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"Flex" question from new skier

post #1 of 11
Thread Starter 
Hi folks, i'm reading some tidbits more and more about "flex" ratings associated with skis. I would like to educate myself on this subject, could some of you school me on "flex" ? Thanks !

                                         Rich K.

PS is there a "search" feature on this forum ? I'm not seeing one..
post #2 of 11
Hi Rich,
Welcome to EpicSki!
To answer your last question first - yes - the search bar is along the top, the white bar under the HOME/GEAR/FORUMS/WIKI/PROFILE headings.

When you ask about flex, do you mean in the boots or in the skis?
In both cases it means roughly the same thing (I'm not an instructor, I'll use the simple terms that make sense to me, and hope they make sense to you)

"Flex" means how easy it is to bend or twist something. For a ski boot, it means how easy it is to push forward on the cuff (vertical bit of the boot that goes up your leg). The softer the flex, the easier the boot is to ski in. Racers use very stiff flex boots, but by being stiff they are uncomfortable and you have to be more precise to control them.

Flex in skis works roughly the same way - racers use very stiff skis. There are two types of flex in a ski - longitudinal and torsional. I'm not going to bother about torsional - it's how easy the ski is to twist. To see how much longitudinal flex a ski has, you could stand it upright, hold on to the tip, make sure the tail won't move, then push in the middle. The ski will flex into an arc shape.
The easier it will do that, the easier it will flex into the shape needed to make a turn. But the drawback of that is that it doesn't go as fast.

So, in summary, it's easier to learn on a soft flex boot and soft ski, then progress up stiffer as you get better.

Hope that helps (or at least doesn't confuse you any more!)
post #3 of 11
Thread Starter 
Wow, awesome read ! Thanks for the flex details !
post #4 of 11
If you turn things upside down, you can look at your ski as a beam with only one column, located in the middle holding it up.  The load on this beam is the the snow piled up on top of it.  The behaviour of this beam is governed by beam-deflection equations that are well-understood by good civil engineers.  All you need to know is that the greater the load, the more the beam bends, and the stiffer the beam, the less it bends for any given load and a load in the middle of the beam, right on top of the column won't bend the beam at all, but a load at the ends will bend it a lot.

Now turn it right side up.  As you ski forces act on the ski and these forces are transmitted through the boot and binding to you and turn you where you want to go if you manage things correctly.

If the ski is too soft, the loads at the tip cause the ski to bend more and angles to change so that the ski can end up loosing it's grip.  You want a nice stiff ski if you are going to want to have big forces at your disposal.

If the ski is too stiff, it cannot be bent without a lot of force existing at the tip and tail.  You want a ski that is soft enough to bend at the forces you will be able to apply to it.

You want the ski to be able to bend the ski into a nice arc so you can "arc" turns by bending the ski into the shape you want layed out in the snow to be able to ski along that path without skidding sideways across your edges.

Stiffer skis are harder to manage because they get the load out to the tips and tails, where they have a longer lever arm and can exert more torque on you.  Softer skis keep the load in the centre of the ski so they are easier to manage.

Torsional stiffness describes how easy it is to twist the ski.  The applied load on an edge can only be transmitted if the ski resists twisting.  A weak ski will twist before transmitting much load, thus reducing the forces you have to deal with by losing its grip.
post #5 of 11
As a beginner it is important not to buy a high performance ski (i.e. very stiff) that is beyond your abilities.  Many beginner skiers think that by buying an expensive high end ski that it will make them a better ski, when in fact it does just the opposite.  If you do not have the ability to control a high performance ski it will be taking you for a ride, instead of the other way around.  The proper flex is determined by a combination of your weight, ability, and the speed and snow conditions you nomally ski.  A  softer flexing ski, especially in the tail, is generally "more forgiving" and will be a better and more enjoyable learning tool.  The general rule is that for soft snow you use a soft ski, and for hard snow you use a stiffer one.
Edited by mudfoot - 11/21/09 at 8:17am
post #6 of 11
Rich, trying to learn to ski with stiff skis or stiff boots is like trying to learn to drive in a Ferrari...or Peterbuilt truck.  It makes things much harder.

The flex of any ski model increases as it is made in longer lengths.  Picking the right ski for any person is a very inexact skill.  The way a person flexes the ski depends on the energy they put into it from their weight, their height, their strength, the speed they ski, and their skill level.  For the same size person with the same model ski, a higher energy skier will like a size longer.

We always recommend that skiers try to demo skis before they buy, and that is often hard to arrange.  For advancing skiers, it is often better to rent skis or take out a yearly lease on skis so they can advance their skis the next season.  Also, for skiers who only ski a week or ten days a year, it may be cheaper to rent than to buy.  Good rental shops have skis of various sizes and skill levels.  One advantage of renting at a destination resort or at the hill is that the shop may be talked into swapping skis to try different models and sizes.
post #7 of 11
Thread Starter 
Man, I hope I didn't purchase skis that are too stiff for my beginner level. I just purchased a super clean, used pair of Rossi 160cm Cut 10.7's. What behavior can I expect from skis that are too stiff? Thank you for all the help!

                                                              Rich
post #8 of 11
Stiffer skis need to be skied with your weight forward, but beginner/intermediate skiers tend to ski "in the back seat."  A ski with a stiff tail will work better if you are in the middle or with weight a little forward, but it will want to accelerate forward out from under you if you get your weight back. Also, you need to flex the ski (reverse the camber) in order to make it turn without just skidding it into a new direction.   The stiffer the ski, the more energy you need to make it flex, so stiff skis may work very well going fast when your weight and momentum can load them up, but will be sluggish and uncooperative at slower speeds.  The shorter your ski is, the more weight you have pushing on it per square inch, so the more easily you will bend it.

I am not familiar with those skis, but 160 is fairly short, so unless you are a real light weight, I don't think you should have any problems.

P.S. I found this info, and it sounds like they should be perfect for a  beginner.

Summary:
The Rossignol Cut 10.7 are all around good skis, especially for the price. They are awesome for resorts and they seem to do well in the backcountry as well. 3-4 foot deep snow seems to get the better of them however. All in all if your just starting they are great skis to buy for the price, and they can take a beating. One other thing if you do get a pair add some stickers or something because these skis are very common on the slopes, and someone will walk away with yours on accident. Enjoy.

post #9 of 11
Thread Starter 
Thanks mudfoot for the input, sounds like my Rossi Cut skis will be fine for now.. realistically, one would think that most shorter adult skis are engineered towards beginner/intermediate users, so hopefully the "term" forgiving plays into these skis' design !
post #10 of 11
Richkay:

It sounds like you have made a very good ski choice.  Something to be aware of is the other end of the stiffness/length equation.  If you are on a ski that is too short and/or soft it will have trouble holding an edge on hard snow.  If your weight and momentum overpower the ski it will tend to chatter (bounce) when you properly weight it to carve a turn.  Be advised that this can also occur because you are not weighting it properly because your techniuqe has you off balance.  Once you get to a point where you feel comfortable and are turning pretty well on the skis, if you notice that they get unstable at higher speeds, it may be time to go to a slightly stiffer and longer ski.

Good luck, hope you have a great season.  MF
post #11 of 11
Thread Starter 
Thanks everyone for the read. I'm all good on "flex" now ! I am 5'11", and weigh 155 lb. so I think 160cm beginner skis will be perfect for me for a year or two, we'll see how I advance...
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