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Best Bump Technique: Backpedaling? - Page 6

post #151 of 166
V8--what you describe is pretty much what the original Stickman that I drew does. The only difference is that he remains cuff neutral in his boots all the time, even as he pushes his feet ahead of him and pulls them back behind him. While it may seem like you have to press on the backs of the boots when you push your feet forward, and on the fronts when you pull them back, the fact is that you don't. And, I maintain, shouldn't!

Best regards,
Bob
post #152 of 166
I am a yellow stick man!!!!
Owwww!
post #153 of 166
Hi veeeight,

Ya know, there are probably an infinite number of stickman iterations and I am not going to get to all of them - I am not even going to try! I believe that I am missing one and with work commitments and a pending trip I don't expect it to arrive soon.

Anyway, I'm with Bob on this! Your request is playing! Further, aside from the fact that stickman has perfect timing and stays neutral in his cuffs, the only one that doesn't match your description is yellow man going out the back door - I even drew the vertical lines!!!

Describing my intent and reasoning might help understand why I chose the examples I did for these animations - and also let you determine if I was successful or not!! The intent was simple, try to answer ssh's questions:

Quote:
Originally Posted by ssh View Post
...What would each of those stickmen look like trying to backpedal in bumps? Furthermore, what would their bodies be doing if they were guiding the skis properly?
How do you do that with so many variables? And how do you compete with "stickman"? That guy is just living right! Beautiful moguls that perfectly match his perfectly balanced full range of flexion and extension, plus he's able to peg a constant velocity of his CM that allows him to maintain perfect ski to snow contact without deflecting his CM.

So, I decided - for the sake of doing a comparison overlay - that my stickmen could live almost as well with their screwed up boots. To that end - for the overlay versions - I assumed that stickman was still perfect in his timing, velocity, etc. ... however, I did restrict him to the range of motion that allowed him to remain in balance as effected by his poor boot setup - yellow man can't flex deeply to absorb as well so his CM rises over the mogul and hot pink man can't extend fully into the trough so his CM has to dip a bit into the valley between.

The second yellow man (non-overlay version) was simply to show the consequence of exceeding the "in balance" range of motion by trying to swallow a mogul when your equipment forces you out that backdoor in order to do so. The version that I'm missing currently is hot pink stickman trying to fully extend into the trough like his instructor original stickman is able to do. What's going to happen when he attempts that?

Chris

PS My wife does not understand this sudden interest in riding a unicycle, but is thankful as she feels I get way too caught up in skiing
post #154 of 166
Very nicely done, cgeib, and very educational, too. I look at those and think about how many skiers I ski with and try to help who match each of those options. These animations provide insight into the importance of set-up, but also into the mis-judgements we can make when we mistake a technique issue ("you're in the back seat in the bumps") for an equipment set-up problem. If a skier refuses to make a change to their set-up (or can't... see "rental boots"), we'll have to help them compensate. But, at least we know what the real issue is... and it isn't technique!
post #155 of 166

CTKook..... Thanks

Quote:
Originally Posted by CTKook View Post
saying that absorption can't suck up speed is basically the flipside to the arguments that you can't pump terrain features (including bumps) for speed, or that you can't accelerate out of a turn. People who say you can't do these things often do resort to saying they violate the laws of physics as Spag has done here re: absorption, with your concurrence. Why they believe that, I'm not sure; we all grew up with the ability to either pump higher in a swing or slow the swing back down without touching our feet to the ground.
The pumping got me thinking, I gave away my college Physic textbook so I went to Amazon to search for my much hated Halliday & Resnick classic text (only to engineering student who had to suffer two years of this stuff). Instead, I found “The physic of skiing” 2 ed. by Lind and Sanders, it has updated material on the shape skis.

Chap 5 and specifically Technote 10 points out clearly about “pumping” up at the bottom of the trough to pick up speed. The key concept is rotational force and the location of the center of mass. Lind gives descriptions and math equations on kinetic energy when you extend to pump up. Conversely, you can absorb to decrease kinetic energy, thus lose velocity (using equation T10.2).

Overall, it’s good read on why things happen on the slope, however you need a background in Physics for a better understanding this stuff.
post #156 of 166
Quote:
Originally Posted by jack97 View Post
...[snip]

Overall, it’s good read on why things happen on the slope, however you need a background in Physics for a better understanding this stuff.
I'm not sure if getting you reading about physics should make me happy or sad? It's actually one of those things, like turning a bike, which are pretty complex because the parameters of the system vary -- in the case of the bumps, the length of the skier varies through A&E in harmony with frequency & amplitude of the bumps within certain obvious limits. The good news is, I don't think you need to worry about any of the theory to do it, same for turning a bike.
post #157 of 166
Quote:
Originally Posted by CTKook View Post
The good news is, I don't think you need to worry about any of the theory to do it, same for turning a bike.
But I disagree, there’s a lot of data in this forum; some good, some bad. Understanding the physic of the movement (hence the cause and effect) is one way to filter out this data.

