 Poster: A snowHead
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Listen, I said back to skiing. Anymore of this and I'll split it off to a new thread 
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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the ice perv, the film was made whilst the details of the bomb were still classified as secret. It even got the design wrong (I'm led to believe).
[EDIT] Sorry I hadn't seen Pete's last message when I posted.
Last edited by Obviously A snowHead isn't a real person on Wed 13-04-05 13:54; edited 1 time in total
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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| D G Orf wrote: |
| however if we are looking at the unassisted requirement (i.e you can walk up a mountain but you need assistance to fly) |
I've not seen anyone do the flying K without skis but I doubt they would be that fast.
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You need to Login to know who's really who.
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It must be the weather - or that end of season feeling
skanky, Ignorance is no excuse. Taking no notice of a Mod's instructions is a crime punishable by documenting the verifiable references for any external sources relating to information you've provided in your posts over the past month. Repeat offences are punishable by a trip down the flying K piste blindfold.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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PG, source linked in an edit.
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You'll need to Register first of course.
You'll need to Register first of course.
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davidof, ok powered assistance then! Likewise you can freefall without a parachute but the results might be a little unplesant
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Ok, so why is it that a golf ball, hit with backspin, quite often doesn't 'bite' until the 2nd bounce.
Alway wondered that, so which of you cleverclogs has an answer.........
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Slowplough, going back to my days as a caddy 7/6 for a half set and Ten Bob a round for a full'un, it seemed to depend on the friction conditions of the landing area and the height of the drop. Probably has a lot to do with the quality of the golfer.
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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Masque, you were cheap
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Russell, It were a bloody long time ago 
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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A typical recreational skydiver will freefall in a flat, stable, face to earth attitude at about 120mph, transitioning to a standing up position will get you up around the 140 mark and head down in a nice streamline would get you up around the 160 area. To go faster you need more height to start with, a very good technique and a decent set of gear (helmet, fast suit etc).
Jo Kittenger holds the absolute record but of course he didn't just go up and jump from a plane. He did go just over the 700mph mark on his epic jump though, breaking the speed of sound as well.
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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Strictly speaking, I don't see how you could possibly go faster during speed skiing than in free-fall, all other factors being equal. You're speed at the end can be seen as a direct result of your change in gravitational potential energy, but since there is more friction during skiing than in free fall, you will be slowed down more along the way, and hence end up slower at the end. The only way I could see the speed-skiier going faster is if the free-faller was extremely un-aerodynamic, but if the person falling got as aerodynamic as the speed skier, there is no way the speed skier could reach or surpass the free faller's speed.
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Frosty the Snowman,Pete Horn, in which case the bomb must have been spinning in the direction of travel and not backwards? I'd hate to sit on an airplane that landed with backward spinning wheels!
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You know it makes sense.
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Anyone fancy talking about speed skiing?
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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Not really qualified to Pete ....... but I have enjoyed most of the diversion.
On topic, from your original post, it seems like Les Arcs really needs to think about better access to the KL and maybe more netting around the rocks/cliffs area. After all it was not the KL which killed poor Marco. Anyone familiar with the area able to comment on the practicality of easier / safer access and improved hazard protection ???
Here's an article about the NZ speed skiing team at Verbier - couple of days old I'm afraid, we got diverted.
http://www.snow.co.nz/media/media_index.asp?pressReleaseKey=1784
Last edited by Otherwise you'll just go on seeing the one name: on Thu 14-04-05 8:33; edited 1 time in total
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Poster: A snowHead
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Subject to gendarmerie findings, those that have voiced an opinion on the French speed skiing forum don't seem to want to attribute any blame. Two or three people made the point that it was just bad luck, and that netting wasn't really the answer.
