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CoM, BoS, Centrifugal G-Force, and "Inclination" - Page 6

post #151 of 181

Thought I would give this MA a shot.

 

 

"Ahhh, good fart on deck."

 

 

"Oops ... not a fart."

 

 

"Dammit ... all down my right leg."

 

 

"If I hold my right foot up, maybe it won't get in my boot."

 

 

"I've just got to make it down and to the bathroom in this position and I will be all set."

 

Also in light of this spin move, an unfortunate release and our discussion on centripetal force I think it should be said that if he were to be able to continue spinning all the way down, centripetal force would keep the contents from moving down to his boot. Does that sound right?

post #152 of 181
Quote:
Originally Posted by justanotherskipro View Post

Whatever, MGA. You can be skeptical if you like but it won't change the fact that I do what I say I do and many many of the skiers I teach would tell you the maneuver just isn't that hard once you lose the fear of being pulled down the hill. It's really just a circus trick sort of thing. Sort of like ballet was back in the day. Anyone remember Suzie Chapstick?

In any case in spite of it moving the thread a bit out off topic I want to thank Jacques for his video and hopefully my advice will help him refine his spinning. Hey BTW Jacques one last thing, stand up more, that stance is really screwing up your fore aft balance when you bend at the waist so much. Stay neutral.


Thanks.  I like to get low so I do bend to tuck a bit.  I don't weigh much so it helps me keep pressure on the front portion of the skis.  I'll work on that.

post #153 of 181
Quote:
Originally Posted by Rich666 View Post
 

Thought I would give this MA a shot.

 

 

"Ahhh, good fart on deck."

 

 

"Oops ... not a fart."

 

 

"Dammit ... all down my right leg."

 

 

"If I hold my right foot up, maybe it won't get in my boot."

 

 

"I've just got to make it down and to the bathroom in this position and I will be all set."

 

Also in light of this spin move, an unfortunate release and our discussion on centripetal force I think it should be said that if he were to be able to continue spinning all the way down, centripetal force would keep the contents from moving down to his boot. Does that sound right?


Now that's pretty good there!  You a meme artist.

post #154 of 181
Thread Starter 

JACQUES - YOU ARE A GOOD SPORT!  In other words, now I can laugh with you.  You are also very courageous.  I am afraid to post a video here.  Now I am really afraid.

 

But because of your courage in standing up to the evil one, I will later this season. 

 

Until then, let's have a beer together!  We can invite Rich666 too. 

 

(Although, unlike Rich666, I have pledged never to use humor for evil.)


Edited by Tim Hodgson - 9/19/16 at 9:16pm
post #155 of 181

Centrifugal force is a phrase used to describe a certain types of problems in dynamics (i.e describing the motion of rigid bodies).  Essentially, the concept is a handy shortcut to solve simple dynamics problems.  It is also relatable in that one of human's sensory organs is affected by spinning motion.  The vestibular organs are filled with fluid that allows us to sense acceleration.  The nerves in our skin and joints give us feedback on compressive loads in our legs.

 

That said, centrifugal force is NOT a real force.   The real forces in current physics theory stem from the fundamental forces:

 

1) Gravity

2) Electromagnetic

3) Strong Nuclear

4) Weak Nuclear

 

 

In skiing, we (most commonly) feel: 1) Gravity and 2) Electromagnetic.  Gravity is obvious and is something we as humans "understand."  Electromagnetic forces maintain distances between molecules in stuff - ie the snow, your ski boot, the ski, etc.  A ski sitting on the ground stationary.  It is being pulled by gravity into the ground.  The electron clouds around the 'stuff' in the ski are preventing the ski from passing through the snow, and likewise, the snow is repelled by electrostatic forces on the surface of the ski.  Matter refusing to penetrate other matter happens on very short distances, unlike gravity.  These forces are driven by 2).  The other two forces are in play, but we don't really perceive these as 'directly' as 1) and 2).

 

Anyway, this is irrelevant when it comes to skiing, however, I felt compelled to post since I perceived someone to be wrong on the internet.

post #156 of 181
Thread Starter 

TexSkier:  I have two words for you:

 

"Sit back, pop yourself a cold one honey, and listen to the Michael Berry Show." 

