20m SCR

[Mattias112]

you checked it out Mike T. The math is not quite straight forward and some very elegant treatment comes into play for the nth degree clothoid when you evaluate the Fresnel integrals.

The only problem with theory is that most people forget how to combine the theory with reality. For example, the board will not bend equally in different conditions. So the elegant treatment will work in some conditions but not so good in some.

And the flexcurve along the board will change the boards behavior almost as much. In the beginning of this thread there was this discussion on sidecut radius and actual turning radius. So do they have a magical formula for this also?

I do know that are almost as much theory as there are board manufacturer:o

And most boards actually work really good at least in some conditions:biggthump

[Jack M]

I will say that after riding the NSR185, which is a blended radii if not an actual clothoid, that I did feel what Bola was talking about with regards to the reduced g-loads. I haven't quite gotten my head around it, because mv/r² is mv/r², but it just felt so easy and it could help explain why I was able to hold an edge on such lousy conditions at high speed.

[Corey]

Let me crawl out once again and say the following, at least you are learning something and trying to learn it real fast.

What's the weather like up there? :lol: Seriously, could you get any more condescending?

On this intellectual realm, you are obviously clueless good ol'buddy, so STFU.

Come on, that's just too far. You're doing exactly what you've previously accused other people of doing, discounting their opinion and calling them out.

Been challenged recently on stress and failure by a clueless poster. I like being challenged on the intellectual plane but it is not funny when clueless poster want to pose a challenge, that crap should be reserved for the park where baggy pants and posers rule.

I was the 'clueless poster' in that first example. I certainly didn't challenge you, I asked pointed questions that you dodged and/or didn't answer.

http://www.bomberonline.com/vbulletin/showthread.php?p=225468&highlight=6061-T6#post225468

Take this back to the intellectual plane you mention above so that others can benefit from your vast knowledge. Good science doesn't depend on someone calling out everyone else, it stands up to close scrutiny and even calm discussions on the internet. Even scrutiny by 'clueless posters'. This was a pretty good discussion until the pissing match started.

I for one am curious if the differences between a clothoid curve and a simple segmented (13m front, 15m rear section) sidecut are within the manufacturing tolerances of the average board maker.

[lowrider]

If every snowboard ever built was based on sound engineering and a complete text of all relevant math formulas i"m sure Bruce and others of his unique skill wouldn't have time to test and ride the boards being built today.I've never seen his shop but i have a wonderful impression in my mind what his and others shops look like and if they are like a sterile operating room with walls covered in math formulas i don't think i could enjoy riding any board thinking i have condemned the man to that fate! Correct me if I'm wrong but my impression is he takes an idea builds it improves on it enjoys it and moves on.If the act of snowboarding is only a series of math formulas repeated by each change of direction then I'd say find a new sport. Corey dyck is right someone is breathing some funny air. I've always though that the pursuit of a new idea was worthy of the scrutiny of some but the respect of all. It's not about the math it's about the fun !

[lowrider]

the air is -12 c looks like we might get another week of riding before last run I'f bruce v would like to answer the question of the air in his shop does it tend to be thicker with sawdust or chalk from the blackboards covered in math homework ? looking forward to all the scientists taking over the lead in snowboard design. Is a single radii board now as passe as double camber?

[BlueB]

Sheeeshkebab! This tread seriously went astray!

Let's try to steer it back on track again...

I think what a lot of people mean to say is that their favorite freecarve board would not be something that a racer would use in a PGS or PSL FIS race, such as my 170/21/14, or the good ol' Donek 171fc (171/19.5/11.2)

Bingo, exactelly what I was trying to say.

As for the spiral section (common terms for clothoid, no?) sidecut, yes it works. I can tell from Virus and Kessler. While it is totaly fun and usefull to be able to change turn shape without horsing the board too much, it also messes with my brain a bit... When I do less then a perfect turn (yes, I do these too ;) sometimes) the board would do something unpredicted, like turn super tight or just release. With the radial sidecut, the turn shape is very predictable, but you pay by less versatility... I was totaly sold on the Vampire, then Prior Metal convinced me there's life after Virus too. Different ride but still great.

