EpicSki › The Barking Bear Forums › On the Snow (Skiing Forums) › General Skiing Discussion › paging physics man.....4 speed skiing
New Posts  All Forums:Forum Nav:

paging physics man.....4 speed skiing

post #1 of 25
Thread Starter 
PM,
I was told by a speed skier once that when he hit a certain speed he was on a cushion of air, not the melted snow suface us mortals ski on. is this true? what is that speed?
Thank you,
Matt :
post #2 of 25
Hmmmm, never heard that one, air hugh?

Snow is frozen water, the ski base and is designed to hold wax, the wax assists in providing a water barrier.

It is true that the ski slides along creating friction and therby producing a water vapor or barrier which is slides along on.

Wax beads the water very effectively which is why it slides a bit better than no wax. There are different types of wax for the various conditions. Altough an Orange or Red may work on most days for Alpine.

In Nordic the Wax or Glistner is much more important as we use it for not only the SLIDE but also the GRIP. You really learn alot about wax and water skiing when you take on Nordic. We have some base prep that is so sticky I still have some of it stuck to a ski rack somewhere!
You can put this stuff on the bottom of a nordic ski and get a push on ICE!

I would have to guess that at over a hunderd miles per hour the snow may not have enough time to vapor before you are over it! Also the friction causes the ski to adhere to the snow, this can create a vacume, proper wax is needed to keep this from happening. At that speed the ability of the vacume to build may be reversed and the friction casues the frozen water to go gasious therby producing the "Air" which the ski rides on.
I have seen the tracks left by the speed skiers and they look the same as other skis, you can see the result of the water produced by the friction as the glassy sheen in the flat part of the ski track.
Never had to wax for 100+. But waxing pricipales remain the same, I am sure.
post #3 of 25
Matt
I used to write on this subject and was lucky enought to visit the fastest track in the world (Les Arcs, France) on a few occasions.
This phenomenon of riding on air has been mentioned by speed skiers, in the same sense that a skimming stone across water will do the same. I can't account for its scientific validity, but it's more than likely true.
I've certainly seen speed skiers (and the current record holder Harry Egger made an attempt on 250 km/h last winter) ski with their skis tilted on to their parallel inside edges to maintain stability.
The view down from the top of the speed track is most frightening sight I've ever seen in my ski career.
And you should see them fall...
post #4 of 25
<BLOCKQUOTE>quote:</font><HR>Originally posted by matt_davis:
PM, I was told by a speed skier once that when he hit a certain speed he was on a cushion of air, not the melted snow suface us mortals ski on. is this true? what is that speed? Thank you, Matt :<HR></BLOCKQUOTE>

Matt -

We all ride around on a ultra thin cushion of liquid water when we are skiing. However, on equipment that is normally used for SL, GS or DH, I don't think anyone is ever going to get completely airborne at DH speeds or below, even if they are on wide jumping skis (or any other ski with wide tips).

Clearly, someone already airborne on wide jumping skis is going to get a substantial degree of lift from the air hitting the bottom of their skis, but this is very different from the situation you are interested in where the ski is flat on the snow, and the airstream is only hitting the turned up tip.

When skiers report that they feel like they are "floating on a cushion of air", I think that what they are most often feeling is a reduction in tip pressure caused by the ram effect of the air on and under the tip. The whole ski doesn't need to lift off the snow for the ski to feel "light" or "quiet" or unusually easy to pivot.

The conditions under which this would happen require:

1) An *extremely* smooth but fairly hard surface;

2) Skis with wide tips;

3) Skis with a soft forebody;

4) Moderately high speeds (50 mph might do);

5) A perfectly flat ski.

To get a feeling for the plausibility of this effect, stick your hand out a car window at 50 mph. Angle it up 45 degrees, and you will feel several pounds of lift on your hand. Your hand is roughly the same surface area as a ski tip, thus, there could be several pounds of force lifting up on your skis tip. Now, while someone is standing on the snow, lift up on their ski tips just enough get them off the snow. Somewhat surprisingly, for most skis, but particularly, soft powder skis, it only takes a few pounds to begin to lift the tips. Thus, there might be enough aerodynamic lift on the tip to lift it up a bit, but it would require VASTLY more force to lift the whole ski off the ground. There might be enough lift to do this at speed skiing speeds, but there are too many variables for me to predict this accurately.

