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Can you "bend" new skis with metal like the Blizzard Cochise?

post #1 of 20
Thread Starter 

So back in the day, if you skied alot moguls conventional wisdom was to avoid skis with a lot of metal, like most of the GS race gear, because you would risk, and likley end up bending the ski. 

 

Advance to today, and skis like the Cochise run metal layers, but yet you dont hear the same concerns about the skis getting bent in bumps....why not?

 

Is it a case the metal is different, then old school skis and is less likley to bend?  Or is it a case of people just not realising? Or something else?

post #2 of 20

Don't those ski come pre-bent.  I think they call it flip-core.

post #3 of 20

Metallurgy's come a long way since the Rossi Roc 550 days where lot's of proto 'early rise' was happening  much to their owners' chagrin: 

 

"Titanal (aluminium, zinc, magnesium, copper, zirconium) a product of Austria Metall AG. Commonly used in high performance sports products, particularly snowboards and skis."

 

- wikipedia

 

search and you shall find! 

 

http://www.amag.at/AMAG-Titanal-R.1193.0.html?L=0

 

 

"AMAG Titanal®

 
 
 
 

AMAG repeatedly enlivens the market with innovations, especially in .... "

 

 

It's all about that modulus of elasticity. smile.gif

post #4 of 20
Thread Starter 

Cool, I was told that it was the "Titanal" but no-one could tell me "why" or what exactley Titanal even was...as I undertood the article, the titanal is very very thin, yet still provides the benefit of older thicker metal...but due to being thin, it is much less likley to deform.   Right?

post #5 of 20

I'm guessing it also has a lot to do with it's ability to bond to other laminates, but yes, I'm sure there's just been mods to the formula over the years that have upped the MoE. Other than the wood cores, most of what skis are made of wasn't around 30-40 years ago, chemically or metallurgically. 

post #6 of 20
Quote:
Originally Posted by Skidude72 View Post

So back in the day, if you skied alot moguls conventional wisdom was to avoid skis with a lot of metal, like most of the GS race gear, because you would risk, and likley end up bending the ski. 

 

Advance to today, and skis like the Cochise run metal layers, but yet you dont hear the same concerns about the skis getting bent in bumps....why not?

 

Is it a case the metal is different, then old school skis and is less likley to bend?  Or is it a case of people just not realising? Or something else?

Something else. Maybe as simple as the skis were long and frequently got into a bad trough or something. My early metal skis pre-dated tight moguls on the hill. By then I had Olins and such. Never bent a metal ski, Kaestle RS's, Fischer Alu's, Head Comp's, Atomic Bionic RS Volkl Explosiv.
,. Today people can put the skis where they want to more easily and avoid stressing the ski, due to a skis easier turning perfomance and shorter length. And groomed slopes pob' save a lot of skis.

 

Titanol is a type of aluminum. Named 6064 I think, like used in high end bicycle frames. I don't think it's all that thin in the construction, relatively or absolutely. Some of the companies provide that thickness information, like .5mm or something.

 

Agree, some of the advancements are likely in adhesives.

post #7 of 20

I would second the notion that it's the thinness of the Titanal that eliminates bending. When you hold a ski like the Bonafide and look at it's sidewall, you can see where the thin layers of metal are. Looking at this, you can see why it'd be irrational to think that this thin layer could bend the entire ski. More likely, your ski would literally be split and the core shattered, with just the top sheet remaining bent and intact.

 

In short... you won't be bending the metal in these skis unless your entire ski is broken beyond repair.

 

-Matt @ Skiessentials.com

post #8 of 20

Metal skis still bend, I see it fairly often. I'd agree with the poster above who mentioned shorter skis and, let's face it, people ski bumps a lot less and quite a bit differently than they used tp.

post #9 of 20

It appears Joey Cordeau is skiing the bumps below on a pair of  Stockli Laser GS, which has titinal in it (see the slow-mo at 5:20):

 

post #10 of 20

^^^ If the Stockli isn't already bent, it will be. I am 100% positive about that. He is skiing very smooth in the portion of video I watched, but those skis are absolutely doomed.

post #11 of 20

Warning, nerd alert...

 

This thread piqued my curiosity about metal alloys used in modern ski construction.  I am a mechanical/aerospace/biomedical engineer, so I would like to think I understand the structural aspects a little.  Modern skis are laminated composite structures (beams) typically with layers of plastic at the top and bottom (base and topsheet), fiber-reinforced composites (fiberglass, carbon fiber, maybe kevlar) and/or metal next, with wood or foam cores, all bonded together with resin/glue. 

