When skiing powder, you may have wondered what is hiding beneath the visible parts of your cross-country skis. You may have wanted to know what gives the skis their edge hold or pop.
If you have wanted to know the answer to the question “what are skis made of?” this article is for you. This ski construction guide will take you through the center of your all-mountain skis to their edges, explaining how your equipment is built and how the varying manufacturing techniques may affect your skiing experience.
How Different Ski Parts Are Built
Ski Core Materials
The core is the single most crucial part of the ski – it defines the ski’s flex and character. The most popular skis over the past 4 decades have used wood cores. Wood continues to be the gold standard when it comes to ski core construction.
Wood features a combination of properties that make it ideal for manufacturing different types of skis. The most important property that wood imparts into skis is the ability to store energy.
As the ski get weighted, the wooden core loads up. As the skier exits the turn, the stored energy gets released, a feeling commonly referred to as the “pop”. For this reason, skis featuring a wooden core are generally more responsive.
Wood features different stiffness than the surrounding plastic and fiberglass. As a result, vibrations get damped out, making the wood-core skis more stable. Compared to foam, wood features more stable properties – this means that it is less likely to degrade to lose its stiffness and ski camber over time.
The type of wood used varies from ski to ski. Many skis use varying types of wood laminated together to achieve an ideal set of handling characteristics. In some skis, the wood strips used do feature areas where other materials can be used.
Wood cores feature one major problem – they are expensive. For low-end skis or the rental market where ski performance is not a huge concern, foam is used to build the core.
While the shitfoam cores are more affordable, they feature several downsides. Compared to wood, they are less strong, they lose their stiffness and camber more quickly. Also, they lack the same rebound energy and “pop” that is generally associated with lively skis.
It is worth noting that some foams are engineered to feature exceptionally low weight and incredibly high strength. While the high-end foams tend to be more expensive, their unique combination of properties ensures that the skiers have a much better experience after putting on their ski jackets.
When used on their own, the high-performance foams may still be prone to chatter and vibration. To achieve better qualities, the high-performance foam is used together with wood strips.
A wide range of other materials is used instead of or added to the wood. These materials include:
- Carbon – This material is lively, strong, light, and performs well under compression. Carbon is extremely expensive.
- Kevlar – This material is reasonably light, strong, a good dampener, and performs well under tension.
- Aluminum Honeycomb – Very strong and light. It is, however, expensive and features reduced damping capabilities.
- Titanium – Very strong and light, with ideal dampening capabilities, but expensive.
- Fiberglass – Generally expensive. The material is, however, light and strong.
- Air – When used properly, the air is capable of decreasing the weight of the core without having major negative effects on the strength.
Composite Layers’ Materials
We wouldn’t have answered the question “what are skis made of?” fully if we were to leave out the composite layers’ materials. The composite material is responsible for giving the ski most of the stiffness. It also sticks the ski core to the other plastic components.
The composites used in modern skis feature 2 components – some type of epoxy and some type of fabric. When used on its own, each material may not be very useful. However, when used together, the materials will create a strong structure.
The epoxy is a thick and sticky liquid. During ski construction, heat and pressure are used when working with the epoxy. After solidifying, the epoxy will bond the different layers together. The epoxy also aligns the fabric fibers, gives them stiffness, and also helps them transfer loads to the other layers.
Most manufacturers use the same type of epoxy. The main differences existing between the composites are brought about by the type of fabrics used. Different types of fabrics will have different properties and cost. It is worth noting that fabric fibers can also be woven in varying ways to increase the bending stiffness or torsional stiffness.
Below, we have the common fabric materials:
Approximately 90% of all the skis, including beginner skis, use fiberglass as the fabric. The material contributes approximately 50 to 80% of the total stiffness on the majority of the skis. The material can bend a long way before breaking.
When combined with a wooden core, the fiberglass features a responsive and damp feel. Fiberglass is generally more affordable. Its major downside is that it is heavy.
If you prefer using high-end skis after donning your ski helmet and ski pants, chances are, you have used skis featuring a carbon fabric. Compared to fiberglass, carbon comes at a higher cost. However, it is much lighter for a given amount of stiffness. When using carbon, manufacturers can make the skis featuring the same flex and stiffness as fiberglass skis, but at a fraction of the fiberglass weight.
Whenever the skis flex, the skier puts the top side of the ski into compression while the bottom side is put in tension. These stresses are capable of straining the fibers. Since carbon features high stiffness, the carbon fibers are generally more prone to buckling.
To avoid this issue, most manufacturers will add carbon fiber “stringers” to the skis. The stringers are thin carbon strips that help reduce the total weight without having to sacrifice too much strength or money.