Other phenomena occur at high speeds on flat skis that could generate a similar sensation. For example, enough heat can be generated when a fully loaded skis is traveling at high speed not only for the snow to turn to liquid, but for the wax to melt. When this happens, there will be a sudden change in friction that might also be mistaken for "going airborne".

The reason I am familiar with this general phenomena is that one day last season, I was caught at the end of the day on a wide, long, totally empty low blue cruiser on my powder skis (Volkl Explosivs with 120 mm wide soft tips). The snow was fairly hard and groomed / melted / refrozen to mirror smoothness. I was in a big hurry, so I straightlined the run on flat skis. I have no idea what speed I was going (certainly no more than 50 mph, and probably more like 40), but above a certain speed, my skis suddenly get very quiet, suddenly become frighteningly easy to pivot, etc. Subsequently, I wondered what was going on, chatted with a bunch of people about it, did a bunch of calculations (eg, stagnation pressure, lift, etc.), and came to the conclusions I stated above.

If anybody is interested in the details of the feasibility calculations, I can describe them in subsequent posts, but I think that the only absolute proof of this tip lightening phenomena would be to instrument up some skis and run some RW tests.

Hope this helped,

Tom / PM

<FONT COLOR="#800080" SIZE="1">[ November 24, 2001 01:57 AM: Message edited 1 time, by PhysicsMan ]</font>
post #5 of 25
<BLOCKQUOTE>quote:</font><HR>what they are most often feeling is a reduction in tip pressure caused by the ram effect of the air on and under the tip. The whole ski doesn't need to lift off the snow for the ski to feel "light" or "quiet" or unusually easy to pivot.<HR></BLOCKQUOTE>
I think that after sufficient speed is reached, the tip of the ski is lifted enough to bend the front of the ski into a more de-cambered position, effectively turning the entire front half of the ski into an extra-large tip. This effect should get approximately half of the ski airborne and add to the ability of the ski to plane.

<BLOCKQUOTE>quote:</font><HR>
I have no idea what speed I was going (certainly no more than 50 mph, and probably more like 40)
<HR></BLOCKQUOTE>
You’d be surprised, I bet you were going even faster than you think….
Me & some buddies once borrowed a police radar gun and dragged it up to the hill. Powderhorn run at Sierra@Tahoe is a short, medium-pitch blue run with about 600 feet of vertical on it’s steep section. We got out there for the first run of the day, which was a typical icy spring morning. The radar showed that 40 MPH wasn’t very fast. In fact, old men cruising along making GS turns were pushing 50. The Racer-Groms were riding their tails down in the 50’s and those of us actually trying to go fast were blowing them all away. All of the snowboarders there were hitting 60+. I (the only skier) managed to reach eighty on my first and only run. And this was all on a short intermediate run. I bet you were getting close to that yourself on your run.

<BLOCKQUOTE>quote:</font><HR>but above a certain speed, my skis suddenly get very quiet, suddenly become frighteningly easy to pivot<HR></BLOCKQUOTE>Don’t ya just LOVE that feeling

<BLOCKQUOTE>quote:</font><HR>
If anybody is interested in the details of the feasibility calculations, I can . . . instrument up some skis and run some RW tests.
<HR></BLOCKQUOTE>Can I be the Gunea pig for this? :


