I'm thinking of trying to make a double or triple radius sidcut on my next ski, my concern is I have some thoughts about it but I'm not sure about anything.
For a double radius for example, I plan on having the transition at the narrowest point (mounting point on my skis) and I was wondering what would be the effect of having a larger radius on the front than on the back (20m front - 17m back for example) or the opposite : 17m front -20m back.
My vision of it is when I go fast I have a tendancy to put more weigth on the back so I would need a larger radius to be more forgiving, When I want to make quick tight turns I'm more "agressive" and I more likely lean forward, I would benefit a tighter radius on the front then.
Am I completely out of the track ? any thought about this ?
Multi-radius sidecut
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
Multi-radius sidecut
A bad day skiing is always better than a good one at work...
I once made an 18/23 m dual radius ski (front/back) with the transition directly under foot. And the results were . . . not good.
The exact dimensions were 131-97-120 sidecut, 178.8cm long. ~5mm camber (each) with a stiff core, 13.5 mm under foot to 2.5 mm tip/tail, made out of vertical laminate bamboo flooring.
When they are in a pure carve, they feel like the center of the turn is in front of the mounting point. The only way I can describe this is think of taking a pair of old elan scx's and mounting the bindings a good 6-12" back (15-30 cm). It just doesn't feel right.
When in a skidded turn on firm corduroy (on a cold morning), they vibrated so violently that they made my foot feel like it was going to explode. This could be due to the lack of damping, or to the resonant modes induced by the geometry - I have not figured it out yet.
They also have weird turn initiation - you need to adjust your body mechanics/balance depending on whether you want to skid or carve a turn.
Some positive feedback - they held a pure carve turn incredibly well. When the edges get dull, they ski a bit better and more forgiving. And they ski well in corn/soft snow.
Here are some photos of them (the short ones on the left). Note the second mounting line - even after re-mounting, they still felt awkward.
Photos can also be seen at
http://www.skibuilders.com/phpBB2/viewtopic.php?t=1330
If you are near Reno/Tahoe and ever want to try them PM me.
The exact dimensions were 131-97-120 sidecut, 178.8cm long. ~5mm camber (each) with a stiff core, 13.5 mm under foot to 2.5 mm tip/tail, made out of vertical laminate bamboo flooring.
When they are in a pure carve, they feel like the center of the turn is in front of the mounting point. The only way I can describe this is think of taking a pair of old elan scx's and mounting the bindings a good 6-12" back (15-30 cm). It just doesn't feel right.
When in a skidded turn on firm corduroy (on a cold morning), they vibrated so violently that they made my foot feel like it was going to explode. This could be due to the lack of damping, or to the resonant modes induced by the geometry - I have not figured it out yet.
They also have weird turn initiation - you need to adjust your body mechanics/balance depending on whether you want to skid or carve a turn.
Some positive feedback - they held a pure carve turn incredibly well. When the edges get dull, they ski a bit better and more forgiving. And they ski well in corn/soft snow.
Here are some photos of them (the short ones on the left). Note the second mounting line - even after re-mounting, they still felt awkward.
Photos can also be seen at
http://www.skibuilders.com/phpBB2/viewtopic.php?t=1330
If you are near Reno/Tahoe and ever want to try them PM me.
Brian
Well I would never have expected that !
There are a bunch of ski with progressive sidecuts so it might somehow work, maybe they have 3 radii and that makes the difference.
Does someone have a similar experience ?
Just for information I don't plan such a big difference between my 2 radii, it would be a max of 2 meters difference... don't know...
There are a bunch of ski with progressive sidecuts so it might somehow work, maybe they have 3 radii and that makes the difference.
Does someone have a similar experience ?
Just for information I don't plan such a big difference between my 2 radii, it would be a max of 2 meters difference... don't know...
A bad day skiing is always better than a good one at work...
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doughboyshredder
- Posts: 1354
- Joined: Mon Sep 17, 2007 7:37 pm
I have multiple radiuses on my boards with a tighter radius in the front for driving turns, mellow radius under foot for straightlining, and then tighter than the center but mellower than the front for pow cranking. I love it. You can definitely feel the difference in carves based on very minor weight adjustments. I would think it would translate well to skis, but I have never skied so I have no idea.
Doing a multi-radius sidecut like doughboyshredder's design, and having a more balanced tip/tail makes sense.
I am curious as to how "parabolic sidecuts" are designed, as in focus and vertex placement, and how they compare to a triple radius sidecuts (tip-underfoot-tail) and single radius sidecuts.
