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# Other things to be considered while turning..... - Page 2

TdK, like your approach to the entire matter, but if the pitch gets steeper you need to weight more the outside ski. When the slope is flat then you can add more support via the inside ski. But I think you may have just written that incorrect. Also that string rock thing is very clear to me, but it only shows how centrifugal force works, not really gravity and normal force and especially where. But if you could hang that onto a scale and swing that in different angles (slopes) I think that may give a good reading.

Quote:
Originally Posted by simplyfast

TdK, like your approach to the entire matter, but if the pitch gets steeper you need to weight more the outside ski. When the slope is flat then you can add more support via the inside ski. But I think you may have just written that incorrect. Also that string rock thing is very clear to me, but it only shows how centrifugal force works, not really gravity and normal force and especially where. But if you could hang that onto a scale and swing that in different angles (slopes) I think that may give a good reading.

There was a study made of WC skiers skiing 20 gates 10 at flat and 10 at steep with pressure sensors under their feet. To everyones surprice there was more pressure on the outside ski on flat. That was for all the skiers tested.

The string/rock thing takes in consideration gravity and yes, the angle mimics the slope. If you swing it fearly slow and increase the pitch you will feel gravity very easily.
I am sorry, but I did not hear about that test and I would want to know who the skiers were and the guys testing it. I almost go that far and say it is impossible.
Hopefully this will make sense. I took a picture and drew a red line from the estimated cg to the outside foot and a blue line from the cg to the inside foot. These represent the force vectors the skier is creating. The top picture is on a flat and it's easy to see that the red vector has a pretty decent vertical component. It's no great leap of faith to see that his entire body weight could be supported vertically just on the outside ski.

The bottom picture is the same thing, only rotated as a hackneyed show of what happens on a steeper slope. You'll notice the red vector has almost no vertical component. Say it's angle is 10 degrees, then the vertical component is sin(10) = .17. So the force on the red vector needed to support the weight vertically would be 1/.17 = 5.9 times the skiers weight. If the can't hold that, force has to be transfered to the blue vector, which has a much more advantageous angle to support the skiers weight.

So, if this has made any sense, you can see that on steeper slopes, more force has to be carried on the inside ski before the apex. I don't have the verbal skill to describe what happens at and after the apex, but it's different.

Simplyfast, send me a pm and I tell you more.

retroEric, I made a vector diagram and would like to have your opinion.

Look, you cannot take the same picture and put that in a flat or steep situation. Your stance is different in a flat section than in a steep one.
Just go out from a position when you are standing on both feet on top of the hill. (equal pressure/weight) And lets say you start out with just slight turns (weight slightly shifts towards the outside ski) in the upper flat section and start turning more and more as the hill becomes more steep. (increase weight/pressure on outside ski as forces increase)
You don't even have to think twice, almost anyone can picture what happens as you progressively pick up speed and thus increase the radius of the turn.
Let's not forget that it is gravity that keeps the ski pressed into the snow, and on the horizontal section it is perhaps easier to keep that outside ski pressed down because gravity is acting straight into the snow.  Maybe the more-heavily weighted outside ski is the favoured position, but is easier to achieve on the flats for a number of reasons, such as less variation in turning force required from the ski,  tipping angle from the snow being the same from the surface as it is from the horizontal and not changing with ski angle across the hill, etc..

Nice vectors btw tdk6, If you are simply drawing the two forces acting on the skier and their resultant, it's very good.

If you are drawing all the forces acting on the skier, the yellow one should be pointing the other way. (resulting in zero net force or equilibrium in the frame of reference moving with the skier, and resulting a net turning force toward the centre of the arc in a frame of reference stationary with respect to the hill and no centrifugal component)

Ghost, the yellow vector was merely a resultant of the gravity and centrifugal force. Did not want to show all the forces. Here below I have tried to picture the difference between the horisontal and the vertical componenets as we come from the top of the turn to the bottom. I know SF, its not right to just turn the photo arround but me and Ghost merely wanted to bring the differences into pickture. I wanted to show why you tip into the turn at the top and why you un-tip as you come through the bottom half of the turn. Correct me Ghost if Im wrong.

Very good tdk.  Nice vector addition. Just the word "tip" might be misinterpreted if one doesn't already know what you mean.  You mean position the cm, not change the tipping angle of the ski on the snow.  Correct me if I'm wrong.
Great pictures, tdk. Your pictures are a lot better than mine.

