4 Questions

RR tracks is zero skid angle, not zero steering angle. Steering angle was defined differently before I got interested in the term.  I didn't make up the term "local steering angle" or even steering angle.  Michael quoted Ron LeMaster's book about it earlier where it is defined as edge angle versus direction of CoM.

Rick used skid angle defined as direction of travel of edge versus angle of edge, and we later sorted out how it differed from steering angle.

Skidude suggested that tip steering angle could be used to provide some description of the turning for an edge-locked carving ski.

I don't think steering angle is really that useful for edge-locked carved turns.  You aren't skidding, and tail follows tip.  Give a radius of curvature and you pretty much have it covered.  One could extend the theory LeMaster used in his book for steered turns to carved turns so that we had a unified theory that covered all types of turns, but then we would have to consider centrifugal force instead of forward momentum.  It's too complicated for what it gives us.

That is all.

What it does give you is that the part underfoot is what is turning the skier, even if the steering angle is microscopic, it's still turning the skier.

It also gives you the notion that we can modulate the pressures and edges of the ski to create a torque that turns the ski so that the ski may then turn us. 

In other words, we can use the steering angle of the ski to turn the ski so that we may turn, and abandon the whole notion of twisting the skis into the new direction to cause a turn.

Later in the text, LeMaster speaks of "initial steering angle" which is the direction that the ski is pointing in reference to the path of the CM, but no deflection has begun.  This is the pivot before the carve.

In light of the notion of the steering angle of the ski,  is it necesary to force this pivot using the legs or can we again modulate the pressue and edge to enter the turn with an appropriate initial steering angle?

There is no need to pivot before the carve.
There never really was a need to pivot at reasonable speeds; decambering took care of it in deep snow; agressive forward weight shifting could do it on hardpack.

Pressure on the middle of the ski pushing us in a direction toward the centre of curvature when we are in a turn, so do the tip and tail contribute.  The steering angle of the tip ensures that the middle of the ski will be pointing in the new direction as we move forward along the curve so that when we get there the middle of the ski will still be able to push us in a direction towards the centre of curvature. 

Quote:

Ghost, perhaps what happens is that there is a steering angle in a pure carved turn, but there is no skidding because the curvature of the ski causes the ski to be displaced along that curved path instead of skidding.  There is still a steering angle displacement which takes place, that is what causes the ski to turn at all.  The only question in my mind is whether the ski skids or not, which is part of why I think Rick set out to distinguish a difference between steering angle and skid angle.

 

Further to that, regardless of what some people think, most of us are not doing 100% pure arc'd turns 99% of the time.  Its an ideal.  You strive for it in order to increase the efficiency of the steering angle.  You are not actually acheiving it 100%.  Which means that you are always dealing with a little bit of skid angle.  According to Rick, the skid angle maybe different than the steering angle and I tend to agree.  LeMaster did not get into that kind of detail unfortunately.

  YES!  That is what I love about this discussion.  Steering does not need to thought of as a nicer word for "twisting the legs".  Twisting the legs may or may not be part of it, depending on who you talk to, but the real desire is to manipulate the steering angle through some means, be it tipping, bending, twisting, pressure control, etc.


If there is an intentional pivot entry.  

He also talks about the local steering angle, which he refers to the sidecut in the tip of the ski.  Basically, by tipping the ski at turn init, the sidecut creates a steering angle immediately.  Its no different then if the skier had pivoted the ski.  At that instant the edge of the ski, particularly near the front tip, is redirected from the line of travel, creating steering angle...albeit small.  This has the effect of starting to bend the ski and initiate the turn.  Depending on what you do with it, it could have the effect of pivoting the ski, if that is how you manipulate things, or you could try to contain that so that  a pivot entry is minimized and the ski bends into a nice arcing scenario with minimal skid.


It depends on the situation.  I do not think its ALWAYS necessary.  That's what the BPST is.  However, there are most definitely situations when a little added twisting is needed in order to go for a faster/bigger pivot then what the local steering angle will provide on its own.  On the other hand, sometimes if you twist your legs to do it when you don't really need to, you would end up with too much, when you could have relied on tipping and pressure control to obtain the steering and skidding angle you needed while focusing more on the edge control. 

I do not think this is a black or what thing.  There is a wide variety of skill blending between a variety of skills.  They can be done well or poorly, like anything else..  



Edited by borntoski683 - 11/10/09 at 6:23pm

Ghost,

LeMaster writes in context of a race course, where the course is set so that pure arc to arc turns cannot be executed.  His solution is to go deeper into the turn and pick up the arc later.  That requires the skis be pivotted to be tangent to the desired arc.

