Ideas:long radius stiff skis

[karma]

So I officially started shoping for some new skis, I'm looking for something 180-85ish, pretty stiff, 92-102 underfoot and looooooooong turn radius 30+???

This is what I have found so far, am I missing some?
Head SuperMojo 125-102-117 37.3 in a 183
Legend Pro 124-97-116 29 in 186
Ross Scratch BC 128-98-121 185 No radius on website, anybody know it?
B4 122-94-112 No Radius listed again
Stockli DP 125-94-111 29.4 in a 184
Gun Lab 188cm anyone know the demensions?


Fischer's seem to have more sidecut than I want, same for the Mantra, I know I dont really like Atomics so those are out. Is there anything else that should be added to the short list? What's the Radius on a pair of 188 Bros?

[marshalolson]

Gun Lab 188cm anyone know the demensions?

135-101-12?
pretty small radius... about 25m

[splat]

What's the Radius on a pair of 188 Bros?

Last time we checked it was around 29.

[H-wood]

K2 Apache Chief

[Mcwop]

Why not Atomics?

[seldon]

You can still find exploders.

I mean, they only made them for 9 years, there couldn't possibly be a pair around that isn't being skied.

[cj001f]

You can still find exploders.

You looked for them lately? They ain't exactly easy to find, every pair gets snapped up quick.

[karma]

Why not Atomics?

Something about them just feeling dead on my feet, and the lack of swing weight i think. I dont really know other than i can never really "feel" the ski beneath me.

[karma]

You can still find exploders.

I mean, they only made them for 9 years, there couldn't possibly be a pair around that isn't being skied.

Yeah 180 sploders are on the list and im on the lookout for a good pair, mostly as a ski for work. But im looking to get somthing new in addition for freeskiing days and comps.

[fez]

i think backcountry.com still has last year's m103's in the 183 for around four bills.

cant get much less side cut than that anymore.

<edit>
and i think slippy is selling a pair unmounted for tree fiddy</edit>

[addict]

I know some people'll hate me for this, but I'm with Karma on being anti atomic . Something about a ski that gets multiple hairline cracks in the edge that scares me. Seen waaaay too many pairs like that.

[descender]

Gotama 130-105-122 32m @190 Medium stiff
Explosive: 120-95-112 30.7 @ 180 35 @ 190
BigDaddy 133-107-123 34 @ 193

[karma]

Gotama 130-105-122 32m @190 Medium stiff
Explosive: 120-95-112 30.7 @ 180 35 @ 190
BigDaddy 133-107-123 34 @ 193

How can the gotama and Explosive be 3m diff at 190 when the dimensions are the same except 10mm thinner throughout?


Edit: Nevermind answered my own question, the Sploders are effectively longer since no twin tip.

[descender]

How can the gotama and Explosive be 3m diff at 190 when the dimensions are the same except 10mm thinner throughout?


Edit: Nevermind answered my own question, the Sploders are effectively longer since no twin tip.

Yeah and the sploders are stiffer, although I don't know if that plays into the calculation (I suspect not), but it does effect the amount of effort needed to bring them around.

[Meathelmet]

Yeah and the sploders are stiffer, although I don't know if that plays into the calculation (I suspect not).

That´s something i have allways wondered..

Lets say, you have two identical skis sidecut/length wise but different in stiffness, wouldnt the softer ski turn with a lesser radius in real life?

I mean,the reasoning behind this is, if you have a ski on its edge, you have a turn radius of X.
If you then apply pressure/flex to the ski so that it bends more, doesnt the sidecut increase,and thus lessen the turnradius to Z?

Y in hell am i wondering this anyway...?

Anyone?

[splat]

That´s something i have allways wondered..

Lets say, you have two identical skis sidecut/length wise but different in stiffness, wouldnt the softer ski turn with a lesser radius in real life?

I mean,the reasoning behind this is, if you have a ski on its edge, you have a turn radius of X.
If you then apply pressure/flex to the ski so that it bends more, doesnt the sidecut increase,and thus lessen the turnradius to Z?

Y in hell am i wondering this anyway...?

Anyone?

Yes, it will, to some degree, Meathelmet. I skied two Bro blems most of last season that had two different flexes. It wasn't very noticeable in soft snow, but a couple times on hardpack, I could feel the diffference in the flex. It wasn't so much that the softer ski carved a significantly smaller radius, but it flexed more in the turn. Most noticed on heavy-pressured steep ice.
Knowing the soft Bros will carve a shorter radius easier, due to the flex, I would have to say that your assumption is correct. The flex differential being the most influencing factor, of course.

[Vitamin I]

Yeah and the sploders are stiffer, although I don't know if that plays into the calculation (I suspect not).

Yeah, I would expect the radius number reported by manufacturer to depend only on the geometry of the ski---not on the force required to flex the ski into an arc, the weight of the skier, etc.

[descender]

That´s something i have allways wondered..

