Evolution of Ski Shape

Seth Masia

When the first “shaped” skis arrived at ski shops in 1993, they were a revelation.

Deep sidecuts to help skis carve short, clean turns had been sneaking up on us for a century – so slowly that only a very few savvy ski designers, largely outside the mainstream Western European factories, could see them coming.

Sidecut – the subtle hourglass shape of the ski – goes back to skiing’s prehistory. It was invented by now-forgotten artisans sometime before 1808 and was adopted universally after being popularized by Sondre Norheim and his friends in Telemark, Norway, around 1856. Early skiers, who carved their own skis, found that pinching in the waist of the ski made it easier to turn. Since that time, the “straight” ski with parallel edges has been a rarity, enjoying real popularity only as a light cross country ski for use in modern machine-set tracks, and for modern jumping skis. In alpine skis, sidecut shape has grown gradually deeper over the decades, stalling for about five decades starting in 1936, and at a greatly accelerated pace since 1988.

In the beginning: 4mm of sidecut

The original Telemark skis were carved by hand in home workshops, and the dimensions could vary quite a bit. But a typical Norheim-era ski, as represented in modern replicas from Morgedal, measured 81mm across the shovel, 67mm at the waist, and 70mm across the tail, for a sidecut depth of 4.25mm. (These skis, patterned after Sondre Norheim’s own work, were built to commemorate the 1988 Calgary Olympics.) Telemark dimensions worked well for Fridtjof Nansen and Roald Amundsen, and this standard shape was still relevant midway through the 20th century, when ski manufacturers began to think about making skis of metal and fiberglass in elaborate molds.

Sidecut depth means that if we put the ski on a table and tilt it up so the base or sole is at a right angle to the tabletop, resting on the widest points of the tip and tail, then the distance from the ski’s waist to the table is, in the case of the original Telemark model, 4.25mm. (Today’s turny slalom skis have a sidecut depth of about 18mm.) Based on the ski’s running surface length (that is, the length of edge in contact with the snow, excluding the turned-up tip), the radius of the sidecut curve is 83 meters – very long by modern standards, but certainly not straight. The geometry worked well enough for running and jumping skis, and it changed very little into the 1930s, when a typical 230cm jumping ski (91-77-80mm) still had a sidecut of 4.25mm, and an agile 192cm women’s cross country ski might be 88-73-80mm, for a sidecut depth of 5.5mm and a turny radius of 47m – about half that of the jumper.

This basic shape was still viable when Howard Head cranked out his first aluminum Standards in 1950. The 79-inch version of that ski (203cm) measured out at 81-68-77mm, for a sidecut depth of 5.5mm and a 62 meter radius.

Experiments in carved wood: 7mm of sidecut

When skis were made of carved hickory, it was pretty easy for a craftsman to experiment with sidecuts. The workmen at Thor Groswold’s factory were among the more innovative talents. They were happy to build a ski to an athlete’s specifications, and it shouldn’t surprise anyone who has watched him ski to learn that Dick Durrance liked a very turny shape. The 206cm Durrance signature model, from around 1939, measures 74-54-62mm. This is remarkably narrow for an alpine ski, unless it was meant exclusively for running slalom on ice. What most folks didn’t notice was that the ski offered a dramatic increase in sidecut depth to 7mm (radius 42 meters). And a wider GS-style ski, the 212cm Barney McLean model from 1950, ran 90-73-81 – sidecut depth 7.25mm and radius 48 meters.

The 7mm sidecut depth became the new standard for race skis, good for the next four decades. The Kastle slalom used by the 1964 medalists Pepi Stiegler, Billy Kidd and Jimmie Heuga had a 6.75mm depth on a 64mm waist; the 1968 Rossignol Strato and Dynamic VR17 measured 6.75 and 6.5mm on a 69mm waist; and as late as 1983, the Rossignol SM GS ski still used the Strato shape (the contemporary FP slalom ski was narrower – and straighter). The big innovation, introduced by Dynamic in 1967, was to move the waist back about six inches, from the ball of the foot to the heel. The change was hardly noticeable to the eye, but it helped the great French racers of the era to accelerate out of the end of the turn.

