HANDLE TIPPING VS. HEEL-1ST MT LOAD INDUCED TIPPING


As a prelude to discussing the mechanics and biomechanics of tipping a ski on edge with the weight on the heel and the leg clamped tightly to the shaft of the boot where it is used like a handle to tip a ski on edge vs. heel – 1st MT load induced tipping, I have created a model of a shape ski about 16 cm in length by 8 mm in minimum profile wide (waist) with which to illustrate the differences. The model has a vertical handle in the center that I will use in a video to tip the ski model on edge with center only loading (heel) and center (heel) inside edge (1st MT) loading.

The model of the shape ski is made of polyethylene. It has a curve along its length to simulate camber. The black line shows the transverse center of the ski. The center area across the waist is stiffened with a plastic rib which serves as the mount for the vertical handle. Here are 3 photos of the shape ski model.

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The camber is evident in this photo.

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The sketch below shows the different aspects of the shape ski model. It is easy to make with readily available materials.

Shape Ski Model

Here’s a video that illustrates the problems of trying to tip a ski on edge using the leg as a lever and the boot shaft as a handle when the weight is under the heel of the outside foot in a turn. At initiation of a new turn, the skier must move into the new turn, away from the outside ski, in order to release the load on the ski. When the heel and 1st metatarsal are loaded across the bridge formed by the longitudinal arch, the ski will tip on edge as the load on the 1st MT progressively increases and the load on the heel progressively decreases.

In my next post, I will discuss the mechanics and biomechanics of heel pressure only ski loading vs. heel-1st metatarsal pressure differential ski loading and the effect of high pressure 1st metatarsal COP on edge engagement.

 

2 comments

  1. This is a great demonstration.
    I think it is possible to get a similar feel for the forces involved across the ski using a bent paperclip as the ski model for those with less DIY abilities though it doesnt show the reverse camber effect.

    1. Thanks for confirming that Mike. The actual mechanism is quite complex. But as Einstein says, if you can’t make something simple, you don’t understand it well enough. I have understood the basic mechanism since about 1988. But I readily concede that it can be challenging teaching it to skiers and racers. I was hoping a simple model would communicate the basic mechanism and spur interest in understanding how to apply it. Once a skier learns the mechanism, it is an intoxication feeling to stand on the outside ski, load the first metatarsal, feel the edges engage and the shovel lock up and pull the ski into a turn with little physical effort on the part of the skier.

      Please keep your comments coming as I try to go forward with this issue.

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