Long skis

[onix]

This past weekend I saw a race advertised as the world's fastest non-motorized sport - speed skiing. They guys were doing 150+ mph on 60 degree slopes. One dude wiped at 151 mph. I noticed the length of their skis weren't the 210+ that a lot of experienced skiers boast, but instead more like 180's.

I have been told that longer skiier are faster, but I've had my doubts. What's the real truth? I don't need a sophomore physics argument, that friction is propotional to weight normal to surface, etc. My speculations/theories are:

• Longer skiis keep one "afloat" above the snow, and that way not so much is being "pushed" out of the way.

• Longer skiis help with stability, and eliminate energy losses due to chatter, sideways motion, etc.

I did notice that for speed-skiing the trails were specially groomed.

Added 1:34PM PST, July 26, 2005

Well I guess I was wrong about length. The speed skiis are actually much longer.

http://www.speedski.com/PopularMechanics.htm

I've noticed that speed skateboards are also long...

 

[jagec]

Hmm...I'd guess you're right about longer skis keeping you from "sinking" as far in the snow, and thus you lose less energy that way. HOWEVER, you lose more energy through friction on the bottom of the ski.

So, ideally, you want the thinnest and shortest ski which will keep you fully "afloat" on a given surface. So the snow is the limiting factor: you probably want tighter packed snow, as smooth as possible. If the snow is loose, or uneven, it will make the skis sink or chatter more, so you need bigger skis to avoid that.

I guess you just get smaller and smaller skis the harder the surface. The limit of which is basically ice skating: a tiny "ski" on very tightly packed, smooth "snow".

 

[CycloWizard]

I'd speculate that the long skis are used because they're more stable and will keep you going straighter, in addition to the reasons you mentioned. I can't recommend anything that might make you suddenly turn when goingo 150 mph.

 

[KoolAidKid]

Long skis are generally faster. I would speculate that this is because your body weight is distributed over a larger surface area, thereby allowing you to stay as close as possible to the top of the snow layer. If you sink in the snow the most resistance would be at the front tip of the ski. The increased friction incurred by having a larger snow/ski interface would be overcome by minimizing the amount of snow that the tip of the ski has to plow through. As I said, just a guess.

 

[Glib]

Length is mostly for front/back stability; once you get to a certain length, width of the ski will be a greater determining factor in surface area, and narrower skis will be faster. The industry has given us examples of this with the wide, slower skiing "powder skis" that offer plenty of lateral stability and keep skiers on top of the snow, but produce lots of chatter as you try to ski faster in them.

 

[CreativeTom]

I think going with more narrow ski's are actually more benificial then longer

 

[George Powell]

For all out speed there is likely to be a sweet spot on ski length and width. For normal use however most people find a shorter wider ski better because it offers you more control, you are able to perform tighter turns and can more easily navigate power conditions. The base treatment is likely to be more important than length for an extreme speed challenge. I doubt that normal ski wax would be too great at 150mph.

 

[GZDonner]

There are huge differences the types of responses you get with different sizes, widths, camber and "shape" of skis. Those speed races use the longer, slightley fatter ski. I dont need to repeat why because it was discussed above only because the only factor going that fast with skis is the stability issue, and you get it with the longer ski.
Another factor is the wax, good wax will turn the snow into water molecules when you ski over it, it then refreezes as you ski on. Thats why sometimes you can see a light reflection off of the track the ski lives behind on a flat carve.
That being said, big skis arent good for going down double blacks unless there is 6 feet of untracked fresh. keep em on the groomers

 

[colincsl]

The main reason for a lot shorter skis these days is that with the curve of the ski you can ski much better when they aren't as long. This is for normal skis however, so I'm not sure about speed skis. I got a pair of all terrain K2 165cm for last christmas and I'm 5'10," 138lb.

edit: I wouldn't really trust that article very much. Things have changed drastically since 1994.

 

[GZDonner]

Originally posted by: colincsl
The main reason for a lot shorter skis these days is that with the curve of the ski you can ski much better when they aren't as long. This is for normal skis however, so I'm not sure about speed skis. I got a pair of all terrain K2 165cm for last christmas and I'm 5'10," 138lb.

edit: I wouldn't really trust that article very much. Things have changed drastically since 1994.

It's not that the shorter skis make you better, they just make carving easier than the longer ones. What makes you better is being able to carve the same railroad tracks that the smaller skis can do but with longer ones. And yes you're right, a lot has changed since 1994

 

[Glib]

If you're interested in carving S turns, then the newer, shorter skis you see nowadays with wider tips are ideal. The hourglass shape allows the entire inner edge of the downhill ski to carve your turn, keeping you smooth and stable throughout the turn. In the 80s and before, longer skis were preferred because they gave you front-back stability as well as additional bend in turns so that you could hold an edge. All the same, most people skidded through turns and pretty S turns were somewhat rare.
The newer designs are amazing.

 

[George Powell]

An example of a trick carving ski. Looks more awesome in real life.

Streetracer.

 

[wedi42]

i used to work in a ski rental shop, we like to have fun with customers. we had to ask people their experience level to give them the right equipment.
whenever someone said they never skied before i'd tell them 'ski are rated by their top speed in mph, so here are some 150's'
the look on their faces was great!

 

[Chef Brian]

Shorter, narrower skis are faster. If you can keep yourself stable on them, that is. My skis are 190s and I'm only 5'8 (I'm seventeen), so obviously I can't cope with the short and narrowness. Not recommended for non expert skiers!