 

http://www.iheart.com/show/139-The-Michael-Berry-Show/?episode_id=27716913

 

Free at last, free at last, free at last...


Edited by Tim Hodgson - 9/19/16 at 8:48pm
post #157 of 181

It's an xkcd battle!

https://xkcd.com/1734/

 

"Fundamental" and "real" are not the same thing.  "Centrifugal" and "coriolus" forces capture very real patterns in the movements of bodies and fluids.  

post #158 of 181

Does F=Ma?  In all coordinate systems?  Even rotating ones? Yes, if there are centrifugal forces. 

post #159 of 181

 

Quote:
Originally Posted by Ghost View Post
 

Does F=Ma?  In all coordinate systems?  Even rotating ones? Yes, if there are centrifgal forces. 


He he

 

  These are the three forces one has to make up to get F=ma in a rotating coordinate system. The Coriolis force is my personal favorite... if we're going this route, why skip it?

 

 

https://en.wikipedia.org/wiki/Centrifugal_force#Time_derivatives_in_a_rotating_frame

 

:mad 


Edited by razie - 9/20/16 at 12:06am
post #160 of 181
Quote:
Originally Posted by TexSkier View Post
 

Centrifugal force is a phrase used to describe a certain types of problems in dynamics (i.e describing the motion of rigid bodies).  Essentially, the concept is a handy shortcut to solve simple dynamics problems.  It is also relatable in that one of human's sensory organs is affected by spinning motion.  The vestibular organs are filled with fluid that allows us to sense acceleration.  The nerves in our skin and joints give us feedback on compressive loads in our legs.

 

That said, centrifugal force is NOT a real force.   The real forces in current physics theory stem from the fundamental forces:

 

1) Gravity

2) Electromagnetic

3) Strong Nuclear

4) Weak Nuclear

 

 

In skiing, we (most commonly) feel: 1) Gravity and 2) Electromagnetic.  Gravity is obvious and is something we as humans "understand."  Electromagnetic forces maintain distances between molecules in stuff - ie the snow, your ski boot, the ski, etc.  A ski sitting on the ground stationary.  It is being pulled by gravity into the ground.  The electron clouds around the 'stuff' in the ski are preventing the ski from passing through the snow, and likewise, the snow is repelled by electrostatic forces on the surface of the ski.  Matter refusing to penetrate other matter happens on very short distances, unlike gravity.  These forces are driven by 2).  The other two forces are in play, but we don't really perceive these as 'directly' as 1) and 2).

 

Anyway, this is irrelevant when it comes to skiing, however, I felt compelled to post since I perceived someone to be wrong on the internet.

Widely accepted modern theory in the last 100 years has removed gravity from that list.  And it's completely relevant, because now people can no longer ski without gravity being real.  So, it's good we know what is real and what isn't.

post #161 of 181
Quote:
Originally Posted by E350 View Post
 

JACQUES - YOU ARE A GOOD SPORT!  In other words, now I can laugh with you.  You are also very courageous.  I am afraid to post a video here.  Now I am really afraid.

 

But because of your courage in standing up to the evil one, I will later this season. 

 

Until then, let's have a beer together!  We can invite Rich666 too. 

 

(Although, unlike Rich666, I have pledged never to use humor for evil.)

 

I admit that I may not have made that joke had I thought Jacques was a poor sport as based on our past interactions. Besides, this could be good advice for anyone finding themselves in a similar predicament. Ski boots are expensive and can smell bad enough from more typical circumstances. In college I invented something called the party diaper as an accessory to the beer helmet. It was the completion to what is now a fully contained system. It hasn't done well and have only sold a few and even that was mostly for people with a pet monkey. I keep my pet monkey on a very short leash that does not reach the bathroom, so I do understand that issue. I think the idea may have more legs for skiers and especially on monster powder days. People tend to forget that like friends, there are no bathrooms on powder days.

post #162 of 181
Quote:
Originally Posted by E350 View Post
 

JACQUES - YOU ARE A GOOD SPORT!  In other words, now I can laugh with you.  You are also very courageous.  I am afraid to post a video here.  Now I am really afraid.

