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# 4 Questions - Page 12

Ghost, if you are going straight down the hill, you are not on an edged ski, its N/A

If you are turning, at the instant you are at the fall line, you have steering angle.  Otherwise the ski would not continue to turn.

Its not zero.

But regardless, zero or non-zero, the rear of a carving ski is not negative steering angle because the ski is not brushing at all.....its slicing.  Every point along the ski has the same local steering angle.
Quote:
Originally Posted by borntoski683

Ghost, if you are going straight down the hill, you are not on an edged ski, its N/A

It's NA to a carving ski as well.
Quote:
Originally Posted by borntoski683
If you are turning, at the instant you are at the fall line, you have steering angle.  Otherwise the ski would not continue to turn.
You are assuming falsely that the conclusion is true to try and prove a premis.

Forget what you think know, and just look at the facts of the premis.  Ski points down. You are moving down.  Steering angle is zero.  The steering angle is not defined by whether or not you are turning.  It is defined by what the direction of motion is and what angle the edge is pointing in.
Quote:

Forget what you think know, and just look at the facts of the premis.  Ski points down. You are moving down.  Steering angle is zero.  The steering angle is not defined by whether or not you are turning.  It is defined by what the direction of motion is and what angle the edge is pointing in.

The edge only matters if you're using it Ghost.  If you're running straight you are on flat skis.

I think you're just debating to debate at this point.

Get LeMaster's newest book, "ultimate Skiing" read it and get back to me.  he covers this topic in more detail than his previous book.  At this point I'm going to have to say we disagree and I don't particularly think you know what you're talking about, but you don't seem to get it and I'm tired of trying.  Good luck.
None are so blind as those who will not see.
I think you don't know what you're talking about.  And the fact that you cannot find anything wrong with my argument proves it.
I guess there's only one way to settle this.
Ghost,

At one point in the arc the body moving to the left side of the trail, and the next it is moving to the right.  At some point, it's moving directly downhill.

Same comment with the skis.

What does that have to do with steering angle?
Steering angle measured underfoot at the time the body is moving directly downhill when the ski directly underfoot is pointing directly down hill is zero.  This is an example of local steering angle that I'm hoping some people will be able to see, and finally admit the truth that is staring them in the face.

Just to show you that I am not just arguing.  I have been convinced that local steering angle as defined by LeMaster is actually applicable to a carving ski.  At the front of the ski the steering angle actually does act against the direction of motion doing negative work on the skier and slowing him down.  At the rear of the ski the negative angle does work on the skier speeding him up, and under foot, no work is done on the skier, as the force in the skier's direction of motion is zero. (sine of zero is zero).
Then what causes the steering angle to become non-zero again?
Quote:
Originally Posted by BigE

Then what causes the steering angle to become non-zero again?

Ski shape causes the local steering angle to be non-zero at tip and tial. Rotating a decambered ski about it's long axis also increases steering angle at tip and tail.
OK, but it is the local steering angles at tip/tail that turn the ski. It is the steering angle underfoot that turns the skier.

I'm not certain that for every turn I make, the direction that the skis are pointing and the direction that the CM is moving ever becomes parallel.
Now we are getting somewhere.

The sine and cosine of the local steering angle indicates how much of the pressure acting on that part of the ski is directed towards turning and how much is directed towards slowing down/speeding up the skier. At the point under an arcing ski where the edge lines up with our current direction of motion, that is to say at a local steering angle of zero degrees, sine of the steering angle = 0 and cosine of the steering angle =1 means all of the pressure acting on that part of the edge goes to turning and none goes to stopping. Should you suddenly throw them sideways, at 90 degrees, sine 90 =1 and cosine 90 = 0 means it all goes to stopping and none goes to steering.
Nice dissections Ghost!

At each moment in a carved turn the skier's current momentum can be isolated and drawn with a directional arrow.

Each microscopic, point along the carving ski's engaged edge has its own Local Steering Angle - relative to the just-mentioned direction of our skier's current momentum. (If measured against that particular point's own direction of momentum, then the Steering Angle would approach Zero instead)

At points near the tail of the ski, those Local Steering Angles just happen to point in a "negative" direction relative to our skier's overall direction of current momentum (assuming we've assign a 'Positive Value' to the Local Steering Angles near the Tip)

.ma
That's all well and good, Ghost, but these local angles only serve to turn the ski, not the skier. So when you write that these local steering angles contribute to turning the skier, you have to take into consideration the stiffness of the ski to judge their entire effect.

Lemaster throws them out entirely.  You're saying they actually matter.

