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Angulation vs. Banking - Page 5

post #121 of 148
Quote:
Originally Posted by borntoski683 View Post
Interesting dilemna isn't it? If you go faster the critical edge angle requirement will increase, but you have a given turn radius you are trying to accomplish, except faster now.
This is why you see racers moving straighter toward the gates. They are going fast enough to require that higher edge angle, and producing arcs to match it. In modern GS this is not a huge problem as the courses seem to be getting tighter and tighter all the time, so if you can achieve those higher angles and tighter turns you will be better off. The problem is that the strength that it requires to keep these turns up for 2 minutes is not an ability that a lot of skiers possess - due to the huge forces that the skier is subjected to. In a perfect world the critical edge angle and the desired turn would match each other... but they don't always [ever]. Usually, you need to make a tighter turn - not a longer turn... This is what makes ski racing difficult.

Later

GREG
post #122 of 148
Quote:
Originally Posted by borntoski683 View Post
Interesting dilemna isn't it? If you go faster the critical edge angle requirement will increase, but you have a given turn radius you are trying to accomplish, except faster now. I guess that is why they make GS and downhill skis Ghost. ;-)
The same thing happens when you exceed the critical angle on the SGs as on the SL. It's just a little more exciting at higher speeds.
post #123 of 148
I dunno, but this was a stupid thread when I started and the skulls are thick around here. later.
post #124 of 148
Quote:
Originally Posted by borntoski683 View Post
No matter what speed you are going, if you don't want to skid you must always have the skis at the critical edge angle(or more), whatever that angle happens to be at any given moment in time.

At slower speeds the critical edge angle requirement is reduced. You frankly don't really need any more angulation going slow then you do going super fast. There may be other factors at play such as the wrong ski for the job,. This is why slower skiers go for SL sidecut skis so that they can turn sharper, going slower with less edge angles. There are other factors also at play such as how easily the shovel of the ski will bend.
Or get longer radius skis so that you can make the same size turn at a higher speed with a bigger edge angle (bigger than critical).
post #125 of 148
yes, that is what I meant when I said the reason they make GS and downhills skiis Ghost.
post #126 of 148
Quote:
Originally Posted by borntoski683 View Post
Excuse me Max, when did this turn into a pissing contest?
I'm sorry, I'm just a stinker sometimes.
post #127 of 148
LOL, I didn't see it that way at all. I too would like to see video of people taking turns at the limit free skiing. If anybodys got some, post up!

Unfortunately when I go skiing, I just go skiing, I don't go "movie making". I did take a gps along a few times.

Sorry max, maybe you can check to see if Blue Mountain has any recordings from their web cams of Dec. 30. 2005. I have GPS of maxing out the WC SCs, but No GPS maxing out the SGs (the batteries were dead).

http://forums.epicski.com/showthread...ighlight=devil
post #128 of 148
[Sidebar On]
I disagee with the idea that this is a 'stupid thread'.

I've been mulling over recent threads expressing concern for the dilution of ‘quality instructional content’ on EpicSki - then, this one pops up.

Obviously it'a a matter of opinion but I think this is quite a good instructional thread with high-quality posts from a Mentor-Class participant… and it's kinda nice to get back into meaningful discussions - especially with a knowledgeable participant coming back after every few posts to re-rudder the boat with clarifications, expansive content, polite conversation and respectful debate. I don't think a thread becomes 'stupid' just because people present information I might not agree with.

On the expressed concerns for Constantly Recurring Questions - well;
1) New participants are popping in all the time (unfamiliar with old threads)
2) Long-time participants may have missed previous discussions
3) New ideas develop and/or new perspective are expressed
4) Bob comes up with new Animations we aint seen yet
5) Old ideas are re-worded into even better presentations of the original idea
6) Sometimes, the old Adamant Dissenters of yesterday have evolved into the new Adamant Proponents of today

In any case - I think this evolved into a pretty good discussion…
[/Sidebar Off]

.ma
post #129 of 148
Potentially relevant thoughts

When discussing Centrifugal force... with respect to skiers we should remember that this force is not restricted to the ‘Horizontal Plane’. A skier making turns down a 30-degree slope experiences Centrifugal force (generally) in the Plane of the Slope. Bob’s diagrams can be drawn from a horizontal perspective (in this sense) and still be an accurate depiction (in general) for the same turns on a steep slope.

