Sidecut vs Effective edge

[abakker]

which one is more important in determining the actual carve circle that a board can make?

[BlueB]

Effecctive edge has to do with grip and stability, but nothing with carved radius.

Carved radius is determined by side cut, and then flex vs. your ability to bring board high on the edge and decamber it. Firmness of the surface also plays a rolle.

For strictly scientific purposes we should imagine a board with circular sidecut, totaly hard surface (blue ice), and flex suited for your weight/abillity, as well as your ability to incline the board to any angle... In that case, a board of a given sidecut will carve only one specific radus at a given angle of inclination.

Boris

[lonerider]

which one is more important in determining the actual carve circle that a board can make?

Sidecut is the only thing that is important aside from that fact that if you don't have enough edge grip (from effective edge) you might slip out of the circle at high speeds.

[Phil]

Sidecut AND running length determine turn radius. A board with a 160cm running length and a 10m radius is going to turn tighter than a board with a 140 cm running length and a 10m radius.

[tex1230]

if you're gonna go like that, Phil, then you have to include speed, rider weight, board flex, and technique...

I can make a 12m board turn like a 9m board given the proper set of circumstances...

[Jrobb]

Sidecut AND running length determine turn radius. A board with a 160cm running length and a 10m radius is going to turn tighter than a board with a 140 cm running length and a 10m radius.

So a good slalom board would have a 200cm running length and 10m sidecut?

J

[BlueB]

Sidecut AND running length determine turn radius. A board with a 160cm running length and a 10m radius is going to turn tighter than a board with a 140 cm running length and a 10m radius.

I have to disagree with this. It would be just hookier.

Deceiving factor is that on anything other than ice, skilled rider will be able to push the centre of the longer board deaper in the snow, thus decamber more and tighten the radius.

If anything close to scientific approach is to be considered, only one parameter should be changed at the time. So, same imaginnary rider, same flex, same inclination angle, same (firm) surface, same (radial) SCR and different lenght still equals the same turning radius. It's simple geometry...

[Phil]

Wow, I won't lie to you guys about the fact that I am frustrated with you calling me out like this.

If two boards of different lengths have the same sidecut radius, the longer board will have a greater sidecut DEPTH. BlueB touched on this a little, but made the false assumption that it is simple geometry when in fact it is not. At the same angle of tilt, the longer board with the greater sidecut depth (same sidecut radius) will decamber more, causing a tighter arc.

I have to disagree with this. It would be just hookier.

Deceiving factor is that on anything other than ice, skilled rider will be able to push the centre of the longer board deaper in the snow, thus decamber more and tighten the radius.

If anything close to scientific approach is to be considered, only one parameter should be changed at the time. So, same imaginnary rider, same flex, same inclination angle, same (firm) surface, same (radial) SCR and different lenght still equals the same turning radius. It's simple geometry...

So, if you will humor me, take out a piece of paper and make a circle by tracing something (I used a CD) or using a compass. Now cut out two different length "boards". Tilt the shorter "board" to your desired tilt angle and trace the arc on the paper. Now tilt the longer "board" to the same angle and trace the arc on the paper. Let me know the results.3

As far as your scientific approach, check out the book thatI referenced below.

So a good slalom board would have a 200cm running length and 10m sidecut?

J

Wow, that board would really turn tightly. Unfortunately, you would really have a hard time getting out of that turn. Imagine the tip/tail width on that board..! It would be so unwieldy.

if you're gonna go like that, Phil, then you have to include speed, rider weight, board flex, and technique....

You cannot throw out other board characteristics, but they are not as important in determining possible turn radius which was the O.P.'s question.

I can make a 12m board turn like a 9m board given the proper set of circumstances...

Are they the same length? If they are, then the same tilt will produce a different turn. If the 12m board is longer than the 9m board, you are only proving my point.

For example. Here are the specs for F2's GS boards:

<TABLE cellSpacing=0 cellPadding=4 width="98%" align=center border=1><TBODY><TR><TD class=board_specs>Board Length

</TD><TD class=board_specs_length align=middle>168

</TD><TD class=board_specs_length align=middle>173

</TD><TD class=board_specs_length align=middle>177

</TD><TD class=board_specs_length align=middle>183

</TD></TR><TR><TD class=board_specs align=left>Effective Edge (CM)

</TD><TD class=board_features align=middle>151.5

</TD><TD align=middle>156.5

</TD><TD class=board_features align=middle>160.5

</TD><TD align=middle>166.5

</TD></TR><TR><TD class=board_specs align=left>Side Cut Radius (M)