 

But because of your courage in standing up to the evil one, I will later this season. 

 

Until then, let's have a beer together!  We can invite Rich666 too. 

 

(Although, unlike Rich666, I have pledged never to use humor for evil.)


Thanks.  One must have a sense of humor!  It's good for one!  I gotta' admit that was funny.

post #163 of 181
Quote:
Originally Posted by Rich666 View Post
 
Quote:
Originally Posted by E350 View Post
 

JACQUES - YOU ARE A GOOD SPORT!  In other words, now I can laugh with you.  You are also very courageous.  I am afraid to post a video here.  Now I am really afraid.

 

But because of your courage in standing up to the evil one, I will later this season. 

 

Until then, let's have a beer together!  We can invite Rich666 too. 

 

(Although, unlike Rich666, I have pledged never to use humor for evil.)

 

I admit that I may not have made that joke had I thought Jacques was a poor sport as based on our past interactions. Besides, this could be good advice for anyone finding themselves in a similar predicament. Ski boots are expensive and can smell bad enough from more typical circumstances. In college I invented something called the party diaper as an accessory to the beer helmet. It was the completion to what is now a fully contained system. It hasn't done well and have only sold a few and even that was mostly for people with a pet monkey. I keep my pet monkey on a very short leash that does not reach the bathroom, so I do understand that issue. I think the idea may have more legs for skiers and especially on monster powder days. People tend to forget that like friends, there are no bathrooms on powder days.


One day I was watching a super good park skier.  He sailed large and crashed.  You guessed it.  He pooped his pants!  "S" happens!

post #164 of 181
Quote:
Originally Posted by Ghost View Post
 


One or the other.  If you fix your frame of reference to the car and have it going around the curve, you are pulled into the door, and in reaction, the door pushes back on you.  If you fix your frame of reference to the earth, the door pushes you and you, in reaction, push back on it.  The force pushing or pulling YOU is either centrifugal or centripetal, but not both.  Real forces are deduced from real accelerations of objects having mass.   We deduce gravity as a force acting between two objects by the acceleration of the objects.  Likewise we deduce centrifugal force acting on an object in a frame of reference (the car) that is accelerated with respect to another frame of reference (the earth) by the acceleration of the object in that frame of reference (the car).  A cigarette package on the dash gets accelerated to the outside door and we deduce it must be being acted on by a centrifugal force (car frame of reference).  OR a cigerette package on the dash keeps going straight as the dash goes around the curve (earth frame of reference).

So Ghost, what is the right frame of reference in terms of affecting outcome?

 

When it comes to a ski turn,  it is the edging of the skis plus velocity plus pressure management that forms the circle (arc) and hence centripetal force. I would assign this activity to the Afar Frame of Reference. 

 

The skier, in their Personal Frame of Reference is feeling and dealing with a number of forces and if they don't understand what these forces truly represent, they may react in a way that defeats their intentions. 

 

When we tip the skis to initially begin a turn, the pressure that bends the ski is fundamentally our weight powered by gravity. As velocity increases, that pressure is increasingly sourced by centripetal force. The skier (in their Personal Frame of Reference) feels the centrifugal force and may not understand that centrifugal is caused by the existence of centripetal force.

 

LF suggested that we might need a conscious "rewire" of our brain to affect this change and I think she might be on to something.  

 

When I am in a carved turn and I feel the centrifugal forces building up,  it is a signal that I am doing things right in the creation of centripetal force and not a signal that my edges are about to break free and I am going to fall on my a--.

 

As I stated in a previous post, Golf (also a circular sport) one needs to rewire their brain to understand that we are not striking the ball.... we are instead creating a high speed circular path with our clubhead and the ball just happens to be in the way.  A rewiring task that humbles us all. 

post #165 of 181

JESINSTR,

 

I guess that I have completely rewired my mind. I interpret the pressure that I feel under my feet as a push that I can use to go where I want to go. All the bending, twisting, shifting that I do is to effectively transmit this push through my skeletal system to the body in motion while at the same time regulating that push. Sounds pretty complicated when its stated that way but when I tell my students to feel their feet push them around and use this push to go where they want to go it seems to click. Don't know how much rewiring goes on but their skiing changes.

