technique vs skate stiffness

[YesLanges 127]

Regarding "facts" vs. "beliefs" and chosen language for expressing one or the other:

Chad, there's a huge difference between someone simply saying that he has a hard time believing something or that something doesn't seem right to him and someone pronouncing a firm position and proclaiming that someone else is wrong without facts to prove his point. If the person is doing the latter, it might be perfectly appropriate to tell him to "make your point with facts not beliefs." But if the person is merely doing the former and not purporting to know the answer or to tell anybody else that he's wrong, the same response is just unnecessary, and frankly, obnoxious.

I wasn't making a point; I explained politely why I was having a hard time accepting your answer and I posed the thought experiment that bothered me about it. Your tone is only appropriate for someone expressing belief as fact; it's not appropriate for someone expressing a belief as a belief or polite disbelief of your position and posing the thought experiment that bothers him about your answer. You don't have to address my question about the relative hardness of the surface being relevant in relation to the length of the cut left by blades of different sizes if you don't want to; but I need your help with rhetorical argument about as much as you need my help sharpening skates.

[GreatestAmericanBeardo 258]

here my two cents to add fuel to the fire :)

“The larger the radius, the greater amount of blade goes on the ice, Your body weight puts friction on the ice, creating a film of water that is a lubricant. The greater amount of lubricant the faster you go. So speed skaters, with the most blade on the ice, go fastest, but hockey players and figure skaters can maneuver better.

-George Knakal

http://www.nytimes.com/2009/06/23/science/23SharpW.html?_r=0

[YesLanges 127]

To me, it's not a fire and shouldn't even be an argument: it's just a discussion among people with different views and without any need for rudeness or condescension by anybody.

I think everybody's in agreement that larger radii put more blade on the ice if all the other variables are the same. The main disagreement is whether the overall length of the blade puts different amounts of blade on the ice when the radius of each is the same. Chad (and others) suggest that blades of different length put equal amounts of steel on the ice at any time as blades of different length as long as the radius is the same. That doesn't seem right to me for the following reason:

My intuitive belief is that a longer blade puts more steel on the ice even when the radius is the same as a shorter blade for the exact reason you articulated. Ice is soft so the blade doesn't just touch the ice at a specific point the way lines tangent to a curve or a circle do on paper. On a perfectly (or relatively) hard surface, only the actual flat of the blade touches the surface; but when you have the weight of a skater pushing the blade down into a soft (or relatively softer) surface like ice, more of the blade sinks into the ice than just the flat. I believe this is true even when the weight of the skater is the same. You could simplify it even further by imagining a heavier weight and a lighter weight pushing down on the exact same blade: I'd expect the heavier skater to sink more steel into the ice than a lighter skater even when they're wearing the same exact blade.

The thought experiment I'm using is perfectly doable: Place the same amount of weight onto two different blades of the same radius and measure the cut each blade leaves in the ice. I'd expect that the outcome of that experiment would be a longer cut under the longer blade. Furthermore, if that were to be tested by engineers, I'd expect that they'd use the weight of the skater in proportion to the blade length to express the formula for determining how much blade touches the ice for ice of a given hardness. I'd also expect them to include the radius as a variable but that the radius variable would be nearly negligible compared to importance of the blade-length variable, especially for radii that are relatively similar (such as 7' and 9' vs. radii that are double or triple one another) I don't have any "facts" to support my expectation and I'm not suggesting that I'm right or that anybody who disagrees with me is wrong. This is just a very testable hypothesis of what seems to make the most sense to me thinking about it, trying to visualize it, and participating in what should be a civil conversation.

[Hockeydog 8]

I think a 9 ft radius puts the same amount of blade on the ice no matter how long the blade is - but only when cenetered on the flat of the blade. It would seem to me that when we lean the boot over and redistribute weight either front or back ( like a powerturn where the skate is leaned over and weight is mid to back of blade) more of the blade touchs the ice. We are sinking in because we throw snow and leave carve marks. So my guess is the radius is just a baseline or neutral psoition.

[chk hrd 164]

Take a circular object, it doesn't matter what size. Place your fingers at opposite sides about an inch from the bottom and see how much touches a flat surface. Now move your fingers halfway up to widen the space between them. The amount of contact on the flat surface is the same. Fingers close together are small blades, fingers farther apart are longer blades. Same radius, same surface area contact, even if leaned sideways, forwards or backwards. The only way you would have more contact with the same size circle is if the surface was soft enough to make weight applied to it a factor. The ice we skate on is pretty hard so the bite into it would be minimal. If you want more/less blade contact then you have to alter the radius. A larger radius is more blade contact, smaller radius is less.

[Chadd 916]

Let's look at an image that was posted here six years ago..

Now put the exact same profile on another skate, one size larger or smaller, it doesn't matter which. Now, bear in mind that the difference from one size to the next is 8mm or so. Only four of that will be forward of the center of your skate and entirely at the toe. How does making the toe 4mm longer, put more steel on the ice? How deep do you need to sink into the ice for the difference of 4mm at the toe or 4mm at the heel to add more steel on (or in) the ice?

As to sinking into the ice, some believe that you actually skate on a thin film of water and not actually in the ice. Others disagree, but I don't have time to dig up the more recent discussions of the physics. However, if you truly were sinking deep into the ice, you wouldn't be sending a shower of fine snow flakes into the air when you stop. There would be major chunks of ice being gouged each and every time you stopped, turned or dug in hard to accelerate, even if you were only sinking a couple mm into the ice. As you can see from the profile above, or on your own skates, you would likely need to be 1/4" or more into the ice before the last few mm would make any difference in terms of your amount of steel in contact with the ice.

[Hockeydog 8]

That is a very good post Chadd, and it certainly clears it up for me. I come here to learn, so thank you for that !