</TD><TD class=board_features align=middle>13

</TD><TD align=middle>14

</TD><TD class=board_features align=middle>15

</TD><TD align=middle>16

</TD></TR><TR><TD class=board_specs align=left>Nose Width (CM)

</TD><TD class=board_features align=middle>22.6

</TD><TD align=middle>23.3

</TD><TD class=board_features align=middle>23.4

</TD><TD align=middle>23.9

</TD></TR><TR><TD class=board_specs align=left>Center Width (CM)

</TD><TD class=board_features align=middle>18.6

</TD><TD align=middle>19

</TD><TD class=board_features align=middle>19.2

</TD><TD align=middle>19.6

</TD></TR><TR><TD class=board_specs align=left>Tail Width (CM)

</TD><TD class=board_features align=middle>22.6

</TD><TD align=middle>23.3

</TD><TD class=board_features align=middle>23.4

</TD><TD align=middle>23.9

</TD></TR><TR><TD class=board_specs align=left>Construction

</TD><TD class=board_features align=middle>Sandwich

</TD><TD align=middle>Sandwich

</TD><TD class=board_features align=middle>Sandwich

</TD><TD align=middle>Sandwich

</TD></TR></TBODY></TABLE>

Notice as the boards get longer, the sidecut is longer as well. These boards are all made for the same GS course, but if they had the same sidecut on the longer lengths as the shorter lengths, the longer boards would be "too hooky" as BlueB put it.

Unfortunately, all of my books are in storage because I am working on moving, so I cannot reference any of this stuff for you. It would be better if I could quote the experts, but alas, I cannot. I can only give you my dated paraphrase. I hope that it was enough.

If you don't want to take my word for it, do some investigation of your own, check out The Simple Geometry of Skiing I believe that this is where a lot of stuff comes from, but like I said, my books are in storage (in another city) so I cannot verify.

[lonerider]

LOL, I'm exiting this thread right now.

[Buell]

Very thought provoking post Phil.

Is it correct to think that the longer board, with the deeper sidecut, needs to be softer longitudinally than the shorter board with the shallower sidecut, for a given rider. This is so the rider can fully decamber the board into the snow and achieve the same angle of tilt as the shorter board.

When you say that the F2 GS boards (168 to 183) are designed for the same GS course, are you saying that each length of board is designed to make the same radius turn when matched with the rider it was designed for?

Would it follow that F2 could design each length of board to make the same radius turn for a given rider by adjusting the longitudinal flex only? I assume the turns would feel different, even if they are the same radius.

Thanks, Buell

[abakker]

thanks for the in depth answer. so, to take this a little away from the theoretical and back to the realm of me actually getting another snowboard.

i posted earlier looking for a short sidecut board.

take the f2 speedster SL linup.

the two lengths i am looking at are the 163 and the 166

they have sidcuts of 9.5 and 9.7 respectively.

now supposing that they are for the same course and have the same turning arc, the 166 will turn sharper because its added length will allow me to decamber it better(easier)?

[Buell]

I expect the 166 will be stiffer and therefore will make a bigger radius turn for a given rider in the same conditions.

[BlueB]

Phil, yes I can and I will call you out on this. I wouldn't challenge you on riding technique, but I am qulified to talk about geometry. And keeping all the other parameters fixed, it does come down to simple geometry.

Yes, I agree that longer of 2 boards of same side cut radius would have more side cut depth. I also agree that it would have to decamber more at the same angle of tilt, but just to be merly able to carve the SAME radius as the shorter board.

I can develop a 3d model/computer simulation of this, but there's no need -just go into NateW's calculator

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

and select the Reverse Engeneering option.

Keep all the parameters the same, type in a running length and side cut radius, let the thing calculate the carve radius. Then type a longer running length and the same sc radius as before and recalculate. Watch the carved radius remaining the same for any given running length and side cut depth and decamber changing all the time.

Here's also 2 screen shots to illustrate this little experiment:

[NateW]

FWIW, I did that calculator stuff because my intuition told me that edge length had to be a factor, and Jack Michaud was telling me otherwise, here on this forum, a long time ago. Turns out my intuition was wrong.

I tried two approaches at the geometry - first, using the "carve radius is a function of sidecut radius and edge angle" approach, and second using the "carve radius is a function of sidecut depth, edge length, and edge angle" approach. Given the same board specs and edge angle, you get the same carve radius no matter which way you do the math. Given a board with a 10m radius, you'll get the same carve radius for a given edge angle, no matter how long the edge is.

