 Poster: A snowHead
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ski, not on GS!
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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To be fair the racers are often skiing on a frozen surface (they often spray race courses with water to get a hard surface) thus the conditions they race under may bear only slight resembelance to those we as recreational skiers are used to
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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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Wear The Fox Hat, ski, isn't the point that when the ski is flat, the racer is going straight downhill? When the ski is on edge, the ski is turning so most of the time it is resisting gravity.
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So the general view is that for myself, im prob' about right on a 150 then?
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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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Renry, 160 ish.
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Renry,
It really does depend which ski you go for. So decide which ski you want to get, then ask advice on length.
I add this same problem myself when buying some new Rossi Z9s that I didn't get to test. I had to email a very nice lady in the US who had skied them to ask her advice!! Fingers crossed I've gone for the right length... (162).
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i have to respectfully disagree with a few of the opinions here. in years past, weight was an issue with skis. we had to "bend" or de-camber the ski in order to get the tool to perform. as skis gained more shape, tipping the ski on edge accomplishes what we used to have to do in de-cambering the ski. do skis still bend? yes, however, not as much as ten or twenty years ago.
why has this been engineered out of a ski? what does a bow do after it sends the arrow? it straightens. the same energy in a ski can be difficult to manage. when short slalom skis were combined with extreme sidecuts, the stored energy was often difficult to manage. these skis have gotten a little "straighter, a little longer, have almost no camber, and as a result are much easier to manage.
i can think of very few skiers in colorado who are routinely using a ski any taller than their height. in addition i'm puzzled by the idea of a ski "flopping" around. there is something fundamentally wrong with your balance, the mounting point on your ski, or the ski itself if it is behaving in this manner.
i'm 175 cm tall and ski a 170-178 cm ski.
look at nordica's big mountain the hot rod. in it's 74mm waisted ski the longest length offered is 178cm. Fischer's AMC line tops out at 182cm. long skis are vestigial.
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Wear The Fox Hat, (Feel this may be a high jack - but never mind)....On a course earlier this year, talking about GS, I got the impression that to be really quick, the edges are used as little as possible, that is, at the end of the turn, as soon as you can, start to roll the edges off, in preparation for the next turn. 
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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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ski, so what way do you start the turns? - are they mainly skidded, or carved?
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Wear The Fox Hat, Carved !
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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Wear The Fox Hat, A ski running along it's length, whether on the edge or flat, will be faster then a skidded ski. We were talking (on the course), about getting of an edged ski as soon a pos.. 'cos that would be faster, hence my thought that a flat ski is faster than an edged ski. 
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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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ski, i had a lesson through gates once with a v good French instructor. He said that the first thing to do was carve all your turns properly. This would get you down pretty quickly. Then to squeeze out some extra speed, he said that between turns you could try to get the skis running flat, get your weight a little bit back and almost boost the skis forward. I didn't quite get to that level... but I can assure you that the instructor went like an absolute rocket
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| ski wrote: |
| Wear The Fox Hat, A ski running along it's length, whether on the edge or flat, will be faster then a skidded ski. |
Totally agree - that's why I made the comment - you had said about getting ready for the next turn, so, what I think you mean is getting off one set of edges in preparation of going onto the other ones.
See, when a ski is skidding, you are using it flatter than if it was on edge, so, going round a turn, a ski on edge will be faster than a ski on its base.
Now, since you can't directly compare a ski on edge with a ski flat going down the hill, since the ski on edge will want to turn, then it's difficult to compare a straight line speed difference, but we can say that going round turns, a ski which is carving on its edge will be faster than one which is turning on its base.
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You know it makes sense.
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Wear The Fox Hat, Glad that's settled then 
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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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| ski wrote: |
| Wear The Fox Hat, Glad that's settled then |
ah, go on!
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Poster: A snowHead
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Rusty Guy, I'm curious.
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we had to "bend" or de-camber the ski in order to get the tool to perform. as skis gained more shape, tipping the ski on edge accomplishes what we used to have to do in de-cambering the ski. do skis still bend? yes, however, not as much as ten or twenty years ago.
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I thought skis de-cambered/bent more these days because of the massively accentuated side cut?
