 Poster: A snowHead
|
|
|
|
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
|
| veeeight wrote: |
| There is ski divergence, yes, but remember please, this is an outcome, not intent. Especially with Grandi, you'll find that it is NOT inside ski divergence, which is what everyone here is fixated on - it is very easy to mistake the ski divergence as inside ski divergence, but if you look at the freeze frames below, you will see this is not the case. |
V8, now you claim to know the intent of a racer who has nine podiums and two victories in World Cup?!
|
|
|
|
|
|
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
|
| veeeight wrote: |
| Grandi does much better with a little patience at the top of the turn, |
 I'm sure he will be relieved that the great V8 has given him the seal of approval!
|
|
|
|
|
|
You need to Login to know who's really who.
You need to Login to know who's really who.
|
| veeeight wrote: |
| I cannot imagine for a moment why people think that two identical skis with the same sidecut should produce different radii |
Not sure if this one has been answered yet.
1. Different edge angles
2. Differing inside/outside foot weight distribution
3. Differing fore/aft weight distribution
4. The "rotary torque" theory of Bob Barnes (search on Epic if you're interested  )
On Physicsman's theoretical "infinitely hard surface", only 1. is possible.
|
|
|
|
|
|
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
|
| veeeight wrote: |
| Masque, I am still no clearer if you support if ski tracks are identical or parallel. |
In the interests of moving this thread along with the objective of improving the general sum of knowledge of this community, let us leave aside the thorny divergence/convergence question; and would it be fair to say that we all agree now that the answer to the above question is:
"In theory, they can be either, but they can never be both simultaneously."
If anyone is NOT in agreement with the above statement, I think it's fair to say that we would all be grateful if they could concisely lay out the logical basis of their disagreement.
|
|
|
|
|
|
You'll need to Register first of course.
You'll need to Register first of course.
|
| Martin Bell wrote: |
V8, now you claim to know the intent of a racer who has nine podiums and two victories in World Cup?! |
No, I claim to be able to assess what is actually going on from that video. There is a difference. This *is* my job.
Everyone looks at the video, and in particular, gets fixated on this:
And slaps down $1000 claiming ski divergence.
Actually, yes, ski divergence, but *outside* ski divergence (outside ski running wide). Look at all the preceeding video and freeze frames.
With regard to intent of WC racers - interestingly, there has been, for the past few years, a myth surounding the White Pass turn - Phil Mahre himself has come out and said that this has never been intent, but outcome as a recovery to moving to the inside too quickly. However, there are some benefits to this move in some specific instances - and thus has found it's way into training regimes.
No one has yet been able to produce a photo montage where both skis are bent along the arc, but the inner ski is bent more than the outer ski (not one where the inner ski is bent and the outer ski is straight) - probably because it doesn't exist.
Why don't all the proponents of a deliberate inside ski diverge group plus the inside ski smaller radius group publish a paper? This is indeed groundbreaking if it were true, as no other instructor nor coach actually train people to deliberately diverge their inside ski. Debating/arguing it on here is very small fry, publish publish publish and educate the world!
|
|
|
|
|
|
|
|
|
veeeight, and at the same time you will be writing a paper on non-euclidean geometry in hyper-dimensional space?
|
|
|
|
|
|
|
|
|
Peace in the Middle East anyone?
|
|
|
|
|
|
You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
|
veeeight, So . what you're saying is that a ski has a fixed curvature that varies only with the amount of pressure put into it . . . ignoring sidecut for the minute and that it doesn't matter where a skier vectors his mass into the ski it will always bend in the same fixed curvature?
Why is everyone fixated by the existence of 'divergence' in all these pictures? Even if the skis were in a perfectly balanced, perfectly equal carve, the mechanical fact that the inner ski is further along the turn circumference means that it will be and look as if it were diverging. It is a geometric and mechanical fact, It has a role to play here but it's not as important as people think since it will occur to a greater or lesser extent however good, bad or indifferently you are skiing.
|
|
|
|
|
|
|
|
Frosty the Snowman, Now you get worried 
|
|
|
|
|
|
snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
|
| Martin Bell wrote: |
"In theory, they can be either, but they can never be both simultaneously."