The Mahre brothers raced and won on slalom and GS skis with a 7mm sidecut depth, patterned after the French race skis. From 204cm down, K2’s molds emulated the VR17 slalom shape. From 207cm up, they used the Strato GS shape. The Mahres were so successful on the 710 and VO Slalom that the shape was widely imitated in Austrian factories – thus the first Fischer Vacuum Technique slalom was a mirror image of the VO, which of course was patterned closely on the original VR17. All these skis featured a stiff tail, cracked edges, a sidecut shape close to 7mm and a waist width close to 68mm, making for a radius of 48 to 51m. Atomic, Kastle, Blizzard and Volkl all built their own versions of this ski.

Ingemar Stenmark held an advantage over the Mahres, skiing on an Elan shape with an 8mm sidecut depth, giving him a 20% shorter turning radius of about 41 meters (it's now reported that Stenmark liked to file an extra millimeter off each edge at the waist, which would have given him a 9mm depth and a 37m radius). Partly to save money, many skimakers liked to have single set of molds, so during this era, if you wanted a full-length Elan ski, you got the company’s standard “Uniline” sidecut shape. The big differences between models were in flex pattern and materials – slalom skis had stiffer tails, GS skis had aluminum layers, recreational skis had a softer, rounder flex. If you were to graph the evolution of sidecut, the line would show a flat spot from 1940 to 1980, an era when most skis stalled at the 6 to 7mm depth.

Snowboards shake up the scene

Something dramatic happened in the mid-70s: snowboards. Snowboard designers owed no loyalty to ski design. The 1975 Burton Backhill Board, a plywood plank 140cm long, with no steel edges or plastic base, sported a radical sidecut shape of 302-265-295mm, for a sidecut depth of 17mm and a radius of just 6 meters. The shape set a pattern — a modern 155cm freeride board typically has dimensions of 302-257-302mm for a radius of 7 meters.

Most ski designers ignored this phenomenon, though we often hear the myth that ski designers learned all about sidecut from snowboarders. Around 1979, Head’s chief engineer John Howe and marketing chief Gary Kiedaisch came up with the concept Natural Turning Radius, under which short, agile recreational skis would have a slightly deeper sidecut than the factory’s long high-speed cruising and racing skis. The idea reached the market in 1981, when the 180cm Head Yahoo (92.5-71.5-80mm), with a 7.3mm sidecut, offered a turn radius of about 35 meters. The company didn’t go so far as to build deep-sidecut molds, but Kiedaisch produced a pocket-size flexible aluminum ski for salespeople to use in demonstrating how a carved turn works. The sales tool had an exaggerated sidecut, and some people who saw it thought, “Hmm, why don’t they make real skis that way?”

Albert goes wild

In 1984, an executive at Olin Corp. had been having trouble learning to ski. He asked Frank Meatto, an engineer at the company’s ski division, why the factory couldn’t build a sort of Prince tennis racquet for skiers – something that would make the learning process a lot easier. Meatto, along with Ed Pilpel, had been working on designs for a better race ski, and had an idea that the key to a great teaching ski would be a deep sidecut. According to Pilpel, Meatto came up with “Albert,” which ski industry insiders consider the first of the modern shaped skis. Albert, named after a plastic toy belonging to Meatto’s dog – had a very fat tip and ridiculously narrow waist: according to Pilpel, the dimensions were 128-40-79mm. The prototype would have had a sidecut depth of 31mm and a radius of 8 meters. The swollen tip wouldn’t fit in Olin’s presses, so Meatto had to figure out how to make it narrower without sacrificing the deep sidecut. At the time, racers skied a very one-footed technique, leaping from inside edge to inside edge. Meatto wondered if they even needed an outside edge. He sliced Albert almost in half and prototyped an asymmetric 150cm ski, with a ruler-straight outside edge and a radical sidecut on the inside edge with a 10 meter radius. The waist wasn’t wide enough to accommodate a ski boot, so Meatto engineered an elevated Delrin platform to carry the bindings. He took out a patent covering the deep sidecut and the leverage advantage of the platform, specifying that the ski edge ran close to the centerline of the bootsole, like an ice skate. Olin produced a run of 150 pairs for introduction at the 1986 SIA Trade Show. Instructors who tested it thought Albert was a fabulous idea, but retailers thought the asymmetric hourglass shape far too cartoonishly weird and declined to buy it. Albert slid into obscurity, but the patent drawings lived on in Olin’s corporate legacy, to surface in other offices.


