You bring up a good point about modelling, and it really depends what you are trying to achieve.
If you want to predict the final shape of a ski under a real loaded situation then this is fairly challenging without the use of FEA (though not impossible). The distribution of load along the ski will be a function of the stiffness profile of the core and so as far as I am aware you would have to run an iterative program to find the solution. This is possible, but the question is will it really represent reality? - I would argue that irregularities in the snowpack will dominate in the real world and so this level of analysis is not really going to produce results that are any more relaven thatn the model of a point load or constant bending moment. In addition I would question what you would do with the final information? What is your target shape - are you trying to achieve a perfect arc or what?
Alternatively if you want to provide a repeatable way to characterize the skis that you have and compare them then all you need to do is analyse a loading pattern that you can recreate accurately in practice (either a constant bending moment as suggested earlier in this link, or a point load). The final deflection of this analysis will clearly not be the final shape of the ski under real skiing load, but it does provide a comparison and you can start to look at existing skis or designs and say - "I want a bit more tail stiffness in the next one" or compare the deflection to the deflection of a ski that you really like. This is about the best way to make a start.
In case you didn't see it there is a link to my flex predictor on a link somewhere in here. This is a simple FEA analysis carried out on a spredsheet which makes life easy for you interms of analyzing the multi directional fiberglass etc... At the moment it assumes point loads, but given that we have profiles from constan bending moments on here I will shortly add the expected profile from that to the sheet soon.
In short while it might be an interresting academic excercise, I am not sure that beining able to predict the exact shape of the ski under snow load gives you any more useful information than any other test simulation . The important thing is to pick a standard by which you can compare skis. Predicting the exact deflection under the correct (real skiing) loading would be useful if you knew what shape curve you wanted to end up with, but the analysis for that would be more of a challenge than predicting the deflection!
I am happy to include different cases in my spreadsheet if people would like to see a deflection under uniform load or any other cases.
B.
Accurate, replicable method of measuring ski flex (long)
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
Over the past few weeks, I have been conducting tests on various plastics and woods to observe how their flex charactoristics change when exposed to freezing temperatures, as compared to room temperature testing. The results have been really interesting. Basically, all of the materials tested exhibited notable increases in stiffness, some more dramatic than others. Certain thermoplastics that were flexible at room temp became quite inflexible and brittle at low temperature. All thermoset plastics increased in stiffness as the temperature decreased... some became brittle and some did not. Most all woods increased in stiffness, though not as much as the plastic materials. One plastic material did not increase too much in stiffness, but showed much greater rebound activity, when frozen, than the other plastics (increased 'pop'?). Overall I tested about 30 different plastic materials.
None of my testing was very scientific. I just placed the sample of uniform size in the freezer for an hour, quickly pulled it out, placed it in the testing device, and loaded it before it warmed up too much. After my testing, I'm left with the feeling that all of these room temperature ski flex test proceedures that we've been doing may well be of limited value when it comes to actual flex charactoristics of the ski when on snow. Like I said above, some of the common materials that I tested went from being fairly flexible to downright stiff and inflexible when frozen.
For me, it really leads back to how the ski feels on real snow, and how well it holds up after lots of time on the snow.
G-man
None of my testing was very scientific. I just placed the sample of uniform size in the freezer for an hour, quickly pulled it out, placed it in the testing device, and loaded it before it warmed up too much. After my testing, I'm left with the feeling that all of these room temperature ski flex test proceedures that we've been doing may well be of limited value when it comes to actual flex charactoristics of the ski when on snow. Like I said above, some of the common materials that I tested went from being fairly flexible to downright stiff and inflexible when frozen.
For me, it really leads back to how the ski feels on real snow, and how well it holds up after lots of time on the snow.
G-man
definately bambi, that would be very interesting.
I made a machine once that pressurizes the ski uniformaly. It is made with 100 compression springs, but would be more accurate with pneumatic or hydraulic power distribution. The problem with this tecnique is that the results we get are too complex to use other than visually. the camber, momentum and stiffness values are all mixed in one curve, and get difficult to differentiate afterwards. But as an internal comperison between similar skis it is great.
my point is that we want to know just the stiffness, not some strange combined value of stiffness, camber and momentum.