If anyone is NOT in agreement with the above statement, I think it's fair to say that we would all be grateful if they could concisely lay out the logical basis of their disagreement. |
One special case where they can be both simultaneously: straight-lining 
|
|
|
|
|
|
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
|
Sideshow_Bob, I got there first a few pages back 
|
|
|
|
|
|
|
|
|
|
|
You know it makes sense.
|
|
Martin Bell, Yeah dude. I lived opposite a potatoe farmer once. No idea how to grow potatoes.
|
|
|
|
|
|
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
|
|
...but he was probably out standing in his field...
|
|
|
|
|
|
Poster: A snowHead
|
| veeeight wrote: |
| There is ski divergence, yes, but remember please, this is an outcome, not intent. |
But we have seen that divergence (and subsequent convergence) is extremely common. I would assume that the top class racers and coaches know this (Martin Bell certainly does). Therefore, if they did not intend that outcome, they would work out a way to eliminate it. Because a racer (or any other skier) may be trained to think of a particular intention, does not mean that side-effects are unintended.
|
|
|
|
|
|
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
|
|
Hey, Yogi, it's deja vu all over again.
|
|
|
|
|
|
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
|
| veeeight wrote: |
With regard to intent of WC racers - interestingly, there has been, for the past few years, a myth surounding the White Pass turn - Phil Mahre himself has come out and said that this has never been intent, but outcome as a recovery to moving to the inside too quickly. However, there are some benefits to this move in some specific instances - and thus has found it's way into training regimes.
|
This is the cool thing about building a solid skill base. Spontaneous invention springs forth to fill need. Steve Mahre was actually the inventor of the White Pass Lean, and veeight is right, it was not at all intended or planned, it was a desperation move while in the heat of a WC Slalom race run he used to avoid dumping speed after getting late. Bet your bottom dollar, though, it wasn't the first time he played on his inside ski.
Same could be said for diverging/converging skis. Racers may do it without even know they are, there bodies doing it instinctually simply because it's serving a need. Skis need to separate and come together again from transition to apex and back. Edge angles and pressure distributions are not always conducive to equal radii in inside and outside ski. Racers do what they need to do to compensate. They drag, they lift, they point, they steer, they pivot.
Last edited by Well, the person's real but it's just a made up name, see? on Wed 12-11-08 9:29; edited 1 time in total
|
|
|
|
|
|
You need to Login to know who's really who.
You need to Login to know who's really who.
|
Last edited by You need to Login to know who's really who. on Wed 12-11-08 9:20; edited 2 times in total
|
|
|
|
|
|
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
|
| laundryman wrote: |
| they would work out a way to eliminate it. |
It's only a symptom (of various causes). Fix the underlying root cause(s) and it does go away. Besides, in the grand scheme of things, it's pretty small fry symptom (unless in a particular case the underlying cause is problematic, eg: hip position).
Last edited by Anyway, snowHeads is much more fun if you do. on Wed 12-11-08 9:26; edited 3 times in total
|
|
|
|
|
|
You'll need to Register first of course.
You'll need to Register first of course.
|
| Masque wrote: |
| Why is everyone fixated by the existence of 'divergence' in all these pictures? |
Because if you are obsessed with the notion that the inner ski prescribe a smaller radius, then you have to be equally obsessed with the mechanism of Ackerman steering - and thus you will want to deliberately diverge your inside ski to achive this.
And on good stiff skis (unlike forgiving recreational skis) that track well, the inevitable yard sale will soon follow.
|
|
|
|
|
|
|
|
| veeeight wrote: |
| Because if you are obsessed with the notion that the inner ski prescribe a smaller radius, |
I don't think anyone is obsessed; as described below, it is merely one of the options available to a ski-racer (or any skier) - but limited to low-angle situations like the "railroad turns" drill.
| FastMan wrote: |
Now, to the topic of 2 ski carving. In low edge angle turns it is quite doable to cleanly carve both the inside and outside ski. But when edge angles rise that possibility becomes more remote. To carve parallel skis, the inside ski needs to ride a higher edge angle, which means the inside ski needs to be tipped onto a higher edge. At high edge angles, good luck with that. Very hard to impossible to ski artificially bow legged at high edge angles.
So then, what really happens at high angles? A couple other options exist. First, a skier can keep the skis parallel, rotationally tension the inside leg, and power the inside ski through the turn so it stays in directional harmony with the carving/turn shape dictating outside ski. That rotational tension of the inside leg injects the inside ski steering necessary to keep it tracking the direction changing of the outside ski.
