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# Accelerating out of a turn - Page 2

Skidude -- do you intend to enlighten us on the difference between "speed" and "velocity"? The last time I cared was in 1988. I seem to recall something about "velocity" being a vector, meaning that a direction is associated with it?
Skidude, disconnected "deductions" of self-impressed "logic" do not create truth. I don't know why you persist in trying to prove something by "logic" when science has shown differently. but hey, even Sisyphus got perverse pleasure in his pointless pursuits. well done!

KevinF, "speed" is a perception. velocity is the physical measurement.
I ski from one turn to another, not so much down hill. In fact, to linger in the inevitable journey is the true goal.

If everything goes just right. sometimes.... there is a little kick in the butt, just when I think all the inertia has been spent.

Release the potential energy, enjoy the kinetic.

Repeat as required for maximum pleasure!

CalG

Speed: is actual distance travelled over a set amount of time. For example if you drove down the highway at 60mph...your speed is 60miles/hour.

Velocity: Velocity, is the distance between your start point and end point measured in a straightline (whether you were able to get there in a straight line is irrelevant) over a set amount of time. for example, If you drove from lets say your house a A, to your friends at B which is 10miles away in a straight line, but becuase of the winding road you actually had to drive 20miles to get there. Your speed may have been 60mph but your velocity would have been half that, 30mph.

So, coming back to the point of this side argument, the question was, can you get to the bottom of the hill (ie point B) quicker by turning. The answer is no. The reason? Becasue while it may be true that you can capture ski energy and accelerate out of a turn, increasing your speed, there is no way it will be enough to overcome the extra distance travelled. Your effectivley comparing the accleration from "pumping" as some call it, to the accleration of gravity.

To help understand more: the accleration offered out of a turn, comes from the flexed ski, straighing. The only force you are getting is like when you flex the ski by hand in a shop, and it comes back at you. That is the force that you are using to accelerate.

The more you bend the ski, the more energy it will have to acclerate you, but to bend the ski more, you need to make your turns "deeper", thus travel further. Thus if you do shallow turns, the ski bends less, your travel less distance, but the energy that you have to acclerate with is also less. At no point will this turning energy be enought to over come the extra distance travelled, since by the nature of how it works means, that to acclerate more you will need to travel further and further distance.

If this turning idea where true, you would see World Cup racers do it over the flats, at the start where it is slow, and usually flat, or just before the finish, where again it is flat.

However, as I mentioned in an earlier post it is possible to acclerate out of a turn. It is done at the highend of skiing and ski racing to get a little extra "umphh" out of turns...it is done to win races and to ski a touch faster as compared to others who are ALSO turning as much as you are.....it would never be done to try and beat someone who is straight lining it....hence JohnH took an idea, that you can accelerate out of turns, to mean that he can ski faster, meaning he can get to the bottom of the hill quicker. Wrong. This is where he needs to understand the difference between Speed and Velocity. He can accelerate out of turn, to get to the next gate quicker, to get to the bottom quicker, then other racers who, again are also turning. But he would never beat someone who ignored the gates and just pointed em....

Hence in racing, we usually just focus on speed, but in this particualr issue we are comparing velocity, what is the fastest a to b, regardless of path taken.

hope that helps....although I probably just confused you more.
Quote:
 Originally Posted by uncle crud Skidude, disconnected "deductions" of self-impressed "logic" do not create truth. I don't know why you persist in trying to prove something by "logic" when science has shown differently. but hey, even Sisyphus got perverse pleasure in his pointless pursuits. well done! KevinF, "speed" is a perception. velocity is the physical measurement.
Oh brother....
Quote:
 you excelerate MORE by just pointing them...and keep accelerating until you crash or hit some terminal velocity created by friction.
At some point, the skis will start to squirrel, shaving off your speed and acceleration.

It is not similar to skateboarding (otherwise the snowboarders would already start using it); nor is it similar to pumping on the swings.

