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Ski Camber and Rocker

Posted: Wed Dec 13, 2017 11:26 am
by Johnny
All the different modern ski profiles

Source: Wagner Custom Skis
Ski Camber

Up until the early 2000s, most skis had one thing in common: ski camber. But what is camber, and how does it compare to rocker or early rise? Here, we take a closer look at ski rocker and ski camber and how these elements play a role once you hit the mountain.

To understand rocker and camber, it’s best to picture a ski on a flat, hard surface with the base side down. Traditional skis make contact with the ground surface in the tip and tail sections while the center of the ski is arched upwards. The two contact points often correlate to the widest parts of the shovel tip and tail. The section between these two points is essentially the ski’s effective edge. A ski’s effective edge is the section of ski that is used to make a turn, it is the length of the edge in contact with the snow when the ski is carving through a turn. As a point of reference, traditional race skis have significant camber, which helps ski racers track well on hard snow and initiate fast turns.

Traditional Camber

Ski camber reflects what you are picturing for a traditional ski, as seen in the figure above. With this ski shape, you have a longer effective edge. This translates to a more stable and controlled ride when skiing. Why? When you weight the ski, and initiate a turn, the forces you use distribute along the entire effective edge of the ski. In effect, much of the edge pressure applied to the snow is transferred out to the shovel and tail. This provides better stability, better edge grip, and precision on hard or icy surfaces. When you press the tip into the snow to help the ski “draw” into the turn, the effect is accelerated in a cambered ski, especially in moguls, where the shape of the camber helps maintain contact with the downhill face of each bump. Taken together, the longer effective edge holds a cleaner carved arc and offers a snappy transition into your next turn.

Ski Camber Pros:

    - Ability to carve turns
    - Precision when carving
    - Stability throughout a turn
    - Good edge hold and/or grip
    - Quicker edge engagement when beginning a turn with forward pressure
    - Better traction at high speeds on hard and groomed snow
    - Good traction when skinning uphill (ski touring)

Ski Camber Cons:

    - The effective edge seeks a firm surface (at the bottom of the snowpack), which translates to challenging powder skiing unless you can carve consistently in variable snow.
    - Skis require precise technique in bumps and tight trees

Reverse Camber

Now picture a ski laid flat on the same surface. This time, the shape looks more like a water ski. The middle of the ski touches the surface and both ends arc upward, away from the snow. This shape, as seen in the firgure above, is what the ski industry refers to as reverse camber. In the 1970s, a few skis were built this way so as to concentrate the skier’s weight in the center of the ski for easy steering — they were sold to ski schools for use by first-day beginners. The first high-performance reverse camber skis, and possibly the most famous, were the Volant Spatula and K2 Pontoon. While these very wide skis had their time to shine, they are generally not recommended unless you are skiing perfect conditions (i.e. bottomless powder) all the time.

Reverse Camber Pros:

    - Great flotation for deep powder conditions
    - Perfect for helicopter skiing and snowcat skiing in perfect, bottomless conditions

Reverse Camber Cons:

    - There is essentially zero effective edge which means carving a turn is very difficult if not impossible
    - Feels like you are skiing on roller blades (side note: we have nothing against roller blades)
    - Bad for traversing

Tip and tail rocker

Rocker, also referred to as early rise, is the happy medium between a full cambered ski and a reverse camber ski. Picturing the same ski on a flat surface, rocker is when the center of the ski has mild camber, but the rise, or upturn, of the ski begins behind the ski’s widest point (closer to the bindings). Similarly, rocker can be built into the tail of the ski.

The designer may give the ski symmetrical rocker (similar at the tip and tail), or can build in more rocker at the tip, or more at the tail. The more rocker, the shorter the effective edge becomes. This shorter effective edge correlates to a longer “rise,” the portion of the ski that doesn’t make contact with the snow.

Skis with a cambered center and tip rocker are a really good balance for many skiers, and have been very popular the past few seasons. It’s important to note that a little tip rocker can go a long way.

