20m SCR

[yyzcanuck]

Yeah that works great for railways, roadways and rollercoasters where gentle deceleration comes into play when entering the turn. However, I believe that has little or nothing to do with why the shape is used on a snowboard.

I still believe the sidecut shape has very little to do with how (why?) the 'new school' snowboard works. I think that when you look at a snowboard's shape (from the top) manufacturers could use many different shapes "such as ellipses, K©lothoids, parabolas,...". I continue to challenge you (Bola) to prove to me that it's the K©lothoid that makes the Kessler exceptional.

I stand by my statement primarily because of personal anecdotal data collection. I've ridden boards with K©lothoid (Kessler) and blended radii (Coiler & F2). They perform similarly, therefore... it's not the sidecut shape that makes or breaks the design.

The most important part of the new board shapes isn't the sidecut shape at all, but rather the interaction of the choice of sidecut radii (yeah, blended radii, or K©lothoid, or parabola, or... or...), the choice and positioning of cambers (tip, middle, tail) and the forces of rider weight & board inclination coupled with the board's flex pattern.

The above items are what make the 'new school' designs easier to ride, hold their edges better and track cleaner lines. It's a totally dynamic, 3 dimensional interplay. The heavily loaded contact area, that on a traditional design snowboard stays at the point where sidecut is blended into nose & tail, is now moving along the sidecut and the nose and tail are rising and falling dependant upon loads and inclination. K©lothoid be damned!

Just a sidenote... was the Parabola named after you?

[Jack M]

I could maybe understand a symmetrical curve with the tip and tail having a radius that's larger or smaller than the midsection. I think the difference between tip/tail radius and waist radius would be pretty small, but I can see reasons for doing that (reasons for making the tip/tail a larger radius, and reasons for using a smaller radius... :) ).

But, I got the impression that the "new" boards had tight-radius noses and long-radius tails.

Did I just misread something?

You didn't. It works surprisingly well in several ways. When you're bending the back of the board more than the front, like in the end of a turn, it makes sense to put a longer sidecut back there. And you can manipulate it in other ways too, it's almost like having two boards in one. I need to put more miles on mine before I can elaborate further, but I am a believer.

yyz - someone pointed out here once that the difference between a radial sidecut and a parabolic sidecut is so slight that it can be destroyed by heavy-handed sharpening. So I think you could be right that the difference between a clothoid and a 2+ radius blend or other shapes could be insignificant. The interaction of all the 3 dimensional shapes of the board and the flex and materials matters most. When there is harmony between them, you'll have a good board.

[BlueB]

??

Unprovoqued tread resurection... This is going to be fun., where's my popcorn? :D

I must say that I noticed, when riding Kessler BX, on good carving snow, that my track is often super tight at the initiation and opens up gradually through the turn.

[snowboardworm]

WOW!! i had no idea when i got into this forum that i would so be drawn in to the antics of some of the posters. I'm a softboot instructor of several years who enjoyed teaching grades 7-8 how to snowboard. Due to my current location i can only dream about sliding down the hill to experience my curves. my only solution to this is earning my turns. i'm a newbie to hardbooting and also just picked up skiing and luuvvv the sensation of real speed. i picked up some voelkl race tigers this year so i can hit the slopes in silverstar and sun peaks while on holidays. i have a (SHAMELESS PLUG for COILER) coiler amw 172 06GN2 7.7 bought from Gustav at silverstar, that is my main ride as it goes fast and it let me carve up some nice linked trenches right from the start. i have read this thread from start to finish and was quite glad to hear that Bruce uses some good old fashioned, lets do it and "GIT ER DONE" attitude. As for the rest? it gave me interesting reading but i'm quite happy to just ride and sometimes even hang out in the parks and push my envelope. thanks to all the engineers who dream this stuff up and apply it to real world problems cuz I hated math even tho i was in an engineering program at college. So i will continue to benefit from all your thinking. thanks again.

greg

[jonbass]

I've just read this entire thread and realized there is a reason why I'm a music teacher and can only count to 4 and know the first 7 letters of the alphabet. ;)

I don't think I realized that there was so much to sidecuts and board flex.

It seems like some of these new board are tapered (narrower tail-correct me if I'm wrong). Are these tapered because the radius opens up and gets bigger at the tail or is the radius difference through the sidecut fairly slight?

Does this make it easier to get out of a turn?

[lowrider]

Wrong question or observation could bring out the wrath of Bola. I'm still smarting from my insistance last march that the fun of boarding should trump the science:1luvu:

[TheTruth]

I still believe the sidecut shape has very little to do with how (why?) the 'new school' snowboard works.

