Post by JimRatliff on Apr 2, 2014 17:12:17 GMT -7
HORIZONTAL SKI MEASUREMENTS.
The following are some terms that are Common Knowledge among skiers.
Ski Description pages usually include the following pieces of data. They reference measurements of the width of the ski, and are often printed on the skis "topsheet".
EXAMPLE: HEAD SuperShape Magnum
Dimensions: 128-72-106 @170cm Radius: 13.1
TIP WIDTH: The widest point of the front of the ski that is normally in contact with the snow is 128 mm wide. I am unsure if the "in contact with the snow" is always the way this width is measured, especially with rockered and early rise skis.
WAIST WIDTH: The width of the ski in the middle at the narrowest point is 72mm wide.
TAIL WIDTH: The widest part of the tail (that is normally in contact with the snow) is 106mm.
REFERENCE LENGTH: The reference length is the 170cm model. Different manufacturers handle lengths differently. Head varies the dimensions and the sidecut with length. For example, the 163cm length is 127-71-105 with a sidecut radius of 12. Fischer skis usually have the same tip-waist-tail dimensions even for different lengths, and a greater variation is radius.
SIDE CUT RADIUS: 13.1m is the "sidecut radius" number, and that is what we wish to discuss most.
Side Cut refers to the shape of the ski when viewed from above (see the picture). Today’s modern skis have much more Side Cut than earlier models (now usually referred to "straight" skis"), and this shape should be what causes the ski turn (just twisting the skis is the less desirable option). As the ski is tipped on edge the tip and tail dig into the snow a little bit more. This change in the distribution of force on the ski will cause the ski to bend -- how much depends on the relative stiffness of the ski and the relative weight and skiing speed of the skier because force=mass*acceleration (pressure on the ski = skier weight * skier speed).
Also, in general terms, the more pronounced the side-cut the shorter the bent ski will turn, so sidecut radius is a useful piece of reference information. HOWEVER, sidecut radius is NOT the SAME AS turn radius, and the two terms are often used interchangeably when they should not be. As alluded to above, the turning radius of a ski is a result of the ski's sidecut, the ski's stiffness, AND the skier's weight and speed. The turning radius of a ski will change as the skier's speed changes, because the force applied to the center of the ski is proportional to the skier speed and the skier weight (which is pretty constant). If you have trouble bending your ski, strap a couple of 10 pound weights around your waist .
It is my opinion that the recreational skier is much better served with a high quality,easily bent ski rather than a racer-like stiff ski.
TURN RADIUS:
Because of the variables described above, there is nothing stamped on the ski that indicates the turn radius, and there is no such thing as a single turn radius. A heavy skier and a light skier on the same ski at the same length will generate dramatically different turn radii with that ski. The heavy skier may bend the ski excessively while the light skier may not be able to bend it all (at the same speed). However, a light skier at high speed (racing) may be able to bend the ski even more than the heavy skier could at the slower speed.
PROGRESSIVE SIDECUT:
Traditionally, the Side Cut shape of a ski describes a perfect arc, or part of a circle, which runs from the tip to the tail of the ski.
But as skis have gotten wider in the past few years, a traditional Side Cut and radial design have caused problems, especially in longer All Mountain skis. Using a Radial Side Cut design tip to tail on wide and long skis destined for All Mountain or powder use can cause hooking of the tip, over twisting of the ski and a very difficult release at the end of the turn.
The solution is to make the Side Cut less towards the tail thereby making the ski slightly narrower and also friendlier to ski on because the tail will release more easily - a bonus in crud or powder.
From a marketing perspective, when describing how a pair of skis can perform a multitude of turn sizes; Progressive Side Cut, Varied Side Cut, Multi Radius, Dual Radius all refer to this recent trend in ski design where manufactures are specifically sculpting ski shapes and using materials to make it easier for skiers to actively adjust the size and shape of their turns, including during the turn.
Expert skiers are able to vary their turn shape to increase or decrease its size while in different conditions, by adjusting edge angle and pressure to the tip or tail of the ski, but this skill takes time to acquire and practice. However, with modern manufacturing and designs, skis are now being produced that make for quick turn initiation and easy tail release allowing for skiers to achieve the same results as an expert skier in various conditions.
Different manufactures have approached this theme in a mixture of ways such as manipulating the shape of the ski tip to make it slightly wider but softer, which will let the tip engage smoother making the ski edge and carve in a more consistent arc. Others have included Rocker to raise the tip of the ski off the snow, which reduces the contact length on hard pack, producing a smaller turn, but still allowing the ski to float when off piste. Some designs are made with adaptive Cambers allowing more effective edge only when the ski is rolled beyond a certain angle, while others have combined all these elements into one ski.