Lets say, you have two identical skis sidecut/length wise but different in stiffness, wouldnt the softer ski turn with a lesser radius in real life?

I mean,the reasoning behind this is, if you have a ski on its edge, you have a turn radius of X.
If you then apply pressure/flex to the ski so that it bends more, doesnt the sidecut increase,and thus lessen the turnradius to Z?

Y in hell am i wondering this anyway...?

Anyone?

This is definitely true. As the ski flexes, the shape of the effective edge on the snow will have a smaller radius. The snow doesn’t give a shit if the shape is due to the geometry of the ski or the flex. So in real life flex matters, but I don't know what goes into the radius calculation they list for each ski. I think there is a formula somewhere.

[72Twenty]

Just get some old 223cm DH boards and be done with it.

[splat]

I think there is a formula somewhere.

According to this guy, there are at least three ways to determine the radius of a sidecut. We simplified all this by overlaying a circle on the curvature of the sidecut in CAD, but I'm not so certain that is 100% accurate with complex radii involed. Nerd on this if you're up to it:


The quick way:

Look at the ski at three places: the waist (the narrowest part of the ski), where it's widest near the tip (the front end) and where it's widest toward the tail (the rear end). The engaged length (call it L) is the length from the front end to the rear end.

To simplify, assume the waist is halfway between the front end and the rear end. The width of the ski is different at the front and rear (i.e. the depth of the sidecut in front is different from in the rear). Neverthless, to simplify, treat them as if they're the same, by adjusting each so it's equal to the average.

So D = depth of sidecut = (front width / 2 + rear width / 2 - waist width) / 2.

Sketch this out on a piece of paper with the tip of the ski at the top, and the tail at the bottom; put a point way off to the right to represent the center of the circle whose arc includes the sidecut. Draw a line from the center to the front end and to the waist.

You've just drawn a right triangle, whose hypotenuse is the radius of the circle: one side (up & down) has a length equal to L/2; the other side (left & right) has a length equal to R-D.

So, applying the Pythagorean thereom:

R^2 = L^2/4 + (R-D)^2
= L^2/4 + R^2 - 2RD + D^2
R^2 - R^2 + 2RD = L^2/4 + D^2
2RD = L^2/4 + D^2
R = L^2/8D + D/2

If you want to simplify further, note that D is, at most, 30mm, so the D/2 term only affects the answer by 15mm (or .015 m). Since R is going to be something over 10 m, you don't lose any significant accuracy by omitting the D/2 term, since it's about 3 orders of magnitude less than the answer ... which is smaller than the error in your measurements.

So:

R = L^2 / 8D


The elaborate way:

Any three distinct points (call them A, B and C) lie on one (and only one) circle.(1)(2)

By definition, the center of a circle is equidistant from all of the points on the circle.

Start with points A and B. Draw a straight line between them. The mid-point halfway along this line is equidistant from both of them. The complete set of other points equidistant between them form a line that passes through this mid-point and is perpendicular to line AB. All of the points on this "midline" are equidistant from A and B.

Do the same thing with points A and C. All of these points on the AC midline are equidistant from A and C.

The point where the AB midline and the AC midline intersect is the center of the circle. The distance from that point to A = the distance from that point to B = the distance from that point to C. (3)


So, let's apply this to the problem.

Look at the right edge of a ski. The three points we're trying to run a circle through are three points along the edge of the ski: (A) at the waist, (B) where the ski is widest near the tip and (C) where the ski is widest near the tail.

The length of the ski (along the ski's centerline) from where it's widest at the tip (next to B) to where it's widest near the tail (next to C) is the "engaged length;" call it L. Part of it is in front of the waist (Lf), and part of it is to rear of the waist (Lr).

The sidecut has a depth in front (Df) and in the rear (Dr). The depth in front is half of (the width in front minus the width at the waist); same calculation at the rear.

Go into an x-y coordinate system, with A at the origin, the Y axis extending along the length of the ski, parallel to the centerline of the ski, and the X axis (obviously) perpendicular to that.

A is at 0,0
B is at Df, Lf
C is at Dr, -Lr

The AB midpoint is at Df/2, Lf/2
the AC midpoint is at Dr/2, -Lr/2

The slope of line AB is Lf/Df
The slope of line AC is -Lr/Dr

The slope of the AB midline is -Df/Lf
The slope of the AC midline is Dr/Lr

The equation that describes the AB midline is: y - Lf/2 = -Df/Lf (x - Df/2), or:
y = -Df/Lf * x + Df^2/2Lf + Lf/2

The equation that describes the AC midline is:
y = Dr/Lr * x - Dr^2/2Lr - Lr/2

The intercept lies at Ix, Iy. To determine the x-coordinate of the intercept:

Dr/Lr * Ix - Dr^2/2Lr - Lr/2 = -Df/Lf * Ix + Df^2/2Lf + Lf/2
(Dr/Lr + Df/Lf) Ix = Df^2/2Lf + Lf/2 + Dr^2/2Lr + Lr/2

Ix = (Df^2/2Lf + Lf/2 + Dr^2/2Lr + Lr/2) / (Df/Lf + Dr/Lr)

To determine Iy, insert Ix into one of the mid-line equations above:

Iy = -Df/Lf * Ix + Df^2/2Lf + Lf/2

Apply the Pythogroean theorem to determine the radius:

R = sqrt ( Ix^2 + Iy^2).

