What's essential for carving on hard snow?

[James]

Thread closed?

No. Geez how lame would the site be if it can't handle a snarky response? Shutting threads has indirect effects for those not involved in the fracas. Like why bother to discuss these things in the future? It usually wears off, but the more it happens the more side effects. The closing and destruction of epicski had the effect of making some who'd spent a lot of time on these discussions just go away.

I will bet my life that I've taken more physics courses than you have.

Hard to tell. What did you get out of the Reid Thesis posted earlier.

 

[skier]

Hard to tell. What did you get out of the Reid Thesis posted earlier.

I'm sorry. I didn't read it. The link wasn't working for me at the time. It's working now. I'll read it when I get a chance. Thanks.

 

[Uke]

skier,

Its wonderful to think for yourself but you have to accept that your thinking might be flawed and being the lone voice among so many equally experienced people might be a clue.

uke

 

[skier]

skier,

Its wonderful to think for yourself but you have to accept that your thinking might be flawed and being the lone voice among so many equally experienced people might be a clue.

uke

First of all, I'm not a lone voice. Many others have said the exact same thing I'm saying. That's the danger of conclusions based on safety in numbers. You get a micro group all thinking the same way, and then it becomes impossible to progress past wrong information. I knew I'd get bashed for posting these ideas, because around here there are many that are dug in with the opposite position. I am not afraid of the lynch mob, but other people that also know the same things as me are afraid of it, so you don't get many people that want to challenge a group's conventional thinking. Based on my experiences, posts I've read, the literature, the opinion's of experts, and the clear physics, the conclusions are fairly indisputable. And, if you didn't get my irony, merely your opinion isn't enough to have that much sway. I already knew the opinions of many people here in this regard. I took that heavily into consideration, did a fairly comprehensive analysis, and concluded that this particular group is wrong. Contrary to your characterization of me, I am not close minded. I can change my mind when I'm wrong, but you'll have to do more than giving me advice on having an open mind and stating you're an expert. In my opinion, you are a flat lander, because the evidence clearly shows the earth is round, and just because lots of people believe it's flat, doesn't make it flat.

 

[Uke]

skier,

Perhaps in the wider world you are not a lone voice but here you seem to be. So, if we are all wrong and incapable of understanding the obvious why are you wasting your time here? Do you just enjoy acting as a troll or do you still expect us to see the light?

uke

 

[geepers]

Geepers, ever since I told you your mogul dude is in the back seat, you've been harassing me at every chance. I'm sorry it upset you so much, but I've had enough of it, and I'm not going to stand for it any more. This is the me too era after all. The writing is on the wall, you're just not getting it, and I suspect if anyone else wrote it, you'd get it. So, back the duck up, buckle up for a ride, here we go, 100 pages and a thread lock. You're not getting the last word.

Surprised you are taking things so personally. It's just equations and forces, not a personal attack.

Presented with the same information we came to completely different conclusions. One of us came to the conclusion that carving is impossible and I got an insight into how Ted Ligerty sticks to the track.

I'm not going to go through a specific rebuttal of your points - you're quite bright enough to figure it out.

You may, however, want to take a moment to consider exactly what your equations are showing. Try them on this and tell me what speed this bike rider would need to obtain to ride around the vertical walls. At what angle will he have to exceed the speed of light, according to v = sqrt(r*g*tan(theta))?

 

[geepers]

If you want to pure carve a 16 m turn at speed, just tip a 32 m radius ski up to 60 degrees. If you want to do it arc-2-arc with no skidding, make the ski go straight for that small fraction of a second it takes you to reach the critical tipping angle, while your body continues into the new turn under the action of momentum from the previous turn and gravity.

I'm not entirely sure but I think our ski tracks make sine waves (ideally) rather than linked semi-circles.

There has to be some period of time when we are going from perpendicular to the slope at transition to max inclination (ideally around the apex). And then reverse the process on the way out of the turn. This can be done smoothly or abruptly (as you describe above).