I made a machine once that pressurizes the ski uniformaly. It is made with 100 compression springs, but would be more accurate with pneumatic or hydraulic power distribution. The problem with this tecnique is that the results we get are too complex to use other than visually. the camber, momentum and stiffness values are all mixed in one curve, and get difficult to differentiate afterwards. But as an internal comperison between similar skis it is great.
my point is that we want to know just the stiffness, not some strange combined value of stiffness, camber and momentum.
A very important issue, and very important to discuss. I will be doing more temperature tests with real skis, have done a few so far and the stiffness did not vary extremely much. Don't think that should make us give up the flex comparison project though.
did you do tests of fibreglass g-man? after all that is the most important stiffening element (mostly).
did you do tests of fibreglass g-man? after all that is the most important stiffening element (mostly).
endre,
Very good points that you make. Yes, I agree that the room temp lab tests provide a lot of useful baseline information and that they are important in the progression of ski design. No, I didn't actually test a thermoplastic (epoxy) in a fiberglass matrix. You are right in that it would be a most valuable comparison. My greatest reason, in the beginning, for doing the tests was to try to determine (a little more objectively) how the side wall material might influence the ski flex at different temperatures. Because the side wall material is relatively thick and wide (12mm x 10mm +/-) at the waist of the ski, theoretically, it could have significant effect in that area. After seeing just how stiff some of the plastics can get when they get cold, I'm even more sure that certain types of plastic could adversely effect ski flex. On the other hand, some could benefit the desirable flex.
Cheers
G-man
Very good points that you make. Yes, I agree that the room temp lab tests provide a lot of useful baseline information and that they are important in the progression of ski design. No, I didn't actually test a thermoplastic (epoxy) in a fiberglass matrix. You are right in that it would be a most valuable comparison. My greatest reason, in the beginning, for doing the tests was to try to determine (a little more objectively) how the side wall material might influence the ski flex at different temperatures. Because the side wall material is relatively thick and wide (12mm x 10mm +/-) at the waist of the ski, theoretically, it could have significant effect in that area. After seeing just how stiff some of the plastics can get when they get cold, I'm even more sure that certain types of plastic could adversely effect ski flex. On the other hand, some could benefit the desirable flex.
Cheers
G-man
here's a picture of me doing some old school flextesting, i think this picture shows pretty much how flex could be visualized in a simple way, (maby not this brutal)
anyway, to take a picture of the whole bending process provides a good visual image of the stiffness through the ski, eventhough it is a mixed image.
Hey endre,
Great pic. That's quite a building... lots of character. Are those ski core blanks behind you?
The ski that you are flexing appears to have about 3 different flex arcs going on... one very soft one at the tip, a little stiffer one at the tail, and a pretty stiff arc through the waist. According to my own theories and experience, that ski wouldn't turn very smoothly. I have a lot of respect for your work and experience in this area. How do you feel about this skis theoretical (or real, if you've actually skied it) on snow performance.
Just out of curiousity, is that ski a cap ski or a sandwich ski?
G-man
Great pic. That's quite a building... lots of character. Are those ski core blanks behind you?
The ski that you are flexing appears to have about 3 different flex arcs going on... one very soft one at the tip, a little stiffer one at the tail, and a pretty stiff arc through the waist. According to my own theories and experience, that ski wouldn't turn very smoothly. I have a lot of respect for your work and experience in this area. How do you feel about this skis theoretical (or real, if you've actually skied it) on snow performance.
Just out of curiousity, is that ski a cap ski or a sandwich ski?
G-man
Yes that room is hardcore, 8 meters tall and has got an 8ton crane in it.
Actually that ski right there has quite nice flex characteristics. The soft tip lifts the ski up of the soft snow while the relatively stiffer middle and tail give me support in cruising position and landings. I don't think I agree in your theory about the "roundness" of flex, and the ski will get a different curve when bent by snow anyway.
Through the flex studies I don's see any connection between a "round flex" (whatever that really is) and skiing characteristics. I think that the turning capabilities of a ski is not the only, and definately not the most important reason for varying the flex along the ski.
I think that the ski can be divided into parts by analyzing the flexcurve: You have the mid ski where the binding is mounted, the front -and back ski, and just where the curve goes from convex to concave in each end we call the tip and tail of the ski (front -and back tip) The tip lengths vary a lot. The main purpose of the tips, especially the front tip, is to absorb the terrain. Different flexshapes give different feelings. I go more and more towards a steep curve in the tips, a little bit like the curve on salomon and stöckli skis. (and my ski on the pic.)