According to Ron LeMaster, when you load the tips, they cut into the snow/ice and define the curve, and when you load the tails, the skis go faster. After that, it's centrifugal acceleration of the edged skis that may or may not help you go faster.

I first felt it when I was about 13, riding a bicycle with my firends, when I started swinging it smoothly left and right in the same rythm as I was pushing the pedals, making it "carve the turn": all of a sudden I was ahead of the rest of the group. Did you notice how the racers in Tour De France stand up out of the saddle when they need to accelerate? That's the same idea: they swing the bike with every push on the pedal, and they don't want to put too much weight on the saddle at such moments.

Yes, we can accelerate out of the turn when skiing - if we use the dynamics correctly.
Squirrel?

Now we are on Animal Planet???
We sure are
Look people there is NO acceleration out of a turn- it has been tested and proven over the years. The more you load a ski to bend it into reverse camber (flex) the more the radius shortens and the more braking force is imparted on the turn. The "snap" you may feel of the ski releasing its energy is always going to be less than pure fall line skiing. Yes you may feel like you are accelerating but only because you have exerted such a braking force in the turn that when you re-enter the fall line in your transitional movement you feel like your speed is increasing. But again, this will always be less than a pure fall line straight run. Many of the analogies posted here as in the bike reference have no bearing on this issue.
Try this. Get a pair of Rossi 9S or another short lively and very shaped skis, fairly soft. Then try skiing fast down a fairly gentle slope and complete each turn without ANY skidding. Then make a turn the way they should NOT be taught - lead it to completion with the outside shoulder, but DON'T SKID. Forget body stacking; countering; unweighting in that one turn. Just let the skis do what they do best: decamber them and wait. What will happen is the skis will turn up and then possibly will go a couple of feet up the slope. You will have compensated for the gravity pull by accelerating out of the turn.

Regarding the bicycle reference, it is directly related to the issue: the cyclists do accelerate by swinging the bikes; it's the rhythm (frequency) that matters most. What happens when you tilt the bicycle? it goes into a turn. The same thing happens to the skier when you tilt him/her.
Quote:
 Originally Posted by Skidude72 The more you bend the ski, the more energy it will have to acclerate you, but to bend the ski more, you need to make your turns "deeper", thus travel further. Thus if you do shallow turns, the ski bends less, your travel less distance, but the energy that you have to acclerate with is also less. At no point will this turning energy be enought to over come the extra distance travelled, since by the nature of how it works means, that to acclerate more you will need to travel further and further distance.
Here's your problem, dude. You didn't listen when I said that passively turning, as you describe above, doesn't cut it. When you pump out of a turn, you are imparting enery to the skis to help them accelerate.

Quote:
 Originally Posted by Skidude72 As for your skateboard anology, skateboarding and skiing are not the same. To pump in skiing as you suggest, would be akin to skating downhill, in that case sure I agree, but skating is not turning. You will never get the necessary momentum to create enough energy in the turns at that speed to make up for the extra distance.
Yes, they are the same. Again, you didn't listen (read) very well. Keep both feet on the skateboard on a flat surface. Can you make it move forward? I can. But I guess you have never tried, so you feel it's impossible.

Quote:
 Originally Posted by Skidude72 If this turning idea where true, you would see World Cup racers do it over the flats, at the start where it is slow, and usually flat, or just before the finish, where again it is flat.
Guess what, dude? They DO! Watch a SL racer come out of the bottom of the first 2-3 gates. They pump their way out of the gate to gain acceleration. No, they don't deviate from the fastest line, because the gates come at them too fast and they would end up out of the proper line. And if they were going slow, they'd just skate.