Now I realize that the steepness is by far the bigger factor.

On a flat slope you can get more of your turning done before the apex than on a steep slope. Also, you need to use more pressure on the inside leg at the start of a turn on the steeps. Furthermore, you don't need to a-frame to hold your weight up.
Quote:
Originally Posted by Ghost

Very good tdk.  Nice vector addition. Just the word "tip" might be misinterpreted if one doesn't already know what you mean.  You mean position the cm, not change the tipping angle of the ski on the snow.  Correct me if I'm wrong.

Thats what I ment, sorry. Thanks
Let me be a nerd and quote from LeMaster's newest book, "Ultimate Skiing":

p49
Quote:

Line selection is complicated by the pitch of the hill.  Because of the pitch, the ski's edge angle will always be smallest early in the turn and get progressively greater until the turn's completion (figure 3.21).  Because the ski's edge angle determines its carving radius, the turn's radius will naturally get tighter as the turn proceeds.  The steeper the hill, the greater the effect.  It can be mitigated somewhat by carving with the forebody early in the turn and moving back on the ski coming through the bottom, but the fact remains that nice, circular arcs just aren't possible on slopes with much pitch.
BTS, exactly. Not mentioned in his quoting is speed that progressively is increasing through out the turn. Leg extention at the very end of the pressure phase adds to the effect. Lots of things happening past apex:
- edge angles increase
- speed increase
- centrifugal force increases
- gravity force swings arround and starts pulling towards the outside (downhill) insted of the inside (downhill) causing increased turning forces
The last point is really the main one because even in very controlled turns with little speed increase, the effect will be observed.
Quote:
Originally Posted by simplyfast
You don't even have to think twice, almost anyone can picture what happens as you progressively pick up speed and thus increase the radius of the turn.

You mean DE-CREASE the radius of the turn? Depending on the situation offcourse but the thing is that the whole carving consept builds on SPEED. No speed no turning. Eventually your turn radius will start to increase but not before it has de-creased quit a lot. This is when it starts getting dangerous. Your ski turns but your CoM is not due to unbalance.
Quote:
Originally Posted by tdk6
You mean DE-CREASE the radius of the turn? Depending on the situation offcourse but the thing is that the whole carving consept builds on SPEED. No speed no turning. Eventually your turn radius will start to increase but not before it has de-creased quit a lot. This is when it starts getting dangerous. Your ski turns but your CoM is not due to unbalance.

That's too simplistic TDK.

Its really more about the resultant force vector of the CoM.

Speed contributes to the resultant force vector, along with turn radius and skier mass, and let's not forget that gravity is also contributing to the resultant force vector.

The resultant force vector is what determines the critical edge angle that is required to arc and not skid.  You can also and probably usually are edging well beyond the critical edge angle.  The edge angle also determines your radius.   So yes, if you speed up during a turn, you MIGHT need more edge angle to accomodate the increased speed.  That is assuming that your initial edge angle was not already more than enough to stay on edge.

I think with skiers going fast you will find that their speed does not vary that much during a turn.  It does somewhat, but not compared to the other factors that contribute to the resultant force vector.  In terms of slope steepness the primary factor is that the direction your ski bases are facing becomes increasingly lined up with the direction of gravity.  This causes a need for more edge angle to avoid skidding, regardless of speed changes that may or may not occur.
BTS, you probably missed my posting #44. Yes, posting #46 was simplistic but the point is that for carving you need speed. You need turn forces and you need edge angles. And you need to balance. If you skidd you dont need these or much less anyway. Balancing is much easier.
Well decrease or increase depends how you look at it. It depends and BTS said I believe the better answer to that. I guess the radius would decrease while the size of the turn my increase? Hope that is confusing enough.

MfG.
You are in control of what edge angle you tip your skis to.  The edge angle, measured against the slope of the hill required for a given radius varies only with that radius.  The critical edge angle required to hold and not slip at a given radius, however, depends on the forces, centrifugal (m(v^2)/R), and gravity (mg(sinB)sin(T)).  The problem lies in that as the critical angle required to maintain grip increases due to speed increasing and gravity contributing, the requirement can exceed the required angle for that turn radius.  At that point, skidding will happen.  You can't tip any more without calling for a smaller turn radius, which would require an even greater critical angle. Your only options at that point are to open up the turn, or unload the skis and let them cross under at the tighter radius, or a mixture of both.
retroEric, I like your observation with the steepness and how you said that about turning earlier in a flat section than in a steep one.
And actually everyone here so far is really heading in that direction that I kind of wanted to open up to consider. Here and there different point of views, but that is just the way it should be anyhow.
I just thought it is very important to understand that the situation in skiing is under constant change and that it is not simply done by one statement or just one graph to describe what happens in a turn. Besides recognizing that and by how much  the forces change and influence the skiers action while turning is also determined by the terrain/slope.