In 1988, Atomic engineer Rupert Huber was asked to create a better powder ski. By this time, like most ski factories, Atomic was building snowboards. It seemed logical to Huber to use the capacious floatability of a wide snowboard as a powder ski, so he simply bandsawed a snowboard in half, turned its steel edges inward, and put ski bindings on it. The production version became the Atomic Powder Plus, at 133-115-122mm the world’s first superfat powder ski – with a traditional straight-ski sidecut depth of 6.25. But a year later Volkl began work on its mid-fat Explosiv; the original 190cm version carried a profile of 118-94-110mm, for a sidecut depth of 10mm and a scary-short radius of 28 meters — helping this massive metal ski to feel reasonably agile underfoot.

The 10mm race ski

During the late ‘70s and early ‘80s, giant slalom racing changed. The Brothers Mahre and their chief rival Ingemar Stenmark developed a faster, straighter line from gate to gate, with a tighter, slalom-like turn. Course-setters responded by placing GS gates further across the fall line. According to K2 engineering chief Jim Vandergrift, by the late ‘80s GS had become a race of round turns across the hill. A few race ski designers began to think about pushing the sidecut depth up to 9 or 10mm. For race stock GS skis, used exclusively on hard snow, it was easy to make the waist narrower. Most of the European factories put their racers on new limited-production skis with a waist width around 62mm and a sidecut radius around 32 meters. By comparison the Rossignol SM VAS ski sold to the public had a 69mm waist for a radius of 48 meters.

At K2, designer Walter Knott remembers, “We figured we needed a little deeper sidecut to help the racers make a cleaner turn.” Thus was born, in 1990, the aluminum K2 GS Race, with its 10mm sidecut (my pair of 205s actually measures 10.6) and, in 1991, a fiberglass version for fast recreational skiing, the Velocity. These skis were a delight for fast skiing on groomed snow. A good skier quickly learned to start the turn with a touch more edge tilt – and a lot less steering. You got less tail slip at the beginning of the turn, and noticeably more speed through the entire arc. Volant followed on, in 1992, with the Zmax G, a fast racer/cruiser with a radical 12mm sidecut. On groomed Western snow, the G lived up to its name, in every sense. The first time I made a run on these, I found myself catapulting from arc to arc with effortless speed. The young racing star Amy Livran said “Hey, where have you been training?” It was becoming clear that better sidecut could make us all better skiers. By ’93, Dynastar also had a 12mm cruiser, the G9 race ski. K2 revised the Velocity as the MSL, which in its second year featured a 12mm sidecut. K2 also sold a version of the Volkl fat ski as the Big Kahuna, specifying an 11.5mm sidecut.

Other race ski designers were thinking along similar lines. In 1991, Bernhard Russi created a very twisty, technical downhill course for the 1992 Olympic venue on Bellevarde Face in Val d'Isere, a course clearly designed to favor very technical skiers like Gunther Mader, who had won World Cup races in slalom, GS, Super G and combined. At least one factory responded with experimental, turnier downhill skis. Little-known Austrian racer Patrick Ortlieb, who had never won a World Cup downhill, took gold on a slim-waisted Head ski, barely edging out Franck Piccard, 1988 Olympic Super G champ, on an Atomic-built, Dynamic-branded ski. Mader took third on Fischer. The speed specialists who finished at the top of World Cup downhill standings that year -- Franz Heinzer, Daniel Mahrer and AJ Kitt -- finished more than a second back. Race rooms are always very secretive about what they do, and in the era before FIS imposed rules on ski dimensions, there was no reason to reveal the actual sidecuts of downhill skis. 

The Revolution

But the real breakthrough came from out in left field. Jurij Franko graduated from the University of Ljubljana in 1983, with a degree in engineering, and joined Elan in ’87 as a lab manager. In 1988, he had an idea for a deep sidecut ski, and his colleague Pavel Skofic calculated a suitable flex pattern. They organized a project dubbed Sidecut Extreme – SCX – and set out to build prototypes. (Jurij Franko is often confused with his schoolmate Jure Franko, whose successful World Cup career was capped by a silver medal in giant slalom at the Sarajevo Olympics.)

