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 America 3-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