[Jack M]

On this intellectual realm, you are obviously clueless good ol'buddy, so STFU.

Come on, that's just too far. You're doing exactly what you've previously accused other people of doing, discounting their opinion and calling them out.

erm, yes, I kinda missed that. Let's play nice, mmkay?

[Corey]

Internet debating about things you have no expertise about is just silly. Looks like my beef so far has been related to mathematics or something closely related to it.

There are a bunch of people that would love to learn more, but you've got some secrets that you won't reveal. I'd love to hear some reasoning of how/why a clothoid curve works on a snowboard sidecut, but without the name-calling and extremely defensive posture. I for one don't understand how the rate of change of acceleration in a vehicle driving on a clothoid curve has anything to do with a snowboard that has a clothoid curve for a sidecut. The clothoid-shaped road presents a simple 2-D problem that relates to human sensitivity to sudden changes in acceleration, the clothoid sidecut on a snowboard is a 3-D problem with some pretty funky inputs with two highly variable discrete point loads (our feet), changing edge angle, a decambering board, and dynamically deforming snow underfoot.

I am out of this thread.

I'm noticing this is a trend. You state something, when people question it at all, you call them idiots and leave the thread. It really leaves anyone questioning and the readers wondering if you really know something about this or are just an internet thug. Sorry, I hate to call you out as you obviously are quite intelligent but you're making claims that don't mesh with simple 2nd or 3rd year mechanical engineering principles.

Lets drop all the internet tough guy stuff and have a real discussion about how the physical design of snowboards affects our riding and enjoyment of the sport. I'd love to learn more!

[yyzcanuck]

El DiaBola... step up and educate the un-educated. I'm all ears 'my friend'. BUT... don't expect me to not challenge your teachings until I am fully schooled. The other choice is for you to name call and run away.

Let me crawl out once again and say the following, at least you are learning something and trying to learn it real fast.

Anyone with skin thinner than mine might think you're a dickhead... I take some solace knowing that I can be educated and quite quickly. Teach me Doctor Bola.

[yyzcanuck]

No thanks... I've pretty much quit drinking since the 'incident' and I don't have a phone anymore.

There was no baiting, it was a sincere request to have you share your closely held knowledge and help educate.

I'm sure everyone misses you at NRC and Ecole Polytechnique. I'll be at Ecole Polytechnique next month... I'll ask around for some of your old friends.

.

[Corey]

There was no baiting, it was a sincere request to have you share your closely held knowledge and help educate.

100% agreed here too, no baiting.

I understand you are busy Bola, all I ask is that you spend as much time sharing your knowledge as you do calling others simpletons and stating your own credentials and past experiences. I spend a good portion of my days at work explaining technical issues to non-technical people, please do the same for us at BOL.

I'd love to hear your rebuttal to this one question/observation I made above:

I for one don't understand how the rate of change of acceleration in a vehicle driving on a clothoid curve has anything to do with a snowboard that has a clothoid curve for a sidecut.

Please, answer without calling anyone stupid or telling us how smart you are. Just write out some scientific reasoning how the two can be related and I'll be really happy. Maybe I'm completely misunderstanding what you're trying to say, just throw us a bone so that yyzcanuck and I can understand a link between the two.

[yyzcanuck]

... Just write out some scientific reasoning how the two can be related and I'll be really happy. Maybe I'm completely misunderstanding what you're trying to say, just throw us a bone so that yyzcanuck and I can understand a link between the two.

Thank you corey_dyck, perhaps I'll have you do my posting in the future so that I don't pollute my questions with horse****.

The answer to your question is held within the quote below. Time to sit down and crunch the numbers?

The velocity and acceleration properties of the clothoid is such that they minimize the exerted G force for a given speed or rate of change of speed. In short, you will be able to rail and change directions quickly while minimizing the crushing load. In lay terms, fatigue will be reduced while fun is maximized for the weekend warrior.

But my favourite is this...

But please stop spewing out loads of rubbish and when you are called out, you try to switch or play the victim.

