 Poster: A snowHead
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| Sharkymark wrote: |
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. |
Laundryman wrote in another thread on a similar theme (Scientific help needed!):
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What I hadn't taken into account was that (just as for the gravitational force, as I pointed out earlier) the fact that the frictional force is proportional to mass is cancelled out by the fact that acceleration is inversely proportionally to mass. The only force acting on the skier that is not proportional to mass is the air resistance, and the relative deceleration that this will cause will be greater for the lighter skier. His terminal velocity (when the downhill and uphill forces balance) will be less.
This applies to skiers of different masses but presenting the same cross-sectional area to the airflow. The effect will normally be diminished because the heavier skier will normally have a bigger cross-section. However his mass will tend to vary with the cube of his height, whereas his cross-sectional area will vary only with the square. Therefore the heavier skier's advantage will not be entirely overcome |
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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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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| Sharkymark wrote: |
| I think it's therefore possible for a well tucked skier to have a higher terminal speed than a flailing skydiver... |
That maybe so, but I thought we were talking like for like and comparing a speed skier with speed skydiver who presumably can tuck up into that egg shape rather than 'flail'. Though as D G Orf points out any sensible skydiver will also be encumbered with a parachute.
My money is still on a well tucked skydiver having a higher terminal velocity than a well tucked skier.
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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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It could be possible but I agree that 99.99% of the time the skydiver wins...
I clearly miss snow too much
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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, you're correct if the skydiver adopts the traditional skydiving position, however if he adopts a head-down position then he will present a far smaller frontal area to the air than even a skier in a tuck position. I would imagine then, that a skydiver would have the advantage. 
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You'll need to Register first of course.
You'll need to Register first of course.
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What we need is an experiment! Any skydivers amongst the snowHeads or speed skiers for that matter...
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| Ian Hopkinson wrote: |
| What we need is an experiment! Any skydivers amongst the snowHeads or speed skiers for that matter... |
Me waves.
I did the odd jump or 48 whilst a uni student 10 years ago, haven't done any since though.
http://jameshart.mine.nu/others/skydive/skydive.wmv was me on a cloudy day.
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Will you volunteer for the sans parachute test?
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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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Will you promise to catch me if I say yes?
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Bit OT but at least about speed skiing. More on the Kiwis at Verbier from snow co
A personal best for one and a very creditable 5th place for the other. Keep an eye out for them at Les Arcs during EOSB Week.
FenlandSkier, nice little video clip - no way could I ever do that.
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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As with FenlandSkier, I've not made any jumps for the last 10 years or so (crap British weather and over-crowded airspace caused me to give up after about 80 jump), so will respectfully decline Pete Horn's kind invitation. I do have my 'chute still, but am now probably too heavy to use it 
If anyone's looking hard at the kit in his vid and thinking about the drag issue, FenlandSkier was using fairly old-fashioned kit with a belly-mounted reserve. (I assume it was a fairly early jump of his - nice attitude on exit, I always had a problem with going over backwards so much preferred going out head first). Most jumps are now made with (aerofoil-shaped) back mounted mains and reserves, which are much less bulky when packed and I doubt cause a lot of drag. As stated above, the general rule of thumb I was given when starting was that a standard belly first attitude gave a terminal velocity of about 120mph, and if you put your arms back and go head down (either to go straight down or shaping yourself into a wing shape and going into a track, with some horizontal component) you could get up to about 180mph - very exhilarating I assure you. As most skydiving (after initial training) involves formation work, matching fall velocity is pretty crucial. You can speed up/slow down a bit by increasing/decreasing the amount you arch your back, but lighter/smaller/beanpole jumpers do fall slower and often wear weightbelts, while the more solidly built of us would tend to wear more voluminous/flappy jumpsuits.
Anyone else see the vid of a skydiver in a wing-suit racing skiers down a (I assume pretty steep) piste? Can't remember who made it, but I saw it in the sports bar in Chamonix last year. He was about 200ft off the surface of the piste (and got closer on occasions). Staggering! 
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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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| Quote: |
Not a good season so far, for fans of the "White Fear" in Les Arcs. Heavy snow led to the cancellation of the annual event, the Red Rock Cup last weekend. Just one more big event this season in the resort, the World Championships, taking place between April 18th and 23rd - but conditions are not ideal.
Far worse - at the end of last month some of the club kids were in the Varet gondolas on their way up to the Aiguille Rouge when they saw one of the KL racers, in full gear, take a horrific tumble. Not on the course itself, but making his way across the top of the Lanches black to the intermediate start point. Carrying his 2m40 speed skis on his shoulder, he lost his grip as he hit a rock and the bindings on his short skis ejected. It was an extremely warm day, and he was only wearing his aerodynamic speed ski gear - a very slippery, plastic-coated, skin-tight catsuit. With little that could act as a brake on the snow, he continued to accelerate as he bounced through the mogul field. Not the steepest of blacks, but once you start falling, it's very hard to stop. He eventually slid off the side of the piste - then it's a long, rocky way down.
