SWriverstone Posted February 23, 2005 Report Share Posted February 23, 2005 I've been trying to fully understand sidecut in snowboards. To help myself (and possibly others) I sketched out a diagram (see below) that makes it a lot easier to grasp. (I've never seen another diagram like this.) Now I need some clarification on this diagram... If I'm using the terminology correctly (which I might not be), the blue "board" on the left has a smaller sidecut and therefore will turn a smaller circle. The red "board" on the right has a larger sidecut and therefore will turn a larger circle. Am I right so far? What I'm still wondering about is this: The radius of the side cut alone does not determine the waist width of the board, because you can place the circle at any depth into the board (e.g. closer to the center). Unless there is a standard for this? Related to this is where the sidecut begins at the toe and tail---in other words, if the circle is positioned closer to the center of the board, then the sidecut will begin nearer the toe and tail. So I guess what I'm still confused about is how the two relate to each other: the radius of the sidecut, and the position of the sidecut, which are two entirely different things as I see it. The final confusing point is that (depending on its position) a smaller sidecut would appear bigger, because it cuts more deeply into the board, right? So when the terms "larger" and "smaller" are used, they do not refer to the appearance of the sidecut, but strictly refer to the radius of the circle, right? :) Thanks in advance for clarifying this! Scott Quote Link to comment Share on other sites More sharing options...
Guest TrDi Posted February 23, 2005 Report Share Posted February 23, 2005 Hi! I'll just add a thought of my own: when riding, the board bends in turns and it seems to me that it creates another radius that depends on it's stiffness. If the board is stiffer, the board will bend less and therefore carve a larger circle and vice versa. The point I don't understand is the following (although this question might be better asked on extremecarving forum...): when extremecarving, the board is supposed to be perpendicular or near perpendicular to the snow. What point has sidecut radius at that point? The only radius that affects the curve is then the radius made by the board itself - its stiffness. Or am I wrong (I suppose as sidecut radius does seem to be important)? However, the I suppose sidecut radius is crucial all the time you don't ride on the edge angle 90°. But in reference to tighter or wider turns and circles - why sidecut? Shoot me if I'm wasting your time... :D Bye, TrDi Quote Link to comment Share on other sites More sharing options...
skywalker Posted February 23, 2005 Report Share Posted February 23, 2005 Hi Scott You're right about the bigger and smaller. It's not the way round you think about board width and scr. At a given board length and a given scr the board width is the result of both. (most of the time. There are some parameters like starting and end radius too, but I would like to neglect them now). It's not a given length, a given overall width, a given waist width and a given scr. this would result in areas withaout radius along the board. You're right again about your final confusion point: A smaller sidecut is deeper ;). This is: more sidecut depth at the same eff edge length means smaller scr. Hope I could give some more confusion Tom If I'm using the terminology correctly (which I might not be), the blue "board" on the left has a smaller sidecut and therefore will turn a smaller circle. The red "board" on the right has a larger sidecut and therefore will turn a larger circle. Am I right so far?What I'm still wondering about is this: The radius of the side cut alone does not determine the waist width of the board, because you can place the circle at any depth into the board (e.g. closer to the center). Unless there is a standard for this? Related to this is where the sidecut begins at the toe and tail---in other words, if the circle is positioned closer to the center of the board, then the sidecut will begin nearer the toe and tail. So I guess what I'm still confused about is how the two relate to each other: the radius of the sidecut, and the position of the sidecut, which are two entirely different things as I see it. The final confusing point is that (depending on its position) a smaller sidecut would appear bigger, because it cuts more deeply into the board, right? So when the terms "larger" and "smaller" are used, they do not refer to the appearance of the sidecut, but strictly refer to the radius of the circle, right? :) Thanks in advance for clarifying this! Scott [/b] Quote Link to comment Share on other sites More sharing options...
Jack M Posted February 23, 2005 Report Share Posted February 23, 2005 http://www.bomberonline.com//articles/physics.cfm Quote Link to comment Share on other sites More sharing options...
Fleaman Posted February 23, 2005 Report Share Posted February 23, 2005 when extremecarving, the board is supposed to be perpendicular or near perpendicular to the snow. What point has sidecut radius at that point? The only radius that affects the curve is then the radius made by the board itself - its stiffness. Or am I wrong (I suppose as sidecut radius does seem to be if you lay the board on its edge say perpendicular to the ground, only the tip and the tail are touching, when you pressure the board, the center goes away and makes another arc. Now if you put a flat board on edge and did the same thing, it would be really hard to push the center of the board away without pushing the rest of the board with it. I hope this makes sense. Quote Link to comment Share on other sites More sharing options...
