A quantitative measure for ski flex

[corona]

Why does this not exist? In any ski review or marketing info skis are always just 'soft' or 'stiff' but there is never an actual value given to flex. It's always based on someone's opinion. If it's a ski racer reviewing a stiff park ski they'd probably say it's a soft ski, but someone who skis a buttery park ski would probably say your average all mountain ski is a stiff ski.

I propose reviewers take a few minutes and take an actual measurement of flex. It doesn't need to be complicated. It could be as simple as: a ski flex of 40 means it takes 40 lbs to flex the ski 1 inch when blocks are placed 3 feet apart centred on true centre. Of course this doesn't take into account changes in flex pattern over the ski, but it's a good starting point.

Or take a measurement for the whole ski and normalize for length. Or many flex points along the ski to make a flex curve (I bet ski makers do this).

It would be super useful information to go alongside dimensions and turn radius.

 

[a_pla5tic_bag]

I wish they did this for boots too. Like make some human leg analog and have a graph of force applied on x axis and distance flexed or something on y.

 

[TRVP_ANGEL]

or...

 

[Cryptno]

I wish they did this for boots too. Like make some human leg analog and have a graph of force applied on x axis and distance flexed or something on y.

What? They have this, maybe full tilt but everyone sells boots ranging from like 40 flex to 140 flex

 

[Woos]

What? They have this, maybe full tilt but everyone sells boots ranging from like 40 flex to 140 flex

And none of those numbers are regulated or agreed upon by these companies either. A 40 flex from one company could be a 60 according to another. So no, they do not have this.

 

[Cryptno]

And none of those numbers are regulated or agreed upon by these companies either. A 40 flex from one company could be a 60 according to another. So no, they do not have this.

I see what your saying. I just thought he meant no scale in general.

 

[Cryptno]

Why does this not exist? In any ski review or marketing info skis are always just 'soft' or 'stiff' but there is never an actual value given to flex. It's always based on someone's opinion. If it's a ski racer reviewing a stiff park ski they'd probably say it's a soft ski, but someone who skis a buttery park ski would probably say your average all mountain ski is a stiff ski.

I propose reviewers take a few minutes and take an actual measurement of flex. It doesn't need to be complicated. It could be as simple as: a ski flex of 40 means it takes 40 lbs to flex the ski 1 inch when blocks are placed 3 feet apart centred on true centre. Of course this doesn't take into account changes in flex pattern over the ski, but it's a good starting point.

Or take a measurement for the whole ski and normalize for length. Or many flex points along the ski to make a flex curve (I bet ski makers do this).

It would be super useful information to go alongside dimensions and turn radius.

Technically you could just go off of the core if its wood. I have seen a chart from Ski Lab. Of course this doesn't take into account metal inserts, the rest of the ski, or the thickness.

 

[a_pla5tic_bag]

Technically you could just go off of the core if its wood. I have seen a chart from Ski Lab. Of course this doesn't take into account metal inserts, the rest of the ski, or the thickness.

I mean thats useless, it's like weighing the chassis of a car prior to addition of all the other stuff and calling that the curb weight. It need s to be done with a ski i can buy off the shelf, and probably for every length too.

 

[Cryptno]

I mean thats useless, it's like weighing the chassis of a car prior to addition of all the other stuff and calling that the curb weight. It need s to be done with a ski i can buy off the shelf, and probably for every length too.

Not really, a core is what gives a ski its stiffness so if you just found what kind of core they had you could go off that, I cant imagine length has that big of a effect because they don't switch the construction from a 152 cm to a 186 cm. Thickness is another big factor. It also would depend on where you want stiffness. underfoot? tips and tail? Plus there are different kinds of stiffness. Blizzards are really stiff coming out of a turn because the metal plate they use snaps back, race skis are just stiff all over.

 

[Session]

Not really, a core is what gives a ski its stiffness so if you just found what kind of core they had you could go off that, I cant imagine length has that big of a effect because they don't switch the construction from a 152 cm to a 186 cm. Thickness is another big factor. It also would depend on where you want stiffness. underfoot? tips and tail? Plus there are different kinds of stiffness. Blizzards are really stiff coming out of a turn because the metal plate they use snaps back, race skis are just stiff all over.

Man, all this time I thought that the layup had something to do with the stiffness of a ski. Now I know it's just the core.

 

[hi_vis360]

you're def onto something but there are so many variables. Like you said the flex pattern is super different between skis, and also that test with the wood blocks would have to be adjusted for ski length as well. Different core materials flex differently too. Some skis become more flexy as you ride them, whereas others maintain their flex a lot more.

This is definitely a good idea, but I think it's easier said that done

 

[a_pla5tic_bag]

you're def onto something but there are so many variables. Like you said the flex pattern is super different between skis, and also that test with the wood blocks would have to be adjusted for ski length as well. Different core materials flex differently too. Some skis become more flexy as you ride them, whereas others maintain their flex a lot more.

This is definitely a good idea, but I think it's easier said that done

It wouldn't be easy but it's 100% doable. All those things that are different between skis is what we're looking to measure, adjusting for length isn't really an issue. There's probably some issues to overcome but humanity has dealt with way more complicated things that standardizing/empirically measuring ski flex. I'm sure if a few smart guys got together they could easily build a machine to do this.

The real trick is that there's no financial incentive to do this incentive to do this, in fact you'd likely lose money.

 

[hi_vis360]

It wouldn't be easy but it's 100% doable. All those things that are different between skis is what we're looking to measure, adjusting for length isn't really an issue. There's probably some issues to overcome but humanity has dealt with way more complicated things that standardizing/empirically measuring ski flex. I'm sure if a few smart guys got together they could easily build a machine to do this.

