Carving turn phases - Reilly McGlashan's theory

[razie]

I see some things a little different...

You cannot go straight down when the ski is bent a lot. Simply impossible.

I think you can - hockey stops. There's no denying the ski bends, just not enough tilt to grip and deflect... granted, it's a "corner case"...

GRF is dependent on weight, speed and turning radius, it has nothing to do with the ski or ski technique. Doesn't even matter if it's on snow. It is merely physics, what you're traveling on and with is not important. It doesn't matter whether you make a 12 meter radius turn with 4 meter offset at 50 km/h on a ski, a sled, a bycicle, a tractor, or whatever. As long as these items weigh and behave the same as a ski, the physics will be the same. You can do this on sand, rocks, grass whatever. Ergo, if you would be able to move yourself forward at 50 km/h and make a 12 meter radius 4 meter offset turn, the centripetal force and GRF would be exactly the same on any surface and on any item (if the weight is the same).

Ah - not quite. That's the problem with physics and reality sometimes it's too idealized...

I had a quick back and forth on this with Jurj, the inventor of the shaped ski. While it (talking to some famous guy) doesn't validate the rest of my post, he's right that there is a maximum ski bend at a certain force applied on it (and resultant GRF), given the snow's deformation ability. When you reach that maximum, the ski won't bend anymore even if you double the force applied.

Let's have this thought experiment - glide on ice on a green run, with all your body weight on the ski. Getting deflection at 5 degrees tilt results in a larger radius than getting deflection at twice that tilt, ay 10 degrees, although your weight is the same. The force vectors change slightly since you're turning tighter, but not much. If my cousin (yeah, he's like that) decides to jump on my back in the middle of that turn, the turn radius won't change because the ski bend won't get bigger although the force just doubled in all directions (and the GRF with it, lest I sink into the snow). That's Jurj's point, and I think he's right.

Either case, same weight/pressure bent the ski twice as much just because I tilted it more. The lateral component was higher at 10 degrees, but it doesn't change the fact that I was applying the same tilt and weight to the ski.

And that gives you also the logic behind controlling the GRF with technique: it's a matter of the angles you're able to create at what point in the turn.

So... at normal speeds is this, let's say 30 mph or 50kmh: at linear speed X, some people are able to tilt the ski N degrees and get an R radius turn while others are able to tilt at N+n and get an R-r degree, with a bigger deflection force.

Let's have another thought experiment: one of them almost ran into me the other day, so this is fair: catching one of those morons that are tucking it straight down, with a lasso from the side of the run and deflect them into a turn. The turn radius is given by your distance to the moron and it's constant then, regardless of the tucker's mass and speed. If the speed is double, there will be a lot more centripetal force for the same radius and you'll need a stronger lasso. That's the basic theory behind it: at a given snow and max tilt angle A, the ski bend B resulting in the maximum radius R. At any speed above V, the ski won't bend anymore, because the snow doesn't give in anymore, but you have a bigger centripetal force to recon with, because V is higher. Or the skier is fatter... At the same time, if it's possible to have a bigger angle A++ it will allow a bigger ski bend thus a smaller radius, thus a higher maximum GRF. That's where technique comes in. That doesn't change the fact that if you go at it with twice that speed, the ski won't bend anymore, your body will just have to put up with higher turning force, the higher GRF. (of course, idealized assuming the ski has no lateral twist - which actually gives the skis their maximum force thus radius at an angle (a racing lasso is stronger but has it's limits too)...

The ski bend is not a result of the turning radius - it's the other way around: your ability to bend the ski dictates the radius...

cheers.

 

[Steve]

Gotta have video. Trying to improve your technical skiing without video is like trying to improve your cooking without tasting what's in the pot: You may be following a recipe to the letter, but you're fooling yourself about what's actually going on, because the recipe is not the the dish. A recipe is like a handful of utterances from a coach, not what you actually did after she said them.

Totally disagree. Cooking is preparing something for later consumption
Skiing is for the moment it is happening.

 

[razie]

Totally disagree. Cooking is preparing something for later consumption
Skiing is for the moment it is happening.

no way, Jose... have you heard of video? I don't know who your coach is but with my coach, anything you do on snow today is for later disappointment, when he sees the video ...

 

[Steve]

If I'm playing piano for an audience it's different than if I'm playing for myself.

 

[Steve]

Intrinsic not extrinsic.