 

[geepers]

It has been mentioned once or twice, but I think that the dynamic nature of the loads is not being given enough attention. An "adiabatic" picture, where the history is treated as a sequence of quasi-static situations, is not valid. The forces are not in balance at each individual time.
We get light at transition to reduce the necessary loads. Our center of mass follows a less-curved path than our skis.

Good points as inclination increases. For low speed RR tracks we basically keep our body over the skis.

 

[James]

The ski must cross the path of the skier's momentum such that it feels like the momentum is going into the skis. Jamt and the Physics of Skiing describe that there must be a steering angle before loading to make this happen. I believe this is true too. This is why I believe there is a slight rotary input for many types of turns without skidding.

When the ski is tipped and stood on, it bends and gives you a steering angle. What's wrong with that mechanism?

 

[François Pugh]

I'm not entirely sure but I think our ski tracks make sine waves (ideally) rather than linked semi-circles.

There has to be some period of time when we are going from perpendicular to the slope at transition to max inclination (ideally around the apex). And then reverse the process on the way out of the turn. This can be done smoothly or abruptly (as you describe above).

Yes. Typically my turns decrease in radius to the apex, then increase, more closely resembling a sine curve. Also the angle to which the skis are tipped, does not have to correlate in time to the acceleration on the centre of mass; the body and the skis have separate paths and accelerate at different rates and times. That allows us to pressure the ski into the snow before demanding the ski accelerate us around the turn.

 

[skier]

skier,

Perhaps in the wider world you are not a lone voice but here you seem to be. So, if we are all wrong and incapable of understanding the obvious why are you wasting your time here? Do you just enjoy acting as a troll or do you still expect us to see the light?

uke

Good question! No, I don't enjoy trolls. No, I don't think I will ever convince you. There are some good people here, and I keep learning lots of stuff even though it's unpleasant at times. I thoroughly enjoy @jack97 's posts. If it wasn't for him, I probably would have drifted on a while ago. I'm not interesting in these types of conversations we're having now. I would have dropped it long ago, but it's time I get the last word in with Geepers, otherwise he's just going to hound me every time I post something he didn't learn in his system. Unfortunately, many of you are in the same system, so I can't push back on him without interference.

The question you need to ask yourself though, why does my opinion bother you so much, such that you keep coming at me with no real argument? 1. People disagree with me. 2. Why am I here? 3. You're an expert. 4. I have a closed mind. There's no substance there. You couldn't possibly be trying to convince anyone. Only the choir will agree with you with those kinds of arguments. Those attacks have no purpose other than trying to intimidate me or make yourself feel better about something? Rallying the troops? Backing up a buddy? Bruised ego, because I don't bow down to your expertness? I can speculate, but whatever the reason, it's definitely you that needs to question your motives, because those attacks are honestly nothing but trolling.

 

[skier]

When the ski is tipped and stood on, it bends and gives you a steering angle. What's wrong with that mechanism?

During transition, the body is moving across the skis, so the momentum is moving away from the skis as the skis are being tipped. How can you tip it, bend it, and have the ski turn to catch you when you are moving away from the skis while you tip them? To have the ski come around and catch you, you must have momentum driving into the skis, not away. We're talking about 60 degrees of edge angle, before any carving can happen.. You have to be inside to get that much edge angle. If your that inside with momentum moving away from the skis, then in a fraction of a second the ski will not be bent before it can turn.

You can either start tipping early and have the ski gradually tip and bend to come around in time, or you can rotate the ski at the top of the turn. You can't go straight, tip to 60 degrees instantly and have it catch you. I'm still trying to make time to read that thesis.

 

[François Pugh]

Troll or no, skier's posts have teased out a lot of interesting information regarding carving (OP definition) on hard snow.

 

[François Pugh]

We're talking about 60 degrees of edge angle, before any carving can happen.

Well you are, we are not.

