I’ve written about the skating, tobogganing and curling, but there’s a major winter sport I’ve yet to explore (and no, it’s not competitive car-boosting). That’s probably because, while I’ve skated, tobogganed and curled, I have yet to strap two long, skinny pieces of fiberglass to my feet and go careening down a mountain or sliding around the lake. But I’ve been thinking about giving it a try.
Skiing has been around for a long, long time. Greek historians mention various kinds of devices used to enable individuals to travel more easily over the snow, as do Norse myths. Ancient skis have even been found in bogs in Sweden and Finland. They consist of elongated curved frames covered with leather–and they’re between 4,000 and 5,000 years old.
In those days, skis weren’t for sport, they were for transportation. Skis and snowshoes work the same way to keep their wearer from sinking into the snow; they spread his weight out over a much greater area. A 90-kilogram man standing on his own two feet in the snow obviously exerts a much greater weight per square centimetre on the snow’s surface than a 90-kilogram man standing on two boards two metres long. But skis have an advantage over snowshoes: they slide. Sliding over the snow is obviously far less tiring than wading through it, plus skis, unlike snowshoes, don’t require you to walk like a constipated duck. This was undoubtedly what led Norwegian explorer Fridtjof Nansen to use skis to traverse Greenland in 1888. His account of his expedition was so popular that sport skiing suddenly began spreading across Europe, whereas before that time it was pretty well limited to Norway.
Skiing comes in various flavors. Nordic skiing is cross-country skiing, skiing over flat or gently undulating country. (It does have a wild-and-crazy side, however: ski-jumping, hurtling down a ramp and flying up to a hundred metres through the air.) Alpine skiing is what Nordic skiing became when the sport made it into the Alps; it’s skiing down steep slopes. Freestyle skiing relates to the other forms somewhat like figure skating relates to hockey. The emphasis is on acrobatic skills.
All forms of skiing share a few basic scientific principles. Ice melts when put under pressure. A ski, pressed down by the weight of the skier, slightly melts the snow under it, creating a thin film of water. This thin film of water lubricates the passage of the ski over the snow, reducing friction.
Thanks to this reduced friction, the skier can glide across the snow at a high rate of speed. When he decides to turn, he angles and tilts the skis. The edges bite into the snow, both slowing his forward momentum and altering his direction: it’s easier for him to move in the direction the skis are pointing than to overcome the friction between the ski-edge and the snow. This process is aided by ski-poles, extensions of the skier’s arms that help to give him stability and, in the case of cross-country skiing, supply additional forward thrust.
An important element of modern skiing is ski wax, a thin layer of which is applied to the bottom of the skis. Waxes repel water, and since the skis move on a thin layer of water, applying wax to the bottom of the skis makes them glide even more smoothly.
But it’s a bit more complicated than that, as Tim Chicilo down at the Ski Shop explained to me, especially in cross-country skiing.
Cross-country skis actually have two kinds of waxes on them, glide wax and grip wax. Glide wax is harder, designed to enhance slipperiness; grip wax is soft and rather tacky, designed to grab onto the snow more. (Grip waxes are tacky because they contain a certain amount of “klister,” the grippiest wax of all. Most of the waxes are quite solid at room temperature, but klister has a consistency more like soft glue.)
Cross-country skis are cambered; ordinarily, the middle section doesn’t even touch the ground. Grip wax is applied in this “wax pocket”; glide wax is applied to the rest of the ski. When a skier pushes down on the ski to turn, the wax pocket comes into contact with the snow, and the grip wax helps him maneuver.
Different kinds of waxes are applied for different weather and snow conditions. When the weather is very warm, a relatively thick layer of water builds up under the ski–more than you want. In that kind of weather, soft glide wax is used, because the snow will gouge channels in it that allow excess water to escape. When the weather is cold, the layer of water is very thin, so a hard glide wax is used to trap all of it beneath the ski. (Below about -20 Celsius, no layer of water forms at all, and it becomes much harder to ski, just as it becomes harder to skate in really cold weather.)
The choice of grip wax is determined more by snow conditions. Fresh snow has lots of jagged edges, so it’s easier to grip, but in old snow, the jagged edges have been worn off, either by melting or by previous skiers, until sometimes it becomes almost like skiing on millions of tiny ball bearings. For that kind of snow, you need a much grippier grip wax.
Cross-country skiing is an excellent form of exercise because it exercises many muscle groups. Alpine skiing is also physically challenging, but at least you don’t have to provide your own forward momentum–gravity does that.
Downhill skiers plunge down the slope at up to 130 kilometres an hour; speed skiers may reach 220 kilometres an hour. That’s about as much forward momentum as anyone could possibly want. It’s also a lot of wind in your face. Skiers therefore adopt a low “tuck” which minimizes air resistance. In fact, a downhill skier in tuck position is more streamlined than most sports cars.
Speed skier just hurtle down the mountainside, but other Alpine skiers have to turn. A downhill skier making a turn puts a strain 2 1/2 times his body weight on his inside leg, due to the combination of gravitation and centrifugal forces.
Let’s see. I weigh more than 100 kilograms, so that’s 250 kilograms on that knee that’s been bothering me off and on since…Hmm.
Anyone for checkers?