[edit] - forgot to reference the speed skiing forum link
http://www.kl-france.com/
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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One answer on that forum to a technical question I added, querying the Swiss skier's "air cushion" (previous link reference)
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Dear Peter,
It is a myth that a "cushion of air" forms under the skis. At high speed, any small "bump" may cause the skier to deflect upwards. Typically, at high speed, the skier is "skimming" over the snow surface so there is reduced ski-snow contact...but this is not due to a cushion of air trapped under the ski.
The technique for speed skiing is much more complex than people peceive it to be. It is a combination of staying in your most aerodynamic "tuck" whilst "trimming" your skis to gain speed and maintain control; flat skis are faster but more difficult to control while coming up onto your inside edges increases control but reduces speed.
Everyone has their own way to balancing the various aspects to maximize their speed and certain tracks suit different people.
Skiing ability is very important especially when things go a little wrong...skiing ability might keep you upright when a fall seems inevitable!
You know you can try it yourself very easily!?
Nigel |
(At least I could wriggle out of his last suggestion without too much trouble!  )
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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Quite a few years ago and I have forgotten where, but I think it was near Morzine/Avoriaz Les Gets.Or maybe Verbier! We watched speed skiers practicing their starts by being 'Launched' with the aid of an 'elastic band'held between 2 Pisten Bully, It was quite spectacular to say the least 
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You need to Login to know who's really who.
You need to Login to know who's really who.
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OT (sorry) a thousand thanks for phpbb - that speed skiing forum is clanky in the extreme. 
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Going back to the 'air cushion' thing, perhaps it's a matter of semantics, yet again. The above poster seems to agree with DG - but then again Masque's earlier post on the processes at work contradict this to an extent.
http://snowheads.com/ski-forum/viewtopic.php?p=117571#117571
Someone at the Club des Sports told me that a majority of records were broken end of season, in the warmer conditions. If that's correct, that might suggest that the process at work under Masque's description potentially generates greater speeds in speed skiing events than on the 'corrugated' hard snow/ice scenario suggested by DG. The surface in warmer conditions may well be smoother as the Swiss speed skier suggested in his article, with a minute air cushion created by using the appropriate warm weather high fluor wax.
Not sure how that would work... less friction in hot weather with the high fluor reaction on snow with a high water content than when using cold weather wax for rock hard icy snow at temperatures well under zero?
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You'll need to Register first of course.
You'll need to Register first of course.
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Although my observation was that the snow was corrugated for speed (either with a winched piste machine, or by racers side-stepping the track (the traditional way)) they would certainly wait for softer snow - not run races on ice or hardpack.
Some experimentation was done by a British engineer back in the 1980s who produced a method of feeding liquid lubricant through holes in the ski from a reservoir mounted on the top of the ski. I think the FIS banned it!
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| PG wrote: |
| Not sure how that would work... less friction in hot weather with the high fluor reaction on snow with a high water content than when using cold weather wax for rock hard icy snow at temperatures well under zero? |
I always believed that the slippery nature of snow is due to melting under pressure. Considering the speed and the angle of the slope, the pressure of the ski might not be sufficient to melt the surface, unless hot weather helped.
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Frosty, but it was spinning the "wrong" way, at least it was in the film. I always thought it was spinning to make it bounce.
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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marc gledhill, Your are probably right. I could always concenrate on the film but only until Guy Gibson shouts for his dog. etting back to the tragic death, am i correct in thinking that anyone could die if they fell on this particular black run  , or were there special circumstances involved. Had the poor fellow died during the race it would have seemed strangley less tragic.
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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Frosty the Snowman,
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am i correct in thinking that anyone could die if they fell on this particular black run
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A pertinent question , and one that will worry Mrs W when I get to return. I've done that run a number of times, and on the first ever attempt, a good few metres "a derriere". It is steep, and a fall (bless those darling icy moguls) does result in a fair old slide, even with the bumps to hang on to.
But never, never have I felt in danger of going over an edge. There are drops, for sure, but if memory serves, there are two black pistes coming off the top, and any rocky outcrops tend to be in the off-piste between the two marked areas, and on the flatter sections nearer the bottom (all skiable terrain btw).
