Getting Started with Ski Construction and Geometry
All skis have a few basic components in their construction that dictate their behavior on snow. These components consist of a base, edges, core, sidewalls, and a top sheet. Different skis designed for different disciplines, or different ski companies with different technologies, may vary the materials used or manufacturing process but will all consist of these same parts.
The base of your skis is the part on the bottom of the ski that makes the most contact with the snow. This is the surface that absorbs wax, repels water, and protects the core of the ski. The bases of skis are generally made out of a material called ultra-high-molecular-weight polyethylene (UHMW-PE) and are usually only a millimeter or two thick. Another name for this material is P-Tex. Sticks of P-Tex are also what is used to repair damaged bases that have seen scratches, punctures, or other damage.
While bases may all look the same, there are two common types of ski base; extruded and sintered. Extruded bases are created by heating and melting pellets of P-Tex. This results in a one-piece base but is not a very porous surface. The lack of pores makes the base absorb less wax which will affect speed and handling of the skis. On the other hand, these bases require less waxing and are generally less maintenance than their sintered counterparts. An unwaxed extruded base will tend to be faster than an unwaxed sintered base. Extruded bases are also usually cheaper to produce and easier to repair. Extruded bases can generally be found on lower-end adult skis, kid skis, and occasionally on park skis. In the park, jibbers and rail riders don’t necessarily need to go fast and rails and other features often damage ski bases. Having an extruded base that is easier to repair would be much more beneficial to most park riders aside from riders doing big jump lines where speed is required.
Sintered bases are another alternative to extruded bases and are also made by heating pellets of P-Tex. Instead of melting the pellets down, sintered bases press together the heated pellets to make one sheet. Sintered bases are much more porous than extruded bases and absorb wax exceptionally well. When properly waxed, a sintered base will be much faster. Sintered bases cost more to produce and, as a result, are generally found on mid to high level skis. They will also be more costly to maintain since they will need consistent waxing and care. Ski bases are designed and engineered for certain types of skis as well. Race skis may have more porous bases to absorb better wax, while freeride skis will sometimes have harder or thicker bases to resist damage from rock strikes. While thicker bases are more durable, they also add a considerable amount of weight.
The sharp metal bits that run along the sides of the ski. These edges are what help you carve hard or “keep an edge”. Edges come in different shapes and sizes depending on the type of ski and style focus. A lightweight set of backcountry touring skis will generally have thinner edges that stop short of the tips. This helps cut weight and since the edges on the tips and tails never touch hard snow, they can be removed to reduce swing weight and increase flotation. Park skis on the other hand, may have thicker edges to stand up to the level of abuse they will be subject to when ground on rails and ramps. Thicker edges will be more durable and can be tuned more often. A thinner edge will wear out quicker as the ski is tuned and material is removed.
The heart and soul of the ski. The core of the ski is a key contributor to the ride feel and attributes of the ski. Most cores consist of multiple parts including different core materials and laminates.
With a wood core, pieces of wood are vertically laminated together and then profiled with a CNC or wood planar to get the desired contours and profile. Different woods provide different characteristics; common wood types you will see in skis are Ash, Maple, Poplar, and Aspen. All-mountain skis will generally be made of Maple or Ash since these are two of the stiffest and most durable types of wood used in ski cores. Poplar and Aspen are much lighter woods and can be found in skis that will be more playful and compliant. For the lightest skis, woods like Paulownia or Bamboo are used for their durable, but lightweight properties. Woods can also be blended to get the best qualities of different woods, how a core is profiled (where it is thicker or thinner along the ski) can also play a factor in how a ski will feel.
Generally used for less expensive or beginner skis, foam cores are used for their lightweight and inexpensive properties. Skis using dense foam cores are usually softer and do not provide the same level of performance as their wood counterparts. Foam cores are a great choice for children or adults who are just learning how to ski or are not charging at Mach 12 down the slopes.
Laminates are used in tandem with cores to enhance and further customize the flex, dampness, or pop of a ski. Fiberglass laminates are the most common and are used to adjust flex (uni-directional), torsional rigidity (bi-axial), or both (tri-axial). The lighter version of fiberglass, carbon fiber, is also used in high performance skis. Carbon fiber works in the same way fiberglass does, but it allows the ski profile to be thinner by negating the amount of wood core that is necessary to provide durability. Carbon fiber also works to add rigidity or “pop” to certain areas of the ski. Paired with a good ski profile, these laminates can create an extremely durable, chargey ski or a lightweight ski with generous flex. Metal laminates can also be used but serve a very different purpose than fiberglass or carbon. Metal acts as a damper and reduces the vibrations felt when skiing at high speeds or through variable terrain. Metal laminates also create a much stiffer ski and can be heavier than a similar ski with carbon fiber laminates. Other materials used include rubber, koroyd, graphene, and cork.
Sidewalls are the component found along the sides of the ski above the metal edges. Sidewalls protect the ski and contribute to the stiffness or flex as well. Most sidewalls are made with P-Tex or ABS plastic. These stiffer sidewalls are generally found in racing skis or other high-end skis where edge grip and torsional stiffness are preferred. Sidewalls usually fall into three categories: Sandwich construction, Cap construction, and Semi-Cap or Semi-Sandwich hybrids. Sandwich construction will feature sidewalls made with P-Tex or ABS and provide additional stiffness to the ski. Cap construction sidewalls are made when a composite layer rolls down off the top sheet to cover the sidewalls. This style of sidewall lacks the rigidity you would see in a sandwich style sidewall and is easier (and cheaper) to manufacture. Cap construction sidewalls are also usually lighter due to the lack of material. Some skis combine the two and utilize a half-cap which is light and snappy due to having a combination of P-Tex sidewalls underfoot and cap construction on the tips and tails. Semi-cap or semi-sandwich skis are where the top sheet rolls down over a portion of the sidewall, but then features a partial sidewall above the edges.