It is worth noting that some manufacturers will only use small carbon quantities when producing their skis. However, if you have to carry your skis up several thousand feet of the mountainside, it is easy to rationalize the weight decrease offered by the carbon.
Aramid is commonly known by the trade names Nomex and Kevlar. Compared to fiberglass, Aramid is lighter for a given amount of stiffness.
However, the reason why a large number of manufacturers will choose to use Aramid is the fact that it can absorb impacts and damp vibrations. If you put on skis featuring Aramid, they should offer a much better experience compared to fiberglass.
Aramid is generally expensive. For this reason, it is rarely used in huge quantities. However, the small quantities used do have a significant positive impact on the ski designs that are otherwise vibration prone or too chattery.
Although plastic does not contribute much to your skiing experience after you step into the ski bindings, it is basically what you see when you look at your skis on the rack. Varying forms of high-performance plastics are usually used to make the sidewalls, top sheet, and base.
The main function of all the varying types of plastics used is to ensure that the skis are protected from the snow elements. They also ensure that the skis are sliding easily on the snow.
For the ski bases, most manufacturers will use UHMW-PE (Ultra-High-Molecular-Weight Polyethylene). This material is available in a wide range of colors. It can be cut quite easily to form a wide range of intricate designs.
While it is possible to purchase the material in varying thicknesses, most base materials feature a thickness of only 1.5 millimeters. The most important property of the UHMW-PE is that it slides well on the snow.
There are 2 types of UHMW-PE materials used on skis – extruded and sintered. The extruded UHMW-PE is heated plastic that has been forced through a die after melting. While the process of making the extruded UHMW-PE is cheap, the resulting material cannot hold wax. For this reason, you will only find the extruded UHMW-PE on low-end skis, where the price point is more important than the performance.
Sintered UHMW-PE is made from fine powder that is compressed and then heated (below the melting point) for an extended period until it solidifies. The thin material is then shaved to achieve the desired thickness.
Waxing skis featuring a sintered base material is much easier – the sintered material has tiny pores that accept the ski wax. This results in a superior glide.
The top sheet is responsible for protecting the rest of the ski from water intrusion. It is also an ideal platform for decorating the ski. The main qualities needed in the top sheet plastic include:
- The ability to bond well with other layers.
- Good clarity of displaying the graphics.
- Resistance to chipping from the edges.
Three technologies are used when printing the top sheets – direct digital printing, sublimation, and screen printing.
Screen printing is the cheapest and most used method. Sublimation is more expensive and technology-intensive compared to screen printing. Direct digital printing requires expensive equipment but can achieve clear and crisp graphics. Unlike sublimation, direct digital printing does not produce waste.
This plastic layer is attached to the core before the skis get pressed. It gets bonded to the rest of the ski using epoxy.
When skiing steeps, the sidewall skis generally hold a better edge compared to the cap style skis. This is because there is more material digging into the snow at every turn. Also, since the sidewall is less stiff than the surrounding materials, it can help with dampening the vibration.
If you had taken a good look at your skis before asking the question “what are skis made of?”, you probably have noticed that the ski construction features some metals. For most skis, you will only find the metals on the edges. Some skis, however, will use the metals to transmit power to the edges, providing a secure platform for mounting the bindings and to reduce vibration.
These dig into the snow when you are turning. Screw-in edges are short steel sections that are screwed along the ski edges. When they break, they can be easily changed.
While the majority of the edges are made of conventional steel, you may also find stainless steel edges. These offer better performance since they do not rust during shipping and use. The stainless steel will be more expensive and much softer.
It is often important to use metal in the ski laminate, next to the fiberglass or the core. Since bending is necessary, the metal used should have the ability to flex and bend without yielding (becoming bent permanently) or cracking.
If you use your ski knee braces with racing skis, chances are, the skis have Titanal. The Titanal helps add stiffness to the skis.
While Titanal sounds more like Titanium, Titanal is an aluminum alloy and does not feature any titanium. It is worth noting that some metal laminates may feature trace amounts of Titanium.
While binding inserts are ubiquitous in the snowboard world, to allow for the bindings adjustment, they are rarely used on the skis. Some skis, however, use them as a solution to the problem of the binding screws pulling out during use. The mounting inserts also make for easy and quick adjustment of the binding-mount locations, without the need to drill new holes or deteriorate the ski structure.
Globo Surf Overview
While finished skis appear to be rather simple pieces of lightweight synthetic materials, the factors involved in ski construction are generally based on complex principles of material science, engineering, and physics. This article has already proven this.
While we have answered the question “what are skis made of?”, it is worth noting that different manufacturers will use varying combinations of the materials we have mentioned above. This will bring about the differences often found on skis from different brands.
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- Skier Need to Know — Ski Construction, Aviesskisport.com