The other option is to employ a bit of a divergence of the inside ski at the start of the turn. Translation: manually turn the inside ski in the direction of the coming turn as you come out of the transition, so that the skis are no longer parallel, but resemble a reversed snowplow. From that point, both skis can carve the entire turn and the inside ski does not need to carve a sharper turn to stay with the outside ski. |
And we have seen that Fastman's third option definitely can exist in the real world:
| veeeight wrote: |
|
At World Cup level, racers are making these technical decisions (usually based on tactical requirements) at an almost instantaneous, almost subconscious level, so perhaps the word "intent" is rather misleading because it implies a conscious decision.
|
|
|
|
|
|
|
|
.
.
.
.
You appear to have omitted possible the single most important table in this entire thread. One that shows that the inside ski does not prescribe a smaller radius.
| veeeight wrote: |
 |
|
|
|
|
|
|
You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
|
|
|
|
|
|
|
wow... i never knew a conversation like that was possible....
|
|
|
|
|
|
snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
|
|
|
|
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
|
|
|
|
|
|
| skimottaret wrote: |
I see a lot of "old school" skiers that scissor a lot and have a very pronounced inner tip lead. They think they are countering well and getting their shoulders square to the fall line but are really just twisting at the waist and not separating the upper/lower body, and, typically have a straight, stiff outer leg with a large inner ski lead of 20-30 cms.
What drills do you use to eliminate this problem? |
Why would you be wanting to ski the fall line? pick a line and ski it
|
|
|
|
|
|
You know it makes sense.
|
Yes, that is one explanation. There were also all sorts of questions raised about those numbers when they first appeared - including what is the definition of "overall turn radius"? - that actually means that table has very little useful to say, without further clarification.
And a final word, while we're on the subject of obsessions; whether something is a primary action/movement or secondary to something else ("intent" or "consequence") is crucial do deciding what to do about it (if anything needs to be done), it makes not one iota of difference to the mechanical consequences of being in that position.
|
|
|
|
|
|
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
|
| Martin Bell wrote: |
where the skis diverge near the beginning of the turn, the outside ski carves a tighter radius (due to higher edge angle and/or greater loading) and the skis converge towards the end of the turn.
Would anyone be in agreement with that hypothesis? |
Nope. 
This is where it all began for me: From the very start - I (and countless others) have always maintained that you do not deliberately diverge your skis at the beginning of the turn.
It was in response to this statement (which advocates the need for a smaller inside ski radius).
| Sideshow_Bob wrote: |
I see racers scissoring when they're trying to make tighter turns than their speed and ski radius would otherwise let them. Other skiers use it as a way of controlling speed while 'carving' their outside ski. I remember an article in the ESC magazine a good 15 years ago where a coach was highlighting how scissoring was the only way of doing high-speed carving due to the non-differential sidecuts of a ski and how the inside ski otherwise had to track a shorter radius turn, hence requiring more angulation than given to the outside ski. |
The two beliefs go hand in hand.
If you believe that the inner ski must prescribe a smaller radius, then you must automatically belief that you need to diverge your skis to achieve this (eg: Ackerman Steering).
However if you believe that the two ski arcs start off life as identical arcs of the same radius - then the need to beleive in diverging skis go away.
|
|
|
|
|
|
Poster: A snowHead
|
|
|
|
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
|
veeeight, I would agree with both you and Martin Bell, I think that the skis do diverge then converge again during a turn but that this isn't deliberate and would be a mistake to try to teach it by itself.
If the skier's shins stay a constant width apart then the distance between the skis must increase at higher edge angles, this can let us feel that the skis are doing the same thing even though they are not.
|
|
|
|
|
|
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
|
rjs, ever the diplomat 
Do you mean the skis themselves diverge (scissoring) or the tracks diverge and converge (tracks widening and narrowing)? I definitely agree with the latter, but not the former as intent.
Here is another take from BigE across the pond:
| Quote: |
The radius of the arc of the inside ski does not have to be smaller than the outside ski. If you think about it, the tracks left by a carving skier often widen at apex and narrow at neutral, looking a lot like a moon or banana. The radius of the short side of this shape is left by the inside ski. To make the shape, the inside radius must be larger than the outside ski or longer arc, otherwise the tracks would be widest at neutral and narrowest at apex; the inside ski would diverge and ski away from the slow turning outside ski at apex.
....... unless you hold your feet very close together at turn apex, the outside ski turns a tighter radius. This is especially evident when your stance has a constant "horizontal separation". |
|
|
|
|
|
|
You need to Login to know who's really who.