The difficulty I have in making them matter is that the connection between the local steering angles at the tip and tail have to go through a flexible ski and a flexible boot/ankle system before they can actually deflect me.  Lemaster goes so far as to say the tips and tails don't turn the skier.  Only the steering angle that is created underfoot does that.

Look at it this way... if the local steering angles at tip and tail were substantial contributors, then the longer ski would turn more when carving and the snowblade would turn less.  The opposite is true.
Even further to that, since the tips and tails do little to actually turn the skier, I will argue also that the local steering angle of the tip and tail are not really related to the direction the CoM is moving (for the same reason, the tip and tail are too uncoupled from the CoM).  Rather the direction the ski tip or tail is sliding and the steering angle thus formed.  The deflection caused on that particular part of the ski. Whether or not that deflection actually has a significant effect on moving the skier is dependent on numerous factors.  How far away from the center of the ski obviously determines some of this.  How about this for a wrench in your works...if the deflection from the tip or tail are not in the same direction as the mid section of the ski, might they impart a torque force on the skier mass?  Might they actually be capable of being more effective in that way then in simply pushing the CoM as the mid section of the ski does?  Its not on or off, all or nothing either.....
1)  What are the pros and cons of being countered while steering?

Being countered allows you to create more angulation with the hip joints and use stronger muscles to resist forces.

2)  What are the pros and cons of staying square while steering?

Allows for a greatest range of movement fore/aft

3)  When is "skiing into counter" a good option, and when is it not?

Whenever the direction of the momentum that you are carrying continues into the next turn... mostly dictated by the speed you are traveling and the tightness of the arc.

4)  Is rotating, or skiing rotated, while steering ever a useful practice?

Here comes the controversy...
If you are in really deep heavy powder on a shallow slope and you are moving too slow to plane or develop any momentum from turn to turn... (Although it will not set you up optimally for the next turn) rotation will create a change in direction faster and easier... and of course if you want to do spinny tricks in the air.
Never say never!
1)  What are the pros and cons of being countered while steering?

Pros:  Counter is useful in a tuck, because it naturally puts the weight/pressure over the front of the outside ski (because of where your hands are.)   If you don't have the strength or are tiring, counter allows you to rest by resisting the buildup of forces (from change of direction) skeletally, rather than muscularly.  Counter naturally leads to a position from which you can unwind to pivot for the next turn.

Cons:  Counter leads to a "static" kind of skiing, and creates a large risk of promoting excessive inside tip lead, which leads to a host of problems.  (I have a lot of experience with the lab work that backs up that latter observation...)

2)  What are the pros and cons of staying square while steering?

Pros:  It's a more fluid, less static skiing, more two-footed and faster (in my experience, playing with it at a clinic while timed) more natural in taking advantage of a more natural gait dynamics-driven approach.  Less vulnerable to promoting excessive inside tip lead.

Cons:  It doesn't have the limited advantages of counter, listed above.

3)  When is "skiing into counter" a good option, and when is it not?

I don't know.  Seems reasonable, when carrying a tuck through the flats at the bottom of a race course, when you're tired and the counter/tuck thing is working for you.  Runs the risk of a static, less balanced, less "flow" kind of skiing, but that's less of an issue when you're setting up for a big unwind/pivot move to make the next gate.

Topic 4 is beyond me.

SfDean.
Quote:
Originally Posted by borntoski683

Even further to that, since the tips and tails do little to actually turn the skier, I will argue also that the local steering angle of the tip and tail are not really related to the direction the CoM is moving (for the same reason, the tip and tail are too uncoupled from the CoM).  Rather the direction the ski tip or tail is sliding and the steering angle thus formed.  The deflection caused on that particular part of the ski. Whether or not that deflection actually has a significant effect on moving the skier is dependent on numerous factors.  How far away from the center of the ski obviously determines some of this.  How about this for a wrench in your works...if the deflection from the tip or tail are not in the same direction as the mid section of the ski, might they impart a torque force on the skier mass?  Might they actually be capable of being more effective in that way then in simply pushing the CoM as the mid section of the ski does?  Its not on or off, all or nothing either.....

Post #284
Right.  Good!  So....let's take it even further.

In an arc'd turn we can say that we have minimized that rotational torque and maximized the turning effect on the actual skier.  If that is the case, then in an arc'd turn, the tip and tail would need to neutralize each other.   If there was negative steering angle on the tail, then they would not neutralize each other at all, they would collude together to create a pinwheel effect.  They must both be positive and they need to be similar in value also in order to eliminate that rotational torque.