The following are some terms that are Common Knowledge among skiers.
Ski Description pages usually include the following pieces of data. They reference measurements of the width of the ski, and are often printed on the skis "topsheet".
EXAMPLE: HEAD SuperShape Magnum
Dimensions: 128-72-106 @170cm Radius: 13.1
TIP WIDTH: The widest point of the front of the ski that is normally in contact with the snow is 128 mm wide. I am unsure if the "in contact with the snow" is always the way this width is measured, especially with rockered and early rise skis.
WAIST WIDTH: The width of the ski in the middle at the narrowest point is 72mm wide.
TAIL WIDTH: The widest part of the tail (that is normally in contact with the snow) is 106mm.
REFERENCE LENGTH: The reference length is the 170cm model. Different manufacturers handle lengths differently. Head varies the dimensions and the sidecut with length. For example, the 163cm length is 127-71-105 with a sidecut radius of 12. Fischer skis usually have the same tip-waist-tail dimensions even for different lengths, and a greater variation is radius.
SIDE CUT RADIUS: 13.1m is the "sidecut radius" number, and that is what we wish to discuss most.
Side Cut refers to the shape of the ski when viewed from above (see the picture). Today’s modern skis have much more Side Cut than earlier models (now usually referred to "straight" skis"), and this shape should be what causes the ski turn (just twisting the skis is the less desirable option). As the ski is tipped on edge the tip and tail dig into the snow a little bit more. This change in the distribution of force on the ski will cause the ski to bend -- how much depends on the relative stiffness of the ski and the relative weight and skiing speed of the skier because force=mass*acceleration (pressure on the ski = skier weight * skier speed).
Also, in general terms, the more pronounced the side-cut the shorter the bent ski will turn, so sidecut radius is a useful piece of reference information. HOWEVER, sidecut radius is NOT the SAME AS turn radius, and the two terms are often used interchangeably when they should not be. As alluded to above, the turning radius of a ski is a result of the ski's sidecut, the ski's stiffness, AND the skier's weight and speed. The turning radius of a ski will change as the skier's speed changes, because the force applied to the center of the ski is proportional to the skier speed and the skier weight (which is pretty constant). If you have trouble bending your ski, strap a couple of 10 pound weights around your waist .
It is my opinion that the recreational skier is much better served with a high quality,easily bent ski rather than a racer-like stiff ski.
TURN RADIUS:
Because of the variables described above, there is nothing stamped on the ski that indicates the turn radius, and there is no such thing as a single turn radius. A heavy skier and a light skier on the same ski at the same length will generate dramatically different turn radii with that ski. The heavy skier may bend the ski excessively while the light skier may not be able to bend it all (at the same speed). However, a light skier at high speed (racing) may be able to bend the ski even more than the heavy skier could at the slower speed.
PROGRESSIVE SIDECUT:
Traditionally, the Side Cut shape of a ski describes a perfect arc, or part of a circle, which runs from the tip to the tail of the ski.
But as skis have gotten wider in the past few years, a traditional Side Cut and radial design have caused problems, especially in longer All Mountain skis. Using a Radial Side Cut design tip to tail on wide and long skis destined for All Mountain or powder use can cause hooking of the tip, over twisting of the ski and a very difficult release at the end of the turn.
The solution is to make the Side Cut less towards the tail thereby making the ski slightly narrower and also friendlier to ski on because the tail will release more easily - a bonus in crud or powder.
From a marketing perspective, when describing how a pair of skis can perform a multitude of turn sizes; Progressive Side Cut, Varied Side Cut, Multi Radius, Dual Radius all refer to this recent trend in ski design where manufactures are specifically sculpting ski shapes and using materials to make it easier for skiers to actively adjust the size and shape of their turns, including during the turn.
Expert skiers are able to vary their turn shape to increase or decrease its size while in different conditions, by adjusting edge angle and pressure to the tip or tail of the ski, but this skill takes time to acquire and practice. However, with modern manufacturing and designs, skis are now being produced that make for quick turn initiation and easy tail release allowing for skiers to achieve the same results as an expert skier in various conditions.
Different manufactures have approached this theme in a mixture of ways such as manipulating the shape of the ski tip to make it slightly wider but softer, which will let the tip engage smoother making the ski edge and carve in a more consistent arc. Others have included Rocker to raise the tip of the ski off the snow, which reduces the contact length on hard pack, producing a smaller turn, but still allowing the ski to float when off piste. Some designs are made with adaptive Cambers allowing more effective edge only when the ski is rolled beyond a certain angle, while others have combined all these elements into one ski.