Originally Posted by ydnar
Ever wonder just how much energy is stored in a flexed ski. Here's a way to see.
Take two sawhorses and place a ski between them. Put a light object such as a five inch length of 2x4 on the ski. De-camber the ski by pulling it down with your hand. Release the ski and see how far the piece of 2x4 is thrown into the air. A foot? Maybe two feet? If the ski can only move a few ounces of wood a foot or two how is the poor weak thing supposed to supply enough force to move my fat old mans body around?
Methinks that the sensation of pop/rebound/whatever must come from some other source,
I've often pondered the dilemma you bring up.
Clearly, the rebound can throw my skis over my head if mismanaged. But is that rebound coming from the ski, or the boot, or what?
I tend to think the following. I may be utterly wrong:
-Your sawhorse test will exacerbate the flex of the ski at its softest regions, the tip and tail. Less springrate, so to speak.
-When you make a good SL turn on a good ski, the ski takes on a solid and uniterrupted bend all throughout, including the beefy underfoot region. I believe that
region, with its springrate perhaps an order of magnitude greater than the tip or tail, will create much more rebound than your sawhorse demo shows.
-Keep in mind that there is a binding and boot on top of that region, further increasing its resistance to flex, and perhaps the amount of energy stored by the flexing bootsole (Yes, your bootsole flexes) and binding mounting plates.
-High end skiboots also have rebound. That means that not only do they resist forward flex, they store "rebound energy" through plastic that deforms elastically and is somehow springy. Low end ski boot shells stretch, but have no desire to return to their original shape.