The largest why and how is addition of the metal layers and the taper between the nose and tail. There can be a lot of discussion of what is the "best" way to shape the side cut between the taper, but the fact that modern race boards have a significant difference between the nose width and tail width as opposed to "old school" race boards where the nose and tail width was the same (or almost the same) is what gives them their different feel.

[yyzcanuck]

The largest why and how is addition of the metal layers and the taper between the nose and tail...

Sorry, but I disagree with you. The Titanal™ and taper are significant contributors to the design but... I think the LARGEST contributor to the feel (and measureable performance) comes from how the nose and tail roll up when the centre camber is bent during a turn, thus moving the main edge contact areas towards the centre of the board.

[Jack M]

the nose and tail roll up when the centre camber is bent during a turn, thus moving the main edge contact areas towards the centre of the board.

Am I reading this right? Are you suggesting that the effective edge (the length of edge contacting the snow, contributing to grip and carve) is less on a modern board? I don't think that is the case at all. The edge is buried in the snow right up to the "corner" of the nose. Check out BlueB's sig, and this picture of bschurman on his Coiler NSR (a modern board):

The reason the decambered nose works so well is that now the gradual upturn of the nose blends better with the sidecut when the whole board is decambered in the turn. It works with the sidecut, where a traditional nose fights the sidecut. The difference is slice versus plow. Ultimately, the sidecut is now being designed in 3D. Sidecut, camber, and nose upturn were formerly considered 3 separate things. Therefore they were designed separately, without concern for how each one affects the other two. Now the sidecut, camber, and nose are considered one continuous shape. Kessler finally realized a lot more of the nose counts as "effective edge" than was previously thought. So I really don't think that a decambered nose results in less effective edge, actually I think it results in more.

[TheTruth]

Sorry, but I disagree with you. The Titanal™ and taper are significant contributors to the design but... I think the LARGEST contributor to the feel (and measureable performance) comes from how the nose and tail roll up when the centre camber is bent during a turn, thus moving the main edge contact areas towards the centre of the board.

Well, we can agree to disagree. Here's where I'm coming from: What Kessler did was to adapt what was being done with World Cup race skis to the snowboard race world. If you follow race ski design, they went through a similar progression. GS skis became more "shaped" starting in the mid 1990's, by the late 1990's/ early 2000's they were very shaped, often resulting in skis with similar nose and tail widths. For various reasons, this design was found to be unacceptable at the speeds GS racers run at. The FIS started to demand increasing turn radius for the racer's safety. However, the racers loved the way the most highly "shaped" skis would quickly engage a turn. The ski companies found a way to please both the racers (who wanted quick turn initiation) and the FIS (who wanted longer turn radius for safety at speed) by keeping the ski wide at the nose, but incorporating huge taper down to a narrow tail. What's the turn radius of a modern GS ski? It depends where you want to measure it. Just behind the nose, it can be as low as 14-16 meters, from the waist back to the tail it can run 40-50 meters.

The interesting thing is the construction of true GS skis has changed very little from the "straight" ski era. GS skis contained metal layers, and always has less camber than the all composite slalom skis (metal in slalom skis is a recent design). True GS race skis always flexed softer than slalom skis, and the tip and tail would always "roll up" (as you put it) into an arc faster/easier when on edge than traditional slalom skis. However, "straight" GS skis, the overly "shaped" GS skis, and the most recent GS skis all feel vastly different in use even though the have very similar construction. The single biggest change I see is the difference in taper between the various eras.

[yyzcanuck]

Am I reading this right? Are you suggesting that the effective edge (the length of edge contacting the snow, contributing to grip and carve) is less on a modern board?

That's what I'm saying. Put a new board on edge, the centre convex camber collapse and becomes concave, raising the nose and tail off the snow surface.

This is because the concave nose & tail cambers make their transition to the convex centre camber at a point closer to the centre of the board than where the main sidecut radius ends.

I don't have a drawing to work from but I do have the boards. Put them on a flat surface and inclinate. Push the edge onto the flat surface and watch what happens to the nose.

What's important here is the heavily loaded contact patch (of the edge) is no longer at the extremes of the sidecut radius... it's now moved back to the areas where the nose & tail roll up off the snow. It's also a longer contact area now, not concentrated.

[Jack M]

That's what I'm saying. Put a new board on edge, the centre convex camber collapse and becomes concave, raising the nose and tail off the snow surface.

I completely disagree, look at the picture above. The snow is flying off the board way up at the corner of the nose.

I don't have a drawing to work from but I do have the boards. Put them on a flat surface and inclinate. Push the edge onto the flat surface and watch what happens to the nose.

Yeah, but that's not a meaningful or relevant demonstration. It neglects the fact that the board digs down into the snow, often by several centimeters.

[yyzcanuck]

I completely disagree, look at the picture above. The snow is flying off the board way up at the corner of the nose.