Another important factor i think you can vary a lot with the flex shape is the way the ski floats in powder. I tried a special version of the goode monstro last winter, and it just dived straight down, even though the waist is huge. After flex testing it I noticed that the tip of the ski was stiffer than anything I have seen , while the mid ski was pretty soft (the whole flexcurve was very uneven, maby caused by difficulties shaping the special core?)
Other, narrower skis floated a lot better, especially those with the softer tips.
The ski is a sandwich ski with symmetrically laminated core (like the blanks in the background) and triax fibreglass. Pretty standard construction.
Actually that ski right there has quite nice flex characteristics. The soft tip lifts the ski up of the soft snow while the relatively stiffer middle and tail give me support in cruising position and landings. I don't think I agree in your theory about the "roundness" of flex, and the ski will get a different curve when bent by snow anyway.
Through the flex studies I don's see any connection between a "round flex" (whatever that really is) and skiing characteristics. I think that the turning capabilities of a ski is not the only, and definately not the most important reason for varying the flex along the ski.
I think that the ski can be divided into parts by analyzing the flexcurve: You have the mid ski where the binding is mounted, the front -and back ski, and just where the curve goes from convex to concave in each end we call the tip and tail of the ski (front -and back tip) The tip lengths vary a lot. The main purpose of the tips, especially the front tip, is to absorb the terrain. Different flexshapes give different feelings. I go more and more towards a steep curve in the tips, a little bit like the curve on salomon and stöckli skis. (and my ski on the pic.)
Another important factor i think you can vary a lot with the flex shape is the way the ski floats in powder. I tried a special version of the goode monstro last winter, and it just dived straight down, even though the waist is huge. After flex testing it I noticed that the tip of the ski was stiffer than anything I have seen , while the mid ski was pretty soft (the whole flexcurve was very uneven, maby caused by difficulties shaping the special core?)
Other, narrower skis floated a lot better, especially those with the softer tips.
The ski is a sandwich ski with symmetrically laminated core (like the blanks in the background) and triax fibreglass. Pretty standard construction.
endre,
I often toss around my personal theories hoping that someone will disagree with them. I'm always delighted when that happens because it's such a great opportunity to test current thinking and learn some new stuff. So, thanks for disagreeing and taking the time to explain why.
I have probably skied 30 or 40 different skis in the past ten years, not a really large number compared to some folks, but I generally have kept up with the current popular models from year to year. I mostly liked the newer models when they came out, probably because they just kept getting wider from year to year. I still have most of those old skis and I've tested the flexes of many of them on my 'flex analyzer', and really, it seems to me that the basic flex designs haven't changed very much over the years... just the width and the side-cut have primarily changed. But, honestly, none of the newer models that I skied on from year to year, ever really made me say "WOW!!" on the first time out. It wasn't until I skied on my own skis, which have a really round flex, that I found myself saying, "WOW!, WOW!, WOW!" on every turn. They just simply seem to turn as though they are locked onto some sort of perfectly curved track, and that I'm just along for the blissful ride. So, if I seem a little obsessive about round circular flex arcs, that is where it comes from... I just can't get that amazing feeling out of my mind, and I never got it with any other ski. I skied my skis about 50 or 60 days last spring, and I got that same feeling on every turn. I'm really not absolutely sure why they ski so differently, but that is what I like about having these discussions.
It seems that most of the skis that I see in your graphs (again, very impressive work on the graphs) are alpine skis, so that leads me to believe that you may do a fair amount of alpine skiing (I'm guessing about the ski models... I've only been on alpine gear once in my life, and that was 30 years ago, so I don't follow alpine models). I do wonder if tele skiers and alpine skiers might each appreciate different flex qualities in a ski... at least to some minor degree. When I ski, I sit low and right over my rear ski in a tele turn, so, I can really feel it when the rear ski locks into the carve. Could I be 'feeling' the ski flex differently than an alpine skier would? I like your description of how the purpose of the tips is to absorb the terrain, but, to be honest, I never give my tips much thought while skiing... they seem to do just what I need them to. Could it be that the tele body position (lower and longer) demands less performance from the tip design than the alpine body position? It seems that many contemporary ski designers are saying that there is not much difference in a tele ski and an alpine ski now-a-days, but I'm wondering if there might be a little more to it than that. Any feedback from skiers who swing both ways?