They are also a long way to the SouthWest of the KL (well, up the valley anyway). So if Marco (God rest his soul) made it that distance because of the suit being of no use to slow him down, then it was a very, very long way indeed.
Any thoughts PG?
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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Yes, a long way indeed. During one of the first few times I took that run, towards the bottom as you say, I was in that "no man's area", and found myself at the top of a drop - gave me quite a scare. But unless conditions are extremely icy (I wouldn't go down that black if they were) I don't think it is particularly difficult or dangerous.
The speed racer who witnessed the fall, described his amazement when he realised that the object he saw bouncing high over the moguls, which he first assumed was some sort of large transport bag, was actually a person.
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The "World Champs" have been delayed by a week, so should now be taking place during the EOSB, if conditions allow..... following press release from Les Arcs:
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"In reason of bad weather conditions and forecasts, the Mondial race in les Arcs schedule is modified :
Sunday April 24th : registration
Monday april 25th / Wednesday april 27th : race
April 28/29th : weather days
April 23/27th : track open for training"
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You know it makes sense.
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| David Goldsmith wrote: |
| Although my observation was that the snow was corrugated for speed (either with a winched piste machine, or by racers side-stepping the track (the traditional way)) they would certainly wait for softer snow - not run races on ice or hardpack. |
A winched piste basher will leave corduroy style gentle corrugations running parallel to the slope but side stepping would give cross-slope ridges. I'm confused. I thought that for these speed skiing events the idea now is to have the slope as flat as possible since hitting any sort of mini-undulation at speed can cause falls. So what is correct - do they now compete on a really hard and flat surface or on a softer and lightly ridged run?
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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kuwait_ian, well if next week's event isn't cancelled, I reckon the best way to find out is to go and take a look! I hope to meet up with a couple of racers there, from the States and Scotland, so watch this space for the interview...
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Poster: A snowHead
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ian, I think you'll find that the world records are generally set (obviously, talking northern hemisphere, though the Roca Jack slope at Portillo used to be used quite a bit) in March or April when the sun has generated a bit of humidity and lubrication to the surface.
As for the grooming or side-stepping, this is primarily to take out any lumps, bumps, ruts or tramlines because it's so easy for the skis to be deflected. Whether the corrugations run parallel or tangental to the fall-line is probably unimportant - a winched groomer would be preferred because it would be better at reducing undulations than a side-stepped one. However, as I say, smoothed snow or hardpack/ice would be avoided in my experience - otherwise they'd hold KL events in Jan/Feb.
Also, of course, you need extremely calm and clear weather conditions for this event. It demands long hours or full days to get through it.
Last edited by Poster: A snowHead on Sat 16-04-05 11:28; edited 1 time in total
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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OK guys - I await an on-the-spot report and thanks for pointing out the calm weather requirement. Hadn't thought of that one. It seems that having a bit of humidity is the key to all this, as Masque said on page 1, altho' some of the water then breaks down into a gas when it cavitates. Would it actually be steam or could it be a low temperature vapour ????
If most of the racers ski in the same set of 'tramlines' made in practice or by the first few down, the grooming is probably unimportant.
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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...
Last edited by Well, the person's real but it's just a made up name, see? on Sat 15-06-24 11:11; edited 1 time in total
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You need to Login to know who's really who.
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You've made a wrong assumption that the skier and skydiver will have the same vertical velocity component, they won't. The skiers weight will still be pressing against the snow (or air cushion) and this will have a vertical component which will act against gravity.
In your scenario a constant vertical acceleration will give higher horizontal speeds on shallower slopes. We all know this doesn't happen, regardless of friction.
In your argument above you mention the skier will be experiencing a horizontal acceleration. Where does the energy for this acceleration come from? - It must come from reduced vertical acceleration.
