Camber - or lack of it - weirdness

A snowHead

'lovely pop out of the turn....'
'riser front and tail, with traditional camber underfoot...'

I am familiar with this. I am used to skis with camber.

Then....

...last year I bought a Jones Mind Expander board for the Grom. This is banana shaped. He floats around the mountain on it. surface riding the powder whilst others are waist deep. It's a hoot.

Then I found some reverse camber skis - 2018 Mantra Youth in 158 (86 waist) and since I am 5-7 and 130 lbs they were OK for me. They are doing my head in. In a very good way, not a bad way.

This Christmas' crud and slop - they rode up like surfboards and took me over everything. No diving, no being thrown this way and thither. Nope, just point and they go over everything like a boat on water.
Want to turn - oh, they already have.
Get some air off a mogul - they land so very softly. Nice.
There's no way that they will carve - wrong; tilt them and they engage immediately....and then rail around.
No grip on ice - on the contrary, they are sidewall skis, and once you engage the tip you are locked in. Brilliant.

So I began to hunt, and found Faction, with 2mm camber - er that's really no camber at all. Whitedot...with really very little.
I am beginning to wonder about camber....is it the essential design feature which all skis must have? Or maybe not?

A snowHead

Of course positive camber isn't essential but I don't suspect many racers are going to be giving theirs up soon. Bear in mind you are very light and thus may well be not as used to decambering a ski simply by standing on it

Well, the person's real but it's just a made up name, see?

I agree reverse camber skis are far more versatile than they should be. My massive DPS Spoons only have a 40cm running edge on hard snow, but they hold on remarkably well (I wouldn’t recommend trying to hold an edge on ice though Shocked

).

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@valais2, It's a valid question. I'm not quite sure what +ve camber actually achieves in a *modern* ski? I mean, when solid wood, hand shaped, well, yes, to encourage longevity of spring ... but these days you just get your materials right. And the actual elasticity was never very much, the old (very old) test of an "appropriate" skis (which was probably nonsense anyway) was to be able to pull the two skis together with index finger and thumb. Functionally meaningless I would submit.

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As above, I believe the clue is in racing and use of edges in that environment.

The camber presents the ski to the snow surface at proscribed ski edge length more consistently over skier vertical mass difference relative to snow surface in vertical plane.
In compression and lift of skier mass the end part of the ski edge applied to flat surface is very repeatable from full buried out compression to just coming back into contact from airborne to give the racer absolute consistency of response and radius the ski is designed to work at.

Coming back from that full out speed and bleeding edge competition performance it would seem less and less critical if you don’t mind shift in character for different surface conditions.

In other words, if you put a GS racer on full rockered ski, then what would their performance look like ? In pure pace, it would be unlikely to match tge traditional.

This setting in mtb would be suspension sag on full suspension bikes (well cars and motorcycles too) in that you try to keep consistent geometric contact to the surface as far as possible, also assists landing from air as the damper has effectively a longer stroke to use in arresting mass, that similar to a small extent in landing a heavily cambered ski.

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Similar outlook to you @valais2, in that I've used odd, outlyer skis for years that other's have strong opinion of, to the negative often.

Early adopter of Salamon 1080 (hired a pair in La Tania when they first appear) and couldn't believe just how different they were in comparison to conventional direction of what I should be using. Bought some a year later and still got them. Everyone will shout "noodle" while pointing at them, with no idea of what they are really like.

Bought some head Monster 88, 1st iteration, that had the binding centre point very far back, with at the time huge long flexible shovels with early rise gemoetry. They performed well on piste but as you described "like riding in a boat" at the end of the day in warm chopped mash and giant mogul, you could plot a course and they'd sail serene through anything, you could sit back and enjoy the ride.
Skiing friends don't particularly like either of these, with the fronts to wayward for their liking.

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@ski3, I just don't see that, given how little force is required to put the ski flat.

I mean, sure there is definitely an argument that if it wasn't competitively useful, it wouldn't be there, but ...

