Skier Need To Know — Ski Construction

beneath the pretty face, is a complex beast…

Design and construction of skis is, and has always been, an art. In day of yore, length and width were the only considerations in selecting a ski. Not so today. And that’s nice for us skiers. Subtle differences in materials—how and where they are applied when making the ski—and minor changes in seemingly insignificant things can make major changes in how a ski behaves and performs.

The intent of this page is not to make you an expert in ski construction, but rather to give you enough understanding so you can make better choices in selecting skis upon which to ski. Keep in mind that each manufacturer has their own way of doing things, and each professes that way as the best way, or at the least as an improved upon way. That said, each tweak by a manufacturer stems from some basics of how a ski is put together.

What is posted here, for the most part, applies to snowboards as well as skis. Our apologies, but it gets too tiresome to type out “ski and snowboard” every time the word “ski” is used.

Let’s start at the top of the ski and work our way down, then out to the sides.

TOPSHEET

The topsheet of the ski is the very top layer. That’s the one with all the great cool or goofy graphics. It’s the topsheet that grabs your eye and first brings you to take a closer look at that particular ski. You can bet lots of research goes into what will grab your eye. The topsheet however, is more than just a “pretty face” for the ski.

The topsheet provides a protective layer to the rest of the ski, especially the core and composite layers. There are a variety of materials the topsheet may be made of, and there are several ways that graphics are applied. Neither however, while perhaps interesting, make a huge difference in ski behavior or performance.

COMPOSITE LAYERS

Under and above the core, layers of composite materials are arrayed to provide the torsional strength of the ski. Torsional strength is that implied from side-to-side, resisting twisting forces across the width of the ski. These layers influence overall behavior and performance of the ski.

There is a huge diversity of materials put into the composite layers—various wood species, various metals and alloys, fiberglass, and foam. Exactly what, how, and where any laminate is designed and employed is proprietary information. Composite layers are where much of the year-to-year tinkering goes on in ski manufacture. Titanium is used one season, then a titanium-aluminum alloy termed “titanal” is used the next. The next after that might be a weave of titanal rather than a full sheet across the ski.

The purpose of all the tinkering is to achieve skis that are fun to ski, and that perform well in either specific, or a variety of conditions. Each ski manufacturer produces an array of skis suited to many different styles of skiing, different levels of ability, and differing skier preferences.

CORE

The core of a ski is the heart and soul of the ski. What happens at the core influences all other characteristics of ski behavior and performance. Almost universally, the core of a ski is made of various kinds of wood laminated together. What woods are used, and how they are laminated together, are of course proprietary secrets of the trade.

Wood is used at the core because it is light, strong, and highly flexible. Wood also is very adept at reducing vibration, thereby helping the ski be more stable. Many other materials may be added to the wood as laminates. Carbon fiber, aluminum, fiberglass, titanium, foam, kevlar, and even air, are common additions, depending upon what the manufacturer wants the ski to behave and perform like. Some materials, such as foam or fiberglass, are relatively inexpensive. Others, such as carbon fiber and titanium are more expensive. Skis containing carbon, titanium, or kevlar, are often more expensive, reflecting use of those materials.

Much research goes into what, where, and how materials are put together to make up the core of the ski. Each different combination results in different behavior and performance in the finished ski. This makes it somewhat bewildering to walk into a ski shop and then try to determine what differences exist between skis, and are those differences meaningful?

An important take home point is that as you consider a ski purchase, cost is reflected in the materials used. When you see the use of carbon or titanium, for instance, you are paying a premium for those materials. The result however, is a lighter, more responsive, more performance-oriented ski underfoot. As the adage states—You get what you pay for.

BASE

The base of the ski is of course, the bottom. Most folks shopping for skis look over the topside graphics with much interest, and give the base a quick glance, if they look at all. Which is weird because the base is where all the action is taking place. So you would think the base more worthy of considerable inspection and deliberation. But that’s not generally the case.

The base of a ski is made up of a plastic formulation called P-Tex. During the manufacturing process, the P-Tex is made into the base in two different ways—extrusion or sintering. Different additives may be used when making the base, to make the ski faster, more durable, stronger, or whatever endpoint the manufacturer is trying to get to. Additives are more commonly found in sintered bases.

An extruded ski base is, to describe it simply, melted P-Tex that is forced into a mold then cut to shape. The benefits of an extruded ski base is that they are simple and quick to make, and therefore inexpensive to make. Extruded bases are generally very smooth, and not very durable. Because they are cut from melted P-Tex, the resulting base is not very porous, and therefore does not hold wax very well. Extruded ski bases tend to be slower on the snow, because of their make up, and because they don’t hold wax very well.

