Feeling the "Push"

[Steve]

Josh, that sounds like countersteering. Am I correct?

 

[geepers]

Does that reduce turn radius, at least that of the forward part of the ski?

Look at the tracks left by the skis in a carving turn.

Is there a way for the tips of the skis to bend a tighter radius and yet leave no sign in the tracks of having done so?

I must be smearing or skidding. I just feel I’m carving. I “feel” that the part of the edge cutting and extending a groove is tracking not what the tip started, but what the part of the ski in front of it cut. I think I’m saying, in another way, what I referred to as the effective edge. A bit after turn initiation, the pressure is further back. Where that pressure is determines what part of the edge has greatest and most significant effect. What the tip is doing, to me, seems irrelevant. But, that’s just a visualization in my head, one that is not grounded by subjective observation.

Surely the ski tracks tell the story.

The tips cannot magically create a groove without leaving any evidence in the snow.

 

[Josh Matta]

its more like resisting the skis rotation from its sidecut, but sure...

I also think there is some for and aft pressure management coming from this movement as well, since the skis are on edge.

 

[Doby Man]

Ahhhhh! Now I see where you are coming from.

I agree. Rotary has no place in carving IMO. The ability to carve is first and foremost about obtaining and edge (tipping). That being said, rotary is part of most ski turns whether by "intelligent choice" (steep/tight radius required) , preference, laziness or just poor and improper technique.

This is why when you ask seemingly advanced skiers to do railroad tracks, most all introduce rotary into the maneuver.

You mean "rotary edging". We use "skeletal" rotary in a number of areas for pure carved turns to help control the movement of pressure over the skis. I think you know this and perhaps are just being lazy. But that can confuse a lot of readers.

Again, what is being ignored is the concept of "Frame of Reference" That's what helps qualify and it does matter. "Loading" can mean many things depending on FOR.

To fall on my sword, I should have titled this thread "Feeling the Push....From the ski"

No, Jesinstr, you titled it correctly. “Feeling the push” is suggesting that we are being pushed “upon”. It is only inevitable that a following thread is going to take advantage of any possibility to view someone else’s point through their own eyes, which is often more associated with an overly simplistic view of achieving a visual output from direct input from the skier such as a skier “pushing” on the ski rather than the ski pushing on the skier. That is because most people move their CoM against their BoS rather than the other way around which is much more dynamic and effortless.

What “feeling the push” means to me is about the ground force reaction that is initiated, for me, directly from tipping the ski. While some people say “flex to release”, I take it a step sooner and say “tip to flex” whereby flexion and release will happen immediately and automatically following the ski tipping via the natural combination of mobility and movement restrictions of the human kinetic chain, also depending on absorption skills. At that level of complexity, I digress ... It is the GFR reaction from tipping the rounded ski against the snow, in a pure carved turn, that I use to power my flexion and to time the immediately following transition. If the ski is tipped too slowly and/or not enough, little to no GFR is created, typically, for intermediates and below. This “absence of force” forces the skier to flex on their own which means they are dropping their CoM to the BoS which requires a lifting effort to “re-set” that movement between every turn. When we use GFR to “lift” the BoS up towards the CoM, the BoS drops back down effortlessly with gravity which causes effortless extension. These types of flexion and extension are an automated functions of effortless expert skiing. Flexion and extension as a direct input to release the ski without the use of ground force reaction will not be well measured and timed with the immediately occurring forces of the turn nor on a natural basis. When flexion is derived from GFR, the DIRT of that flexion is “systemic” and thus including inherently appropriate measures. While “tipping to flex” is an example of skiing from the feet or the ground-up based on the direction of its kinesthetic directive, “flex to release” is not because that flexion and its DIRT is derived from the hips, in a downward associated directive, and direct skier intent is an actively direct input which moves (drops) the CoM and not the BoS. It is about employing the mechanical output of a tipping ski to “automate” many of our functions that ultimately culminate as passive outputs yet all too often seen and taught as directly active inputs.

For me skiing is not as much about the circular path that you discuss but rather how the forces are generated through how that circular path of the BoS is working “against” the straighter and flatter path of the CoM to produce all the critical and fundamental movements we discuss. In other words the PSIA fundamental of managing the relationship between the CoM and the BoS and their paths which include the kinetic chain outcome associated with the differential of the two paths taken. That kinetic chain outcome being the five movements of separation which are flexion, extension, rotation, angulation and inclination. When these movements become the indirect, systemic and passive outcomes of the management of the relationship of the CoM and BoS, they become effortlessly timed and motored.