 

fom

post #166 of 181
Thread Starter 
Quote:
Originally Posted by fatoldman View Post
 

JESINSTR,

 

I guess that I have completely rewired my mind. I interpret the pressure that I feel under my feet as a push that I can use to go where I want to go. All the bending, twisting, shifting that I do is to effectively transmit this push through my skeletal system to the body in motion while at the same time regulating that push. Sounds pretty complicated when its stated that way but when I tell my students to feel their feet push them around and use this push to go where they want to go it seems to click. Don't know how much rewiring goes on but their skiing changes.

 

fom


Or maybe unsaid but implied with a JFB French Canadian accent:   THE SKI-SNOW INTERFACE IS THE INPUT.   THE RELATIVE (CONSTANTLY/DYNAMICALLY MOVING) POSITION OF THE FEET, LEGS, HIPS, SHOULDERS IS THE RESULT OF THAT INPUT. 


Edited by Tim Hodgson - 9/20/16 at 12:56pm
post #167 of 181

Here's a quote that I think summed up one of my points very well.  This is from a Caltech physicist and Nobel laureate writing for Scientific American.

 

"With general relativity, Einstein managed to blur forever the distinction between real and fictitious forces. General relativity is his theory of gravity, and gravity is certainly the paradigmatic example of a "real" force. The cornerstone of Einstein's theory, however, is the proposition that gravity is itself a fictitious force (or, rather, that it is indistinguishable from a fictitious force). Now, some 90 years later, we have innumerable and daily confirmations that his theory appears to be correct."

 

Notice how physicists tend to put "real" in quotes allot?  This is to show that we have to be careful about what conclusion we make about the word real.  In my opinion in a particular context, if it's real for all practical purposes, then it's real.  Centrifugal force and gravity are real for all practical purposes in regards to skiing.  Therefore it's not necessary to refer back to the 4-vector every time we want to describe how something falls on earth even though gravity is not real.  So, those of you that like to describe how skiing works in terms of a force pulling towards the center of the earth, great news, keep doing it, it's fine.


Edited by The Engineer - 9/21/16 at 9:10am
post #168 of 181

Of course. Skiers are undistinguishable from Guild Navigators, as they both just ride folded space and choose the safest geodesic, dodging either !@#%@#$ or trees or stars, as needed. Same thing, really.

 

By Uploaded by Frostmourne 16, from Cylon.org, Fair use, https://en.wikipedia.org/w/index.php?curid=5488806

 

p.s.

Oh well... back to the simplicity of our reality: Gravity is a centripetal force - not a centrifugal force... and the entire point was that we ski with centripetal forces, not centrifugal. Which... is still true. Gravity pulls down, snow pushes in. Seems we need both.

 

Whatever.


Edited by razie - 9/21/16 at 9:33am
post #169 of 181
Actually Gravity switches roles as we change directions. It always draws us down. But as part of that resultant where we are pulled down the hill, starting a turn it draws us into the turn and it draws us away from it as we turn away from the fall line.
post #170 of 181
Quote:
Originally Posted by TimHodgson View Post
 


Or maybe unsaid but implied with a JFB French Canadian accent:   THE SKI-SNOW INTERFACE IS THE INPUT.   THE RELATIVE (CONSTANTLY/DYNAMICALLY MOVING) POSITION OF THE FEET, LEGS, HIPS, SHOULDERS IS THE RESULT OF THAT INPUT. 

