Sidecut, mounting points, and profile

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kohlrabi
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Joined: Thu Aug 25, 2005 8:52 pm

Sidecut, mounting points, and profile

Post by kohlrabi »

I am in the beginning stages of designing a ski for myself

While looking at other skis I have I've noticed a few things.

Some skis (park skis mainly) are mounted directly in the center. this is also right at the apex of the sidecut.

Other skis are mounted somewhat behind the centerline of the ski. I'm not able to determine whether the sidecut apexes at this point, or at the very center of the ski. Do you think there'd be any advantage to adjusting the apex of the sidecut arc to correspond to the center of the mount point rather than the center of the ski?

I know there's a book on the physics of skis, but it looks like a pretty involved read... I've only taken first year physics... I've always figured hell was something that *might* happen at the end of one's life. Not a self inflicted learning experience selected in one's prime. ;)
broskier
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Post by broskier »

I think it depends on the type of riding you'll be doing. From what I've noticed, most skis have the sidecut centered a bit ahead of the center of the mounting point. I think this was used more when skiers performed fewer switch maneuvers. If you've ever arced a turn switch on a pair of skis mounted center you can notice not only the increase in stability from the larger tail, but also the maneuverbility due to the sidecut being more centered, so to speak. Just my 2 cents.
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G
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Location: Nashville, TN

Post by G »

I have read a little bit about how to determine exactly where to mount the bindings, and need some help in making sure I have this correct before finalizing my design.

My understanding is that the ball of the foot should be over the midpoint of the chord, and then the middle of the boot is estimated.

How are others determining this?
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G
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Post by G »

Would it be possible to add the center boot location on one of your CAD drawings, and possibly a side view showing the relationship of the camber to the side cut? This would be a big help. Thanks.
Alex
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Post by Alex »

I use a simple calculation of area for determining the mounting point. 42% of the area should be behind the boot center for powder skiing. On my Voelkl Gotama this is a bit to much forward for powder but you can carve it well on piste. With my reverse sidecut homebuild i can lean as much forward as possible without making the tip dive (it just slows down). I put the widest point (reverse sidecut) of the ski to the boot center.
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G
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Post by G »

Thanks for the 42% number. If you were building a std all mountain ski with sidecut and camber, would you design it so the min width corresponded with the boot centre (assuming the 42% rule) and the max camber was situated at this point as well?
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hose-man
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Post by hose-man »

Alex, How did you arrive at the 42% number? I've been measuring skis & moving bindings to evaluate performance & have yet to find a reliable number. I'll apply your 42% to what I've tried so far & see how it compares..... I'm curious!
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G
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Post by G »

There was a posting in another area of the forum that suggested a ratio of 200/250 for the area behind/above the binding. So the percent for the tail would be 200/450 = 44%, which is pretty close to the 42%.

hose-man....i sent you a few pm's re surplus fire hose you still may have for sale...can you let me know please. Thanks.
Alex
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Post by Alex »

There was an article in a freeskiers magazine some time ago. They said that 42% is the maximum you should go backwards to keep the ski still manageable on the slopes. A more versatile setup is 43-44% percent. We tested the 42% percent on some skis (Rossi B3, Atomic Sugar Daddy, Karhu Jill, Voelkl Gotama) and found that this is a good compromise for freeriding.

The min. width seems to be always a little bit 1-3cm in front of the boot center. But i'm not shure about this...
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