volklgirl
Ski Diva Extraordinaire
Ski Construction – What It Means to You
The way a ski “feels” or behaves depends on the combination of its measurements, the materials used in its construction, and its construction methods. This means that 3 skis with the exact same dimensions could still feel significantly different depending on their construction. Fortunately, some generalizations of behavior can be made when it comes to measurements, materials, and construction methods, but first we’ll examine the basics of construction, stiffness, measurements, and tail shape.
CONSTRUCTION
The main parts of a ski: Base, edges, sidewall (part of the topsheet in this picture), core and filler material, and top sheet. Here is a simplified picture:
In modern skis, the base material is a clear, black or colored plastic material called P-Tex. The topsheet and sidewalls are typically a plastic called ABS, but could also be wood or stainless steel. The core materials usually used include foam, wood, Kevlar, carbon, fiberglass, epoxy, rubber, and metal (stainless steel, aluminum, magnesium or titanium).
There are 3 widely used construction methods: Torsion box, laminate, and “cap” or monocoque construction.
STIFFNESS
There are 3 key components to consider when examining ski stiffness. All three are at least partially determined by the type and location of material used in the core, the construction method used, and the number and location of metal layers in the ski. Overall stiffness is the general stiffness along the length of the ski. Torsional rigidity is the stiffness across the width of the ski, or amount of twist when edged. Flex pattern is the distribution of stiffness variations along the length of the ski
MEASUREMENTS
The main measurements to be concerned with include tip (shovel) width, waist width, tail width, ski length, taper, and turn radius. Tip, waist, and tail measurements are usually expressed as tip/waist/tail in millimeters (i.e. 120/87/113). Length is usually expressed in centimeters. However, length numbers can be tricky – some manufacturers measure the actual total ski length (along the bottom bends), some measure cord length (the straight-line measurement from tip to tail), and some measure running length (from contact point to contact point). Taper is the difference between the tip width and tail width. Turn radius (sidecut) is determined by other the measurements and describes the radius of the circle the ski would make based on the difference in its tip/waist/tail and length dimensions only and is expressed in meters.
TAIL SHAPE
Ski tails are generally made in 4 shapes: flat and wide (square), flat and rounded, partial twin-tip, and true twin-tip.
The way a ski “feels” or behaves depends on the combination of its measurements, the materials used in its construction, and its construction methods. This means that 3 skis with the exact same dimensions could still feel significantly different depending on their construction. Fortunately, some generalizations of behavior can be made when it comes to measurements, materials, and construction methods, but first we’ll examine the basics of construction, stiffness, measurements, and tail shape.
CONSTRUCTION
The main parts of a ski: Base, edges, sidewall (part of the topsheet in this picture), core and filler material, and top sheet. Here is a simplified picture:
In modern skis, the base material is a clear, black or colored plastic material called P-Tex. The topsheet and sidewalls are typically a plastic called ABS, but could also be wood or stainless steel. The core materials usually used include foam, wood, Kevlar, carbon, fiberglass, epoxy, rubber, and metal (stainless steel, aluminum, magnesium or titanium).
There are 3 widely used construction methods: Torsion box, laminate, and “cap” or monocoque construction.
- Torsion box construction entails a core of foam or wood wrapped with varying materials:
- Laminate construction entails layers of materials pressed together using epoxy under heat and pressure. This method is the easiest because it does not require molds for each size ski. However, it is subject to the layers coming apart under rough usage (delamination).
- Cap construction entails a topsheet that is molded to form both the topsheet and sidewalls in one piece. Thus the sidewalls become an actual part of the weight-bearing structure.
STIFFNESS
There are 3 key components to consider when examining ski stiffness. All three are at least partially determined by the type and location of material used in the core, the construction method used, and the number and location of metal layers in the ski. Overall stiffness is the general stiffness along the length of the ski. Torsional rigidity is the stiffness across the width of the ski, or amount of twist when edged. Flex pattern is the distribution of stiffness variations along the length of the ski
MEASUREMENTS
The main measurements to be concerned with include tip (shovel) width, waist width, tail width, ski length, taper, and turn radius. Tip, waist, and tail measurements are usually expressed as tip/waist/tail in millimeters (i.e. 120/87/113). Length is usually expressed in centimeters. However, length numbers can be tricky – some manufacturers measure the actual total ski length (along the bottom bends), some measure cord length (the straight-line measurement from tip to tail), and some measure running length (from contact point to contact point). Taper is the difference between the tip width and tail width. Turn radius (sidecut) is determined by other the measurements and describes the radius of the circle the ski would make based on the difference in its tip/waist/tail and length dimensions only and is expressed in meters.
TAIL SHAPE
Ski tails are generally made in 4 shapes: flat and wide (square), flat and rounded, partial twin-tip, and true twin-tip.
OK, SO HOW DOES ALL THIS AFFECT ME????
Here’s where the generalizations regarding ski construction and behavior come in. Keep in mind, these are generalizations only and the actual behavior or feel of a ski is determined by the combination of ALL of these components!!- Wood core vs. foam core: wood core will be heavier, more stable, and more damp.
- Metal layers in ski: each metal layer will make the ski heavier, more stable, and more damp.
- Construction methods: torsion box is most durable; cap is usually lightest (except Volant skis).
- Stiffness: the stiffer a ski is, the more it will like high speeds, but the harder it will be drive into a turn and the more demanding it will be.
- Torsional rigidity: the more rigid the ski is the better grip it will have on ice and steeps, and the more demanding it will be.
- Flex pattern: a softer tip will help the ski roll into the turn. A stiffer tail will have power coming out of the turn. A “balanced” or even flex pattern will move equally into and out of a turn.
- Waist width: wider skis float better in powder and crud but suffer on the groomed stuff. Most East coast and Midwest skiers will be best served by Carvers (60-70mm) or Midfats (70-87mm) for their main ski. West coasters could also consider Fat skis (80+ mm) because of their softer snow conditions.
- Taper: the greater the taper, the more the ski will want to roll into the turn and the easier it will release the turn. The less taper it has, the more float it will have in powder and crud.
- Sidecut: the higher the turn radius number, the larger the turn the ski will comfortably make and the more stable it will be at high speeds. The smaller the number, the more it will want to turn and the more nervous it will be at speed. East coast and Midwest skiers are best served by turn radii around 14-20 meters for versatility while West coasters can look for radii of 18 meters or larger. Slalom skis are typically 12-14 meters, GS skis are typically 18-25 meters, and Big Mountain skis are typically 20+ meters.
- Tail shape: square tails hold the turn longest. Rounded tails and twin-tips release the turn more easily. True twin-tips are designed so the ski will ride equally well forwards or backwards (switch or fakey).
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