 

I believe this premise is arse-backwards. Ski to snow surface interaction [edging (skid/carve/combo) pressure management (fore/aft), turn shape (direction)] is the final result of all anatomical input starting at the feet/ankles and moving up the chain. While we all do make adjustments regarding what we feel under foot such as a unexpected loss of edge purchase or abrupt change in friction from the snow surface, there is a very limited span of time that highly mitigates its benefit to nothing more than a quick-jerk reaction to the unexpected circumstance where we employ our athletic skills of agility, balance and reaction time but not anything associated with adjustments in technique. This immediate sensory reaction dynamic pales in significance to pro-active motor patterns from pre-established technique and its adjustments from anticipation based on visual cues. The visual indications of upcoming terrain is all an experienced skier needs for anticipation that leads to actual technical adjustments. If you are too late or inaccurate with this cognitive process of anticipation, all you have left is a brainstem reaction that is solely reliant on movements that are 100% intuitive.

 

Added: When we look at a skier to determine his/her ability level, all we really need to look at is the ski/snow interaction. When we detect inefficiencies in this relationship we then look at the body to determine the underlying issues of poor ski/snow interaction.


Edited by Rich666 - 9/21/16 at 10:19am
post #171 of 181
Centripetal early, centrifugal late. Messes up the blanket statements about "always" that while so convenient, just don't hold up to scrutiny.
post #172 of 181
Thread Starter 
Quote:
Originally Posted by Rich666 View Post
 

 

I believe this premise is arse-backwards. Ski to snow surface interaction [edging (skid/carve/combo) pressure management (fore/aft), turn shape (direction)] is the final result of all anatomical input starting at the feet/ankles and moving up the chain. While we all do make adjustments regarding what we feel under foot such as a unexpected loss of edge purchase or abrupt change in friction from the snow surface, there is a very limited span of time that highly mitigates its benefit to a quick-jerk reaction to the unexpected where we employ our athletic skills of agility, balance and reaction time but not necessarily anything associated with pre-established technique. This sensory reaction dynamic pales in significance to pro-active motor patterns from technique and anticipation based on visual cues.


Fair enough.  That is why it was an "epiphany" for me. You say tomato I say reaction, you say output I say tomawto.

 

That is the main topic I got from watching the video of JFB which razie originally posted and which I summarize and post in # 30 here:

 

http://www.epicski.com/t/147474/ski-school-demo-wedge-to-parallel-video

 

If and when you have a chance take a look at the video and let me/us know what you think.

 

Because I have been thinking about it and this is why I think I like it.

 

THE SKI-SNOW INTERFACE IS THE INPUT.   THE RELATIVE (CONSTANTLY/DYNAMICALLY MOVING) POSITION OF THE FEET, LEGS, HIPS, SHOULDERS IS THE RESULT OF THAT INPUT. 

 

1.  If we think about our feet, legs, hips, (and body), shoulder position, then we are more apt to do more with them than is actually required by the ski-snow interface.  Which will cause certain things that I am guilty of including unnecessary counter, unnecessary angulation, etc.;

 

2.  Unnecessary counter, unnecessary angulation, etc. leads me to hold a foot, leg, hip, body and shoulder position too long for what the ski-snow interface actually requires to complete the turn for the snow conditions/terrain, etc.;

 

3.  Which in my skiing leads a "park and ride" or other static / non-dynamic mode of movement; 

 

4.  I wonder if focusing on the constantly ever changing ski-snow interface (Edge, Pressure, Rotation) will inform me of the true demands required of the feet, legs, hips, body, shoulders and, thus, promote more constantly dynamic movement and separation.

 

So, I understand that it is merely a "mental/body focus" type of thing (i.e., egg/chicken, reaction/action, input/output) but thinking of it that way may make me focus more on what is actually happening at the ski-snow interface and then only react in the type and amount of feet, leg, hip, body, shoulder necessary to only do what is demanded which could help me improve my personal skiing.  So I will focus on the ski-snow interface for a while, or if it works, forever.

 

Take a look at the video and let us know what you think:

 

 

 

 

 

After all, if you think about it, wasn't that the ultimate conclusion drawn from MGA's "Help with Counter" thread? 


Edited by Tim Hodgson - 9/21/16 at 11:02am
post #173 of 181
Quote:
Originally Posted by Jacques View Post
 


Thanks.  One must have a sense of humor!  It's good for one!  I gotta' admit that was funny.

