Cannatonic wrote:my explanation would be too confusing,
Ha! This made me laugh my friend- because I can relate! I make my living educating and training- and no matter how hard I work at it- explaining things is very difficult! Training is so much easier!
a great explanation- especially from a downhill (i.e. "Alpine") ski perspective.
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 website 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.
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...