I discovered that intrinsic gratification (that being satisfaction coming from within) is the key to peace and happiness in my life. To heck with what the rest of the world thinks. If we try to please them, if we base our happiness on outside approval, we'll never be truly content and at peace, because there will always be disapproving voices to be heard and agonized over.

I LOVE to ski. Don't interfere with my delusion.

 

[Tony S]

Intrinsic not extrinsic.

I discovered that intrinsic gratification (that being satisfaction coming from within) is the key to peace and happiness in my life. To heck with what the rest of the world thinks. If we try to please them, if we base our happiness on outside approval, we'll never be truly content and at peace, because there will always be disapproving voices to be heard and agonized over.

I LOVE to ski. Don't interfere with my delusion.

Someone has to buy the last remaining copies of novelist Richard Brautigan's Trout Fishing in America!

 

[Skitechniek]

I see some things a little different...



I think you can - hockey stops. There's no denying the ski bends, just not enough tilt to grip and deflect... granted, it's a "corner case"...



Ah - not quite. That's the problem with physics and reality sometimes it's too idealized...

I had a quick back and forth on this with Jurj, the inventor of the shaped ski. While it (talking to some famous guy) doesn't validate the rest of my post, he's right that there is a maximum ski bend at a certain force applied on it (and resultant GRF), given the snow's deformation ability. When you reach that maximum, the ski won't bend anymore even if you double the force applied.

Let's have this thought experiment - glide on ice on a green run, with all your body weight on the ski. Getting deflection at 5 degrees tilt results in a larger radius than getting deflection at twice that tilt, ay 10 degrees, although your weight is the same. The force vectors change slightly since you're turning tighter, but not much. If my cousin (yeah, he's like that) decides to jump on my back in the middle of that turn, the turn radius won't change because the ski bend won't get bigger although the force just doubled in all directions (and the GRF with it, lest I sink into the snow). That's Jurj's point, and I think he's right.

Either case, same weight/pressure bent the ski twice as much just because I tilted it more. The lateral component was higher at 10 degrees, but it doesn't change the fact that I was applying the same tilt and weight to the ski.

And that gives you also the logic behind controlling the GRF with technique: it's a matter of the angles you're able to create at what point in the turn.

So... at normal speeds is this, let's say 30 mph or 50kmh: at linear speed X, some people are able to tilt the ski N degrees and get an R radius turn while others are able to tilt at N+n and get an R-r degree, with a bigger deflection force.

Let's have another thought experiment: one of them almost ran into me the other day, so this is fair: catching one of those morons that are tucking it straight down, with a lasso from the side of the run and deflect them into a turn. The turn radius is given by your distance to the moron and it's constant then, regardless of the tucker's mass and speed. If the speed is double, there will be a lot more centripetal force for the same radius and you'll need a stronger lasso. That's the basic theory behind it: at a given snow and max tilt angle A, the ski bend B resulting in the maximum radius R. At any speed above V, the ski won't bend anymore, because the snow doesn't give in anymore, but you have a bigger centripetal force to recon with, because V is higher. Or the skier is fatter... At the same time, if it's possible to have a bigger angle A++ it will allow a bigger ski bend thus a smaller radius, thus a higher maximum GRF. That's where technique comes in. That doesn't change the fact that if you go at it with twice that speed, the ski won't bend anymore, your body will just have to put up with higher turning force, the higher GRF. (of course, idealized assuming the ski has no lateral twist - which actually gives the skis their maximum force thus radius at an angle (a racing lasso is stronger but has it's limits too)...

The ski bend is not a result of the turning radius - it's the other way around: your ability to bend the ski dictates the radius...

cheers.

Well we first have to establish what a ski can do. It can do either of two things, namely carve or skid.
In a carved turn a ski will always follow its shape, an engaged ski can simply not not follow its own shape.
In a skidded turn a ski never follows its shape, there will always be tail displacement. A skidding ski turns because of FS2 > FS1 where FS1 is the resultant force of the impacting snow acting on the tail end of the ski and FS2 is the resultant force of the impacting snow acting on the leading end of the ski. A hockey stop is skidding, so per definition the ski won't follow its shape.
And before someone says a ski follows a shape while skidding. No, not possible, go follow a physics lesson. I think everyone knows the saying 'Insanity is doing the same thing, over and over again, but expecting different results.' A contrario I could argue it is insanity to do two different things, but expect the same result. Skidding and carving are two different things, don't expect the same ski/snow interaction. Carving is dictated by radius and skidding is not.