 

I actually went to my gastroenterologist for a bowel movement analysis complaining of poor bum to toilet interaction that kept me from keeping up with my friends. First he told me that I need to "get forward" and resist falling into the back of the seat so that my descending colon remains properly stacked over my you-know-what. Then he told me to improve my rythm (same time daily). Most importantly, he suggested that my inputs, (Captain Crunch) was clearly affecting my output (Count Chocula). He suggested trying Lucky Charms to improve consistency. He then suggested that to keep my speed up to use a better wax bead or flax seed or something like that. Lastly, he suggested maintaining good separation of output with an arm movement pattern referred to as "the flush" and that any lack of separation would follow me around for the rest of the day. Not knowing my orientation, he left the pole plant out of the conversation. Because of my age, he suggested as video analysis during an upcoming appt. and something I will post here to get more advice.

post #174 of 181
Quote:
Originally Posted by justanotherskipro View Post

Actually Gravity switches roles as we change directions. It always draws us down. But as part of that resultant where we are pulled down the hill, starting a turn it draws us into the turn and it draws us away from it as we turn away from the fall line.

 

Quote:
Originally Posted by justanotherskipro View Post

Centripetal early, centrifugal late. Messes up the blanket statements about "always" that while so convenient, just don't hold up to scrutiny.

 

I was serious: skiers are folded space navigators... and we can also release going up the hill... what is it then?

 

The fabric of reality doesn't change between left and right turns, JASP...

 

You mean to say that it adds or subtracts its effect to the centripetal force from the snow, depending on our movement direction in different parts in the turn... That's why we use vectors.

post #175 of 181

 

From smbc-comics.com

post #176 of 181
Quote:
Originally Posted by Tim Hodgson View Post
 


Fair enough.  That is why it was an "epiphany" for me. You say tomato I say reaction, you say output I say tomawto.

 

That is the main topic I got from watching the video of JFB which razie originally posted and which I summarize and post in # 30 here:

 

http://www.epicski.com/t/147474/ski-school-demo-wedge-to-parallel-video

 

If and when you have a chance take a look at the video and let me/us know what you think.

 

Because I have been thinking about it and this is why I think I like it.

 

THE SKI-SNOW INTERFACE IS THE INPUT.   THE RELATIVE (CONSTANTLY/DYNAMICALLY MOVING) POSITION OF THE FEET, LEGS, HIPS, SHOULDERS IS THE RESULT OF THAT INPUT. 

 

1.  If we think about our feet, legs, hips, (and body), shoulder position, then we are more apt to do more with them than is actually required by the ski-snow interface.  Which will cause certain things that I am guilty of including unnecessary counter, unnecessary angulation, etc.;

 

2.  Unnecessary counter, unnecessary angulation, etc. leads me to hold a foot, leg, hip, body and shoulder position too long for what the ski-snow interface actually requires to complete the turn for the snow conditions/terrain, etc.;

 

3.  Which in my skiing leads a "park and ride or other static / non-dynamic mode of movement; 

 

4.  I wonder if focusing on the constantly ever changing ski-snow interface (Edge, Pressure, Rotation) will inform me of the true demands required of the feet, legs, hips, body, shoulders and, thus, promote more constantly dynamic movement and separation.

 

So, I understand that it is merely a "mental/body focus" type of thing (i.e., egg/chicken, reaction/action, input/output) but thinking of it that way may make me focus more on what is actually happening at the ski-snow interface and then only react in the type and amount of feet, leg, hip, body, shoulder necessary to only what is demanded which could help me improve my personal skiing.  So I will focus egg/chicken, reaction/action, output/input for a while, or if it works, forever.

 

Take a look at the video and let us know what you think:

 

 

 

 

 

 

After all, if you think about it, wasn't that the ultimate conclusion drawn from MGA's "Help with Counter" thread? 

