ski shape and binding placement

[uni412]

I've been thinking alot lately about the placement of bindings in relation to the tip and tail widths of a ski. Here are my thoughts:

1. The binding (or actually the ball of the foot) should be placed above the narrowest part of the ski because this is the part of the ski that is pushed down the most when carving and should therefore have direct pressure applied to it.

2. If the sidecut curvature of a ski is the arc of a circle, the width of the tip and tail should determine where the narrowist part of the ski is located. If the tip and tail are the same width then the narrowest part of the ski should be in the exact middle of the ski. However, if the tail is narrower than the tip, the narrowest part of the ski should be closer to the tail than the tip. (Therefore the binding should be placed more back on the ski).
This diagram shows what I mean: the shaded area between the two curves is the ski and the tip is much much wider than the tail.


So I have 2 questions. Is my reasoning correct? and, Why does almost every ski have a narrower tail than tip and therefore a binding mounted rear of the middle of the ski.

Thanks
Uni412

[East_Coast_Style]

think of a ski as a car. driving a car forward, its very stable. thats because the turning forces are initiated from the front. drive a car backwards at 30 mph, what happens? it wants to spin around, cause the turns are initiated from the rear. skis are the same way. and, most skis are not radial sidecuts, as that is a fairly outdated design. radial sidecuts have a tendency to wanna kick back uphill and not release from turns, which is why you see very often skis with steeper sidecuts in the nose, and narrower, more drawn out tails. the idea is to shift more of the turning forces to the nose of the ski, and let the tail just follow through, exactly like a car. this increases stability, skiability, blah blah blah. as for the mounting location, the mounting point on a ski should be at the narrowest part, or the center of the skis sidecut (same thing), and at midsole. that centers your weight directly over the control center of the ski. it allows your toes and forefoot to pivot the nose, and heel to control the tail. if you forward mount (like on alot of non symetrical twin tips), in order to ski the ski, you end up riding more in the backseat. if you were to mount farther behind midsole, you wouldnt be able to apply proper pressure to the ski, and would be way forward. now granted, moving the mount a inch or two on most skis is fine, and thats how alot of companies design womens skis, to adjust for thier center of gravity, but for the most part, center-arc is the ideal place to mount at.

[uni412]

Thanks alot for the info. So when designing a ski you should adjust the curvature of the sidecut so that the narrowest part of the ski is in the middle (lengthwise) of the ski?

As a side note, how is the sidecut radius measured on skis without radial sidecut?

Thanks again,
Uni412

[Cadman]

As a general rule of thumb, the ball of the foot goes at the mid running surface (MRS) and the center line of the boot goes to the waist so for general design guidlines, The waist is usually back about 2.5-2.75 inches
since that is the distance from the ball of the foot to the center line on a size 27.5 size boot which is the average foot size. Remember this is
a guidline only. Park skis are mounted differently so the the rules go out the door here.
The MRS being the mid point between where the tip and tail start to turn up.