If that isn't the "pot" calling the "kettle" black, I don't know what is!!

[Corey]

Sorry Bob, you couldn't afford my rates! :p

I'm looking for something more in-depth than that. ;) Here's my issue:

Originally Posted by bola

The velocity and acceleration properties of the clothoid is such that they minimize the exerted G force for a given speed or rate of change of speed. In short, you will be able to rail and change directions quickly while minimizing the crushing load. In lay terms, fatigue will be reduced while fun is maximized for the weekend warrior.

100% agreed for a vehicle driving on a clothoid curve. The passengers will experience a gentler change in acceleration than a straight merging directly into a simple radius.

How does that relate to a clothoid curve that travels with you on your snowboard? You can change which part of the curve you travel on with weight shifts, unlike the above example where the vehicle's change in trajectory is strictly defined by where it is along the curve.

If we're talking about minimizing change in G-force in a carve with a board with a large radius at the tail and a small radius in the nose (regardless of what curve it is), you'd start the carve on the tail to keep the radius large and then shift the weight progressively to the nose to tighten things up mid-turn. Then back to the tail again to release G-force slowly and progressively. I don't think anyone actually does this!

A rider can control the crush load with any sidecut profile, they just change the inclination of the board relative to the snow. Too many G's? Get the board flatter. Too few? Tilt it up further.

Bruce, if it's not a trade secret, could you chime in with what method you use to blend from one radius to another on your boards? Few would say that your boards are horse****.

[lowrider]

If i were Bruce Varsava i'd save his info for his masters thesis i think if he can illicit this much debate on this forum a room full of engineering profs.would wet themselves with what he had to tell them! Crank out those boards and keep them guessing .

[Bruce Varsava]

Bruce, if it's not a trade secret, could you chime in with what method you use to blend from one radius to another on your boards? Few would say that your boards are horse****.

Take a long piece of wire from something like a mig welder, draw a bunch of different radii and cut them out as accurate as you can. Then take a few of those radial sidecut templates and lay them over each other to get the desired result. Use a router to copy that to the new template and blend in the sections with a bit of block sanding.

Trade secret is secret no more:biggthump

VOILA!

I know this next info is not really valid as we tested actual boards with actual riders of various skills so the results by no means are meaningful:lol:

Had 11 boards to test last weekend and the conditions were a bit of granular over real hard with dark mega hard patches, surface softened up during the day. No real surprises and each type of board worked for different riders. The higher sidecut race models were not too loved by many, edge hold was good but the acceleration needed good control to harness so they were not too popular. Had a tighter turning soft multi sidecut board and most liked that if they had solid carving ability. If the rider needed to slide it a lot, they found it too demanding as it was quite grippy. Of course a flex pattern change could have helped with that but then a bit of grip would surely be given up. . Radial boards gave up a bit of grip but offered a nice predictable turn and many said they felt most natural on those models. My favorites on the day were the multi sidecuts as they had great grip but that is a bit of a skewed view as they were quite soft and it was a day you really could not push the board hard due to the loose surface and the hard ice. Just showed me I need a real soft board for those types of days. Still totally enjoyed the Classic and Stubby and others did too as they were out the most.

Just a great day of testing with a handful of riders of all abilities which really is what testing is all about.

BV

[lowrider]

Thank you Bruce for clearing the air on your methodology i'm relieved that you don't spend all your time on solving complex formulas at the dusty chalk board but spread the fun around by having others involved in true on hill engineering.:D

[Mattias112]

Hi, it seems that there are some different explanations on a clothoid on a snowboard. So please, if some know which is true please inform me:confused:

Does a clothoid shaped board have shortradius nose and tail ond longer in the middle, (like a elliptic board)?

Or does it have a longer radius nose and tail with tighter in the middle?

Or thight in thos nose and then progressively longer? Or the opposit??

Thanks:)

My personal thoght would be that to decrease the forces it would need to have a long radius at nose and tail and thighter in the middle. But if not so I would appriciate an explanation on how the practical theory of this.

Thanks!