 

I'm not a big fan of this perspective either.  In my view, the output is where we go, i.e. a turn.  Usually, when we define a system with inputs and outputs, we try to come up with one where the output doesn't change unless the input changes.  So, if the snow is the input, the output would be a skier that just skis straight down the hill.  In other words, the snow doesn't decide when you turn.  The skier decides.  The skier's input is tipping the ski and the output is making a turn.  Often systems will have the output fed back into the input, and I think that's what this perspective is really trying to describe, because as you start tipping the ski you have to feel the result and then modify.  But, feedback in a system doesn't usually entail redefining the input, it's just an algebraic modification to the transfer function.

post #177 of 181
Thread Starter 

10-4.  The Engineer:  Thank you.  When you have time would you please watch JFB's video?  Because I may have missed his point entirely.  Or I may have understood only part of it, but there is something there.  Possibly with your typical precision, you can find it and relate to me what it is that JFB is saying.  Because I don't want to misunderstand him or, God-forbid, to misquote him!

 

Maybe I have been whitewater kayaking too long.  Where the medium is moving downriver, upriver behind rocks in an eddy, vertically on standing waves and cushions, down into holes, diagonally from reactionary waves caused by a rock splitting the downriver current, etc. and we merely place our boat in the proper position on the feature and have the river do most of the rest. 

 

Including, mystifying to the untrained eye, surfing upstream on a diagonal wave to the rock creating the diagonal without paddling much if at all...

 

And remember guys and gals:  I can't ski and the bumps prove it.  So I want to learn how to ski bumps.  And watching that very cool Jerry Berg Skiing Bumps at Aspen vimeo video:

 

https://vimeo.com/43584768

 

and this JB round bumps video:

 

 

 

Look a lot more like whitewater kayaking to me than skiing.

 

But maybe it only looks like that to me because I don't know how to do it yet...


Edited by Tim Hodgson - 9/21/16 at 12:11pm
post #178 of 181

We are getting closer here. Deconstructing turns often leads us to make some assumptions to get our theories to make more sense. Or to make the task of producing a workable math model easier to understand. The worst of these is the centripetal force being the only thing we need to worry about as we ski. Second is the idea that Gravity always acts as a outward fleeing force. As Razie correctly wrote, Vectors are indeed the best way to understand how the resultant force is a constantly varying combinations of external and internal forces. Even the skills classifications use the words "pressure management" which implies a changing amount of net forces and the varying amounts of cooperation and resistance we use to create specific outcomes like a ski turn. It struck me that in TE's railroad track analogy he wrote about a need to continuously calculate and recalculate the amount of lateral accelerating forces if we used the inertial momentum and lateral accelerating forces I offered. Practically speaking isn't that exactly what we do during a turn? It may not be a conscious mental activity where we rely on math and science as much as real world experiences where we move in an almost instinctive way to manage the forces we are encountering. An opinion Vagners clearly stated in the intro to his book on the math and science of skiing.

 

We are now in excess of 175 posts and no new ideas seem to be in the offering, so even though I have just re-stated my opinion, I am seeing little value in continuing to debate this subject. I am sure this post will not be the last word on the subject but hopefully it serves to demonstrate just how folks approach the subject from their own unique perspective. For e350 and others it may help them understand the complexity of all the models offered so far and how strongly all of us feel about the subject. In the specific context of any certification tests toe the line long enough to pass the test and after that entertain all the competing ideas out there.

 

Ski season is quickly approaching and all of this stuff will quickly give way to actually making turns. Enjoy those turns.

 

JASP

post #179 of 181
Quote:
Originally Posted by Tim Hodgson View Post
 

10-4.  The Engineer:  Thank you.  When you have time would you please watch JFB's video?  Because I may have missed his point entirely.  Or I may have understood only part of it, but there is something there.  Possibly with your typical precision, you can find it and relate to me what it is that JFB is saying.  Because I don't want to misunderstand him or, God-forbid, to misquote him!

 

Maybe I have been whitewater kayaking too long.  Where the medium is moving downriver, upriver behind rocks in an eddy, vertically on standing waves and cushions, down into holes, diagonally from reactionary waves caused by a rock splitting the downriver current, etc. and we merely place our boat in the proper position on the feature and have the river do most of the rest. 

 

Including, mystifying to the untrained eye, surfing upstream on a diagonal wave to the rock creating the diagonal without paddling much if at all...