 

The way I see it, skis bend because the metal layers yield (undergo plastic deformation).  I guess you could bend a ski without metal, but I think that would be a case where some components were cracking or de-bonding.  I think the carbon, glass and wood components are not ductile enough to bend, but would crack (fracture) instead of yield.  So, the most important material property of the metal that determines when a ski will bend (and stay bent) is the yield strength.  To actually break the metal you have to exceed the ultimate tensile strength.  Different alloys of aluminum have very similar stiffness, but can have very different yield and ultimate tensile strengths.  Thin layers will have lowers stresses in pure bending, but if they are at the outer layer of a composite beam they will see mostly tensile stress.  Thicker layers would be stronger in tension.  I have seen layer thicknesses of 0.5-1.2 mm quoted in ski specs.  A thicker layer should make for a stiffer ski that is less likely to yield in tension.  I have not studied dynamics too much, so I don't have a good feel for why skis with more metal might feel more heavily damped compared to all carbon layups.

 

It was interesting to look at the Titanal link markojp posted.  I always thought Titanal was a titanium-aluminum alloy, but it is in fact a 7000-series aluminum (which includes no titanium).  Similar alloys are used in aerospace applications and bike frames.  I don't know what types of metal were used in older skis, but I am guessing it might have been 6061 aluminum.  Titanal has a yield strength about twice as high as 6061 (http://www.amag.at/fileadmin/AMAG/AMAG/Pictures_NEW/AluReport/AR_3_09_EN_Sports.pdf).  AMAG also claims better adhesion for Titanal due to a porous anodized coating.

 

So, I think newer skis probably bend less frequently because they are using stronger materials, better design, and better manufacturing processes.

post #12 of 20

Yield strength... are we talking about modulus of elasticity, or failure? I'm assuming the former, correct?

post #13 of 20

"modulus of elasticity"

 

Great rock band name. No doubt would become MOE, but very cool.

post #14 of 20

Here's a photo of my friend's Enforcers after his last day at Homewood.   He managed to get them straightened and says they still ski like new.

 

 

post #15 of 20
Marlojp: Modulus of elasticity is the stiffness of a material (how much deflection for a given applied force). Yield strength is not ultimate failure (complete breakage) , but if you stress a material beyond the yield strength it does not go back to the original shape.
post #16 of 20
Yes! That's right! I thought I was screwing it up... It's been a few years since my structures courses. Thanks for helping me get that sorted out!
post #17 of 20
Quote:
Originally Posted by Whiteroom View Post

^^^ If the Stockli isn't already bent, it will be. I am 100% positive about that. He is skiing very smooth in the portion of video I watched, but those skis are absolutely doomed.

Hmm. Pretty soft snow. Agree on the style = doom, but maybe when he's back here on some real bumps with the consistency of steel ingots. 

Quote:
Originally Posted by BTMac View Post

Warning, nerd alert...

 

This thread piqued my curiosity about metal alloys used in modern ski construction.  I am a mechanical/aerospace/biomedical engineer, so I would like to think I understand the structural aspects a little.  Modern skis are laminated composite structures (beams) typically with layers of plastic at the top and bottom (base and topsheet), fiber-reinforced composites (fiberglass, carbon fiber, maybe kevlar) and/or metal next, with wood or foam cores, all bonded together with resin/glue. 

 

The way I see it, skis bend because the metal layers yield (undergo plastic deformation).  I guess you could bend a ski without metal, but I think that would be a case where some components were cracking or de-bonding.  I think the carbon, glass and wood components are not ductile enough to bend, but would crack (fracture) instead of yield.  So, the most important material property of the metal that determines when a ski will bend (and stay bent) is the yield strength.  To actually break the metal you have to exceed the ultimate tensile strength.  Different alloys of aluminum have very similar stiffness, but can have very different yield and ultimate tensile strengths.  Thin layers will have lowers stresses in pure bending, but if they are at the outer layer of a composite beam they will see mostly tensile stress.  Thicker layers would be stronger in tension.  I have seen layer thicknesses of 0.5-1.2 mm quoted in ski specs.  A thicker layer should make for a stiffer ski that is less likely to yield in tension.  I have not studied dynamics too much, so I don't have a good feel for why skis with more metal might feel more heavily damped compared to all carbon layups.

 

It was interesting to look at the Titanal link markojp posted.  I always thought Titanal was a titanium-aluminum alloy, but it is in fact a 7000-series aluminum (which includes no titanium).  Similar alloys are used in aerospace applications and bike frames.  I don't know what types of metal were used in older skis, but I am guessing it might have been 6061 aluminum.  Titanal has a yield strength about twice as high as 6061 (http://www.amag.at/fileadmin/AMAG/AMAG/Pictures_NEW/AluReport/AR_3_09_EN_Sports.pdf).  AMAG also claims better adhesion for Titanal due to a porous anodized coating.

 

So, I think newer skis probably bend less frequently because they are using stronger materials, better design, and better manufacturing processes.

Hey, appreciate the input. We need more engineers and fewer speculators like me. Have a question: In composite beams, assume we're talking cross sectional areas, how is the total resistance to bending calculated?

post #18 of 20
Quote:
Originally Posted by BTMac View Post

Warning, nerd alert...

