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Is steering/guiding without pivoting real?

post #1 of 107
Thread Starter 
Is there really a functional effect of applying a torque in the plane of a ski where no pivot results? I have no doubt about the usefullness of steering that is a combination of tipping and pivoting (mostly in off-piste terrain with various obstacles and crux's). I wonder about all the comments about steering/guiding where the ski supposedly does not pivot around it's center. I understand that it is a part of many peoples perceptions and models but I wonder if there is some objective evidence of it's efficacy?
post #2 of 107
Lito, Breakthrough On The New Skis, page 79, photo caption:
Quote:
Originally Posted by Lito
All I need to do is to progressively, smoothly flex my outside leg forward in the direction of the turn. The ski tip bites and grips and tightens the arc of my turn. A patient subtle steering action of the foot can help too, but, please, no sudden twisting.
post #3 of 107
I think it can be useful at times.

If you are scarving and you want your front edges to turn you more you need to put more weight on them and press them into the snow, but not push them to the outside of the turn. Less often you may want to do the same thing with the tails.

If you are carving you sometimes need a little extra pressure on the front edges too keep them from drifting out, and sometimes you may want to dig in the tails. With the old straight skis you went from loading the tips to loading the tails in just about every hard turn, all the while doing your best to avoid having them skid out.
post #4 of 107
Si,

Steering the skis is something that I actively do. Moving the ski, tip first with the foot and tail of the ski following both guides the ski through the intended arc (path) and also helps engage the inside edge of the ski in the snow. This allows the ski to "hook-up" sooner in the turn than merely bending it as weight is transferred, and letting the side cut do it all.

RW
post #5 of 107
Thread Starter 
Quote:
Originally Posted by Ron White
Si,

Steering the skis is something that I actively do. Moving the ski, tip first with the foot and tail of the ski following both guides the ski through the intended arc (path) and also helps engage the inside edge of the ski in the snow. This allows the ski to "hook-up" sooner in the turn than merely bending it as weight is transferred, and letting the side cut do it all.

RW
Ron,

That is the perception and model that I am referring to. When I see video of strongly steered skis (even by some of the best) it appears to me that there is a combination of a slight and gradual pivoting of the ski that combines with substantial tracking of the ski through a turn based on the mechanics of tipping. I guess there is also the case where turning occurs based mostly on pivoting of the ski with only a small contribution from a lesser tipping angle - and everything in between.

So, based on what I see and my own experience my question is two fold:

1) If there is a slight pivoting of the ski is that more or less effective than further tipping of the ski in tightening a turn. (Of course if someone is at their limit of tipping angle then it is clearly effective).

2) If there is no pivoting of the ski then what are the actual mechanics of what goes on to tighten the turn. Again in the case, if this is a real phenomena, I would ask if it is more or less effective than tipping the ski to a larger angle.

I know that SSH has previous described his model and perceptions of the second case. Perhaps he will reiterate here. Even better than perceptions, though, would be some objective evidence of what happens.
post #6 of 107
Quote:
Originally Posted by Si
Is there really a functional effect of applying a torque in the plane of a ski where no pivot results? ...
Hi Si –

In your question, two critically important and very specific conditions were implicit. Condition #1 is that “no pivot results”, and #2 is that the torque is purely in the plane of the ski.

With respect to condition #1, unless one is doing knife-edge thin RR track turns on a rock hard surface, during all other turns (ie, where a bit of sideways skidding is always present), torque in the plane of the ski will always result in slight rotation of the ski around the torque axis. At low edge angles, this will directly result in an increase in the skid or “crabbing” angle (ie, the angle between the direction the ski is pointed and the direction the ski is moving). At higher edge angles, the same will happen, but because of a less direct mechanism.

At high edge angles, torque in the plane of the ski will make the tip dig in a bit more, and the tail dig in a bit less, so that there will be more resistance to the tip skidding (however slightly) sideways compared to the tail skidding (however slightly) sideways. This mechanism also leads to an increase in the skid angle, albeit less directly than when at low edge angles. Such small changes in skid angle are important because even a change from a 1 degree imperfect skarve (ie, 1 degree away from perfect RR tracks) to a 2 degrees skarve will substantially tighten up the turn.

With respect to condition #2 that the torque is purely in the plane of the ski, in my opinion, once the knee is flexed, most less experienced skiers will tend to use a bit of femur rotation when attempting to apply torque in the plane of the ski. This will not only apply the torque in the desired plane, but also increase the edge angle, which will also tighten up the turn.

