Olympic snowboarding gold medalist Kelly Clark made history in 2011. At January's Winter X Games, she uncorked the first 1080—three full rotations—executed by a woman in competition. At the 29th Burton U.S. Open Snowboarding Championship in March, she hit the trick again. Before winning her fifth Open title, Clark did a 900 for our cameras; the trick lasts 2 seconds and was captured in 23 frames (only 13 are shown here). Three decades of advances in half-pipe engineering, physical training, and board design have allowed snowboarders to fly higher and spin more quickly. With Clark's assistance, we break down the mechanics behind snowboarding's new heights.
In the pipe, riders can travel up to 40 mph, but they have to fight the forces that sap speed. As Clark moves along the arc in the transition from flat bottom to vertical wall, centripetal force pushes her down. Harnessing that force adds speed, but if she buckles, Clark's body absorbs kinetic energy and slows down. As she approaches the pipe's transition—where centripetal force is the highest—Clark pumps her legs. This stiffens her body and causes her to exert more force on the ground, which, according to Newton's third law of motion, pushes back and boosts her speed.
2: LAUNCH & FLIGHT
"One of the biggest misconceptions is people liken it to a vertical jump," says Jon Turnbull, the winter performance program manager at the New Zealand Academy of Sport. If snowboarders jumped like basketball players, they'd fly away from the wall and toward the center of the pipe, instead of up above the lip. Clark generates height by rotating her body as she reaches the lip, which creates vertical velocity. Once in the air, she pulls her arms close to her body to increase rotation and spin in a fluid motion. "The more compact I am," she says, "the faster I spin."
Clark spots her landing two-thirds through a trick. When landing, she must "?'pull the chute'—you make yourself as big as you can to slow your rotation," she says. To maintain speed into the next trick, she reenters the pipe as high on the wall as possible while angling her board down the pipe to take advantage of its 18-degree pitch. When she lands, Clark must keep her body rigid; flexing her knees would absorb energy and decrease her speed. "She's maintaining her gravitational potential energy from a body of flight and changing it to kinetic energy," Turnbull says.
Once just crude wooden planks, snowboards have evolved into precisely engineered pieces of equipment. The core is composed of small wooden strips arranged to improve strength and flexibility. Because wood is strongest when bending with the grain, the strips near each end run parallel to the board's length, adding spring. In the center, the grain runs perpendicular so it flexes as the rider leans forward and back. Fiberglass and carbon fiber add strength, and a Teflon-infused epoxy reduces friction. At an event, techs hone a board's edges and bake wax into it overnight: On cold, dry days, when snow is icy, a hard wax is used; on warm, wet days, a softer wax applied with texture prevents suction. "The board base is absorbent," Clark says. "The more it's waxed, the faster it gets."