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CG at Transition, Sequence of Three Aspects Transitions

post #1 of 21
Thread Starter 

Transition could be defined as--

 

  1. Arc changes from left-hand to right-hand (or right-hand to left-hand)
  2. Edges cross zero edge angle.
  3. CG crosses center of stance.

 

I guess 1 is probably the best definition.  Then the question arise, do the other two transitions happen before, at, or after the 1?

 

I've reach a bit of an analysis conundrum. Consider the the diagram below.  Say this is the side view of the hill at transition.  Say that the red dot represents the center of the stance equidistant between each ski.  The blue got is directly above.  If you were standing still, in static balance, the blue dot is where your CG would be.  Now lets say you are skiing.  The green dot is the spot at 90degrees to the hill of the red spot.  Should your CG be here?  If so, your CG would have had to cross the center of the stance before edge change.  The only that could not be is if you did some really funky angulation down the hill at transition.  I thinking in dynamic skiing, you can have your CG at the green dot and have your CG pass over the center of  your stance ahead of transition an momentum will take care of everything; you skis will turn and catch the force of your CG moving down the hill and put you in balance.  But skiing slowly, do you actually have to somehow break the sequence of all transitions happening at the same time?

slopeCG1.GIF

 

It seem to remember Bob Barnes having some sequence drawings of top and side view through a couple turns.  Maybe they would help clarify but I haven't seen the in a long time and I don't remember what sequence of the three transitions they indicate.

 

-l2t

 

post #2 of 21

I'm thinking just tilt your screen 30 degrees.

post #3 of 21
Quote:
Originally Posted by learn2turn View Post

Transition could be defined as--

 

  1. Arc changes from left-hand to right-hand (or right-hand to left-hand)
  2. Edges cross zero edge angle.
  3. CG crosses center of stance.

 

I guess 1 is probably the best definition.  Then the question arise, do the other two transitions happen before, at, or after the 1?

 

I've reach a bit of an analysis conundrum. Consider the the diagram below.  Say this is the side view of the hill at transition.  Say that the red dot represents the center of the stance equidistant between each ski.  The blue got is directly above.  If you were standing still, in static balance, the blue dot is where your CG would be.  Now lets say you are skiing.  The green dot is the spot at 90degrees to the hill of the red spot.  Should your CG be here?  If so, your CG would have had to cross the center of the stance before edge change.  The only that could not be is if you did some really funky angulation down the hill at transition.  I thinking in dynamic skiing, you can have your CG at the green dot and have your CG pass over the center of  your stance ahead of transition an momentum will take care of everything; you skis will turn and catch the force of your CG moving down the hill and put you in balance.  But skiing slowly, do you actually have to somehow break the sequence of all transitions happening at the same time?

slopeCG1.GIF

 

It seem to remember Bob Barnes having some sequence drawings of top and side view through a couple turns.  Maybe they would help clarify but I haven't seen the in a long time and I don't remember what sequence of the three transitions they indicate.

 

-l2t

 



all offensive turns slow or fast have all three things happening at the sametime. In slower speed turn you just do not move as much inside.

post #4 of 21
Hi Learn2Turn,

I think this thread has the illustrations of Bob's you are thinking of:
Those Turns Illustrated

Quote:
Originally Posted by learn2turn View Post

...The blue got is directly above.  If you were standing still, in static balance, the blue dot is where your CG would be.

Maybe. You could certainly make it so. However, I'll bet you naturally have a bit more bias to the downhill ski when standing on the side of the hill or traversing.
post #5 of 21

If only it was that simple L2T!

  • The direction change occurs when the turning to one direction stops and that immediately occurs when the skis are released. The skis don't reach zero edge angle anywhere near that point. (see Bob's graphics in the yellow box)
  • The center of gravity is a mathematical concept and it cannot be assumed it is alway inside the body. So the implied connection between flat skis being when the CoG has crossed over the feet needs to be re-evaluated. Same goes for the equal leg length moment you call center of stance (if that is what you are calling it)
  • it is unclear what you call the transition. The most common definition is a transition from one turn to the next and all of this stuff is included. An edge release, edge change, and re-engagement. A cross over / under where the dual paths pass over / beneath each other. And the direction change.

If you look closely at Barnes' graphics you will notice all of these things occur at different times, not as Bush erroneously suggests. (sorry Bush but it's just not a simultaneous event, it's a series of events)

 

L2T as you study this stuff further I am sure you will get your mind around the idea that the transition is a phase and as such it is not a single point during a turn. Only then will the conundrums melt away and leave you with the clarity you seek. Ski well my friend.