Oh,by the way...
post #6 of 25
As a glider pilot I would call it gound effect. The density of the air on a cold surface like snow or ice would be greater than that of ambient temp. Certailnly the speed of the ski and the aerodynamics that has been shared are part of this theory.
However on a pair of skis, this call it hydrofoil or hydroplaining is a lose of control and would not be efective in achieving the goal, that of speeds in excess of 100+ mph. (and live to tell about it)
Here too the friction of the snow and wax would hold back the skier from attaining the goal.
So an optimal solution would be an air cushion not much more that lets say "Air hocky" where one could skim the surface breaking the bond of the ski base and water film of traditional skiing. This does allow for some airdam effect by the ski tip however too much of that would be lose of control. (that is why the tip of a speed ski is so low)
I did consult a ski tune pro., about the wax theory. A hard wax mix is best because of the speed and high friction. There are some silicone mixes out there which may be optimal for this type of skiing.
Remember it is all about electrons. Watch the snow as the sun hits it, or a pond on a cold morninig as the sun comes up and acivates the alge therby heating the water surface. The particles which we see as "steam" or "smoke" coming from the surface escaping into the air are actulay electorns being released.
This same electron release occures while skiing. Now with this in mind there are several mixes which would accomplish this or aide this besides wax. My thought here is that Wax in the traditional sense would become prohibitive at such high speed and temprature as you will ultimatley see above 100+ mph.
Now as my tech tells me he can share this MIX with you however he would have to kill all of us as it is TOP SECRETE.
But a treatment of the base to CLOSE not OPEN the base structure could be prudent at these speeds. (we open the base structure in normal ski waxing to allow the wax entry and ability to fill)
I would speculate that this would be done electronicaly and that a treatment again of a silicone which could work at high temprature on the TEFELON base might work well. (as you know Teflon is not normal base material, but for this application it might work well as it has a more dense structure and it holds up to high friction and temp, while maintaining the integrity of its surface)

<FONT COLOR="#800080" SIZE="1">[ November 24, 2001 06:39 AM: Message edited 1 time, by Dr.GO ]</font>
post #7 of 25
THINKING OUT OF THE BOX FOR A SECOND.
The high density of the H2O molucule would be useful IF a ski could be made which would take advantage of that.
Our new Fighter Aircraft use vector jets to control wing surfaces.
Suppose that along the base of the ski we had several thousand tiny vector openings. Now out of those send Hydrogen gas. (if you don't explode) The introduction of the H would promote more of the O2 to release. Actualy the H2O is O2+H2O, or a very heavy concentration of Oxygen vs the traditional mix of H2O, again the release of electons are from the O2 hooking up with other atoms of H as the hard solid becomes gas. As you know the electrons slow in the cold, so more Oxygen is in there to get out. They are packed in there so tight, that is why the air during winter smells so right. There is an Ozone that is produced from so much traped O, that is released as the solid turns back to gas. So you ride on a surface of H which is trigering a release of O2 therby pushing you along instead of pulling or creating friction.
It is WAY out there but you understand the pricipal now.
post #8 of 25
The particles which we see as "steam" or "smoke" coming from the surface escaping into the air are actulay electorns being released.

Isn't this called Evaporation(Liquid-Gas) and a change of state from(Solid-Gas)is known as Sublimation? If so,then Molecules(Electrons?) of a material are being expelled creating Kinetic Energy. Doesn't the release of Electrons change the properties of a substance not it's state?

Watch the snow as the sun hits it, or a pond on a cold morninig as the sun comes up and acivates the alge therby heating the water surface.

I was always under the impression that the reason steam or fog from a body of water was created by the sun warming it was because the water has more Kinetic Energy than the ground surrounding it thereby starting the Evaporation process more rapidly than the ground. Alge may have a part in it but it's Molucules(Electons)are not stimulated as readily as it's enviorment. I maybe all wet and just a Truck Driver to boot.

<FONT COLOR="#800080" SIZE="1">[ November 24, 2001 09:46 AM: Message edited 1 time, by slider ]</font>
post #9 of 25
Good SLider,

Yes BOTH.

Here is where I think the "AIR" is coming from.

Not the Aeordynamics but the change in State or Properties as the SKI at SPEED creates that effect.

We can free those electons by exciting the atomic structure. Friction = heat or the sudden impact of the pressure or realeas of pressure. That is where clouds come from. Ever been in the cabin of a high altitude plane? See the cloud form from the seal being released or from the sudden decompression. CLOUD!

In the atmosphere there is this RIPPING of the air by forces. Lets just say forces for now.

SO we have this surface of really reduced atomic activity made up mostly of H and O. There are several forcs acting upon it.
Kenitic energy, the mass of the entire sruface, the solar energy imparted by the sun, and the energy of the ski.

