 Poster: A snowHead
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I completed my BASI L1 and L2 last winter. One of the things that was drilled into us was pressure + edge + rotation as the three elements of turning while skiing.
I fully understand edge and rotation as concepts, but I have never really "got" the pressure part.
Pressure is defined as force/area (force over an area)
BASI talks of controlling pressure, absorbing pressure etc. Do they mean force rather than pressure? The pressure that you can feel is the force projected over the surface area of the bottom of your foot, and since the area of your foot is fixed it would make more sense to me to talk about feeling the force.
Does anyone else find the pressure/force distinction here confusing? Would be especially interested to hear from BASI people!
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Feel the force. Feel the pressure. For me there is no difference between the terms as far as skiing goes. I'd use them interchangeably if a client preferred one word rather than the other.
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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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given that you have stated the area is fixed (foot sized) pressure and force are proportional and therefore interchangeable when speaking. 
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| Quote: |
feeling the force.
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well if your a Jedi then it would make sense to feel the force. The pressure they are talking about comes back from the snow as the arc of the turn increases. forces that are stopping you from drifting down the hill,(the edge biting and resisting gravity) as these forces grow they will make the edge hold allowing you to influence the arc of the ski. however if the forces grow too much the the "pressure will build too much" and the ski/skier will not be able to maintain its grip and the ski will break away. Therefore it is necessary to allow the build up of pressure at the start to get the ski gripping and then to maintain the pressure throughout the turn to allow the ski to continue its grip/carve and allow the ski to work properly.
hope that helps
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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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The important take away is to come to understand the relationship between pressure and balance. Pressure management is about balance skills development. Changing your state of balance changes the pressure picture. Base of the foot pressure awareness, how it's distributed, is your guage of what you're doing, and how you're doing.
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You'll need to Register first of course.
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I think rob@rar has this one - it's just semantics, not physics!  Use the word the customer "gets".
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Imagine standing on a turntable with your feet astride the vertical pivot.
Applying more force/weight/pressure to either foot will do nothing productive.
But then imagine someone picks up the back of the turntable so that the pivot is tipped forwards.
Now, if we apply more force to one foot then the turntable will rotate until this foot is at the lowest point. We don't need to apply any 'rotation' - the turntable will do this just by pressure alone.
Leaping back to snow for a moment, this foot can now have a great deal of force on it - the majority of our body mass plus that 'weight' generated by centrifugal force as we make the turn.
To stop the ski breaking away down the hill we need to manage this force by carefully absorbing it. This allows the edges to grip properly and momentum lets us complete the turn.
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| Quote: |
| pressure + edge + rotation.... but I have never really got the pressure part. |
Yup - The term pressure is not as intuitive as rotation or edge.
Imagine a very basic snow plough turn.
Where you stand static like a goalie and just push hard (down into the ground) with your left or right big toe to make the turn.
That is a turn made using just the pressure element.
In a parallel turn pressure becomes a measure of the force you apply to each ski.
Wide GS turns will require more of the pressure element (on the outside ski)
Short turn in moguls will use more of the rotation element.
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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.
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Haggis_Trap, not being a scientist, I struggled with altis' analogy, whereas yours is crystal clear. Shows that Alexandra's spot on when she says
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Use the word the customer "gets".
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musehead, Another way of thinking about it is what's happening to the ski.
'edge' - you 'tilt' the ski.
'rotate' - you 'turn' the ski (and leg).
'pressure' - you 'bend' the ski.
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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david@mediacopy, nice.
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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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Does this pressure element go back to the downweighted turns and upweight turns,
is it pressure, edge,,, rotation or edge pressure rotation?
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| livetoski wrote: |
| is it pressure, edge,,, rotation or edge pressure rotation? |
It varies, and the blend (the rate and range of how each element is applied) will change all the time. When I teach I try to develop my clients' skills in each element through different drills, but then when putting it all together I find that most people perform better when you talk about outcomes (turn shape, speed, etc) rather than inputs (apply a bit more pressure at the top of the turn).
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You know it makes sense.
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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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Yes, pressure and force are interchangable for most circumstances in a teaching situation. There are occasions though when thinking about "how skiing works" where the differences are key to the argument (those with long memories may remember we also crossed swords with veeeight about this a while back).