G-man
I often toss around my personal theories hoping that someone will disagree with them. I'm always delighted when that happens because it's such a great opportunity to test current thinking and learn some new stuff. So, thanks for disagreeing and taking the time to explain why.
I have probably skied 30 or 40 different skis in the past ten years, not a really large number compared to some folks, but I generally have kept up with the current popular models from year to year. I mostly liked the newer models when they came out, probably because they just kept getting wider from year to year. I still have most of those old skis and I've tested the flexes of many of them on my 'flex analyzer', and really, it seems to me that the basic flex designs haven't changed very much over the years... just the width and the side-cut have primarily changed. But, honestly, none of the newer models that I skied on from year to year, ever really made me say "WOW!!" on the first time out. It wasn't until I skied on my own skis, which have a really round flex, that I found myself saying, "WOW!, WOW!, WOW!" on every turn. They just simply seem to turn as though they are locked onto some sort of perfectly curved track, and that I'm just along for the blissful ride. So, if I seem a little obsessive about round circular flex arcs, that is where it comes from... I just can't get that amazing feeling out of my mind, and I never got it with any other ski. I skied my skis about 50 or 60 days last spring, and I got that same feeling on every turn. I'm really not absolutely sure why they ski so differently, but that is what I like about having these discussions.
It seems that most of the skis that I see in your graphs (again, very impressive work on the graphs) are alpine skis, so that leads me to believe that you may do a fair amount of alpine skiing (I'm guessing about the ski models... I've only been on alpine gear once in my life, and that was 30 years ago, so I don't follow alpine models). I do wonder if tele skiers and alpine skiers might each appreciate different flex qualities in a ski... at least to some minor degree. When I ski, I sit low and right over my rear ski in a tele turn, so, I can really feel it when the rear ski locks into the carve. Could I be 'feeling' the ski flex differently than an alpine skier would? I like your description of how the purpose of the tips is to absorb the terrain, but, to be honest, I never give my tips much thought while skiing... they seem to do just what I need them to. Could it be that the tele body position (lower and longer) demands less performance from the tip design than the alpine body position? It seems that many contemporary ski designers are saying that there is not much difference in a tele ski and an alpine ski now-a-days, but I'm wondering if there might be a little more to it than that. Any feedback from skiers who swing both ways?
G-man
hmm.. interesting assumtion about me being an alpine skier G, i am not. But the skis we test in the magazne often come with alpine rig, so I have to strap on my Lange's now and then.
Anyway I agree that tele -and alpine skis should have different flex. My conclution though, after testing lots of tele specific and pure alpine skis are:
There is a much larger difference between the brands than different kinds of skis. It is pretty easy to recognize a brand by the shape of the flexcurve, but it is absolutely impossible to find a general tendency to what differentiates a teleski from an alpine ski.
When we ski alpine the power distribution throughout the ski is a little bit different from when we tele. You have pressure on your front ski, when you tele you completely rely on the tail and the ski as a total through the stance. The tele turn and the linked nature of the binding automatically gives you a lot more "absorbing motion" when you ski. When I tele, My wheight is allmost completely on the tail of the "first ski". This is a very laidback position, and gives very assymmetrical bending force to the ski. (actually, a little bit like the way I stand on the picture)
It is a general assumption that tele skis should be softer than alpine skis. I totally disagree in this assumption. Because of the absorbing nature of the tele technique (described above) I think tele skiers would benefit from a stiffer back -and middle ski, and because you have little pressure to the front of the ski, you can have very soft tips that gives you lots of float and an even smoother ride.
Alpine skis need to be softer and more forgiving, afterall there is no linked connection between your legs and the snow. All of the absorbing activity is done by the skis, and finally your legs.
I think it is great that we can have this discussion about ski flex! I can't comment on your experience with your own skis, because I don't know their flex characteristics compared to any other skis. But the most important thing is that you burn for your opinions and have a clear idea of what your skis should be like, that brings us foreward. (and, I think, further than the large brands)
I will post curves of some more tele spesiffic skis in a while.