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short slalom skis were combined with extreme sidecuts, the stored energy was often difficult to manage. these skis have gotten a little "straighter, a little longer, have almost no camber, and as a result are much easier to manage.
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They have? I thought this was exactly the desired effect? AFAIK, slalom skis have gone monotonically from skinny 203s to hugely waisted 165cm (for men)?
Re turning being faster than straight...IIRC, old style skis on edge in a straight line were slower as the friction of an edge going through the snow was greater than a ski sliding on top. Also there would almost inevitably be a degree of sideways skid further slowing one down. These days, carvers in the right hands (on the right feet) and the different shape of race courses (?) mean is this less important?
Also, I understood that the point of wax was to increase the particular friction co-efficients as to maximise the effect of the thin layer of fluid between ski and snow and aren't you then in an entirely different world to the area x pressure x coeffient of friction than sand blocks are in in high school physics?
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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, I don't see to many top-speed skiing competitors using 150cm skis. All other things being equal longer is better for all-out high speed. All other things being equal though means that we don't compare a 190 B1 to a 170 SX11. A ski that will flop around when going over bumps at high speeds on hard snow (tips are bouncing like pancakes) won't be bothered at all on a couple of feet of fresh snow, if you find a steep and long enough pitch to get going that fast too.
Regardless of the above, advances have been made and skis are much more stable at a given length and weight than would have been possible years ago. You can get away with a lot shorter ski today.
With the exception of a few speed freaks, I can think of only two reasons for a longer length. One is the affect on turn radius it may have. If you want to make a clean carve at a long radius on hard snow the sidecut will limit how long a radius you can cleanly carve. The other is that the length of the ski and the fact that you only have two of them limits the amount of snow/ice you can push against in a carved turn. If you want to use bigger forces, you need more ski.
A shaped ski is decambered easily when put on edge. Try and get the whole edge on the carpet with the ski at an angle. You will see it is decambered into a nice arc by pressing down on the centre. Decambering a straight ski is a little more complicated.
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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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So, just why are longer skis faster? I always thought it was because of increased stability.
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You need to Login to know who's really who.
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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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slikedges, a very good question! I ain't qualified to answer it - I'm no physicist - but it would be very interesting to know the definitive answer. One gets the impression that, over the centuries, optimum ski length for speed has been arrived at more by trial and error than science.
The 240cm speed ski may, or may not, be the optimum length but it is actually a lot shorter than the 3, 4, or even 6 metre skis that were trialled in places like the Californian Sierra to achieve maximum speeds (as long ago as the mid-19th century).
Lengthening the wheelbase of a non-motorised platform like a skateboard also optimises speed. I guess the physicist would answer that a longer platform generates less vibration (heat? friction?), enabling the device to slide/ride faster, but let's get the authoritative answer!
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PG, the slovenian/croatian thing is interesting. It really demonstrates what we all know intuitively and makes sense I suppose because as skiers get bigger it is only a square of their linear increase in their size that gives them greater drag, but a cube of that linear increase in size that gives them more mass to drive against that drag.
I haven't had time to read the other thread yet! but am looking forward to it. Thanks!
David Goldsmith, the length thing is an issue to me as I've just bought a pair of 155cm skis! I can feel a third pair to the quiver coming on.
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I would imagine that snow behaves sufficiently like a fluid for boat design rules to work, probably those for a hull on the plane are the closest , digging up my copy of Skene's Elements of Yacht Design it actually says that a powerboat on the plane performs just like a water ski, a mathematical definition of planning is very simple
Speed / (square root of ski length in feet) = 2
Thus we can say that a 1.5M long or 5foot ski will plane at about 4.5mph at slower speeds the ski will be displacing snow and be harder to turn etc.
Now with boats there are 3 ways to increase speed, apply more power, lighten the boat or increase the length of the hull, obviously with skis power is effectively going to depend on the angle of the slope you are travelling down the steeper the slope the faster you travel, the weight will depend on the weight of the skier but so will the power, as a heavier skier has a greater potential energy at the top of the slope than a lighter one so the only easily changed variable is the length of the ski, this is where it gets complicated as we start using hydrodynamics formulae
The easiest to use would be Kieths formulae but it needs to be modified a little
Essentialy we get a fomulae as folows : Speed = (square root of Length) x C x (Cube root of ((Power x 1000)/Weight)) Where C is a Constant value for skis probably something between 1.3 and 1.5
Weight is measured in pounds and length in Feet, power should be in HP so this would need to be calculated for each slope however since esentilaly for the same slope and skier the second part of the equation does not vary we can simplify the formulae as follows
Speed is proportional to the square root of the length of the ski (given the same skier and slope)
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And the winner of this years Dull Thread award is....................