A sintered ski base is a very different beast. The P-Tex is ground to a powder, then pressurized and heated to shape, then sliced to final form. This is a more expensive manufacturing process, but the result is more durable, faster skis. A sintered ski base is also very porous, so they absorb ski wax very, very well. This makes them considerably faster on the snow. A sintered base may have additives, such as graphite, which helps reduce friction between ski and snow. Ski bases with additives will be faster still. Of course, those additives end up on the price tag of the ski.

A pattern set into the ski base may or may not be present. If the base of the ski is flat, with no ridges or crosshatch markings, then no pattern is set in the base. There is no standard. Some bases do and some do not. Some have more or less patterning, and it may be straight-grooved or crosshatched or herring-boned. What’s the difference? A base with a pattern marked into it will perform better in certain kinds of snow, especially wet snow. The cuts put into the base break surface tension when running across the snow. Since surface tension increases friction, which slows the ski, breaking the surface tension reduces friction and lets the ski move faster. If your skis feel really “sticky,” especially in wetter snow conditions, you may want to have a ski shop set a pattern into the base, as noted below. In general, having some form of pattern in the base is helpful in reducing friction. See “Skier Need To Know—Waxing” for more on friction, and ways to reduce it.

The base, since it is the area meeting abrasive snow, ice, dirt, and unfortunately at times, rock, takes a beating. Small scratches are not a big deal, but gouges and deep cuts and slashes should be repaired by filling them with P-Tex then scraping/sanding them flat to the base. After a while, the base may become pretty beat up, and if you had a pattern set in the base when the skis were new, it may be pretty worn. A ski shop can grind the base using the equivalent of a very large belt sander, or can stone grind the base, if the shop is so equipped. A belt grind refreshes the base and removes small scratches and irregularities, though it does not necessarily result in a flat surface across the ski. A stone grind removes a top section of the base, creating a flat surface, and imparts a pattern into the base.

CAMBER AND ROCKER

Skis have shape related to their length along the bottom of the base. Camber and rocker are the terms used to describe this shape.

Camber refers to the arch that is formed at the center of the ski when laid on the ground with no weight on the ski. The height of that arch is a measure of the camber, though it is not a term that you hear in advertising, or otherwise. The arch, once weighted, flattens to the ground, engaging the entire length of the ski with the snow. This engagement is important in how a ski bites into and grips through turns. The amount of camber also determines how lively a ski will behave. Stiffness of the ski, a result of core and composite layers, is of course quite important in both how lively a ski is, and how well it holds a turn.

Some skis have a tremendous amount of camber, while others have nearly none. The skis behave and perform differently depending upon the amount of camber, and their stiffness. There is no right or wrong, and there is no better or worse. Only in the regard that you personally might prefer one configuration over another.

Rocker refers to, essentially, a shortening of the ski behaviorally. Rocker is applied at tip and tail. When a ski has tip rocker, the inflection point where ski meets snow in the cambered arch at the tip of the ski has been moved back towards the center of the ski. Why? Because raising the ski tip a bit—by moving the snow contact point back—makes the ski float better in powder. Extreme amounts of tip rocker will make a ski float powder quite nicely, but a cost is paid on the groomers because less ski is contacting snow in turns and the ski can become less “turn worthy.” Adding rocker, because it is reducing the effective edge of the ski in contact with the snow, makes the ski easier to tip into turns. Provided that tip rocker is applied judiciously, the ski will ski “easier” and still hold turns pretty well.

Tail rocker is the same as tip rocker, but in this case the contact point of the ski with the snow is moved forward towards the center of the ski. Why? Because this makes the ski easier to tip into and out of turns, and helps float in powder (but less so than tip rocker). Applied sparingly, tail rocker can help make a ski a bit easier to ski but with minimal loss of edge grip.

The addition of rocker, especially tip rocker, can help a ski be more worthy in the snow on a powder day. That same rocker helps ski performance when moving through loose snow, such as late in the day on the slopes when snow has been skidded into piles here and there. The early rise of the tip helps the skis engage and navigate through that late afternoon “crud.”

You may want to read the “Skier Need To Know—Skis” page for a bit more on camber, rocker, and other traits of skis.

SIDEWALL

The sidewall of the ski is that area on the sides above the metal edge. Sidewalls typically are either ABS or Cap construction. The sidewall protects the core both from the elements, and from sharp edges when skis cross or hit objects on the slopes.