Yeah, but that's not a meaningful or relevant demonstration. It neglects the fact that the board digs down into the snow, often by several centimeters.

In defence of both of those points is this... imagine how much worse it would be if the nose (and tail) were not 'decambered' by design. The conventional board has it's highly stressed, heavily loaded edge areas concentrated at the point where the sidecut radius meets the upturn.

With the 'new school' design, that concentrated area of loading is no longer there. It's being rolled up because the SCR ends at a point that is beyond the point where the nose turns up.

Put your new board base down on the floor and use your method of determining the running length (paper slid under nose & tail).

Now stack a pile of books between the inserts so that it is pushed flat onto the floor at that point.

What happens? The nose and tail roll upward (and reduce the running length).

Why? The centre camber (convex) of the board transitions into the nose & tail camber (concave) at a point that is closer to the centre of the board than the end of the SCR.

Now imagine being able to push the centre of the board even deeper into the floor. The convex centre camber now becomes concave. This new concave centre camber must pivot about some point on the base. That point is the transition to the already concave nose camber.

What happens? The nose continues to roll upward even more.

Why? The pivot point is the transitional area of two different radius cambers.

THIS is the essence of 'new school'.

[Jack M]

In defence of both of those points is this... imagine how much worse it would be if the nose (and tail) were not 'decambered' by design. The conventional board has it's highly stressed, heavily loaded edge areas concentrated at the point where the sidecut radius meets the upturn.

With the 'new school' design, that concentrated area of loading is no longer there. It's being rolled up because the SCR ends at a point that is beyond the point where the nose turns up.

I think we agree here - I believe you're talking about an old style nose plowing and the new style slicing.

Put your new board base down on the floor and use your method of determining the running length (paper slid under nose & tail).

Now stack a pile of books between the inserts so that it is pushed flat onto the floor at that point.

What happens? The nose and tail roll upward (and reduce the running length).

Why? The centre camber (convex) of the board transitions into the nose & tail camber (concave) at a point that is closer to the centre of the board than the end of the SCR.

I agree that happens on a hard floor, but I don't think it is representative of what happens while carving. The paper test is no longer relevant, and perhaps it never even was anyway. In practical use the board penetrates down into the snow, and the edge is carving from widest point to widest point. Therefore I believe "effective edge" should be measured from widest point to widest point. It's certainly what's happening in the photo above.

[yyzcanuck]

OK, maybe we need to start with a new, formalized nomenclature for the various elements of snowboard design.

Let me offer up another bit of anecdotal evidence. The nose shape of 'new school' boards has been changed drastically from conventional. Why? I think it's because you no longer rely on the conventional nose rise to save you from augering in. Now, the nose is rolled up and will facilitate a much smaller, more abrupt shape (hammerhead).

These pics, like the one you posted of Ben, are just moments in time but... look at the nose of the board. It looks like it's barely touching the snow.

.

.

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[Jack M]

Man what do they put in the non-exported Molson up there?? ;) ;) ;)

A 185cm board with a 150cm effective edge wouldn't be a very effective race tool, methinks.

F2 and Donek list specs for effective edge that are longer than they would be on a old-school board. For example, F2's 183 is listed as 173cm effective.

I strongly believe effective edge should be measured as widest point to widest point now:

Putting my board on the ground and pressing the waist down to the floor, a piece of paper would slide down almost to the K:

<img src="http://www.jmphotocraft.com/Kessler.JPG" height=400>

If what I think you're saying was true, the sidecut wouldn't need to continue much beyond there. But it does, because very often the whole board is carving from widest point to widest point.

[yyzcanuck]

Man what do they put in the non-exported Molson up there?? ;) ;) ;)

Try not to take it to a personal level... Leave that to Parabola.

OK, I agree, sort of... the static effective edge can and should be measured from widest point to widest point as you state. But as you pointed out earlier, that's not a meaningful or relevant demonstration in this case.

The board is a dynamic system. The static effective edge is now put under varying loads during cornering (and to a lesser degree while running flat). This dynamic loading moves the heavily loaded contact area (what nomenclature shall we use for this? HLCA?) along the running length. The greater the loading (decambering?), the more the HLCA moves towards the centre of the board. To me, the distance from the HLCA at nose & tail is the effective edge now. Let's call this the dynamic effective edge?

[WinterGold]

Basically you are not contradicting each other that much. The important thing is that the boards somehow adapt to various conditions and that is the special thing!

If you ride the board flat or only slightly inclined (drifting), the effective edge is shorter than on traditional boards (which is good!).

When starting to carve the effective edge length changes and becomes much longer (which is good for carving!).

Depending on the constitution of the surface, the board will cut more or less into the snow and the contact area will change accordingly.

