Once upon a time, most skis were made of a few materials glued together. Wood, aluminum and fiberglass were most common. Not today. As Madonna would say, “we are living in a material world.” Material science advancements in aerospace and military applications have made their way into the ski market. That means all sorts of materials are now available for strength, flexibility, dampening and durability can be combined to create a wide variety of performance characteristics for speifi skiing objectives.
Everyone loves trees. They’re beautiful, strong and flexible. Some can live for 5,000 years. People have used wood for all sorts of products and still do. Wood is strong and durable. Woods are easy to work with. It can be cut, combined with other woods, pressed, formed, and glued. Certain woods like Ash, Poplar, Maple and Aspen are stiff and durable. These woods maintain their strength and have relatively long-lasting flex characteristics. This makes them perfect materials for skis. Wood cores are still common. Wood cores can be engineered for specific stiffnesses and flex characteristics. Wood cores also act as natural dampening characteristic creating a smooth feel for the skier.
Composite materials are materials made from two or more constituent materials. When combined as a composite, the composite takes on different characteristics than either of the two constituent materials. Generally stronger Concrete is a composite made of stones and cement. Fiberglass is a composite made of glass and plastic. Carbon fiber, kevlar and Titanal (see below) are composite materials.
Fiberglass is melted glass that has been extruded to produce a string like substance. The string can can be woven into yarn, and the yarn into a kin od cloth. It often comes in rolls and looks like cloth. It can be easily cut into any shape. The shapes can then be placed in molds, or layered on top of each other. To harden the fiberglass, a resin, in liquid form can be added. The resin requires a catalyst so that it reacts with the fiberglass. The fiberglass and the resin hardens. Fiberglass is really cheap (about $1.50 per lb). That’s why its commonly used. But it’s heavy.
Carbon fiber are carbon bonded carbon atoms made into chains. These “carbon strands” can be twisted together like yarn. The yarn, in turn, can be woven together like cloth. It looks like cloth and can be purchased as rolls. It can be easily cut into any shape. The shapes can then be placed in molds, or layered on top of each other. To harden the carbon, a resin, in liquid form can be added. The resin requires a catalyst so that it reacts with the carbon and hardens. Carbon fiber’s key characteristics are strength (five times stronger) and weight (two-thirds less than steel). It’s also twice as stiff as steel. Carbon fiber has better characteristics than fiberglass but its four times as expensive, about 5 to 7 times the cost of fiberglass.
Cellphone cases are often made of carbon fiber materials. The fibers create strength and act as a dampening agent. Ski manufacturers use these fibers for similar effects.
Aramid is a synthetic of polymers. The polymers are catalyzed into a solid that can be spawn like yarn, and woven into cloth. The fibers are very strong. Aramid fibers make up Kevlar. Kevlar is used in bulletproof vests. Kevlar is used because it is strong and also acts as a dampener to spread the force of the bullet. Aramid can be used n ski construction for similar purposes. It can provide strength and act as dampener.
Advancement in materials has profoundly influenced ski construction options. Composite layers give skis amazing torsional strength. These composites can be layered above and below the core. It serves the dual function of protecting the core and creating torsional rigidity. The most composite used for in ski manufacturing is fiberglass. For decades manufacturers have been creating fiberglass wraps (bi-axial and tri-axial) to facilitate torsional rigidity. The wraps weave the glass fiber strands at various angles to one another.
Simple plastics are organic polymers with little strength. However, they are great coatings and can easily be strengthened to make good coatings for top sheets.
Plastics and rubber can be manufactured in ways to create foam versions. For skis, the foams are designed to approximate the density of wood. However, they tend to lack other quality characteristics of wood like flexibility, strength, and durability. These foams can be injected or layered into a ski core. Foams are cheap and light. Most higher end skis today avoid foams. They simply don’t perform as well as the alternatives. That said, advancements in material sciences are likely to rekindle interest in foams.
Polyurethanes & Polyethylene
Polyurethanes, also called urethanes, are artificial rubbers. They are often used to create foams that can be injected into things. Polyethylenes are the more common plastics used to make containers and bags. They can also be manufactured to be very strong, yet easily meltable.