Using conservation of energy arguments, and assuming no friction: The vertical force on a 100KG skier/skydiver due to gravity is 980N (assuming g=9.8). The potential energy lost through a 100m vertical drop will be 98,000 joules. If this has all been converted to kinetic energy then the speed will be the square root of ( 2 x energy divided by mass) (from e=½mv²), this gives about 44.272m per second for both, the average speed being about 22.136m per second.
In the skydivers case this will be vertical only and distance travelled will be 100m, the skydiver will have taken about 4.52 seconds to do this. Assuming a 45° slope the skier will have travelled about 141.42m
(root 2 times 100) and taken about 6.39 seconds.
Do some reverse sums and you'll see that the skiers acceleration has been about 6.93m per second per second down the slope. Vertical acceleration about 4.9 m per second per second, - ½g.
Now lets introduce friction. Assume both skydiver and skier have the same friction at the same speeds, and say the average of the frictional force over the descent is 100N. The energy taken away from the skydiver will be 10,000 joules (force x distance) while the skier on a 45° slope will have lost 14,142 joules. Skydiver's kinetic energy now equals 88,000J and the skiers 83,858J. This gives speeds of 41.95m per second for the skydiver and 40.95m per second for the skier. The skier is slower over the same vertical fall.
One could argue that you could have slopes/falls long enough for both to reach terminal velocity. Fair enough, then the only difference between their terminal velocities would be due to differences in friction. I would say that the skiers skis pressing against snow (or a very small air cushion) would have more friction than a similarly attired skydiver with skis pressing against nothing. Of course a skydiver doesn't need skis and could therefore make them self more streamlined.
Hope this doesn't sound too pedantic or nit picking, besides, I've enjoyed doing the sums.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Pete Horn, of course the sky diver does normally require a parachute which even when packed probably gives at least a little drag
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You'll need to Register first of course.
You'll need to Register first of course.
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About time too
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Pete Horn, Happy millenium, Peter
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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The force due to gravity experienced by skier and skydiver is identical, providing they are of the same mass. The skydiver only experiences friction due to air resistance which is a factor of his projected surface area. The skier experiences contact friction with the ice, which is constant and air resistance based on projected area. Providing the slope is long enough, the skier will reach the same speed regardless of the slope angle. His absolute acceleration will just be lower for a lower gradient. Therefore, apparently the only way a skier can reach a higher speed than the skydiver (providing they both reach terminal velocity) is by a having a far smaller projected area to overcome the extra contact friction with the snow. However, a skydiver has a very bluff profile whereas the skier will be crouched and be wearing aerodynamic headgear. The skydiver will therefore generate more wake than the skier and so his friction coefficient will be higher for a given projected area. If my memory serves me correctly, the friction coefficient of a completely bluff body can be reduced by 30% by reshaping to an egg shape. I think it's therefore possible for a well tucked skier to have a higher terminal speed than a flailing skydiver...  I'll have to dust off my notes and check that lot.
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MartinH wrote (a while back)
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Helmets don't necessarily protect from spinal injuries.
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they don't always do well on head injuries either. At the opposite end of the ski-danger continuum from speed ski-ing, my brother in law, luckily wearing my helmet, fell a few feet backwards off his second ever nursery slope draglift, having left it too late to let go at the top. Five hours later, when he was still vomiting, and couldn't remember the circumstances surrounding the accident, I took him to the local doctor who diagnosed concussion but said we must watch him like a hawk and ring for an ambulance to take him to Albertville for a brain scan, if his condition deteriorated. No doubt speed skiers wear much higher tech helmets, but as this terrible accident shows, bodies are frail. It was a good 48 hours before we relaxed our vigilance. The Italian racer's suit was obviously designed for minimum friction, but it's easy to slide quite a way even in ordinary ski wear, on an ordinary slope. What kind of clothing maximises friction to reduce this danger? A lot of the stuff in the shops looks pretty shiny.
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FAQ