In a side slip you have also eliminated the rotational torque by ensuring that both the tip and the tail cause approximately the same amount of summed up steering angle to occur on each side of the boot(front and back).  Steering angle is very large in that case, in fact its so large, with reduced edging, that its not steering the skier at all, its only producing a lot of skid.  But the point is, that there is large steering angle in the front, large steering angle in the back, and the delta between them is going to be something very close to zero.  Its not the sum, its the delta, that indicates the rotational torque.

Now then take the arcing case, We have reduced the rotational torque in this case also, but we have reduced the overall steering angle of the ski to as close to zero as we're going to get while making a turn. Whether its zero, or very very close to zero, it mattereth not in the discussion about whether there is ever any negative steering angle.  The front half of the ski and the back half of the ski need to have a very small delta between them in terms of their local steering angles.  If the front half is positive, the back half needs to be positive also.  Otherwise there will be more rotational torque.
I'll buy that for a dollar!
Quote:
Originally Posted by michaelA

Nice dissections Ghost!

At each moment in a carved turn the skier's current momentum can be isolated and drawn with a directional arrow.

Each microscopic, point along the carving ski's engaged edge has its own Local Steering Angle - relative to the just-mentioned direction of our skier's current momentum. (If measured against that particular point's own direction of momentum, then the Steering Angle would approach Zero instead)

At points near the tail of the ski, those Local Steering Angles just happen to point in a "negative" direction relative to our skier's overall direction of current momentum (assuming we've assign a 'Positive Value' to the Local Steering Angles near the Tip)

.ma
You are quite correct.  However what we are interested in is OUR change of direction, hence it is better to consider the free body as the whole package of ski and skier, as LaMaster did.  Note that the angle versus local ski direction that you are contemplating  is the skid angle that Rick came up with, also useful!
Quote:
Originally Posted by BigE

That's all well and good, Ghost, but these local angles only serve to turn the ski, not the skier. So when you write that these local steering angles contribute to turning the skier, you have to take into consideration the stiffness of the ski to judge their entire effect.

Lemaster throws them out entirely.  You're saying they actually matter.

The difficulty I have in making them matter is that the connection between the local steering angles at the tip and tail have to go through a flexible ski and a flexible boot/ankle system before they can actually deflect me.  Lemaster goes so far as to say the tips and tails don't turn the skier.  Only the steering angle that is created underfoot does that.

Look at it this way... if the local steering angles at tip and tail were substantial contributors, then the longer ski would turn more when carving and the snowblade would turn less.  The opposite is true.

And they go through flexible ankles, boots, knees and hips too!

Still, if you consider all the forces acting on the skier and his skis, you get the actual acceleration of the skier and his skis.

I'll take 165 cm Fischer WC SL skis over blades on any slalom course you care to name.

I will agree that for most people I see on the slopes the turning force at the tips and tails is minimal compared to the turning force underfoot. The force at the tip depends on how well you are carving and on how much bend you get in the ski.  Skidding at low edge angles on a soft straight ski = not much effect.
Bending a good SL ski into a tight arc   = quite a bit.
Quote:
Originally Posted by borntoski683

Even further to that, since the tips and tails do little to actually turn the skier, I will argue also that the local steering angle of the tip and tail are not really related to the direction the CoM is moving (for the same reason, the tip and tail are too uncoupled from the CoM).  Rather the direction the ski tip or tail is sliding and the steering angle thus formed.  The deflection caused on that particular part of the ski. Whether or not that deflection actually has a significant effect on moving the skier is dependent on numerous factors.  How far away from the center of the ski obviously determines some of this.  How about this for a wrench in your works...if the deflection from the tip or tail are not in the same direction as the mid section of the ski, might they impart a torque force on the skier mass?  Might they actually be capable of being more effective in that way then in simply pushing the CoM as the mid section of the ski does?  Its not on or off, all or nothing either.....

Although the direction of the ski tip and tail is different, they are both toward the centre of the turn, both acting against centrifugal force and both causing the skier to turn.
Looks like the US Marines have retaken the hi-jacked vessel!
Quote:
Originally Posted by skinerd

1)  What are the pros and cons of being countered while steering?

Being countered allows you to create more angulation with the hip joints and use stronger muscles to resist forces.

2)  What are the pros and cons of staying square while steering?

Allows for a greatest range of movement fore/aft

3)  When is "skiing into counter" a good option, and when is it not?

Whenever the direction of the momentum that you are carrying continues into the next turn... mostly dictated by the speed you are traveling and the tightness of the arc.

4)  Is rotating, or skiing rotated, while steering ever a useful practice?

Here comes the controversy...
If you are in really deep heavy powder on a shallow slope and you are moving too slow to plane or develop any momentum from turn to turn... (Although it will not set you up optimally for the next turn) rotation will create a change in direction faster and easier... and of course if you want to do spinny tricks in the air.
Never say never!