Critical-Angle: I’ll leave it to Bob to clarify his own definition for this if needed - but to clearly follow his reasoning I suggest readers use Bob’s definition rather than debating from ones own definition (as has already occurred earlier in this thread about inclination and banking). My own interpretation of Bob’s ‘Critical Angle’ discussion is largely in agreement with everything I’ve come to understand about ski-snow interaction.

---
Regarding the discussion about increasing the speed of the skier for a given turn radius…

Increasing the skier’s speed in the turn (in isolation of other changes) *rotates* the Resultant Force Vector (originating in the CM) to a new angle - one pointing further to the outside of the turn. This *does not* change the Critical Angle as defined by Bob - because that angle is defined as being 90-degrees from the Resultant Force Vector.

If you change the context (and thereby, the RFVector) you automatically move the Balance Point/Line of Action along with it. Once the Line of Action is re-located - the Critical Angle of the ski at that point on the snow is re-established. I see no disparity.

Changing Speed, changing Radius, or changing Mass will *not* change the Critical Angle the base of the ski needs to have in relation to its supporting surface. Changing these things *may* require a lateral change in CM location in relation to the supporting ski(s). But once you adjust the CM’s location - the Critical Angle (measured as defined) once again accurately depicts the necessary base angle of the ski. (or perhaps I should say, "...Of at least one ski." )

Momentum:
In the sense of *Pressure* - a skier's momentum will make a difference in Bob’s diagrams (as drawn) so I think there are some general assumptions implied about the skier's overall technique.

The skier who largely releases their CM (laterally) sometime just after turn apex may allow their upper body to flow ‘ballistically’ across their skis into the new turn. Such a skier will experience different degrees centrifugal force at different points in the turn than the skier who progressively ‘guides’ their upper body Mass out of the old turn, across the hill - and then into the next turn.

I believe this is relevant because ‘Centrifugal Force’ is proportional to the turn Radius and Speed of the Mass that is moving along that radius* (which is what the drawings portray).

This *wouldn’t* be entirely accurate if our skier has made that big lateral move across the skis.

In such a case there would be very little centrifugal force to work with at the skis during turn-entry (just that generated by the skis and lower legs - because the skier's upper-body mass is on a different trajectory). Active leg-extension helps re-attach our upper body mass to this equation but our range of extension is limited.

If the skier’s upper body moves more closely along the path of the skis (arcing across the hill) then the depicted diagrams work very well.

.ma
post #130 of 148
You guys need to relax. I'm not trying to pick a fight. Just getting the facts straight. I'm glad to hear Bob meant to say that his understanding of critical edge angle is 90 degrees to the resultant vector. That was the least important point I made above, so don't dwell on it. Its defined best by LeMaster p19 for curious minds.


Quote:
Originally Posted by michaelA View Post
When discussing Centrifugal force... with respect to skiers we should remember that this force is not restricted to the ‘Horizontal Plane’. A skier making turns down a 30-degree slope experiences Centrifugal force (generally) in the Plane of the Slope. Bob’s diagrams can be drawn from a horizontal perspective (in this sense) and still be an accurate depiction (in general) for the same turns on a steep slope.
Yes, but you are now overlooking gravity, which adds to the slipping forces when you are in the bottom of the turn because it combines with the centrifugal forces in a more similar direction then earlier in the turn, due to the slope of the hill. The first diagram above is representative of what things are like at the apex. After the apex, you can expect the slipping forces to increase, thusly requiring more edge angle if you don't want to skid.

