Decamber

[www.oldsnowboards.com]

Yes. They might be credited with it though :)

[lowrider]

I once had a pair of skis that automatically decambered when they got wet in the spring slush. Wooden skis no metal edges no ptex base and non release bindings. Don't want those days back !

[kipstar]

for my riding, the older boards had a steeper shovel, no decamber, so they responded well to a forward weighting drive into each turn and heavy drive into the turn could be accompanied by the nose catching slightly in variable snow, this was particularly noticeable on some assymetric boards which tended to have a very short and tight corner on the toe side so you would drive forward and the nose could 'trip' you if you went too far forward.  With a decambered modern raceboard where the front up to 20cm back from the nose shovel is decambered so the nose starts going up from about 30-40cm back from the tip, (the nose shovel itself has been dropped down so the shovel angle to the horizontal is also lower) the board doesn't respond at all really to forward weighting, it responds to being put on edge.  The sidecut is also changed as well, since everything works in conjunction with everything else.

 

Laid flat, even my stubby, with a tiny little nose on it, has about the front 30cm which is not touching the snow at all, but once you tilt the board onto its side, the nose slowly and increasingly adds running length the steeper the angulation.  So weighting the nose at the start of a turn as the board rolls onto its edge doesn't do anything.

 

So now given that modern technique we tend to be riding the board more centered, and the board is metal and damp, the decamber serves to ease the nose of the board even more into each turn, making it even less likely to have an issue when riding in variable snow where it suddenly can catch or trip you.  That's why the new boards are so easy to ride.  But on the flip side....I believe less feel to them not solely the result of being metal, but also the geometry as well.  I did ride back to back with an old glass board last trip to try to feel the difference, and it was a lot more noticeable than I expected.

 

I find even in moderate powder (as in up to maybe knee deep) decamber is also quite good for getting some degree of float and can be ridden quite ok (for a narrow board) despite the low shovel.

Edited January 26, 2016 by kipstar

[lowrider]

 Kipstar Very good description of "decamber" effect.

[Corey]

But on the flip side....I believe less feel to them not solely the result of being metal, but also the geometry as well.  I did ride back to back with an old glass board last trip to try to feel the difference, and it was a lot more noticeable than I expected.

 

Donek has done some experimenting with this.  I rode a fiberglass freecarve board at SES a couple years ago - new school shape with fiberglass replacing metal.  That board made a distinct tearing noise in a carve and had quite a lot of pop.  Then there's the Proteus line, which is an old-school single radius sidecut with only tip decamber/rocker (tail is cambered all the way) with metal construction.  It's damp if you ride it gently and will kick you in the air if you pressure it hard at the end of a turn. 

[bigwavedave]

... It's damp if you ride it gently and will kick you in the air if you pressure it hard at the end of a turn. 

My last 2 metal boards, one Donek and one Coiler, were each based off their race construction with the only difference being a near single radius sidecut. Although they have their distinct personalities, they both have less decamber in the tail than the nose and the tail feels stiffer than the nose, so I experience the same as you describe above, which reminded me of what I observed in photos I took while judging at the local NorAm races─racers being propelled off the tail of the board into the next turn.

[Corey]

Neat stuff, Dave!  

 

There are so many things that interact together that it's hard to isolate one thing to a particular trait, thought you seem to have found that tail sidecut radius relates to pop.  That also makes me wonder if that's why I didn't fall in love with the early metal Donek Freecarve boards.  I think they had a sidecut that continuously got bigger from the nose to the tail.  I found that they carved very nicely but didn't finish the turn like I wanted and felt a bit numb.  

 

That makes me wish I had tried the Donek backwards VSR (big nose sidecut, tight tail sidecut) at SES a few years ago.  Most people didn't like it, but some said it was fun.  

[Donek]

Traditional camber boards (no decamber/rocker/early rise) generate what I would call a pressure focal point at the rise line (transitions from camber to shovel bend) in a carved turn.  This results in:

• drag or friction that slows the rider down
• a back pressure or force at the shovel of the board that becomes key in the boards carving performance
• the rider needing to pressure the shovel aggressively at the initiation of the turn
  • when reaching for the edge of the board that is off the snow, the rider will reach towards the tip of the board
• a need for a stiffer shovel to prevent the board from folding in a hard carve
• pronounced impact at this point when crossing a rut or hitting a bump in the snow (I think Brian called this greater feedback)
  • you'll see more vibrations in a board built this way as a result

Boards incorporating well engineered (insert term of your choosing to describe a bend in the opposite direction of camber) will reduce or eliminate most of the above behaviors. You will find:

• a reduction in drag resulting in a board that runs dramatically faster and is less likely to slow down in a carve
• when reaching for the edge that is off the ground, the rider will reach for a position closer to his front foot keeping him in a more stable, static centered position on the board
• the board does not need to be as stiff thus reducing the effort required to carve turns
• dramatic reduction in board chatter resulting from rutted or rough snow conditions

 

Why does Donek not use the term "Rocker"?