Jack M Posted February 23, 2005 Report Share Posted February 23, 2005 Originally posted by skywalker At a given board length and a given scr the board width is the result of both. Not really, waist width is up to the designer. For example, Donek makes two 171s - both with an 11.2m sidecut, but one that is 18cm wide at the waist and one that is 19.5cm. I suppose if you wanted to fix the nose and tail width at some arbitrary number, then yes, length, nose/tail width, and sidecut radius would determine waist width. However most designers fix the waist width at some number, and let the length and sidecut radius determine nose/tail width. Burton seems to take a different approach - they seem to fix length, waist width, and sidecut <i>depth</i>, which results in a random sidecut radius number. Quote Link to comment Share on other sites More sharing options...
Neil Gendzwill Posted February 23, 2005 Report Share Posted February 23, 2005 Originally posted by SWriverstone The radius of the side cut alone does not determine the waist width of the board, because you can place the circle at any depth into the board (e.g. closer to the center). Unless there is a standard for this? The last points of contact of your circle determine the effective edge length of the board. Usually the designer will add a little radius going back the other way and then the shape moves into the nose or tail sections. So how far a given sidecut bites into the side of the board is a matter of how much edge the designer wants the board to have. Clearly a really long board won't work with a really short-radius sidecut as you would need a very wide nose/tail in order to have a usable waist. Related to this is where the sidecut begins at the toe and tail---in other words, if the circle is positioned closer to the center of the board, then the sidecut will begin nearer the toe and tail. Also a matter of design choice. A powder board with a long, gradual nose will have the centre of the sidecut back further than a slalom racer with an abrupt, short nose. Originally posted by TrDi when extremecarving, the board is supposed to be perpendicular or near perpendicular to the snow. What point has sidecut radius at that point? When the board is laid over, it flexes and the sidecut radius becomes effectively smaller. The given radius is the largest radius turn the board can make in a pure carve. In the extreme carving case, the point where they are totally laid out and the board is at a high angle is just the peak of the action. Before and after that point the board is at a more regular angle. At the peak, the tail and tip are dug strongly into the snow and the board is already strongly flexed so I don't think the board is behaving like it would on some theoretical flat surface - it's turning on a combination of edge and base pushing against the snow. Quote Link to comment Share on other sites More sharing options...
astrokel Posted February 23, 2005 Report Share Posted February 23, 2005 Just thinking about this a bit (geometries, physics, and all that school stuff), it seems to me that the sidecut is a major determinant of how QUICK a board can be thrown into a turn. The determinants of the real turning radius is sidecut and flex (and to a certain extent size of rider and speed). If sidecut is small (8-9m) and the board very stiff then you have to be going really fast or be really heavy in order to maintain the turning radius but the sidecut would enable you to enter the turn quickly. If the sidecut is large (13-14m) and all other issues were equal the ability to enter the turn would be slower and more gradual but once into the turn the radius would be MORE determined but how the rider can bend the board (the sidecut WOULD be continually contributing to the trench but it seems more of the base of the board would be more on the snow in the trench depending of course on the snow conditions). I really don't think that this idea that the sidecut of the board is the largest turn the board can make in a pure carve actually holds water in the real world (how much can a board "carve" when it's flat?). A really stiff board with a small sidecut could make a bigger carved turn than a floppy board with a huge sidecut. Here's the bike analogies again. Think shape of tire with radials, tire circumferance, and width as variables... both could make the same size turns just how they get into the turn is the variable (the bars turning is analogous to the flex of the board). I guess we could start a thread on countersteering here but that would be just a bit O.T.:) Ideas? Quote Link to comment Share on other sites More sharing options...
Neil Gendzwill Posted February 23, 2005 Report Share Posted February 23, 2005 Originally posted by astrokel I really don't think that this idea that the sidecut of the board is the largest turn the board can make in a pure carve actually holds water in the real world (how much can a board "carve" when it's flat?). A really stiff board with a small sidecut could make a bigger carved turn than a floppy board with a huge sidecut. When the board is flat, clearly it's not carving. If the board is such a noodle that it will fold up in any carve, that's a big design flaw don't you think? The point is, a board won't carve a bigger radius than it's sidecut, although it may be difficult to get it to carve even at the sidecut radius due to the fact that it will always flex somewhat in the turn. Quote Link to comment Share on other sites More sharing options...