Over the next couple of years some very strange skis emanated from Franko’s lab. Back in 1977 Elan had produced a run of Variable Sidecut System skis, or VSS, slotted along the centerline through the shovel and tail. Across the top of each slot was a jackscrew, so the skier could adjust the width of the shovel and tail and thus the sidecut. It was a crude experiment, but it produced data that helped Franko and Skofic zero in on a new sidecut shape. Franko’s calculation was straightforward: “Choose the radius of the turn — 10 meters, for example. Choose the speed you want to ski — 5 meters per second for example. Calculate the centrifugal force and the lean angle, as for a bicycle. This is the angulation of the ski. Imagine a ski of constant width bent to the radius of the turn and penetrating through the snow. ‘Cut’ the ski with the snow surface, and there you are!”

By 1991 Franko and Skofic had finalized a 203cm mold for a GS race ski with a 110-63-105mm profile – that’s a 22.25mm sidecut, three times what most racers were using for slalom at the time. Sidecut radius was just 15 meters – about 35 percent of Jure Franko’s medal-winning Elans from ‘84.

The SCX was blazingly fast on the GS course. In its first local races, skiers on the SCX took eight of the top ten places. The new ski conformed more easily to the actual arc required to carve a clean turn in the racecourse. For any given turn, the racer needed less edge angle, and could therefore stand on a straighter, stronger leg. Folks on the World Cup circuit woke up.

In the Austrian Tyrol, Kneissl was trying to scramble back into the international market. In the late ‘70s the Tyrolian factory had tried to streamline production by converting to injection-molded foam-core construction for all its skis. The result was a marketing fiasco and bankruptcy. The company went through several ownership changes, and from 1986 to 1989 was partnered with Olin and Trak as part of Tristar Sports. Kneissl designers may have seen the Albert drawings. By 1990, reduced to being the local Tyrolean brand, Kneissl had resorted to making the “Bigfoot” novelty ski, a strange 80cm snowskate pitched at casual skiers. The Bigfoot, which featured a tip shaped like a set of toes, could strap to ordinary shoes as easily as to ski boots, and had a snowboard-style deep sidecut. Early in 1992, designer Wolfgang Wagner thought the deep sidecut might make an interesting recreational ski, and came up with the 180cm Ergo at 100-62-100mm – 19mm of sidecut depth, with a radius of 14 meters. Kneissl took the prototype to ISPO, the European trade show, that spring.

(A modern myth has arisen that ski designers adopted deep sidecuts from snowboarding, but the folks at Elan and Kneissl didn't make snowboards and apparently paid no attention to the sport.)

Carving for everyone

By April ’93, Elan’s sales organizations in Europe and North America had seen the SCX prototype. Mike Adams, marketing director in the U.S., sent four sets of samples out to ski instructors around the country, including Bill Irwin at Killington and this author at Squaw Valley. I was amazed at what the ski would do – it made me instantly the equal of the best skiers on the mountain, in any kind of snow. More to the point, when I put a middle-aged intermediate-level student on the Kneissl Ergo, she was immediately able to carve clean turns in spring corn, over rotten crust. I put her husband on the SCX, and he could do the same. The couple were the novelist Amy Tan and her husband Lou deMattei – and they may have the honor of being the first ski school clients ever to learn to carve on modern shaped skis. All the instructors who tried the SCX called Adams back and said “I don’t know what this is, but it’s a fabulous teaching tool,” or words to that effect.

Adams got the message. Franko and Skofic spent the summer creating a shorter version, scaling everything down but keeping the same radius. The result was a 163cm teaching ski for adults, and a 143cm junior race model. By December, Adams was demonstrating the short SCX to ski school directors and resort managers. “Everyone who skied on it was blown away,” Adams recalls.