Quote:
 Originally Posted by Skidude72 However, as I mentioned in an earlier post it is possible to acclerate out of a turn. It is done at the highend of skiing and ski racing to get a little extra "umphh" out of turns
This is exactly what I'm talking about, and yes, you can beat someone who is straightlining it, if the conditions are right (flat slope) and the speed of straightlining is slow enough.
I just love rebuttals where they donâ€™t say that I am wrong, but rather they go for the I didnâ€™t understand what they were saying approach. The fact is, I donâ€™t really care what some think, I am only here to answer a few questions, and hopefully pass on some of my knowledge and experience. If some of you choose to believe that WC Slalom racers turn around the gates to gain speed, as opposed to believing that they turn around the gates because it is the rulesâ€¦.good for you.

If you want to prove your points by referring to skateboards or butterflyâ€™s I encourage you to do that also. As for me, I will talk about skiing, ski technique, and the associated physics and biomechanics because I can. If you donâ€™t understand something I wrote, just ask and I will be happy to try and explain. If you as a reader of these forums believe that there are two or more good points raised in these threads, but conflict, I encourage you to try things out on the hill for yourselves. It may also be good to discuss the ideas with your peers and mentors because I would suggest that in a lot of cases it would only take one good on-hill demo for it all to become clear.
Rats, haven't the time to read all the posts on this one but did notice the post by PhysicsMan and will have to go back to that one tomorrow.

YES, you can move down a slope faster by making energetic short radius turns properly than by a straight glide...!

Earlier this season I asked a former PNW Tech Teamer to show me 'acceleration turns' as I wished to learn the technique. He had a friend of mine ski straight down the slope we were on (maybe 12 or 15-degrees) while he made short radius 'pumping' turns. While my friend started off quicker, Marty-O' passed him up after maybe 20 or 25 feet, and blew him away after that.

We worked on the technique for a while but I've yet to get it working so well for myself.

For those questioning the concept, it's NOT about storing energy in the -ski- it's about where our MASS is during each phase of our turn. The turn starts with our Mass low and close to the skis (we flex a lot).

As the turn progresses we extend forcibly, raising our Mass toward the center of the turn before the turn completes (read mondo Inclination). This is much like the figure skater pulling her arms in moving Mass closer to her center, effect: our rate of rotation (around the turn) increases.

I'm also quite certain there is a point of diminishing returns in this.

At some point the given rate of travel down the hill cannot be increased (by pumping alone) because my ability to move quickly and properly create the pumping-effect is limited by my athletic ability. I simply can't pump quickly enough. Also, as mentioned by others there is a point of diminishing returns when our turn radius gets too large - we can only raise our Mass a small percentage of the turn-radius in a medium radius turn.

As to the idea that "if it were possible, everyone would do it" ... Well, skiing the Downhill in the Olympics is certainly possible, so why isn't everyone doing it? Maybe 'cause it takes a bit more skill than the average skier has? There is also the issue of Lateral Balance and the high likelyhood of disrupting said balance. This takes accurate timing and a high degree of edge control. No doubt it often makes more sense to a racer to limit this quirky activity when they've got better things to do - like managing their line.

I've been skiing a while and may even qualify as an 'old fart' trying for my L3 this year. Still, this Pumping thing isn't yet working as well as I'd like. Hafta work on it a little more I guess.

Anyway, for those of you actually doing this in a race setting I'd sure like to hear some technical tips on better execution.

