Hard pressure on tips while on steeper terrain (Carved short turns?)

[markojp]

+1
And not to mention the surface variations that have to be negotiated. Love skiing those glaciers in Europe with wide open consistent surfaces. But here in the NE we have dumps, bumps, lumps, ice, humps, ruts, nuts - all within the space of a few turns... You have to adjust on the fly and be reactive. Theories and formulas don't work very often.

Just a reality check, but the rest of the world, has mixed conditions. Some of the crappiest, hard surface piste skiing ive experienced has been in Japan. The PNW iis no slouch in generating incredible surface weirdness including very steep rock hard conditions.. just ask any Alpental regular.

Glacier skiing often has a sweet spot time wise for optimal conditions during the day with a lot of variation before and after. Physics is physics. Snow surfaces are variable pretty much everywhere. Video that we most often see is shot in optimal conditions because they don't have to shoot on holiday weekends or in crappy weather.

Anyhow, carry on.

 

[Sanity]

Have I missed something, or is the disagreement in this thread with the mantra of stay forward, not get forward?

The OP asked if it's bad that he stay forward. My answer was that Olympic mogul skiers teach to stay forward throughout the entire turn (constant shin pressure), though I added in the caveat that there are situations where it's not going to happen, and there are advantages and disadvantages based on the situation.

 

[Sanity]

Scratching head...

So what's the difference in foot to CoM speed in a reasonable turn? Let's take 12m radius turn with a speed of 16.631m/s. (Picked those 'cause it gives centripetal accel of 1.414g which is roughly a 45 degree inclination of the CoM.) Let's say CoM is 1 m to the inside so the CoM speed is 16.63*(12-1)/12 which is near enough to 15.245m/s.

So that's a difference 1.386 m/s.

Is that significant? A typical soccer player's foot is moving about 20 m/s when they kick the ball. Typically they don't fall over because they automatically compensate and I'm guessing skiers generally do too when their feet (wrt to their CoM) are moving over 14 times slower.

Rather than look at the velocity gradient, I think a more intuitive way to understand this problem is to look at rate of rotations. If a racer completes a turn in 2 seconds, that would mean a leaned over skier's body would rotate about 180 degrees in 2 seconds. A ski boot has about 14 degrees of forward lean. If you gave up all that forward lean you would be feeling very aft and too aft to initiate the next turn well. So, once the skier releases the pressure and floats, the rate of rotation continues, which means the skier will rotate aft in 14/180*2= 155mS. Or another way to look at it, if the skier floats for just 7% of the time that they spent turning, they will end up aft. Yes, that's significant.

 

[François Pugh]

Thinking some more on your theory...

So we balance against the ski/snow friction and then we release the friction decreases so the feet shoot forward? That it?

First point - wouldn't the friction decrease be larger in softer/heavier snow than hard snow so the feet would shoot out more? 'Cause seems that staying on top of the skis is more of an issue on hard snow than soft.

Second point - it's ignoring the virtual bump which tends to slow the feet turning out of the fall line. Size of that depends on pitch, speed and how far the turn is finished.

Second point - absorb the virtual bump. Do it!

First point, if you are considering the linear momentum a la MV, you've are doing enough. Calculus can show integrating MV of all points of mass going around a circle in a spinning object is the same as I Omega.

Angular momentum, speaking apart from the fact that you are going around a curve, as you skis and legs ski into and out of counter needs to be balanced by the upper body (with some internal tension)which faces the general direction of travel.

 

[François Pugh]

Scratching head...

So what's the difference in foot to CoM speed in a reasonable turn? Let's take 12m radius turn with a speed of 16.631m/s. (Picked those 'cause it gives centripetal accel of 1.414g which is roughly a 45 degree inclination of the CoM.) Let's say CoM is 1 m to the inside so the CoM speed is 16.63*(12-1)/12 which is near enough to 15.245m/s.

So that's a difference 1.386 m/s.

Is that significant? A typical soccer player's foot is moving about 20 m/s when they kick the ball. Typically they don't fall over because they automatically compensate and I'm guessing skiers generally do too when their feet (wrt to their CoM) are moving over 14 times slower.



Not sure why there's this huge focus on forward/forward/forward once we get past the beginner/intermediate phase of tentative backseat skiing. I'm with the US Team guy in that what goes back has to return. And vice versa - what goes forward also has to return. There's an interesting part in a Tom Gellie vid where he drylands the difference in his fore and aft positions in a carving turn. It's very small and yet he's quite capable of high edge angle turns on a variety of pitches.