MfG.
Ghost,

Nice way to describe that and I would also throw in to that a more skilled skier would want to change the edge angle based on the snow condition as well.
Well, I thought about it a bit, and it's more complicated that I first thought. First, I've realized that "On a flat slope you can get more of your turning done before the apex than on a steep slope." Doesn't really mean anything. By definition you're turning the same amount from cross slope to down the fall line whether you're on flat or steep. A more meaningful statement would be: You can get more turning force out of your skis before the apex on a flatter slope. The reasons are as Lemaster wrote more eloquently than I am able.

The interesting part is that on a steeper slope, gravity is doing more of the work of changing your direction before the apex.

I'm going to roll this around in my head while I'm driving to St Louis tomorrow.

Thanks to all for the insights.

retroEric, your modified statement is better. The reason is as you say yourself that its easier to create turning forces when gravity is not pulling you very strongly the opposite way. Thats why its called an "upside down" position. You are balancing over your uphill ski insted of your downhill ski.

The big question is HOW do we create turning forces? As we concluded earlier we need to place our skis on edge. But if we are standing on flat ground with your skis on and tip them to on edge by inclining in the direction we want to turn two things will happen: we will fall in that direction to the ground and we will not turn. What are we missing? Why are we falling to the ground? Why are we not turning? We are falling because we are offsetting our body into the turn and allowing gravity to pull on our CoM outside our BoS down and since we have no TURNING FORCES pulling on us in the other direction we will fall to the ground. The trick here is to tip our skis on edge WITHOUT MOVING OUR CoM OUTSIDE OUR BoS! How do we do that? Simple, we tip our skis on edge with our feet and lean the other way with our body to keep our CoM inside our BoS. If we do it correclty we angulate. Now we can stay upright and our skis are tipping. And we are not falling. But we are still not turning. What are we missing? Cannot feel any turning forces building up! Yes, we are missing SPEED! Lets point our ski tips a bit downhill and give us some speed with our ski poles and try the tipping part again. As soon as we tip our skis on edge as we are sliding forwards we should be turning. And we should feel the turning forces starting to build up.

Its all sequential. Turning forces are really only the body mass accelleration in a new direction. The body mass is accellerated away from its original direction (straight forward) by tipping our skis on edge causing turning. When we do this our lateral static BoS becomes dynamic and shifts in the opposite direction of where the body mass is accellerating. If we want to increase tipping we need to overcome the turning forces and this is easier to do in the high C since we are tipping in the same direction gravity is pulling us. The steeper the easier it is to tip, but the harder it is to create turing forces. Poor performance is not tipping enough in the top part of the turn but its all just a matter of a gross estimation. You need to tip as much as you think is needed. Good skiers do this very well. Bad skier eather end up on their inside ski and in some cases fall to the inside because they inclined too much or skidd their turns because they did not incline enough. Just as important it is to create turning forces we need to aggressively overcome the turing forces at the top part of the turn.

Annother important issue is that if you are on a flat slope you dont have to tip much before you have your skis on edge. If you are on a steep pitch you need to come off your old edges and onto new edges. Keeping your CoM low and flexing through the transitions will help you create highter edge angles early on since you dont need to be moving the CoM so much in the vertical direction.

A wider stance gives you a much wider BoS, stronger stance. It also gives you faster reaction time as you can offset your CoM quicker into a turn. A simple flexing of one leg is enough. Thats why racers use a wider stance. Thats why tennis players have a wide stance when they are returning serves. The faster you go the more important this becomes because of stronger turning forces. Think DH and SG. In SL you use a more narrow stance for other reasons.

Quote:
Originally Posted by simplyfast

Ghost,

Nice way to describe that and I would also throw in to that a more skilled skier would want to change the edge angle based on the snow condition as well.