Thus, I don’t think you encounter the conditions implicit in your question very often in normal skiing, BUT, if you tell the average skier on average snow to guide the ski by applying torque in the plane of the ski, the turn will tighten up.

Tom / PM
post #7 of 107
Ahhh... I see I was typing at the same time Ron and Si were typing their latest comments. It sounds like we all have similar models / experiences. Perhaps, we should coin a new phrase, "braquage-on-edge".

Tom / PM
post #8 of 107
Quote:
Originally Posted by Si
Is there really a functional effect of applying a torque in the plane of a ski where no pivot results? I have no doubt about the usefullness of steering that is a combination of tipping and pivoting (mostly in off-piste terrain with various obstacles and crux's). I wonder about all the comments about steering/guiding where the ski supposedly does not pivot around it's center. I understand that it is a part of many peoples perceptions and models but I wonder if there is some objective evidence of it's efficacy?
Not that I'm a big fan of it, but knee angulation comes to mind imediately. Doesn't it really boil down to intent and execution? Meaning do I want to overpwer the ski/snow interaction, or do I just want to change or enhance the ski/snow interaction wihtout disloging the ski edges grip or platform in the snow.

make some pivot slips and then go out and make some carved at speed and try some of the same rotary movements in the middle of the carved turn. My experience shows that it will allow effective tightening of the turn. Femur rotation. Thighs moving like windshield wipers on a windshield. Standing over my skis versus being inside my skis produces different outcomes on my skis from my movements. Of course D.I.R.T, plays a big role here (execution). Wouldn't you agree? Later, RicB.
post #9 of 107
Quote:
Originally Posted by PhysicsMan
Ahhh... I see I was typing at the same time Ron and Si were typing their latest comments. It sounds like we all have similar models / experiences. Perhaps, we should coin a new phrase, "braquage-on-edge".

Tom / PM
Or why not just steering versus guiding? Later, RicB.
post #10 of 107
Thread Starter 
Quote:
Originally Posted by PhysicsMan
Hi Si –

In your question, two critically important and very specific conditions were implicit. Condition #1 is that “no pivot results”, and #2 is that the torque is purely in the plane of the ski.

With respect to condition #1, unless one is doing knife-edge thin RR track turns on a rock hard surface, during all other turns (ie, where a bit of sideways skidding is always present), torque in the plane of the ski will always result in slight rotation of the ski around the torque axis. At low edge angles, this will directly result in an increase in the skid or “crabbing” angle (ie, the angle between the direction the ski is pointed and the direction the ski is moving). At higher edge angles, the same will happen, but because of a less direct mechanism.

....

Tom / PM
Hi Tom,

Glad I could engage you. I hope the work load is down a bit to allow you to focus on some meaningful physics here

Of the two situations I delineated (not to be confused with your conditions 1 and 2), your response I have quoted here addresses the second and also RicB's questions:

Quote:
Originally Posted by RicB
Or why not just steering versus guiding? Later, RicB.
Rick is saying let's call my second situation guiding. However, as your quote here suggests to me, and as I think about it as well, pure "guiding" (no pivot) doesn't really exist as any "torque in the plane of the ski will always result in slight rotation of the ski around the torque axis."

So, it seems to me that RicB's "steering" and "guiding" are really only two different sections or points on a continuum.

Finally, the much more difficult issue, I think, is to get a handle on the relative advantages and disadvantages of tipping vs. torquing (in the plane of the ski). You have commented on what I think may be a key issue: When working on steering or being instructed on how to steer a ski skiers may end up increasing the tipping angle. Vice versa, increasing the tipping angle may result in an applied torque to the ski. However, in ferreting out this issue, another thing that I don't have a solid grasp on is whether the joint rotation involved in tipping really produces a significant torque on the ski or just "passively" allows the ski to follow the path produced by tipping.
post #11 of 107
Quote:
Originally Posted by Si
...I hope the work load is down a bit to allow you to focus on some meaningful physics here
LOL!!! I think things are indeed easing up. I can go into it off-line.

Quote:
Originally Posted by Si
...So, it seems to me that RicB's "steering" and "guiding" are really only two different sections or points on a continuum...
I agree 100%.

