Kneale Brownson

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This thread is getting interesting. I had no idea that PSIA examiners were paid employees of their regional PSIA. Oh, wait, so it's an employee only in the sense that they get paid to teach those clinics that PSIA runs for instructors. Yeah, that makes sense.

@Mike King, are you implying that the "job interview" looks for qualities in the examiner candidate that go beyond skiing and teaching to the standards established for examiners? If so, what?
Not Mike, but I've participated in several PSIA "job interviews". At the end of one, I was asked if I'd shave off my whiskers in order to get the "job".
 

Kneale Brownson

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This poses another question. Is the correlation in passing the exam and ski width really due to the narrower ski being better suited to the task, or are there other reasons as well?
Performing the task appropriately on the wider ski would require greater skill than candidates who did not develop their skills on narrow skis might have, if that makes sense to you. In other words, the more narrow ski might be easier to use for completing the tasks to standard if you have the skills required.
 

markojp

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In the end, off piste, narrow skis require more accurate movements and sometimes different tactical considerations. On piste, narrow skis are easier to ski with the precision of snow/ski interaction that examiners are looking for.
 

Mike King

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@LiquidFeet, as I’ve never been through the process (after all, I’m a very part-time instructor and only a Level 2 at that), someone else should answer — @Kneale Brownson already did so.

@Skitechniek, here’s my interpretation of the graph, the video, and integrating both with my experience. Wide skis, much wider than what you define as wide (say over 90 cm) cause different biomechanics than narrow skis. They result in pushing the ski in the late shaping and finish phases of the turn and use different mixtures and intensities of muscles. Our exams have a skiing element where the examiner looks at the ski performance you obtain for requested maneuvers (these are selected to isolate and demonstrate ski performance). If you’ve never learned how to maximize ski performance, you are unlikely to pass Level 3. Pushing the skis is not what the examiners are looking for. So if you are skiing on a tool that biomechanically results in ski performance that’s not what the examiners are looking for, you’re not likely to pass. A narrow ski is better suited to learning the movement patterns that result in the ski performance examiners are looking for.

Showing up for an exam on skis that are wide could give the examiner a hint that you might not own the movement patterns they are looking for.

Mike
 

crgildart

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Just for total hyperbole... Without having any clue of the conditions to be encountered, given only two choices of A, sub 70 under foot or B, over 100 under foot, who would choose B for their first attempt at a certification exam? I'm guessing only someone who has spent over 90% of their entire ski career on skis over 95mm would choose B.
 

Kneale Brownson

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Only sub 70 ski I own is a pair of K2 Motto SLs that are very old in years, not ski use, and have NTN tele bindings. They're 65 mm under foot. My most narrow otherwise is the Nordica 84 EDT. Interesting that both are marked as 17 meter skis. My daily driver for both ski school and personal skiing is 93 under foot. I'm too old to be an exam candidate. This will be my 80th winter.
 

James

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@LiquidFeet, as I’ve never been through the process (after all, I’m a very part-time instructor and only a Level 2 at that), someone else should answer — @Kneale Brownson already did so.

@Skitechniek, here’s my interpretation of the graph, the video, and integrating both with my experience. Wide skis, much wider than what you define as wide (say over 90 cm) cause different biomechanics than narrow skis. They result in pushing the ski in the late shaping and finish phases of the turn and use different mixtures and intensities of muscles. Our exams have a skiing element where the examiner looks at the ski performance you obtain for requested maneuvers (these are selected to isolate and demonstrate ski performance). If you’ve never learned how to maximize ski performance, you are unlikely to pass Level 3. Pushing the skis is not what the examiners are looking for. So if you are skiing on a tool that biomechanically results in ski performance that’s not what the examiners are looking for, you’re not likely to pass. A narrow ski is better suited to learning the movement patterns that result in the ski performance examiners are looking for.

Showing up for an exam on skis that are wide could give the examiner a hint that you might not own the movement patterns they are looking for.

Mike
How are the "biomechanics" different since the bio is the same?
 
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geepers

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How are the "biomechanics" different since the bio is the same?
The presentation covers that. Short summary - wider skis involve greater forces on leg joints in some phases of the turn in certain conditions so skiers adjust.

Watch vid for more detail.
 

Steve

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I have not seen any systemic disdain or animosity towards ski instructors in my life.
People may not like the way some of us ski. But nothing personal against us.
 

crgildart

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I have not seen any systemic disdain or animosity towards ski instructors in my life.
People may not like the way some of us ski. But nothing personal against us.
We save the animosity for snowboarders... Kidding of course. I'll share the goods with anyone as long as they're not talking politics..
 

mister moose

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How are the "biomechanics" different since the bio is the same?
The presentation covers that. Short summary - wider skis involve greater forces on leg joints in some phases of the turn in certain conditions so skiers adjust.

I skimmed the video, am far less qualified, but have a different or maybe additive take on it. The video looks at the foot in the boot without looking at where in the skeletal structure the loads are carried. From the video:


Lever armV.jpg

In the video the origin of the lever arm (r) is depicted smack dab in the center of the boot. Also, the boot is shown on the pinky edge, or the inside ski in a turn.


This is my drawing:

Lever arm.jpg

Here we see that the tibia is not in the center of the boot. The main load bearing bone is far closer to the big toe than the pinky toe. Also, the big toe edge is the outside edge, and bears more pressure than the inside foot. For the above diagram I measured my foot, and estimated where a 100mm ski would sit under my foot given the entire foot is centered on the ski. I then took 70% of that graphically, and centered that distance. Because the tibia is not centered over the footbed, the arm comparison the video suggests I think is not correct. This depiction suggests the difference is greater that the video depiction, and therefore the effect of the greater lever arm is even more pronounced. In this case, a 100mm ski on me would have twice the lever arm on the tibia centerline than a 70mm ski.

