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Tricks of The Trade
Shannon Brownlee
January 27, 1988
Ever wondered what keeps a ski jumper flying or a luger on track? Here are some answers
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January 27, 1988

Tricks Of The Trade

Ever wondered what keeps a ski jumper flying or a luger on track? Here are some answers

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Even in this high-tech age the length of a ski jumper's leap is still measured by the naked eye. During competition, officials stand on either side of the hill, at carefully measured one-meter intervals, watching the skier's feet as he flies through the air. When the skier lands, the official closest to the touchdown point raises his hand to indicate the distance of the jump.

During the Sarajevo Games, 114-pound Jens Weissflog of East Germany was likened to "a piece of paper in the wind" when he won the 70-meter jump, but a better analogy would have been a paper airplane, because a ski jumper gets a similar sort of aerodynamic lift. The skier-inflight gets lift by holding his body at about a 35-degree angle over his skis. As he flies, the air is drawn around his body and skis, causing corkscrew vortices to form (see below). The vortices decrease air pressure over the skier's back and increase pressure below his chest. The pressure differential pushes him upward slightly, keeping him from falling like a stone.

HEAD START

It may look as if a skier is trying to go down the hill on his face instead of his skis when he bursts headlong out of the starting gate (below), but he's actually shaving hundredths of a second off his time. By launching his torso out over the run, the skier is already plummeting downhill by the time his legs knock aside the wand that starts the timer.

At the bottom of the bill, the timer stops when the skier breaks an electronic beam at about knee height. By lifting the tips of his skis, a clever skier can make the skis pass through the beam ahead of his legs.

Lugers have similar tricks. The timer is triggered at the start of the run and stopped at the end by electronic beams aimed three inches above the ice. Many lugers draw their knees up before hitting the beam at the top—thus delaying the timer's start by a fraction of a second—and extend their toes as far in front of the sled as possible at the bottom of the run.

BOBBING ALONG

Before doing an $850,000 bobsled design for the U.S. team, engineers at Airflow Sciences Corp., a fluid-mechanics consulting firm in Livonia, Mich., conducted computer simulations to find out where they should concentrate their efforts. They simulated hundreds of bobsled runs, varying such things as the weight of the sled, starting speed, friction on the sled's runners and aerodynamic drag. To their surprise, it is the athletes who matter most. More important than sled design is push time—how long it takes the sledders to propel their craft and leap into it over the 50-meter starting run. As little as a 10th of a second off push time shaves a quarter to a third of a second off run time, which is plenty of time to determine who will win—or lose—a gold medal.

The engineers' simulations didn't take into account the trickiest part of launching a bobsled—jumping into it without scratching your teammates with the hundreds of needles that project from the soles of your sledding shoes. The needles grip the ice during push time.

KING TUCK

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