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HOW SKIS WORK "The story goes that a world-champion ski racer was out with skiing with
his son. Son had on a pair of kid's skis with Mickey Mouse graphics, and Son was
horsing the skis around the turns with lots of body movements and arm swinging.
Dad said, "Now, Son, let Mickey do the work!" It is said that at the
end of a ski day, your skis should be tired from working, not you. In the snow/skis/skier system, note that the skis come between the snow and the skier. Once on a given area of snow, the skier can't do a lot about its character, and the skier is pretty much stuck to the skis by the boots and bindings. So if the skier is to influence what is to happen, it has to be by somehow positioning the skis so they will interact with the snow and make the skier go this way or that, and faster or slower. We all know generally what skis look like, but take a close look. "What is the most important part of the ski?" is a question sometimes asked in ski instructors' exams when they try out for certification. This is a loaded question. Anyone who has broken a ski tip while out in the woods will say the upturned end, or shovel, is the most important, for it allows the ski to run up over obstacles instead of diving into them. Beginning skiers may not notice some other features that more advanced skiers would. When placed on a flat surface, like a solid floor, the skis arch upward in the middle, their bases touching only at tip and tail. Why are they made this way? When you stand on the middle of the ski, you flatten it to the floor and your weight is then evenly distributed along the ski's length instead of just mainly under your foot as would otherwise have happened. (It's the same principles engineers apply when they pre-stress bridge spans or heavy-load truck beds; these arch upward, too, until loads flatten them.)
A skier also knows that the sides, or edges, of the skis are crucial. A ski that is flat on the snow will slide where it wants. When a ski is tipped on its side, its edges dig into the snow, keeping us from sliding where we don't want to go--or getting us to slide where we do. The edges are even lined with squared-off steel to help them bite into the snow better. Some advanced skiers might not notice what more expert skiers should about another ski characteristic. Look down on a ski's top surface from above. Notice the ski is narrower under the foot area than at its tip or tail. Why? Setting the ski on the floor again, bottom down, first lift up one side of the ski. This will put the ski at an angle to the floor. Now, keeping the ski angled to the floor, and ensuring the tip and tail don't slide on the floor, press downward on the ski's middle, causing the ski to bend until the lower side of the ski touches the floor. If you followed these directions, and your ski is normal, the ski's line of contact on the floor will be an arc. The more you tilt the ski to a higher angle with the floor, the more of an arc you will get when you press the middle down again. Now do the same thing but on a rug. While still holding the ski so the arced edge presses against the floor, push the ski forward and watch the ski track along its edge in an arc. This shows how a tilted ski can turn us more or less depending on its tilt and therefore how much it can bend into an arc. (Be careful not to cut the rug!) If your rug has a bit of depth, it will be like snow in that the higher the ski is tilted, the more of its weight is put on a smaller area, increasing pressure on the edge of the ski and causing it to bite into the rug--or snow--more deeply. HOW BALANCE MAKES SKIS WORK. While learning "How Skis Work", we kept the skis on a flat floor. That's not where we use skis, however. We use them on hillsides. To make the skis work the way they are designed to, then, we must position our bodies to produce the same forces as in the flat-floor example. Our forces must be centered on the skis and perpendicular to them, no matter how the skis may slope or tilt. Imagine the gyrations we must do in our bodies to always have our main line of force perpendicular to our skis--especially when the skis are tilted. If the skis are flat to the snow and going down a steep slope, for instance, our bodies must be tilted forward from vertical. If the skis are tilted to the side, our lower legs must also tilt to the side, and somehow we must keep from falling over. To assume such positions is not possible while standing still in normal gravity mode. Only while we are moving and new forces of motion come into play can we manage to place ourselves in seemingly gravity-defying postures. Perhaps this is a little like a car going around a curve at high speed; the road-builders often bank up the roadway on one side so the car tilts inward from vertical but stays more nearly perpendicular to the road surface, and is less likely to fly off the curve's outside. And so when we speak of balance in skiing, we are not talking of the more usual balance against just gravity, but a much more complex and dynamic type. Learning these new balance positions and experimenting with them constitutes both the joy and the frustrations of learning to ski. For those who enjoy motion, the journey is always fun. For some, however, who do not overcome a distaste, or even fear, of sliding, the journey will be more limited. One beginning skier confided to her instructor, "It's the sliding part I don't like." There is a lot of humor in her utterance, yet most skiers in spite of their efforts to overcome, at some point will find that it's fear of "the sliding part" that ultimately limits their advance in skiing.
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Skiing Web Manual "Skiing is a Sliding Sport"
Note the lengthwise bend of the tipped skis.