 

[Doby Man]

I must be smearing or skidding. I just feel I’m carving. I “feel” that the part of the edge cutting and extending a groove is tracking not what the tip started, but what the part of the ski in front of it cut. I think I’m saying, in another way, what I referred to as the effective edge. A bit after turn initiation, the pressure is further back. Where that pressure is determines what part of the edge has greatest and most significant effect. What the tip is doing, to me, seems irrelevant. But, that’s just a visualization in my head, one that is not grounded by subjective observation.

If what your ski tip is doing seems “irrelevant”, perhaps you can just cut them off to save weight and maybe use them to:

1. level your TV correcting the spinal adjustment of the viewer.
2. balance your fridge so the noise doesn’t keep you awake at night.
3. use as a whimsical alpine home fashion door jam.
4. glue them to the bottom of your snow boots so you can skate across your snowy ski area parking lot.
5. or just take back that statement and forget you ever said it.

 

[geepers]

2. balance your fridge so the noise doesn’t keep you awake at night.

Please tell more. The condo we're in has a noisy fridge. I'd gladly sacrifice a ski tip or two...

 

[karlo]

Or it could be that your skis have tip rocker and the tip doesn't get involved until you reach a bigger edge angle.

Yes, rockered. Yes, I feel this not when I have high tipping angle, but with shallow angle. But, I do point the tip down at initiation to engage what I can of it.

Please tell more. The condo we're in has a noisy fridge. I'd gladly sacrifice a ski tip or two...

Tip it and stand it on it’s outside feet.

 

[Josh Matta]

Point the tip down?

 

[CalG]

Softer and deeper snow will aid us all in fully understanding just how skis and mankind were made for one another.

 

[geepers]

Tip it and stand it on it’s outside feet.

 

[JESinstr]

You mean "rotary edging". We use "skeletal" rotary in a number of areas for pure carved turns to help control the movement of pressure over the skis. I think you know this and perhaps are just being lazy. But that can confuse a lot of readers.



No, Jesinstr, you titled it correctly. “Feeling the push” is suggesting that we are being pushed “upon”. It is only inevitable that a following thread is going to take advantage of any possibility to view someone else’s point through their own eyes, which is often more associated with an overly simplistic view of achieving a visual output from direct input from the skier such as a skier “pushing” on the ski rather than the ski pushing on the skier. That is because most people move their CoM against their BoS rather than the other way around which is much more dynamic and effortless.

What “feeling the push” means to me is about the ground force reaction that is initiated, for me, directly from tipping the ski. While some people say “flex to release”, I take it a step sooner and say “tip to flex” whereby flexion and release will happen immediately and automatically following the ski tipping via the natural combination of mobility and movement restrictions of the human kinetic chain, also depending on absorption skills. At that level of complexity, I digress ... It is the GFR reaction from tipping the rounded ski against the snow, in a pure carved turn, that I use to power my flexion and to time the immediately following transition. If the ski is tipped too slowly and/or not enough, little to no GFR is created, typically, for intermediates and below. This “absence of force” forces the skier to flex on their own which means they are dropping their CoM to the BoS which requires a lifting effort to “re-set” that movement between every turn. When we use GFR to “lift” the BoS up towards the CoM, the BoS drops back down effortlessly with gravity which causes effortless extension. These types of flexion and extension are an automated functions of effortless expert skiing. Flexion and extension as a direct input to release the ski without the use of ground force reaction will not be well measured and timed with the immediately occurring forces of the turn nor on a natural basis. When flexion is derived from GFR, the DIRT of that flexion is “systemic” and thus including inherently appropriate measures. While “tipping to flex” is an example of skiing from the feet or the ground-up based on the direction of its kinesthetic directive, “flex to release” is not because that flexion and its DIRT is derived from the hips, in a downward associated directive, and direct skier intent is an actively direct input which moves (drops) the CoM and not the BoS. It is about employing the mechanical output of a tipping ski to “automate” many of our functions that ultimately culminate as passive outputs yet all too often seen and taught as directly active inputs.

For me skiing is not as much about the circular path that you discuss but rather how the forces are generated through how that circular path of the BoS is working “against” the straighter and flatter path of the CoM to produce all the critical and fundamental movements we discuss. In other words the PSIA fundamental of managing the relationship between the CoM and the BoS and their paths which include the kinetic chain outcome associated with the differential of the two paths taken. That kinetic chain outcome being the five movements of separation which are flexion, extension, rotation, angulation and inclination. When these movements become the indirect, systemic and passive outcomes of the management of the relationship of the CoM and BoS, they become effortlessly timed and motored.

DobyMan, Yes to your first comment. I should have stated Rotary Edging. After all, we talk about the importance of separation...something must be rotating.