Firstly I have a problem with applying GRF, you cannot apply GRF. GRF happens. Secondly, if the weight of a skier increases, GRF increases too (I see you edited your post now, but I'm pretty sure the first time you said GRF doesn't change with someone on your back). Newton's third law: If an object A exerts a force on object B, then object B must exert a force of equal magnitude and opposite direction back on object A. Meaning, ground reaction force will always be equal to the weight of the skier. If someone jumps on your back, GRF increases. It's as simple as that.

Yes, there is a maximum ski bend, but there is no way causality with ski bend and GRF. You can even hardly speak of correlation. GRF happens cause of your weight, speed and radius like said. Someone weighing 80 kilo's will have much higher GRF than someone weighing 60 kilo's if they ski the same radius turn at the same speed. Like I said so many times, GRF is dependent on weight, speed, radius etc. Hence the path you travel is important too. Doesn't matter whether the ski bends or not. GRF is likely higher in a short turn than in a carved turn, even though the carved turn has a bigger ski bend. But again, ski bend and GRF are two seperate things. There is GRF because you weigh 70, ski 50 km/h and ski a 14 meter radius 6 meter offset path. Ski bend, no ski bend, doesn't matter, if you ski that path, the forces will always be the same if all variables are equal. Now obviously the ski bend dictates the path you will travel, but GRF does not increase because of the ski bend, but because of the path you're travelling. And it just happens to be the case that in this sport you need ski bend to travel a certain path. But if we lived in an imaginery world where we can ski the same path without bending the ski, the forces would be the same. So yes, your ability to bend the ski dictates radius, I agree, but in no way it dictates forces. Forces don't increase because the ski bends more, but because the path changes, which changes your weight due to increased centripetal/g-force.

So like illustrated above, you were missing my point. The point is that GRF is mainly a result of weight, your weight however can change due to radius and speed. If you make a 12 meter radius turn at 50 km/h with 6 meter offset, my weight changes and my GRF changes. That's why I said it has nothing to do with skiing or ski's etc. It's physics, if I make a 12 meter radius turn at 50 km/h with 6 meter offset on a sled, on a bycicle, on whatever (and the object weighs and behaves the same as ski's) the forces will be the same. No matter whether I do it on rocks, grass or snow. So in that sense, those forces are not ski specific. It's simply how physics in general works. So no matter how good or bad your technique is, if you turn at the same speed, with the same offset and the same radius and the same weight, the forces will be the same. How you got there ski technique wise doesn't matter. But obviously someone with better ski technique will create bigger forces, but that is not the point.

 

[markojp]

Because I'm bored, and in the interests of clearing up confusion and preventing the spread of misinformation, I will feed this troll. It is a myth that every skier is trying to brake. In fact some skiers are trying to ski faster, and many skiers are perfectly content with whatever speed the slope and conditions deliver.
The definition of a turn is a change in direction of travel, not braking. Good skiers turn to change their direction of travel. Their intention is to "Go there", not to stop going.

So, where does this myth come from? What gives it traction?

I can see two factors. Poor instruction from day one. Even predating the gliding wedge, some poor instructors were teaching the snow plough as a braking maneuver instead as a battle between two skis to go right versus left with the more tipped and weighted ski winning the battle to "go there".
Other factors are the importance of safety, the needs and concerns of the typical lesson taker, and the relative difficulty of teaching a newbie how to do a true braking maneuver, e.g. hockey stop.
That being said, it must be admitted, if being truthful, that turning introduces more friction, which slows one down. The best skiers endeavour to turn with the least friction possible, carrying the most speed around the turn as often as they can (i.e. not when they need to slow down).

Adult learner fear is real. Steep terrain amplifies this. I know one skier in particular who skis to L3 standard on moderately pitched groomed terrain. Tip up the table, add variable off piste conditions, and this person will get a bit back and in. They're quite candid about admitting their fear. This person still skis steep off piste better than the large majority of recreational skiers even as an adult learner with about 15 years of skiing under their belt. And we need to remember steep is relative. We have blue runs here that are steeper than 99% of upper midwest black and double black runs.

This whole braking argument is silly. We're either pushing the skis out and away from us (making forces... this is what most do), or we're letting pressure come to us (managing/using pressure to change direction). The former is physically more taxing, the latter much less so, but it's also very counter intuitive as it requires a bit of trust and patience that skis will do what they're designed for. Fear vs. flow... fear is Z shaped turns hurriedly executed to 'get around the corner. Flow is circular and round and is predicated on being able to move effectively over the old outside ski. Call it toppling or whatever, but there has to be confidence that one's skis will catch up, and that's where fear pokes its ugly mug into the picture.