After all it is free

@under a new name, ...yep, if the force needed to pull the skis together is so low, if can’t see how this contributes to the idea of ‘pop’ at the end of a turn - the amount of force needed to launch me nicely into the air is not going to come from that...it’s far more likely to come from holding the edge at an angle to my direction of travel at the end of the turn - keeping the edge in - and then me deliberately forcing my body up off that solid platform .... I think a lot of things may have been attributed to camber which derive from very different elements of the complex physics of skiing.

Interesting analogy with sag in mtb and DH suspension - regret a specialist subject of mine, since I was involved in full suss mtbs since day 1 - Thinking it through the principle function of sag is to place the unsprung mass in around 30% of the travel so that the wheel can move DOWN into holes as well as UP over bumps. The whole point is keeping the contact point consistently in contact with the ground. I am thinking through the analogy ... does the camber keep the right tension in the ski to present a consistent edge to the snow? In which case my lightness means that all I need to do is tilt the ski and go....which is what it feels like...

I suspect it's probably just a case that manufacturers have found that in their experience having some camber provides a better balance between the ski stiffness and responsiveness when skiing dynamically.

The two examples above suggest that some negative camber (and maybe a softer ski) tends to makes a ski that feels easy and relaxed. It doesn't seem too far a stretch to suggest that traditional camber (and maybe a stiffer ski) tends to make a ski that will feel more dynamic and responsive.

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@olderscot, ...and according to some, Volkl experimented in the market with these reverse camber skis and they didn’t sell well ... they are now sneaking them out with the label Mantra (flat) .... which is fine

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@valais2, except the current M6 has mild tip and tail rise and +ve camber in the middle ...

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Is anyone doing 3D bases in skis yet, or is there just too little real-estate under there for that to make any difference?

You know it makes sense.

Skis are different from snowboards though. And races are different from deep back country snow.

I think snowboards are heading back to camber. The banana thing came and went, at least from what I see. In my experience in powder, moderate reverse camber was tolerable but didn't do anything particularly useful.

Heli guides ride reverse camber because they're easier to ski. Punters use them because they can sit back. They're a bit tougher to use on packed out traverse run-outs through the woods, and sideways on windslab.

I reckon it's all good: people should try different things as it's fun.

No reverse camber, no turned up edges in this one. This is a 144 "sinker" maxed out.

Otherwise you'll just go on seeing the one name:

A snowHead

@Arno, you are looking for Young's modulus https://en.wikipedia.org/wiki/Young%27s_modulus. Linear up to a point.

Indeed, @ski3, a ski's construction ises different materials in different shapes. I'd be amazed if it were linear.

I still don't see the value in +ve camber. My skis go flat just lying on the ground (and they're quite rigid).

A snowHead

Interesting, thanks

I'd always understood that the camber was intended to equalise the pressure along the length of edge in contact with the snow but that may or may not have had any basis in fact

Well, the person's real but it's just a made up name, see?

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@ski3, Back in the late 80s there was a minor revolution in slalom skiing (can't recall the details) but it was driven, at least in part, I think, by the likes of the Rossi 7S having much more torsional rigidity than previous skis. Certainly the 7S was much more rigid than it's 4S predecessor, with an accompanying improvement in grip.

I can't see that cm or so of camber equalising anything. Almost all the pressure when flat is under foot and you're way into negative camber when turning at any speed.

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@ski3, …that makes a lot of sense. The extent to which Volkl has held on to sidewall skis is interesting - obviously high end producers like Whitedot do this, but it’s interesting the extent to which a large provider has done so (Kenja, Kendo etc).

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@valais2, I'm not sure it has a lot to do with sidewalls? Nor that they are unusual? My Movements (98 Go) and Bonafides have sidewalls, as do most or all Black Crows?

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I think this comes down to the right tool for the job. The camber adds additional range to the flex and also stiffness (I.e. amount of pressure required to flex the ski). The reason that works for high speed on firm snow is the ski needs to cope with relatively higher forces. The camber has little benefit in other circumstances though, and is actually detrimental in some. And to my mind is also a bit wasted on anything but the stiffest/most piste oriented ski, its probably of most benefit in race skis and their “near race” equivalents (the heaviest/stiffest piste skis). If you are a less aggressive skier (or just lighter) I don’t think camber is necessary in the design of a ski that flexes predictably and stably when carving on piste.

