20m SCR

[BlueB]

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.

This can bee seen even by looking from the cahir at your tracks from the previous run - there is a drastic direction change on the transition.

Also, I dare to say, it makes your stance angles feel flatter, as it is not the angle to the centerline of the board anymore, but rather angle to the tanget of the edge at the binding!

[KingCrimson]

I tried to have Bruce explain this to me a while back but it's apparent that he's sick of the taper subject.

Now it makes sense why Bruce says (and I noticed beforehand) a tapered board will turn abruptly at first and then open up.

This is why the speed between crossunders and taking up the run seems disproportionate to me. Obviously using a small lane is faster, but the margin is small considering how much time is spent across and up the fall line.

In pointing down the fall line, there is an abrupt turn out of the fall line, and then a larger radius "traverse" (traverse used loosely as it's still very downhill) afterwards. In changing to the downhill edge (as opposed to more or less following the fall line), the board very quickly pulls into the fall line and sticks there doing a large radius turn. This seems to be extremely valuable for racing; hook around a gate and straightline to the next.

Thanks everyone!

T

[Ladia]

What kind of special plate has that second racer on his board? :confused:It looks like 2 x 8 with a lot of duct tape. What such modification will do to the characteristic of the board?

[jp1]

Ah, ha. Racers (all kinds) and their Duct Tape, gotta love it :) Hopefully Fin & CNC will rectify this issue

[yyzcanuck]

Jack, et al...

I like this 'peer review' format... it makes a person think. Thanks for all the feedback.

Let me try to summarize this again...

1. I don't believe the type of curve (elipse, radius, clothoid parabola) is the important part of the new board designs. One curve may be better than another but by my own admission, I can't tell which type is under my feet.

2. I think the most important part of the new board design is the concave nose & tail camber ends (starts?) within the sidecut shape of the board. Some are calling this a decambered nose.

3. I believe this is the most important design element because it results in a movement of the high edge pressure zone from a concentrated area near the nose & tail, to broader areas closer to the centre of the board.

4. I see this happening because in meaningless tests on a flat surface, I can see the nose roll upward when the centre camber is made flat rather than convex.

5. This roll up of the nose benefits the overall ride by:

(a) see item 3 above

(b) edge areas close to the nose have pressure reduced and the nose is sometimes even lifted off the snow

© provides a smoother more controlled entry into the turn

© provides a means for the nose of the board to actually be moved towards the turn direction as the centre camber is made more concave

(d) allows for a much shorter nose on the board resulting in the possibility of a much longer static effective edge (measured from widest point to widest point)

I think all of these things, combined with Titanal™ construction, huge (2+cm) taper and multiple SCR blending (or some other shape) result in a reduced sliding resistance, easier turn entry, less likelihood of augering in the nose, truer tracking and overall, a less tiring ride.

All of these aspects may not be what every rider wants. Some may still want the SCR to tighten at the tail, some may still want plenty of pop in the tail (not Fin, he's getting plenty of that), some may want to continue with glass construction, some may want minimal taper. That's fine by me. To each his own.

This thread started with a question about 20 metre sidecut radius and has variously transgressed to name calling, finger pointing and ultimately peer review. I still stand by my original assertion that K©lothoid shapes are not what makes the new boards behave the way they do. Comparing the use of the clothoid shape in civil engineering and snowboarding is pure horse****. It's the decambered nose and the upward motion created by the mechanics of this design that makes this new design what it is.

AND... while I'm on my soapbox : I will again say it's best not to compare the SCR numbers of the new board designs with more traditional designs (or for that matter, the curves of a rollercoaster!). Better to be used only for comparing new boards with new boards (SG vs F2 vs Kessler vs COILER vs VIRUS). BUT... you can't ignore them. The SCR (of a manufacturer's board lineup) is important for comparison purposes.

[Jack M]

1. I don't believe the type of curve (elipse, radius, clothoid parabola) is the important part of the new board designs. One curve may be better than another but by my own admission, I can't tell which type is under my feet.

I am inclined to agree, but at the same time obviously Kessler etc are using a clothoid for some reason. However I suspect that its performance can be effectively equaled by blended radii, which is part of what I want to find out in my review.

2. I think the most important part of the new board design is the concave nose & tail camber ends (starts?) within the sidecut shape of the board. Some are calling this a decambered nose.

Agreed. However for racing and high speed GS style freecarving, I'd say the increasing radius sidecuts are very important too. Less hook to the turn finish is a good thing at high speeds.

3. I believe this is the most important design element because it results in a movement of the high edge pressure zone from a concentrated area near the nose & tail, to broader areas closer to the centre of the board.

I think perhaps it eliminates it (your "HLCA") altogether. I think the pressure may be evenly distributed along the whole length.

Also, the decambered nose provides a significant amount of mechanical suspension. The nose simply carves over or through bumps that would upset a traditional nose.

[yyzcanuck]

I am inclined to agree, but at the same time obviously Kessler etc are using a clothoid for some reason.

Well, I don't think I've ever said the clothoid was better or worse than any other shape. I think I've only been trying to say the important thing isn't the shape but how the shape is used in the board design.