Anyway I agree that tele -and alpine skis should have different flex. My conclution though, after testing lots of tele specific and pure alpine skis are:
There is a much larger difference between the brands than different kinds of skis. It is pretty easy to recognize a brand by the shape of the flexcurve, but it is absolutely impossible to find a general tendency to what differentiates a teleski from an alpine ski.
When we ski alpine the power distribution throughout the ski is a little bit different from when we tele. You have pressure on your front ski, when you tele you completely rely on the tail and the ski as a total through the stance. The tele turn and the linked nature of the binding automatically gives you a lot more "absorbing motion" when you ski. When I tele, My wheight is allmost completely on the tail of the "first ski". This is a very laidback position, and gives very assymmetrical bending force to the ski. (actually, a little bit like the way I stand on the picture)
It is a general assumption that tele skis should be softer than alpine skis. I totally disagree in this assumption. Because of the absorbing nature of the tele technique (described above) I think tele skiers would benefit from a stiffer back -and middle ski, and because you have little pressure to the front of the ski, you can have very soft tips that gives you lots of float and an even smoother ride.
Alpine skis need to be softer and more forgiving, afterall there is no linked connection between your legs and the snow. All of the absorbing activity is done by the skis, and finally your legs.
I think it is great that we can have this discussion about ski flex! I can't comment on your experience with your own skis, because I don't know their flex characteristics compared to any other skis. But the most important thing is that you burn for your opinions and have a clear idea of what your skis should be like, that brings us foreward. (and, I think, further than the large brands)
I will post curves of some more tele spesiffic skis in a while.
endre,
Yes, from observing the stance that you choose to apply flex pressure to the ski (in the above pic), I should have realized that you might well be a tele skier... my mistake
.
After many years of watching tele skiers (many of them who are really good), it is very clear to me that there are lots of different styles of tele skiing. I have a fairly strong Tai Chi background (which sort of naturally influences how I move through even basic daily chores), and I'm sure that it influences my skiing style to some degree.. for better or worse, I'm not sure... when I ski, I may look like a real dork to other skiers. From your description of your tele style, it seems that you and I probably have somewhat differing techniques, each of which would probably best benefit from a somewhat differing ski flex. I hadn't realized this before our exchange of ideas on this thread. I don't think this new realization will cause me to change the way that I design my current flex patterns, but it certainly is a concept that I'll keep tucked away in the back of my mind in case, someday, I end up designing and building skis for other people.
I look forward to seeing your tele specific curve data.
thanks again,
G-man
Yes, from observing the stance that you choose to apply flex pressure to the ski (in the above pic), I should have realized that you might well be a tele skier... my mistake
.After many years of watching tele skiers (many of them who are really good), it is very clear to me that there are lots of different styles of tele skiing. I have a fairly strong Tai Chi background (which sort of naturally influences how I move through even basic daily chores), and I'm sure that it influences my skiing style to some degree.. for better or worse, I'm not sure... when I ski, I may look like a real dork to other skiers. From your description of your tele style, it seems that you and I probably have somewhat differing techniques, each of which would probably best benefit from a somewhat differing ski flex. I hadn't realized this before our exchange of ideas on this thread. I don't think this new realization will cause me to change the way that I design my current flex patterns, but it certainly is a concept that I'll keep tucked away in the back of my mind in case, someday, I end up designing and building skis for other people.
I look forward to seeing your tele specific curve data.
thanks again,
G-man
Very interesting discussion!
I believe the flex curve of the ski is the most important factor when it comes to ski characteristics. Being an engineer, my ski making process has started with calculating the flex pattern I like to have on my dream ski, based on models I like and dislike.
I’ve done alpine skiing for the last 8 years. Before that I did telemaking for about 15 years. When I started doing alpine skiing I wanted my skis to be really stiff, as I like going fast. Really stiff skis are nice when going fast, and the conditions are not too soft, but they have two major drawbacks; first they tend to dive in the soft snow, and secondly you have to be a powerful rider to take them threw tight terrain. All the soft skis I tried were really crap at high speed, and when trying to stomp landings they took me to the back seat or I tramped them all the way to China. For me stiff skis were the best compromise.
Until two years ago I was a “the stiffer the better” skier, but that changed when I tried the K2 Maide’n. They have a relatively stiff mid ski, with a progressively softer front ski, and a soft back ski. I don’t think they are the perfect ski, but they made me realize it was possible to make a ski that’s stable at speed, float in pow and being easier to handle in tight places and in places with a lot of terrain.