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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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| Frosty the Snowman wrote: |
| And the winner of this years Dull Thread award is.................... |
My oh My, I don't think this one wins by a long shot, Snowman. This is important to our Sport.
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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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Long skis truck. Short skis suck.
Long threads truck. Short threads suck.
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Wear The Fox Hat,
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Are you saying mine is irrelevant?
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No. Is there some other language I should post in that you would understand better?.
This thread started quite well with a nice chat about the correct lenght of ski for different people. I agree this is very important and relevant to all, but has gone downhill at gradually increasing speed due to the increasing length of waffle. Put the Craotian/Slovenian study in front of 100 skiers plucked from the mountain , give them a nice mug of Horlicks, and I will bet that over 90 will be a in the land of nod within ten minutes. Perhaps in that case it is dull.
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You know it makes sense.
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David Goldsmith, What about girls?
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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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I don't know. My wife is 5'1".
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Poster: A snowHead
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Frosty the Snowman, I have that Croatian link in my favourites for when I'm having trouble nodding off for my afternoon nap. If the English version doesn't have the desired effect, try reading it in Croatian.
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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PG, I have to confess that i didnt read it all. I do however have a very strange imprint on my head after it slammed into my keyboard after reaching halfway down the first page.
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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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PG, Frosty the Snowman, guys, it really doesn't take a lot of reading, a few seconds skimmed tells you all it has to say - it just looks a bit compuh-likated. If it took any time, I couldn't have found the time to read it at work. Still haven't read the other thread for instance - too many words.
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You need to Login to know who's really who.
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slikedges, sum ov uz arent az briyt as yew
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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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Frosty the Snowman, briytness not required for this stuff but never anything wrong with more light
D G Orf, are you saying a long ski sinks in less and so produces less friction?
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slikedges, not exactly, it's helpful if you think of snow as a more boyant form of water and skis as a form of boat, at low speeds you push through the snow but at slightly higher speeds (roughly walking pace) you will glide over the top without sinking. Doing this allows you to use hydrodynamic formulae as a guide, it's not just friction although that does play a part it's not a big one
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D G Orf, errr, so why is a longer ski faster? Even if it is because it is gliding over the top, it still means less friction, doesn't it
PG, I just read that thread. The only bit I understood was where laundryman (where is he these days?) said what I was saying above about cubes and squares. 
Seriously, assuming standardised environmental conditions straight down the hill on a frictionless surface but with friction from drag (identical to free-fall), mass and frontal area presented seem the only important variables. I suspect that on an icy surface, the other variables still aren't very important, except perhaps for more stable (?longer, stiffer, straighter) skis. On a softer surface, obviously friction from snow contact on the bases, as well as pushing through soft uneven bits becomes more important. At low speeds and on shallow slopes, there is little drag and the main resistance is from the snow. Increased mass provides momentum/inertia to overcome/reduce friction and drive through the snow, so is a great advantage. At high speeds and steep slopes, drag becomes more important and friction less so. The helpful effect of a smaller frontal area creates less drag and relatively reduces the speed benefit of increased mass. I think.
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slikedges, hmm lets see, as the ski gets longer the distribution of weight is better so ground pressure is less (so friction plays its part here) however if you were to make a ski of the same area but wider rather than longer you don't get to go as fast, this is where the frontal area of the ski becomes important, however in all seriousnes there's not a huge difference between a 1.76 and a 1.8 m long ski, as an example to go just 50% faster than you could on a 4ft (1.2M) ski you'd need to be on 9ft (3.6M) skis. David Goldsmith, asked what the answer was so I posted the formulae but in reality as anyone can see whilst longer skis are potentially faster it won't be by much
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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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D G Orf, looks like I'll have to put on more weight. Any more room on your funbus?
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slikedges, not my bus I just begged a place 
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FAQ
, has no relavance to the one i do though. 