So that's the general way to determine the sidecut radius.


As a test, apply it to the "quick-way" simplified case above. In the simplified case, the waist is at the mid-point of the engaged length, so Lf = Lr = L/2. Also, we jiggle the front and back sidecut depths and treat them as if they're equal, so Df = Dr = D. Also, it's obvious that the center of the circle will lie on the x-axis, so R = Ix.

R = Ix = (D^2/L + L/4 + D^2/L + L/4) / (2D/L + 2D/L)
= (2D^2/L + L/2) / (4D/L)
= (2D^2/L + L/2) L/4D
= 2D^2/4D + L^2/8D
= D/2 + L^2/8D

Which is the same answer obtained above.


The FIS way:

The FIS measurement procedure is a bit odd, and would seem to be susceptible to anomolous results if someone wanted to tweak a ski design to obtain a particular measurement (the way yacht designers notoriously do).

The procedures is:

"1. Measurement of W, narrowest width of the ski (or minimum width at ski middle area)."
That's straightforward enough, though I'm not sure what the parenthetical is exactly supposed to mean.

"2. Measurement of L1, the front length, and L2, back length, from the W location."
The accompanying diagram makes it clear that L1 and L2 are the length all the way to the tip and tail, not just to the widest points. That's right: all the way to the point of the tip, which includes part that isn't even on the snow, normally.

"3. Calculation of L1-20% and reading of its location, measurement of S"
The accompanying diagram shows that S is the width of the ski at "L1-20%," that is: at the point that's 80% of the way from the waist to the tip. This isn't necessarily the widest part of the ski.

"4. Calculation of L2-10% and reading of its location, measurement of H"
This is similar: H is the the width of the ski at "L2-10%," that is: at the point that's 90% of the way from the waist to the tail. Again, this isn't necessarily the widest part.

"5. Calculation of R, the ski radius."
The formula supplied is
"Radius = L^2 / 2000 x (S + H - 2 x W), with L= (L1-20%) + (L2-10%) or 0.8 x L1 + 0.9 x L2."
If you work through this (realizing that the thousands are there to adjust for using different units to measure the ski and the radius), you find it reduces to L^2 / 8D,

BUT: instead of the actual wide-points near the tip and tail, they simply move back 20% of the front length from the tip and 10% of the rear length from the tail (= 15% of the total ski length).

I suppose in most cases this is pretty close. It's interesting to think, though, what a savvy designer could do to finesse the measurement. For example: stick a long narrow tip extension on. Make it long enough, and you could get it so that "S" width is actually narrower than the waist.

I suspect they don't worry about this, because they're sufficiently autocratic that if somebody produced a ski that tried to "game" the rules, they'd just ban it.

--------------

(1) Okay, there's an exception: if the three points lie in straight line, there's NO circle on which all three lie. To put it another way, they lie on an undefined "circle" with an infinite radius.

(2) The circle has to lie in the plane defined by the three points: a circle in any other plane will only intersect the 3-points' plane at (at most) two points. In the rest of the following, we'll just assume we're staying within the plane defined by the three points ... so that (for example) the set of points that are equidistant from two of the points form a line, not a plane.

(3) In the special case referred to in (1), the two mid-lines are parallel, so there is no intercept.

[karma]

ouch, my head hurts...

[Vitamin I]

...
Ross Scratch BC 128-98-121 185 No radius on website, anybody know it?
B4 122-94-112 No Radius listed again...

I have an Excel file where I keep info like this...

I have 23m radius on the 2005-6 185cm Rossi Scratch BC

I have about 31-ish on the 2005-6 185 Rossi B4 (but it flexes a lot)

.

[Vitamin I]

135-101-12?
pretty small radius... about 25m

yeah, I have
1080 Gun Lab 188cm 135-101-126 24.2m radius

.

[Vitamin I]

K2 Apache Chief

i have
2004/2005 K2 Apache Chief 188cm 126-98-116 about 31.1m radius(190) (but probably flexes a lot)

[Vitamin I]

...am I missing some?...

consider:

skis at http://www.bumtribe.fr/ski-dre.html

PMGear Bro Model stiff (should feel like high radius)

Iggie FFL or FAT or ODC 180 or 190 custom flex, if ya got the cash to blow

DB surreal 185

volkl explosiv

old 183m Volant McH Hucksters

But you said looooooooong turn radius:
so throw down on iggies or else buy head m103, or settle for explosives.

.