astrokel Posted February 23, 2005 Report Share Posted February 23, 2005 Neil, I can see how it might make sense that the radius determines the largest turning radius but think of it... Does the entire edge of the board contact the "surface" of the snow. This does happen I suppose in ice conditions but even then it would be more like ice skating than snowboarding :). If you think of the real world there's more slop in the system than how we're thinking of it. That "noodle board" is extreme but it's only a model of what could happen and also it's more of a relative model than an absolute one. My only point was that that of trying to see the model in a different less static way. Keep your mind open. Something good might fall in...cool: : Quote Link to comment Share on other sites More sharing options...
forrest Posted February 23, 2005 Report Share Posted February 23, 2005 When you carve a snowboard the sidecut plays a different role than it first appears. I'll break it out into steps. 1. You put the board on edge. What happens? The two widest points contact the snow, hopefully the tip and the tail or something has gone horroribly wrong. 2.Your weight is centered between these two points. Since the edge of the board between these two points in not touching the snow the board flexs until the full edge contacts the snow at which point the board maintains its flex throughout the carve. This is how the board behaves when you get air and land in a carve, it provides a step by step progression. When you are carving normally the angulation and the flex happen progressively such that as you angulate more the board flexes more without the seperation between angulation and flexation so that you are not aware of one effect and then the other. 3. As you reach a higher and higher angulation the board must flex more and more to contact the snow creating a smaller and smaller circle allowing you to carve tighter and tighter, i'll try to repeat a few more words to make it a true mockery of the english language. A good way to see this effect is to take your board and lay it on the ground. When at 90 degrees see that only the tip and tail touch. At a small angulation flex the board until you have the full edge touching the surface, notice that as you angulate higher you must flex the board further to touch the ground. The sidecut determines how far you must flex the board before the full edge touches the ground. The smaller the sidecut the further you must flex the board before the edges touch meaning that you curve the board more which causes you to scribe a smaller circle. The reverse is true for a large sidecut board. The true effect of sidecut is to determine how much the board must flex before the edge comes into contact with the ground. This is where the stiffness takes effect, for a stiff board to achieve the necessary flexation force you either need more weight, heavier rider, or more speed because the speed along with the radius of the circle you are making determine the number of g's you are pulling, the more g's the higher the force generated for a specific weight and thus more flexation in the board. A quick thing on EC, take a look at the movies they achieve high angulation not 90 degrees. Look at your snowboard on the floor at 90 degrees no matter how hard you press the edge never will come into contact with the ground meaning you dont carve, which sucks. Quote Link to comment Share on other sites More sharing options...
SWriverstone Posted February 23, 2005 Author Report Share Posted February 23, 2005 From Jack and Iain Duncumb's article... But what is the use of this information? It comes in very handy when selecting a snowboard for a particular use. Say you were looking to purchase a new carving board and you narrowed your selections down to either Prior or Burton. Prior's WCR175 has a sidecut radius of 11.5m; Burton's Factory Prime 173 has a sidecut radius of 13.31m. What this tells you is that the Prior will reach a particular turn radius at a slower speed and lower edge angle than the Burton. Also, at a given speed, the Prior will be carving a tighter turn. This may be a good or a bad thing depending on what you want to do. If you spend most of your time riding the narrower trails of eastern North America, the Prior would be the better choice. If you ride wide open terrain where you can arc huge high speed turns at your leisure, the Burton might be a better choice.If you're a racer and you prefer the round-carves/stay-high technique, the Burton would carve a given radius at higher speed. If you race using the point-straight-at-the-gate-and-make-a-quick-turn-at-the-last-second technique, the Prior would make a quicker carve at a given speed. Or, let's say you've been riding something like Burton's FP164 and you're considering something longer. If you like the size and shape of the carves you make on the FP164, but you feel you need more edge hold, you would want to shop for something with more length but similar sidecut radius. Noting that the FP164 has a sidecut radius of 11.79m, you would be wise to select the WCR175. It will carve turns of similar radius, but alas, there's no such thing as a free lunch. You'll have to exchange the lighter weight and maneuverability of the 164 for the superior edge hold and stability of the 175. This is a great article, and cleared up some things for me. But one question remains, and I haven't heard a good answer to it. (Jack?)... How does waist width affect turn radius? (Or does it?) It seems reasonable to assume that the narrower the waist width, the less stiff the board...meaning the more the center of the board will deflect in a turn...meaning the tighter the turn radius will be. (Am I wrong?) Scott Quote Link to comment Share on other sites More sharing options...