[Bruce Varsava]

Hi, it seems that there are some different explanations on a clothoid on a snowboard. So please, if some know which is true please inform me:confused:

Does a clothoid shaped board have shortradius nose and tail ond longer in the middle, (like a elliptic board)?

Or does it have a longer radius nose and tail with tighter in the middle?

Or thight in thos nose and then progressively longer? Or the opposit??

Thanks:)

My personal thoght would be that to decrease the forces it would need to have a long radius at nose and tail and thighter in the middle. But if not so I would appriciate an explanation on how the practical theory of this.

Thanks!

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

To tell you the truth I still do not really understand all the variables but if you get a board to bend and turn from the nose it is a much more aggressive way then getting it to bend in the mid section. The flex has to work in unison with the sidecut . On radial sidecuts, boards that have more mid flex tend to be more relaxed at turn initiation. Soften up the nose and they are much more aggressive at the start of a turn. The multi sidecuts can affect this as you could imagine. Tighter sidecut in nose = more aggressive bending and initiation.

When you look at a picture of someone in a hard carve, most of the time the mid of the board is radically bent. Hard carving you can also feel the mid of the board overbending and creating a wider line in the snow to scrub speed. As a designer I can adjust the amount this happens through the flex and sidecut. Some boards you want this to happen to slow things down and other boards for racing you do not.

Freecarve boards have more of this and raceboards have the least. Modern raceboards are very stiff and have straighter underfoot for this reason to keep the flex to a minimum and keep your body weight from bending too far into the snow and slowing you down.

Obviously there are so many variables it is tough to just put it into math so from my perspective its best just to look at the trends of whats going on and adjust stuff from there.BV

[Corey]

worked this out yet? Don't forget that you can throttle steer a vehicle and I am sure Bruce knows about this first hand. Didn't we all learn to prove or disprove an hypothesis? PROOF! I think we are too old to be spoon fed.:rolleyes:

You're dodging the question - AGAIN. :) And what does throttle-steering a car have to do with clothoid sidecuts? Never mind, I assume that's yet another tactic to dodge the original question.

Please do spoon feed us 'children'. I've clearly laid out my hypothesis for why I feel that there is no relation between a vehicle driving on a clothoid-shaped road and a clothoid that travels with us on our snowboards. Now it's your turn to present something other than what boils down to "trust me, I'm smarter than you ever could be." This is the peer-review process that's common in science:

1. You state something as fact.

2. People review your work and ask questions.

3. You answer their questions with explanations that explain away their concerns.

Step 3 is missing. Usually when step 3 is missing it means the 'fact' in 1 is incorrect or the person offering it really doesn't understand what they're talking about.

Let me make myself painfully clear: It's not that I don't believe that some makers are using clothoids or other advanced geometrical shapes. I just disagree with your reasoning as to why a clothoid curve is the 'best' way to have a variable sidecut. I also assume that you are smart Bola, but I really can't understand why you are being so evasive about something you claim to know so much about.

We all await your next reply, hoping it won't be yet another pedantic pat on the head or a listing of your credentials.

Bola, are you going to SAE congress in Detroit? It's a longshot but it seems you have very diverse interests. I'll be there Wednesday through Friday, I'd love to meet up in the evening to discuss this and all things snowboarding with a fellow enthusiast.

[BlueB]

Hi, it seems that there are some different explanations on a clothoid on a snowboard. So please, if some know which is true please inform me:confused:

Does a clothoid shaped board have shortradius nose and tail ond longer in the middle, (like a elliptic board)?

Or does it have a longer radius nose and tail with tighter in the middle?

Or thight in thos nose and then progressively longer? Or the opposit??

My personal thoght would be that to decrease the forces it would need to have a long radius at nose and tail and thighter in the middle. But if not so I would appriciate an explanation on how the practical theory of this.

Just by eyeballing the Virus Vampire, it seems to have tighter radius in the middle, straighter on the tail and forward part and then tightest at the very nose...

[NateW]

You're dodging the question - AGAIN. :) And what does throttle-steering a car have to do with clothoid sidecuts? Never mind, I assume that's yet another tactic to dodge the original question.