.ma
were these "energetic" turns using pole plants or any push offs? Were you sure there were no skating or push off movements? We tried this over and over and no one was able to beat a straight run when turning unless they were pushing off. I had yet to find a skier who can make energetic SL type turns on a near flat slope from a dead stop without resorting to an initial skate type movement. No one was able to beat the straight running skier regardless. These were all high level (8 of 'em)- J2 racers. Every time they move across the fall line they fell farther back from the straight run.
OK, I'm a little late on this thread, but how about this simple explanation. If turn initiation is a braking motion, perhaps we're storing the lost kinetic energy in the ski, turning it into potential energy, and turning that potential energy back into kinetic energy at the end of the turn. It isn't creating energy, but reusing as close to the same amount of energy lost as possible.
As far as Physicsman's analogy of the figure skater, that's bogus. The figure skater has a certain rotational momentum, when they bring their arms in, they are decreasing their rotational mass by bringing some of their mass closer to center, and therefore rotate faster. It has nothing to do with the subject at hand.
Several years ago, a friend and accomplished masters racer came to the hill every day M-F before work and skied 10 practice runs. His form and balance was always perfect, and occassionally, when my skiing was suffering because my balance wasn't right, I'd follow him down the hill and my balance would come back just by mimicking his position. I am no way a race geek, I am a bumper and an all-mountain skier, every turn I do is to scrub speed and never had patience to learn the true race turn. Well, one day, he decided to teach me something. He stopped on the hill, and told me to raise my outside hip at a certain part of the turn. The result was an epiphany, it was like someone was behind me giving me a kick in the ass. So, yes, there is a way to accelerate out of the turn, but I think it's only reclaiming lost energy.
i've been following this topic, and all of a sudden it seems very simple
i tried it on in-line skates (on a very little slope that evened out) and using short, slalom style turns i was able to keep going much faster/further then straightlining it.
as to why racers wouldn't turn on flat areas where there are no gates? at that speed, you would lose more speed turning then you could gain (the human body does have limitations). imagine this... going slowly on a skateboard, if you push off you gain speed; going 60km/h on a skateboard (i know it's not reasonable, but bear with me), you couldn't push off fast enough to speed yourself up and just putting a foot down with the intention of pushing off would slow you down.
gonna try it on skis on saturday

jinx

edit: i don't think you're reclaming lost energy, rather flexing in/out of the turn you actually push off
Quote:
 Originally Posted by 2-turn OK, I'm a little late on this thread, but how about this simple explanation. If turn initiation is a braking motion, perhaps we're storing the lost kinetic energy in the ski, turning it into potential energy, and turning that potential energy back into kinetic energy at the end of the turn. It isn't creating energy, but reusing as close to the same amount of energy lost as possible...
Try pumping on a swing strung up with stretchy ropes. If the ropes have sufficient give, it's almost impossible because centrifugal force will move your center of mass away from the center of the turn (the support) at those moments you need to be forcing your CM up towards the support and thereby gaining extra angular velocity (at constant angular momentum, ie, m*v^2 / r is constant). Flex in the skis WILL return some of the energy you put into them, but pumping is extra, something different, on top of this.

Quote:
 Originally Posted by 2-turn As far as Physicsman's analogy of the figure skater, that's bogus. The figure skater has a certain rotational momentum, when they bring their arms in, they are decreasing their rotational mass by bringing some of their mass closer to center, and therefore rotate faster. It has nothing to do with the subject at hand.
Sorry, but it does. Two comments:

1) There is indeed rotational angular momentium of a skier in a turn. Consider a skier at the apex of a pure carved arc. His or her path is close to a circle of a certain radius and there is a mass (the skier) traveling around that circle. That means that there is angular momemtum around the center of rotation. If you decrease radius of the turn by phyically moving your CM towards the center of the turn (ie, not changing the radius of curvature of the turn), then, by the conservation of angular momentum, your tangential velocity will increase, just like the pirouetting skater. At each transition, ie, where your angular momentum is zero, and so up-and-down motions won't change your angular momentium (ie, it will remain zero), if you let your CM settle back down a bit towards you skis, you will be set to repeat this movement over and over again. This is the simplest version of pumping.

2) Did you even glance at the peer-reviewed journal article I cited where they analyzed pumping on a swing in the rotational domain by making an analogy with what is essentially a figure skater pirouetting on a lazy susan constrained by a spiral (wind-up) spring. Even if you don't understand the math or physics behind their analysis, it should be obvious from the most casual read that one group of PhD's made a sufficiently accurate analogy between a swing and the rotational motion of a pirouetting skater that a second, completely independent group (the reviewers of the article) agreed completely. In actuality, what they were doing is trying to simplify the analysis of the swing to the analysis of something (conservation of angular momentum) that everyone can understand.

