hi i'm sean martin president and founder of donek snowboards in this video I'm going to explain how the different side cut shapes that we produce can affect your riding in order to ensure that everyone watching is on the same page I'm going to start with some basic concepts and then progress through some demonstrations intended to provide background information necessary to the discussions finally I'll show you how the different side cut shapes that we offer can affect the shape and dynamics of the turn produced by a snowboard almost anybody who's purchased a snowboard has taken a look down the side of the board like this bent it like that now there's a good reason for that some of you may or may not know what it is but that reason is because these two things define very very key features in the snowboard the combination of curvature on the side of the board and the degree to which it bends define the ease or lack of ease with which you can carve a turn let me demonstrate okay so if you're standing on your board you're flattening it out bending it a little bit and when we make a turn we tip the board up on edge now if we tip it a little bit we can see a curvature created with the contact point between the edge and the snow or the surface we're riding on and as long as we use the correct technique the board is going to travel right along that the path generated by the edge so the steeper we angle the board you can see the curvature keeps getting tighter and tighter so we get more and more curvature and therefore we carve a tighter turn so the more we angle that board the more force we put on that board the tighter the turn that the board creates okay I've moved outside because I want to be able to demonstrate some basic physics principles and I don't have enough room in the studio so what we're going to look at is the forces that the snowboarder sees well he's always riding right we're going to do that I've got a simple little contraption here it's just a frame that holds my GoPro camera and then what we've got is a weight here suspended by a rubber band so what you're going to see is that rubber band stretching and coming up you can see my little device going around in circles here and you'll be able to see in the side frame sort of what's happening now what I do to begin with so I'm going to speed things up and go even faster you going to see that that rubber band really stretches alright so now what I'm going to do is slow things down a little bit not too much and what's going to happen is I'm going to tighten my radius by pulling on my string with that slowing down the speed alright so let's do that again so if I maintain the same speed but shorten the radius that I'm turning in you're going to see that that rubber band stretches a little bit more and we see a greater centrifugal force both these things are key your speed the faster you go the greater the centrifugal force you see the tighter the radius you go the greater the significant force to experience now let's look at a couple other things the primary cause that the last demonstration is we're snowboarding we're not on a horizontal plate we're actually on an incline plane so we're going to look at next is what happens to the forces as we traverse through our turn on an inclined plane let's see if I can get this going and you can see that I'm running on an inclined plane here and what you're going to see here is that the forces are greater at the bottom of that turn and at the top of the toe this is a really really key element to what happens in a snowboard let me go good okay I'm back here in the studio and I've got my little pretend snowboarding slope set up that we can draw and look at some of the things we've learned and see what the results are the first thing I want to talk about though is how most manufacturers describe the sidecut of their board you'll find that most of the time if you look at the specs of a snowboard you're going to find that they list a radius for this curve now if you don't know what that means it's essentially just this curve is a section of a circle and pop up a little graphic but if you were to continue this curve indefinitely it would actually come back and hit the other end of the snowboard and be a circular shape but being said let's return to what we've what we've been observing and have a look at what's happening through a turn one of the most important things we've observed is that as our speed increases what we're going through a turn the centrifugal force or the force we're applying to the snowboard increases as well so faster speed means greater centrifugal force the other thing that's important is a smaller turn or a tighter turning radius means greater centrifugal force the other thing we've observed is at the top of our turn this is our turn at the top we have a relatively small centrifugal force and at the bottom we have a relatively large centrifugal force and in between well it's going to be a little bit bigger it's actually building ok this is because of a number of factors if you recall we said greater speed means a greater centrifugal force well up here we're going relatively slowly but we've come down a hill here and our speed has increased and increased and increased therefore our centrifugal force down at the bottom is increasing what else is happening well we showed earlier that when you tilt the board at a steeper angle the board bends more and our turn gets tighter well because our centrifugal force or our force being applied to the board has increased we have to lean into the turn more which means we're tipping the board more on angle which means what we're tightening the radius so our turn is getting a smaller radius down the bottom than it was up top a very big radius okay because we've tipped the board further over on edge our forces have combined and helped us make an even tighter turn there's one other factor here that explains what's going on we've got the force of gravity pulling us down the hill up here at the top of the turn the force of gravity is fighting or detracting from centrifugal force so our centrifugal force is small over here in the middle of our turn it's not a having an effect other than to pull us down the down the slope and make us go faster down here at the bottom in addition to this increased speed increased angle reduced turning radius we've also got the force of gravity pushing on the board as well making us bend it even more so all of these factors combine to result in a low force a medium force and a very large force on the board which means a very large turning radius up here a medium turning radius down here and a very tight turning radius down here so we can fairly easily represent what that turn shape actually looks like it's big at the top tighter tighter tighter tighter tighter theta getting very very small towards the bottom so this is what happens when we use a circular radius on the side of the board because nothing is changing with respect to the shape of the board and all of these forces are getting bigger and bigger towards the bottom now a lot of free covers really like this term shape they like it because what happens is as they go through the turn as they progress the board is bending a little and more and more and more until they get to the end of the turn where the board has bent a huge amount and then boom they release all that energy and use the board like a springboard to launch them through the air into the next turn so if that's the type of turn you like to make well then a single radius side cut is really possibly what you want we can do similar things with some of the other side cut shapes but it will generate this type of turn shape and that type of building of energy towards the end of the turn and then the ability to release all that energy and cause the board to slingshot you into the air and then you can start your next turn well the next question becomes what happens if this isn't right for me well if you look at a racer this isn't right at all in fact a racer wants a turn shaped completely opposite from what we just saw they want a turn that's tight at the top and longer and longer at the bottom why because if there's a gate let's say right here they want to make a rapid direction change at the top of that turn and accelerate to the turn or to the next gate that's down here somewhere so a rapid direction change and an acceleration is what they want to create well question becomes how can we create something like that with a different side cut shape or through board engineering well we have to look at one other factor that's occurring in your turn and that is where's your weight as the turn progresses so if you look at a typical snowboarder when they start their turn up at the top the forces that are going to generate the centripetal force needed to generate a carve turn aren't there they've got to create them themselves so what they do is they tend to lunge into the front of the board or distribute or displace their center of mass towards the front of the board so that instead of bending the entire board now they're bending just a portion of it and by doing so they can initiate a turn and begin that carve turn as their turn progresses weight typically slowly through the term shifts towards the tail of the board so what we can do is vary the radius of this side cut from the tip of the board to the tail now we do that very simply with the same technique I just drew drew that curve it's what we call a continuously variable side cut radius and it gives a very smooth continuously variable side cut radius and the ability to very smoothly and effectively adjust your turn shape depending upon where your weight is on the board there are a few companies using variable side cut radius as these days it's frequently refer to as VSR and what they'll do is they'll use a combination of radii so it might start with it might start with one radius here and then progress to a second radius towards the tail of the board you can see that there's a marked change or a very visible change in the shape of the curve there so what can be done is you can use more than one one radius so you might go to three so you've got your first radius and then a transitional radius and then your big radius on the other end so that's smooth things out a little bit what we do it donek is we use something we refer to as a continuously variable side cut radius and that involves a radius that changes continuously down the length of the side cut so you've got a very even transition from one radius to the other over the entire length giving it a tremendous amount of variability in your turn shape you