Edited by justanotherskipro - 1/22/12 at 9:06pm
post #6 of 21
Quote:
Originally Posted by cgeib View Post


Hi Learn2Turn,
I think this thread has the illustrations of Bob's you are thinking of:
Those Turns Illustrated
Maybe. You could certainly make it so. However, I'll bet you naturally have a bit more bias to the downhill ski when standing on the side of the hill or traversing.


Bob's diagrams and descriptions are very clear and concise!  and JASP adds some great points too.

 

I would add that the amount of forward momentum plays a role in the relationship between edge change and direction change which can occur at different intervals.  For example, when traveling very slowly we can release the edges which will permit the tips to seek the fall line, provided we move accurately over them, but even though we have begun to turn, the edge change may not occur until very close to the fall line.  Conversely, when we are carrying ample forward momentum the edge change can occur much earlier, closer to simultaneously with the release.  Think pivot slip entry vs. arc to arc entry.

 

 

 

post #7 of 21
Thread Starter 

Thanks for finding the illustration.  I knew the answer would be there.

 

I think the critical factor as mentioned by jasp and others is that the skis do not have to reach zero angle to release.

 

Looking at the Dynamic Parallel illustration, you can see that the skis are still somewhat on the old edge at points 12 and 20 which are the transition with respect to ski path. 

 

 

post #8 of 21
Quote:
Originally Posted by bud heishman View Post


Bob's diagrams and descriptions are very clear and concise!  and JASP adds some great points too.

 

I would add that the amount of forward momentum plays a role in the relationship between edge change and direction change which can occur at different intervals.  For example, when traveling very slowly we can release the edges which will permit the tips to seek the fall line, provided we move accurately over them, but even though we have begun to turn, the edge change may not occur until very close to the fall line.  Conversely, when we are carrying ample forward momentum the edge change can occur much earlier, closer to simultaneously with the release.  Think pivot slip entry vs. arc to arc entry.

 

 

 


Speed allows us to stand against the edged skis earlier.
post #9 of 21

Yes, in Bob's dynamic parallel graphic the re-engagement occurs at a different point than it does in the wedge turns. 14 verses 16. Only then does the passive weight shift become possible. But as I mentioned earlier it isn't this simple. Even the idea of momentum and speed involves multiple on and off axis components. I won't hijack this thread and hopefully not open the door to all the theoretical physicists to do that either but I will suggest the subject is far too complex to be presented in anything short of a book like Jules Vagners wrote many years ago.

 

What I will offer instead is a simple idea that the transition is where wholesale and ironically the most subtle changes occur. It's also the most important and complicated phase of a turn, or series of turns. Developing the near flat skiing skills needed to perform clean transitions and to carry the maximum amount of momentum into the next turn is usually the difference between first and last place, and it's the difference between good and great skiing.

post #10 of 21

Bob's pictures are great but since I could not see a definition of camera angle its not very useful for determining the sequence of edge change relative to passing the 90 degree line.

 

It's important to point out that the green line represents a neutral position at edge change. The CoM will be close to this line at edge change, either to the left or to the right of it. It will never be anywhere close to the blue line.

 

l2t, your picture is a bit oversimplified if you want it to describe lateral actions. In your picture fore-aft will play a large role in the CoM position, unless the skis are 90 degrees to the fall line.

post #11 of 21

Jamt, good to see you buddy! The yellow box shows edge angles from behind the skier, the skier is viewed from above. I'm curious if your comments about the green line and a neutral position means a symmetrical body position? Angulation like we see in the serpent move, or a countered stance may move the CoM / CoG out of the body and not near the green line when the skis finally get flat to the snow. Even the point that the skis are flat to the snow can be variable (moguls, ruts, etc) So even though we generalize about the symmetrical body position and the skis being flat simultaneously, we need to leave wiggle room in there to accomodate those times when a symmetrical body position doesn't coincide with the edges reaching the flat to the snow point.


Edited by justanotherskipro - 1/23/12 at 10:45pm
post #12 of 21
Quote:
Originally Posted by justanotherskipro View Post

Jamt, good to see you buddy! The yellow box shows edge angles from behind the skier, the skier is viewed from above. I'm curious if your comments about the green line and a neutral position means a symmetrical body position? Angulation like we see in the serpent move, or a countered stance may move the CoM / CoG out of the body and not near the green line when the skis finally get flat to the snow. So even though we generalize about the symmetrical body position and the skis being flat simultaneously, we need to leave wiggle room in there to accomodate those times when a symmetrical body position doesn't coincide with the edges reaching the flat to the snow point.