After all it is free

As pointed out, the construction is hardly simple, so looking the Young's Modulus of a single layer may or may not be linear, but you have multiple layers anyway. And even a single spring can easily be made non linear: imagine what would happen if a spring's thickness reduced along its length, for example. With a composite, you've a lot of control of that. That's partly why skis are composite!

@phil_w, but lying on the ground they're flat, not in +ve camber. And I just don't see what the +ve camber is contributing during a turn Puzzled

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@under a new name, my piste skis are definitely not flat lying on the ground, there is a noticeable gap caused by the camber. They need pressure to lie flat, quite a bit actually.

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@under a new name, yep - Black Cs, upper range Dynastars etc - and this I thought adds a lot of torsional stiffness compared to a (cheaper) cap construction since the material over the skis gives this quality…I thought….

@zikomo, maybe mine aren't either! haha. I'll look properly next time.

@valais2, I don't think it adds torsional rigidity, as such, in and of itself.

You know it makes sense.

@ski3, interesting, now I see your thinking. Hmm, yeah, plausible?

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A snowHead

I find it fascinating in what they put inside these ski.

Splitting it down, if you took a thin sheet of balsa wood in ski proportion and bonded a carbon composite sheet to top and bottom to make a sandwich, then let it cure obviously.

Now if you bend that along it's length it tries to stretch one sheet and contract the other, resistance coming from the balsa structural integrity plus the layer bond strength. This similar to a railway girder bridge, the bigger the separation of those two outer layer in distance, the more resistance the structure has to that bending. That's as long as the substrate and bond can hang with the stresses they're asked to do.

Now if you twist that same first constructed sheet torsionally, those plain stress lines cross over in the middle of the assembly to give a long X to the four corners. If you just add a single carbon composite X bonded in that pattern the torsional will rise in resistance greater than the longtitudinal flex (conventional ski bending) where as if you lay instead of that X a layer in shape full width centre of ski then tapering to a point back and front, the flex resistance rises more or less independently of torsional performance.
Mix these two attributes and you can play with those qualities in balance to one another.

If you simply increased the first iteration of three straight layers by just doubling the balsa wood thickness, then the difference in curve when bent rises from top layer to base layer to fit the same radius of bend as before. Again, if the bond and structure can support the loading, this will make a much harder to flex sandwich.

A balsawood form being thickest in centre of length with thinner ends, then with the two layers top and base will then give a variance of spring rate when measured as you test from tip and tail toward the centre because of the layer geometry above.

Combine all three construction and you're most of the way there to a ski.

A snowHead

Well, the person's real but it's just a made up name, see?

IMV. The Camber puts more pressure onto the Tip and Tail - which should help engage the Front of the ski at the start of the turn and the Back of the ski at the end of the turn.

Secondly, pressing forward (and across) at the start of the turn, "loads" the ski into reverse camber, which adds power to the turn if the timing is correct.

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@zikomo, And I've just realised that I am definitely talking nonsense regarding my skis being flat just lying on the ground as most of the time they're actually sitting up on their brakes Embarassed

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@Old Fartbag, yebbut, the actual tip/tail pressure is vanishingly small.

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Then you can post your own questions or snow reports...

@under a new name, tip and tail pressure should be equal to the amount of of pressure/weight required to deform the ski to flat.

After all it is free

I think also that the pressure needs to be consistent along the entire running length, or the ski will break away where the pressure's less. Hence decambered noses and torsional stiffness. They dick around with the stiffness at tips especially to stop them vibrating: it's not just "stiffness" which matters, it's also "damping". For completeness, the sidecut profile also has some input into this.

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@Richard_Sideways, yep, so a gentle pressure between thumb and index finger.

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Camber - or lack of it - weirdness

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