After testing a lot of skis, I believe my dream ski has a relatively stiff mid to make them stable at speed. The front ski has to be progressively softer, with a relatively soft tip. This makes the ski float better in pow, but also makes the skis more forgiving on hardpack and boilerplate (the superstiff skis makes all the forces go right into your legs). The back ski has to be relatively stiff to make it easier to stomp landings and to give me a nice kick out of the turns. The last part of the back ski and the tail has to be softer, making it less likely to hook up, and making panic turns easier. In fact I believe my “dream ski” is not as far from Endre’s ski pictures above, even though I’m an alpine skier.
When it comes to turning capabilities I think the side cut plays an important role. Big side cut makes the ski easier to turn at low speed, but more nervous at high speed. The opposite goes for less side cut.
Another factor that has to be considered together with the flex and the side cut is the taper of the ski. A big taper (pin tail) makes the tip float better in soft snow (the tail is pressed down), but it also makes it harder to do carved turns. With big taper the back ski has the tendency to “drift” while trying to make carved turns. Some skiers like this characteristic because of its predictable and forgiving feeling; personally I don’t, especially not on all round off-piste skis.
On the other hand a smaller taper makes it easier to make carved turns, and gives you a better kick if you put pressure on the back ski at the exit of the turn. Twin tip skis made for switch riding and landing I pow has a small taper combined with a soft tail to make it tail float.
Again, this is my personal preferences. I really don’t think there’s any “final solution” as it’s all a question of riding style and technique. A sign of that are all the different models coming from skier-influenced brands, experimenting with flex and shape trying to accomplish the same result.
Happy Turns!
I believe the flex curve of the ski is the most important factor when it comes to ski characteristics. Being an engineer, my ski making process has started with calculating the flex pattern I like to have on my dream ski, based on models I like and dislike.
I’ve done alpine skiing for the last 8 years. Before that I did telemaking for about 15 years. When I started doing alpine skiing I wanted my skis to be really stiff, as I like going fast. Really stiff skis are nice when going fast, and the conditions are not too soft, but they have two major drawbacks; first they tend to dive in the soft snow, and secondly you have to be a powerful rider to take them threw tight terrain. All the soft skis I tried were really crap at high speed, and when trying to stomp landings they took me to the back seat or I tramped them all the way to China. For me stiff skis were the best compromise.
Until two years ago I was a “the stiffer the better” skier, but that changed when I tried the K2 Maide’n. They have a relatively stiff mid ski, with a progressively softer front ski, and a soft back ski. I don’t think they are the perfect ski, but they made me realize it was possible to make a ski that’s stable at speed, float in pow and being easier to handle in tight places and in places with a lot of terrain.
After testing a lot of skis, I believe my dream ski has a relatively stiff mid to make them stable at speed. The front ski has to be progressively softer, with a relatively soft tip. This makes the ski float better in pow, but also makes the skis more forgiving on hardpack and boilerplate (the superstiff skis makes all the forces go right into your legs). The back ski has to be relatively stiff to make it easier to stomp landings and to give me a nice kick out of the turns. The last part of the back ski and the tail has to be softer, making it less likely to hook up, and making panic turns easier. In fact I believe my “dream ski” is not as far from Endre’s ski pictures above, even though I’m an alpine skier.
When it comes to turning capabilities I think the side cut plays an important role. Big side cut makes the ski easier to turn at low speed, but more nervous at high speed. The opposite goes for less side cut.
Another factor that has to be considered together with the flex and the side cut is the taper of the ski. A big taper (pin tail) makes the tip float better in soft snow (the tail is pressed down), but it also makes it harder to do carved turns. With big taper the back ski has the tendency to “drift” while trying to make carved turns. Some skiers like this characteristic because of its predictable and forgiving feeling; personally I don’t, especially not on all round off-piste skis.
On the other hand a smaller taper makes it easier to make carved turns, and gives you a better kick if you put pressure on the back ski at the exit of the turn. Twin tip skis made for switch riding and landing I pow has a small taper combined with a soft tail to make it tail float.
Again, this is my personal preferences. I really don’t think there’s any “final solution” as it’s all a question of riding style and technique. A sign of that are all the different models coming from skier-influenced brands, experimenting with flex and shape trying to accomplish the same result.
Happy Turns!