IF we were speed skiers we sould know there is an optimal time to be OUT there. We do not want the snow mushy but we DO WANT THE SUN JUST RIGHT!

THe photons actualy will knock some of the electons lose as they strike the O and H atoms, from just sheer force of the impact. Secondly there will begin to be friction with in the mass. Just as the strike is taking place we want to be THERE. This time ZONE will vary for it's optimal purpose of SPEED through the release of the Electron. It is sort of like the "Rise" in Trout fishing. There comes a time when the littel critters hatch and come to the surface. It is not all at once and it may last a while depenting on many factors.

What we do not want is TOO much Friction whithin the mass. Why, becasue this is where the MUSH begins. (basic Atomic stuff)

Generaly speaking the compression of the atomic structure and the forces acting upon them will creat a shift, change altering of the state. Here we are attempting to use it to produce a reduction in friction. As the question was posed a cushion of air.

I say yes this is possible, through the described actitivtes. I am not a proponent of the Aerodynamic theory of Ram air, as this will create a loss of control. (warm or ambient temp air mixing with high density low temp air off the surface) GO look at the river in Oregon as it dumps into the the ocean for an example of that one.

But I am theorising about the proper and subtle method of getting the ski to lift on a cusion of air through the process familure to us who SKI at lower speed and therfore friction. In fact I might just go out on a limb here and say not a cushion of air but a bed of Electrons, which push the ski and skier away from the surface much like a magnetic train would float above the rails.
post #10 of 25
SLIDER,

Available energy in a biological Vs inert matter.

OK we have two ponds, one is crystal clear, so not bioloical the second is green with stuff.

The green one will have the "steam" and the Clear one will not. Well not as quck. Why? Cause the clear one will "steam" but not until the sun penitrates the water and can get toe the bottom creating a bounce of the photon which as in our thoughts about the friction in the mass above creates the heat of force to release the electrons.

THe alge immediatly begins to react with the enviroment producing a heat which will allow the traped O2 to get out. I have seen you too, but maybe you have not noticed. Ponds which are not in DIRECT sunlight release these electrons. WHY? Cause the alge needs littel light to begin their thing. Some alge actualy is still doing theri thing in the dark from the day before. Call it stored energy. I fell in reality it is that the littel beasts are sill poopong form all the stuff they ate and did when the sun was out!

There is much more energy in biological than inert.

Lets see, how can I prove that to you....Well take OIL for instance, or coal. Tremendous energy right. Well take my word for it there is more energy in a pound of coal than ten pounds of granite. Why, coal is a biologic compressed and stored. Granite is an inert compressed and stored.

Ok Ok, let me aim a little closer to home.

Remember the move MATRIX? Why did those nasty DOt COm guys use humans or "copper tops" rather than the solar energy or some other cosmic stuff? Hugh Hugh?

SO there!

Hope all your thoughts are happy thoughts about skiing!
post #11 of 25
Very Interesting but....all that Molecular Theory is making my head hurt.
Just kidding. Back to the subject of skiing. I figured those guys were skiing on air cause it was so damn steep they were free falling. Over.
post #12 of 25
Yeah that is actualy the Holy Grail of the sport.
To attain TERMINAL VELOCITY, that speed at which the human body free falls.

As seen or experienced by skydivers.

This would mean that in reality the only resistance the skier had was the same wind resistacne that a sky diving cousin would have had.
This would ultimatley mean that they would have to overcome the FRICTION of the ski.

WHich is exactly why we are having this discussion.
post #13 of 25
<BLOCKQUOTE>quote:</font><HR> The particles which we see as "steam" or "smoke" coming from the surface escaping into the air are actulay electorns being released. <HR></BLOCKQUOTE>

Unfortunately that is completely false. Electrons are way too small to see, the movement of electrons is what electricity actually is. Lightning is a good example, the friction in the clouds above creates a static charge and when it becomes high enough it will arc with the ground (to neutralize the charge).

