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What's essential for carving on hard snow?

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skier

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Ok, I've dug up some more info. Rather than bother with all the references, I'll just explain it, and then let the "opposition party" fact check it and correct where relevant.

The sidecut of a ski traces out an oval. In order for a ski to carve perfectly, it must trace out a circle. When the ski is bent just the right amount, it traces out a circle. So, a ski with a given sidecut has one radius, Rsc, where it will trace out a perfect circle and thus one edge angle for "perfect" carving. A ski with a small radius will perfectly carve small circles, but not large circles. A ski with a large turning radius will perfectly carve large circles, but not small circles. Modern skis have a small turning radius, so they carve small circles well, but not large circles. They will skid for large circles. At the top of the turn, carving arc to arc, the turning radius is large, so the ski will skid, until the turning radius is tightened to match Rsc. Ironically, older style skis with a larger turning radius will carve more cleanly at the top of the turn, but will not carve as cleanly for tighter turns.

Peace.
 

markojp

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Please, please, oh please talk about centripetal/centrifugal forces/force vectors in relation to all of this.... Skier, have you mentioned this in any of your posts? You may well have... I saw Razie brought it up for a moment, but I just don't have the time, energy, or patience to go through 11 pages. I'm much more looking forward to actually skiing with the kiddo tomorrow.
:golfclap:
 
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François Pugh

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You bring up a very interesting point. A ski with a 13 m radius on hardpack will not carve a 30 m radius curve. However it will splice 13 m turns together just fine, with the splice being skis flat.

To illustrate consider skiing a pair of 13 m so skis.

As a start, consider a series of half circle arcs joined together. Where the circles meet, the radius can be considered as 13 m radius turn to the right, or 13 m radius turn to the left. At transition, you may consider the turn radius as 13 m right, 13 m left or infinity since skis are going straight.

Now consider what happens when you increase, then decrease the tipping angle though-out the turn. At transition, given a carving intent an according technique, a 13 m radius turn is begun. The turn tightens to an apex and then widens back to a 13 m turn, with skis flat at the next transition. This is done using proper body position management, with separation of paths of centre of mass and skis, being sure not to overload the skis at transition.

OR you can start your turn by trying to make your 13 m skis carve a 30 m (or any turn larger than 13 m) turn and gradually decreasing the turn size. If you do that, your skis will skid at the start of the turn (and continue skidding until you reach the critical angle).

Your choice. It's fun to have fun, but you have to know how.
 

CalG

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Ok, I've dug up some more info. Rather than bother with all the references, I'll just explain it, and then let the "opposition party" fact check it and correct where relevant.

The sidecut of a ski traces out an oval. In order for a ski to carve perfectly, it must trace out a circle. When the ski is bent just the right amount, it traces out a circle. So, a ski with a given sidecut has one radius, Rsc, where it will trace out a perfect circle and thus one edge angle for "perfect" carving. A ski with a small radius will perfectly carve small circles, but not large circles. A ski with a large turning radius will perfectly carve large circles, but not small circles. Modern skis have a small turning radius, so they carve small circles well, but not large circles. They will skid for large circles. At the top of the turn, carving arc to arc, the turning radius is large, so the ski will skid, until the turning radius is tightened to match Rsc. Ironically, older style skis with a larger turning radius will carve more cleanly at the top of the turn, but will not carve as cleanly for tighter turns.

Peace.

How much is "bent just the right amount ", and how would one know? (by the traces left in the snow?)

And

Why must turns need be circular curves? I rather enjoy asymptotes.
 

CalG

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You bring up a very interesting point. A ski with a 13 m radius on hardpack will not carve a 30 m radius curve. However it will splice 13 m turns together just fine, with the splice being skis flat.

To illustrate consider skiing a pair of 13 m so skis.

As a start, consider a series of half circle arcs joined together. Where the circles meet, the radius can be considered as 13 m radius turn to the right, or 13 m radius turn to the left. At transition, you may consider the turn radius as 13 m right, 13 m left or infinity since skis are going straight.