Quote:
Originally Posted by Si
...Finally, the much more difficult issue, I think, is to get a handle on the relative advantages and disadvantages of tipping vs. torquing (in the plane of the ski)...
This is indeed a very important and a very difficult issue. Unfortunately, I think it's even more complicated than you suggest: To your 2 way comparison, I think we need to add a third dimension, namely, fore-aft pressure changes. This is because the effects of torquing the tip of the ski into the snow are similar but certainly not identical to conventional pressuring of the tips of the skis. I'll respond more later tonight.

Quote:
Originally Posted by Si
...You have commented on what I think may be a key issue: When working on steering or being instructed on how to steer a ski skiers may end up increasing the tipping angle. Vice versa, increasing the tipping angle may result in an applied torque to the ski...
This reminds me of the comments Pierre made a year or two ago on the need for, but the incredible difficulty in isolating movements. I wish I could do this one-tenth as well as he seems to be able.

Quote:
Originally Posted by Si
...However, in ferreting out this issue, another thing that I don't have a solid grasp on is whether the joint rotation involved in tipping really produces a significant torque on the ski or just "passively" allows the ski to follow the path produced by tipping.
Similar to the previous comment, I think one can train oneself to minimize both the pivoting torque and the tip-digging torque that could result from tipping movements. The former needs to be reduced in any skier that hopes to carve and has been discussed b4. AFAIK, the latter is new territory.

Good topic!

More later,

Tom / PM
post #12 of 107
Si,

a ski can only pivot either if it is flat or almost flat in the snow, or if it is unweighted. A ski engaged on edge can't really pivot (it's stuck on edge).
Guiding the ski tip first into the new turn will get the ski moving in the new direction earlier than just tipping it onto edge and once the ski 's edge is engaged, it will continue to help the ski to "climb" as it decambered. A highly edged ski will climb on it's own and at that point, leg rotation will only help keep the tip engaged in the snow (the rotary will be directed more downward into the snow at that point).

Quote:
1) If there is a slight pivoting of the ski is that more or less effective than further tipping of the ski in tightening a turn. (Of course if someone is at their limit of tipping angle then it is clearly effective).
Use of rotary will get and keep the ski turning sooner than tipping alone, so it is effective to shorten the radius while tipping the ski. Once the ski is at max angle, rotary will have a minimal effect. Best when rotary and tipping are both used.

Quote:
2) If there is no pivoting of the ski then what are the actual mechanics of what goes on to tighten the turn. Again in the case, if this is a real phenomena, I would ask if it is more or less effective than tipping the ski to a larger angle.
A ski is designed to make a certain radius arc in the snow at the optimum angle. If edging is used alone, the ski will start to make a radius less than the designed radius. As the ski is tipped more on edge, the ski will start carving closer to the designed radius.
I hope this makes sense to you.

RW
post #13 of 107
Keeping in mind that all of these things blend to make the stew. Ron's post makes a lot of sense to me.
This is something that Aldo Radamus talked about back in 1984 when we were talking about "gliding" the top of the turn as much as possible. Aldo never wanted to have these types of discussions (detailed technical) but he talked of guiding the gliding skis onto thier edges.
I think this is what Harald describes as a "brushed carve".
Another thing that comes to mind, the idea that this causes the tip to engage, brings up Ron LeMasters point that the tip has a greater "local steering angle". To me that explains tightening the turn and making the tighter radius with the inside ski.
post #14 of 107
Thread Starter 
Thanks Ron,

Quote:
Originally Posted by Ron White
a ski can only pivot either if it is flat or almost flat in the snow, or if it is unweighted. A ski engaged on edge can't really pivot (it's stuck on edge).
Guiding the ski tip first into the new turn will get the ski moving in the new direction earlier than just tipping it onto edge and once the ski 's edge is engaged, it will continue to help the ski to "climb" as it decambered. A highly edged ski will climb on it's own and at that point, leg rotation will only help keep the tip engaged in the snow (the rotary will be directed more downward into the snow at that point).
RW
This assumes the snow surface does not yield - true in some cases not in others (depending on a combination of the harness of the snow and the tipping angle). The concept of "guiding the ski tip into the new turn" seems to me to be a further confounding issue. You can't move (rotate) the tip of the ski "in" without having the tail move "out. You can apply a torque to the ski without having the ski rotate, however. I assume this is what you mean by guiding. If so, my question remains what are the advantages/disadvantages of applying this torque vs. increasing the edge angle which will also tighten the turn?