A physics lesson about Snowboard turn shape: Part 1
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18 thoughts on “A physics lesson about Snowboard turn shape: Part 1

  • June 3, 2019 at 11:05 am
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    great video! thanks

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  • June 3, 2019 at 11:05 am
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    Holy shit, this is beautiful.

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  • June 3, 2019 at 11:05 am
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    Sean- Watching this again. Love the product…thank you for the R&D which makes this Donek I ride amazing. I bought another board a couple months ago in anticipation for this season, it will remain in the closet. The new Donek absolutely RIPS.

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  • June 3, 2019 at 11:05 am
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    Hey, that's very interesting, thanks:)

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  • June 3, 2019 at 11:05 am
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    This is great. Very autistic. Autism > snowboarding.

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  • June 3, 2019 at 11:05 am
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    Same as ski teaching, hard to explain the transition from speed control turns to just lean with speed makes balance by using centrifugal force.

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  • June 3, 2019 at 11:05 am
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    centrifUUUUUUUUgal

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  • June 3, 2019 at 11:05 am
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    ….and your company name is now planted in my head…….job done.

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  • June 3, 2019 at 11:05 am
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    It is good to see a manufacturer explaining the physics of their board shapes. I thought previously it was just a basic curve radius but didnt know why it mattered so much. I've learned yet another golden nugget of information about board tech, thanks man..

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  • June 3, 2019 at 11:05 am
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    I love that he made a note for "engineers/physicists" about his use of centrifugal force, because he knew we'd all be going "centrifugal force is not a force, blablabla" at the video 😛

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  • June 3, 2019 at 11:05 am
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    This explains a lot. Whenever I carve a tighter or perfect turn, I am able to pop up so freely because of force hidden in the board. In contrast, when doing skidded turn, I can't spring up at all. It requires too much energy from my legs.

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  • June 3, 2019 at 11:05 am
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    So, understanding the side cut and how it relates to turning makes me wonder… How is it possible to go straight? I know I don't tilt my board up so it's perpendicular with the ground. And It does seem that I ride a and angle where the back sidecut points down the mountain and he front sidecut slips

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  • June 3, 2019 at 11:05 am
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    This is awesome. Some of my favorite subjects combined, and now I understand more about what's happening!

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  • June 3, 2019 at 11:05 am
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    No free body diagram????

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  • June 3, 2019 at 11:05 am
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    @supertrooperdude69 um… this is NOT a snowboarding lesson, this is a physics lesson. So of course an instructor should not be teaching this to his students.

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  • June 3, 2019 at 11:05 am
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    Thank you for this video.

    Reply

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