Now consider what happens when you increase, then decrease the tipping angle though-out the turn. At transition, given a carving intent an according technique, a 13 m radius turn is begun. The turn tightens to an apex and then widens back to a 13 m turn, with skis flat at the next transition. This is done using proper body position management, with separation of paths of centre of mass and skis, being sure not to overload the skis at transition.

OR you can start your turn by trying to make your 13 m skis carve a 30 m (or any turn larger than 13 m) turn and gradually decreasing the turn size. If you do that, your skis will skid at the start of the turn (and continue skidding until you reach the critical angle).

Your choice. It's fun to have fun, but you have to know how.

BS!
13M at what bend?

Case in point, Thursday morning the mountain was covered with 3-4 inches of a snow/ sleet mix ( bonded over sheet ice)
The surface skied sublimely! BUT, the tips of my skis (Volkl RTM) near to damnit would strike me in the ear when pressing a hard turn, if I had let them.

Sharp carving curves without a hint of sliding. Tracks to prove were obvious on the chair back up Go figure
 

John J

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Um... yeah a ski with a 13m radius will carve a 30m radius. Conversely, a ski with a 13m radius will also carve an 8m radius, or there about. Ultimately, it comes down to boot pressure. The more you drive your outside knee into your toe of the same ski, the tighter you can make your turn. Reverse camber. This assumes the skier is comfortable and proficient with keeping their hips over their feet at any given part of the turn. Ya gots ta be forward. That means having properly fitted boots, and having the upper part of your boots buckled tight enough to support your weight when leaning forward in order to get your hips over your feet. The front of the boot should act as a lever to push your heel into the heel cup. To me this forwardness creates center balance... (This also means straight upper body and head up, no hunching) equal weight on the heel and ball of the foot. Line choice becomes whatever you want it to be. If you still feel your calf against the back of your boot, you're in the back seat and you need to slow it down and figure out how to stay against the front of your boots. The front of your boots is your friend. Fore/Aft balance is a critical component of skiing. Aft balance is fine after the apex of the turn when centrifugal force pushes you in the back seat... but, you must, must, must be able to bring your COM (hips over feet) to start your next turn with any type of consistency. You can get away with skiing in the back seat on most easy green runs, but as soon as the terrain or pitch or snow conditions become more difficult, you will struggle.

Enough rambling. Go back and read LF's post 192. I'd listen to her any day of the week and twice on Sunday. If you happen to be losing outside ski pressure, your turns are probably not as round or snappy as you'd like them while carving. 1 or 2 things might be happening. 1, You are banking your turns... too much weight on the inside ski, because you didn't create enough lateral balance over the outside ski to create a platform to balance on. 2, you may be a little in the back seat without realizing it which will cause your turn to be straighter or not as round as you'd like and you may feel a bit out of control. Been there, done that and have 2 closets and 1 dresser full of T-shirts to prove all of my past bad habits and what a horrible skier I can be. Of all the things there are to learn to be an OK skier, keeping your hips over your feet is the hardest thing to become comfortable with. This is a carving thread, but it doesn't matter if you're carving or steering... master keeping your hips over your feet and those shins against the front of your boots. Try skiing switch... this is a great exercise to figure out how to stay against the front of your boots... it will actually improve your forward skiing. If you've read this far and are curious about learning to ski switch... check out www.skiguru.tv
That's the simplest best breakdown I've seen, and how I learned how to ski switch. Take the leap.
 

geepers

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Jurij Franko says the sidecut is based on the top of the sine curve - have a listen to his interview with Tom Gellie at 13:00.

Shortly after that he adds:
"...that for every single radius of skiing and for every different angulation there's a different shape of side cut. That's in theory. In practice you cannot produce skis inside those tolerances."​

Elsewhere (on FB) he's posted:
So, for everybody interested, here is equation of sidecut:
α – angualtion angle (0- flat on the ground)
x – width of the ski at centerpoint
w – width of the ski
l – distance from centerpoint of the ski to the point on the edge of the ski
r – radius of a turn

w=x+ 2(2r sin⁡(α) sin⁡(l/2πr))​

I've no idea if that applies only to the Elan skis he designed and if that's changed by other manufacturers or in more recent times.