 

This thread piqued my curiosity about metal alloys used in modern ski construction.  I am a mechanical/aerospace/biomedical engineer, so I would like to think I understand the structural aspects a little.  Modern skis are laminated composite structures (beams) typically with layers of plastic at the top and bottom (base and topsheet), fiber-reinforced composites (fiberglass, carbon fiber, maybe kevlar) and/or metal next, with wood or foam cores, all bonded together with resin/glue. 

 

The way I see it, skis bend because the metal layers yield (undergo plastic deformation).  I guess you could bend a ski without metal, but I think that would be a case where some components were cracking or de-bonding.  I think the carbon, glass and wood components are not ductile enough to bend, but would crack (fracture) instead of yield.  So, the most important material property of the metal that determines when a ski will bend (and stay bent) is the yield strength.  To actually break the metal you have to exceed the ultimate tensile strength.  Different alloys of aluminum have very similar stiffness, but can have very different yield and ultimate tensile strengths.  Thin layers will have lowers stresses in pure bending, but if they are at the outer layer of a composite beam they will see mostly tensile stress.  Thicker layers would be stronger in tension.  I have seen layer thicknesses of 0.5-1.2 mm quoted in ski specs.  A thicker layer should make for a stiffer ski that is less likely to yield in tension.  I have not studied dynamics too much, so I don't have a good feel for why skis with more metal might feel more heavily damped compared to all carbon layups.

 

It was interesting to look at the Titanal link markojp posted.  I always thought Titanal was a titanium-aluminum alloy, but it is in fact a 7000-series aluminum (which includes no titanium).  Similar alloys are used in aerospace applications and bike frames.  I don't know what types of metal were used in older skis, but I am guessing it might have been 6061 aluminum.  Titanal has a yield strength about twice as high as 6061 (http://www.amag.at/fileadmin/AMAG/AMAG/Pictures_NEW/AluReport/AR_3_09_EN_Sports.pdf).  AMAG also claims better adhesion for Titanal due to a porous anodized coating.

 

So, I think newer skis probably bend less frequently because they are using stronger materials, better design, and better manufacturing processes.

Thanks for posting this.  Here's my thinking on this.  I'm not a materials scientist, so I'd be interested to hear your comments:  

Let's suppose you have two different metals, A and B, with the same elastic modulus (stiffness), but metal A has the higher yield strength.  Further assume that both are used in the composite ski construction you've described above.  Because they have the same elastic modulus, they will contribute the same stiffness to the ski (assuming their thicknesses are the same, of course).  However, because metal A has a higher yield strength, the ski made with this metal can be bent into a tighter radius of curvature without permanent deformation.  

 

More generally, it seems it follows that, for a given elastic modulus, a higher yield strength means not only that the material can sustain a higher force before it reaches its elastic limit, but a greater degree of elongation as well.  And I'm thinking it's really the "elastic elongation limit" (not sure what the proper technical term is, but I'm referring to the maximum dimensional elastic deformation) that you want.  I say this because skis are engineered to achieve a given stiffness.   Thus it seems to me that maximizing robustness is not about maximizing resistance to deformation (i.e., making the skis so stiff they can't be bent much), but rather about making it so that, for a given stiffness, they can bend as much as possible without sustaining permanent deformation.

 

Hmmm...so I guess what you'd really want to maximize robustness would be a high yield strength and a low elastic modulus -- that's would give you the greatest elastic elongation limit.  Though of course you wouldn't want the elastic modulus to be too low -- then you'd need too much mass to meet your stiffness target.


Edited by chemist - 3/31/13 at 1:30am
post #19 of 20
Quote:
Originally Posted by beyond View Post

Hmm. Pretty soft snow. Agree on the style = doom, but maybe when he's back here on some real bumps with the consistency of steel ingots. 

Hey, appreciate the input. We need more engineers and fewer speculators like me. Have a question: In composite beams, assume we're talking cross sectional areas, how is the total resistance to bending calculated?

In laminated heterogeneous materials it's more complicated.  But if by "resistance to bending" you mean stiffness rather than resistance to elastic deformation, then: the stiffness of a sheet of material of a given width is proportional to the inherent stiffness of the material (aka modulus of elasticity or Young's modulus) times the thickness cubed (I think this is in the thin-plate limit, so if the material were thick this relationship would break down).  

 

So if you want to increase the stiffness while keeping the mass the same, it's much more effective to find a material with a lower density than one with a higher Young's modulus.  Because, for a given mass of material, if you double the Young's modulus you double the stiffness.  But if you find a material with the same Young's modulus but half the density, you can make it twice as thick (for the same mass), which yields an 8-fold (2^3) increase in stiffness.  The highest-performing metal in this regard is beryllium, because it is relatively stiff yet incredibly light. Probably overkill to use it in skis, though.

post #20 of 20

I have bent skis as recently as my first gen of rockered Katanas.... I also ski bumps pretty hard some of the time.....

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