I've also had problems "getting" the pressure as a means of turning argument - as pressure/force by itself will do nothing about turning a ski. It does so though when a shaped ski is edged - and also when angled away from the horizontal in soft snow. Pushing on a completely flat ski will do nothing - so you mustn't isolate the elements too much.
| rob@rar wrote: |
| ...but then when putting it all together I find that most people perform better when you talk about outcomes (turn shape, speed, etc) rather than inputs (apply a bit more pressure at the top of the turn). |
Hmm, horses for courses. Depends on the level/circumstances of what you're trying to do. One of the big changes in my skiing this year has been to get better acceleration and turn control in phase 1. This has been entirely due to thinking carefully about and feeling the pressure/force at and just after the transition. The output has been a known desire for several years, and has on occasion happened by fortunate accident, but that's only turned into a reality by careful concentration on the inputs - then of course, seeing how changes to those affect the outputs. The same thing has applied equally well to several people I've been coaching this summer. So, OK, different clientele to your normal set, but for wannabe and mid-level racers this can be very important. Just last week we were doing some work focussed very much on input, but in an unfamiliar context, and the transformation in performance when we then dropped back to the normal context was remarkable.
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Poster: A snowHead
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| GrahamN wrote: |
| ... so you mustn't isolate the elements too much ... |
Agreed, it's almost always a blend of all three.
| GrahamN wrote: |
| rob@rar wrote: |
| ...but then when putting it all together I find that most people perform better when you talk about outcomes (turn shape, speed, etc) rather than inputs (apply a bit more pressure at the top of the turn). |
Hmm, horses for courses. Depends on the level/circumstances of what you're trying to do. One of the big changes in my skiing this year has been to get better acceleration and turn control in phase 1. |
Yes, agreed again. If you are trying to fine tune performance rather than change it altogether then it's back to thinking about inputs, but not every skier reaches the level where they are trying to fine tune their performance.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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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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So this American bloke shows up for a BASI 1 course, lets call him quickbloke. He is an ex racer and really knows his stuff to say the least.
Now do they, at the end of day 1, tell him he has already passed as he is way above the required standard....
...or do they have him doing one legged pivot slips, switch, on telemark skis, then tell him about centripetal forces that exist only to counter centrifugal forces that don't exist, or even phantom feet?
Its all about the rebook, beware the BASI head-phque.
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You need to Login to know who's really who.
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| jbob wrote: |
| So this American bloke shows up for a BASI 1 course, lets call him quickbloke. He is an ex racer and really knows his stuff to say the least. |
Interestingly (or maybe not) I see quite a few young racers on BASI courses. All good skiers in the gates, and can probably carve decent turns. Surprisingly (or maybe not) quite a few of them seem very poor when you ask them to come off their edges and steer their skis by smoothly twisting them like you'd want a beginner to do when making snowplough turns, or you'd want a good skier to do when skiing steep terrain.
Good skiers can do it all on their skis. No weak spots, just good fundamental technique which can be applied to whatever conditions they want to see.
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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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| Quote: |
Interestingly (or maybe not) I see quite a few young racers on BASI courses. All good skiers in the gates, and can probably carve decent turns.
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Wonder if it would be the same with French or Austrians ?
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There's something else, beyond what I said in my last post, that I feel is important for people to clearly understand. It's something that really throws many learning skiers.
YOU DON'T CREATE PRESSURE YOURSELF! The turn creates pressure. Pressure is just a RESULT of turning. You don't TRY to apply pressure to your ski. Any attempt to do that has only a fleeting effect at adding pressure. Stand on a scale and try to increase pressure, such that the weight it registers goes up. You can, but only for a split second. Sustained pressure is the result of turning, of momentum driving a real force into the ski. The sharper you turn, the faster you're traveling, the higher the pressure you'll sense as the turning forces attempt to pummel your body into the snow. It's that pressure/force that actually bends a ski, not the skier trying to bend it.
The skier's job is only to manage the location of the pressure the turn creates. Inside or outside ski. Fore or aft. That management is where efficient/effective skiing is either born or lost.
Last edited by You'll need to Register first of course. on Fri 5-11-10 16:20; edited 2 times in total
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rob@rar, they dont always make it... on a recent L1 course one of the boy racers failed the other day. watching him i thought he sucked but he was bigging up his race background so musta done some gates at some point....
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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.
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FastMan, If I stand on a set of bathroom scale with both feet, I exert a pressure of Xlb/sqft. If I lift one foot, my weight does not change, but the pressure in lb/sqft on the scales doubles. If I do the same on skis, I am applying pressure to (hopefuly) the outside ski am I not ? By doing so, with a modern carving ski, if I stand still and do nothing else, I will turn. So I dispute your assertion.
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| deerman wrote: |
| if I stand still and do nothing else, I will turn. |
Surely you'd have to tip it on to an edge as well as standing on it?
