- This article concerns the skis used in skiing. For the place in Norway, see Ski, Norway.
A ski is a long flat device worn on the feet designed to help the wearer slide over snow. Originally intended as an aid to travel in snowy regions, they are now primarily used for recreational and sporting purposes. Also, a ski may denote a similar device used for other purposes than skiing, e.g., for steering snowmobiles.
Snow skis glide on snow because downward pressure, as well as heat from surface friction, melts the snow directly under the ski. This creates a very thin layer of water directly under the ski upon which the ski glides. This is why if there is freezing rain that freezes to the bottom of the ski (perhaps when carrying the ski), when set down on the snow, won't glide until the ice wears off or is knocked off. Ski wax is used to increase the freezing point of water on the base of the ski, easing the creation of the water layer.
Construction
Skis were originally wooden planks made from a single piece of wood. They are now usually made from a complex assembly of components including glass fiber, Kevlar, Titanium or composite materials, though many may still contain a wooden core.
Most skis are long and thin, pointed and curved upwards at the front to prevent it from digging into the snow. The user is attached by a bindings to the skier's ski boots.
Types of ski Many types of skis exist, all designed for use different situations, of which the following are a selection.
Downhill ski Downhill skis are "shaped" (when viewed from above or below, the center or "waist" is narrower than the tip or tail, and the cut from tip through waist to tail follows either a parabolic curve, or an arc, on either side of the ski) to promote easy turning. Most varieties of skis have a metal edge running the length of the sides that once sharpened allow the ski to grip more effectively on hard packed snow and ice.
By setting the ski at an angle so that the edge cuts into the snow, the ski will follow the arc and hence turn the skier, a practice known as carving a turn. Faced by competition from snowboarding, during the 1990s this shaping of the ski became significantly more pronounced to make it both easier for skiers to carve turns, and to dramatically increase the turning sensation experienced. Such skis were once termed carving skis, or shaped skis or parabolic skis to differentiate them from the more traditional straighter skis, but nearly all modern skis have this more pronounced shape now. For other turning techniques, see Skiing.
The ski binding anchors the foot firmly to the ski at heel and toe. As a safety feature, it is spring-loaded, detaching the ski from the foot in case excessive force is applied. The ski is turned by applying a mixture of pressure, rotation and angle.
Twin-tip ski Twin-tip skis, also known as "freestyle skis", are skis with turned-up ends at both the front and rear. These special skis make it easier to ski with ones back facing downhill, allowing reversed take-offs and landings when performing aerial maneuvers. Only recently have they become popular.
Alpine ski touring ski Alpine ski touring ski. This type of ski is ususally a modified light-weight downhill ski with an alpine touring binding. Like the backcountry ski it is designed for unbroken snow. For climbing of steep slopes skins (originally made from the fur of seals, but now made of synthetic materials) can be attached at the base of the ski and the binding opened at the heel. For skiing downhill the bindings are locked. The ski is used with alpine touring boots which are hard but lighter than downhill skiing boots.
Monoski The monoski is a singe ski which both feet attaches to. Most common in the eighties but is (by 2005) still used by enthusiasts. Many argue that the monoski is better in powder snow because of its width.
Telemark ski Telemark ski. A downhill or touring ski, where the binding attaches only at the toe. The Telemark ski was the first ski with an inwards-turned waist which made it much easier for skiers to turn. It was pioneered by Sondre Norheim of Telemark, Norway. The fact that the foot is only attached to the ski at the toes, means that specialised more flexible ski boots are used, and a specific turning technique involving pushing one foot forward and lifting the heel of the other foot is used.
Cross-country ski Cross-country skis are very light and narrow, and usually have quite straight edges, though some newer skis have slight sidecut. The boots attach to the bindings at the toes only, there are three binding systems currently used, Rottefella's NNN and Salomons SNS profil and SNS pilot. The ski bases are waxed to reduce friction during forward motion, and kick wax can also be applied to get adhesion when going uphill. Some waxless models may have patterns on the bottom to increase the friction when the ski slides backward. There are two major techniques, classical (traditional striding) and freestyle or skating which was developed in the 1980s. Skating skis are shorter than classical skis and do not need grip wax. Skating is also the technique used in biathlons.
Backcountry ski Skis for mountain/backcountry/cross-country free range skiing which are designed for skiing on unbroken snow, where an established track is lacking. These are characteristically quite wide, and with cable bindings to provide general sturdyness, and to better extract ones feet from deep snowbanks, in case it should be impossible to reach the bindings by hand. This is also the model used by military forces trained to fight in winter conditions, and the most closely related to the historical ski.
Ski jumping ski Skis for ski jumping. Long and wide skis, with bindings attaching at the toe.
Snowblade A type of ski that is much shorter than a standard ski, and is a cross between a ski and an Ice skate.
See also - [1] (http://www.snowlife.org.uk)
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