MichaelA nailed it correctly in his recent post where he pointed out (in simpler language) what I described above, e.g., it's not about storing energy in the skis, his comments on the limitations of the pumping technique due to our physical limitations, etc.

Jinx also has it correct in his edit about not recovering lost energy.

JamesK - The reason "pumping" doesn't work from a dead stop (ie, the situation you described) is exactly the same reason you can't pump a swing that is not already moving (at least a bit) - you need some initial angular momentum to build on.

Cheers,

Tom / PM
Quote:
 Originally Posted by PhysicsMan Jinx also has it correct in his edit about not recovering lost energy.
OT and moot point, but anyway: that's "her" edit

Jamesk basically has it correct- most of these other analogies simply do not apply to skiing. I do like the "reclaimed lost energy" comment- that perhaps explains why you get the "sensation" of accellerating out of a turn. I hope this finally puts it all to a rest once and for all.

But I know you guys will continue to beat it to death despite its resolution- Have fun!
Physicsman,

I knew we could count on you!!!

A-man
Vail99, you've got some folks on your side who say pumping doesn't work, basically because they either can't do it themselves or have never seen it done, and some folks on my side (one of whom is an L3) who either have done it themselves or have witnessed it being done.

Arguing that something can't be done because you haven't seen it done (or can't do it yourself) can be tricky because the reason it didn't happen could simply be that the people trying didn't know how to do it or were trying to "do it" under the wrong conditions (eg, too fast, too steep, snow was too soft, radius was too long, etc.).

OTOH, arguing that something can be done because you have done it yourself or have witnessed it being done is a lot easier to defend. In this case, if you're sure the witness hasn't missed a bit of a skating step or a pole plant and the guy making turns beats the guy going straight, it's a slam dunk.

I think what this really calls for is a field trip, somebody who says they can do it well (ie, not me), somebody else matched to person #1 in straight line runs, lots of witnesses (or a video cam), and lots of beer!

It probably won't be the world's slowest and least exciting race, but with one guy making a zillion shallow turns on low angle terrain and the other doing absolutely nothing but going straight, it will probably come pretty close : Don't worry, tho, that's what the beer is for.

Tom / PM
Physicaman--- It was "Jamesk" who did the experiment with his racers- I think you have me confused with his and many other posters here.

In any case the initial posting regarding accelleration out of a turn has proven over and over to be false- just ask any race coach. Any good coach will have his skiers minimize braking in their turns and we all know that the tighter the radius the more braking in the initial phases of a turn will always slow you down, the release of the energy in the ski or an attempt at pumping (no poles, no pushing, no skating movements) will never overcome the deviation from the fall line.

My basis will always be what the skiers at the highest level are doing- and what the clock says at the end of the run. Play at the recreational level is fine as a source of debate here, but no one takes it seriously at the upper levels.

I just dont want jr racers being led into a false concept in ways to look for speed- there are so many otehr areas where skiers can gain speed that are clear, definite and workable. Thats what I would rather focus on.
Vail99 - Your comments on pumping not being applicable to racing fits dovetails with the previous caveats about pumping working best in relatively slow, shallow, short radius turns, and becoming less effective as you go faster, steeper and longer in radius, ie, the very province of the racer. While there might be some minor usability in parts of the course, you nailed it when you said that Jr. racers should never be misled by this & that there are lots of other things for them to be working on. Fortunately, I don't think too many will be misled.

I think this thread zig-zagged back and forth between trying to answer two distinct questions: (1) "Can it be done at all while skiing", and (2) "If it can be done, does it have much impact on competent amateurs' and racers' skiing". I think that's one of the major reasons for the confusion and seemingly contradictory points of view.

(edit: In the last paragraph, "it" = "pumping to increase your speed")

Cheers,

Tom / PM
Quote:
 Originally Posted by jinx OT and moot point, but anyway: that's "her" edit lady jinx
Whoops!!! Sorry. I just saw this post. Do I at least get partial credit for at least having a "his or her" earlier in that message.