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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| livetoski wrote: |
FastMan,
| Quote: |
Stand on a scale and try to increase pressure,
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So my tiny brain says maybe we are applying additonal weight to our skis during a turn its just that we are not exerting additional conscious pressure
OK shoot me |
livetoski, no bowing necessary, and no bullets will be used. I like that you jump in to explore what I said. It's helps get the message out.
What you're saying about "not applying conscious pressure" is spot on, and my very point. Those changes in pressure that do occur as you go through a turn are not a result of the skier consciously trying to make them happen. Rather, it's simply a result of changing turn radii, changing speeds, and changing skier orientation to the gravity force line, all natural occurrences that just happen during the course of a turn. The skier does nothing to MAKE those pressure/force changes occur, outside of shaping the turn in the manner they desire. Their focus is on producing the shape and nature of the turn they want to execute, not on creating the amount of pressure they want. Pressure just happens, a byproduct of the turn. They only manage how they distribute it across the base of their feet and skis, with their balance skills, for the purpose of achieving certain performance enhancements.
Last edited by snowHeads are a friendly bunch. on Fri 5-11-10 17:54; edited 1 time in total
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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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| deerman wrote: |
| FastMan, If I stand on a set of bathroom scale with both feet, I exert a pressure of Xlb/sqft. If I lift one foot, my weight does not change, but the pressure in lb/sqft on the scales doubles. If I do the same on skis, I am applying pressure to (hopefuly) the outside ski am I not ? By doing so, with a modern carving ski, if I stand still and do nothing else, I will turn. So I dispute your assertion. |
Thank you, deerman, you've illustrated my point perfectly through your lifting foot example of how all you control is the distribution of pressure, not the overall amount. And yes, all you need to do on skis is stand on and edge them, and they will turn. No active pressure need be applied, beyond body weight, to make it happen. You're not disagreeing with me, you're endorsing what I'm saying.
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Physics terms = Potential for semantic confusion -> Lengthy thread
Whoda thunk it?
I prefer "weight" as my layman's term.
To open a new can o worms is it easier for snowboarders to grasp the interconnectivity of all the elements given that they can't simply edge by a lateral movement but have to use heel/toe pressure to engage the edge? Rotation is undoubtably important too given the propensity to pivot rather than carve turns and as a major get out of jail card.
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You know it makes sense.
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| fatbob wrote: |
| is it easier for snowboarders to grasp the interconnectivity of all the elements [as they] have to use heel/toe pressure to engage the edge? |
I think you've answered your own question.
| fatbob wrote: |
| ... given the propensity to pivot rather than carve |
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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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Won't the pressure exerted depend on the angle and speed of the turn, almost in a similar way to centripedal force when you whang a bucket full of water around your head and the water stays in the bucket? As far as I understand it the speed you whang the bucket around and adjustment of the the radius of the circle you whang it through affects the pressure of the water in the bucket - i.e. a pressure sensor in the bottom of bucket should register changes depending on the speed and radius of the bucket whanging device. Isn't the skier the water in the bucket and the skis the bucket?
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Poster: A snowHead
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| Megamum wrote: |
| Won't the pressure exerted depend on the angle and speed of the turn, |
Yes.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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| Megamum wrote: |
| Won't the pressure exerted depend on the angle and speed of the turn, almost in a similar way to centripedal force when you whang a bucket full of water around your head and the water stays in the bucket? As far as I understand it the speed you whang the bucket around and adjustment of the the radius of the circle you whang it through affects the pressure of the water in the bucket - i.e. a pressure sensor in the bottom of bucket should register changes depending on the speed and radius of the bucket whanging device. Isn't the skier the water in the bucket and the skis the bucket? |
You win a gold star, Megamum! Well done. The skis are the bottom of the bucket, and the sensors are in the feet. Becoming aware of those sensors, and how pressure is distributed across the base the foot, is a key to developing great balance skills. Balance skills is just another term for pressure management skills.
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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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FastMan,
I've been out to do the goats (filling buckets with water!) and worked it one step further, in a given turn radius at a given speed the total pressure exterted across both skis will be determined by the amount of water in the bucket (the constant that is the skier), however, skier can alter the distribution of that pressure between the two ski's depending on what they do with the muscles in their legs and how much weight distribution each individual ski is feeling. The total overall pressure over both skis doesn't change, but the skier can alter the distribution of that pressure using their muscles and the position of their body over the skis. Yes? Well it seems to fit with FastMan's, comment to me just above from what little I understand anyway.