CarvCanada Posted February 23, 2005 Report Share Posted February 23, 2005 It's weird to think about that at 90 degrees, no matter how much you flex the board, the sidecut will not fill the snow. When extremecarvers are at 90 degrees, their board is inclinated a bit less (with the torsional flex) maybe at 80-85 degrees. I'd guess sidecut hardly matters at 90 degrees like extremecarvers go, but how are you going to get to 90 degrees smoothly without a sidecut? --->What Jacques and Patrice do is angulate into the turn with bent knees and use the sidecut to get into a good carve, then right as they reach 90 degrees, they push out with their knees to tighten the radius and grip the snow. In the apex of the turn during the time that they are at 90 degrees, the board's behaviour is completely determined by flex, and the leg's pressure, and not by sidecut. This is why you need semi-soft snow, so that the tip and tail sinks in enough so that the waist and all the edge that's in between still pushes against the snow. Then when they suck the carve back in with their legs and loosen off the angulation, the sidecut comes into play again in loosening off inclination, radius of carve loosens off ( becomes bigger), and initiating the next turn. I'd also guess that since the tip is so sunk into the snow, the nose comes into play a lot in deflecting a lot of snow, and this is why the nose flaps so much in imperfect snow. I think some of that also has to do with them making the flex on the Swoard soft in front of the bindings to absorb imperfections while the waist and tail keep the edge grip. Maybe this is also why the nose is so flat and short. That's my understanding Maybe in the future, extremecarving boards will increase their sidecut radii to infinity right as you get to 90 degrees (rectangular board) so the edge hold will be awesome. Boards that dynamically change shape... But before then we'll probably be having too much fun cloudboarding on anti-gravity boards :) Quote Link to comment Share on other sites More sharing options...
Jack M Posted February 23, 2005 Report Share Posted February 23, 2005 Originally posted by SWriverstone How does waist width affect turn radius? (Or does it?) It simply does not. You can make a narrow board as stiff as a wide board, but it will probably be thicker. Quote Link to comment Share on other sites More sharing options...
astrokel Posted February 23, 2005 Report Share Posted February 23, 2005 Carvcanada, I think this is the key phrase: "use the sidecut to get into a good carve, then right as they reach 90 degrees, they push out with their knees to tighten the radius and grip the snow" The sidecut is used to enter the carve. The flex of the board determines the radius of the carve itself (along with rider weight and speed, this is actually the bugger of the argument because this makes the whole equation rather complicated) . When on edge what is actually gliding on the snow is not the steel edges (although that part is also gliding) but the part of the Ptex that is dug into what snow there is. Only on pure ice are the metal edges the only thing touching the surface. That's why torsional stiffness is so important in carving boards. Still developing the theory though... I think the diagrams that Jack did are correct but the assumptions that the snow is a flat surface doesn't pan out in the real world. In real snow the board acts more like a boat cutting through water than a knife (although the latter is easier to model theoretically). All I think I'm trying to say is that the potential turning radius of any particular board is more complicated that just looking at the sidecut... Quote Link to comment Share on other sites More sharing options...
SWriverstone Posted February 23, 2005 Author Report Share Posted February 23, 2005 Originally posted by Jack Michaud It simply does not. You can make a narrow board as stiff as a wide board, but it will probably be thicker. Okay...so waist width doesn't affect turn radius. Makes sense. So then can I assume that board flex (stiffness) does affect turn radius? ...and what does waist width affect? (Other than boot overhang or not.) Anything? Or is it just cosmetic? Slowly getting enlightened, Scott Quote Link to comment Share on other sites More sharing options...