 

[markojp]

Here's an interesting example. Pause the vid and read what this ex-race and race coach guy is thinking about when he turns - at about 90 seconds in. It's mind boggling.


Do you reckon he should think more or less about ski racing for his own skiing?

Watch part 2 to find out what TG and SIA guy think.

The skier being MA'd appears to have embraced the twin mantras of 'long leg/short leg' and 'crush the front of the cuff' to the exclusion of effective structural
alignment through the pelvis, and 'front' of the ski vs. 'front' i.e. down the hill.

 

[razie]

Looking at the environment/equipment - the dude seems to be on bad snow - he's breaking through or jamming the left foot a couple times? I'd be curious to see if he still falls on the inside ski in good snow too...

He also needs different boots or better fore/aft setup on those.

We're either pushing the skis away from us (making forces... this is what most do), or we're letting pressure come to us (managing/using pressure to change direction). The former is physically more taxing, the latter much less so, but it's also very counter intuitive as it requires a bit of trust and patience that skis will do what they're designed for.

 

[Noodler]

This whole braking argument is silly. We're either pushing the skis out and away from us (making forces... this is what most do), or we're letting pressure come to us (managing/using pressure to change direction). The former is physically more taxing, the latter much less so, but it's also very counter intuitive as it requires a bit of trust and patience that skis will do what they're designed for. Fear vs. flow... fear is Z shaped turns hurriedly executed to 'get around the corner. Flow is circular and round and is predicated on being able to move effectively over the old outside ski. Call it toppling or whatever, but there has to be confidence that one's skis will catch up, and that's where fear pokes its ugly mug into the picture.

Hallelujah. Nice post.

 

[Viking9]

Sorry for the drift but if the guy in the # 109 video is what instructors are teaching , and he’s doing a good job of doing what he’s told , I don’t know.
To me there’s just no style.
How about style and athleticism.

 

[razie]

To me there’s just no style.
How about style and athleticism.

Yah, I don't know, blue pants would work better, yah... If were going to look at style...

He's not really athletic, he's freaked out and pushing/reaching for balance, what @markojp said. Been there, done that... The dude is not really in a bad place - some equipment alignment, some technique work, he can do fine... Here's me freaking out in bad snow now...

 

[James]

Sorry for the drift but if the guy in the # 109 video is what instructors are teaching , and he’s doing a good job of doing what he’s told , I don’t know.
To me there’s just no style.
How about style and athleticism.

Did you read what the guy is thinking? He’ll likely never have what you’re talking about.

Bob Barnes talked about teaching a legit Prima Ballerina, retired. She could make pretty much any move you taught her and follow anything. But when it came to just skiing, there was no self expression or breaking from a set thing. Just didn’t compute.

 

[geepers]

What is really cool is that in Gellie's Advanced Bump Webinar he talks about skiing fall line zipper line moguls where the skier wedges/stuffs the tips into the uphill face of the next bump to reduce speed. A speed control concept completely new to me and which I am excited to try. He describes this as the "Vertical Turn" I.e., bumps are a form of turning, however, in the vertical plane.

Yep, another interesting webinar from TG. There's a point to note - participating in that webinar was a CSIA L4 instructor from WB, Guy Dale, who made the point that whilst this works it will happen at a higher speed than most skiers anticipate. So need to be comfortable with that higher speed while dealing with bumps.

Got to try this wedging thing on what turned out to be the last day of my season. The 1st attempt ended up sitting on the snow wondering what happened. The 2nd attempt popped out of the bump perfectly balanced - unfortunately not wearing any skis. The slush from the day before had been covered in a layer of ice overnight and the tips broke through. Will maybe try it again next season.

Be interested to know how you get on with TG's bump stuff including the tip wedging.

Turning does slow down your vertical rate of descent, but it isn't braking, particularly in a pure carve.
So once again it's semantics. It's not braking, but it does slow you down.
Ski the slow line fast.

People who enjoy high speed skiing don't turn to slow down; they turn when they must and try to ski as fast as possible while making the turns they have to make (e.g. because the trail turns).

This whole braking argument is silly.

We turn to control direction (which is compulsory otherwise we hit things or exit the course) and manage speed. Any time we have the skis out of the fall line we are not optimizing gravitational force so we can manage our speed by turning back and forth across the fall line. Note that's manage speed - as in both decrease and increase. An exercise we sometimes do in CSIA courses is to carve at a consistent speed on a slope with sections of varying pitch by altering line.