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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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| FastMan wrote: |
| Becoming aware of those sensors, and how pressure is distributed across the base the foot, |
Called 'feel'? No one has mentioned feel yet, but is this not a vital part of what you are discussing?
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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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Jumper,
Correct. The nerve endings involved are called pressure sensors. So we feel pressure.
As to the bathroom scales.
I stand on the bathroom scales in a nice low stance, I extend my legs and my body rises upwards. the scale whirrs and I register a higher weight. the the scale returns to the force of my mass being acted upon by gravity. If I retract my legs, the measured force will reduce for a bit and then return to normal.
Weight is a force and thanks to Isaac Newton, every action has an equal and opposite reaction. The force applied is equal to mass times acceleration. If I keep my legs still, my body remains stationary relative to the scales and there is no variation of force.
If I am going round a curve, I might try to reduce the pressure felt by absorbing the force. I could do this by bending my knees.
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You'll need to Register first of course.
You'll need to Register first of course.
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Megamum,
its a new one on me maybe you should copyright that one
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livetoski, I think that could be an example of quoting out of context 
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| Megamum wrote: |
FastMan,
I've been out to do the goats (filling buckets with water!) and worked it one step further, in a given turn radius at a given speed the total pressure exterted across both skis will be determined by the amount of water in the bucket (the constant that is the skier), however, skier can alter the distribution of that pressure between the two ski's depending on what they do with the muscles in their legs and how much weight distribution each individual ski is feeling. The total overall pressure over both skis doesn't change, but the skier can alter the distribution of that pressure using their muscles and the position of their body over the skis. Yes? Well it seems to fit with FastMan's, comment to me just above from what little I understand anyway. |
What do you mean "how little you understand"? You understand loads! That's a super comparative description, and spot on.
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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.
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| FastMan wrote: |
| deerman wrote: |
| FastMan, If I stand on a set of bathroom scale with both feet, I exert a pressure of Xlb/sqft. If I lift one foot, my weight does not change, but the pressure in lb/sqft on the scales doubles. If I do the same on skis, I am applying pressure to (hopefuly) the outside ski am I not ? By doing so, with a modern carving ski, if I stand still and do nothing else, I will turn. So I dispute your assertion. |
Thank you, deerman, you've illustrated my point perfectly through your lifting foot example of how all you control is the distribution of pressure, not the overall amount. And yes, all you need to do on skis is stand on and edge them, and they will turn. No active pressure need be applied, beyond body weight, to make it happen. You're not disagreeing with me, you're endorsing what I'm saying. |
OK, so this is a discussion where the difference between pressure and force is relevant, and FastMan is guilty of some "terminological inexactitude". By lifting the foot, the force (i.e. body weight) does not change, but as deerman says the pressure does double. The same happens on skis - the pressure exerted by that ski on the snow does double - it is a redistribution of force, but it is a complete change in pressure. This does at least two different things to the ski, if the snow has some give in it: 1) it's going to bend a lot more (if there's snow around to be displaced) 2) it's going to sink into softer snow much deeper, or will carve a deeper groove if the snow's a bit harder. Hence why you ski softer snow with a more even weighting between the two skis, to stop the outer ski going off and doing its own thing (or burying itself 2' under the snow and breaking your leg in the process), while the inner ski meanders about being chucked around by the likkle snowflakes.
| thirty06 wrote: |
I stand on the bathroom scales in a nice low stance, I extend my legs and my body rises upwards. the scale whirrs and I register a higher weight. the the scale returns to the force of my mass being acted upon by gravity. If I retract my legs, the measured force will reduce for a bit and then return to normal.
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Don't forget the other things that happen as well though. The period of registering the higher weight happens only while you are actively increasing the rate at which your body rises (i.e. the time when you are actively pushing). Once you stop that push, your "weight" has returned to normal, but your body is still moving away from the scales, and your legs are having to continually extend to match that. At some point you run out of leg length, and you can no longer even sustain the normal support of your body weight. At this point the downward force from your body, your apparent "weight" as registered by the scales, goes down and your body starts slowing down (under the action of gravity). This is how "up-unweighting" works - you give a push for a brief period of time (i.e increased "weight"), so you can get a period of lightened feet a short time later. Similarly when retracting your legs - i.e. "down-unweighting" - gives that brief period of lightness, but will of necessity be followed by a period of increased "weight" to make up the deficit. The bottom line is tha' don't get owt fer nowt - if you have a constant surface, and remain in a the long term moving a constant overall rate with respect to it, then the long term average of your apparent weight also has to remain a constant.
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FAQ
Hope/well sure I am getting in over my head here LOL