No doubt, regardless of the actual side cut equation, there's some piece of snow that satisfies the appropriate ISO standard for smoothness, uniformity of snow sheer strength and diamond like hardness where the manufacturer's rigid adherence to 6 sigma quality makes a difference.


 

razie

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Ski radius is a state of mind... or rather, a result of skill. It would be great to stop talking about skiing on a theoretical level and just go out and ski...

This is a stiff GS ski, with a 18m sidecut radius printed on it, skied on hardpack, on a green run - the turns look cleanly carved 100% and have about 11-12m radius with a 3m offset - that's almost a WC SL turn, by the looks of it:


Once you have the technique to get this from it, the discussion will change... ;)
 

skier

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I probably didn't explain it very well, so I found someone that I think does a much better job. Enjoy.

https://www.real-world-physics-problems.com/physics-of-skiing.html

No need for anyone to get pissy. If you're not interested, then just stop replying, and the conversation will die very quickly, which could be a win for all of us. Forums like this are much better served if it's limited to telling people how to tip when they ask for skiing advice and what ski to buy (over and over and over again). We'll leave the complicated stuff for when the military gets involved, like Geepers quoted :).
 

François Pugh

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Ok. Fully admit this is an approximation, but it's the best approximation we have. The lowest tipping angle we can have is 0 degrees. To turn, we need to tip the skis. At 0 degrees the best fit circular arc to the ski's edge is the side cut radius of the ski. As you tip the ski on hardpack the shape of the ski causes the ski to bend when weighted, and the best fit arc to the skis edge becomes smaller, not larger. There is no angle you can tip the ski to that will shape the edge of a 13 m ski to have an 18 m arc. There is some flexibility in the ski and some give to the ski, so the ski can make a clean carve at slightly different radii. You can also force a greater bend into the tips with tip pressure (At the expense of the purity of the carve), but you cannot make a wider turn.
If you think you are carving 30 m turns with your 13 m skis on ice or boiler plate snow, you are likely carving on the straighter underfoot portion of your skis while your ski tips are scraping along, trying to turn sharper. This is not pure arc-2-arc carving. You are not alone; I too thought I could carve gs turns on my sl skis, until I tried those same gs turns on my sg skis. When the whole ski is trying to carve the same turn, it's much smoother.
 

Eleeski

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This thread has been fun. It got me to play with my "unbendable" ski again. It makes me think - both about form on the snow and the engineering of skis in a turn. I might not agree with some of the conclusions but it is entertaining to me.

So I'll add another 2 cents after a long straight reasonably fast icy traverse on very steep Headwall where a carve is required to avoid slipping off a cliff. Large edge angle to the snow. Convex and concave fluctuations of the hill. Occasional obstacles requiring subtle course corrections both slightly uphill and downhill. I made these corrections, not by changing the ski angle or changing the pressure on the skis, but by twisting my lower legs. Rotation was the dominant factor for directional control in that pure carve situation. Pretty tracks regardless of the contour of the traverse or the course corrections.

Certainly a carve is complex and can be made by different techniques.

Sharp edges and reasonably stiff skis do seem to be a necessity for a carved turn. And a specific skillset.

Eric
 

markojp

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I probably didn't explain it very well, so I found someone that I think does a much better job. Enjoy.

https://www.real-world-physics-problems.com/physics-of-skiing.html

No need for anyone to get pissy. If you're not interested, then just stop replying, and the conversation will die very quickly, which could be a win for all of us.

No pissy from me, just a legitimate question from a skier and coach after 11 pages and seeing scant reference to the critical forces mentioned in my post. But I'll refrain. So how many angels fit on the head of a pin? Just enough. Juuuuust enough. Not one too many, not one too few.