Gotta have video. Trying to improve your technical skiing without video is like trying to improve your cooking without tasting what's in the pot

Yes. What we feel isn't necessarily what's going on. Objective evidence.

If I'm playing piano for an audience it's different than if I'm playing for myself.

Trouble is what we hear may not be what others hear. One of my kids was a handy musician in high school. He once asked what was the country and western tune I was playing on guitar. Unfortunately it was Pink Floyd's "Wish You Were Here".

I would think ALL of us would want VERY much to get in a GS course, albeit perhaps not a World Cup one.

I'm pretty sure it would give about the same result as playing from the championship tees. May want to hit the ball the way Fred Couples used to but not deluded enough to think that's going to happen.

I LOVE to ski. Don't interfere with my delusion.

I feel the same way about guitar playing. It sounds like Jimi Page in my head....

Looking at the environment/equipment - the dude seems to be on bad snow - he's breaking through or jamming the left foot a couple times? I'd be curious to see if he still falls on the inside ski in good snow too...

That's a good thought. Only issue - that was the snow he had to deal with at the time.

Sorry for the drift but if the guy in the # 109 video is what instructors are teaching , and he’s doing a good job of doing what he’s told , I don’t know.
To me there’s just no style.
How about style and athleticism.

Well, those 2 instructors weren't teaching that. In fact they prescribed a back to basics, practice at a lower level.

 

[Tony S]

Got to try this wedging thing on what turned out to be the last day of my season. The 1st attempt ended up sitting on the snow wondering what happened. The 2nd attempt popped out of the bump perfectly balanced - unfortunately not wearing any skis.

This made me laugh hard. Real life on skis.

I'm pretty sure it would give about the same result as playing from the championship tees.

A Nastar course, for example, on a hill with a little pitch, is not at all a championship tee. Nevertheless it tends to be very revealing. (A few Nastar and club courses are so flat and straight that you can basically navigate them in a tuck, which is kind of pointless imo.)

 

[Loki1]

markojp said:
We're either pushing the skis away from us (making forces... this is what most do), or we're letting pressure come to us (managing/using pressure to change direction). The former is physically more taxing, the latter much less so, but it's also very counter intuitive as it requires a bit of trust and patience that skis will do what they're designed for.

So how do we let pressure come to us? What does that really mean?

 

[LiquidFeet]

So how do we let pressure come to us? What does that really mean?

Letting pressure develop means the skier does not push the skis against the snow in order to increase pressure beyond the available pressure that's already there. Where does that pressure come from? The line the skier is skiing, and the point on that imaginary line in the turn.

@Loki, are you looking for physics type descriptions here with specific forces mentioned?

 

[JESinstr]

Assuming we are talking carving (creation of circular travel) does not the above discussion depend on velocity ?

At some point, the function of bending the ski morphs from a dominant downward force (Gravity/your weight) to a dominant inward force (Centripetal/your mass).

In most of the stuff being posted here, velocity is assumed and hence the movement patterns being advocated are all Centripetal Dominant. This reality can be problematic in the context of the skier's ability execute what the pundits are advocating. If a skier's reaction to velocity is strictly extend/push/brace what makes you think that you are going to get them to willingly move their mass offensively in the direction of intended travel?

I bring this up because there is the big difference between experts, intermediates and beginners when addressing carving skills.

Beginners start the carving process under gravity and their first carved wedge turns will most likely end in that state. So for them it is a matter of lateral movement of weight for the purpose of increasing pressure to an already established inside edge of their new outside ski. Totally different from the movement patterns associated with a Centripetal Dominant state. But it's a start both from the perspective of physical execution and mental understanding of the carving task at hand, something the self/improperly taught skier is lacking.

 

[Mike King]

@JESinstr your definition of carving is s not the definition I believe most instructors or ski associations adopt. They generally define carving as edge locked turns ; e.g. snow moving along the length of the ski, not across the base or edge of the ski. A basic parallel turn is not a carved turn In PSIA parlance. A wedge turn performed by a beginner would not be a carved turn. I don’t think most would consider a power wedge performed by a member of the Swiss demo team to be a carved turn either even though one ski is carving.

if you look at Reilly’s video referenced in the OP you will see that it is a carved turn according to the definition above.Thus, centripetal force is the dominant force to be dealt with although gravity plays a role in managing the magnitude of pressure in different phases of the turn.