Today’s skis have come along way from the wooden barrel staves and leather straps that marked their origin in the 1920s. In case you don’t have a degree in mechanical engineering, we’ve created this crash course in slalom ski design; with a more thorough understanding of a ski’s inner workings, you’ll be better able to pick the ski that’s right for you and enhance your on-the-water performance.
MAJOR DESIGN COMPONENTS
Today’s slalom skis are finely tuned machines. Five primary components – bevel, concave, flex, outline and rocker – work in concert to determine exactly how a ski will behave in the water.
1. Bevel: The edges on the side of a ski where the flat side wall transitions to the ski’s bottom. Bevels can be sharp and flat or soft and rounded. Sharper bevels offer more speed and stability when riding in a straight line, and they track more in the turns. Rounded bevels offer more control in the turn, with less speed and stability when tracking. To provide a blend of both sharp and round bevels, some manufacturers now incorporate several small radii along the edge of the bevels.
2. Concave: The U-shaped tunnel running along the ski’s bottom that allows it to grip the water for increased stability. A deeper concave provides a solid grip on the water but decreases speed. Shallow concave is faster and allows for harder turns when on edge. High-end skis typically feature a shallow concave that runs continuously from edge to edge. Some manufacturers have begun adding small, flat rails on the outside of the concave to give skis with shallower concaves more stability without sacrificing speed and edge control.
3. Flex: The amount that a ski flexes along both its length (longitudinal) and width (torsional). A highly flexible, or soft-flex, ski will turn more easily and ride smoother in rough water, but will be slower when riding straight. A stiffer flex offers increased speed in flat water, but is more challenging to turn.
4. Outline: The outside shape and width of a ski from tip to tail. Wider skis are more stable and easier to stand on during deepwater starts, but they’re less nimble. Narrower skis are less stable but can be easily put on edge for sharp, controlled turns.
5. Rocker: The amount of curvature in a ski from tip to tail. A flatter ski with minimal rocker is faster and more predictable, but has a longer turning radius. Adding rocker allows for tighter turns, but too much rocker makes the ski slow and can cause tip rise. Most skis have one or more flat spots in their rocker, allowing for fast skis that turn with ease.
Modern slalom skis are constructed with several different materials, depending on who they’re being designed for and what the retail price will be. A ski’s foam core is made from either polyurethane (PU) or polyvinyl chloride (PVC), while the lamination that’s wrapped around the core is made of fiberglass, carbon or a blend of the two.
PU cores: All but the highest-end skis have PU cores. This foam is either injected into a mold or cut from foam blanks to shape the core. PU is slightly heavier than PVC but also quite a bit less expensive.
PVC cores: Ultrahigh-performance skis have PVC foam cores. These cores are cut from flat panels of foam into the desired shape using CNC machines. PVC is about a pound lighter than PU and can be cut with extreme precision, providing for increased consistency from ski to ski.
Despite carbon’s benefits, the vast majority of water skis today are still made with fiberglass. The reason? Carbon is extremely expensive, so it’s used only for the top-of-the-line designs. But fiberglass offers more than just a cheap price: It absorbs vibration better than carbon and generally produces a smoother ride.
The ultimate high-performance slalom skis have PVC cores that are laminated with aerospace-grade carbon fiber. Carbon is much lighter and stronger than fiberglass, so not only will the skis be faster but they’ll also last a lot longer and hold their flex much better over time.
Since carbon has so many advantages, most manufacturers have intermediate-level skis made with carbon/fiberglass blends. Typically, the higher a skier’s ability level, the more carbon in the blend. In the past year or so, some manufacturers have also begun adding some carbon to all of their skis, even beginner models.