The real trick is that there's no financial incentive to do this incentive to do this, in fact you'd likely lose money.

I agree but If you were doing the test OP suggested with placing blocks three feet apart from true centre you definitely would have to adjust for length

 

[plugs]

A test like wood blocks wouldn’t work because it wouldn’t account for torsional stiffness which has a lot to do with how a ski rides and it wouldn’t account for progressively flexing skis. At the end of the day you have to make your way out to a ski shop if you really want to know what the flex is of a ski or look at comparisons to other skis. Also ski reviews usually have a bio for the reviewers so you can get an idea of their height weight and a little background bio.

 

[Cascara]

I know this doesn't fully answer your questions but here are my two cents on why the manufacturers don't publish it.

I am the Design Engineer for Line Skis and; this is a question that we deal with all the time. Internally, we measure all of our skis in a 3 point bend (running surface only) to determine the bulk stiffness. Our test is pretty simple and can be replicated at home with simple weights and a ruler.

A detailed video of our setup can be found here:

(skip to 1:49):

At Line, we support a ski at the fore-body and aft-body contact points. We deflect the ski 1 inch and measure the load applied. The load and deflection give us a bulk stiffness (lbs/in). We do a similar thing for torsion and pressure distribution but that is beyond the scope of this thread. Bulk stiffness data is useful for internal comparisons of skis and for pairing skis but isn't all that meaningful to the end user.

Bulk Stiffness data can be extremely misleading as running surface lengths change. A small change in span makes a huge difference in measured stiffness. (Defining a running surface was easy when skis were all traditional camber but it is much more complicated with rocker.)

The bulk stiffness is only a small part of the full stiffness puzzle. The most important thing to a skis on-snow stiffness is the distribution of flex/stiffness throughout the skis length. Skis with a higher bulk stiffness will often feel softer on snow if the flex profile is extremely soft in the tips and tails. The stiffness distribution/flex profile is the real magic in ski design and is highly proprietary. We try to communicate stiffness as an on-snow feeling because that is the easiest and most meaningful information to the end user... skiers.

Hope that helps!

**This post was edited on Dec 11th 2018 at 6:36:13pm

**This post was edited on Dec 11th 2018 at 6:38:19pm

 

[johnblaze]

Here's the test I have used for years. Hold the ski up by the tip and put ski between your legs with the tail on the ground behind you. Do 3 squats pressing your crotch down onto the center of the ski and give it a good flex. If by the 3rd squat you're feeling that special tingle, you found your ski.

 

[steve0]

Great question O.P. and good post. nhrida...

The Hockey Industry has done a pretty good job of this with composite sticks. Bauer, CCM, and warrior all give flex ratings for their sticks. An adult stick is usually an 80, 90, 100, or 110 flex, and is typically marked for varying flexes if you cut it shorter.

As nhrida explained though, that's only half the story. The flex profile is really what makes the ski or stick feel different. In hockey it's referred to as kick-point, and can make a stick better for big slap-shots, or quick wrist shots. Skiing is similar, different flex profiles are what really make a ski feel different, not just the overall flex, and that's complicated to try and quantify.

 

[tino_]

Not really, a core is what gives a ski its stiffness so if you just found what kind of core they had you could go off that, I cant imagine length has that big of a effect because they don't switch the construction from a 152 cm to a 186 cm. Thickness is another big factor. It also would depend on where you want stiffness. underfoot? tips and tail? Plus there are different kinds of stiffness. Blizzards are really stiff coming out of a turn because the metal plate they use snaps back, race skis are just stiff all over.

There are construction differences between ski lengths though. Not that different materials are used between different lengths, but the core of longer skis is generally thicker to make them more stiff and keep the same on-snow feel between sizes. See this article for more info:https://blisterreview.com/gear-101/skiing-101/construction-changes-in-longer-skis

 

[tino_]

Great question O.P. and good post. nhrida...

The Hockey Industry has done a pretty good job of this with composite sticks. Bauer, CCM, and warrior all give flex ratings for their sticks. An adult stick is usually an 80, 90, 100, or 110 flex, and is typically marked for varying flexes if you cut it shorter.

As nhrida explained though, that's only half the story. The flex profile is really what makes the ski or stick feel different. In hockey it's referred to as kick-point, and can make a stick better for big slap-shots, or quick wrist shots. Skiing is similar, different flex profiles are what really make a ski feel different, not just the overall flex, and that's complicated to try and quantify.

I agree that a single flex rating will not tell you a ton about a ski's characteristics, but I think it would help to give you a general idea. From the hockey stick example, even if the kick point is different between two sticks, the flex rating still gives you a good idea of how much force you'll need to properly flex the stick. I think the same would be true for skis.

However, it would probably be really complicated to give skis a simple rating like hockey sticks. There is definitely a larger variance in flex along the length of a ski than there is along the length of a hockey stick, which would make it difficult to give one number as a ski's flex rating. I think it would need to be done the way Blister rates flex on skis, with different values for each part of the ski.

Really interesting topic, I would like to see the measurements for flex ski companies use in the design process.

 

[Cryptno]

There are construction differences between ski lengths though. Not that different materials are used between different lengths, but the core of longer skis is generally thicker to make them more stiff and keep the same on-snow feel between sizes. See this article for more info:https://blisterreview.com/gear-101/skiing-101/construction-changes-in-longer-skis

Ok, I didn't know that. But as you said yourself, its more to keep a uniform feel than it is to change stiffness. A 152 cm still feels the same as a 186 cm.