Perhaps we should be more like Feutz who apparently is center of the ski top to bottom. (That's Sam DuPratt's opinion on Feutz and presumably a guy whose been on the USA ski team a number of times has some insight.)

Short distances do count in angular momentum conservation - witness the figure skater bring her arms in to spin faster, or try it yourself on a bar stool (so long as you're not too drunk )or spining office chair.

 

[Scruffy]

The OP asked if it's bad that he stay forward. My answer was that Olympic mogul skiers teach to stay forward throughout the entire turn (constant shin pressure), though I added in the caveat that there are situations where it's not going to happen, and there are advantages and disadvantages based on the situation.

Yeah but, the OP is not an Olympic mogul skier, or an expert WC racer, or an expert level carve-aholic recreational skier. Intentionally getting forward, or intentionally getting back are tools ( metaphorically speaking). Like any set of tools there are beginner tools and usage of, and advanced-expert level tools and the usage of. Context is everything. Red slopes are intermediate level.

 

[Zirbl]

Yeah but, the OP is not an Olympic mogul skier, or an expert WC racer, or an expert level carve-aholic recreational skier.

Red slopes are intermediate level.

Depends how you ski them doesn it?
The OP said he couldn't carve anything more than a European red without picking up too much speed. That would imply he is comfortable carving most terrain and has been trying to carve on blacks. If that's the case, he can't be too bad at carving.

The OP asked if it's bad that he stay forward.

My recollection is that he was talking about getting so far forward that he lightened the tails to brush them out.

 

[Rod9301]

I studied nuclear physics, so math is pretty easy for me. But all these attempts of understanding skiing thru math are going over my head. Not to speak of that they are pretty wrong to reduce skiing to math, even if it makes some people feel good about themselves.

 

[Zirbl]

There's an interesting part in a Tom Gellie vid where he drylands the difference in his fore and aft positions in a carving turn. It's very small and yet he's quite capable of high edge angle turns on a variety of pitches.

I think it's fair to say that some very high-end skiers express ideas on fore-aft in carving that are very different to the stuff Tom Gellie repeats from Jurij Franko, so I wouldn't expect too much agreement there, even if what they're saying is correct.

Perhaps we should be more like Feutz who apparently is center of the ski top to bottom.

Doesn't it depend on the ski? I.e. some want more tip pressure, whereas some are designed to be skied under the bindings? Throw in binding placement too.

 

[Scruffy]

Depends how you ski them doesn it?
The OP said he couldn't carve anything more than a European red without picking up too much speed. That would imply he is comfortable carving most terrain and has been trying to carve on blacks. If that's the case, he can't be too bad at carving.


My recollection is that he was talking about getting so far forward that he lightened the tails to brush them out.

Sure - reread my post. No need to defend the OP as he wasn't slighted. We haven't seen him ski, but even if he is the most awesome blue square/red slope carver on the planet my post still stands. By his own admission and seeking help, he is having trouble controlling his speed on anything steeper than red.

I'm not comfortable carving anything steeper than a European red because I hit warp speed too quickly.

By his own admission he has tried slamming the cuffs and then brushing his tails on steeper terrain, and this sorta works for him, but he sees others not doing that, and wants help from us to see if there is a better technique he can work on to obtain the skills to carve steeper slopes.

Then we get into thread drift that argues over one of the perennial arguments here on the forum - getting too far forward and pressuring the cuffs all the time. Then the thread drift drifts farther into what Olympic WC skiers do.

I mean, thread drift is inevitable here, but let's not get too far into the weeds

 

[Zirbl]

@Scruffy I see, seems we're on the same page then. Apart from:

Then the thread drift drifts farther into what Olympic WC skiers do.

It wouldn't be much of a discussion about carving steeps if it didn't.

 

[geepers]

Rather than look at the velocity gradient, I think a more intuitive way to understand this problem is to look at rate of rotations. If a racer completes a turn in 2 seconds, that would mean a leaned over skier's body would rotate about 180 degrees in 2 seconds. A ski boot has about 14 degrees of forward lean. If you gave up all that forward lean you would be feeling very aft and too aft to initiate the next turn well. So, once the skier releases the pressure and floats, the rate of rotation continues, which means the skier will rotate aft in 14/180*2= 155mS. Or another way to look at it, if the skier floats for just 7% of the time that they spent turning, they will end up aft. Yes, that's significant.