nils Posted February 23, 2005 Report Share Posted February 23, 2005 Just to add few things to Carvcanada remarks.. EC is indeed a smooth but complex process that uses the sidecut then mostly the flex and the torsion control of the board. 1. entry / exits of the turns uses the sidecut, and we've found out that the range for most efficient EC turns is between 11-13 meters. Too small sidecut and the turns are too quick, too big and the speed it too big, and whole turn too slow. 2. laying down part with the extension of the legs ( push part) is combined with the board getting to 80-85° on the snow. The flex is then forced to a much tighter turn that the natural radius of the board, and since it is vertical almost, the mid part between the bindings tends to get away while the tips of the boards grip 3 apex: the board is fully flexed, and the tips fully grip, the radius is proportional to the pressure put on the legs in the extend part. What is to be noticed is: depending on the hardness of the snow, the board behaves differently. On perfect snow the torsion resistance is optimum, and the tips dig deep, conducting the board through the turn without skidding. The special design of the nose of our board allows it to guide the nose throughout the turn without eating too much, and without skidding. On hardest snows, the carbon parts and the specific soft flex (compare to other race decks) allows the board to not loose edge grip by guiding the edge along a perfect arc, without hard points or bend points on the edge length. Since there is no snow to push with the base on ice, but just the edges against ice, it becomes very tricky to do EC, because the push section has to be very smooth. If too violent the mid section of the board is likely to want to loose grip. this is also why the rotation technique helps there: it diminishes the lateral forces on the edge, having the whole rider+board to rotate along an circle rather than pushing itself toward a center. A bit complicated to explain, but the key is as said previously in every board the flex+ sidecut+ materials used, and also the shape of the nose/tails and the camber pattern. In my opinion having a ISO like measurement of those parameters is a dream that is too complicated to achieve! Nils Quote Link to comment Share on other sites More sharing options...
Neil Gendzwill Posted February 23, 2005 Report Share Posted February 23, 2005 Originally posted by SWriverstone ...and what does waist width affect? (Other than boot overhang or not.) Anything? Or is it just cosmetic? Quickness edge to edge, and overall weight of the board. Also a wider waist allows lower angles, so if you like low angles you want a wide board. IIRC the EC guys run relatively low angles. Quote Link to comment Share on other sites More sharing options...
skywalker Posted February 23, 2005 Report Share Posted February 23, 2005 Sorry, I was not totally correct. The difference between overall width (or: nose and tail width) and waist width is a function of eff. edge and scr. So with a given waist width (for binding angles) or a given overall width (for FIS rules) the other number just is a result ;) Originally posted by Jack Michaud Not really, waist width is up to the designer. For example, Donek makes two 171s - both with an 11.2m sidecut, but one that is 18cm wide at the waist and one that is 19.5cm. I suppose if you wanted to fix the nose and tail width at some arbitrary number, then yes, length, nose/tail width, and sidecut radius would determine waist width. However most designers fix the waist width at some number, and let the length and sidecut radius determine nose/tail width. Burton seems to take a different approach - they seem to fix length, waist width, and sidecut <i>depth</i>, which results in a random sidecut radius number. Quote Link to comment Share on other sites More sharing options...
Jack M Posted February 23, 2005 Report Share Posted February 23, 2005 Originally posted by SWriverstone So then can I assume that board flex (stiffness) does affect turn radius? Flex and sidecut are symbiotic. A board with no sidecut will not flex, no matter how flexible it is, it would just rail you into the woods in a straight line. A board that is too stiff won't bend easily into an arc, so it may turn wider than the sidecut naturally wants. Vice versa for a board that is too soft. Sidecut and flex need to be appropriately matched to each other and to your weight. Quote Link to comment Share on other sites More sharing options...
skywalker Posted February 23, 2005 Report Share Posted February 23, 2005 There are two things making Extremecarving possible: 1.) Torsion. As the board is twisted, the appearent radius is increased. The more a board is bent, the more it is usually twisted. This increases the carved radius with increased angulation of the board. I don't think, a torsionally totally stiff board would be the optimum for EC as it would bite the snow. 2.) Snow is not a plain ultrahard surface. If you look at the trenches the Extremecarvers make, you can see, that they become wider when the turns a fully laid down. The nose and the tail make the snow "move" or displace it. So as snow is a soft surface, the board's stiffnes and it's distribution affect the bending radius at a given angulation (as the board's torsional stiffness does). My little 2 Eurocent ;) Tom Quote Link to comment Share on other sites More sharing options...
Phil Posted February 23, 2005 Report Share Posted February 23, 2005 "Snow is not a plain ultrahard surface." Maybe not where you ride :D Quote Link to comment Share on other sites More sharing options...
skywalker Posted February 23, 2005 Report Share Posted February 23, 2005 please don't bore me to death! Quote Link to comment Share on other sites More sharing options...
skywalker Posted February 23, 2005 Report Share Posted February 23, 2005 o.k. some more ;) I was writing about something physical. Maybe not where you ride If it was, we wouldn't be snowboarding on it ;) ;) Quote Link to comment Share on other sites More sharing options...
Mellow Yellow Posted February 23, 2005 Report Share Posted February 23, 2005 dear lord this all makes my head hurt.... here's what I've found.... I step into my bindings... I start to move.... I turn... I have fun..... :p Quote Link to comment Share on other sites More sharing options...
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