Hardened polyethylenes are used to coat the base layers of skis. Bases can be extruded or sintered. Extruded bases are where polyethylenes are melted, cut into shapes and hardened. These are relatively cheap and low maintenance. Sintered bases are where the base material is ground into powder and then heated and presses into shapes. Sintered bases are porous and absorb wax well. In fact, they need to be waxed to maintain performance.They require more maintenance and are harder to repair. Often there is sintering (hardness measure) number on the base describing the hardness of the polyethylene. They’re used to repair ski gauges. P-tex is a polyethylene.
Rubbers are elastomers: polymers with viscosity and elasticity. Rubber deforms and bounces back into its original shape. Ski manufacturing often use rubber as a dampening agent. It can be cut into strips, layers, and other shapes and sandwiched into the ski.
Piezos & Ceramics
Piezo means squeeze or press. In physics, scientists observed that certain cells would change dimensions when an electric potential is applied. Hence piezoelectric. This was especially noticeable with ceramic materials. Engineers found that you could stack ceramics materials in thin layers, introduce an electric potential, and create movement. All this takes place at very small scales. Piezo strategies are used in manipulating print heads on ink printers and in head phones to support the transmission of sound.
I mention these because dampening systems are likely o become more important as the average age of skiers increase. Active materials refer to materials that can react under certain circumstances. Ceramics combined with electric potential is an active material. In the late 1990’s and early oughts this combination was touted as a ski dampener. Success was limited, however, continued advancement in material sciences and active materials may lead to a rebirth or other similar types of strategies.
Steel is an easy to use material. It can be manufactured into incredibly thin sheets and even rolled. It can easily be shaped and cut. It’s widely available and relatively inexpensive. Metal components are occasionally added to skis to create durability characteristics, especially in load bearing areas. They can also be used to create spring or activeness. Occasionally a manufacturer will tout steel as a dampening agent, however, its likely its steel in combination with other materials that create this effect. Issues with metal are weight and its relative weakness compared to other alloys and composites.
Titanal (The New Aluminum)
Aluminum has a rich history in the ski industry. It was used to spur the evolution of skis from wood construction to composite construction using stronger and durable materials. But aluminum has problems, especially with aggressive forces. The forces routinely placed on skis by any high-performance skier. Aluminum is still found in skis today: for load bearing duties. But aluminum has been large replaced by Titanal.
Titanal is not your grandfather’s aluminum. Although it’s mostly aluminum, around 70%, it’s fortified by copper, magnesium, zinc, and zirconium. There’s probably other stuff and proprietary curing processes that the single manufacturer keeps secret.
How good is Titanal? A ski spends it day in action under tension, bending and contracting. Titanal’s tensile strength and elongation limits are superior to other alloys. Titanal offers low weight but high strength. It is deformation resistance and durability. Equally important it can be intgrated into the ski manufacturing process. Titanal is so good; it is the dominant industry alloy.
Cores are made up of all sorts of products and often layered. Here are some of the materials and why they’re used.
The sidewall is the area above the metal edge that contains the end of the core. Manufacturers generally pursue one of three designs: Sidewall, Cap and a hybrid.
The sidewall or sandwich construction technique involves using a hard polymer (e.g., ABS) to protect the core. In other words, the ABS becomes the sandwich bread and the core is the meat. The separate sidewall presses against the core making it torsionally stiffer. This helps create better edging. This design is used to make race skis and precision carvers. This technique adds weight and exposes the top layer to damage. However, the technique allows a ski to snap and quickly edge. Watching a good slalom skier shows how critical this construction is to the race ski.
Cap construction involves bringing the top layer down to cover the core. This technique is lighter and protects the top layer. However, it makes a ski less torsionally rigid. At higher speeds, skis using this technique tend to lose their ability to hold an edge and chatter.
Hybrid or half-cap construction uses both techniques. A thinner sidewall is used, and then the top layer is bought over the sidewall as a cap. Manufacturers can even vary this technique by using a sidewall technique in the center of the ski to create torsional rigidity and a capping technique at the tips and tails.
These techniques and why they have been traditionally used become less sacrosanct with material advancements. For example, Titanal and Kevlar allow manufacturers to create torsional rigidity with less reliance on a sidewall.
Ski edges are the metal that runs along the outside ski used to edge into the snow when a ski is tilted. There fill wraps and partial wraps. A full edge wrap completely wraps around a ski and is joined at one end. These wraps create a strong edge. However, they use more metal than a partial wrap making the ski heavier. If damaged, they can be harder to repair. A partial wrap covers the sidecut on one side. Tip and tail area have aluminum edges added. This creates a lighter ski and edges that are much easier to repair if damaged.