This is the top face of the ski where you will find most ski manufacturers incorporate art, decals, and usually have the general specs of the ski such as length and waist width labeled. Top sheets are more than just pretty, they also serve as a protective layer to prevent water damage to the ski cores. Some ski brands also have functional top sheets made of wood that add to the stiffness or flex of the ski.
Ski Shapes and Geometry
Rocker and Camber
Traditional Alpine or Full Camber will feature a fully cambered profile from one effective edge to the other. Full Cambered profiles usually have a longer effective edge which holds a cleaner carved arc and utilizes the cambered profile as a spring which offers snappy transitions from one turn to the next. One downside to camber is that the effective edge of a cambered ski seeks a firm surface to distribute the weight on the tips and tails. This can be less than ideal when powder skiing. Cambered skis also require more precise technique in bumps, moguls, and tight trees since the camber presses the edges near the tip and tail into the snow. Having the longer effective edge will help with speed and stability at the cost of powder skiing and tight turn control.
Tip Rocker will feature a rockered tip with a camber from the effective tip edge to the tail. This one-directional ski excels in maintaining flotation in deeper snow while still having the pop and bouncy feel from camber.
Tip & Tail Rocker will have both the tip and tail of the ski have a rockered profile with camber in the middle/ underfoot. This is a twin-tipped design most commonly seen in Freeride skis that require twin tips for skiing switch (backwards) and maintaining float in deep snow. Tip & Tail rocker is also a good design for park skiers since the central camber will allow for better control on rails while maintaining soft tips and tails for nose presses and butters.
Full Rocker (aka reverse camber) profiles are when the middle of the ski touches the ground and the tips and tails both arc upward away from the snow. Full rockered skis are usually reserved for powder skis that require maximum flotation in the deepest of snow. Because of the full rockered profile, these skis will have a much shorter effective edge and are not designed for hard-packed groomed runs. Full Rockered skis do not have the same pop as a cambered ski but instead will have a smooth, surfy feel between turns. This is due to the fact that the ski does not need to be flexed when entering a turn in the same way as a cambered ski would flex.
Sidecut and Effective Edge
Back in the day, skis and snowboards were just straight planks with turned up tips. Today, skis are constructed with a more parabolic shape to them. This shape is crucial in determining how sharp the skis can turn, as well as how long the effective edge will be on them. Sidecut refers to the difference in width between the tip and tail of the ski versus the waist width. The greater the difference between these widths, the sharper the turn the ski can make. So what does having a larger sidecut get you? Why does it matter where the effective edge and contact points of the ski are?
Depending on the ski terrain and skier preference, having a shorter effective edge with more pronounced sidecut can be advantageous or limiting. For someone wanting to make big turns at high speed, having longer edges with a shorter sidecut will mean better grip in the turn while maintaining speed. For someone skiing moguls or through trees, having a shorter turning radius with closer contact points will make it easier to maneuver the skis between tight obstacles. This comes at the trade-off of not being able to go as fast without experiencing chatter and instability.
Another way you may see this described is by using the term “taper”. Taper describes the ratio between the tip and the tail of the skis versus the waist width. Skis with more taper tend to be more directional while skis with less or no overall taper are better for freestyle and switch skiing. Taper is not to be confused with “Early Taper” which refers to the fattest points of the tip and tail (contact points) in relation to how close it is to the tip and tail edges of the ski.
- Effective Edge: How much edge comes in contact with the snow
- longer effective edge: More edge hold
- Shorter effective edge: Less edge hold
- Taper: The ratio between the widest parts of the ski (contact points) and the waist width
- More Taper: Less effective edge, more maneuverability and flotation in deep snow at the cost of more chatter at high speeds
- Less Taper: More effective edge, more stability at speed, and better bite while carving.
What are the main ski dimensions?
The main dimensions that you should pay attention to when looking at a pair of skis are the waist width, length from tip to tail, effective edge from contact point to contact point, and profile (rocker and camber). These dimensions will be the greatest contributor to how the ski feels when riding.
What is the best ski shape for beginners?
A good beginner ski will be shorter in length and generally have a narrower waist width since most beginners will spend most of their time on piste. A ski with a decent camber underfoot and minimal rocker at the tip and tail will also be most helpful in keeping a secure edge while initiating turns.
How do backcountry ski bindings work?
Backcountry or AT bindings differ from regular alpine bindings with one important function. Touring bindings will have pins that engage with the toe piece to create a pivot point for the ski to rotate on. This pivot point, paired with AT boots in walk mode, allow for greater range of motion to walk/glide in a more natural motion. Without this free heel and pivot, skinning would be an extremely inefficient process.
What ski shape is best?
In short, there is no master shape that is better than all the others. The variations in shape and dimensions help the ski excel in different conditions. A high speed carving ski will see minimal rocker and a very stiff construction to maintain edges while carving. A powder ski on the other hand will have significant rocker to maintain float and will have a wider waist width and be of a softer flex.
Are shorter or longer skis faster?
In general, the longer the ski the more stability you will have at higher speeds. The trade-off is that a longer ski will be harder to perform short, quick turns and will require more power to turn your skis. A shorter ski will have more chatter and less stability at speed but will be much quicker at initiating quick turns.