When a substance goes from solid to liquid or solid to gas it's because it's amount of kinetic energy is increasing due to the energy is is recieving from the sun, and as the molecule vibrates more it separates from the other molecules. This lowers the density of the substance and the higher density of the substances around it will force it upwards.

<FONT COLOR="#800080" SIZE="1">[ November 24, 2001 11:40 AM: Message edited 1 time, by Mike B ]</font>
post #14 of 25
Yes Mike B,

Electrons are way too small for you and I to see.

A few billion of them might look like smoke, a couiple of quatrillion might look like a cloud.
A few tera GODZILLA might even stike you dead.

But alas we are talking about a few trillion secaping the surface of a pond.

What happens when a solid turns to a gas or a liquid turns to gas?

I do not suppose there is some Transfer?

What transfer could that be?

Let us talk about covailent theory, electron transfer?

No lets get into Quamtum , yada yada yada.

You are correct in that there is a change of state but you are glossing over the rest of it.

Think harder grasshopper. Look deeper. Even the smallest is evident when you take notice.

Sorry but even without the mumbo jumbo it is what it is.

Besides I am not conducting class, if I were you would pay me.

The man asked a question and I have a theroy and several observations fo him

Got something better?

I like the wind under the ski that is really right on.
Best one is I TURN EM STRAIGHT DOWN HILLL AND THEY GO REAL FAST!

Stay on with what you will.

It is all here for your pleasure.

Oh and CHEERS!
post #15 of 25
<BLOCKQUOTE>quote:</font><HR>Originally posted by Dr.GO:
As a glider pilot I would call it gound effect. <HR></BLOCKQUOTE>

That is indeed what it is. It is air being squeezed between the wings and the ground.


> The density of the air on a cold surface
> like snow or ice would be greater than
> that of ambient temp.

This is not a very relevant observation. First, the air might be colder than the snow; and second, even if there were a 10 deg F difference, the difference in density would only be approximately (273+10)/273, or 3%.

> This does allow for some airdam effect by
> the ski tip however too much of that would
> be lose of control. (that is why the tip
> of a speed ski is so low)

True


> Remember it is all about electrons.

No it isn't.


> Watch
> the snow as the sun hits it, or a pond on
> a cold morninig as the sun comes up and
> acivates the alge therby heating the water
> surface. The particles which we see
> as "steam" or "smoke" coming from the
> surface escaping into the air are actulay
> electorns being released.

I don't want to offend you, but I also can't let a comment like the above stand. Basically, its so completely inaccurate, it can only be labeled as "scientific gibberish". I don't know where you got these ideas, but if you are interested in these sorts of phenomena, you should only use information from reliable sources on physics.

> This same electron release occures while
> skiing.

Sorry. No it doesn't. There is no significant release of free electrons from either ponds or skis. Under some conditions, the bottom of a ski can pick up a minor amount of static charge, much like when you walk across a rug in winter, but the only effect of this is that the ski bottom has a tendency to pick up dust, and there is slightly extra friction from this.
post #16 of 25
<BLOCKQUOTE>quote:</font><HR>Originally posted by Geoff':
I think that after sufficient speed is reached, the tip of the ski is lifted enough to bend the front of the ski into a more de-cambered position, effectively turning the entire front half of the ski into an extra-large tip. This effect should get approximately half of the ski airborne and add to the ability of the ski to plane. <HR></BLOCKQUOTE>

In principle, this degree of tip-lift could perhaps occur (at high enough speeds), but there are a lot of serioius factors involved working against it. The main one is that if the front of the ski lifts up to any appreciable extent, the air that is being rammed under the ski simply escapes from the side. A second factor is that since skis get substantially stiffer as you go towards the center, this would strongly favor tip lift over the whole front half of a ski lifting up.

<BLOCKQUOTE>quote:</font><HR>Originally posted by Geoff':
You’d be surprised, I bet you were going even faster than you think ... Don’t ya just LOVE that feeling ... Can I be the Gunea pig for this? <HR></BLOCKQUOTE>

1) That's interesting info from your radar gun tests. Not being a racer, I know I don't have the experience to judge speed on skis well. OTOH, on this particular run, the conditions were perfect to just let the skis run, and I probably was going faster than I have ever gone in my previous 30 yrs of skiing.