Quote:
Originally Posted by Ron White
Use of rotary will get and keep the ski turning sooner than tipping alone, so it is effective to shorten the radius while tipping the ski. Once the ski is at max angle, rotary will have a minimal effect. Best when rotary and tipping are both used.
RW
Same question as above, what are the trade offs to just tipping further and increase edge angle instead? In other words how much bang for the buck to you get from applying a torque to the ski vs. increased tipping?



Quote:
Originally Posted by Ron White
A ski is designed to make a certain radius arc in the snow at the optimum angle. If edging is used alone, the ski will start to make a radius less than the designed radius. As the ski is tipped more on edge, the ski will start carving closer to the designed radius.
I hope this makes sense to you.
RW
??? The specified turning radius of a ski is for a flat ski. As you tip beyond that (given the shape of the ski) the ski continues to bend and the turning radius decrease dependent upon tipping angle (and load). I don't think there is any optimum angle for a "designed" radius only the relationship of radius to edging angle.
post #15 of 107
Quote:
Originally Posted by Si
Same question as above, what are the trade offs to just tipping further and increase edge angle instead? In other words how much bang for the buck to you get from applying a torque to the ski vs. increased tipping?
I think that there is a point at which the turn forces do not allow increased edge angle without unwanted consequences (like the ski breaking loose). That is why I think a blend works better.

However, to be clear about my own journey, I think that I have a lot of work to do on exploring the limits of tipping in my own skiing, and I am certain in that process.
post #16 of 107
Si,

Quote:
You can't move (rotate) the tip of the ski "in" without having the tail move "out.
You can move the tip inward with very little tail displacement. Remember you are sliding forward and rotation the tip inward while the foot and tail of the ski follow is different than twisting the ski from the center of its axis. You can describe a arc on the floor with your foot without your heel moving outside the arc.

Quote:
Same question as above, what are the trade offs to just tipping further and increase edge angle instead? In other words how much bang for the buck to you get from applying a torque to the ski vs. increased tipping?
I guess you won't know until you play with it. Two forces are better than one?

It takes time in the transition to get the ski flat and then reengage the edge to the point where side cut will start turning the ski, this is where some rotary steering is most useful.

Quote:
??? The specified turning radius of a ski is for a flat ski.
Incorrect, but close. The measurement of the radius of the side cut is the diameter of the circle it describes, ie: 13m. That has nothing to do with the arc it will describe while flat. The more a ski is decambered on edge, the tighter radius it will carve, and the more edge angle applied will affect that. The flex of the ski is the other factor on how much the tip will "climb". The stiffer ski has more resistance and more climbing power, where an overly soft ski will overload and not track through the arc cleanly.

RW
post #17 of 107
Quote:
Originally Posted by Si
Hi Tom,

Glad I could engage you. I hope the work load is down a bit to allow you to focus on some meaningful physics here

Of the two situations I delineated (not to be confused with your conditions 1 and 2), your response I have quoted here addresses the second and also RicB's questions:



Rick is saying let's call my second situation guiding. However, as your quote here suggests to me, and as I think about it as well, pure "guiding" (no pivot) doesn't really exist as any "torque in the plane of the ski will always result in slight rotation of the ski around the torque axis."

So, it seems to me that RicB's "steering" and "guiding" are really only two different sections or points on a continuum.

Finally, the much more difficult issue, I think, is to get a handle on the relative advantages and disadvantages of tipping vs. torquing (in the plane of the ski). You have commented on what I think may be a key issue: When working on steering or being instructed on how to steer a ski skiers may end up increasing the tipping angle. Vice versa, increasing the tipping angle may result in an applied torque to the ski. However, in ferreting out this issue, another thing that I don't have a solid grasp on is whether the joint rotation involved in tipping really produces a significant torque on the ski or just "passively" allows the ski to follow the path produced by tipping.
Well it depends on whether you want to classify by outcome, like whether the ski/snow interaction (edge grip) is being overpowerd or not, or joint movement. I'm a huge fan of teaching movements, but when it comes to comunicating all the different aplications and outcomes a movement has, don't we need to differentiat between outcomes? Seems to me both psia and HH have done just this. Rotary that breaks the edges loose, versus rotary that inflences the ski but doesn't break the edges loose.

