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Sidecut Symmetry

post #1 of 12
Thread Starter 
Lately some companies have been making twin-tips with a symmetrical sidecut. The tips and tails are the same width and the waist is exactly in the center. The advertising hype is that such a ski will work equally well both forward and backward.

Would it be more truthful to say that such a ski would work equally badly in both directions? I figure there is some good reason that traditional skis are wider in the tip than the tail, and that there is some compromise to be made in having both ends the same, or nearly the same. It seems one would have to give up some degree of performance in the forward direction in order to gain some skiing switch.
post #2 of 12
I feel the same way. Symetrical skis might be good for a park ski or people who spend a lot of time going backwards. I like slightly wider tips on my skis. lol
post #3 of 12
Symmetrical ski's are definately park oriented!
They will usually have a larger turn radius because to make them symmetrical they will make the tip less wide vd making the tail wider.
Most of the time you'll want a ski to engage in the turn as soon as you put it on edge (wide tip) but you want an easy turn release too (smaller tail).

But, as always, it's the skier that ski's.
They can be skied anywhere, they're just not made for it.
post #4 of 12
Thread Starter 
Quote:
Originally Posted by Schussboelie View Post
Symmetrical ski's are definately park oriented!
They will usually have a larger turn radius because to make them symmetrical they will make the tip less wide vd making the tail wider.
Most of the time you'll want a ski to engage in the turn as soon as you put it on edge (wide tip) but you want an easy turn release too (smaller tail).

But, as always, it's the skier that ski's.
They can be skied anywhere, they're just not made for it.
That's what I was trying to figure out; I just couldn't get all the concepts to line up so I could make sense out of them.

Being an old schooler, I'm still having trouble getting my head around the idea that 20m is a long turn radius, but this year, for the very first time, my straight skis were starting to look funny, and shaped skis were starting to look normal, instead of the other way around.
post #5 of 12
Quote:
Originally Posted by Morrison Claystone View Post
Being an old schooler, I'm still having trouble getting my head around the idea that 20m is a long turn radius, but this year, for the very first time, my straight skis were starting to look funny, and shaped skis were starting to look normal, instead of the other way around.
That's funny!
Mind you though, I'm a European.
I think we tend to ski a lot more on short radius ski's than North-Americans do.
SL ski's and their derivatives make out a very big part of the market here.

For me, anything with a radius higher than 17m I prefer to avoid, 12m to 15m is my preferred range.
Luckily I've discovered Icelantic
post #6 of 12
The difference between tip width and tail width is called Taper Angle. Draw two straight lines down the sides of the ski from the widest point of the tip to the widest point of the tail. the angle formed where these 2 lines intersect is the taper angle.

Taper refers to the relationship between the width of the tip and the width of the tail, i.e., a ski with a wide tip and a narrow tail will have a larger taper than a ski with little difference between tip and tail widths.

A larger taper angle provides more versatility in turn shape. The tail does not tend to lock into a specific turn shape or in other words it is easier to vary turn shape since the tail is narrower.

From PSIA Archives:

Tip and Tail Relationship/Taper
Many ski designers and manufacturers refer to the relationship between the tip and the tail as the taper. The wider the tip relative to the tail the greater the taper. Narrowing the tip or flaring the tail can reduce taper, and this relationship can have a dramatic effect on how the ski performs.
Traditional Taper
The tip is 9 to 12 millimeters wider than the tail.
Characteristics:
aAllows the tip to pull through the turn; rewarding your forward/lateral movements with a cleaner turn initiation.
aAllow you to adjust turn radius with more or less tip pressure/edge angle.
aMake it easy to release the old turn and start a new one.
aEnable you to easily release the tail of the ski for skidding.
aRequire you to control the ski with fore/aft movements.
aEnable you to make both short-and long-radius turns.

Small Taper
Tip and tail dimensions may be the same. In general, however, the tip is 6 to 8 millimeters wider than the tail.
Characteristics:
aAllow both ends of the ski to support the turn. Both the tip and the tail contribute to turn radius, much like a four-wheel-drive vehicle simultaneously engages all four wheels.
aAllow you to use more of the ski. With the tip and tail both lending more support to the ski's middle section, the ski-to-snow contact is relatively substantial. In other words, much like an oversized tennis racquet or golf club, this type of ski has a large "sweet spot," which is more forgiving of imprecise movements.
aAllow you to stay on task. Once you start a turn the ski seems to want to stay engaged and keep turning. However, these skis tend to have one predominant turn radius.
aAre easy to operate. These skis provide a lot of confidence and security as you feel the skis are working for you rather than against you.

Large Taper
The tip is more than 12 millimeters wider than the tail.
Characteristics:
Offer an extremely strong tip initiation if desired.
aEnhance the skier's ability to control turn radius, but geared toward experts because they're not very forgiving of imprecise movement.
aAllow you to release out of the turn very quickly.
aRequire precise control of fore/aft balance throughout the turn because
post #7 of 12
Atomicman, that's an interesting document, because I'd guess this year the majority of skis between 70 and 90 mm waist width had tapers of 12-14 mm. Are we moving toward more taper and, according to the list, more demanding skis?

My own sense is that greater taper has benefits off groomed not mentioned (rides up in crud or pow, tail is easy to slide/pivot in bumps or trees) and must not be as demanding as the document suggests given the popularity of big tapers like Contact 11/Ltd/whatever the hell it's being called next year, the AC40, or even the Mantra.
post #8 of 12
Quote:
Originally Posted by beyond View Post
Atomicman, that's an interesting document, because I'd guess this year the majority of skis between 70 and 90 mm waist width had tapers of 12-14 mm. Are we moving toward more taper and, according to the list, more demanding skis?

My own sense is that greater taper has benefits off groomed not mentioned (rides up in crud or pow, tail is easy to slide/pivot in bumps or trees) and must not be as demanding as the document suggests given the popularity of big tapers like Contact 11/Ltd/whatever the hell it's being called next year, the AC40, or even the Mantra.
I found the statement that skis with smaller taper angle (tail closer to tip dimension) are more difficult to ski well, since they are less versatile opposite of my experience. If you are not making tunrs right in the wheel house of their symmetry you are fighting the shape. the tail does not want to let go smoothly. So it would seem to me, at least from my experience, that a ski which is more of a one trick pony more symmetrical forcing it's shape on the skier, is more difficult for most.

The ski that comes to mind for me is the Atomic SL9.12 or later the SL9. it was fine as long as you were making one turn shape. If not it would "Wag" like a ski skate! this was probably excerbated by the fact it was a 160cm. Neither the Sl 9.16 (the predecesor or the SL11 exhibited this behavior due to a much more taper angle.

also the old Fischer RCR had identical 89MM tip and tail dimension and they promoted it as "dual sidecut" since the tip to the waist and waist to the tail had the identical dimensions. It was very difficult to ski this ski on steeper hard snow without it chattering unless you were exactly on it's dictated turn shape.
post #9 of 12
One of the very first successful shaped skis was perfectly symetrical - the Kneisel Ergo.
post #10 of 12
Thread Starter 
Since old style straight skis have small taper angles, would a shaped ski with a small taper ski similarly to a straight ski, or would the deeper sidecut tend to force a turn shape onto the skier but the straight ski wouldn't?

The description above makes it sound like a shaped ski with a 9-12 mm taper could be skidded like a straight ski with a 3-5 mm taper more easily than a shaped ski with a 3-5 mm taper.

Am I reading this correctly?
post #11 of 12
Thanks for sharing that info Atomicman -- good stuff to know.
post #12 of 12
Yes, I think you are absolutely right.
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