You need to Login to know who's really who.
|
|
veeeight, In the bit that you quote from BigE it doesn't make sense to talk about radius, even if the inside ski follows part of a circle the outer one must follow an ellipse for the skis to be further apart at apex but converge again..
|
|
|
|
|
|
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
|
| veeeight wrote: |
| However if you believe that the two ski arcs start off life as identical arcs of the same radius - then the need to beleive in diverging skis go away. |
The utter incoherence of this sentence is symptomatic of your hazy, even dim, grasp of logic and geometry. Stick to the day job - just don't use cod geometry and mechanics with customers who are better qualified in those fields.
|
|
|
|
|
|
You'll need to Register first of course.
You'll need to Register first of course.
|
|
I love this thread.
|
|
|
|
|
|
|
|
|
All the grandi picture proves is that skiers racing do spend time with pressure on the inner ski from time to time.
|
|
|
|
|
|
|
|
| veeeight wrote: |
| I (and countless others) have always maintained that you do not deliberately diverge your skis at the beginning of the turn. |
At the risk of getting Clintonesque about it, it depends what the meaning of "deliberate" is
Inbetween the 6th and 7th frames of this sequence
http://www.ronlemaster.com/images/2006-2007-B/slides/raich-aare-2006-gs-2.html
no, Benni is not thinking "oh, my skis will be carving identical arcs through this turn, causing them to converge as the turn progresses, therefore it is my intent to start this turn with a little bit of divergence". He just does it, based on years of trial and error. At a subconscious level, he "feels" how much divergence he will need to give him a comfortable stance width at the apex of the turn. The same way Beckham doesn't need to calculate a parabola every time he takes a free kick.
You could say he's doing it
| FastMan wrote: |
| instinctually |
By the way, we know that Benni's subconscious assumptions are based on correct maths. Identical arcs will inevitably converge, be they circular:
| Sideshow_Bob wrote: |
 |
or sinusoidal:
| GrahamN wrote: |
 |
The only way Benni's right ski can change direction like that between those frames 6 and 7 is by doing this:
| FastMan wrote: |
| The other option is to employ a bit of a divergence of the inside ski at the start of the turn. Translation: manually turn the inside ski in the direction of the coming turn as you come out of the transition, so that the skis are no longer parallel, but resemble a reversed snowplow. From that point, both skis can carve the entire turn and the inside ski does not need to carve a sharper turn to stay with the outside ski. |
There is no other way that ski can pivot like that in that short space of time. If you cannot see that, you should really not be coaching ski-racers. Benni's coach may not have told him to diverge, and indeed in the current orthodoxy that Veeeight spouts, "divergence" and "convergence" are dirty words. But it happens. And it happens because Benni's own reflexes and muscle memory have a better grasp of geometry than many top ski-racing coaches and instructor-trainers....
|
|
|
|
|
|
You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
|
| rjs wrote: |
veeeight, I would agree with both you and Martin Bell, I think that the skis do diverge then converge again during a turn but that this isn't deliberate and would be a mistake to try to teach it by itself.
If the skier's shins stay a constant width apart then the distance between the skis must increase at higher edge angles, this can let us feel that the skis are doing the same thing even though they are not. |
This is a big part of the equation. As legs tip to higher edge angles, feet must separate to keep the legs from hitting together. How that separation is accomplished is at the heart of this topic. There are two basic ways. You can drag the inside ski sideways as you tip into the turn and flex the inside leg, or you can diverge the skis at the start of the turn and let the inside ski track the inside foot into a larger separation by apex. BigE's moon example.
Last edited by You'll get to see more forums and be part of the best ski club on the net. on Thu 13-11-08 23:22; edited 1 time in total
|
|
|
|
|
|
|
|
| rjs wrote: |
| If the skier's shins stay a constant width apart then the distance between the skis must increase at higher edge angles, this can let us feel that the skis are doing the same thing even though they are not. |
Again, it depends on how you define "width". In the first turn in this video, "horizontal" width is converted into "vertical" separation - the quickest way to achieve high edge angles.
http://www.youcanski.iringweb.com/wp-content/uploads/2008/09/paerson_sl2.m1v
The actual on-snow separation of her skis is actually fractionally less at the gate than at transition. This is because her vertical separation does not quite compensate for her earlier horizontal separation, and is probably a desired tactical outcome - the outside ski remains closer to the gate and can travel a shorter distance.
Perhaps this is why we see far less "scissoring" in SL than in GS. Tactical necessities outweigh the importance of fully-carved arcs on both skis through the entire turn. It is noticeable that her inside ski only "carves" or participates in the latter part of the turn.
EDIT: this is a little off subject, but only trying to show that there are sometimes other considerations to be factored in.
|
|
|
|
|
|
|
|
FAQ