Please do spoon feed us 'children'. I've clearly laid out my hypothesis for why I feel that there is no relation between a vehicle driving on a clothoid-shaped road and a clothoid that travels with us on our snowboards. Now it's your turn to present something other than what boils down to "trust me, I'm smarter than you ever could be." This is the peer-review process that's common in science:

1. You state something as fact.

2. People review your work and ask questions.

3. You answer their questions with explanations that explain away their concerns.

Step 3 is missing. Usually when step 3 is missing it means the 'fact' in 1 is incorrect or the person offering it really doesn't understand what they're talking about.

Let me make myself painfully clear: It's not that I don't believe that some makers are using clothoids or other advanced geometrical shapes. I just disagree with your reasoning as to why a clothoid curve is the 'best' way to have a variable sidecut. I also assume that you are smart Bola, but I really can't understand why you are being so evasive about something you claim to know so much about.

We all await your next reply, hoping it won't be yet another pedantic pat on the head or a listing of your credentials.

Just wanted to say that I completely agree with Corey here.

It makes no sense to me why a variable SCR would be a good thing. Enough people are enamored with it that I am keeping an open mind, but I sure would like to understand it.

At any given moment in time, all of me and my board is turning at a single rate. Why is it better to have part of the board trying to turn at a great rate and part of the board trying to turn at a lesser rate? Doesn't that mean that part of the board is going to be carving and part of the board is going to be skidding? Why is that better?

I "get" the theory behind decambered noses, and now I'm looking forward to trying one. But variable SCR still seems completely bizarre to me.

Again, I realize that there are people who like it who probably have good reasons for liking it. I don't deny that. I just want to understand the geometry and the physics behind it.

[lowrider]

WE failed engineers love to taunt the geeks and engineers it reveals a lot of a persons inner demons.With the recent debates raging isn't it too bad the season is comming to a close here in north america,while Bruce V is squeaking in a few more R&D runs this last weekend in Ontario I look forward to what is in store for next season .I hope he does't run out of mig wire before he can show off his next great creation.:D

[Gunnar]

Just wanted to say that I completely agree with Corey here.

It makes no sense to me why a variable SCR would be a good thing. Enough people are enamored with it that I am keeping an open mind, but I sure would like to understand it.

At any given moment in time, all of me and my board is turning at a single rate. Why is it better to have part of the board trying to turn at a great rate and part of the board trying to turn at a lesser rate? Doesn't that mean that part of the board is going to be carving and part of the board is going to be skidding? Why is that better?

I "get" the theory behind decambered noses, and now I'm looking forward to trying one. But variable SCR still seems completely bizarre to me.

Again, I realize that there are people who like it who probably have good reasons for liking it. I don't deny that. I just want to understand the geometry and the physics behind it.

Could it be so that the tighter sidecut in nose and tail, makes up for decreased edge pressure due to torsional flex?

[Mattias112]

J

At any given moment in time, all of me and my board is turning at a single rate. Why is it better to have part of the board trying to turn at a great rate and part of the board trying to turn at a lesser rate? Doesn't that mean that part of the board is going to be carving and part of the board is going to be skidding? Why is that better?

Well actually this is only true on a hard surface, like ice. On snow the middle of the board will sink a little deeper and thus create a multirate radius... The only thing is, when I calculate this radius it actually should be longer radius in the nose and a thighter in the middle! And then the same from the middle and to the tail( If the board is ridden with a central weight distribution). This is particulary true if the board is leaned over more than 45 degrees. And in those turns the clothoid or elliptic, which both has a longer radius in the middle (what is the difference??) will work against the board and the board will not have as good egdegrip as a single or slight progressive radius. This is not just math. It is exactly what I experiece with for example the boards from Virus.

But I must admit that a clothiod or elliptical sidecut is fun and reactive in normal carving conditions. It is only when you tilt the board more than 45 degrees that you actually can feel a slight decrease in edgegrip. I do ride rather agressivly but whit a very centralized stance so another person with an different riding style, might disagree with this.;)

I know some of you do have other opinions and I look forward to read them.

[NateW]

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?