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sidecut question?


jtslalom
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If you lay your board on its side on a flat ground, you will have a gap between your board and the ground at the midpoint of your boards length. Given the points at which the sides of your board come in contact with the ground, about how far from these contact points towards the middle of your board does the sidecut radius end. I think this is a question better suited for the engineering department of a snowboard company but I would like to hear other peoples replies.

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You can tell where your sidecut ends by placing the board flat on the ground, decambered. Slide a piece of paper under the nose and tail until it stops. This commonly happens a few centimeters in from the widest points of the board.

The reason for this is that technically the widest points of the nose/tail do not lie on the mathematical curve of the sidecut. This is due to the fact that the outward curve of the sidecut needs to be married to the inward curve of the nose. You can't just stop the sidecut curve and instantly start the nose curve. There would be a point formed at the intersection.

Since the widest points of the board are not mathematically part of the sidecut equation, board makers usually start the upturn of the nose at the end of the sidecut. They <i>could</i> turn the nose up at the widest points of the board, but I don't know what that would do to the ride.

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Originally posted by AlpentalRider

I wouldn't use a file to detune, a gummi stone does the trick and you won't have to worry when your hand slips while doing it.

Funny you should mention that...the index finger of my right hand is significantly larger than my left for this reason...lots and lots of scar tissue/callous from preping/tuning boards over a decade ago. Detuning the nose/tail IMHO is best done with a stone as you can control the angle freehand a lot easier than with a file

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I've often wondered about this myself. As a couple other people have said, the widest parts of the board are usually a few centimeters up the nose or tail. I've heard a bunch of explanations but so far they've all been more touchy-feely than math-physicsy so I still wonder.

I'm about to take delivery of a board whose widest points are right where the camber and tip/tail curves meet. I'll report my findings as soon as I get some snow time with it.

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Originally posted by Jack Michaud

Since the widest points of the board are not mathematically part of the sidecut equation, board makers usually start the upturn of the nose at the end of the sidecut. They <i>could</i> turn the nose up at the widest points of the board, but I don't know what that would do to the ride.

Where the sidecut ends in relation to where the tip of the board turns up can have a large affect on it's performance in a turn. If the sidecut ends right where the tip begins to bend, you get a bit more drag in a carved turn. The board can feel almost as if it is trying to burrow under the snow. By bringing the sidecut into the bend a little bit, the board tends to plane over the top of the snow better when in a carve. This design can also assist in initiating a turn.

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A picture is worth a thousand words!

Here is a sketch of your theoretical snowboard that stops getting wider right at the end of the sidecut radius:

ks4fd

Now, if we zoom in to the widest point:

ksoow

Notice the kink in the edge? That would be hard to make! So, there is a slight area where the edge starts curving inwards while the width is still increasing.

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Originally posted by Donek

Where the sidecut ends in relation to where the tip of the board turns up can have a large affect on it's performance in a turn. If the sidecut ends right where the tip begins to bend, you get a bit more drag in a carved turn. The board can feel almost as if it is trying to burrow under the snow. By bringing the sidecut into the bend a little bit, the board tends to plane over the top of the snow better when in a carve. This design can also assist in initiating a turn.

Wow this explains a whole side of things I have understood at a feel level but never actually thought about...We had some boards that slipped in the mold (1-2cm at most) creating each of those characteristics, I always prefered the board with the bigger/taller nose though I never knew the why of it. Thanks Sean I have learned something new today:)

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Originally posted by Jack Michaud

I thought my explanation above was fairly mathy, did you see it?

Yeah, but you left out the important part. :) What would it do to the ride?

My intuition says that having the sidecut go up the nose a bit probably helps pull the nose of the board inward during a carve, especially in soft snow where the board digs a trench. The alternative would allow the wrong-way-curved part of the nose to try to cut straight ahead, or "burrow," as Sean put it.

But on ice, where the trench depth is very small, what happens then? Is there an edge angle at which a non-linear section of edge is scraping along? Maybe that's why some people like to detune? Inquiring minds want to know.

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Corey - I don't think that diagram illustrates the question jtslalom asked. If you draw a board with a nice blend of sidecut and nose curves, there's a widest point. The funny thing is, if you set that board down on a flat surface with no weight on it, that widest point is NOT where the edge meets the surface.

At the widest point, the edge is slightly above the surface. The contact point is a few centimeters behind the widest point. And the question is, why?

I mentioned a while back that I met a guy in my area who is making boards. He has a mold set up so the widest point IS the contact point. He says it works fine and if I don't like the results he'll make another. So I says hell yeah let's try this.

The board he's making is quite similar to the Coiler I got from Bruce a couple years ago, just a bit narrower, and width a bit less nose and tail, so I'm going to do some A/B comparisons.

There's no such thing as a failed experiment - only new data. :)

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Guest boogieman

jtslalom

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BoogieMan,

Knowing the approximate point at which the sidecut ends makes it possible for me to tell the (almost exact) sidecut radius based on a parabolic, hyperbolic, or circular sidecut. All based on conic sections.

Wich allows you to do what?

actually i dont care what sidecut radius my board has as long as i like the ride

and if it was to know what radius the board has to make sure that if you buy a new one its sidecut radius will be bigger or smaller depending on what you want i would just write down the serial number and email the guy who made them i think thats a little easyer then trying to measure it yourself.

but thats just me,

maybe you like making complicated calculations

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You bet Boogieman,

I am a high school geometry teacher. I am teaching my Honors Geometry class about circles and how they relate to conic sections and snowboarding. The STUDENTS will be making complicated calculations based on the curvature of a snowboard based on circular side cuts. I will also relate this problem to pre-calculus students based on parabolic and hyperbolic curves. All of which are based on conic sections. In order to get a realistic problem I have to get all the details straight. So I posed the question because I wasn't exactly sure. The answer I recieved confirms where I had thought the curve ends. A few cm back based on individual manufacturers and where they think the nose and tail curve will start. The point of inflection may very between manufaturers.

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Originally posted by NateW

...and it be showin like a mothafxxxa:

http://www.natew.com/frame_main.cgi/software/snow/html.Main

Thank you Nate, I've trying to figure out the side cut radius on my Flite for two years now I I could not remember the formula...now I know my 163 has 144cm of effective edge and a 9.6 m sidecut...that that it matters much any more since my Coiler arrived today (thank you Bobby Buggs :D )

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