It does not imply a symmetrical body position, it really depends on what you want to do in the next turn. If you need to tighten up you keep the old edges as long as possible before you release, thus keeping the countering as well. You can even increase the edging at this time, because the legs flex more. This sets you up for a strong anticipation and a rapid transition, and as you say the COM will pass the green line before the skis are flat. In racing recentering is the concept of recentering the symmetry in transition, but it does not always happen at edge neutral.

You know the video with the GS stars freeskiing, that one has some excellent examples of recentering.

 

post #13 of 21

liget-bc-2006-gs-2.jpg

 

Jamt, here is Ligety doing a variation of the serpent move made famous back in the late sixties. . Notice his upper body is not symmetrically lined up with the flat skis, equal leg length moment (frame five). That doesn't mean it doesn't line up with the legs eventually tough. I would point out that occurs somewhere after frame five and almost at frame six. By then the legs are not equal length

 

I have a picture of Jerry Burg in moguls in my gallery but I need help accessing it for this discussion. Maybe I'll import it to my computer from my Epic gallery...

 

post #14 of 21

900x600px-LL-f0cc77ee_Selected20Images20from20Ultimate20Skiingberg-moduls-01-final.jpg

Here it is. Notice the anticipated body at frame five and the ski flat to the snow! The slope is clearly steeper than the shoulder of the bump he is absorbing but the skis are very much flat to the snow surface.

post #15 of 21

What I am trying to show here is that the idea of symmetry at the transition is overplayed and as the dynamics of the transition increase, an arbitrary theoretical ideal like recentering to a symmetrical stance becomes less appropriate to the desired outcome. I also want to point out that neither example show a recovery move where the skiers were off balance and needing to "re-center". Is it a function of intent dictating technique? Absolutely. Does it invalidate the idea of learning to be symmetrical at the same point the skis get flat to the snow? No not at all, knowing how to do that is a good thing. It's just good to know how to maintain anticipation and some angulation through the transition. Once the new turn starts we can line up the body along the balance axis but the legs more than likely will not be equal length and the skis may already be on edge, if not already engaged.  


Edited by justanotherskipro - 1/24/12 at 1:44pm
post #16 of 21

Ironically, I spent about two hours discussing this very subject with HH and even though he doesn't really like PSIA types we had a very civil discussion of this being a large part of conserving momentum through the transition. Let him think it was all his idea. Spent countless days working on it with our trainers over in Aspen, and even many of Barnes' foot squirt clinics where we explored leaving that square to the skis and symmetrical body position concept in the lodge. My personal opinion is obvious, so I won't repeat it. But by all mean I would encourage you to explore all options and decide for yourself if that re-center to a symmetrical stance makes sense in your skiing. Ski well Jamtbeercheer.gif

post #17 of 21

Great input JASP. I absolutely agree with you, IMO recentering has too much focus in racing circuits, or at least it has had. I just watched a video of Marcel Hirscher and he sometimes has immense amounts of upper body anticipation at edge angle neutral, and obviously if that is the case when you pass through the square to the skis state your legs must be unequal length then.

 

Full recentering only makes sense if your line is not forced by gates or terrain, and as you say it is a good skill to have but primarly a theoretical ideal.

 

Personally I don't pay much attention if I am edge neutral when I pass through square. Probably quite so when carving arc2arc but not so much otherwise.

 

Nice pictures.

post #18 of 21
Quote:
Originally Posted by Kneale Brownson View Post


Speed allows us to stand against the edged skis earlier.


definitelyicon14.gif

 

post #19 of 21

Different turn type here - retraction, more like the Berg images above.

 

You can see what your talking about in this video at roughly 21 secs and 32 secs at the transition.

 

 video by: 3CAConcept                                                                                     http://youtu.be/AAvhCyoK_RA

 

It does look like he moves the outside ski forward at the end of the turn to even the tips up. This "slicing" action of the outside foot simplyfast talked about last year. It would seem that this allows to move over the skis into the next turn sooner, and keeps more pressure on that soon to be inside foot.

post #20 of 21

Marcel the great:

Marcel anticipation at neutral.jpg

post #21 of 21

Plus blocking pole plant? Can't tell.

It seems that numero uno for slalom skiers is stable upper body. It's really quite impressive.

 

http://cdn.epicski.com/6/61/61d4082c_Marcelanticipationatneutral.jpeg

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