Another Balkan racer was thinking along the same lines. Ivan Petkov retired from the Bulgarian ski team in 1976 and took up windsurfing. He designed and built a line of “Bora” sailboards and won the national championships three times between 1977 and 1980. He came to the US in 1987, to spend the summer in Hood River and the winter teaching skiing in Aspen. By 1989 he was managing a retail operation for Robbie Naish on Oahu, and while watching the craftsmen there carve custom sailboards, got the idea for a new carving ski. In the spring of 1992 he went back to the resort town of Pamporovo, in the Rhodope mountains of southern Bulgaria. There, Atomic had set up a factory to make some of their inexpensive constructions.

“I had them make a mold for a 187cm ski with a profile of 113-61-91,” Petkov says. “We couldn’t find a wide-enough base material, but they also made water skis there so we got some greenish-blue polyethylene and cut the base out of that. I took three or four pairs in different flexes and went to Mt. Hood. We were amazed at how well they held.”

Petkov called his new product the S-Ski, for its turn shape. He applied for a patent on the geometry. He ordered more skis in 183 and 193cm lengths, and went to the SIA Trade Show in the spring of ’93. “Everyone came to the booth,” Petkov remembers. “Warren Witherell (author of How the Racers Ski) was very excited.” He shipped 300 pairs. The 183cm sample in the Colorado Ski Museum measures 115-61-85, for a 19.5 sidecut depth and a 15 meter radius.

For 1994, there were shorter lengths, 163 and 178cm, and Petkov sold 1200 pairs. S-Ski was on a roll, but Petkov was unhappy with Pamporovo’s quality, and opened negotiations with Blizzard to build his ski.

Wagner, Franko and Petkov settled on shorter lengths for a simple reason: When the tip and tail grew wider, a full-length ski felt intolerably heavy – there was simply too much mass out there at the end of the lever. The 208 version of the K2 GS Race, for instance, felt as ponderous as a downhill race ski, and it was called by insiders The Hammerhead. The solution was to shorten the ski dramatically. When average width rose 13% (from 72mm to 83mm), length needed to fall 13% (from 204cm to 178cm). Bearing surface area remained the same, and so did material weight. But the turn radius – proportional to the square of the running surface length – fell dramatically. Additional mass at the tip and tail, combined with improved edge contact through the turn, meant that the new 180cm skis could be as stable as the old straight 205s. Another design change proved essential: the ski had to be stronger and stiffer through the center to prevent the wider tip “hinging” upward in bumps and deep snow.

Atomic, Fischer and Head had taken notice and quietly began to design 15mm sidecut skis of their own. There was the Fischer Revolution Ice (92-62-92mm), the Head Cyber 24 (94-61-90mm), and a whole group of identical skis marketed under the Atomic-built labels: Atomic, Dynamic, Hart, Rohrmoser, Colt. “It turns out that everything we thought we knew for forty years was wrong,” admitted one Austrian ski designer. But the big Western factories – notably Rossignol/Dynastar, Salomon and K2 – seemed somnolent in the face of impending revolution. “Shapes are a fad,” snorted a senior executive for one French skimaker.

There was a good economic reason for their delay. 1990 was the year Salomon entered the ski market with its “cap” ski – a good conventional ski with a seamless one-piece plastic top to replace the traditional “square” sidewalls and topskin. The streamlined look was really just a simpler way to make skis but, billed as a “monocoque” structure, it took the world by storm. By ’93, factories around the world saw their business eroded by the Salomon invasion and decided to invest millions in new molds to build cap skis. With crash programs under way to compete with Salomon, few plant managers wanted to spend additional millions creating molds for deep sidecuts. As late as 1994, Rossignol built an entire factory for rapid manufacture of the injection-molded 4SV cap ski, with a painfully straight 7mm, 83-64-73mm profile – and the factory didn’t yet have a shaped ski in progress.

Many factories went bankrupt trying to keep pace with Salomon. Among them was Blizzard, which slid into the control of the banks during ’94 and ‘95. But the factory already had Petkov’s S-Ski mold, and began producing its own cap-ski version that spring. Meanwhile Pamporovo made versions of the original S-Ski for other brands.

But Elan, the odd little factory in Begunje, Slovenia, was never threatened by the Salomon monocoque. Presciently, in 1990 it had developed its own cap ski, the MBX Monoblock. By ’94 Monoblock sales subsidized the creation of a complete set of cap-style SCX molds. Elan not only had a lead in shaped skis, it had a catchy name for them: “When Jurij tried to describe the turn shape to a journalist, he used the word parabolic,” Adams recalls. “And that’s what we named the ski.”