As far as torque or passive, I see this as being the continuum, through varying the application of duration, intensity, rate, and timing. Later, Ricb.
post #18 of 107
Quote:
Originally Posted by Si
Same question as above, what are the trade offs to just tipping further and increase edge angle instead? In other words how much bang for the buck to you get from applying a torque to the ski vs. increased tipping?
I see it as having more immediate response from the skis, more continuous control of the ski, and more control over body position, versus just tipping, and the the combined effect of skiing into counter over just following the ski around the turn. Actively guiding the skis farther across the hill than the hips go. later, RicB.
post #19 of 107
Quote:
I see it as having more immediate response from the skis, more continuous control of the ski, and more control over body position, versus just tipping, and the the combined effect of skiing into counter over just following the ski around the turn. Actively guiding the skis farther across the hill than the hips go. later, RicB.
Well put, Rick!

One more point about rotary ski guidance. Pressure and edge alone is applying force away from the intended path of the ski, where active guidance keeps the movement toward the direction the tips are moving. This is especially noticeable on ice where it doesn't take much to overload the ski and cause chatter or slippage. Guiding the ski tip actually pulls the ski into the snow (ice), tip first, where pressure and edge alone pushes it off.

RW
post #20 of 107
Thread Starter 
I very much appreciate people's responses here, so thanks. RicB and Ron, what I hear you talking about are perceptions. I guess I am a bit skeptical about the effectiveness of the guidance you are talking about. In other words, I wonder whether enough torque can be applied to a ski to appreciably bend the tip of the ski (beyond the bend produced from sidecut and edge angle) when it is at sufficient edge angle to keep from breaking loose. Additionally, I still wonder about the size of the effect to be gained from applying a rotary torque to the ski vs. increased tipping (which as previously noted can also be used to differentially bend the tip when a forward bias pressure is applied or applied with equal fore/aft pressure).


It's very easy to spot steering when there is low edge angle and rotary torque actively applied. Beyond that, when the skis are solidly tracking I don't know how to objectively judge the contributions of the various inputs. Tipping certainly requires hip rotation and had I been indoctrinated appropriately I think I could be a believer in a model of my own skiing that incorporated guidance.

I guess what I am saying is that I still am looking for objective measures of the relative effect and effectiveness of tipping vs. twisting (applying a torque to) the ski. I think about an instumented boot binding pressure interface that can differentiate between a ski bringing the boot around vs. a boot bringing the ski around. That, however, is not likely to happen so I'm still on a quest for other objective measures to answer the questions I have.
post #21 of 107
I think the difference is that effect of the ski being put on edge (tipping) is compounded by the movement of the legs into the turn. It really can be very subtle, or very strong and quick. I have personaly been working on this for a couple of years and I can feel a difference and see the difference in others. To see the diffrerence, watch people who are carving from a chair lift. This perspective shows it very well, at least this is my favorite perspective. Another way to look for this is to watch for inside leg activity, also watch a skiers knees, thighs and skis (both), versus the pelvis and upperbody as they are skiing towards you. those skiers who are actively guiding and controling turn shape will show very different activety in these areas versus the skier who is simply tipping. later, RicB.
post #22 of 107
Well dang… I was actually getting some work done when I popped by to see what’s new. Now I’m getting nothing done again. Oh well. Skiing’s more important anyway.

Si, Great topic. I spent a few days last season on-snow exploring this very question. I too wondered just how much impact torque would have on turning performance for a Dynamic Parallel turn. As conditions presented themselves I tried experiments in very-soft snow, firm snow and on ‘hard’ snow (as hard as it gets around here - re-frozen day-snow late at night). Here’s what I found… (all mention of torque below refers to torque applied to an axis perpendicular to the ski base)

---
In very soft snow added torque made a huge difference. The added torque caused my ski-tips to dive deeper into firmer/denser snow further down. In soft snow the base of my ski-tip already has full-ski-width contact with the snow. When it digs deeper down, it finds thicker snow and bends more because the denser snow (deeper down) doesn’t give-way or compact as easily as surface snow.

PhysicsMan may wish to comment otherwise but I suspect the ‘forward momentum’ of my body mass (tangential to the existing turn) presses against that tip-base angle more *evenly* than when I’m on a firm surface. That is, on ice the ski twists longitudinally due to the uneven centripetal force applied only near the engaged edge - reducing the effective edge-angle (at the tip) by whatever ski-twist that occurs. This lets the front of my ski be more effective at turning me in soft snow than on ice for the same amount of edge-angle produced by boot/leg tilt. In the firmer snow (deeper down) the effect is increased because the snow there does not give-way nor compress-away so easily.