That would assume we wait until one instance and then release everything. It's not the same case as whirling a rigid body around on ta string and then releasing it - where it would rotate about it's own CoM as it flew off.

Watch these two vids of Lorenz. The torso is already on its way from low to the snow inside the old turn towards the new turn while the feet are still tracking across the hill. The body and feet are moving in 2D (sometimes 3D). If there's a big corrective movement to overcome being aft please point it out.

Second point - absorb the virtual bump. Do it!

The virtual bump was just one of many other factors that affect a skier's fore aft balance. Not heard anyone mention turn induced inclined angular momentum backseatedness as something to be concerned about before.

Casting around for something vaguely similar.... consider adverse yaw induced by banking an aircraft. (Orville Wright was the 1st to figure that one out so invented the rudder.) It's inherent in all winged aircraft. This is quite a big deal for planes with a high aspect ratio wing (like a sailplane) and needs a fair input of rudder to correct. It gets a mention very early in flight training. It's a minor deal on a light plane (like an LSA class ultralite with lower aspect ration and a big fan at the front) and only needs a smidgeon of rudder. It gets mentioned as an afterthought somewhere in flight training, typically in steep turns when chasing your own prop wash. It's of no consequence on a hang glider - they don't have rudders - and doesn't get much of a mention at all.

An alternative suggestion for any feeling of backseatedness...?? From a Lorenz article...

I studied nuclear physics, so math is pretty easy for me. But all these attempts of understanding skiing thru math are going over my head. Not to speak of that they are pretty wrong to reduce skiing to math, even if it makes some people feel good about themselves.

Fair enough!

I think it's fair to say that some very high-end skiers express ideas on fore-aft in carving that are very different to the stuff Tom Gellie repeats from Jurij Franko, so I wouldn't expect too much agreement there, even if what they're saying is correct.

It's probably all good. Until the tails head for the valley.

Doesn't it depend on the ski? I.e. some want more tip pressure, whereas some are designed to be skied under the bindings? Throw in binding placement too.

Yeah - Franko makes that point re stiffer skis.

 

[Sanity]

That would assume we wait until one instance and then release everything. It's not the same case as whirling a rigid body around on ta string and then releasing it - where it would rotate about it's own CoM as it flew off.

If it's a quick release then the skier actually rotates back. If it's a slow release, then the skier pressures the tails to keep from rotating back, i.e. aft. The rotation is always there and tail pressure stops the rotation, therefore skiers are aft at the end of the turn.

 

[Zirbl]

Franko makes that point re stiffer skis.

Sorry, which point?

 

[François Pugh]

Back to the figure skater. I had fun as a young adult getting wired for sound and going out to play with friends in the children's playground of all places. A bunch of us would spin the merry-go-round up to speed and then everyone, except one person would charge the centre of the merry-go round. The person on the outside had trouble hanging on, that merry-go round speed up so much.

Now consider a skier at the apex, legs straight, spread out as it were. Compress and do a cross under turn - the mass spins faster. The skis go faster. Something to think about.

I didn't really notice any real effort required to get back forward for the next turn, making DH and SG turns at speed. However, when I started doing a rapid succession of quick transition cross-under turns learned on my SL skis while doing tight GS so-so SL turns at high GS speeds it took real effort.
BTW I am a recreational skier, never raced.

 

[James]

The OP asked if it's bad that he stay forward. My answer was that Olympic mogul skiers teach to stay forward throughout the entire turn (constant shin pressure), though I added in the caveat that there are situations where it's not going to happen, and there are advantages and disadvantages based on the situation.

Comp mogul skiing is probably the most specialized.

Not exactly round turns here. It’s just different.
At 0:40 on groomed-

 

[Sanity]

Comp mogul skiing is probably the most specialized.

Not exactly round turns here. It’s just different.
At 0:40 on groomed-

My version:

 

[geepers]

If it's a quick release then the skier actually rotates back. If it's a slow release, then the skier pressures the tails to keep from rotating back, i.e. aft. The rotation is always there and tail pressure stops the rotation, therefore skiers are aft at the end of the turn.

If those Lorenz turns aren't quick enough release please post vid of some that are.

 

[geepers]

Sorry, which point?

Intermediate skis need less fore/aft input to make them lose grip than advanced skis which need a larger input. That was from his time at Elan way back.

 

[Zirbl]

Intermediate skis need less fore/aft input to make them lose grip than advanced skis which need a larger input. That was from his time at Elan way back.

Ah right, I meant where on the ski you give the impulse, not how much.