nik · January 21, 2021 17:27
diff --git a/ski_science.txt b/ski_science.txt
 there are a lot of factors in ski shape that affect how a ski behaves. The main ones I can run through. Saying that there is only one or two factors that explain the ski's characteristics is wildly off-base and its really a combination of a lot of things, leading it to be difficult to pin down.

 Width - a wider ski has a lower torsional rigidity, meaning a lot of the force that goes into the ski does not correspond to a direct transfer of energy pushing you in the opposite direction; instead, much of it goes into generating a torsional force which bends the ski laterally. This is a waste of energy as you're putting your valuable kinetic energy into deforming a ski laterally (which provides no performance). The skis are also harder to get on edge, and slower from one edge to the other just as a function of the larger force required to transition from one edge to the other. Skiing wider on firmer snow can also place your knees in more compromising positions, as you're potentially closer to the limits of your ROM and compensating for the additional torsional forces due to having a larger distance between the (lateral) centre of your boot and the contact point with the snow (as previously discussed).

 Rocker - Rocker affects the running length of a ski. It is essentially the early rise of a ski. Most skis are cambered with rocker at the tips and tails which means they're bent concavely underfoot and transition at a certain point in front and behind the bindings into a convex shape. The more rocker you have, the less of the edge you're actively able to load and therefore use in a carve. The less edge you have, the faster you reach the load limit of the snow you're on and the easier you skid. Due to the dynamics of carving, minimal tail rocker helps keep the turn engaged in a carve for the full length of the turn whereas increasing tail rocker reduces the ability of a ski to remain locked into that arc, and increases propensity to skid. This characteristic is obviously favourable in a lot of softer snow-focussed skis, and honestly is one of the biggest determinants of how a ski will feel.

 Taper - The widest point of a ski also defines the effective edge length of the ski; taper describes how early before the end of the ski's full length that the widest point of the ski is. If you look at race skis their widest point is directly before the end of the ski, for obvious reasons. The more taper you have, the more "vague" your turn initiation becomes: think about it as a less sharp knife, vs a more sharp knife - the angle of incision becomes smaller with more taper as a vague analogy

 Mount point - The position along the ski at which your bindings are placed. When you engage a turn, you're using the pressure on the front of the skis to bend them, as you lean onto edge, which generates an arc. Skis mounted more rearwards allow you to provide more forward pressure, which bends the ski more easily, and you can apply more force *forwards* such that even if you are pushed back, you still remain forwards. On a more centrally mounted ski, if you receive something that pushes you back a bit, you are already pressuring the front of the ski *less* so you are pushed backwards more.

 Example:

 Rearward mount, -12cm. Forward force = 400N -> hit a bump -> backwards force = 200N, so Net force = 200N still bending shovels and leaning forwards

 Forward mount, -4cm. Forward force = 250N -> hit a bump -> backwards force = 200N, so Net force = 50N.

 This argument is also applicable to why stiff boots offer more control over one's boots; more potential energy stored in the boot, harder it is to return the skier to equilibrium position, more stable you are.

 The more forward your skis are mounted, the easier they are to "pivot" as well. This is because in a rearwardly mounted ski you have an offset axis of rotation. In a more centrally mounted ski, this issue is less of a problem. The increased pivot-y character tends to want to release from a carve more easily, meaning you'll end up skidding more. This probably isn't even a comprehensive explanation of the effects of mount point; its effects are extensive, and the fundamental aspect of a ski design that will suit you.

 Splay: often overlooked, tip splay matters a lot once you go to wider skis. Lay the skis flat on the ground and measure the distance from the floor to the tip (and tail) vertically - that's the splay. The splay affects the feeling you'll have on ice and powder especially. More splay = a lot more float, but much less performance on ice. Matters more for tail than tip. That said, you see a large amount of variation in both. The physical reason here is that the more splay that there is, the earlier on the ski the rocker reaches the point at which it is not part of the effective edge closer to the bindings (hence less effective edge).

 Sidecut: A tighter sidecut will carve more easily on hard snow. I'm not sure the physical reason here sorry. If I had to speculate, then I'd say you're going to have a more intuitive feeling as the turn initiation is going to be sharper leading to a more defined turn start and end. Less riding edges, much more active.