---
Regarding the discussion about increasing the speed of the skier for a given turn radius…

Quote:
Changing Speed, changing Radius, or changing Mass will *not* change the Critical Angle the base of the ski needs to have in relation to its supporting surface. Changing these things *may* require a lateral change in CM location in relation to the supporting ski(s). But once you adjust the CM’s location - the Critical Angle (measured as defined) once again accurately depicts the necessary base angle of the ski. (or perhaps I should say, "...Of at least one ski." )
Get Lemaster and read it. You are not understanding the physics properly. ANYTHING that will cause the resultant force vector to change may change the critical edge angle required. changing the radius will effect the centrifigal forces and thus will effect the force vector. Moving your CM relative to your skis through angulation or banking, etc. does not alter the resultant force vector one bit or the critical edge angle. It merely changes your balance point, are you balanced on the outside ski, the inside ski, some point between them or are you losing balance because you are angulated too little or too much?

The fact that the slope changes relative to your direction of travel is interesting because though the force vector has not changed...the direction you are sliding in relation to that force vector definitely has changed all the way through the turn, just like Bob's animated GIF earlier. Regardless of the slope, your skis need to be 90 degrees from the resultant vector, which means that if the slope is changing, the actual angle your skis make on the snow will be changing as well if you were going to try to maintain exactly the critical edge angle.
post #131 of 148
Quote:
Originally Posted by borntoski683 View Post
Yes, but you are now overlooking gravity, which adds to the slipping forces when you are in the bottom of the turn because it combines with the centrifugal forces in a more similar direction then earlier in the turn, due to the slope of the hill. The first diagram above is representative of what things are like at the apex. After the apex, you can expect the slipping forces to increase, thusly requiring more edge angle if you don't want to skid.
I think Michael understands the physics, though if you don't already know what he means it's probably hard to understand what he's saying.

What must be remembered is that the "critical" angle is the angle that cannot be passed, not the angle the skis are at. The skis only need to be put on a bigger angle to avoid skidding after the apex if the angle they are already at is the critical angle putting the skis right at the point of skidding in the apex. Equally possible is that the added force, due to gravity now adding to centrifugal force, brings the situation closer to critical at the end of the turn which is continued at the same tipping angle and radius. Comparing a vector diagram for the end of the turn to the apex of the turn, would again mean a longer "x-direction" arrow representing the centrifugal force and the outside-directed component of gravity, a shorter "y-direction" arrow representing the to-the-surface component of gravity, but the resultant still passing through the inside edge of the outside ski - again less angulation, closer to the critical state.

From the born2ski's arguments, I do think b2s understands the skiing. He is intuitively tipping the ski more so it maintains it's grip and transitioning into the new turn with a solid cross-under. Said transition not putting the full centrifugal force to the ski as his cm is not following the arc at the end of the turn, thus NOT forcing the skis out of their groove. That is a good move if the next one is a turn in the opposite direction, not so much if this is a chute between cliffs with one turn in it.

Intent governs the correct action.
post #132 of 148
Quote:
I'm glad to hear Bob meant to say that his understanding of critical edge angle is 90 degrees to the resultant vector.
Meant to say? BTS--I don't think I could have been any clearer about this, between the text of my posts, the illustrations, and the caption in bold on the Critical Edge Angle illustration.

But what do you mean by "critical edge angle requirement," and what do you mean by this statement:
Quote:
even though the increased inclination has increased your edge angle, the increased speed has also increased your critical edge angle requirement.
Again, I don't know what you mean by "critical edge angle requirement," but by your own words (which are accurate), critical edge angle is always 90 degrees from the resultant force. As I have both illustrated and described, the angle of the resultant force can and does change throughout turns, but 90 degrees to that line remains the unchanging magic number. (Of course, to be obsessively accurate, 90 degrees isn't quite right. Base edge bevels and torsional flex combine to make the actual angle needed somewhat more acute, but 90 degrees is close enough for discussion purposes.) Whatever the actual angle, it does not change with increasing speed or inclination.

Increased speed in a given turn will increase your "inclination requirement," if you will, tipping the resultant force line further from vertical. But critical edge angle remains 90 degrees from that line--as easily achieved with subtle ankle tension (angulation) when heeled way over as when standing still and upright. No more angulation is needed to attain critical edge angle in either case. (Of course, this assumes properly set up and canted boots, in both cases.)