Interesting "DobyMan" read on the second part. Have no problems with it.

 

[razie]

I find some of this fairly complicated and decoupled from the actual skiing... especially the COM/BOS references.

Here's the quick physics of a turn on groomed hard snow, using a shaped ski with camber - how the "push" appears and how this relates to technique.

centripetal force

the ski/snow interaction creates the centripetal force, along the entire ski, which bends the ski if the skier opposes that from the boot mounting point. A weak interaction like in a skid will create a weak force and a strong interaction (carving, hockey stop) will create a strong force.

As an aside: a stiff ski will dig the tip deeper and keep it engaged at higher speeds, while also requiring a larger force to bend the ski in the first place.

When the ski is engaged, the forces are balanced and there is no movement towards the "outside"... there is just circular motion of the skis. For a rough model, we can disregard snow compaction underfoot and other such small issues.

Z turns or C turns

Here's the thousand dollar question: are we discussing Z turns, i.e. skidding to an edge set or C turns? Let's take the C turn model, i.e. carving where the forces are balanced.

The initial state is one where the skier is gliding on a flat ski across the slope, so there is lateral momentum across and down the slope.

engagement

the trickiest part of the turn is the top of the turn, the high C, where engagement happens. From a lateral force of zero when the skis are flat in transition, we tip the skis on edge. As the edge angle increases, so does the centripetal force CP, if the skier maintains the ski edge engaged.

As the ski edges and engages, the CP increases. As the CP increases, the ski bends. As the ski bends, it turns.

In terms of technique - some are tempted to push into the ski here and try to bend it by pushing into it, that's a bad idea if you're looking for high performance... as JFB puts it "relax as you engage" or "don't give pressure to the mountain". the best skiers maintain just enough pressure to keep the edge engaged.

apex

However, the initial state was one with lateral momentum. When the skis are approaching the apex, the momentum will compound with the CP. Gravity also starts to add up. Just past the apex, the pressure is maximum, assuming the skier is resisting it (with a long leg). In JFB's words: "receive pressure from the mountain".

deflection and release

How does the lateral impulse to deflect gets created? First look at what's being created:
a) resisting this maximum force will compress and tense the body and bend the ski, peaking right under the apex
b) the circular motion has momentum at this point, pointing across and down the slope

When the ski is engaged, the forces are balanced and there is no movement towards the "outside"... there is just circular motion of the skis. If the skier does not do anything, there will be no deflection, as the ski will complete a circle, go up the hill and the hips just scribe their own little circle.

If we release at this point, a) will generate "rebound" which is back up the hill and across the hill and b) will slingshot the boots and skis across and down.

The question is:
x) has the skier generated enough a) and b) to be able to flex to release or does the skier need to add to the current forces by pushing and hopping to get off the edges?
y) can the skier use b) to impulse the body across the slope?

x) is the big discriminator: if the skier hops out of the turn, he or she will not engage the skis in the next high C, unless the turns are slow enough and big enough.

As always, most beginners can carve clean big arcs on green runs. What discriminates an expert is the ability to carve small arcs on a black run!

middle of the boot

We did not need to discuss COM/BOS at all so far and we were able to describe roughly everything, with the simple assumption that the skier will stay in the middle of the boot and only control tipping and untipping (and whatever else is needed to maintain contact and stay in balance, like flexing and extending of the legs etc)

Fore/aft are optimizations of this model - as noted multiple times in the past few threads, the shaped skis can be carved reasonably from the middle, at a lower level of performance.

clean carving

I think by now all are convinced that there can be 100% carved turns. Easily demonstrated by doing large arcs on a green. The harder and faster it gets, the harder it is to maintain the clean carving.

one foot or two feet

Pressuring one foot vs two feet is not relevant for this rough model, although the body's weight will create more CP via one single foot engaged as opposed to two (distributing the body's weight will reduce the CP in half on each leg and this will reduce the ski bend, especially at the top of the turn)

Also, since the inside leg cannot be long through the arc (at any decent angles), putting any supplemental pressure on it will result in increased tiredness, as this leg is not stacked, but bent and thus "extra" weight on it requires significant muscle action. You can see why racers avoid that, especially as they pull 3g in the middle of a GS turn. if they put 50% of weight on the inside ski, for equal ski bend it's like doing a squat with 150% of the body weight - if they put even just 20% of that on the inside foot, it would mean doing a full squat with 0.6 x body weight, in every turn... which would be completely unnecessary

it's late, so I'll end here. I will expand on this later and dive into the current WC technique and why it's simply the effective solution to the physics of skiing.

