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Shaped vs Straight

post #1 of 16
Thread Starter 
Does any one know where i cn find information about shaped skis and straight ski? I am doing a science fair project about the differences between the two types of skis, so i need some iformation about both of them.
post #2 of 16
Way to go!!!
post #3 of 16
What school in Boston do you attend?
post #4 of 16
Thread Starter 
one on the south shore. Hanover
post #5 of 16
Do a search on this forum for ski shape terms such as:
running length
cord length

Also search the web for anything regarding shaped skis and any terms you read on this board.

If you have access to LexisNexus you will probably be able to pull up some magazine articles.
post #6 of 16
Wow! Are kids getting lazy or what? It is too much effort to Google then cut and paste, now you want us to writh the damn thing for you too.
post #7 of 16
Where did he say he wanted us to write it for him? He asked a skiing related website for some information - probably a good place to ask some questions. No need to be a jerk.
post #8 of 16
Skis have always been "shaped", just now they are more dramatic. There is no longer two schools.."shaped" and "straight", they are now just "skis"
post #9 of 16
Welcome Supra282. Theres a lot of info on shaped vs straight skis here on Epic, but unfortunately its spread out all over the place so let me try to start you off. As compared to traditional straight skis, shaped skis

-- have a deeper sidecut. Take the average of the tip and tail width and subtract the waist width from that number and then divide by 2. The final number tells you how much the side of the ski curves in at the middle if you look at it from the top. You might want to do this for any ski you can get your hands on – both new and old – and then make a table of the results that you can put on your poster.

-- have a smaller sidecut radius. If you take a ski, lay it on a large piece of paper on the ground and use a pencil to trace out the shape of one of the edges on the paper youll get an arc that looks like a small part of a very large circle. The radius of that circle is the sidecut radius. The sidecut radius doesnt tell you anything more than knowing the sidecut and length but its in a more convenient form. For old straight skis, thisnumber used to be anywhere from 35 meters to more than 70 meters. Modern skis run from about 12 meters to 20 meters sidecut radius. If you are good you can usually carve a turn from about one third the sidecut radius up to about 90% of the sidecut radius but out of that range you have to skid the ski a bit. So putting these numbers together means that the shortest turn you used to be able to carve on old skis was around 10 meters in radius or about 60 feet in diameter but for the new skis the shortest turn you can carve is about 4 meters in radius or 24 feet in diameter. Normal people that are skiing just for fun will pick up too much speed if they try carve a 60 foot diameter turn. Now the same people can have the fun of carving without picking up too much speed because they can carve tighter turns on the modern gear.

-- are stiffer torsionally. Take a ski and hold it near its tail with one hand and near its tip with the other hand and try to twist the ski. Modern skis are stiffer this way –torsionally– than old skis. They have to be in order to work properly. If they werent, because they have wide tips and tails, these parts of the skis would tend to lay flatter to the ground as you go around a turn and have the middle of the ski up on edge. This would stop the tip and tail from getting a grip on the snow and you wouldnt turn as well. Old skis didnt need as much torsional stiffness.

-- are shorter. You could make a long shaped ski –and they did for a while-, but it doesnt gain you much because the shorter shaped skis work 99% as well in carved turns and much much better when you are forced to twist the skis around in bumps. Also if you make the ski long and want to keep the same sidecut radius the tip and tail get too wide for comfort.

-- are softer. Take a ski and put its tail on the floor to one side of you. Hold its tip in your opposite hand and press down on the middle of the ski with your other hand. You are feeling the stiffness of the ski. You can smear butter on toast better with a stiff knife not a thin plastic card and the same thing was true for skis. Skidding worked better on stiff skis. Almost all of the turns on old skis by regular folks were skidded so old skis usually were very stiff. Carving a turn only works if the middle of the ski can flex down into the snow a bit so the modern skis meant for carving are made somewhat softer than the old skis meant for skidding.

-- are more fun. Why? Because you can easily carve on them when you want, easily twist them around when you need to –in bumps- , and even skid them fairly well. Whats the big deal about carving? Well there are lots of messages on this forum about this but one good one that I found is thsi one - http://forums.epicski.com/showthread.php?t=8002

-- shaped skis turned out to be so much better for most things taht hardly anyone even calls them that anymore – they just say -skis- not -shaped skis-. About the only time you don’t want so much shape is in deep cut up snow that hasnt been groomed. Skis with too much shape tend to be too turny in that sort of snow and can be jumping all over the place on you.

Have fun at your science fair. I’m figuring you and your family ski, so be sure to show a picture or two of you and your family skiing as well as all the science stuff. If want any more info let us know and be sure to come back and tell us how it went.

Good luck!

post #10 of 16
Thread Starter 
Originally Posted by kiwiski
Wow! Are kids getting lazy or what? It is too much effort to Google then cut and paste, now you want us to writh the damn thing for you too.
Have u tried to find information anbout the physics of straight skis. All that is out there is shaped skis.
PS where does it say anuthing a bout writing the paper Jerk

Thanks for all of the info YOT
post #11 of 16
Originally Posted by Supra282
Have u tried to find information anbout the physics of straight skis. All that is out there is shaped skis.
Lindh, Sanders: The Physics of Skiing, 1996, ISBN 1-56396-319-1
Some straight vs. shaped comparisons, a lot of references to pre-1996 literature.
post #12 of 16
post #13 of 16
I did my project on wood vs metal vs fiberglass, a big topic in 1968. I studied all the structural proprties, explained torsional rigidity, dampening etc. In the end the judges asked "wouldn't some form of plastic be more slippery?"

Don't assume the judges know anything about skiing. Have fun.
post #14 of 16
Originally Posted by Supra282
Have u tried to find information anbout the physics of straight skis. All that is out there is shaped skis.
PS where does it say anuthing a bout writing the paper Jerk
You said it was a science fair project but didn't mention it was a physics project, and what aspect of the skis are you even comparing?? Sidecut? surface area? Flex? Torsion? edge pressure? Friction? Aerodynamics?

Straight and carving skis both obey the same laws of physics.

And seeing as doing a google search on "ski physics" IS too difficult for you I came up with the following articles, if you decide which aspect of ski physics you are comparing then maybe some of them will be useful.











"Son, you don't have bad luck. The reason bad things keep happening to you, is you're a dumbass" - Red Foreman
post #15 of 16
I skiied straight skis for over 30 years before switching to "shaped" skis.
The bottom line that I found is, with good carving technic and a perfectly groomed hill, a good quality straight ski will do just about everything a shaped ski will do.

Where shaped skis excel, is when the skier does not possess good carving skills and/or the snow conditions are poor. With my Rossi B-2s, I have the feeling that I can go anywhere in almost any conditions and still ski the same. I never felt that secure with my straight skis.

However, I still enjoy an occasional early morning groomed run on my old Rossi 7Xs' (GS straight 204cm), carving big round high speed GS turns all the way down. Then they get put away at lunch and on to the B-2s (my "Hero skis").
post #16 of 16
The practicality of such a comparison in 2005/2006 is unclear to me. For practical purposes it´s about 10 years late.

As an academic project, it is, IMHO, slightly better than the classical issue of how many angels there could be on the tip of a needle.
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