Whether my explanation is correct of not, in soft snow added torque seemed to make a big difference in tightening up my turns with no added edge angle.

---
In firm snow I found that added torque still makes a difference though not as much. As mentioned by others above the effect was along the lines of ‘Tips-well-engaged, Tails-not-so-much’. The word Scarving comes to mind. The ski-tails didn’t noticeably give way unless I overdid it. Again, this was tested with a deliberate lack of increased edge angle to see what would happen.

I got the sense that my tails were following easily in the little ruts made by weight on the center of my ski. Examining my tracks reinforced that thought. Once this rut is deeply established in firm snow, the ski-tail has to either climb up & out of it - or smoosh it to smithereens to ‘slip’ sideways out of it. Doing either (in firm snow) seemed to take quite a lot of force.

Despite trying extreme torque on my tips (my outside toe binding released once) the tails seemed quite willing to remain in the ruts unless I pushed them out with some added lateral heel thrust. At minimal edge angles my tails *did* easily slide up & over the outside bank of the existing edge-ruts. Track examination showed this clearly. The ruts still had a clean inside wall but the outside was just smooshed flat and away.

Leg-torque applied to skis with small edge-angles directs the tails more horizontally against rut walls - and therefore overcomes the rut’s guidance easily. Torque applied at higher edge-angles directs the tails more vertically and my weight on the midsection seems to hold the ski-tails down in the ruts.

I also noticed that torque applied at any edge angle on firm snow doesn’t work quite as well in lumpy terrain without conscious attention to flex & extend. With a lot of torque applied, any sort of deliberate or accidental un-weighting allows the tails to jump up and out of the guiding ruts and a partial pivot results.

---
On icy snow … deliberately added torque (from a centered position) required a lot of finesse and I couldn’t use very much without my tails skidding out. I did find that a little torque helped me keep my tips property engaged and tracking (and thereby kept my skis properly bent for dynamic parallel).

On ice, the added tip pressure from applied torque has the *undesired* effect of twisting our ski-tips longitudinally a little more than normal. This twisting of the tip delivers less edge-angle at the tip than we create underfoot via leg/boot tipping so our tips don’t have the holding power that our ski midsections have. Softer skis exacerbate the problem.

Whenever I hit a lump in the ice the applied torque helped keep my ski-tips down on the ice. So long as I kept my weight forward a bit, I found that I could keep my skis appropriately bent (from tip to boot-toe) for the given turn radius while I largely ignored the ski-tails. This let me successfully ‘ski the fronts’ of the skis rather than the whole ski while on ice. (Not saying it’s Right, just saying it’s what I found…)

Did the tails skid out while doing this? Nope. My weight on the ski midsections pinned the whole ski down and the tail obediently followed the midsections. Did I have more grip on the ice doing this? Well, I’m not sure. It depends…

When I have more weight on a shorter metal rail (ski-tip to under-foot) that rail should cut deeper into the ice… but ice has better lateral cohesion when a longer length of rail spreads a lateral force out over a longer stretch of ice… ‘Course, if the *surface* of the ice is much weaker than the underlying ice, then I’d want that shorter rail digging deeper down into the stronger ice. I guess the best grip mechanism depends on the nature of the ice.

---
My experiments with this were limited to Dynamic Parallel turns on one pair each of soft and stiff skis. The results are as objective as I could produce. I wasn’t trying to justify/discredit any particular school of thought. Just to figure things out on my own.

As to my own daily technique I do apply this kind of ‘braquage-torque’ at will. I can increase pressure on the front of my skis (to reduce turn radius) by moving my CM forward or by pulling my feet back - but this ‘braquage mechanism’ seems a whole lot quicker when I need a few extra Hit Points to attack my current turn a bit more fiercely.

.ma
post #23 of 107
Thread Starter 
Interesting test observations michaelA, thanks. Any further thoughts on tradeoffs between torque applied to the ski vs. increasing tipping angle?
post #24 of 107
Quote:
Originally Posted by Si
Interesting test observations michaelA, thanks. Any further thoughts on tradeoffs between torque applied to the ski vs. increasing tipping angle?
I just have to ask, don't both apply torque to the ski, with the difference being the axis of rotation?