 Weight: A heavier ski is going to perform better on ice. It will be better at damping vibrations and keep the full length of the ski running along the surface continually. A light ski won't always be in contact with the snow as consistently.
	there are a lot of factors in ski shape that affect how a ski behaves. The main ones I can run through. Saying that there is only one or two factors that explain the ski's characteristics is wildly off-base and its really a combination of a lot of things, leading it to be difficult to pin down.

	Width - a wider ski has a lower torsional rigidity, meaning a lot of the force that goes into the ski does not correspond to a direct transfer of energy pushing you in the opposite direction; instead, much of it goes into generating a torsional force which bends the ski laterally. This is a waste of energy as you're putting your valuable kinetic energy into deforming a ski laterally (which provides no performance). The skis are also harder to get on edge, and slower from one edge to the other just as a function of the larger force required to transition from one edge to the other. Skiing wider on firmer snow can also place your knees in more compromising positions, as you're potentially closer to the limits of your ROM and compensating for the additional torsional forces due to having a larger distance between the (lateral) centre of your boot and the contact point with the snow (as previously discussed).

	Rocker - Rocker affects the running length of a ski. It is essentially the early rise of a ski. Most skis are cambered with rocker at the tips and tails which means they're bent concavely underfoot and transition at a certain point in front and behind the bindings into a convex shape. The more rocker you have, the less of the edge you're actively able to load and therefore use in a carve. The less edge you have, the faster you reach the load limit of the snow you're on and the easier you skid. Due to the dynamics of carving, minimal tail rocker helps keep the turn engaged in a carve for the full length of the turn whereas increasing tail rocker reduces the ability of a ski to remain locked into that arc, and increases propensity to skid. This characteristic is obviously favourable in a lot of softer snow-focussed skis, and honestly is one of the biggest determinants of how a ski will feel.

	Taper - The widest point of a ski also defines the effective edge length of the ski; taper describes how early before the end of the ski's full length that the widest point of the ski is. If you look at race skis their widest point is directly before the end of the ski, for obvious reasons. The more taper you have, the more "vague" your turn initiation becomes: think about it as a less sharp knife, vs a more sharp knife - the angle of incision becomes smaller with more taper as a vague analogy

	Mount point - The position along the ski at which your bindings are placed. When you engage a turn, you're using the pressure on the front of the skis to bend them, as you lean onto edge, which generates an arc. Skis mounted more rearwards allow you to provide more forward pressure, which bends the ski more easily, and you can apply more force forwards such that even if you are pushed back, you still remain forwards. On a more centrally mounted ski, if you receive something that pushes you back a bit, you are already pressuring the front of the ski less so you are pushed backwards more.

	Example:

	Rearward mount, -12cm. Forward force = 400N -> hit a bump -> backwards force = 200N, so Net force = 200N still bending shovels and leaning forwards

	Forward mount, -4cm. Forward force = 250N -> hit a bump -> backwards force = 200N, so Net force = 50N.

	This argument is also applicable to why stiff boots offer more control over one's boots; more potential energy stored in the boot, harder it is to return the skier to equilibrium position, more stable you are.

	The more forward your skis are mounted, the easier they are to "pivot" as well. This is because in a rearwardly mounted ski you have an offset axis of rotation. In a more centrally mounted ski, this issue is less of a problem. The increased pivot-y character tends to want to release from a carve more easily, meaning you'll end up skidding more. This probably isn't even a comprehensive explanation of the effects of mount point; its effects are extensive, and the fundamental aspect of a ski design that will suit you.

	Splay: often overlooked, tip splay matters a lot once you go to wider skis. Lay the skis flat on the ground and measure the distance from the floor to the tip (and tail) vertically - that's the splay. The splay affects the feeling you'll have on ice and powder especially. More splay = a lot more float, but much less performance on ice. Matters more for tail than tip. That said, you see a large amount of variation in both. The physical reason here is that the more splay that there is, the earlier on the ski the rocker reaches the point at which it is not part of the effective edge closer to the bindings (hence less effective edge).

	Sidecut: A tighter sidecut will carve more easily on hard snow. I'm not sure the physical reason here sorry. If I had to speculate, then I'd say you're going to have a more intuitive feeling as the turn initiation is going to be sharper leading to a more defined turn start and end. Less riding edges, much more active.

	Weight: A heavier ski is going to perform better on ice. It will be better at damping vibrations and keep the full length of the ski running along the surface continually. A light ski won't always be in contact with the snow as consistently.