I think perhaps it eliminates it (your "HLCA") altogether. I think the pressure may be evenly distributed along the whole length.

I'm not sure it can be evenly distributed along the entire length. I think there must be some areas (2) that are more heavily pressured because of the way the centre camber is being deformed (from convex to concave). To prove or disprove this may be nearly impossible without some sort of stress/strain gauges actually put onto a sliding board's edge. Good luck with that.

[Jack M]

Well, I don't think I've ever said the clothoid was better or worse than any other shape. I think I've only been trying to say the important thing isn't the shape but how the shape is used in the board design.

I'll say it's less dramatic and less important, but I wouldn't say it's not important at all. Splitting hairs here.

I'm not sure it can be evenly distributed along the entire length. I think there must be some areas (2) that are more heavily pressured because of the way the centre camber is being deformed (from convex to concave). To prove or disprove this may be nearly impossible without some sort of stress/strain gauges actually put onto a sliding board's edge. Good luck with that.

Yeah, you're right about that. I agree it is now more spread out and further back from the nose.

[yyzcanuck]

I'd say the increasing radius sidecuts are very important too.

The radius is tighter in tip and tail and straighter in mid section.

I don't think all the new board designs use increasing sidecut radii from tip towards tail. Mr. Coiler stated earlier in the thread that the tip and tail radii were tighter than the centre and Kessler seems to have a similar design in place (~13m, ~20m ~15m).

Sorry, Jack, I've edited this... I meant as noted above in bold.

[lonbordin]

To prove or disprove this may be nearly impossible without some sort of stress/strain gauges actually put onto a sliding board's edge. Good luck with that.

Actually embedding stress/strain gauges is something that could be done in production using thin film types. I'm thinking the value of this data could outweigh the cost of the single production board. You'd just need an interested board designer.

Me, I'd just like to see and A to D converter plugged into a snowboard.

[yyzcanuck]

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.

Also, I dare to say, it makes your stance angles feel flatter, as it is not the angle to the centerline of the board anymore, but rather angle to the tanget of the edge at the binding!

I'm not sure how we'd accurately calculate the taper angle but using simple trig and 173 (effective edge?) as the 'opposite' side, 1 as the 'adjacent' side (2cm taper/2) it would give about 1/3 degree. Doesn't seem significant but maybe it is. It's an interesting thought.

[pokkis]

Agreed. However for racing and high speed GS style freecarving, I'd say the increasing radius sidecuts are very important too. Less hook to the turn finish is a good thing at high speeds.

I feel that this new shapes are special great at lower speed at small bunny hills due one does not loose speed on turns as much as on traditional shapes, speedy tail will give momentum going. That is good thing when you are forced to ride smaller hills

[Jack M]

I don't think the new board designs use increasing sidecut radii from tip towards tail. Mr. Coiler stated earlier in the thread that the tip and tail radii were tighter than the centre and Kessler seems to have a similar design in place (13m, 20m 15m).

Is that what they're doing on the PGS boards? I know that's what Bruce is doing with the VSR, but I thought the NSR and PGS boards were strictly increasing radius....? Prior, Donek, and F2 list their PGS boards as having 2 radii, with a longer one in back.

[eajracing]

i'm late to the party on this thread but have immensely enjoyed reading it....

i second the opinion (not fact... gotta be careful here) that for all the decambering/sidecutting etc its the combination of them that makes a great board great. I have spent numerous hours modeling this in the past and as Bruce continues to point out - all my models came with assumptions - and its the R&D approach that really ekes out the best rides. look at aero for f1 cars.... you can CFD til the cows ome home but until you run it, and get feedback you can interpret (jackie stewarts "its a little speeedboaty through 4 comes to mind) all you've got is a great computer model.

I was fortunate enough to ride a 'new school' board last year (coiler, titanal, multiple-increasing from tip to tail sidecut) and couldn't get over how awesome it was. I look forwards to taking possession of my very own VSR in the VERY near future (ahem - bruce - squeak squeak squeak) to better understand the minutiae of the effects discussed.

I think its fantastic that there's this many people that feel this strongly about board design involved in our sport and it will help create better designs for us, and hopefully more of us, in the future. On that note - hypotheses are just that - expect them to live dangerously, and furthermore, expect to defend your own.

Engineers are a unique bunch and they feel very strongly about their work, which is a good thing. The day we stop trying to one up each other is the day i give back my stamp and ring to the PEO.

If Bola is ever up in TO... I would love to moderate the discussion with YYZ... and although it might not be over beers, Dave does have some deadly roti shops i've visited in his neck of the woods... perhaps we could sort it out over some goat curry and doubles? there's always ginger beer.

at risk of sounding like jack's terminal intermediate... theres such a small group discussing these designs, it would be shame to break it up over petulant name calling.... show love to one another- we're all brothers like the bee gees....

[Hotbeans]

The WCR which stands for World Cup Race is the favorite of most carvers that I know.

Yup. The ability of this board to lock down a series of salolom turns or ANY type of turn radius has my full, loving attention... great for meat gates or wide-open play time!