Tom / PM

I repeat it's been pretty much gone over, surely you remember this thread Vail99?

Tom / PM
Vail99, I know the flat hill pumping thing works, as I too have done it. But as PM has already explained, the pumping speed generating move the proponents are speaking of here, and the race arena application you're speaking of are two different beasts. There's a speed threshold where pumping, skating, etc. loses it's effectiveness. Where that threshold is depends on a combination of slope pitch (which determines gravities ability to accelerate the skier), current speed, and skier skill level.

As you suggest, this pumping tactic has little application in a race course. Skating does the same thing and provides better control of line the first few gates and in flat/slow sections. And at most other times during a run the threshold at which skating becomes useless is left behind.

That said, during a high speed race turn the skis are strongly driven into reverse camber, and if the timing and movements of the release are done properly that stored energy can be somewhat directed into the new line of travel. It's a very tricky thing to teach or explain, but when you dial in the proper execution you can feel the difference. It's why you sometimes see racers aggressively driving their arms forward as they come out of an arc to arc transition; it's an attempt to use and direct that energy into the new line.

Or,,, during pivoted cross-throughs you see the racer use that energy to help propel their CM across the falline as gravity drives it down the falline. Ligety is the current master at this technique. In comparison to Ted the other racers releases are very flat, with little forward energy being employed. The energy they have at their disposal is just absorbed and allowed to dissipate. Their absorbing tactic allows them to stay very balanced and controlled, but compared to what Ted is doing, it's slow.
Hey, Rick - How ya been, Bud? I hope you are having a good season.

It must be late, because I had a wierd thought related to pumping, namely, the concept of "anti-pumping" for recreational skiers who want to carve but keep the speed down (not up) ...

Since pumping works best at low speeds and lots of short radius turns, "anti-pumping" will also work well in this situation, ie, dropping or flexing low at the apices of turns, then rising and standing tall (rainbowing) at the transitions. The difference is that "anti-pumping" will slow the skier down a tad in each turn, whereas "pumping" will speed him/her up. Low speeds and lots of short radius turns is the domain of moderatly accomplished recreational skiers, and a lot of them "pressure control" in a way tantamount to "anti-pumping". A lot of this rising at the transitions is obviously old-school habit, but I wonder if another reason for the ubiquity of this way of skiing is in part due to a subconscious realization that it affords some speed control?

In fact, do you remember the thread (http://forums.epicski.com/showthread.php?t=26995) where SSH described following Nolo and Uncle Louie, but always picking up more speed than them? A lot of reasons were offered in that thread for this effect, but I wonder if by any chance, Nolo and Uncle Louie might have been doing some "anti-pumping" whereas SSH with his race background might have been 180 degrees out of phase and been pumping? Since Nolo and Uncle Louie are around, perhaps they will drop by, put their \$0.02 in, and let us know how they were handling pressure control on a presumably relaxed run with SSH.

The effect of "anti-pumping" on average speed is obviously not going to be huge, but I don't know if it's unmeasurably small or maybe just at the 10% level. If I get a chance, I may do some calculations to estimate the magnitude of the effect.

Cheers,

Tom / PM
Humm ... I've read through more of the old SSH thread, including my own posts in it, and now that I refreshed my memory of it, my opinion is that the other effects mentioned in that thread will dominate any slowing down due to "anti-pumping" (at least at the speeds they were going, and the angle of the slope they were on ), so I think I'm going to put this theory into the circular file that sits along side my desk.

Nite...

Tom / PM
Hi, Tom. I'm doing super, thanks for asking, and your fantastic input has been sorely missed around here. Interesting concept, this anti pumping idea. I'm off to Steamboat in the morning (coaching at the NASTAR Nationals), so I have to sign off for the evening, but I'll give this some thought and add comment on it when I return. Great to have you around again.
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