[Phil]

Is it correct to think that the longer board, with the deeper sidecut, needs to be softer longitudinally than the shorter board with the shallower sidecut, for a given rider. This is so the rider can fully decamber the board into the snow and achieve the same angle of tilt as the shorter board.

When you say that the F2 GS boards (168 to 183) are designed for the same GS course, are you saying that each length of board is designed to make the same radius turn when matched with the rider it was designed for?

Would it follow that F2 could design each length of board to make the same radius turn for a given rider by adjusting the longitudinal flex only? I assume the turns would feel different, even if they are the same radius.

Thanks, Buell

This is my line of thinking. However, I don't see how just adjusting the longitudinal flex would make the turns the same. There is still a sidecut depth that decambers at a certain angle.

take the f2 speedster SL linup.

the two lengths i am looking at are the 163 and the 166

they have sidcuts of 9.5 and 9.7 respectively.

now supposing that they are for the same course and have the same turning arc, the 166 will turn sharper because its added length will allow me to decamber it better(easier)?

The idea is that the longer board has a similar sidecut depth due to the longer SCR. The added effective edge makes it more stable IMO. I think that the longer board is also a little stiffer. This is my experience from owning both boards, not math.

Yes, I agree that longer of 2 boards of same side cut radius would have more side cut depth. I also agree that it would have to decamber more at the same angle of tilt, but just to be merly able to carve the SAME radius as the shorter board.

I love to learn, and if you can show me in a real world application where more decambering makes the same turn, I would even enjoy being proven wrong.

Did you do the paper test? Am I over simplifying? The paper test clearly shows a tighter arc given the same SCR on different lengths due to further decambering.

BTW, no, I am in NO WAY qualified to talk about math.

I understand that Nate's calculator is proving my theory wrong, but when I am seeing what is happening in front of me, it is hard to believe the math (maybe because I don't understand it anyway), so how do you explain that in a non-mathmatical way?

I am one that would need real world proof, not mathematical. Figure out how to disprove the paper test and I will be more inclined to believe it.

[Phil]

I am trying to work through this, but I am having trouble with the math.

I don't understand why, if there are different sidecut depths, that the tip/waist/tail measurements are the same on both boards?

In any case, I have to get going to the mountain. I look forward to discussing later.

[tex1230]

My head hurts. I'm going back to delta trading and rho hedges. this sh!t is too complicated.

[Mike T]

My head hurts. I'm going back to delta trading and rho hedges. this sh!t is too complicated.

:lol: :lol: :lol: :lol: :lol: :lol:

[Dr D]

Now add in the benefits of a line of boards with identical sidecut depth across the line. the antiprogressive caternary sidecut. Brian Perhaps you can explain the genius of the identity line better than I. I just know they hook up right now and let you go with ease. takes the work out of it. Oh yeah and the sidecut varies, for instance on my freecarve it starts at 9.5 and finishes at 12.5, so you can vary your turn radius by shifting your weight into a different part of the edge very cool. for the racers back in the pack you can reverse that and get a board that will hold a line through the ruts.

[Jrobb]

Phil, I think what your paper experiment is revealing is an octipal (optical sorry I like pronouncing it wrong) illusion. It's the same radius circle produced but one portion is longer than the other. The pic below is a CD tracing.

...both of same radius but the top one looks like a more gradual arc. The amount needed to decamber the longer (segment/board) is indeed much greater since the segment has to represent a larger length of the arc than the smaller segment, but it results in the same arc tilted to the same angle...at least within my observations using the paper test. The traced segment has to fit around more of the circle's circumference so it has to decamber more than the smaller one.

But I did notice one thing interesting. With NateW's calculator the numbers are not 100% accurate. Phil you're right the nose and tail should not and cannot be the same for a longer board with similar sidecut. The calculator is set up to not adjust the widths for other number inputs. It adjusts the sidecut, sidecut depth, sidecut radius on the fly and leaves alone the effective edge, waist, tip, and tail widths. One reason I can think of, is if you simply increase the sidecut how does the algorithym know both the tip and tail increase symmetrically? Currently it doesn't know that. Nor does it know to decrease the waist width alone to account for this (or increase tip and tail and decrease the waist all equally to get the desired sidecut shape). More programming needs to be done to allow for complete and minute control for that to be 100% correct. It does what it was designed to do well but can be misleading at first glance. All values need to change given one input. Hell you can even just add taper and there's no change to the tail width...or any other numbers for that matter...aside from sidecut setback. One thing that is concrete is the boards no matter what their design will always carve a smaller radius circle than the absolute value of the sidecut radius.

