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How Skis Work

Posted February 22, 2010 12:01 AM by JGstott

Not so long ago, skis were wooden planks with one end turned up and grease or wax smeared on the bottom to help them slide. In the 1990s, under the influence of snowboarding, there was a revolution in ski design, producing the basic principles and wide variety of applications we see on the slopes today.

Just for the record, the basic principles of manipulating a snowboard and manipulating a pair of skis are identical. The difference is all in the physiology driven by the position of the human attached to the gear in question. In this blog entry, I'll focuses on skis; however, the ideas can be applied to snowboarding as well.

The revolution in ski design has allowed recreational skiers to ski more comfortably, efficiently and in a wider range of conditions than allowed for by previous designs, as well as allowing ski racing to push the envelope of speed and maneuverability in new ways.

Four Basic Components

There are four basic components to the design of a ski: "sidecut" - the difference in width of the tip, tail and waist of a ski; overall width - the height at which the skier is "lifted" off the ski; stiffness; and camber. The variations in these factors influence how a ski performs, and skis are designed to manipulate these factors for different purposes.

Today's skis are generally wider, contain more "sidecut", and lift the skier higher off the "deck" or top of the ski. In World Cup and Olympic Racing, governed by the FIS (Federation Internationale du Ski), there are rules about the first three design components of skis, which are intended to even out competition and make technology less of a factor, much like in auto racing. Also like auto racing, manufacturers tend to build the skis to the outer limits of the rules, making the outward differences between skis a matter of degree and construction technique.

Ski Characteristics

In combination with gravity and the skier's manipulations, these four components help to make a ski turn. Sidecut, the arc created from the difference in width of the tip, waist and tail of a ski, influences the general radius of a turn that a particular ski is designed for. Skis meant for Slalom racing tend to be somewhat shorter, with more sidecut (tighter arc, tighter turn). In the high-speed events (Super-g and Downhill), the skis tend to be longer and have somewhat less radical sidecut (longer = more stable at high speed; less sidecut = longer arc, less tight turns).

Skiers "turn" skis by moving their bodies to apply the ski in different reactions to gravity. Movements that allow gravity more effect make the ski/skier go faster, movements that put the ski in opposition to gravity slow the ski/skier down. There are three general movements that skiers use to manipulate a ski: twist, or rotation around the vertical axis; tilt, or turning a ski up on its side (called "angulation"); and applying or releasing pressure to the ski (skiers also adjust where on the ski the center of pressure is, by moving their center of gravity forward and backward over the ski).

That is really it. There isn't anything else you can do to a ski - twist, tilt, push. Combining those forces makes a ski turn or not.

About the Author

Jay Stott is a writer, photographer, teacher and general 'ner-do-well. Before his current career arc, he spent 15 years teaching skiing and leading adventurers in the wilds of the American West. He currently lives in North Central Colorado. Visit him at jgstottphotography.com.

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Re: How Skis Work

02/23/2010 6:55 PM

Not a bad summary.

Many, however, would argue that the era of the modern ski started in the late 50's and early 60's, when wood was phased out and metal and composite skis were introduced. Lengths have generally been reduced over the years, although downhill racing skis are still quite long. In recent years, skis have become noticeably wider, and (particularly for recreational use) shorter.

The obvious trait missing from the "four basic components" is length. Also the definition of "overall width - the height at which the skier is lifted off the ski" is peculiar.

The FIS dos not restrict ski construction in quite the way described, namely that "there are rules about the first three design components of skis, which are intended to even out competition and make technology less of a factor." If those "first three" are the ones previously listed (sidecut, overall width, and stiffness) then this statement is misleading. A minimum radius, but no maximum radius is specified for sidecut. Only a minimum width under the foot area is specified. Stiffness is completely unrestricted. Length, which is not listed as one of the four components in the original post, is restricted to certain minimums.

But given that camber, stiffness, mass, construction materials, running surface, torsion box, core, edges, lengths and widths beyond minimums, and top surface are all completely unrestricted, it is only vaguely true that the rules "are intended to even out competition and make technology less of a factor, much like in auto racing." Skis can be built to within the specification that can range from nearly unskiable to superb.

The FIS rules are here.

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