This is a sketch, not a calculation. But with the tibia aligned with the big toe [NOT the ski boot center], I think I can safely say the lever arm has greater effect than so far discussed. The effects on the knee, and the lateral compression in the upper boot cuff are significantly greater on wider skis. Can it be compensated for? Of course. But the bio mechanics of applying pressure to the outside ski edge certainly change as the ski gets wider.

Do you feel stronger on your big toe edge or your pinky toe edge? Ever wonder why?
 
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Erik Timmerman

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I'll tell you this. I went to the Eastern Team Tryout this year on my (slightly worn out) 86mm wide all mountain skis. I had ben hoping to bring brand new 86mm all mountain skis, but that didn't happen. I knew that a lot of the people competing would be on FIS GS skis or cheater GS skis. I could have brought my Fischer Curvs and I do have a 25m Masters GS ski that is really nice, but I was expecting a lot of bump skiing. My thought going in was that a GS ski is a mistake and also that it is inappropriate to use one. I felt that we should be on skis that are like what our students ski on. I have never, ever had a person show up for a lesson on a GS ski of any kind. It pretty much only took me one run to realize I had made the wrong choice, and we didn't really ski any bumps, so my skis never had a chance to shine.
 

fatbob

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Also, the big toe edge is the outside edge, and bears more pressure than the inside foot.

Do you feel stronger on your big toe edge or your pinky toe edge? Ever wonder why?
I think you've baffled me there. I understand you criticising the original diagrams because they are showing an inside/non dominant ski but my big toes are always the inside edge of both skis and definitely on the dominant edge (of the outside ski) in a turn.

I get the point on tibial alignment but surely everything should be measured by reference to lateral centre of ball of foot rather than toes? Maybe defeining ball of foot is also open to interpretation?
 

LiquidFeet

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I'll tell you this. I went to the Eastern Team Tryout this year on my (slightly worn out) 86mm wide all mountain skis. I had ben hoping to bring brand new 86mm all mountain skis, but that didn't happen. I knew that a lot of the people competing would be on FIS GS skis or cheater GS skis. I could have brought my Fischer Curvs and I do have a 25m Masters GS ski that is really nice, but I was expecting a lot of bump skiing. My thought going in was that a GS ski is a mistake and also that it is inappropriate to use one. I felt that we should be on skis that are like what our students ski on. I have never, ever had a person show up for a lesson on a GS ski of any kind. It pretty much only took me one run to realize I had made the wrong choice, and we didn't really ski any bumps, so my skis never had a chance to shine.
Eric, I hope you did well in those tryouts.
I have three questions.

1. How would a GS ski have behaved differently for you in those tryouts?
2. What did they ask the candidates to do that would have worked better with a GS race ski (FIS or cheater)?
3. Would that advantage have been because of waist width, turn radius, torsional stiffness, tail shape, longitudinal flex profile, all of the above (well, now that's what I'm thinking given that I wrote that out) or something else?
 

James

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Nah, now you're at the Austrian logic. Deal on a gs cheater type or go home. You can go through all sorts of logic, but in the end it's what those running it think. It's definitely harder to ski it where it wasn't made for, so it has meaning.

But, why did men have to ski 200cm + for years and years? Can't see a good reason.
 

crgildart

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But, why did men have to ski 200cm + for years and years? Can't see a good reason.
A hockey stop or hard pivot check turn on a 200+ cm ski has a lot more bite than one on a 165 cm ski. The snow was also softer and not injected ice back then. And, you had to go around the gates more. Not as easy to push them down and ski over them.
 

Erik Timmerman

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Eric, I hope you did well in those tryouts.
I have three questions.

1. How would a GS ski have behaved differently for you in those tryouts?
2. What did they ask the candidates to do that would have worked better with a GS race ski (FIS or cheater)?
3. Would that advantage have been because of waist width, turn radius, torsional stiffness, tail shape, longitudinal flex profile, all of the above (well, now that's what I'm thinking given that I wrote that out) or something else?
Gotta be honest, it didn't go that great. I managed to have my one sick day of the year (caught the crud being passed around ski school) on the first day of the tryout, but really I just was not skiing that well. The tryout was at Iceface and I pretty much skied soft snow or crazy injected freeze/thaw/freeze snow all season. The snow at Iceface was a very grippy ice, an unforgiving surface. The first task was short radius turns (which I happen to think I do very well) on that Olympic trail under the lift with the big timing house at the bottom. It is steep, and I knew I was gonna have a problem after my first turn. Maybe not so much the skis, but my boots were way too positive and it was hard to make the ski slide. I think that I could have made a better short turn on either my Curvs or my GS skis in that condition. Maybe all I needed there was a boot adjustment, I don't know. The only bump skiing we did was a "GS turns in the bumps" run where the bumps were distantly, randomly spaced bumps on a chunk of ice. The grip was fine, my skis were fine there, but the young guns were really skiing it f a s t and the examiners seemed to be eating that up. I would have liked more stability from a stiffer ski on the bottom half of that run. One of the last runs was GS turns on the Olympic downhill trail, GS skis would have been great there. I felt like my skis were going to fold in half. I hope that helps.
 
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