 Poster: A snowHead
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| veeeight wrote: |
| I don't know what else to say. What happens on snow is NOT reflected by any of the maths/physics models being thrown around. |
Does that include your mathematical model of parallel curved lines of equal curvature throughout?
If not, write it up (with the illustration sideshow bob requested), get it published and sit back for your Nobel prize. You'll have revolutionised much more than skiing.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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| Quote: |
Somewhere when you're carving those lines you will have one ski starting edging slightly earlier than the other or are loading it in a way to make it track a tighter radius. You may not feel like it while you're performing the motion (it's ingrained in you) and it's probably small enough a movement so you can't perceive it, but this is what's happening in reality.
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that statement for me sums up and puts closure to this arguement. see Grahams maths above where he shows for a typical turn radius you can get equivalent arc radii by increasing the inner ski edge angle by a mere 2 degrees. I think all the arguement about the purity of the maths is kinda moot as the skier can make small adjustments to edge angle, tip lead, and bend the ski into a different turning radius quite easily to account for these small discrepancies the maths models throw up.
V8 is right, pure carves be done with subtle adjustments by the skier, your right int that the maths say that subtle adjustments are required... 
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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?
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skimottaret, nicely put.
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You need to Login to know who's really who.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Frosty the Snowman, 10 pages is pretty good going for such a minor topic isnt it, musta been a lot of pent up geekery in everyone. 
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You'll need to Register first of course.
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skimottaret, LMAO
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| skimottaret wrote: |
| V8 is right, pure carves be done with subtle adjustments by the skier... |
If that's the case then fine, but had he said that, rather than the diametric opposite - "we are doing the same thing on both skis", there would have been no argument. The problem is that he's extrapolated from that misuderstanding to completely duff explanations of what's going on. Despite having the smallness of those variations from his model of exact equivalence (a degree or so of difference in edge angle, or alternatively a degree or so of divergence) pointed out at least three times he still hangs onto the belief that he is doing the exact same thing on both legs. It's his model of reality that's failing, not that of the mathematicians. If he can show that his model does work, then he should do what laundryman says and publish, and overturn at least 400 years of received wisdom (although I think it would be the Fields Medal rather than a Nobel Prize)
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You'll get to see more forums and be part of the best ski club on the net.
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10 pages in, fun discussion on the whole with some interesting conclusions.
skimottaret, Nicely summed up
The only thing left now is for V8 to understand that parallel curved lines cannot be identical
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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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.
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Here's an interesting quote from ModernSkiRacing:
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| When carving a turn the outside ski is traveling a longer path than the inside ski, simply because it is further away from the turns center. Geometry 101. This longer travel track requires to the outside ski to travel faster than the inside ski to keep up. |
http://www.modernskiracing.org/WaistSteering.php
Veeeight, are you now disagreeing with that site? The outside ski is making a longer path through the curve.
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You know it makes sense.
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Am I disagreeing with that site? Well, lets just say I know who wrote that. wrt. outside ski travelling faster than inner, all that is required is for the outside ski to speed up, or the inside ski to slow down (what a differential does on an axle).
Thing is - all the mathematicians and physicists are so keen to rubbish that can be done in reality as opposed to on 2D paper drawings (with fixed centres etc.) - they have forgotten that in real life skiing everying is moving and changing in 3D - knees, hips, are moving not only in the horizontal plane but vertical plane.
And yes, both skis are still doing exactly the same thing in terms of edge angle. I'll grant you that they are not doing the same thing fore-aft (which is what I said about 5 pages back, but no-one seems to have picked up on that).
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| As I said, I don't give a fig whether they're perfect arcs or circles or have altering radius throughout the turn. Just draw it will you? |
I can't draw it as plainly and rudimentry tools I have can't do it. But I can photograph it from the air, and then you'll have a headache, because, as any racer knows, J turns or bananna turns are standard repetoire.
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| The only thing left now is for V8 to understand that parallel curved lines cannot be identical |
Problem is, whilst I accept it mathematically, I can't do that when I'm skiing, else I'll be always thinking that scissoring is an absolute prerequisite to carve clean RR tracks - which it isn't (the original point of this whole argument). NO WAY can you be thinking that the inner ski must carve a tighter radius.
Last edited by You know it makes sense. on Fri 18-04-08 14:51; edited 2 times in total
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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veeeight, the only things that the mathematicians and physicists have rubbished are incorrect mathematical and physical statements. You might say it's their job, as others correct poor skiing technique.
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Poster: A snowHead
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laundryman, fair point. But they do insist in trying to best fit their 2D paper models into real life 3D skiing, and saying that it's impossible........ Do they try to ski according to 2D models and deliberately scissor their turns, and/or fall over when skiing?
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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veeeight, if we tried to ski with the aim of setting down tracks of equal curvature, then we'd have to contemplate deliberate scissoring (the more so the tighter the turns). But I think most people are aiming for parallel tracks - which scissoring obviously won't produce.