 

[skier]

Well you are, we are not.

I'm just responding to your post where you were explaining how to get past the skidding phase.

If you want to pure carve a 16 m turn at speed, just tip a 32 m radius ski up to 60 degrees. If you want to do it arc-2-arc with no skidding, make the ski go straight for that small fraction of a second it takes you to reach the critical tipping angle, while your body continues into the new turn under the action of momentum from the previous turn and gravity.

Francois, You were right there, I could see it. You followed all the references and were making good conclusions. Then all this banter happened, and you lost it. You were so close to seeing the whole thing, just the last piece of the puzzle is that you can't instantly tip to 60 degrees. It takes lots of illustrations to demonstrate, but it's true.

 

[HardDaysNight]

How is it I can make low speed railroad tracks with just slight ankle tipping movements?

You can because (and this is for @skier’s benefit) those slight ankle tipping movements impart edge angle, however small, to the skis. This results in the ski bending, however slightly, which creates steering angle. Among his other misconceptions is @skier’s apparent belief that steering angle in the context of carved turns is created by twisting the skis; it is not, it is created by bending the skis which begins at the very slightest hint of edge angle. This is why pure arc-to-arc skiing is possible and does not require obligatory skidding, at least not beyond that imposed by the physical qualities of the particular snow surface.

 

[LiquidFeet]

During transition, the body is moving across the skis, so the momentum is moving away from the skis as the skis are being tipped. How can you tip it, bend it, and have the ski turn to catch you when you are moving away from the skis while you tip them? ....

How does one keep the momentarily flat ski (it's only a nanosecond, right?) from rotating or skidding out as the body crosses over it???

There is an answer to that, if I've understood your concerns correctly.

Angulate sufficiently out over the new outside ski, or keep the skis sufficiently up under you (other side of the same coin) ... so that as your released body moves across the skis to their downhill side, the new outside ski maintains a sufficient platform angle with the COM (there's that important term) that assures that it will hold ... even when the tipping edge angle to the snow is slight at first.

With sufficient platform angle, that darned ski won't skid. It's the platform angle that keeps the ski engaged. It's also the restraint the skier imposes on any embedded habit of pivoting the new outside ski at turn entry. And it's the speed with which the skier tips the new outside ski onto its downhill edge before the fall line; this is the "commitment" we hear of so often. Commit, skier! And don't pivot! And keep the darn ski up under you, don't push it out or dump the hip inside. Think: Platform Angle!

 

[HardDaysNight]

just the last piece of the puzzle is that you can't instantly tip to 60 degrees.

No, nor do you need to.

 

[François Pugh]

For the benefit of people playing along at home, (I'm convinced that Skier is just playing Devil's Advocate, especially if he has attended (and passed) as many simple physics classes as I have taught).

You don't need to "instantly" tip to the full 60 degrees that you will have at the apex. You just need to control how much turn force you demand from your skis until they reach a small angle from which you will demand a small turning force. COM and skis travel different paths, forces demanded from skis at small angles to accelerate the body need not be turning forces, skis press down and snow pushes skis up near transition when angles are small. Turning forces gradually increase so that turning forces and vertical forces remain within the critical angle no-slip-sideways requirements from skis flat to skis tipped to 60 degrees.

 

[skier]

For the benefit of people playing along at home, (I'm convinced that Skier is just playing Devil's Advocate, especially if he has attended (and passed) as many simple physics classes as I have taught).

You don't need to "instantly" tip to the full 60 degrees that you will have at the apex. You just need to control how much turn force you demand from your skis until they reach a small angle from which you will demand a small turning force. COM and skis travel different paths, forces demanded from skis at small angles to accelerate the body need not be turning forces, skis press down and snow pushes skis up near transition when angles are small. Turning forces gradually increase so that turning forces and vertical forces remain within the critical angle no-slip-sideways requirements from skis flat to skis tipped to 60 degrees.

Are you Ghost?