And then what are we to make of statements like
Quote:
". . . which requires adjustment of the critical edge angle relative to the surface of the snow,"
when you have just insisted (and I have agreed) that critical edge angle is not relative to the surface of the snow?

It is worth noting, in any case, that "critical edge angle" tells only part of the story. As described, it is the theoretical minimum angle (with respect to the resultant force applied to the skis) that will cause that force to push the ski into the groove it cuts in the snow. Anything beyond 90 degrees, and the force actually pushes the ski out of its groove, as my animation shows.

Some like to argue that more angle will not help the ski hold better. I myself have described how too much edge angle can actually cause a ski to hold less well. And that is still true.

But what about the case where the ski is already skidding, and therefore not cutting a little groove in the first place, but the skier is trying to control the skid and get the ski to hold or shape the turn? For most skiers, most of the time, this is the normal situation, while the clean, locked-in carve is the exception. Here, the math is a little fuzzier and less absolute. Here, there are more variables, but the more you can tip the ski with angulation (within reason), often, the better it will grip.

If it was simple, it would be boring!



Best regards,
Bob Barnes
post #133 of 148
Quote:
Originally Posted by Bob Barnes/Colorado View Post
And then what are we to make of statements like when you have just insisted (and I have agreed) that critical edge angle is not relative to the surface of the snow?
Let me break it down again.

If your resultant vector is changing relative to the surface of the snow, then the edge angle of your skis relative to the snow must also change. When we are skiing, I don't know too many people that are visualizing gravity force vectors and centrifugal force vectors. We are sliding down a slope, that is our frame of reference. Within that frame of reference, the critical edge angle requirement can and does change as the resulting force vector is changing too. This means the skis on the snow, in our frame of reference will not be at constant edge angle.

I don't understand why you're being so defensive and hostile Bob.

Anyway, you guys have tired me out and I give up along with BigE. Go ski however you want.

BTS
post #134 of 148
Heh - my comments about centifugal force and the Plane of the turn were specifc to the CF component sans that of gravity. I wasn't 'overlooking' gravity (though it frequently overlooks me).

---
I'd initially written some comments on 'canting' but deleted them before posing as I thought it too much of a tangent - but since Bob went there...

My Canting Thought: Under-canted skiers will find their Outside-Ski engaging much later at the start of a turn and releasing much sooner at the finish of a turn. Often a skier will be able to tip their ankle and roll the boot a good deal to the Outside-Edge - but will not be able to roll their boot onto the Inside-Edge very far. Managing that Critical Edge angle becomes much more difficult for people with this issue (I know because I’ve had this problem - until messing with my boots a lot).

I think it’s important to this discussion since we make minute adjustments to this Critical Angle by rolling our ankle inside the boot *without* moving our CM laterally - nor changing overall angulation higher up in the body. We can make such adjustments regardless whether we are Banking or Angulating - and regardless what our degree of CM inclination might currently be.

---
A more interesting direction to explore:
What if the skier's Outside-Ski is at an angle LESS than the CA - but the Inside-Ski is at an angle that is slightly greater than the CA...?

What if the 'line of action' from the CM points at the snow midway between the skis...?

What if the skier maintains a 'Rigid structural frame' connecting their legs thru their pelvis...?

*Now* - does the skier skid - or do their skis hold?

.ma

(PS: This directly relates to a thread about 'Carving on Ice' a while back - where we proponents of 'distributed weighting' were at odds with proponents of Outside-Ski-only weighting. So: Consider the idea above on an Icy surface.)
post #135 of 148
Quote:
Originally Posted by BTS
If your resultant vector is changing relative to the surface of the snow, then the edge angle of your skis relative to the snow must also change.
This sounds reasonable if you envision a *firm* and continuously even (flat) snow surface.

But if you envision a very lumpy, uneven surface (cut up crud) or deep soft snow - it becomes *unimportant* what the ski's relationship to the snows surface angle is. All that matters (to keep the ski from 'migrating' outward *or* inward) is that the ski's base angle be 90-degrees to the RFVector.

