Ski - Construction

Construction

Skis have undergone several leaps in design, starting with hand-carved single pieces of wood and evolving into the modern torsion-box design. These can be generally classified into classic wooden, laminated wood, laminated metal and fibreglass, torsion box, and cap designs.

Classic wooden

The classical wooden ski consists of a single long piece of suitable wood that is hand-carved to produce the required shape. Early designs were generally rectangular in cross-section, with the tip bent up through the application of steam. Over time the designs changed, and skis were thinned out to the sides, or featured prominent ridges down the center.

Wood laminates

The perfect wood for a ski is light, flexible in length and stiff in cross-section. Such a wood does not exist. Starting in the 1940s, skis built up from a number of different types of wood glued together became common. By selecting different woods in different areas, the flex pattern could be better controlled. The glue between the pieces of wood also added to the torsional stiffness, twisting the ski along its longitudinal axis requires the sections of wood to move relative to each other, but the glue resisted this motion better than the wood itself. This method also lowered the material costs, as it is generally easier to find smaller pieces of wood, and this was a serious concern when hardwood stocks in Europe depleted.

Edges

In the 1940s, strips of steel were screwed to the bottom edges of the ski on either side. These maintained a sharp edge and allowed the ski to bite into the snow or ice when they were edged. Simple variations on the theme have remained in use to this day.

Metal laminates

Although a number of companies had experimented with all-aluminum skis in the 1940s, none of these proved practical. It was Howard Head's experiments combining aluminum and conventional wood designs that solved the problem. The Head Standard sandwiched a conventional wood laminate ski between two thin layers of aluminum sheet on the top and bottom. When the ski was torqued, the position of the aluminum sheets above and below the axis of rotation required them to slide sideways relative to the core, something that was resisted by the glue along the entire surface of the sheet. The Standard was dramatically stiffer in rotation, and so greatly improved edging and turning that it was known as "The Cheater".

Fibreglass laminates

One disadvantage of the metal laminates was that they were very "springy" and tended to chatter on bumpy surfaces and especially at high speeds. As late as the 1960s, racers still used conventional all-wood designs. Fibreglass, first widely used in the 1940s, offered an alternative material offered vibration damping, as well as allowing the flex pattern to be controlled along the length of the ski. Several such designs were introduced in the 1950s but the first successful one was the 1959 Toni Sailer Fibreglaski by Fred Langendorf and Art Molnar of Montreal. Fibreglass laminates were made much more famous by the Kniessl White Star and Rossignol Strato during the 1960s, and by the late 1960s they were as common as metal.

Torsion box

The Dynamic VR7 introduced a new construction method in which a smaller wooden core was wrapped in wet fibreglass, as opposed to pre-dried sheets being glued to the core. The result was a torsion box, which made the ski much stronger. The VR7, and its more famous follow-on VR17, was the first fibreglass ski that could be used for mens racing, and quickly took over that market. Over time, materials for both the core and torsion box have changed, with wood, various plastic foams, fibreglass, kevlar and carbon fiber all being used in different designs. Torsion box designs continue to dominate cross-country ski designs, but is less common for alpine and ski touring.

Cap skis

During the 1980s, Bucky Kashiwa developed a new construction technique using a rolled stainless steel sheet forming three sides of a torsion box over a wooden core, with the base of the ski forming the bottom. Introduced in 1989, the Volant skis proved expensive to produce, and in spite of numerous positive reviews the company never able to become profitable. In 1990, the Rossignol S9000 took the same basic concept but replaced the steel with plastics, producing a design they called "monocoque". Now referred to as the "cap ski" design, the concept eliminates the need to wrap the core and replaces this with a single-step process that is much less expensive to produce. Cap ski construction dominates alpine ski construction today.

Beginning in the early 2000s, many ski manufacturers began designing skis and bindings together, creating an integrated binding system. These systems serve three purposes. Firstly, they often use a railroad track design, to allow the toe and heel pieces to slide, which in turn allows the ski to flex deeply, without a non-flexing spot underfoot due to the binding. Secondly, it gives the skier a better control on his skis, since the binding is not only screwed on the ski, but integrated in the ski core via inserts. Thirdly, it requires the consumer to purchase both skis and bindings from the same manufacturer due to the proprietary nature of the system, thus increasing sales.