The art of ski design: be smart choosing skis
Posted 1 year, 11 months ago by Seth Masia
Pete has asked me to contribute some thoughts on the art and science of ski design. Over the next few weeks I’ll post some advice, some data and some considerations regarding the design of custom skis.
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: 67mm or narrower.
For soft groomers or general western front-of-mountain skiing, get a moderate waist — 68 to 74mm.
For resort powder (with a firm surface underneath) get a mid-fat waist, 75 to 80mm.
For deep snow (with an unpredictable base beneath) get a fat waist, over 80mm. If you’re big and heavy or carry a heavy pack, go even bigger: 90mm 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 112-71-100, which gives a theoretical radius of about 12 meters and a bearing surface of 1300. 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 should shape should you buy? Start with that “generic” 112-71-100mm 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.
–Seth Masia
Vail Ski School
Permalink · Posted by Seth Masia · October 12th, 2008 · · Read 3 Comments
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October 12th, 2008 at 10:01 pm Pete Wagner
Seth -
Thanks for your thoughts. You have to take the typical ski buyer’s guide with a grain of salt because a ski that is great for one person may be terrible for another. And, with so many skis options out there, it’s difficult for people to identify their optimal ski. Your guidelines create a great reference and starting point. Obviously, every skier is different and their needs are unique. Equipment preferences are heavily influenced by past equipment preferences. For example, some people like the stable feel and pop of Volkls, while others prefer the quickness and lightweight nature of Salomons.
Last season, I skied a 172cm length ski with a 105mm waist and 23m sidecut radius as my day-to-day resort ski in Telluride. It has definitely changed the way I ski and my preferred terrain – I make less turns and find myself avoiding hard snow. I guess the design is more of a big-mountain design and that’s the type of terrain that I seek out. Nonetheless, I’m thinking that a 90mm-ish waist ski will work well as my typical resort ski for trees, steeps, and bumps when we don’t have fresh snow.
I’d say I don’t fit into your guidelines. Am I just a freak?
Pete
October 13th, 2008 at 7:27 am Seth Masia
Obviously you’re not a freak, but you are strong enough to roll a very wide ski onto its edge, and you have the balance skills to hold it there precisely. You can do with a very wide ski what the average advanced skier can do with a 70mm ski.
Note that the very wide ski has affected your choice of terrain and snow conditions. If you had to ski hard snow frequently you’d quickly have picked up a narrower ski.
Yes, your preferences are influenced by what you’re used to, which amounts to what you’ve adapted to. The point about the stable feel of Volkls is relevant here. Volkl creates this feel through its choice of materials. The materials in the ski affect its weight, glide speed, stability in junk, general smoothness, resilience, energy level (what you call “pop”) and durability. More about this later.
Seth
October 15th, 2008 at 1:11 pm Ryan
Interesting discussion guys.
Telluride is a BIG mountain and locals ski fast.
I don’t think strength is an issue in ‘rolling a ski on edge’ …………. that’s a move of either the knee or the center of the body (cross over / cross under). BUT, speed is: the build up of forces (in REACTION to speed) help to manupulate the pressuring of, and holding of the skis edge.
Shape of the turn: ease to pivot or carve?
I am amazed at the number of recreational skiers I see who are able to pivot a ski which is VERY wide underfoot. (IMHO..that is about strength.)
In icy conditions, traveling slowly, medium pitch: pivot: edge set. Same conditions traveling faster I might be able to keep the ski on edge from start to almost finish of the turn (tail skids out.) But pick up that speed, combine the forces:pull of gravity, pressuring, steering and I can fly…… arcing the ski
In mashed potatoes at ANY speed, any level of personal strength: pivot /edgeset imposskable (sic). ( I better strengthen steering and pressuring as well as a little of reckless abandon.)
The point being: who do I want to be; under what conditions do I want to be; and…….who am I?