Several years ago, Pete Wagner asked me to contribute some thoughts on the art and science of ski design. The resulting discussion lived for several years on the Wagner Custom website but got lost in a redesign, so I’m summarizing it here.
Buying skis has become both easier and tougher than it was 20 years ago. Before 1990, there were about 35 ski factories around the world, and they all made essentially the same product. The design of skis had been more or less frozen for several decades. The classic slalom ski was 205cm for men and 190cm for women, shaped 85-65-75mm. This gave roughly a 40-meter sidecut radius and a bearing surface of about 1300 square centimeters. The classic giant slalom ski was 210cm for men and 200cm for women, shaped 87-68-77mm — roughly 50 meters radius and a bearing surface of 1400 square centimeters. The big differences in skis were not in shape and size, but in flex and materials. Slalom skis were of fiberglass, GS skis of aluminum. Recreational skis were thinner (therefore softer) and made of less-expensive materials. Buying skis required a lot of trial and error to find the flex pattern that worked for your weight, strength, skill and snow conditions.
Today most of that trial-and-error is gone. You can choose a ski based on matching width and turn radius to the kind of snow you like.
For hard snow, get a ski with a narrow waist: 70mm or narrower.
For soft groomers or general western front-of-mountain skiing, get a moderate waist — 70 to 78mm.
For resort powder (with a firm surface underneath) get a mid-fat waist, 75 to 85mm.
For deep snow (with an unpredictable base beneath) get a fat waist, more than 85mm. If you’re big and heavy or carry a heavy pack, go even bigger: 95mm and up.
What remains is length and shape. Most men skiing at resorts can get along very nicely on a 165cm ski, most women on 155cm. If you’re stronger than average, go a bit longer but nowadays it won’t buy you a lot of additional stability. If you’re much lighter than average, go a bit shorter — it will pay off in improved agility.
Shape means sidecut. A deeper sidecut with a shorter radius carves a shorter turn. In general, this helps best on groomers. It won’t help in bumps, where you want the tail to release to avoid hanging up at the end of the turn. A good mid-fat nowadays has a shape close to 115-76-105, which gives a theoretical radius of about 12 meters and a bearing surface of 1350 cm2. Note that the bearing surface — the ski’s ability to “float” on soft snow — is similar to the classic straight slalom ski. So is the ski’s weight. But the agility — the ability to bend easily into a turn — is vastly improved due to a turn radius roughly 25% of the old long, straight ski.
So what shape should you buy? Start with that “generic” 115-76-105mm shape at your length, then blow the waist up wider if you’re going to ski a lot of soft snow, and pull it in narrower if you’re going to ski a lot of hard snow. If you’re an expert who loves to carve, go for a shorter radius. If you want to be able to slide the tail a bit in bumps and tight woods (or if you have to skid a bit when you teach intermediates) opt for a bit narrower tail.
That’s the basics. Next time, I’ll consider the relationship between shape and flex pattern.
Vail Ski School