The snow conditions play a major role. If we are talking about race coaching on a higher level no serious practice can be done if snow is not water injected. Here your equipment play a major role.
Quote:
Originally Posted by simplyfast

I just thought it is very important to understand that the situation in skiing is under constant change and that it is not simply done by one statement or just one graph to describe what happens in a turn. Besides recognizing that and by how much  the forces change and influence the skiers action while turning is also determined by the terrain/slope.

MfG.

Could you show us the graph you are refering to. That would make it easier. There is offcourse not one graph for all kind of skiing but a graph generally just points out certain facts. Like in what direction turn forces pull or what is the shortest way or what is angulation.
TdK6,

You talk about a wider stance being more stable, you say that a weaker skier if inclines too much to the inside ski will perhaps even fall. But yet you suggest an "upside down" position on the inside or uphill ski which contradicts all that. Don't you think it would be a bit confusing to your athlete since he does not know what you consider flat versus steep? My rule is, not matter what terrain, the outside ski is the "boss".

Everything else about you approach is very conform with my theory.
MfG.
Somebody pasted the graph from a website, but now I cannot find it anymore, sorry about that.
Quote:
Originally Posted by simplyfast

TdK6,

You talk about a wider stance being more stable, you say that a weaker skier if inclines too much to the inside ski will perhaps even fall. But yet you suggest an "upside down" position on the inside or uphill ski which contradicts all that. Don't you think it would be a bit confusing to your athlete since he does not know what you consider flat versus steep? My rule is, not matter what terrain, the outside ski is the "boss".

Everything else about you approach is very conform with my theory.
MfG.

I dont understand what an upside down position has to do with a stance width? And I never suggested you should put your weight on your inside ski as you are upside down. And I dont find it hard to tell my students if the slope is steep or flat because I teach on the hill and they can easily see for themselves what kind of pitch it is. Your rule sounds very fine to me. The only thing I would like to expand on is what happens when you come into the transition. Eventually you will have to shift your weight over to the new inside ski. Do you do that progressively through the bottom half of your turn or instantly at edge change?

IMO the problem is that since the wide stance is more stable weeker skiers will be more likely to take a very wide stance. The result of this is that they are weighting the inside ski way too much and they loose outside ski pressure. I always teach my students to ski by wedging. This is where I teach them to pressure and balance over their outside ski.  Never saw a person that could ski well not being able to wedge but I have seen more than enough that had no technique at all and were a danger to themselves and others that could not wedge. After working with handicapped and blind skiers my favorite drill at advanced level is to ski with eyes covered and guided by a coach. Saw the handicapped Austrian championship in Warth in 2008 and it was great to see how well handicapped skiers ski. Especially blind because they cannot see what is ahead of them. My friend is a national level snowboard coach for deff. Hearing is the most important organ to sence our environment. More important than the eyes. Many WC skiers had a problem when they had to start using a helmet. They relied so much on their hearing.
Well maybe I just misunderstood your post then. About a wide stance being more stable, sure but it could invite you to lean towards your inside ski if too wide. Plus you can loose your "square" stance all too easy.
Look at Herbst maybe, his stance is pretty close. Or one of the old masters Stangassinger. A closer stance actually lets you concentrate more pressure/weight on your right skis while a wider stance spreads more out.

MfG.
Tdk6, sorry forgot to respond to transition. Well you understand german and I hope you understand when I say "auf Zug fahren". There is nothing that describes that in english, at least I am not aware of. In that case you would want to stay on your outside edge as long as you can. (like "trampoline" turns, being pulled out of the turn by a rubber band) Like in a through gate in SL or long gates in GS/SG and downhills, that is where the transition gets dragged out and smoothly transfers onto the next outside ski but rather late. (The outside ski pushes forward and that motion transfers onto the inside ski, takes over that momentum and initiates the next turn.)

Then of course you have the tight turns where you have to be real quick as in SL and some GS and that is where you have to be extremely quick in your transition. (hop turns on a bouncy ground may mimic here what really needs to be done) it really is sort of the same move than described above, but it happens in lightening speed and usually not really detected very easy. Here you have no time to waste, the next turn is already coming up so you do not want to stay on your edge longer than you have to. Here is where rebound is held short but intense.
If you have a chance to watch Herbst in real live and not on TV you will realize what he does. There is nobody on the circuit that can do that like he does. It is like a turbo-boost that is build in this guy.
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