BTS,

I'm not sure if it is so easy to discard the use of the steering angle of the ski.  If you were to try, what percentage of your skiing do you think you could utilize ONLY the ski?   In Ontario, I'm only freeskiing groomed -- so to me, that figure approaches 100%.

 you lost me E.  Did you mean "skid angle"?

No.  LeMasters "steering angle of the ski" is what turns the ski,  it is different than the "steering angle" which turns the skier.  

I was suggesting that the "steering angle of the ski" can power the pivot in nearly all situations. I generally try not to twist the skis by direct leg action, unless you want to count unwinding from an anticipated position as leg action.

 
 

Oh, the other thing that Lemaster is about is that if the tips are too flexible to pull you into the turn, and only the underfoot steering angle matters to actually turn you, then it is optimal to be center balanced from initiation until release.

 I think you're still missing the point that steering angle does turn the skier.  LOCAL STEERING angle is what only turns the ski perhaps. Or maybe you're not?  I don't know you've confused me now.   

all  lemaster 

pg 22.

Look closely at the bottoms of your skis. (snip) The wax will be worn underfoot, not under tip and tail.
This is direct evidence that the big forces in skiing happen directly under your feet.  These are the forces that make you, the skier turn. The middle of the ski does the work of changing your direction of travel, largely due to its steering angle as shown in figure 3.6a. (cut to pictue highlighting the steering angle of the ski's midbody) The tip and tail are simply not stiff enough to push  very hard on you, and therefore don't have enough force to make you turn.(snip) What do they do then? They make the ski itself turn.
 
diagram 3.6b shows the local steering angle -- essentially the angle between straight down the middle and the direction a tangent to the edge at the shovel. 

pg 24
It is a "local steering angle that brings a reaction force from the snow against the tip that makes it turn slightly as it moves forward.  This in turn creates a small local steering angle in the skis midbody which brings a reaction force that changes the skier's direction fo travel.

 yes, I read all of that too.  What is your point, I still don't understand.

It was as simple as suggesting that given the steering angle of the ski, and the effects of the local steering angle of the tip, that actively pivoting the feet by applying a rotary force from the leg is largely irrelevant.  

The question of what percentage of your turns could be accomplished by use of the skis steering angle is being made to put the comment about the times you really need to actively pivot your feet in perspective.  

It seems like just needing to actively pivot once is enough to marginalize any technique that relies on the steering angle of the ski.  Even techniques that are supported by LeMaster.

 I don't know about you, but I hit situations ALL of the time where the local steering angle is not enough.  On the flip side I see people all over the hill twisting their legs around when they could develop steering angle in more effective(perhaps) ways.  Its kind of a silly question. The need comes up.  10%, 20%, 80%....does it matter what the answer is?  its not 0%, that much I am sure.

The bolded parts are worth a little extra thinking about.

How much pressure is at the tip and tail depends on how much the ski is bent, and how stiff the ski is.
Bending a 13 m ski into a 12-m carved turn won't put too much stress on the tips cause the skis won't be decambered too much.  Skidding a steered turn with any ski at a relatively low edge angle won't do a heck of a lot of bending to the ski either.

You can think of a ski as a beam supported by a single column in the middle.  The load on the ski corresponds to the shape in the same way as piling concrete blocks on the beam would make it bend.  Note that you can pile a heck of a lot right on top of the column without changing the shape of the beam.  The total load on the beam is the total force pushing you into the turn.  The more the ski is curved, the greater proportion of that load is in the tip and tail. 

here's just one scenario where local steering angle isn't going to help you:  your skis are airborne during transition.

 

I actually do think you are perhpas onto somthing here...but what is the point beyond and academic one?

BTS:  True.  I'd rely on unwinding.

But that is what transition is..instant between one turn and the next..no turning is occouring at this moment in time.   And as you think you are aluding, no steering angle.  Once the steering angle starts, so does the new trun.

 ok, anticipation I agree is a MUCH better solution then twisting the legs.  I'm just saying, don't rule it out entirely.

The point BigE is trying to make is that you don't need to provide rotary forces from your legs in order to develop steering angles.  What I am saying is that sometimes, the rotary efforts will still be justified if for whatever the reason the local steering angle effect is not going to be as big or fast as required.  Could be that you just need to turn NOW.  Or maybe you're not anticipated, now what?  Could be that you're airbone and so you won't be able to get the local steering angle effect until later than you need.  Could be that you simply need to turn much more abruptly than will be possible.  Turn entry pivots?  What are those?