Bode Miller and mainstream acceptance

Engineers at K2 at last paid attention. In the spring of ’94, without reference to the Albert patent, a series of internal memos defined the profiles for what would become the K2 Four, Three and Two. The shovels wouldn’t be as wide as the 105+mm Elan, Kneissl and S-Ski, because all of K2’s wide presses were busy building snowboards. With a width limit, the Four wound up with dimensions of 98-65-87 – a 14mm sidecut depth, describing a 22 meter radius at the 195cm length. When the mold was finally cut the following year, the result arrived in New England just in time for a young racer named Bode Miller to try it out in the ’96 Junior National Championships. In four events at Sugarloaf that March, Bode took three firsts and a second. Overnight every Master’s racer in the country needed a pair of K2 Fours just to be in the game.

The word was out: If you wanted to keep up with the hot guys, you needed shaped skis. Traditional 7mm “straight” skis began to pile up in warehouses. Salomon and Rossignol had hundreds of shipping containers full of slick, straight, heavily discounted cap skis. In ’96, playing catch-up, Salomon began work on the Axendo series (99-64-89mm; 15m) and hired Mike Adams away from Elan. Rossignol created a series of Cut 10.4 shaped skis (104-62-94; 19m) at a dramatically reduced price and shoehorned them into every rental inventory they could reach.

That winter, Petkov realized he’d been undercut by Blizzard and Pamporovo: both factories planned to compete with him using his own mold. He turned to K2, which offered to build skis in his dimensions. The Vashon Island factory backed out of the deal when Petkov threatened to enforce his patent against any and all factories, including his own supplier. With no one to build his product, Petkov’s S-Ski slid from sight.

By 1997, shapes had proliferated in all directions. There were fat shapes for powder, called Chubbs and Fudds and midfats. It was possible to buy deep shapes, moderate shapes, race shapes, carver shapes, powder shapes, expert shapes, learn-to-carve shapes and learn-to-ski shapes. Straight skis were piled in clearance racks across the country for $29.95.

In the new century, shapes have grown so radical that the International Ski Federation has imposed limits. Today a FIS-legal GS ski must have a radius of at least 21 meters – that’s K2 Four territory. Civilians can buy an “oversize” illegal GS ski – designed before the rules went into effect – for fast cruising, and that has in fact become a popular category among non-racing experts. And a slalom race ski must be at least 155cm long (for men – 150cm for women). Something as radical as the K2 Seth Pistol – meant for huge jumps and stunts in powder – with its 128-90-115mm, 14 meter radius, looks conservative next to a full-boat World Cup slalom like the Volkl P60: 115-62-98mm, with an 8.2 meter radius.

On skis like this, today’s racers — Bode Miller, Hermann Maier, Benni Raich and the Kostelic kids– can bend space-time. Hell, so can you and I.

That’s a revelation.

A radical early experiment

In the winter of 1948-49, DU racer Jerry Hiatt, who worked in Thor Groswold’s shipping department, got together with high schooler Jerry Groswold and proposed making a turnier slalom ski. They took a pair of the laminated hickory Rocket model – a very flexible ski to begin with – and carved it down to about a 52mm waist, leaving the tip and tail alone. This gave them roughly a 15mm sidecut, twice the normal depth. “We put the edges back on, and went up to Winter Park to try them out,” Groswold remembers. “They turned sensationally but wouldn’t stop turning. We got one long round turn, and a step turn, and another long round turn. We each made one run and went back to the factory and threw the skis in a corner. They probably became firewood. It never occurred to us to keep the waist at 70mm and make the tip and tail a lot wider, as is done today.” This oversight was a natural one, considering that Groswold bought hickory lumber in 4-inch widths. To make the tip wider than 100mm would have required some fancy gluing. Moreover, when they made their skis so narrow at the waist, the two Jerries also made them very soft in flex through the middle, giving them a severe case of double camber. The solution would have been to make the middle of the ski thicker, not wider.

Copyright 2005 by Seth Masia

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