The Italian racer, Marco Salvaggio, died of his injuries - severe brain trauma. The event - the French Championships - was cancelled immediately. The gendarmerie is investigating - concerns have been voiced about access to the intermediate start, via the difficult Lanches black, before.
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There was some argument about this in the Mont Fort cable car last week between a couple of speed skiers on the way to the Verbier speed ski event down from Mont Fort- which is also accessed via a black mogul run - over the lack of suitable attire. Apparently, they are supposed to wear suitable clothing over their plastic suits before they reach the starting point to stop them sliding in the event of a fall. That's all well in theory, but a skier broke his neck a few weeks back after tumbling the entire length of that black mogul run and that was without a plastic suit or 2.40m skis on the shoulder.
BTW- The fastest times I observed last week were in the order of 170 km/h. There was even a one-legged participant
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And here he is, having gone beyond 200 kph at Les Arcs for the first time. Amazing.
http://www.itv.com/news/world_982227.html
We were watching the finals on Saturday, great fun, and I'v a few photos (will post them later) of the post race ambiance. Real camaraderie amongst a group of people dedicated to their sport, from all over the world.
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You know it makes sense.
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Astonishing - but if so much of it is down to wind resistance he does offer less windage by virtue of his 'handicap'. What a guy.
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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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Wow!!. I annot comprehand the achievment and brvery of this guy. Total respect. It looks like he just has one ski and ordinary poles
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Poster: A snowHead
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He was there but didn't take part on Saturday - which is a shame, as people reached higher speeds, starting much further up the run. They've got some strange rules in this event - apparently if you beat a world record during the event (over several days) you can't break it again. If you do a run, and beat your previous record, it's just an "unofficial world best". _thumb.jpg)
That happened to the women's world record holder, on production skis (normal catsuit).
Having got a world record on Thursday (188 kph) she did a run from the top yesterday, reaching 191 kph - but it doesn't count.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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I have to say she looks built for comfort - not for speed 
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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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You need to Login to know who's really who.
You need to Login to know who's really who.
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I'm sure a British speed skier joined snowHeads some time ago...
Xavier's monoski looks a bit blunt at the front - is that normal?
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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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More on disabled speed skier, Australian Michael Milton, here:
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"To crack 200km/h has been a dream of mine for a while now. I've talked about it a lot and haven't been able to get there.
"This year, after delaying flights and waiting extra weeks for things to happen, there's been times I've been almost giving up on the hope of getting the opportunity to do it."
"Yesterday the conditions were so good. It was an absolute superhighway out on the track, so to be able to run on such a track in perfect weather was really helpful." |
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"I know a lot of amputee skiers and I try to talk them into it, but at the moment I'm out here competing against my own previous best and competing against the hill and the wind.
"I can't find anyone crazy enough to come out and do it with me." |
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You'll need to Register first of course.
You'll need to Register first of course.
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Now i bet that is a big thigh
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Another piece here: http://foxsports.news.com.au/story/0,8659,15156414-23218,00.html
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| Milton was striving for the 200km/h mark on March 20 when racing was brought to a standstill when Italian speed skier Marco Salvaggio crashed on his way to the top of the course and slid for 1000m over rocks and bumps. He was pronounced dead on arrival in hospital. "It really upset everyone and at that stage I didn't feel like chasing the record," Milton said. |
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"Try balancing on one leg for a few minutes: then consider how much strength you need to ski at 210km/h in a tuck position on that one leg?"
Australia's current fastest alpine skier, AJ Bear, grew up with Milton on the slopes of Thredbo and Perisher Blue.
"He was always fiercely independent. He might only have had one leg but he'd never let you carry his skis: somehow he'd do it with them tucked under his chin," said Bear.
"The course is set up differently for speed skiing, but I've topped out at 150km/h in a World Cup race and that's incredibly fast even on two skis, 210km/h is mind boggling." |
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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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this thread has been on-topic for too long. Another man in search of speed can be found here: http://www.fredrompelberg.com/en/html/default.asp - click on "Fred Rompelberg" at the top and then on "records" to see his (still current) world bicycle speed record (with slipstreaming) - 268.8kph!!!. Set in 1995 and to be challenged next year by Jeroen Blijlevens.
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Tony Lane, Where the hell do you get V+ rated bicycle tyres
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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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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An update, with confirmation of the calendar for the coming season, one-legged skier Michael Milton's goal of beating the Australian able-bodied record this year, some scary video of a big crash of a New Zealander at Les Arcs last year, plus advice and info about this sport from a former American world record holder, the first man to break the 150mph barrier ...
Read the article
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