J

[bumpyride]

A = length of board

B = Sidecut radius

C = Sidecut depth

D = Ideal length

F = Board stiffness

E = Surface conditions (Rockwell scale of Hardness)

M = Speed of run

O = wieght and style of rider

A + F - B/C x sq root of B/C = DEMO 1

A guy could really go crazy trying to factor in all the variables, especially rider style when looking at the same boards. No doubt specs may give a pretty good indication of what to expect, but different boards work very differently for different riders.

If a person is going to outlay a bundle of cash for a board it would really pay to demo that manufacture's board and model line to see if they're compatible with your riding style. I bought a board or two that just didn't fit what I expected, especially on turning radius, and liveliness.

Remember the Bumblebee!

[Dr D]

A = length of board

B = Sidecut radius

C = Sidecut depth

D = Ideal length

F = Board stiffness

E = Surface conditions (Rockwell scale of Hardness)

M = Speed of run

O = wieght and style of rider

A + F - B/C x sq root of B/C = DEMO 1

A guy could really go crazy trying to factor in all the variables, especially rider style when looking at the same boards. No doubt specs may give a pretty good indication of what to expect, but different boards work very differently for different riders.

If a person is going to outlay a bundle of cash for a board it would really pay to demo that manufacture's board and model line to see if they're compatible with your riding style. I bought a board or two that just didn't fit what I expected, especially on turning radius, and liveliness.

Remember the Bumblebee!

great point ! even if all things were equal between riders size wise we all have different styles and different levels of flexibility ourselves so one mans sweet ride is not necessarily the next guys.

[BlueB]

Reverse Engineering Calculator doesn't reset the nose/waist/tip... We should have used the Forward Engineering, where these do not appear at all - they confuse the issue anyhow, all that's neede is sc radius, running length and angle of inclination to calculate the sc depth and carved radius.

I did the paper test and they all carve the same radius at the same inclination angle and longer board decambers more to achieve this (compensation for longer contact).

Attached is an illustration with 3 overalped boards. Print, cut out and try at any inclination - they'll aways be at the same arc...

[NateW]

But I did notice one thing interesting. With NateW's calculator the numbers are not 100% accurate. Phil you're right the nose and tail should not and cannot be the same for a longer board with similar sidecut. The calculator is set up to not adjust the widths for other number inputs. It adjusts the sidecut, sidecut depth, sidecut radius on the fly and leaves alone the effective edge, waist, tip, and tail widths. One reason I can think of, is if you simply increase the sidecut how does the algorithym know both the tip and tail increase symmetrically? Currently it doesn't know that.

Or what if you change the sidecut and you really want the tip and tail to be fixed, and only adjust the waist instead? It doesn't know that either, and maybe you hadn't thought of that possibility at first yourself, so you can see what I was up against...

To solve that class of problems completely would require WAY more time than I wanted to put into that project. I like the way you can tweak one variable and watch the others change quickly, and I didn't want to lose that for all scenarios just because some scenarios don't work right. Even coming up with a good UI to let the user specify constraints would be challenging - the simple solutions suck, and the good solutions are too complex to be usable. :)

For the most part, it updates the results based on the parameters you type in. If you change one parameter, it won't necessarily work backward to update the other parameters. But sometimes it will. I realize it can be confusing.

[Jrobb]

Or what if you change the sidecut and you really want the tip and tail to be fixed, and only adjust the waist instead? It doesn't know that either, and maybe you hadn't thought of that possibility at first yourself, so you can see what I was up against...

To solve that class of problems completely would require WAY more time than I wanted to put into that project. I like the way you can tweak one variable and watch the others change quickly, and I didn't want to lose that for all scenarios just because some scenarios don't work right. Even coming up with a good UI to let the user specify constraints would be challenging - the simple solutions suck, and the good solutions are too complex to be usable. :)

For the most part, it updates the results based on the parameters you type in. If you change one parameter, it won't necessarily work backward to update the other parameters. But sometimes it will. I realize it can be confusing.

...and you're right! I didn't list all the possible combos of entries. If all the calculations were to update accordingly, you'd have your own version of SnoCad. That part of my post should have read better. It was kind of a collection of thoughts over an hour or so here and there between "putting out fires" here at work and I couldn't get it to flow right. "numbers are not 100% accurate" was poor word choice. Apologies if it sounded otherwise.

J