Doughboy, what ratios and placement are you using for your sidecut radii?
and were you the one who built the board with "straightline"? I'm having a tough time finding that post.
I am curious as to how "parabolic sidecuts" are designed, as in focus and vertex placement, and how they compare to a triple radius sidecuts (tip-underfoot-tail) and single radius sidecuts.
Doughboy, what ratios and placement are you using for your sidecut radii?
and were you the one who built the board with "straightline"? I'm having a tough time finding that post.
Brian
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doughboyshredder
- Posts: 1354
- Joined: Mon Sep 17, 2007 7:37 pm
I am dividing the sidecut in to four equal sections. The front section has one radius the two center sections have one radius, and the back section has a different radius. The two center sections radius is converted to straight lines intersecting in a "V" at the center of the board.
here's the thread about one of the boards built with straight line. http://www.skibuilders.com/phpBB2/viewtopic.php?t=1727
As I've said before anybody that wants to try it out, please do.
here's the thread about one of the boards built with straight line. http://www.skibuilders.com/phpBB2/viewtopic.php?t=1727
As I've said before anybody that wants to try it out, please do.
Well I just modified my design to have 3 radii, it's slightly more complicated to design than only 2 radii but I managed to have something I like...
The skis will be 178 long, about 150cm of running length.
Sidecut radius on the tip section 15m, underfoot (45cm split equally around mounting point) has a 18m radius and tail section 16.5m radius.
With dimensions of 134-95-124 it might work...
Mounting point is @55% of the running length.
The program for this skis is 40% powder, 59% soft groomed, 1% hard packed -> mid-fat with moderate sidecut...
The skis will be 178 long, about 150cm of running length.
Sidecut radius on the tip section 15m, underfoot (45cm split equally around mounting point) has a 18m radius and tail section 16.5m radius.
With dimensions of 134-95-124 it might work...
Mounting point is @55% of the running length.
The program for this skis is 40% powder, 59% soft groomed, 1% hard packed -> mid-fat with moderate sidecut...
A bad day skiing is always better than a good one at work...
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doughboyshredder
- Posts: 1354
- Joined: Mon Sep 17, 2007 7:37 pm
I have designed several pair of skis with dual radius sidecuts and I really like the way they perform. I prefer a longer radius in the back of the ski so the ski sticks to the fall line more in the latter part of the turn. I used to have some Igneous Fat Fall Lines that had this concept and I based one of my designs on that ski. With a narrower tail and higher taper angle than most industry skis I find that the skis exit the turn easier.
For skiing on groomed and carving I definitely prefer more equal sidecut in the tail but I haven't built anything for predominantly on piste.
I seem to remember a Salomon GS race ski that used to have a tighter radius towards the tail with a narrower tip than tail. I never go to ski them but I am guessing that they never caught on.
I have designed my skis so the narrowest part of the ski is under boot midsole. For those who are doing single radius sidecuts, are you mounting your bindings so the ski waist(narrowest part of ski) is more towards the heel?
For skiing on groomed and carving I definitely prefer more equal sidecut in the tail but I haven't built anything for predominantly on piste.
I seem to remember a Salomon GS race ski that used to have a tighter radius towards the tail with a narrower tip than tail. I never go to ski them but I am guessing that they never caught on.
I have designed my skis so the narrowest part of the ski is under boot midsole. For those who are doing single radius sidecuts, are you mounting your bindings so the ski waist(narrowest part of ski) is more towards the heel?
On my last skis I didn't really took a great care thinking where to install the bindings, it came out good but in don't know the exact position from the narrowest point.
After I read a post from G-man, I now want to install my bindings so the mounting point (slightly forward the mid-sole) is matching the narrowest part of the ski, which is @55% of the running length, and hopefully I'll also be able to make a flex pattern that follows this guideline.
It seems to make sense and if you manage to get all your curve centers (sidecut and flex pattern) on a same line perpendicular to ski axis and running thru your mounting point you might end up with a pretty smooth ride. (don't know if I'm clear,,, G-man was but as it went thru my head in french and I now have to translate so it becomes a bit messy...)
Thanks for the advices and experiences anyway, I modified my "mainly groomed" model to have 3 radii as I said in a previous post but I sticked to only 2 radii with more taper for the 2 "powder" models (one standard design and one with rockered tips)
After I read a post from G-man, I now want to install my bindings so the mounting point (slightly forward the mid-sole) is matching the narrowest part of the ski, which is @55% of the running length, and hopefully I'll also be able to make a flex pattern that follows this guideline.
