multi radius sidecut
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multi radius sidecut
Does anyone know how to draw up a multi radius sidecut? do you draw up a parabola or multiple single radius arcs drawn together? And in CAD is there anything you can do with the major and minor radius of an arc in the line properties?
Brian
Re: multi radius sidecut
from what i`ve seen they drawed multiple sinlge radius, aligned tangentially.
they also built in some sort of flat camber/tiny little bit of rocker so that the whole thing worked...
but who would want to ride such skis anyway?! i can`t imagine such a ski to work 100%. it`s just not possible from a technical point of view. there is always a part of the ski that isn`t designed for how you ski in a particular moment.
they also built in some sort of flat camber/tiny little bit of rocker so that the whole thing worked...
but who would want to ride such skis anyway?! i can`t imagine such a ski to work 100%. it`s just not possible from a technical point of view. there is always a part of the ski that isn`t designed for how you ski in a particular moment.
plywood freeride industries - go ply, ride wood!
any knowledge on where the multiple arcs are placed with respect to each other along the ski? I can figure out how to get them to align tangentially, but am not sure on where to start the new arc at the tip and tail, or ratios of arc radii.
For example, If I where to make a ski with a 21m radius that was 180 cm with 170 of that as running length. of that 170 running length 55% tip and 45% tail. So from ski center there would be 93.5 cm of tip and 76.5 cm of tail. What should the second arc radii be at the tip and tail and what where should they be with respect to the center? 18m r @ a 10 cm set back?????
Do ski companies have ratio formulas that they have come up with or is it more of an art? are there different ratios for FIS or race stock skis compared to beginer or intermediate skis?
For example, If I where to make a ski with a 21m radius that was 180 cm with 170 of that as running length. of that 170 running length 55% tip and 45% tail. So from ski center there would be 93.5 cm of tip and 76.5 cm of tail. What should the second arc radii be at the tip and tail and what where should they be with respect to the center? 18m r @ a 10 cm set back?????
Do ski companies have ratio formulas that they have come up with or is it more of an art? are there different ratios for FIS or race stock skis compared to beginer or intermediate skis?
Brian
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threeninethree
- Posts: 172
- Joined: Fri Feb 23, 2007 8:11 pm
- Location: Massachusetts
I once considered using elliptical sidecut (like Line, but I'm not sure if that's what you mean here). I modelled an elliptical sidecut over a normal circular sidecut in solidworks to make a comparrison. The geometrical difference is very smal (a couple hundredth a of millimeter if I remember correctly), so I decided to go with a normal circular sidecut.
As I said, I am not sure that you are talking about the same thing, but if I were you I would make a quick and simple comparrison to a normal sidecut. Because there is a good chance that you will be wasting your time trying to replicate a skimanufacturer's marketing tricks.
As I said, I am not sure that you are talking about the same thing, but if I were you I would make a quick and simple comparrison to a normal sidecut. Because there is a good chance that you will be wasting your time trying to replicate a skimanufacturer's marketing tricks.
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threeninethree
- Posts: 172
- Joined: Fri Feb 23, 2007 8:11 pm
- Location: Massachusetts
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Cadman
If you take a radial sidecut and then bend the ski, isn't the result an ellipse? Seems like that is the case to me.
As far as the proceedure for using two radii, Find where you want your waist to be. Mirror your blend curve that you use at the widest point of the tip about the waist. At this point you need to designate the waist width
or a radius that you want. If you chose the radius then do an arc tangent to two entities and use the two blend curves that you mirrored. The waist will be whatever it ends up when you measure between the sidecut arcs.If you choose the waist width, the radius will be the result of an arc tangent to three entities. Now for the rear radius, do the same thing with the rear blend curves. The result will be two different radii with a perfect tangency
at the waist. If you apply the general rule of 55% where the waist goes,
you have to use two radii or let the tip and tail width be whatever they end up at, given a certain sidecut radius and running length. Other wise the waist will not end up where you want it.
