Main article: History of skiing
The original Nordic ski technology was improved during the early twentieth century so that skiers could make turns at higher speeds. New ski and binding designs, coupled with the introduction of ski lifts to carry skiers high up on mountains, enabled the development of today’s most prominent category of the sport, alpine skiing.
[edit] 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, other polymers or composite materials, though many may still contain wooden cores.

Most skis are long and thin, pointed and curved upwards at the front to prevent the ski from digging into the snow. The user is attached by bindings which in turn hold the ski boots. Beginning in the early 2000s, many ski manufacturers began designing their skis and bindings together, creating an ‘integrated binding system.’ These systems serve two purposes. First, they often use a railroad track style design, to allow the toe and heel pieces to slide, which in turn allows the ski to flex deeply, without a flat spot underfoot, caused by the presence of a binding. Second, it forces the consumer to purchase both skis and bindings from the same manufacturer, increasing sales.
[edit] Types of ski
Many types of skis exist, all designed for different situations, of which the following are a selection.
[edit] Alpine ski
Like all skis, the original alpine “downhill” skis were little more than glorified planks of wood. Later on metal edges were added to better grip the snow and ice of a ski trail. Through the years, downhill ski construction has become much more sophisticated. The use of composite materials, such as Carbon-Kevlar, made skis stronger, lighter, and more durable. In the late 1980s and early 1990s, spearheaded by ELAN, manufacturers began producing parabolic “shaped” skis (when viewed from above or below, the center or “waist” is narrower than the tip or tail). Virtually all modern skis are made with some degree of side cut today. The more dramatic the difference between the width of the tip waist and tail, coupled with the length stiffness and camber of the ski, the shorter radius turns the ski is capable of creating. Skis used in the downhill race events are long with a subtle side cut as they are built for speed and wide fast turns. Slalom skis, as well as many recreational skis are shorter with a greater side cut to facilitate tighter, easier turns.

The ski is turned by applying pressure, rotation and edge angle. When the ski is set at an angle the edge cuts into the snow, the ski will follow the arc and hence turn the skier; a practice known as carving a turn. While old fashioned “straight skis” which had no side-cut could be used to carve turns, it required huge leg strength to generate the enormous pressure necessary to bend them into a curved shape for carving. This shape is called “reverse camber”. Now, when one of the modern, hourglass-shaped skis is tilted over on to its edge, a gap is created between the ground and the middle of the ski, just under the binding as only the tip and the tail touch the snow. Then, as the skier gently applies pressure, the ski bends easily into reverse camber. Influenced by snowboarding, during the 1990s this shaping of the ski became significantly more pronounced to make it easier for skiers to carve turns. This makes skiing much easier to learn, because the skis turn by themselves when placed on edge. 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 recreational skis are produced with some degree of side-cut.
[edit] See also
Physics of skiing
FIS equipment tolerances
For other turning techniques, see Skiing.
A history of the modern shaped ski
The ski binding anchors the foot firmly to the ski at heel and toe. As a safety feature, it is spring-loaded to detach the ski from the foot once a set pressure tolerance is reached. Modern bindings utilize a DIN spring system to minimize the amount of force applied to joints such as the knee during backward twisting falls.
[edit] Twin-tip ski
 
The Böksta Runestone is believed to depic the Viking god Ullr with his skis and his bow.Twin-tip skis are skis with turned-up ends at both the front and rear. They make it easier to ski with one’s back facing downhill, allowing reversed take-offs and landings when performing aerial maneuvers. The turned-up tail allows less application of aft pressure on the ski, causing it to release from a turn earlier than a non-twin-tip ski. Twin-tip skis are generally wider at the tip, tail, and underfoot and constructed of softer materials to cushion landings. Bindings are typically mounted closer to the center of the ski to facilitate the balance of fore and aft pressure, while skiing backwards or “switch”, bindings are built lower to the ski for easy rail sliding. Some skis are also manufactured with special materials or a different sidecut design under and close to the foot to facilitate rail sliding (also referred to as “Jibbing”). The popularity explosion of twin-tip skis created a push for the inclusion of more terrain park elements at ski areas across the globe. In the past five years twin tips have become popular among youth skiers, ages 14-21. Once considered a passing fad, twin-tip skis have become a staple ski in the product line of all major ski-producing companies worldwide, with a few specializing in only twin tips. Line Skis, started by Jason Levinthal, is the first company to market only twin-tip skis. The first twin-tip ski was the Olin Mark IV Comp introduced in 1974. The first company to successfully market a twin-tip ski was Salomon, with their 1080 ski.
Romantic 1903 rendition of medieval Russian soldiers’ use of skis to facilitate their movement during winter campaigns.
[edit] Alpine touring ski
The Alpine touring ski is usually 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.
[edit] Monoski
The monoski is a single, double-width ski that attaches by a common DIN binding interface to modern front entry boots. More common in use during a brief boom in the 80s, today the monoski is used by only a few thousand enthusiasts world-wide. The monoski is produced by only half a dozen companies world-wide in limited quantities. Due to its extra width and flotation in deep snow, enthusiasts claim it superior as a powder ski.
[edit] Telemark ski
The Telemark ski is 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 specialized 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.
[edit] 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 most often used; Rottefella’s NNN and Salomon’s 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.
[edit] 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 sturdiness, 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. The widest backcountry skis are often called ‘Big Mountain’ skis.
[edit] Mogul ski
These skis are specifically designed for moguls. They are typically softer, less wide and less waisted compared to a common carving ski.
[edit] Ski jumping ski
Skis for ski jumping. Long and wide skis, with bindings attaching at the toe.
[edit] See also
 
RollerskisSkiing and skiing topics – further details of skis related to particular variations of ski sport
History of skiing – the ancient history of skis
Roller skiing – a type of inline skate that resembles a ski
Snowboarding – a newer way to ride on snow, on one large board rather than two skis
Skiboarding – very short, twintip skis
Ski boot – specially designed boots for skiing
ski patrol – patrolers on skis