:beercheer:
 

Dakine

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Maybe you guys could look at this another way.
In a long thread on Epic we got into a discussion about the properties of snow and how that affects ski dynamics.
Snow can vary from rock hard with a very high elastic modulus to porous and fluffy with no strength to speak of.
Since what is going on with the snow has to be in balance with the applied forces from the ski (of else you crash) the type of snow is one of the most important factors in carving.
Even world cup skiers can't make clean carves on pure ice, it takes ice skates for that.
Hero carving snow has a unique combination of softness and strength and compressibility that allows a ski to first cut into the snow so pressure can be applied as well as being strong enough to not blow out under the forces applied.
If the snow is right, then the ski can be arced and if appropriate edge angles are applied the ski can be flexed to geometric arced shape allowing a long radius ski to make short radius carved turns.
There is a temporal element in all of this.
At the beginning of the turn before the ski has cut into the snow enough to build a platform, very little force can be applied.
As the platform is built, much more force can be applied until the big dogs can put their hip on the snow and get 60 degree edge angles.

Good skiers store and release energy through the turn..
So does the snow.
On Epic, some of us calculated that as much of 30% of the releasable energy in a turn is stored in the snow compressed under the skis.
The snow has to be compressible to store energy and snow that stores energy well is an important element in carved skiing.
That's why you get extra pop from hero snow compared to typical race grade snow.

The pop you get in powder is due to hydrodynamics not elastic recovery.

Like we all know...Think Snow...ogsmile
 

geepers

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It would be great to stop talking about skiing on a theoretical level and just go out and ski...

Well, I'm 12,000km and just under 2 weeks away from being on snow. Not sure what everyone else's excuse is. :P

As far as ski tips for icy conditions maybe this from Fred Lepine is a nice way to round out the discussion.


Prior to the short turns just before before 60 seconds, Fred's turns are predominantly carving although I'm sure those with lynx eyes will be able to spot some non-perfect carving. Those early turns contrast well with the shorts and the later turns where the rotary action is very visible.
 

4ster

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Watch this in slow motion. Damn near perfect skiing on bullet proof ice.


I only read the first few pages back when this thread started a while ago, so I’m probably rehashing.

Sharp, stiff skis.
High edge angles, early.
Get done bending the ski before crossing the fall line.
Use that energy to propel you to the point of beginning of the new turn, above the fall line.
Get the turn done before the vector forces line up & work against you in the bottom of the turn.
Float like a butterfly, sting like a bee.
CCC6D4BF-432C-4333-A98E-D30D602E9607.jpeg


84EF3E6C-32EA-44F1-A8C8-D4D234239F9D.jpeg
 

markojp

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Um... no it won’t. Please review how exactly a ski works to create a carve. Just the basics will suffice.

Interesting flashback when I read your post, HDN. If one does a traverse demo, how is it we can leaving two clean, straight lines on the snow with a ski with sidecut? I remember doing demos for our SSD with training group a few years back on a Head Titan. One person in the group said it would be impossible not to turn on their Experience 88. The SSD more or less said, "watch". Not being rhetorical here at all. Honestly, I can make a bunch of different sizes of cleanly arced turns on a FIS SL ski, and certainly bigger than 12-13m r. My puzzler is puzzled. Maybe I should somehow try to measure them sometime this season.
 

Erik Timmerman

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Interesting flashback when I read your post, HDN. If one does a traverse demo, how is it we can leaving two clean, straight lines on the snow with a ski with sidecut? I remember doing demos for our SSD with training group a few years back on a Head Titan. One person in the group said it would be impossible not to turn on their Experience 88. The SSD more or less said, "watch". Not being rhetorical here at all. Honestly, I can make a bunch of different sizes of cleanly arced turns on a FIS SL ski, and certainly bigger than 12-13m r. My puzzler is puzzled. Maybe I should somehow try to measure them sometime this season.

I don't know about you, but I feel like if I am "carving" that straight line traverse it is only because I am subtly steering the tips down the hill the whole time to keep the line straight. If I just stood there and let the ski do it's thing it would curve.
 

CalG

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I don't know about you, but I feel like if I am "carving" that straight line traverse it is only because I am subtly steering the tips down the hill the whole time to keep the line straight. If I just stood there and let the ski do it's thing it would curve.

By implication, the scrubbing is lost in the noise of the edged ski track width.

Hmm, perfection has it's limits... ;-)
 
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