If you have problems trying to understand this, send me a private post with your email address and I will send you a file. PLease designate what format you want, ie, igs, dxf, dwg etc
As far as the proceedure for using two radii, Find where you want your waist to be. Mirror your blend curve that you use at the widest point of the tip about the waist. At this point you need to designate the waist width
or a radius that you want. If you chose the radius then do an arc tangent to two entities and use the two blend curves that you mirrored. The waist will be whatever it ends up when you measure between the sidecut arcs.If you choose the waist width, the radius will be the result of an arc tangent to three entities. Now for the rear radius, do the same thing with the rear blend curves. The result will be two different radii with a perfect tangency
at the waist. If you apply the general rule of 55% where the waist goes,
you have to use two radii or let the tip and tail width be whatever they end up at, given a certain sidecut radius and running length. Other wise the waist will not end up where you want it.
If you have problems trying to understand this, send me a private post with your email address and I will send you a file. PLease designate what format you want, ie, igs, dxf, dwg etc
Sorry if I missed it, but has anyone recomended Dan Graff's SnowCad yet? It's a free download.
http://www.grafsnowboards.com/index.php?url=snocad-x
Parobolic side cuts can be made simply by biasing the center of the side cut fore or aft.
http://www.grafsnowboards.com/index.php?url=snocad-x
Parobolic side cuts can be made simply by biasing the center of the side cut fore or aft.
This might be a bit out of topic, but anyway;
As far as I know, the ”multi radius side cut” has developed the last years along with the new ski designs. Traditionally, the skis had a uniform flex pattern; either they were stiff or soft. For off pist skiing, a stiff ski with a lot of side cut is unpredictable, trying to catch the tip and tail. Soft skis are easier to control, and therefore they may have more side cut.
New ski designs combine traditional design features. They often have a stiff mid ski as a platform for stability during speed, edge control etc, but with soft tips and tails for floating and forgiveness. Because of the soft tips and tails it’s possible to add more side cut in these areas without compromising predictability and maneuverability, and at the same time adding more flotation. For the same reason we now see different reversed camber skis as well.
Line cal this “elliptical side cut”, and K2 cal it “progressive side cut”. As far as I can see; same thing different name.
Please correct me if I’m wrong
As far as I know, the ”multi radius side cut” has developed the last years along with the new ski designs. Traditionally, the skis had a uniform flex pattern; either they were stiff or soft. For off pist skiing, a stiff ski with a lot of side cut is unpredictable, trying to catch the tip and tail. Soft skis are easier to control, and therefore they may have more side cut.
New ski designs combine traditional design features. They often have a stiff mid ski as a platform for stability during speed, edge control etc, but with soft tips and tails for floating and forgiveness. Because of the soft tips and tails it’s possible to add more side cut in these areas without compromising predictability and maneuverability, and at the same time adding more flotation. For the same reason we now see different reversed camber skis as well.
Line cal this “elliptical side cut”, and K2 cal it “progressive side cut”. As far as I can see; same thing different name.
Please correct me if I’m wrong
Please correct me if I’m wrong
OK, you're wrong. "Elliptical" and "progressive" sidecut is not the same:the ("progressive")K2 Seth 179 has raidiuses (ski devided in tree, from the back tip to the front): 22,6m-20,7m-19,2m (total 20,5m)
The ("parabolic")Line E.Pollard 185 has radiuses: 16,1m-18,3m-16,3m (total 17,1m)
as you can see, the seth has a shorter radius towards the front tip, the EP has shorter radius towards both ends. This can even be spotted visually if you hold them up next to each other.
The EHP193 is another legendary ski with a pretty remarkable progressive sidecut (and flex!) i'll leave it to Cadman to comment about that one.
Just found this interesting topic...
I'm currently playing around with AutoCAD trying to think about my next pair of skis.
I came to the point I might have multiple radii for the sidecut (OK it's not a new concept, but for me it's an element I'd like to understand)
First I have to say I'm still wondering if I'm right when I decide the waist of the ski (narrowest point where radii tangents are parallel to the ski axis) to be 55% of the running length (from tip). Usually I design my tips slightly longer than the tails, with a 55%-45% ratio on the running length I feel like my ski will be balanced a lot on the back but it's mainly a visual impression, I guess it's what we want in a certain way...
Anyway, let's talk about radii now !
Let's first consider a 2 radii sidecut, apart form telling me how to draw them (I understood this part, thanks), what is the most common option ? bigger radius on the tip or on the tail, what difference will it make ?
