It is well known that increasing edge angle of a ski or snowboard will increase the grip of the device on the snow (assuming proper platform angle). It is also known that with “shaped” skis/snowboards the effective radius is given by measured side cut radius multiplied by the cosine of the edge angle (this is a rough calculation, and we will talk about supplements and limitations to this). What this means is less intuitive unless you get out a calculator and increase the edge angle drastically. To avoid this confusion and make this both easier to understand and apply on the snow, lets take a look at the graph of the multiplier vs the edge angle:
As you can see, at 90 degrees the multiplier becomes zero, so obviously there is a cut off to how much the ski will actually bend! You will also boot out before you get anywhere close to this edge angle! But the main thing to note is the non linearity of the curve. That is, the more you tip the skis or snowboard over, the more drastically the effective radius reduces!
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Degree of Edge Angle
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Percent of Side Cut Radius
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1
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99.98%
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10
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98.48%
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20
|
93.97%
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30
|
86.60%
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40
|
76.60%
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50
|
64.28%
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60
|
50.00%
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70
|
34.20%
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|
80
|
17.36%
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As you can see, the reduction in radius becomes most pronounced above 30-40 degrees. This is perhaps why this law of ski and ride is little known and explored. Is tipping a ski on edge to these extremes practical? In racing the answer is undoubtedly YES! Ted Ligety and Mikaela Shiffrin are great US Ski Team examples of this, and almost all racers achieve these aggressive edge angles to help them carve tighter turns, and gain better edge engagement with the icy race courses.
What about the applications for the mere mortals out on the slopes? Is this practical? Perhaps it is not, but it certainly is fun! When a ski is tipped to extremes, about 40 degrees, the sensations of the turning forces becomes extremely fun and the grip of the ski is also enhanced (assuming again, that we maintain a platform angle that allows for gripping).
For people who are athletic, the ability to tip the ski to a degree greater than 30 degrees offers a superior ski performance. My current ski has a 13.5 meter radius (Head Rev 75 2015 Model Year). Tipped on edge to 30 degrees this ski carves roughly an 11.69 meters arc (86.6*13.5), just 10 degrees more of tipping to 40 degrees give me an effective radius of 10.34 meters. These naturally do not sound like huge reductions until we get to 60 degrees or a 50% reduction in the effective side cut. At 60 degrees our 13.5 meter ski is effectively carving a 6.75 meter arc! What FUN!
Above 45 degrees of edge angle things happen fast! Your skis are now carving a much tighter arc which increases the forces created by the turn (Velocity*Velocity divided by radius creates the outward acceleration of the turn).
Physics of the ski above 45 degrees are also very different. The body motions which normally achieve fore aft pressure as we know them, start to translate into rotational forces on the skis (changing the direction the ski is actually pointed). Leg rotation can start to alter the fore aft pressure along the slicing edges of the skis above 45 degrees of edge angle. This may sound misinformed until you give it a try! Just keep in mind that these skills blend depending on the edge angle.
Lets talk about things that allow the ski to decamber (bend into an arc, think opposite direction of camber) to these degrees when tipped up on edge. First the skier/rider should have good fore aft balance. This is important to ensure that the contact across the entire length of the ski is maintained. When skiing softer conditions like powder the ski will achieve higher decambering due to the body pushing through the center of the ski more than the tips and tails (which are bent upward by the powder). This will push the center of the ski down into the snow, which will decamber it naturally.
So we have talked about ‘bending’ the skis. Obviously you have to push on the skis to bend them, but pick up a ski and push through the binding. This literally takes maybe 20 pounds of force… which is not a lot of force to expend onto the skis. Keep in mind that when skiing a turn, you actually gain or lose the forces of the turn, so your forces exerted through the skis may be greater or less than your actual weight.
The main points of this talk are that, the relationship of the edge angle to radius reduction is not linear, but the effective radius decays more exponentially. Get out and play with tipping your edges to a higher degree if you feel competent and comfortable. Just be careful, this is very advanced skiing and carving, and can be very dangerous if done incorrectly. Thank you