2) Yeah - I did love the feeling, but I gotta admit it was a bit scary for this old fart. Two things were going through my mind: (a) With the skis this easy to pivot, I better not inadvertently get them angled a bit and catch an edge; and, (b) I *really* need to slow down before the washboard section at the end.

3) No! You can't be the Guinea pig. I'm first in line!

Tom / PM
post #17 of 25
<BLOCKQUOTE>quote:</font><HR>Originally posted by Dr.GO:
The high density of the H2O molucule would be useful IF a ski could be made which would take advantage of that. ... Suppose that along the base of the ski we had several thousand tiny vector openings. Now out of those send Hydrogen gas. ... <HR></BLOCKQUOTE>

The concept you are talking about is called "boundary layer blowing", and could indeed be used to reduce friction. In fact it *IS* used to reduce friction on every air hockey table in the world. However, I think your idea to use hydrogen might meet with a few safety concerns. It kinda takes the name "Hotfeet" to a new level (grin).

Tom / PM
post #18 of 25
<BLOCKQUOTE>quote:</font><HR>Originally posted by slider:
Isn't this called Evaporation(Liquid-Gas) and a change of state from(Solid-Gas)is known as Sublimation? ...Doesn't the release of Electrons change the properties of a substance not it's state? <HR></BLOCKQUOTE>

Right on the mark, Slider!


> ...as the sun comes up and acivates the alge therby heating the water surface.

Pretty much right on target. The main effect of algae (and other particles in water) is that they absorb the sun light and heat up the surrounding water. Pure water is pretty transparent in the visible part of the spectrum, so the same amount of energy from the sun would get absorbed in a much thicker layer of water, and hence, heat it up less.


> I was always under the impression that the
> reason steam or fog from a body of water
> was created by the sun warming it was
> because ...

Pretty close. In a pond with lots of vegatable matter near the surface, the sunlight gets absorbed by this matter much more than is absorbed by the surrounding snow that is covering the adjacent land. The water heats up slightly, and some of it vaporizes (ie, is turned into individual molecules in the gas phase). These molecules rise and hit the cooler air that is above the pond. The temperature is cool enough that the molecules stick together and form tiny droplets of water suspended in the air. This is the mist or fog that you see. End of story. No electrons, no trapped O2 being released, nothing obscure going on.

Tom / PM
post #19 of 25
<BLOCKQUOTE>quote:</font><HR>Originally posted by Dr.GO:
SLIDER, ... Available energy in a biological Vs inert matter. ... OK we have two ponds, one is crystal clear, so not bioloical the second is green with stuff.
...major snip... Hope all your thoughts are happy thoughts about skiing!
<HR></BLOCKQUOTE>

LOL!!! You almost snared me with your troll, but the real "over-the-top" stuff finally clued me in. Good one.

I heartily second your final statement about good skiing thoughts.

Tom / PM
post #20 of 25
<BLOCKQUOTE>quote:</font><HR>Originally posted by Mike B:
Unfortunately that is completely false. ...snip...<HR></BLOCKQUOTE>

Mike -

I finally caught on. Its a troll. He's been laying back chugging a few, pumping out the prose, and having fun with us. WE'VE BEEN HAD!

Tom / PM
post #21 of 25
In other words he's full of it.
post #22 of 25
You Guys are so much FUN!
post #23 of 25
You guys missed his point.
He was talking about electorns, not electrons.
Very different properties.
post #24 of 25
<BLOCKQUOTE>quote:</font><HR>Originally posted by Dr.GO:
You Guys are so much FUN!<HR></BLOCKQUOTE>

Hrumph.

You'll get yours. Just wait and see.

Maybe it will be a troll, maybe a snap posted to Epic of a certain Dr. Go after a yardsale, ... You'll never know. [img]tongue.gif[/img] (but its coming). Watch your back.

Tom / PM
post #25 of 25
(Shrugs)
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: General Skiing Discussion
EpicSki › The Barking Bear Forums › On the Snow (Skiing Forums) › General Skiing Discussion › paging physics man.....4 speed skiing