Tag Archive for: ski testing

Marc Liebman

70s Ski Testing: Defining How Skis Work

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Step 1: Inventing The Right Metrics

[Editor Note: In this new series, former SKI editor Marc Liebman recounts how serious ski testing began as a way to provide consumers with objective information about ski performance.]

In the early seventies, ski design was in the midst of a revolution that is still going on today.  It started in 1959 when Art Molnar and Fred Langendorf marketed the first ski with a fiberglass reinforced core under the Tony Sailer brand.  When it came out, skis were made predominantly from wood with a P-Tex bottom and segmented edges screwed into the core.  One piece steel edges were coming into vogue.

Computers and programs to model flex patterns, torsion (twisting) and the impact of different materials on ski performance were in their infancy. Ski design was (and still is) a mix of sound engineering, materials science, and experience.

Ski manufacturers touted the benefits of fiberglass versus aluminum sheets or rods or u-shaped metal versus foam or wood cores and the list went on and on.  Ski Magazine’s (and Skiing’s) customer research said that their readers wanted an objective way to compare skis.  Net net, we – the skier – were confused.

In 1971, Ski Magazine contracted John Perryman, an aerospace engineer to come up with a methodology that would achieve four objectives:

  1. Measure the dynamic and static properties of the ski;
  2. Analyze these properties mathematically because they don’t act in isolation and are intimately related to each other;
  3. Correlate bench testing with a rigorous on-snow program that requires the skis to be put through a standard set of maneuvers by the tester on a variety of snow conditions and terrain without knowing the ski’s identity; and
  4. Present the results in an easy to understand format that enables the skier to compare ski A with ski B.

The program was called SKIpp for Ski Performance Prediction.  Each year, SKI magazine tested more than 200 skis, all roughly 200 centimeters long. I was on the initial team. Calculations were done with a slide rule and data tabulated on my Bowmar Brain, one of the first electronic calculators.  We created five metrics that we believed defined ski performance:

  1. Foreflex dynamics – complex calculation of the force needed to bend the front portion of the ski and its resistance to rapid flexing;
  2. Afterflex dynamics – same as the front for the portion of the ski behind the boot;
  3. Effective torsion – combination of resistance to a ski’s twisting and how sidecut affects ski’s ability to turn in an arc;
  4. Effective Compression – measured the camber of the ski along with the force needed to flatten the ski; and
  5. Damping – ability of the ski’s to suppress vibration.

Based on the data gathered, we could predict how:

  1. Easy a ski was to turn;
  2. It would perform in different snow conditions; and
  3. How it stable it would be at high speed.

Looking back, we didn’t realize how far ahead we were in ski performance analysis.  In the beginning, several manufacturers challenged our results, but in the end, they came around to our side of the table which was that the correlation between our lab analysis and on snow performance was amazingly accurate.

Marc Liebman

Guest Ski Tester

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SKI Magazine Ski Testers Meet The Sundance Kid.

Gene Hackman and Robert Redford in “Downhill Racer” (1969). This heart throb really loved to ski.

Back in the early ‘70s, SKI Magazine (remember it?) developed a program called SKIpp that stood for “ski performance prediction” developed by the late John Perryman. He was a talented engineer who spent years in aerospace and worked with Howard Head at Head Ski Company. SKIpp had two parts, the laboratory analysis that predicted how the ski would perform and on-snow testing. Each year we tested 200+ skis.

John did the analysis and I ran the on-snow testing. Our testers were a mix of male and female skiers, primarily ski instructors with some racing experience. In March, 1974, we were at Park City which let us set up our testing tent near the base of the Shaft lift. Every morning, we tested ten pairs of skis. After lunch, each tester picked his favorite ski from the day or prior days and headed for the lifts.

One bright sunny morning, my lovely wife Betty was collecting test forms in the tent along with Joan, John’s wife, when one of the testers who was, at the time, the ski school director of Sundance Ski Area, walked into the tent and asked a simple question. “Would we allow Robert Redford ski on some our skis?”

We had skis that weren’t on sale yet, some that wouldn’t make it to the market, some that should never been sold to skiers, and Redford hadn’t signed the liability waiver. All of this went out the tent flap when Redford walked into the tent.

I tried to be my best cool, calm and collected Naval Aviator self, but the look on our wives’ faces was priceless – eyes and mouth wide open. Both were speechless that, if you knew them, was rare. His presence attracted the other three female testers who were nonchalantly trying to swap skis or ask Betty, John, or me a question just so they could get in the tent with Redford.

John looked at me, I looked John, and we shrugged. While our wives stared at the famous movie star, I managed to ask, “Can you ski 200 centimeter skis?”

“Yes.”

“What size boot do you wear?”

He gave me a size that I don’t remember. This was back in the days when boot sole shapes weren’t standardized, and we were using Market Rotomat rental bindings that took some fiddling to adjust. None of the easy-to-adjust bindings that we see today existed.

To this day, Betty will tell you she talked to him for a few minutes but has no idea what she said or was she coherent. What we do remember was that Redford was as good-looking in person as he was on the screen.

Oh, and one more thing. By the time he returned the skis, the word was out that Redford was around and a larger than usual crowd had gathered around the tent. None of us were smart enough to get him to autograph the test card he graciously filled out. Oh well!!!