[bobdea]

what's so special about a clothoid as long as you come close with a shape?

what I'm saying is that even if a sidecut is not a very specific formula but close to it, blended sidecuts for example. once worked out it seems that the differences would be so slight that it may not make a noticeable difference. I'm assuming this based on how slight the differences in the shapes can become. at some point using "clothoid" or another term will probably be meaningless because if something works really well everyone else will be doing it eventually unless something better comes along. even if it's not based on a actual true clothoid curve you'd still be able to get very very close. again, I assume.

[lonbordin]

what's so special <snip> again, I assume.

You know slope and surface have little in the way of variance so one must be precise about one's sidecut.

[terekhov]

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.

my eureka moment on understanding this phenomenon is while reading http://www.ronlemaster.com/presentations/RidingFromTheSnowUpVail02192002.pdf some years ago - before kessler yes. ski inside snow cup (page 9) was my bingo. the tip shovel make all the difference, and power platform (between bindings on board) do the hard work

[ajcannon]

interesting discussion about side-cut radius..clothoid...etc.

I have never raced but own two WCR's (one with 13m radius, the other with 10m radius).

Those boards are so much fun for "free-carving"...the 13m is crazy high-speed fun agressive fun.

[yyzcanuck]

A patent abstract is a short technical summary of an invention that includes a statement of the use of the invention. It is primarily used for searching purposes and describes the essence of the patent in layman terms.

So, in this intellectual realm, I'm obviously clueless but... I believe the abstract is saying the most important part of the patent is the 'load-dependent shifting of the edge pressure'.

We can all go ahead and read the patent application and the description of how all shapes can and may be used to perform this load-dependent shifting but I certainly haven't seen anything that states the most important aspect of the patent is the k©lothoid shape.

There are plenty of side benefits to this load-dependent shifting (as noted in some of the previous posts) but I'll be damned if I can find where the most important part of the design is the k©lothoid shape.

Maybe someone with a higher education can read and interpret the patent and show me the limitations of my comprehension? Anyone?

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[colintkemp]

yyz,

The application contains an extensive discussion of variable radii (see discussion regarding figures 12-22). (If you are not used to reading patent applications, it could be pretty dense stuff.) There is also a specific reference to clothoid radii instead of traditional arcs at [0010]. According to Kessler's application (note: it is not a patent but a patent application) one of the benefits of the claimed invention over the prior art is that the edge pressure location is improved - it is more towards the "saddle" of the mid-tip and tail areas and less toward the extremes (see figure 7, and related discussion).

Especially after riding my 180 KST (w/ hangl) this past weekend at Sugar Bowl, I generally grock this particular benefit of the newer designs. While it took me a couple runs to get used to "lifting" the board (I'm used to narrower waists), once I had it "up" on edge it tracked very smoothly and well. I had a sense there was greater edge contact.

***

Without starting another new vs. old technology war, my 180 KST could really be a quiver killer (but for powder days maybe - don't know). I know I have posted that I will never leave home without my Donek 185 FC - which is still true - but it may not make it out of the car once in the mountains - it did not on Saturday. Now, whether I am man enough to handle day after day of riding the Kessler - which is quite heavy - is a different question...

Aside: at Sugar Bowl I saw a woman on a yellow FP and briefly rode with a guy (Alam, I think) on a Pogo. That is more than I often see in a season there. Good stuff.

Happy Holidays,

[yyzcanuck]

Yeah, I'm reading it and note there is discussion regarding the various shapes but I have yet to see anything that claims the clothoid shape is 'the' thing that 'makes' the Kessler KST.

I still believe it's the nose roll-up that is the design feature that produces the defining element of KST.

That may change upon further reading and learning but for now... I'm sticking with the abstract statement.

[colintkemp]

yyz,

I lost track of the thread - did not know "clothoid is THE difference" was the issue. I don't think you will find that in the application. To your point, the upturn is an element of independent claim 1, upon which all other claims (directly or indirectly) depend. Thereafter, some claims contain elements related to variable radii, but claim 1 does not. Again, the figure 7 discussion goes to your point as well. You are on to something, and my experience on my Kessler supports it. The upturn is pretty fundamental.

Notably, before reading the application I had not really focused on thinking of the radii of the sliding surface (i.e., "RS" in Kessler's application). But clearly there is a lot of interplay between the two radii at issue (RS (sliding surface) and RG (lateral edge)) (or, camber and side cute) resulting in board performance.

Interesting stuff. Thanks for circulating the application.

Colin

[tufty]

yyz,

I lost track of the thread - did not know "clothoid is THE difference" was the issue. I don't think you will find that in the application.

Nope, you won't find that in the slightest. As I (skim) read it, pretty much all the application covers is the "decambered tip", or interplay between sidecut radius and board camber. Sure, there's a passing mention of clothoids, but that's all. Indeed, if clothoids are at all important to Kessler, it would be stupid of them to put them into the same application as one which deals with decambered tips.

The passing (and only) reference to that "killer app", the clothoid is, in reference to board geometry, "... it is also possible to use other elements, such as ellipses, clothoids, parabolas, etc ..."

Interesting stuff. Thanks for circulating the application.

Yep, it's an excellent read.

[www.oldsnowboards.com]

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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Nice shot!