Rocker is a term used by the mass producers of cookie cutter snowboards and skis.  It is my belief that these manufacturers have missed the mark so dramatically on the above objectives that using the term would lump our product and my skill as an engineer in with theirs.  This is the last thing I want to be associated with, so I choose to use a term that sets us apart and invites a conversation rather than a negative assumption.

 

We offer pretty much everything from no decamber for a traditional feel to a lot of decamber in our more race oriented lines.  The amount varies depending on the board being made and the riders needs.  As always, I am more than happy to discuss this subject on the phone and help you determine the best board fit for your style.

[kipstar]

Amazing explanation Sean :-)

[philw]

I wasn't there, but here's a 2006 Kessler patent which provides some detail of the thinking behind decambering. The PDF is the original with the diagrams. I don't know if this is where decambered tip & tails started, and I know that US patents in particular are often unscientific. http://www.freepatentsonline.com/y2009/0273161.html

 

I don't know if this was the first mention of this in the literature. You could likely google it down, or maybe someone knows, I do not.

 

-------

• I like "Reverse Camber" to describe... Skate Banana type designs, which have specific uses (park, beginners, or powder for skiers).
   
• Rocker seems unhelpful and unspecific, as it's often used to describe two very different things in a snowboard.
   
• Kessler clearly needed a name for the decambered nose. I agree it's not perhaps the best name, but we're stuck with it now.
   
• Actually, we did not have much of a word for the upturned tips of yore: we didn't need one.
  Now we know how the tip should be designed, it's actually just a snowboard tip: they're all like that.
  Perhaps instead we should try to invent a name for the old shape, like: "before we had finite element analysis" or something.

Edited January 31, 2016 by philw

[ursle]

_{Well, thank god rocker showed up in snowboards in the mid 80's, and then 20 years later it showed up in skis, taking the average 200cm ski with an effective edge of 160cm and changing that effective edge to 185cm is a game changer as it is with a snowboard.}

_{It was to cool when Kessler offered a product with rocker and a hammerhead;)}

 

[BobD]

Camber beam - an upward curvature of a beam to compensate for load deflection. Skiing borrowed the term from engineering. Camber in skis, or boards is exactly that, "an upward curvature to compensate for load deflection" Decamber occurs when the rider's weight, together with the force of a turn bends a cambered board the opposite way. For something to be decambered, it must be cambered in it's normal state. Rocker is the opposite of camber, an unloaded board that is normally bent as if a load has already been applied. Why confuse these simple terms trying to simplify the concepts to the uninitiated.. 

[www.oldsnowboards.com]

THANK YOU

[bigwavedave]

Camber beam - an upward curvature of a beam to compensate for load deflection. Skiing borrowed the term from engineering. Camber in skis, or boards is exactly that, "an upward curvature to compensate for load deflection" Decamber occurs when the rider's weight, together with the force of a turn bends a cambered board the opposite way. For something to be decambered, it must be cambered in it's normal state. Rocker is the opposite of camber, an unloaded board that is normally bent as if a load has already been applied. Why confuse these simple terms trying to simplify the concepts to the uninitiated.. 

Bob, you touched on why rocker is not the opposite of camber, and not simply as convex is to concave. As you stated, camber not only refers to the concave curvature, but it's dynamic function of resisting load, it's ability to flex and return and still perform, even when decambered. I've always seen rocker refer to a static (fixed) convex curve with no dynamic load bearing implied, ie: boat bottoms, surfboards, skate blades etc. You reference the origin of camber to support your opinion. No argument there. Why not do the same for rocker?

 

The decamber (or rocker) used in the boards I've seen is dynamic─a subtle flattening of camber at the ends that changes into a noticeable upturn that looks like rocker when you stand on the board.

 

In the patent link Phil posted, Kessler uses words like concave and convex, and camber and decamber, but not rocker to describe his innovation. My argument is simply that "rocker", as used in ski marketing, is a new use that stretches the current definition. Common use will cause it to become part of the definition.

 

Obviously the cure for this thread will be more time on snow and fortunately I have an appointment with the doctor later this week.

[Corey]

Turn your head sideways to the left to make sense of this:

 

( <--- Camber, or de-rocker, or anti-rocker, or concave

 

) <--- Rocker, decamber, or convex

 

You can mix these two things along the length of a board, with cambered middle and rockered ends, or the opposite, or whatever you want.  At any point along a board, it's either flat or curving up or down.  You can call up Steve and down Clarence if that helps.  

 

What's neat about rocker/decamber in the nose is that when you tip the board up on edge, the front part is already bent and starting the turn before you or G-forces bend it into an arc.  Plus at low-angle skidding it acts like a shorter board with the nose off the ground.