The important thing is how much the edge (nose) digs into the snow. And that is an art! No too much and not too less. Therefore in ski racing they use different flexes (and maybe also shapes?) for different snow conditions. I don´t think that snowboarders go that far at the moment ...

[Jack M]

Try not to take it to a personal level... Leave that to Parabola.

hey just kidding man. were three winks not enough? :D

OK, I agree, sort of... the static effective edge can and should be measured from widest point to widest point as you state.

cool.

But as you pointed out earlier, that's not a meaningful or relevant demonstration in this case.

I think it's relevant to describe the maximum length of the edge that might be carving at any moment.

The board is a dynamic system. The static effective edge is now put under varying loads during cornering (and to a lesser degree while running flat). This dynamic loading moves the heavily loaded contact area (what nomenclature shall we use for this? HLCA?) along the running length. The greater the loading (decambering?), the more the HLCA moves towards the centre of the board. To me, the distance from the HLCA at nose & tail is the effective edge now. Let's call this the dynamic effective edge?

ehhh.... I really don't think the effective edge gets any shorter as the carve gets deeper/harder/sharper/whatever. As long as your weight is anywhere close to the center, the whole edge should be in the snow, contributing to edge hold and turn shape. Of course sometimes that's not the case:

[yyzcanuck]

Let's pick this up again tomorrow... you have me thinking now.

Yeah, the measured effective edge must be longer (by design, compared to a conventional board) but I'm certain that the HLCA is moving toward the board centre as the load is increased. This to me makes the board 'feel' like it's shorter (shorter effective edge?).

I know the nose of the board is rolling up as the centre camber is made concave (rather than convex as it is when unloaded).

Thinking... thinking... my brain is about to explode!

[WinterGold]

I guess you are right, yyzcanuck, but the pressure on the nose and the tail must still be high enough to guarantee a good edge engagement. Otherwise it wouldn´t make much sense ...

[yyzcanuck]

I'm also trying to figure out why the board wants to turn so easily... why it naturally wants to turn when you begin to inclinate the board. I think this is also directly tied to the nose rolling up and into the direction of the turn.

This contradicts my thought on how the effective edge is shortening.

Hence... brain ready to explode!

[inkaholic]

I'm also trying to figure out why the board wants to turn so easily... why it naturally wants to turn when you begin to inclinate the board. I think this is also directly tied to the nose rolling up and into the direction of the turn.

These boards typically have a softer nose than old school shapes, combine that with the tighter nose scr and you have a board that will turn it quicker once put on edge.

Ink

[BlueB]

Dave, think more 3d...

Yes, the nose gently rolls up away from the snow when board is flat. But then, you have the side cut that goes all the way into the nose and tightens at the same time. So, as you put the board on the edge that extended s/c wants to go closer to the snow then the upward profile curve would suggest. Higher on the edge, the closer to the nose the contact point would be. Now, the beauty is in the fact that you are not forcing the nose into the arc by having to bend it, as it is already there, So, when the board hits softer snow or irregularities, it doesnt bounce you around or dig in, but rather goes with the flow, or it releases and re-engages automatically. Also, with the old abrupt curvature noses, when they dag in, they wanted to carve the own arc, like 1m or less, which is not the case with gentle curve of the modern nose. I always noticed this effect in smoothness of the ride of my old Priors, Generics and even Burtons, that have smoother and longer nose profiles, then, say, old Doneks, Protons, Higlender, etc.

[Jack M]

Let's pick this up again tomorrow... you have me thinking now.

Yeah, the measured effective edge must be longer (by design, compared to a conventional board) but I'm certain that the HLCA is moving toward the board centre as the load is increased. This to me makes the board 'feel' like it's shorter (shorter effective edge?).

I'm not even sure there is a HLCA at all anymore. To me it feels like the nose is simply slicing through the snow rather than plowing.

I know the nose of the board is rolling up as the centre camber is made concave (rather than convex as it is when unloaded).

It is, but don't think about it in terms of the board flat on your kitchen floor. Think about it angled up to about 60 degrees, carving in the snow. The shape of the sidecut, the whole decambered board, and the nose all fall in line. And then it is almost as if the nose doesn't even have an upturn.

I guess you are right, yyzcanuck, but the pressure on the nose and the tail must still be high enough to guarantee a good edge engagement. Otherwise it wouldn´t make much sense ...

agreed.

I'm also trying to figure out why the board wants to turn so easily... why it naturally wants to turn when you begin to inclinate the board. I think this is also directly tied to the nose rolling up and into the direction of the turn.

In addition to what ink said, I think taper has something to do with this too. Let's say the "taper angle" of the board is 5 degrees (WAG). Now imagine you're riding flat on your base, straight down the fall line. As soon as you tilt the board up on edge, it is instantly pointing 5 degrees away from the fall line.