Tip Rocker Pros:

    - Improved float in soft or variable snow (sun and wind crust, choppy snow, etc.)
    - Easier turn initiation
    - Better ability to stay in a centered and balanced stance which helps you plow through snow
    - Helps a longer ski maneuver like a shorter ski
    - Will save your legs in deeper snow
    - Makes ski touring (skinning uphill) easier and more controllable

Tip Rocker Cons:

    - The tip of the ski is prone to vibrations as you ski
    - Skis don’t track as well on groomers and hardpack

In contrast to tip rocker, tail rocker is denoted by the tail section of the ski rising off the ground closer to the binding. This also reduces the effective edge, and increases the length of the tail that’s not making contact with the snow. This feature makes the skis feel softer.

Tail Rocker Pros:

    - Good for surfy skiing
    - Allows for easy pivoting
    - Easier turn release in soft or deep snow

Tail Rocker Cons:

    - Reduced tracking stability in long turns
    - Less backbone and energy when turning
    - Loss of stability and edge grip on hard snow

What does this all mean when evaluating or purchasing skis? In 99% of ski designs, camber is a good thing. It creates more versatility, with better edge control and stability, when you need it most. Camber helps especially well when skiing at high speeds, traversing across slopes, and skiing on firm or icy slopes. Having an effective edge is good: It helps you control your turn and gives you power. Camber combined with tip rocker generally makes a more versatile ski. These two features combined allow a skier to stay balanced, and lets the ski do more of the work when plowing through soft, variable and deep snow.

While ski camber and rocker affect the way a ski performs in various conditions, it is important to note that other factors affect the ski as well, including ski geometry (length, width, sidecut radius), stiffness, flex pattern, and materials. As a rule of thumb, camber is a good for versatility. Skis with camber and some tip rocker work well for all-mountain resort skiing. Skis with tail rocker are generally best for soft and deeper snow conditions

Nordic and Telemark Perspective
Source: LilCliffy The Great

Part of the difficulty in explaining/describing it is that the type of camber profile is only one dimension in the physics of a how a ski functions when pressured by the skier. Camber profile, stiffness/resistance, flex pattern, sidecut profile, and construction materials all interact in a synergistic complex. Ski design and development is both a product of engineering as well as art. Amazing really.

As the above so clearly explains, the function of camber from a downhill perspective is to produce an effective edge: "A ski’s effective edge is the section of ski that is used to make a turn, it is the length of the edge in contact with the snow when the ski is carving through a turn. As a point of reference, traditional race skis have significant camber, which helps ski racers track well on hard snow and initiate fast turns."

The Nordic skiing spectrum is much broader and deeper than the "Alpine" spectrum.

At the XC-focused end of the Nordic spectrum, the function of camber is about effective diagonal stride or "kick and glide". The combination of camber, stiffness, and flex pattern are designed to both offer enough for an effective downward "kick" and release; as well as an effective "wax pocket" that is intended to keep the wax/traction zone of the ski off the snow during the glide phase. At the extreme end of this spectrum are very stiff, highly-cambered Classic XC racing skis- designed for a Classic groomed race track.

Double-cambered skis designed for backcountry/off-track snow must have a softer flex otherwise it can be impossible to effectively engage the wax/traction zone of the ski- you just end up driving the tip and tail downwards without engaging the wax/traction pocket with the snow. For example, even my mellow track touring skis (Atomic Motion) are way too stiff for ungroomed snow. By comparison, my E99s have a full double-camber, but have a wonderful flex for fresh, soft snow- they still require good technique, with an effective kick...

For non-XC skiers even the softest-flexing double-cambered skis can be a bit frustrating to begin with. My wife for example- an expert Alpine skier- much prefers our softest and least-cambered skis (e.g. Eon/E109/Ingstad) over truly double-cambered skis (e.g. E99).