For me this breaks into the relm of talking about muscle recruitment patterns and how our intent influences recuitment and how body position infuences recruitment, in particular our lower body position, the amount of flex in the hips knees and ankles. and how much anguation we are using. Also how our intent influences outcome.

For me the trades off are simply the differences between what I need to do and my ability to accomplish them. If I intend to do something, but don't quite get there, then I've lost something in the execution and traded off something in the process.

I don't know, I guess I find that the ability to effectively guide skis without overpowering the ski/snow interaction is a harder skill to learn and master than simply overpowering the ski by steering. The subtle nuances of adjusting turn shape on the fly and getting the most from the ski. Like I said earlier, this is something I have been working on for awhile, and will continue forever I guess. Later, RicB.
post #25 of 107
Thread Starter 
Quote:
Originally Posted by RicB
I just have to ask, don't both apply torque to the ski, with the difference being the axis of rotation?

For me this breaks into the relm of talking about muscle recruitment patterns and how our intent influences recuitment and how body position infuences recruitment, in particular our lower body position, the amount of flex in the hips knees and ankles. and how much anguation we are using. Also how our intent influences outcome.

For me the trades off are simply the differences between what I need to do and my ability to accomplish them. If I intend to do something, but don't quite get there, then I've lost something in the execution and traded off something in the process.

I don't know, I guess I find that the ability to effectively guide skis without overpowering the ski/snow interaction is a harder skill to learn and master than simply overpowering the ski by steering. The subtle nuances of adjusting turn shape on the fly and getting the most from the ski. Like I said earlier, this is something I have been working on for awhile, and will continue forever I guess. Later, RicB.
RicB, sorry for switching to a "short hand." Obviously you can apply a torque to the ski in three planes. I have been generally using the "long hand" and saying "torque applied to the ski in the plane of the ski."

I don't talk about tipping as a torque only because there's a good name for it. There is also a torque that can be applied related to fore aft pressure around an axis perpendicular to the ski in the plane of the ski. This is actually one that I think also needs to be included in the discussion, as it is another way, especially when combined with increased tipping, to pressure and bend the tip more selective.

I very much appreciate your point of view in terms of what you are describing you do to control turn shape. This is especially true as I have a lot of respect for your thinking based on your contributions here. The goal of my post, however, is to investigate possible differences between perceptions and reality as there are others who profess that guiding/steering does not work as effectively as a focus on increased tipping to control a turn. Unfortunately, I don't know whether the other side of the approach is going to get much advocacy in this thread. For myself, I want to ask the question and learn.
post #26 of 107
RicB,

I suggest that guiding and steering top tighten a turn does not work as well as tipping, because we've mentally compartmentalized movements like angulation to the tipping domain. Using angulation to tighten a turn is a skill that many enjoy doing much more than steering.
post #27 of 107
After reading some of the recent messages, I keep coming back to what I said in Post #6 in this thread.
Quote:
...At higher edge angles, torque in the plane of the ski will make the tip dig in a bit more, and the tail dig in a bit less, so that there will be more resistance to the tip skidding (however slightly) sideways compared to the tail skidding (however slightly) sideways. This mechanism also leads to an increase in the skid angle, albeit less directly than when {the same torque is applied} at low edge angles. Such small changes in skid angle are important because even a change from a 1 degree imperfect skarve (ie, 1 degree away from perfect RR tracks) to a 2 degrees skarve will substantially tighten up the turn...
So, let me elaborate a bit:

1) IMHO (and I'm sure I'll attract some flack for this), unless you examine your tracks extremely closely and they were made on a hard, impeccably groomed and consistent snow surface, it is usually difficult for skiers to tell the difference between a theoretically perfect carve and a skarve with a 1 degree skid angle. This is because such a small skid angle only causes the track of the tail to be displaced 3 or 4 cm from the track of the tip, whereas, if the snow is anything but rock hard, the width of even good RR tracks are usually at least this wide/deep. Add in a bit of lumpy snow, a bit of difference between the carving radius of the front and back of the skis (either because of ski sidecut or flex design choices, or because of intentional fore-aft CM changes by the skier), and you get an even wider track, but one which still looks "razor-sharp" to casual inspection, and would feel like a good carve to most skiers.

I feel this observation is important to the present discussion because it supports my the differential skidding mechanism I quoted above even when people think they are truly carving. On a real snow surface in a "carved" turn, the snow is always going to compact by different amounts as the tip and tail of the ski goes by, skis often skitter sideways by a cm or two as they go over snow irregularities, etc. Thus, torquing the tip into the snow, one of the mechanisms usually lumped into the word, "steering", has the potential to make the tip "grab more", exactly as many people in this thread have reported.