Just when I thought I no longer had to worry about torque, angular momentum, centrifugal force… thanks for planting the seed in my head.
post #158 of 166
best bump
post #159 of 166
Quote:
Originally Posted by Bob Barnes View Post

Hi SkiFox--

If it's any help, here's the animation you refer to:



And here's a photomontage of a top level competitor (I'm afraid I don't know who it is) showing the same movements:



This circular movement pattern of the feet beneath the hips is critically important for smooth bump skiing. And it's highly relevant to the current discussion in the thread Moguls/bumps, regarding "carving" down the back side of the bumps.

Is there a strong plantar flexion in the bottom sequence (at two possible points, that is)?
post #160 of 166
Quote:
Originally Posted by comprex View Post



Quote:
Originally Posted by Bob Barnes View Post

Hi SkiFox--

If it's any help, here's the animation you refer to:



And here's a photomontage of a top level competitor (I'm afraid I don't know who it is) showing the same movements:



This circular movement pattern of the feet beneath the hips is critically important for smooth bump skiing. And it's highly relevant to the current discussion in the thread Moguls/bumps, regarding "carving" down the back side of the bumps.



Is there a strong plantar flexion in the bottom sequence (at two possible points, that is)?



Nail's not gonna like this. The stick man isn't "stuffing" his tips into the mogul.

post #161 of 166
Any thoughts, Lars?

Is the skier at bottom pointing his toes down and into the trough between pic 2 and 3 or between pic 5 and 6?
post #162 of 166

I'm usually a lot more comfortable a little too far forward than I am a little too far back in everything except possibly powder on skinny skis.  BAaaaaaaaad things can happen to those that get a bit too far back in the bumps.  But some folks with incredible core strength might be able to achieve the motion being proposed here to some degree.  Even in photo #5 the skier's shoulders are pretty well over his knees which are over his feet (but barely). He's never what I'd call "too far back" in any of the other photos,  He's just not always on the verge of going over the handlebars-which I usually amredface.gif because I have healthy fear of the nonono2.gifback seat predicament. 

post #163 of 166

Just a random observation.

 

My first time Stand up paddling in waves a few Summers ago I discovered perfect balance when paddling out through the waves was just like skiing moguls!  If, as the face of the wave pushed against my board slowing my forward momentum, I pushed my board forward with my feet then, as I passed the crest of the wave, pulled my feet back under me, I could remain in perfect balance.  Just like backpedaling in the moguls this action keeps the balance axis in line with the forces whether it is a paddle boarder balancing over a moving wave or a skier moving over a stationary white wave.

post #164 of 166
Quote:
Originally Posted by bud heishman View Post

Just a random observation.

 

My first time Stand up paddling in waves a few Summers ago I discovered perfect balance when paddling out through the waves was just like skiing moguls!  If, as the face of the wave pushed against my board slowing my forward momentum, I pushed my board forward with my feet then, as I passed the crest of the wave, pulled my feet back under me, I could remain in perfect balance.  Just like backpedaling in the moguls this action keeps the balance axis in line with the forces whether it is a paddle boarder balancing over a moving wave or a skier moving over a stationary white wave.


Good random observation.  Pumptracks, skateparks, etc. all have their similarities too, as does pumping a caught wave to make speed.

 

 

post #165 of 166
Quote:
Originally Posted by bud heishman View Post

 Just like backpedaling in the moguls this action keeps the balance axis in line with the forces whether it is a paddle boarder balancing over a moving wave or a skier moving over a stationary white wave.

Makes one wonder how SVMM technique can claim not to use backpedaling. Is the difference active vs passive?

 

post #166 of 166
Quote:
Originally Posted by Jamt View Post



Quote:
Originally Posted by bud heishman View Post

 Just like backpedaling in the moguls this action keeps the balance axis in line with the forces whether it is a paddle boarder balancing over a moving wave or a skier moving over a stationary white wave.

Makes one wonder how SVMM technique can claim not to use backpedaling. Is the difference active vs passive?

 



CVJ should be the one to answer for SVMM.  Among bumpers in general, there are different levels of focus on A&E -- some say it should be a byproduct of other things, some more of a primary focus.  In one of the other currently active threads, someone (I believe CGeib but could be wrong) noted he thought the term backpedaling may be unfortunate because some interpret it as meaning you move the feet back uphill (actually I think it's just a reference to movement in relation to COM, which is what CGeib was noting).  Whether it's bumps or MTB-ing, or for that matter beachbreak or windchop, the size and spacing of the "bumps" is going to impact how active absorption is, among other things, anyway.

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