What some- including me- describe as "camber-and-a-half", is really a double-cambered ski, where the second camber is very low profile. Examples of skis that I own that all have this low profile second camber include the Eon, E109 and the Combat Nato (the S-Bound 78 that I tested years ago had this profile as well). Skis with this camber profile do not have as effective a "wax pocket" as a fully double-cambered ski (e.g. E99/Glittertind/BC70/Amundsen), but they do offer a much more effective downward "kick" and release than a single cambered ski. Each of these skis can and do have different degrees of stiffness/resistance. For example, the Combat Nato and the E109 are both stiffer than the Eon. I like pushing/pressuring my skis quite aggressively- I prefer the stiffer flex of the Combat Nato/E109. Many skiers prefer the softer flex of the Eon- especially when making downhill turns. The "camber-and-a-half" profile, from my perspective, allows a traditional Nordic touring length, with effective kick and glide performance on fresh, soft snow; while offering better climbing and turning performance than a fully double-cambered ski.

A double-cambered ski will have a second camber that completely resists being compressed- designed to offer a powerful kick/release, as well as preserve a "wax pocket" when gliding forwards.

A single-cambered ski does not have that second very resistant camber. The single camber is designed to produce an effective edge- as described above.

From a fundamental perspective- single camber's primary function is effective edge in a downhill turn; double camber's only function is powerful and efficient diagonal stride when XC skiing.

Salomon's complex DNA Ski ID system for measuring camber (Click to enlarge)

One context where things get blurred is in bottomless powder snow. Even the softest double camber ski will not work effectively in this context. The snow must be dense enough to support the tip and tail of a ski for a true kick to work with a double-cambered ski. Single-cambered work better as XC skis in bottomless powder than double-cambered skis. If I am going for a long-distance tour in bottomless powder I take my 195cm Annums- not my 210cm E99s. At least theoretically a camber-and-a-half ski could perform in bottomless powder. The only 1.5-cambered ski I have tested that does well in this context is my 210cm Combat Natos- it competes with my Annums in this context. Both the Eon and the E109 suck in bottomless powder (Although if you are light enough- like my teenage daughter- the Eon does work!)

Different manufacturers have and continue to take different approaches to the whole hybrid "XCD" context. For example, Fischer's S-Bounds have a fairly high (higher than a typical downhill ski) single-camber. The S-Bounds also have a relatively stiff flex (progressively softer, with increasing width- to correspond with ever deeper, softer snow). I can only assume that the S-Bound complex of camber, flex, and sidecut is to allow a "short" Nordic ski for a tight turning radius; with a relatively stiff flex to offer some reasonable XC performance. The Karhu/Madshus XCDs are different again- the Epoch and Annum also having single-camber, but with a much softer flex than the corresponding S-Bounds (98,112). Some skiers prefer the S-Bounds, some the Karhu/Madshus- what works depends entirely on the individual skier's context- weight, performance preferences, terrain, tree cover, snow conditions, etc.

I know that many skiers have, and continue to, downhill ski with fully-double cambered skis- myself included. Suggesting that a double-cambered ski is "better" for downhill skiing doesn't make sense to me...Unless one is using a non-XC length (i.e. a SHORT double-cambered ski). From a XC perspective, an effective "wax pocket" means that the camber underfoot cannot be fully compressed when both skis are equally weighted. If one can fully compress the camber of a double-cambered ski, when the skis are equally weighted, then the skis are too short to offer an effective wax pocket. I do ski downhill with my current 210cm E99s, but I do not make pretty, equally-weighted telemark turns with them. I initiate turns with a striding technique, and much of the time, most of my weight is on one ski, and then the other. I use my E99s when the context makes them the most efficient and FUN ski- long distances and a stable base to support the double camber. If I want to carve true downhill turns then I much prefer my single-cambered and camber-and-a-half skis.

At the other extreme, one can have a stiff single-cambered ski that is too long for the skier. Again if the camber is not compressed when both skis are equally weighted, then one will have to put most of their weight on one ski to produce an effective edge...

To sum-up from my perspective, in terms of intended function:

1) single camber function = effective edge= downhill turns

2) double camber function = effective wax pocket= XC diagonal stride

3) camber-and-a-half function = balance between effective edge/wax pocket = xcountry and downhill performance

Re: Ski Camber and Rocker

Posted: Wed Apr 25, 2018 11:33 am
by lilcliffy