Subsequent Edit:
Quote:
Originally Posted by BTS
This means the skis on (or IN) the snow, in our frame of reference will not be at constant edge angle.
(Bolding Mine) I see where you're coming from and agree that relationships are always changing. Still, while I'm skiing well I perceive (from my own frame of reference) that I'm always "standing" firmly on a 'flat' pair of skis - the platform feel we freqently tell our students to seek.

.ma
post #136 of 148
BTS--there is no hostility here, although I'll admit to a little frustration due to your arguing with me without, apparently, having paid much attention to what I've actually written. It was an honest question. I'd still like to know what you mean by "critical edge angle requirement."

It appears to me that, while you are rightly adamant that "critical edge angle" is measured with respect to the resultant force vector, you have in fact used the term often to describe edge angle on the snow surface. Clearly, that is what you mean when you say, "This means the skis on the snow. . . will not be at constant edge angle." No argument there. But you can see why it is confusing when we both agree that CEA is independent of edge angle on the snow.

However, if you do mean simply that edge angle on the snow (not critical edge angle) must, without exception, increase throughout the turn, then I still disagree. That is the main point of my discussion of "progressive de-angulation." As I described, several factors conspire to increase the edge angle on the snow as the turn progresses--increasing relative slope angle (slope tips increasingly away from skis after the fall line), and increasing inclination due to rising speed and to gravity pulling progressively more out of the turn, all compounded by the tightening radius that the increasingly edged skis carve. It can be a vicious cycle--the more the skis tip, the tighter they carve, requiring more inclination, which tips them still more. . . . until they blow out of the turn! It happens often, and skiers often react by trying to tip the skis even further!

But good skiers have a weapon to counteract, or at least mitigate, this syndrome--IF they give themselves permission to decrease angulation and "bank" a little as needed as the turn progresses.

Dogmatic belief that we "should" increase angulation throughout the turn often just adds to the problem.

Skillful use of inclination and angulation allows a skier to control edge angle both with respect to the resultant force on the skis and to the snow surface, over a fairly large range, for independent control of both carving radius and grip. As the turn progresses, decreasing angulation can compensate for increasing inclination and relative slope angle, at least to a degree (limited by critical edge angle--we cannot de-angulate beyond that critical 90 degrees without slipping). The common belief that skiers "should" increase angulation throughout the turn takes away this very important technical option, many times causing them to do exactly the wrong thing.

It is not necessarily "better" to de-angulate (bank more) in a turn, but it is certainly possible. It may conflict with still-common conventional wisdom, but I'm here to say--it's OK to do it when needed (and I recommend it).

Of course, anyone who doesn't want to doesn't have to.

Best regards,
Bob Barnes
post #137 of 148
Quote:
Originally Posted by borntoski683 View Post
If your resultant vector is changing relative to the surface of the snow, then the edge angle of your skis relative to the snow must also change.
I disagree with this statement.
post #138 of 148
So do I!

post #139 of 148
If you can't control (increase or decrease) the edge angle of your skis at any time at will, even when out of balance, and regardless of the angle of inclination, then there are some edging skills that need work.

Best regards,
Bob Barnes
post #140 of 148
Quote:
Originally Posted by Bob Barnes/Colorado View Post
Reverse Camber, a function of edge angle on the snow.
The angle at which the ski is directly related to the radius of the turn being made. The turn radius is equal to the sidecut radius times the cosine of the tipping angle. If you are making a turn of a given radius, you can only have your skis tipped to one tipping angle with one pair of skis.

Now let's talk about "critical" angles. You are able to carve any radius you like less than the sidecut radius of the ski provided that the tipping angle required to make the turn (between the snow and the ski) is Greater than some critical angle. Any turn being made with the skis tipped at a greater angle to the snow than this "critical" angle will carve. This critical angle requires that the ski be perpendicular (90 degrees) to the line of action of the net force applied to the ski. The ski will carve if the ski is tipped so that the angle between the ski and the snow is greater than the angle which would be required for the ski to be perpendicular to the line of action of the force. THE SKI DOES NOT NEED TO BE AT THE CRITICAL ANGLE to carve a turn; it can be at any angle so long as the angle between the snow and the ski is GREATER than it would be at the critical angle.
post #141 of 148
Quote:
Originally Posted by Bob Barnes/Colorado View Post
H