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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?
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| veeeight wrote: |
| laundryman, fair point. But they do insist in trying to best fit their 2D paper models into real life 3D skiing, |
The snow surface is a (deformed) plane, so we can certainly model the ski/snow contact in 2D. No-one is trying to model anything else in 2D!
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| veeeight wrote: |
| laundryman, fair point. But they do insist in trying to best fit their 2D paper models into real life 3D skiing, and saying that it's impossible........ Do they try to ski according to 2D models and deliberately scissor their turns, and/or fall over when skiing? |
To be fair they were just trying to correct your poor maths, nobody is saying that it's impossible to carve parallel tracks. The only thing that is impossible is to carve perfectly parallel curved tracks that have identical curvature, either theoretically or in real life. The 2D/3D thing is irrelevant in this context as you are laying tracks on a 2D plane.
If you carved a perfect 360 turn, the inside ski would have to track a shorter radius than the outer. How can you draw a bigger diameter circle inside a smaller one? It's a fact you just cannot ignore.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Let me ask the question another way.
Who here still believes that the inside ski has to bend more than the outside ski in a carved RR turn?
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| veeeight wrote: |
Who here still believes that the inside ski has to bend more than the outside ski in a carved RR turn? |
Do you think the inside rail on a railway track has the same radius as the outside rail in a bend?
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| veeeight wrote: |
Let me ask the question another way.
Who here still believes that the inside ski has to bend more than the outside ski in a carved RR turn? |
I do. It turns through the same angle (skis start and end parallel), in a shorter distance (from the modernskiracing link). Ergo, it must turn tighter. If it's pure-carved, this means it's bent tighter.
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You'll get to see more forums and be part of the best ski club on the net.
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veeeight, I'm asking you the exact same question 
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| uktrailmonster wrote: |
| Do you think the inside rail on a railway track has the same radius as the outside rail in a bend? |
| veeeight wrote: |
| PS: Think railway tracks. Do you really consider that the inside track in a curve has a smaller radius than the outside track |
It would appear he does. 
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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veeeight, At some point you must finally realise that you can only produce a perfect parallel pair of curved tracks if the inside radius is less. Otherwise your tracks must be either diverging or converging. I challenge you to carve a 360 degree turn, producing 2 tracks in the snow of the same radius. Come on, this is not a difficult concept.
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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.
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Well this is the interesting point, as pointed out by someone of the other carve 360 thread, it doesn't describe a circle, more of an elipse. So in no way does it end up looking like 2 concentric circles. So whilst you end up at the end of the 360 carve going in the same direction as you started (and your end point will not match your start point), the tracks don't look anything like 2 concentric circles.
Is no one else here going to stand up and say that they believe that the inside ski has to bend more than the outside ski in a RR turn?
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You know it makes sense.
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| veeeight wrote: |
| Is no one else here going to stand up and say that they believe that the inside ski has to bend more than the outside ski in a RR turn? |
Maybe, a teeny tiny bit, at the tip. So small an amount that you would barely notice.
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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Martin Bell, how do you propose that you do that?
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Poster: A snowHead
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| veeeight wrote: |
| Well this is the interesting point, as pointed out by someone of the other carve 360 thread, it doesn't describe a circle, more of an elipse. So in no way does it end up looking like 2 concentric circles. |
Concentric ellipses then, or even a parallel spiral? Same effect, the inside ski turns tighter. It tracks a shorter length of track yet turns through 360 degrees, hence tighter turn. Why do you think they stagger runners when they're running the 400m?
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Pull the inside foot back. Oh yeah, that's the title of this thread!
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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?
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You need to Login to know who's really who.
You need to Login to know who's really who.
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| Quote: |
Why do you think they stagger runners when they're running the 400m?
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We ski with inside ski tip lead.
Do they stagger runners with inside lead, or outside lead? 
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Outside lead, which makes it even more interesting, as you've got inside lead in skiing 
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You'll need to Register first of course.
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| veeeight wrote: |
Who here still believes that the inside ski has to bend more than the outside ski in a carved RR turn? |
I do, if your RR turn is pure i.e. pure carved and completely parallel. Think railway tracks
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You'll get to see more forums and be part of the best ski club on the net.
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If the outside lane starter ran faster then they would finish equal after a 90 degree turn
(this effect is observable everyday in skiing, those that do not have an active outside foot in skiing (or those that don;t manage their tip lead) - will be seen at transisiton "shuffling" their outside ski forward to be level with their inside, in order to start the new turn balanced).
Last edited by You'll get to see more forums and be part of the best ski club on the net. on Fri 18-04-08 16:49; edited 1 time in total
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veeeight, Indeed and the inside runner would have ran a smaller radius turn, because it was a shorter distance.
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FAQ
). Physicsman would be the first to admit that his model assumes an infinitely hard surface and does not allow for any extra ski flex due to snow compression and differing fore-aft loading.