 

These are all valid scenarios.

Could also be that you INTENTIONALLY want to create more steering angle on purpose in order to get some of that skid angle butter spreading.


 

 

Interesting.... normally  the transition is not thought of as an airborne thing.....

You mean braking?

Quick summary....

- The steering angle of the ski is its side cut
- The local steering angle is the side cut of the tip
- Steering is whenever the ski is turning
- Skid angle is the angle of the ski skidding over the snow
- Skidding is whenever there is a skidding angle
- Carving is whenever there is no skidding angle

If this is how you guys define steering you are totally leaving out any kind of movement made by the skier. I thaught that steering was all about "turning the feet" to over-ride the sidecut. The side cut can also be over-ridden by simply going too fast for the edge angle or by a turn initiation involving un-weighting to help deflect the skis. Anyway, steering kind of looses its meaning since there is a big big difference between carving and skidding. To me it looks like you guys only want to replace the word turning with steering.

IMO you guys need to change the definition of steering and expand it to Active Steering and Passive Steering. Active would be the muscle input made by the skier to turn the skis and passive the skis performing. For example if you actively tried to turn the skis AS while carving you would be driving your knees into the turn without overriding the skis. If you wanted to passivley turn the skis PS then you would let the skis react and perform to other than turning movements such as tipping, angulating and countering according to the TGIF consept. Simple as that

There is a missconseption regarding carving vs skidding. But that is only because carving is defined differently. There is no unified definition. Before carving there was only skidding except for some special cases in racing and big arcs. The small arc carving skis that came out in the late 90s and really made a brake through during the mid 00's gave the skier a possibilitie to carve also smaller arc turns. Before this everyone was skidding their turns. But, good skiers were able to evenly skidd their turns while beginners and lower level skier were struggling with wind shield wiper turns and all kind of funky stuff. Now when carving came along people seem to forget how it was back then and I dont blame them, many of us were not even born then. Back then good skiers were brushing their turns just like they are now with the exception that the skis were harder to turn and more input by the skier was needed. That took skill. That skill is now lacking. Except that its now being re-born as carving. Brushed carving. I bet Rick has his story on this.

Quote:

Off the top of my head I can't think of any other reason to want to skid other than perhaps because you  need to turn tighter and slowing down from skidding is an unavoidable consequence.


no, Steering angle is not the side cut, though sidecut can contribute to it.  Its been explained in the this thread a few times.  Read again and/or get LeMaster's book.  Local steering angle is a bit more broad than just the tip I think, but what I read it was used only in reference to the tip.  I think the general consensus of this thread so far is that local steering angle may have to do with the steering angle effecting one particular part of the ski, as opposed to the overall steering effect on the skier.  But don't quote me on that please.



brushed carving is a very high level skill and yes, a lot of people today are clueless because they have not really learned that skill.  They can edge lock arc or swivel around, but have no idea whatsoever what it means to truly steer a turn.  That is my opinion.

 

 BTS: re local steering angles are everywhere.....

pg 24
It is a "local steering angle that brings a reaction force from the snow against the tip that makes it turn slightly as it moves forward.  This in turn creates a small local steering angle in the skis midbody which brings a reaction force that changes the skier's direction of travel.

If I'm reading this right, it's the local steering angle under the mid-body that does the turning.  Pretty cool I think.  

I agree completely with your opinion on brushing the carve.  I'll hazard a guess as to why that is so... It's because the focus on outcomes ignores mechanics.  

Brushed carving is considered skidding through a turn, that if you were a better skier, you'd carve instead.  Skidding through a turn is considered an elementary "problem" that resolves itself over time.  

Zero attention is paid towards staying centered and making the skis do the pivoting for you.  A lot of attention is paid towards staying centered and twisting your legs.  To my view, an entire skill set is being abandoned.


Edited by BigE - 11/11/09 at 7:43am

I've been thinking about this.....it's only correct if you end the turn in a traverse.

On exit from the old turn, the CM is moving across the skis.  This means that the direction the skis are pointing and the CM is moving is different.  There is a steering angle present.  Even as the ski goes flat, a steering angle will be present.  Due to the lack of edge engagement it will have no effect, but it will still be there.

In thinking about the notion of the negative steering angle just choose one side of the ski to have positive angles, the other negative.  So, if my skis are pointing to the right side of the path of the CM, the steering angle is positive, if left it is negative.  Skis aligned with CM is zero.  It is arbitrary, but more correct that saying a 1 degree steering angle can turn you either left or right.