 

[Doby Man]

Aligning our center of mass and base of support is how we obtain balance and control, without of which, nothing written in the above post would be possible. Breezing over the core fundamentals of skiing is an unfortunately somewhat common developmental/instructional habit that is often supported by a convoluted set of disconnected instructions (often never heard elsewhere) that do not follow a common theme, any pecking order or hierarchy as demonstrated above and making the learning process very difficult.

 

[razie]

Aligning our center of mass and base of support is how we obtain balance and control, without of which, nothing written in the above post would be possible. Breezing over the core fundamentals of skiing is an unfortunately somewhat common developmental/instructional habit that is often supported by a convoluted set of disconnected instructions (often never heard elsewhere) that do not follow a common theme or any pecking order as demonstrated above and making the learning process very difficult.

That's exactly what I mean about over-complicating things. What's wrong with just saying "stand on your skis" (which is what I did, if you do read carefully).



So, an instructor that just recites someone else's book would instruct someone to "align their center of mass over the base of support" resulting in the skier resolving volume integrals and complex body-mass density equations to figure out even the first part of that sentence... while an effective instructor (me in the example above) would just tell the skier: "stand on your skis".

Which do you figure would get an effective outcome? And which would just continue adding words to a topic, so disconnected from actual skiing? Not to mention that fact that your version is incomplete and totally misleading: which direction do you align against? To resolve that, the skier will need to resolve more equations, adding vectors and mv squared etc.

Again, @Doby Man this simple fact seems lost on you: aligning COM with BOS is for the single purpose of not falling. That's all you achieve if you align those. Also, in any skiing above gliding on a green run, they're only aligned for a fraction of a second. Focusing on that alignment is just wasteful for me, since it's missing the 90% of skiing that actually matters... and where those two are in no way aligned... so in fact, your statement is statistically wrong: COM is not aligned with BOS for more than 90% of a turn. In fact, skiing is an act of disturbing balance!

 

[Steve]

@razie I can "stand on my skis" and be on my heels quite easily.

When I'm moving along whether on a shallow or steep trail I need to manage my fore/aft balance so that I am in the middle or front of the skis for the most part.

That's what keeping your COM over your BOS means to me.

Simple. Just focus on my balance. If I'm balanced in motion (my COM is over my BOS) then I can do all the other things that we do as skiers.

Of course an Instructor would never use those terms.

And you post an angry face because @Doby Man is overcomplicating things? Your 1,015 word post was simple?

 

[razie]

Simple. Just focus on my balance. If I'm balanced in motion (my COM is over my BOS) then I can do all the other things that we do as skiers.

You got it! Just in case you missed it:

We did not need to discuss COM/BOS at all so far and we were able to describe roughly everything, with the simple assumption that the skier will stay in the middle of the boot and only control tipping and untipping (and whatever else is needed to maintain contact and stay in balance, like flexing and extending of the legs etc)

And you post an angry face because @Doby Man is overcomplicating things? Your 1,015 word post was simple?

Well, explaining the entire physics of a basic ski turn and deducing the most important elements of the technique of high-performance skiing in 1,015 words (I'll trust your number) and no equations, I think it's pretty, pretty good

 

[markojp]

Simple. 'Where' to stand on one's skis while moving, and 'how'. That's all that's missing from the soon to be page 6 semantics. Loop that back to 'feeling the push' back from the snow from the feet, and there you go. That seems to be about it. Skiing is not easy, but it is simple.

 

[razie]

Simple. 'Where' to stand on one's skis while moving, and 'how'. That's all that's missing from the soon to be page 6 semantics. Loop that back to 'feeling the push' back from the snow from the feet, and there you go. That seems to be about it. Skiing is not easy, but it is simple.

So skiing is a continuous loop of figuring out where and how to stand when the push comes.



I actually like that...

p.s. you are so right, I am changing my signature from "easy" to "simple".

 

[Steve]

Well, explaining the entire physics of a basic ski turn and deducing the most important elements of the technique of high-performance skiing in 1,015 words (I'll trust your number) and no equations, I think it's pretty, pretty good

Until you post a correction/retraction of parts of it.

 

[karlo]

would just tell the skier: "stand on your skis".

Amazingly, though I received training on it, I gave, in the three years I have been instructing, my first new-to-sport lesson this weekend. Whereas "stand on your outside ski" works very often with those that I typically teach, intermediates, it was perhaps only 33% effective for this group. I then went to steering. But, I think it became confusing to the students. I guess I should have started with steering. And, as it turns out, I will have the opportunity to have my wedge christie reassessed this week. I now have a much better appreciation of what a wedge christie is all about. Steering, leg rotation, with just a touch of standing on the outside ski! No angulation, no carving, and no heavy focus on standing on the outside ski, is that right?