20 years, but this application marks its first use in an America's Cup race. The unit detects the motion of the boat in all six degrees of freedom and logs the data. Designers use this information to analyze the motion of the boat in the sea. Comparing the real-world data to computer predictions and other data from rough-water tow-tank model tests validates their software, and helps improve hull and appendage design.

One new technology for Young America is a pistol-shaped laser rangefinder from Laser Atlanta. The Atlanta, GA-based company's real job is making laser speed traps for police departments. The finder is coupled with a digital compass from KVH Industries, Middletown, RI. Pointing and shooting it at a competing boat gives Young America's crew the exact range and bearing of other boat.

Ship ahoy! Motorola is a sponsor of America3 and supplied the team with a wide-area communications system. The system includes a new 900-MHz, 5-channel radio relay system on Point Loma. It lets crew members and race officials in boats on the ocean race course use low-wattage two-way radios to communicate with people at the land-based sailing compound. Essentially, the relay station takes the low-power radio signals from the boats and amplifies them so they are received loud and clear at the compound. Without the system, such communications would be impossible because the high land mass of Point Loma would cut off the radio transmissions.

In addition America3 uses a secured channel to send verbal and other communication data to its base station. Radio helps the crew with weather forecasting, navigation, on-board electronics and computers, and communication about changing sailing conditions. It also lets the crew talk with tender and chase boats.

The Young America crew leases scrambled Motorola 2-way radios to talk among themselves. Marine VHS radios enable them to speak with other boats. Cell phones are also used to fax messages to a tender boat. Team Dennis Conner uses much the same technology.

Says Young America's Hopkins: "During practice we communicate constantly. But there's a rule: From five minutes before the start of the race until the end of the race there can be no communication with the outside world. So we throw all the walkie-talkies and cell phones into a waterproof plastic container and toss it overboard. We're on our own from there."

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