My understanding (I'm not an expert skier so I might be wrong) is lets say I want to design a ski mainly for powder but which can make nice turns on the groomed (OK that's what we all want..). If we just look at the radii, I thinks it would be interesting to have a bigger radius on the tail, meaning a smaller one on the tip. Doing so, as I ride powder leaning a bit backwards I would mainly use the big radius and when I go on groomed I would be a bit more aggressive (lean forward) and use the small radius to make tighter turns.
Does that make sense or am I completely wrong ?
Now let's consider a 3 radii sidecut, how would you deal with that ? Personally I would put a bigger radius underfoot and small radii on tip and tail, always the same reason when I'm on groomed I would lean sideways a bit more and being more aggressive I would think I'm using more those tip and tail radii.
Last point : 2 or 3 (or more) radii ? Will it make a significant difference ?
Thanks for any help on that !
Ben
I'm currently playing around with AutoCAD trying to think about my next pair of skis.
I came to the point I might have multiple radii for the sidecut (OK it's not a new concept, but for me it's an element I'd like to understand)
First I have to say I'm still wondering if I'm right when I decide the waist of the ski (narrowest point where radii tangents are parallel to the ski axis) to be 55% of the running length (from tip). Usually I design my tips slightly longer than the tails, with a 55%-45% ratio on the running length I feel like my ski will be balanced a lot on the back but it's mainly a visual impression, I guess it's what we want in a certain way...
Anyway, let's talk about radii now !
Let's first consider a 2 radii sidecut, apart form telling me how to draw them (I understood this part, thanks), what is the most common option ? bigger radius on the tip or on the tail, what difference will it make ?
My understanding (I'm not an expert skier so I might be wrong) is lets say I want to design a ski mainly for powder but which can make nice turns on the groomed (OK that's what we all want..). If we just look at the radii, I thinks it would be interesting to have a bigger radius on the tail, meaning a smaller one on the tip. Doing so, as I ride powder leaning a bit backwards I would mainly use the big radius and when I go on groomed I would be a bit more aggressive (lean forward) and use the small radius to make tighter turns.
Does that make sense or am I completely wrong ?
Now let's consider a 3 radii sidecut, how would you deal with that ? Personally I would put a bigger radius underfoot and small radii on tip and tail, always the same reason when I'm on groomed I would lean sideways a bit more and being more aggressive I would think I'm using more those tip and tail radii.
Last point : 2 or 3 (or more) radii ? Will it make a significant difference ?
Thanks for any help on that !
Ben
A bad day skiing is always better than a good one at work...
Just a disclaimer: I have never built a pair of skis myself, and only in January started drawing them with CAD. Used snoCAD for a few years for imaginary snowboards and skis, but only now I´ve come to terms with the fact that I indeed will have to make my own press, build my own skis and soforth.nate wrote:Sorry to dig up an old topic, but question were left unanswered, and now I'm curious too. Two years later does anyone care to share some more insight on what multiple radii do and why we care?
Just a dual radius for starters.
I´ve drawn up a 204cm ski that´s 130/116/122. It´s not meant to turn easily on anything hard, but rather slarve around, as the sidecut spans no more than 1500mm. It´s pretty much drawn to crush through anything in a straight line, allowing directional changes from how much you want to push the ski. In a single radius arc, the sidecut is about 59m, and sidecut center is at the very center of the effective edge.
A ski designer friend of mine told me to try drawing it up with a dual radius - one radius for going aggressive with toe ball and shin pressure, one for relaxing a bit more, for skiing trees and such. I still wanted to have the same widths in my sidecut, but at the middle stations between 130 and 116, and 116/122, I pulled up lines, subtracting a bit from the average between the two ends. I wanted a deeper sidecut in the front, and a shallower in the back, allowing both for classic aggro and more modern, slarvy skiing, depending on my stance.
The front portion of the effective edge area (or sidecut, really), is 740mm long, and has a 34m radius. Mimics the old Rossignol B-Squad in that respect. The aft portion is 770mm long, and has a 75m radius. Average sidecut radius is then a 54.5m. The idea behind this is that it´s easier to relax a bit when you want to go straight and fast, but still gain some control of the direction with a simple shift of weight and stance.
The design is not even close to finished, but it´s starting to look good. Until I get a house with my wife, Igneous in Jackson will build this pair for me, and I have a prototype..