 

And remember guys and gals:  I can't ski and the bumps prove it.  So I want to learn how to ski bumps.  And watching that very cool Jerry Berg Skiing Bumps at Aspen vimeo video:

 

https://vimeo.com/43584768

 

and this JB round bumps video:

 

 

Look a lot more like whitewater kayaking to me than skiing.

 

But maybe it only looks like that to me because I don't know how to do it yet...

I definitely paused the longest thinking about bumps before I responded to you earlier.  Some people talk about great bump skiing as being able to turn wherever you want, but for me the fun is having to make that turn, because there's a bump.  So I like responding to the terrain, but I still make lots of decisions.

 

In that video, there definitely was a theme to stay fluid and dynamic such as don't park and ride.  Also, don't release too quick and don't compress into the turn.  He was making a strong point that steering is part of weight shifting which I think ties in nicely with everything flowing together.

post #180 of 181
Quote:
Originally Posted by Tim Hodgson View Post
 


Fair enough.  That is why it was an "epiphany" for me. You say tomato I say reaction, you say output I say tomawto.

 

That is the main topic I got from watching the video of JFB which razie originally posted and which I summarize and post in # 30 here:

 

http://www.epicski.com/t/147474/ski-school-demo-wedge-to-parallel-video

 

If and when you have a chance take a look at the video and let me/us know what you think.

 

Because I have been thinking about it and this is why I think I like it.

 

THE SKI-SNOW INTERFACE IS THE INPUT.   THE RELATIVE (CONSTANTLY/DYNAMICALLY MOVING) POSITION OF THE FEET, LEGS, HIPS, SHOULDERS IS THE RESULT OF THAT INPUT. 

 

1.  If we think about our feet, legs, hips, (and body), shoulder position, then we are more apt to do more with them than is actually required by the ski-snow interface.  Which will cause certain things that I am guilty of including unnecessary counter, unnecessary angulation, etc.;

 

2.  Unnecessary counter, unnecessary angulation, etc. leads me to hold a foot, leg, hip, body and shoulder position too long for what the ski-snow interface actually requires to complete the turn for the snow conditions/terrain, etc.;

 

3.  Which in my skiing leads a "park and ride" or other static / non-dynamic mode of movement; 

 

4.  I wonder if focusing on the constantly ever changing ski-snow interface (Edge, Pressure, Rotation) will inform me of the true demands required of the feet, legs, hips, body, shoulders and, thus, promote more constantly dynamic movement and separation.

 

So, I understand that it is merely a "mental/body focus" type of thing (i.e., egg/chicken, reaction/action, input/output) but thinking of it that way may make me focus more on what is actually happening at the ski-snow interface and then only react in the type and amount of feet, leg, hip, body, shoulder necessary to only do what is demanded which could help me improve my personal skiing.  So I will focus on the ski-snow interface for a while, or if it works, forever.

 

Take a look at the video and let us know what you think:

 

 

 

 

 

After all, if you think about it, wasn't that the ultimate conclusion drawn from MGA's "Help with Counter" thread? 

 

I've watched that before and will watch it again with your points in mind. I will bludgeon my skull with a heavy blunt object in advance to ensure an open mind while watching the full 23 minutes. :)

 

I agree that we are considering a number of frames of perspective/reference that are being held to a host of fluctuating variables (many of which don't even make it to the discussion) and that if someone's "thinking", whether one of a kind or something well established, helps them to make a better turn then, so be it says I.

 

On the other hand, another reason I can't go with the concept above is that the input that I believe we are discussing are the ones carrying the significance of intent. In other words the input is from the skier and skier alone. Neither the skis or the snow surface are providing this kind of input. The kind of input you are talking about is energy transfer which brings us to what I believe is the most significant dichotomy of the physics of skiing that there is and is where the rubber meets the road. That is the energy transfer from 1. the ski to the snow surface and 2. from the snow surface to the ski. You are looking at #1 which is an input of energy from the snow to the ski that is void of human intent. I am looking at #2, the input of energy from the ski to the snow surface which is an input of energy bridled with the significance of intent.

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