If you’re buying skis, you need to know how materials in the ski’s core affect the ski’s behavior. Here’s your guide.
In Part 1 of this series, we covered how to choose a ski’s waist width based on where you ski most and what kind of terrain you prefer. In Part 2 of this series, we looked at how ski shapes affect performance. Part 3 is all about what’s going on inside the guts of a ski—how its materials, sidewalls, and bases affect its performance.
One of the important factors in ski performance is the flex—how stiff or soft the ski feels on the slopes. The appropriate flex depends on your technique, physiology, preferred turn shapes, and taste, but it is ultimately determined by the materials inside the ski.
“Stiffness comes from the ski core profile, it’s width and thickness top to bottom, as well as its materials and its construction, how it’s layered together,” says Bob Gleason, founder of The BootDoctors in Telluride, Colorado, and Taos, New Mexico. “A ski that is longitudinally stiff and torsionally strong drives down the fall line.” The softer the ski, on the other hand, is easier to flex and turn, which is better for lighter or less advanced skiers, for navigating tight terrain, and for a more playful feel.
The main structural material used in skis to control flex is fiberglass, which is basically tiny fibers of glass woven together into a fabric that solidifies when it is combined with epoxy and layered into the ski. The thickness, weave, and layering patterns of the fiberglass help to achieve the desired flex. Ski companies often have their own proprietary fiberglass modification or weave, and each has their own approach to how the fiberglass should be built into the ski.
High-end skis have full wood cores, but the layup and choice of wood creates different feels of a ski—damp, poppy, light or heavy. Many high-performance skis blend tough hardwoods with lower density woods for a strong and poppy feel. “Maple and ash provide snap and durability while enhancing torsional bite and stiffness,” says Gleason. “Aspen is a softer wood that gives a damp feeling and easier flex.” A quick-growing tree like paulownia is used to create a lightweight, user-friendly feel. Balsa and poplar primarily lighten. Learn more about Wagner wood core options in our factory tour video, viewable here.
“Most aggressive male skiers want Titanal for stiffness,” says Preston Klomparens, a member of the Gorsuch Vail hardgoods management team. Titanal is a flexible aluminum alloy that adds torsional strength, edge grip, power and dampness—but it also adds weight. Without this kind of metal, skis are usually softer-flexing and more forgiving. Since a softer ski turns more easily, many women-specific models have no metal, but according to Klomparens, manufacturers can also use lighter grade alloys to control the flex pattern.
A lack of metal doesn’t mean a lack of performance. Materials like carbon and graphene can be used in a variety of ways, depending on the type and placement, but generally they are used for both weight reduction and strength-enhancing properties. A torsion box made of carbon fiber can be soft in one direction yet strong in another, therefore making the ski soft flexing, but stiff torsionally.
Air is used in many different ways in ski design. Air provides suspension (think Nike Air) and can feel damp without adding weight. Part of the lightness of some wood cores, like balsa, comes from microscopic cells of air that the wood shock absorption characteristics, and foam core skis—which contain lots of miniscule air pockets—have a light, compliant quality. Skis can also use air pockets strategically, like air-filled inserts found in some in rockered tips or tails reduce vibration and lessen swing weight. Others engineer voids in the ski that allow for torsional strength while reducing overall weight.
Edges are typically made of tough, conventional steel and can be lighter for touring skis or thicker and more compliant for skiers who abuse their edges, like jibbers. On most high-end skis, the edges wrap around the entire length of the ski (a full wrap), while some weight-conscious models have partial wrap (where the edges run along the sidecut).
The sidewall, which runs above the edges, protects the ski and controls the energy going into it. P-tex sidewalls (found in racing skis and many high-end models) add edge grip and torsional stiffness. There is also “cap” sidewall construction, where a composite layer rolls down off the topsheet to cover the sidewalls. This technique lacks the torsional rigidity of sidewall construction, but is lighter (and cheaper). Some powder skis gain light and snappy characteristics by having a half-cap, or combination of P-tex sidewalls underfoot and cap construction in the tip and tail.
Not all ski bases are the same. They are all made from the same basic material, P-tex, although there are higher performance formulas that absorb and hold wax better than others, and some P-tex bases are harder than others. “Bases for racing usually have a high graphite content so they glide efficiently and are more porous to retain wax better. A harder base material is more resistant to rock damage,” says Gleason. Look for high grade P-Tex if your main focus is performance, and remember that thicker base materials and edges increase your ski’s durability. Interested in learning more about steel edges and base materials that we use in the Wagner factory? Check out our factory tour here.