The skier in the above photo is inclined at about 25 degrees to the snow. The line of action of the force applied to the ski must pass through his cm, so the critical angle would have his skis at 65 degrees to the snow. The skier can carve a turn with a tipping angle of 65 degrees, the critical angle. He can also carve a turn with his skis at 70 degrees to the snow, or 75 degrees! Since he is obviously angulating, he has his skis at a much greater angle than the critical angle.
post #142 of 148
Quote:
Originally Posted by Bob Barnes/Colorado View Post
Hi Ghost--perhaps this will help:



Best regards,
Bob
Let's for sake of example say the skier is carving a turn that requires a tipping angle of 73 degrees (damn he's good!)

As the skier goes around the curve and gravity adds to the centrifugal force, the red arrow above will get longer, and the resultant force will be at a different angle. Again for the sake of example, let's say it will reach 30 degrees, thus making the critical angle between the skis and the snow 70 degrees. What must the skier do?

Well to begin with, he must keep his skis tipped at 73 degrees to the snow to continue making his desired turn, but he MUST move his cm further inside the turn to stay balanced on the outside ski's inside edge (the line of action of the force continues to go through the cm and the ski's edge, but with a longer red arrow).

HE CAN ONLY DO BOTH THESE THINGS BY ANGULATING LESS at the end of the turn.

If the skier is going too fast or the slope too steep, the critical angle between the ski and the snow may well reach 74 degrees, and the skier will loose the edge if he tries to make a turn that requires a tipping angle of 73 degrees. Trying to make a turn with the skis tipped to 74 won't work either, because this turn would have an even bigger centrifugal force and "critical" angle. In fact, giving up on the 73 degree turn at this point and carving with a slightly lower tipping angle would keep you carving, if not exactly where you want to go; the critical angle for this not-so-sharp turn would be much lower.
post #143 of 148
Angulating less at the end of the turn because gravity is contributing more, has the same effect as angulating less because you are making the turn at a higher speed. Higher speeds require less angulation. You go faster and faster, angulating less and less until you reach the point where the line to your cm is perpendicular to the ski's topsheet, at which point your skis are at the critical angle. You are banking on the edge! Living on the edge is exciting! Try it! If you never go over the edge, you never really know where it is.

The fun thing about free skiing is you are free to constantly vary the turn radius at will, getting as close to the critical angle at the apex of the turn and then widening the turn as gravity builds to stay at the critical angle.
The other good thing is that there is usually lots of room to make a recovery by easing up on the turn dialed in, should you start sliding out.
post #144 of 148
When driving a car around a corner and it begins to skid, and you don't want it to skid, turn the steering wheel less, not more.
post #145 of 148
Quote:
Originally Posted by borntoski683 View Post
The powder photos of some guy were interesting. Great action shots by the way, can I borrow your camara man? The first one, obviously a little bit of angulation would have helped you or your outside ski wouldn't be in the air. It looks cool in the picture and you're recovering and staying in the game. Not ideal skiing. The second one you're obviously going very slow right at the moment the shot was taken as your skis are practically pointing straight up to the sky. That does not look like a well executed angulation turn to me, that looks like you slammed on the brakes and your upper body went forward down the hill creating the look of angulation.
As I noted in my comments, the first shot is of a very banked turn, the cause of which was having come out of a transition out of balance somewhere and you're right, it's not ideal. The second shot is there to demonstrate what an angulated turn looks like. Yes, I was braking hard because I was getting a picture taken; it was somewhat staged. And no, you can't have my cameraman!

Here's another couple of shots with more appropriate angulation for the conditions but the point is that the shot I selected in the first place was picked because it was exagerated. These are more normal but they don't necessarily make the point:



post #146 of 148
Looks fun! Lookin' good. Watch the shoulder pulls tho' ;-)
post #147 of 148
Tell me Borntoski683, do you usually ski in deep snow or on hard pack?
post #148 of 148
This is my last response to this thread then I am turning off my subscription so I won't be bothered.

Answer: I ski it all
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