1) agree.
2) agree.
3) Acquiring counter by actively rotating the upper body is sometimes better because the counter might be needed before the skis are able to ski into counter.
4) I don't consider myself much of a steering guy, not even sure what particular version of "steering" is being referred to here, but I think there's a time and place for just about any motion you can make.
These are dangerous waters!

Quote:
Originally Posted by borntoski683

Right.  Good!  So....let's take it even further.

In an arc'd turn we can say that we have minimized that rotational torque and maximized the turning effect on the actual skier.  If that is the case, then in an arc'd turn, the tip and tail would need to neutralize each other.   If there was negative steering angle on the tail, then they would not neutralize each other at all, they would collude together to create a pinwheel effect.  They must both be positive and they need to be similar in value also in order to eliminate that rotational torque.

In a side slip you have also eliminated the rotational torque by ensuring that both the tip and the tail cause approximately the same amount of summed up steering angle to occur on each side of the boot(front and back).  Steering angle is very large in that case, in fact its so large, with reduced edging, that its not steering the skier at all, its only producing a lot of skid.  But the point is, that there is large steering angle in the front, large steering angle in the back, and the delta between them is going to be something very close to zero.  Its not the sum, its the delta, that indicates the rotational torque.

Now then take the arcing case, We have reduced the rotational torque in this case also, but we have reduced the overall steering angle of the ski to as close to zero as we're going to get while making a turn. Whether its zero, or very very close to zero, it mattereth not in the discussion about whether there is ever any negative steering angle.  The front half of the ski and the back half of the ski need to have a very small delta between them in terms of their local steering angles.  If the front half is positive, the back half needs to be positive also.  Otherwise there will be more rotational torque.

You have it right intuitively.  The back cancels out the front in terms of rotation about the middle.

Don't forget the tail is not acting like a rudder.  The force is on the rear facing surface of the ski (the base), so it turns the skier into the turn at a negative angle, while the force is on the front facing surface so it turns the skier into the turn with a positive steering angle.

It is necessary to consider rotation with a skidding ski because rotating forces are significant and changes the steering angle are paramount.  In an arcing ski, rotation is dictated by the path around the arc.  In any case, it is well to consider the rotation and the turning separately.  Consider a spinning top moving along an arc; its path and it's rotation may be related, but they are not the same thing.
Edited by Ghost - 11/21/09 at 6:58am
Who knew freighters had private security forces?
Another Pro for skiing in less countered(rotation) position = stronger more precise control over angulation due to the lower range of angulation available and alignment of bones = less chance of missing the mark and hitting the trees at DH speeds.  Not sure I've explained that well enough, but it seems that way to me.
The private security company was issued blanks, and the hijackers found out!

Consider yourself really cranking out a turn.  Your tips at the bottom of the arc are pointing frontwards 30 degrees to the east of our direction of travel, your tail edge at the top of the arc is pointing frontwards -30 degrees east of your direction of travel.  SO WHAT!  What does that negative angle mean?

Lets see.  The force slowing the skier at the tip is sine(30) times the total force on the tip of the ski or 1/2 the force at the ski tip.  The force at the tail is sine(-30) or -1/2 the force on the ski.  The force slowing the skier is negative! It's speeding up the skier.  The tip slows the skier down, the tail speeds the skier up.  Just like you though it would.  How about the turning component? cosine(30) = cosine(-30) = a positive number.  Tips and tails help the skier turn.

Why get all hung up on this zero or negative steering angle phobia?
It doesn't exist
Ghost,

What you've described is three different LOCAL steering angles.  These are the angles that turn the ski.  Since one is positive, the other negative, there must be a LOCAL steering angle of zero somewhere.

Then in the same breath, you shorten the words to "steering angle", which is NOT the same as the LOCAL steering angle, because the "steering angle" turns the skier, not the local steering angle.
Force turns the skier.  Force slows the skier down.  Force speeds the skier up.

Steering angle determines how the normal (pressure) force acting on the ski is split up into two components: one component affecting the skiers direction, and the other affecting the skier's speed.
Quote:
Originally Posted by Ghost

Force turns the skier.  Force slows the skier down.  Force speeds the skier up.

Steering angle determines how the normal (pressure) force acting on the ski is split up into two components: one component affecting the skiers direction, and the other affecting the skier's speed.

WOW!  12 pages and still going!  This is impressive even for Epic....

I only read this post, so I have no idea if there is a context....but  no Ghost...it is HOW you generate the steering angle that controls the split....the angle itself is irrelevant.
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