It seems to make sense and if you manage to get all your curve centers (sidecut and flex pattern) on a same line perpendicular to ski axis and running thru your mounting point you might end up with a pretty smooth ride. (don't know if I'm clear,,, G-man was but as it went thru my head in french and I now have to translate so it becomes a bit messy...)
Thanks for the advices and experiences anyway, I modified my "mainly groomed" model to have 3 radii as I said in a previous post but I sticked to only 2 radii with more taper for the 2 "powder" models (one standard design and one with rockered tips)
A bad day skiing is always better than a good one at work...
ben_mtl,
Yes, you were very clear. Just as an update on what I have posted in prior threads regarding binding mount position, I have been fortunate enough this past spring and early summer to be able to do a ton of further testing in that regard. Consistent spring corn provides for a great testing ground. On various pairs of skis, I moved bindings forward and back, often on the same day and on the same test slope. The moves were generally in increments of 2 cm. I got so used to my skis, that it became pretty apparent when I felt that I wanted to be just a couple of cm's further forward or rearward... and it was quite clear when the bindings were mounted just in the right spot. I was actually a bit surprised that I became so sensitive to binding location. Anyway, after all the testing was done, all the mounts were at locations just as you described in your post above, with the possible revision that I mount so that the point on my boot that is about 3 cm's behind the ball of the foot lines up with the perpendicular line of the curve centers. This is for telemark skiing, and for the 'style' or technique of tele skiing that I do. It seems that no two telemark skiers use the same technique (particularly in terms of weighting), and I tend to get back on my rear ski pretty heavily, so I tend to focus my binding mount theory more on what my rear ski is doing in terms of weight. Most tele skiers that I see don't get a lot of actual weight on the rear ski, so I think they would benefit from more of a forward mount (center of boot more towards the perpendicular curve line). Of course, there are lots of varying opinions about binding mount positions, and things are only going to get more and more complicated as we move more in the direction of multiple side-cut arcs. We builders always have to be messing around with something, eh. At least we have finally maxed out on the ski width thing, realizing that wider isn't always better. Then we went through the full rockered thing and realized that full rocker has a limited use. Now we're in the midst of the early rise/rockered tip thing, which can also really mess with the old concepts of binding placement, depending on where the widest part of the forward side-cut curve falls in relation the the changes in running surface that are created by the early rise tip. Lots of on-snow testing may be the best way to find the optimal binding mount location... kind of a problem in the off-season.
G-man
Yes, you were very clear. Just as an update on what I have posted in prior threads regarding binding mount position, I have been fortunate enough this past spring and early summer to be able to do a ton of further testing in that regard. Consistent spring corn provides for a great testing ground. On various pairs of skis, I moved bindings forward and back, often on the same day and on the same test slope. The moves were generally in increments of 2 cm. I got so used to my skis, that it became pretty apparent when I felt that I wanted to be just a couple of cm's further forward or rearward... and it was quite clear when the bindings were mounted just in the right spot. I was actually a bit surprised that I became so sensitive to binding location. Anyway, after all the testing was done, all the mounts were at locations just as you described in your post above, with the possible revision that I mount so that the point on my boot that is about 3 cm's behind the ball of the foot lines up with the perpendicular line of the curve centers. This is for telemark skiing, and for the 'style' or technique of tele skiing that I do. It seems that no two telemark skiers use the same technique (particularly in terms of weighting), and I tend to get back on my rear ski pretty heavily, so I tend to focus my binding mount theory more on what my rear ski is doing in terms of weight. Most tele skiers that I see don't get a lot of actual weight on the rear ski, so I think they would benefit from more of a forward mount (center of boot more towards the perpendicular curve line). Of course, there are lots of varying opinions about binding mount positions, and things are only going to get more and more complicated as we move more in the direction of multiple side-cut arcs. We builders always have to be messing around with something, eh. At least we have finally maxed out on the ski width thing, realizing that wider isn't always better. Then we went through the full rockered thing and realized that full rocker has a limited use. Now we're in the midst of the early rise/rockered tip thing, which can also really mess with the old concepts of binding placement, depending on where the widest part of the forward side-cut curve falls in relation the the changes in running surface that are created by the early rise tip. Lots of on-snow testing may be the best way to find the optimal binding mount location... kind of a problem in the off-season.
G-man