2) As has now been mentioned a couple of times in this thread, the difference between "torquing the tip into the snow" and loading the tip using more traditional fore-aft pressure changes is an interesting and important question. I feel this is a very important distinction. If you do the former, and don't move your weight fore-aft, the tip will dig in more and develop more sideways frictional force (if any degree of sideways motion is present, however small). This will clearly bring your tip around more quickly.

On the other hand, if you move your CM forward without explicitly torquing the tip into the snow or changing your edge angle, yes, the tip will once again dig deeper into the snow in the turn, BUT, the tip will now have to also provide more resistance to sideways motion given the increased fraction of your weight that is on the front of the ski. These two effects will tend to cancel each other. Thus, pure fore-aft CM moves will likely not be as effective (in some sense of the word) at tightening a carved or nearly carved turn as torquing the tip into the ground without a fore-aft CM move.

3) Si's question of whether conventional tipping vs torquing the tip into the snow is still unanswered. I think there may not be a "clean", unambiguous, works-in-every-case answer to this question. Clearly, both approaches to tighten up a carve (or near carve) work. To muddy the waters further, torquing the tip into the snow can't work if the ski is not already tipped up on edge, otherwise a torque in the plane of the ski simply pivots the ski.

I think that the postings of several people in this thread have already suggested the answer. Namely, you add torque in the plane of the ski when you are either nearly maxed out on amount of edge angle you can generate and need to tighten the carve further, especially when you need to do this quickly. Specifically, you can quickly apply torque to drive the tips into the snow without any needing large and slower bodily movements (eg, lean angle of your CM, extra angulation). OTOH, the fractional effect of this on the carve radius is probably only in the tens of percent -- it is not the major "source" of the carve. Edging is.

Anyway, that's my $0.02 on the subject for today.

Tom / PM
post #28 of 107
Quote:
Originally Posted by BigE
RicB,

I suggest that guiding and steering top tighten a turn does not work as well as tipping, because we've mentally compartmentalized movements like angulation to the tipping domain. Using angulation to tighten a turn is a skill that many enjoy doing much more than steering.
Well, BigE, I don't think guiding is a stand alone skill all it's own, viable by itself, but I also think that the best examples of skiing we see at the high end have an element of more than just tipping/angulation in them. I also differentiate between guiding and steering as I have already explained. I think most do also, but they may have different terms for them. these are psia terms from a previous tech manual, but they still ring true to me.

SI's question seemed to ask about pure stand alone tipping versus tipping plus added "guiding", which I still say has a very noticable impact on our skis. This guiding can be on the passive movement of the femurs into the turn, or more towards a very strong movement of the femurs into the turn direction, or anywhere in between. Doesn't controling this movement constitute something, and if so how do we classify adding to or taking away from the tipping/ski induced movement into the turn? What happens if we totaly eliminate this movement? What happens when we add energy to this movement? later, RicB.
post #29 of 107
FWIW, the angulation I was thinking about was hip angulation.

IMO, the "guiding" that occurs when the femurs are rotated into the turn is:

1) knee angulation when the ski is on arc, ie, is above critical angle and does not pivot.

2) steering if the ski is below critical angle, and therefore does pivot.

Si's question is different. Apparently the edge angle does not change with the applied torque, since the torque is in the plane of the ski only.

I'd like to know the mechanism of how such a force is created? It can't be femur rotation, otherwise the edge angles will change. Whole body rotation? Waist-steering?
post #30 of 107
Quote:
Originally Posted by BigE
Si's question is different. Apparently the edge angle does not change with the applied torque, since the torque is in the plane of the ski only.

I'd like to know the mechanism of how such a force is created? It can't be femur rotation, otherwise the edge angles will change. Whole body rotation? Waist-steering?
I may not be understanding your question, but couldn't increased forward pressure accomplish this?

Increasing the forward pressure at any point during a turn can, I think, cause the shovel of the ski to engage more fully, resulting in a decreased turn radius. It seems to me that a ski that is on edge and carving can be made to carve even tighter by honking on the front of the ski.

I don't know if that qualifies as "torque", but I think it definitely can result in a turning reaction without changing edge angles or rotating the femur.
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