ABS sidewall construction has each composite layer flat at the side edge of the ski, where an ABS plastic sidewall is then glued in place. This set up is a more expensive approach, but adds considerable torsional stiffness to the ski. The stiffness in the sidewall makes the ski have better edge grip. The down side is sidewalls add weight, making the skis heavier. And generally more expensive.

Cap sidewall construction has the top sheet brought down over the side of the ski to where it meets the metal edge. The composite layers are rounded at the top, making for a smooth rather than abrupt transition from top to edge. This does make the ski a bit less prone to damage from skis crossing, and it is lighter in weight than sidewall construction. The down side is that it is less stiff, making the ski bite and hold in turns less effectively, especially at higher speeds.

Some skis see a hybrid sidewall design that combines both. Cap construction is generally seen towards the front and rear sections of the ski. ABS sidewall construction will be found in the center of the ski, under the binding, where added stiffness will provide improved performance in the turns.

SIDECUT

The days of straight skis are all but gone. Pick up any ski and you will note an hour-glass type shape with a more slender waist or mid-section, and greater width at front and rear. That curvy shape is called sidecut. Sidecut encourages skis to turn when tipped on edge. Each ski will have a sidecut radius designation—15 m for instance—that gives an indication of how tight a turn the ski is designed to make. This does not mean, as in our example of a 15 m sidecut (about 45 feet), that when you tip into a carve you will travel in a 15 m radius circle. Theoretically perhaps, from an engineering perspective, but we ski and ride on snow, not engineering theory.

Look at sidecut radius as a guide to how “turny” a ski will be. The larger the sidecut radius number, the less “turny” the skis will be. The smaller the number, the more “turny” they will be. If you want a pair of skis that are very good at making quick, sharp, aggressive turns, look for one with a small sidecut radius number. Want a pair of sticks that act big and floaty, and are great at making wide, sweeping turns down big, wide ski slopes? Look for a large sidecut radius.

EDGES

Those metal edges gracing the sides of skis are of extreme importance. They bite into the surface of the snow and hold on through turns. And to do that those edges must remain sharp. See the” SWIX Tuning Center” page for edge sharpening tips. Also important is the bevel set into the edge at both the base and side.

Edge angle varies from 90 degrees to 87 degrees, though racers may set angles well below that. Base and side angles are set by the manufacturer as the skis are produced, and can vary between brands and models. That said, most are in that 90 to 87 degree range. If you want to know the factory set side and base edge bevels for your skis, you would need to go online and hunt down the technical specifications for your gear.

Base edge bevel is generally not one thought of when someone says they got their edges sharpened. A typical skier never messes with base bevel. In general, that base bevel may only be set 1/2 degree to 3 degrees from flat. It doesn’t sound like much of an offset, but having a bit of bevel at the base will help the ski tip onto edge just a bit easier.

Side edge bevel is more commonly considered, though most skiers have no idea what degree their side edge bevel is set at. Most side edge bevels range from 1 to 3 degrees from 90 degrees. This makes it a bit easier to get the ski up on edge, and provides better holding power throughout a turn. Why not crank up that angle to 5 or more degrees from 90 degrees for great holding power? Because it then becomes increasingly difficult to pull the ski out of a turn. So yes, too much side edge angle can be a bad thing.

For most New England skiers, a 1 degree from flat base bevel, and a 2 degree from 90 degree side edge bevel is suitable. That combination provides an assist getting the ski up on edge but does not make it difficult to release the turn. And that combination provides pretty good holding power in the often crusty, icy conditions found on New England ski slopes.

The key to having those edges continue to work in keeping you stuck to the snow during turns, is to keep them sharp. It doesn’t take much more than a diamond stone and a few minutes after a day on the slopes to keep them sharp and shiny. See “SWIX Tuning Center” and “Skier Need To Know—Waxing” for more on edge maintenance.

CONCLUSIONS

Let’s repeat an earlier message—cost is reflected in the materials used. When you see the use of carbon or titanium, for instance, you are paying a premium for those materials. The result however, is a lighter, more responsive, more performance-oriented ski underfoot. You get what you pay for.

Ultimately, the best way to understand if differences between skis is significant, for you, is for you to take them out on the hill and ski on them. One option is renting a pair of demo skis. Several times each season ski manufacturers offer “Demo Days” on mountain where you can go and try out their skis for a few runs. This provides a great opportunity to try out and compare, side-by-side, multiple pairs of skis.

The ski techs at Avie’s Ski / Sports can help in this regard. They have skied on most all the skis in stock, have talked to each other and other skiers about how the skis behave and perform, and have talked to the manufacturers about the skis. While it may not be quite as good as taking a pair of skis out for a spin, it’s a good start. Avie’s Ski / Sports does have Demo Skis available for trial.