Pure carbon skis?

[Sonny]

Ok, so the building is back on!

This time I'm building two pairs of skis. One pair light(?) touring ski and one more everyday powder ski. I've tryed finding examples of people using only Carbon fiber CF, in their layup but didn't really find any?

I would greatly appriciate if anyone who have used carbon in skis or snb would input on this idea?

The idea is poplar core, with bamboo sidewalls and 21 oz uni dir CF both over and under. No fiberglass. Is this stupid? And lets pretend carbon isnt 10x as expensive... I've read that CF expands and retracts with heat changes, since we press at only elevated room temperature is this still a problem for us?

How will 21oz (600gram) uni CF behave compared to tri ax 22oz fiberglass?

Also I the prime reason for doing this is that we want to try carbon, and also it looks really Bad ass

[ben_mtl]

I would say you still need fiber reinforcement at +45/-45, which UD Carbon doesn't provide.
I do have a sample of Triax Carbon and was thinking of using it with a "thin" pine core with ash or maple stingers for screw retention... that would make a quite light touring ski...

[bcohen5055]

I can't speak with any real certainty without having done this but I can imagine you will have no torsional stiffness and turning will be very interesting. Take your profile core and try to flex it in torsion. When you add the unidirectional carbon you will only be adding axial stiffness so the torsional rigidity should remain about the same as the core before hand. As mentioned above a triaxial or layered 45/45 weave would probably yield a much stiffer ski.

[twizzstyle]

What these guys said is spot on. You need the fibers at 45deg for torsional stiffness, otherwise they're going to ride really weird.

You also don't want 21oz CF, those would be some STIFF skis. You'd want to get a weight of fiber that has a similar stiffness to 21oz fiberglass. You'd have to work that out yourself.

[mikic1]

I did build pure carbon kiteboards, which get quite similar to ski in layup, materials etc.

I have been using 22oz glass, and for the same core profile I have used 15oz triaxial CF (no glass) with excellent results. I think you can even go lower down, dont go higher, or make the core bit (up to 10% thinner).

You can save approx. 20-25% weight using carbon, however carbon does need more epoxy then glass, remember that. So mix 20% more pr weight then for glass.

Also carbon will give you very high stiffness. Approx 3 times more then glass.

Carbon is roughly 10-15 more expensive then glass.

Also, be careful, carbon is brittle, so the finished product might not be able to take impact same way. Carbon can stretch 1.5% vs 4-5% for glass before failure.

Anyway, if you want pure carbon, use triaxial 15oz as a start, symmetrical layup top and bottom, do few simulations vs glass with some of the code you can find here on the forum.

Cheers,

[mikic1]

PS: reg. the kiteboard, the carbon one is much stiffer then the glass one, just so you dont expect same results, however it was the idea in my case to increase the stiffness.

[Jekul]

I've built a pure CF snowboard (but I ski, so I gave it to my nephew). I did use 45/45/0 triax cf. I used an all poplar core, but it turned out with a decent flex pattern.

I know CoSurfer builds most of his boards using only CF and a unique box-wrapped core. Look around on the posts, I know he was writing about it last year.

[twizzstyle]

Also carbon will give you very high stiffness. Approx 3 times more then glass.

You can't be quite that general without more information. For the same thickness of core?

[MontuckyMadman]

If you are going all carbon to increase toughness and resistance to failure look at toughenrs like rubber additive carbon black and nanotubes.

[Sonny]

Thanks for all your help and input. It is very much approciated!

I going to do some testing to see what kind of results we get from this.

As for powder skis, does to torsional stiffness really matter that much? I'm not sure if a can pinpoint that feeling of a to stiff/soft torsional performance.

Also, I know the poplar core can flex A LOT without breaking, does the carbon's much higher strength, and less stretch before breaking mean that the skis can actually fail sooner then glass skis?

My last pair of skis were 194cm, with 130mm waist.
Core was 2,5-11-2,5 with 22oz triaxial FG over and under.
They are much softer then I would have wanted so more stiffness is part of the goal here..

What kind of results would you guys expect/guess from replacing glass with 21oz (uni direc) carbon? Maybe make the core thinner if the first pair come out to stiff..

[bcohen5055]

I don't have an answer for your question about the stiffness of a powder ski but I'm sure some of the other more experienced ski builders can answer that.

In regard to the poplar core, the carbon will stiffen it, this is the same thing that happens when you laminate it with fiberglass. The carbon fiber has a higher specific modulus than fiberglass though. This means that for the same mass, weave, and matrix mixture %, the carbon fiber is stiffer. This is the reason why people use carbon fiber; with a few calculations and some trial and error they can decrease the mass and retain the same stiffness, or create a stiffer ski with the same mass.

So will the ski fail sooner? This depends on what type of failure you are talking about but generally speaking it will take more force to deflect the ski the same amount if you replace 22oz triax glass with 22oz triax carbon. This means that by observation it will appear the carbon ski is weaker (it fails with less deformation) but in reality the specific tensile yield strength of carbon is much higher so if both the carbon ski and fiberglass skis were to fail the carbon one would take about 3x the load before failure.

Now in your example you are replacing 22oz triax fiberglass with 21oz uni carbon. The results I'd expect from this is a ski that more stiff in axial loading (not usually a concern for ski design) and much less stiff in torsional and bending loading conditions (The ones that matter). You can tune all these chericteristics with different core profiles but I'd imagine that you would have a much higher weight penalty modifying the core compared with modifying the glass.


*Disclaimer I haven't built any skis yet, this is just what I'm thinking. The best thing to do is experiment and let us know the results.

[sammer]

Nobody has mentioned the fact that 22oz triax is only about 12oz in the 0 deg. If you substitute it with 21oz uni carbon it will be ridiculously stiff longitudinally.

http://www.vectorply.com/pdf/etlx2200.pdf

or

http://pdf.nauticexpo.com/pdf/vetrotex- ... 75-_2.html

sam

[Sonny]

I don't have an answer for your question about the stiffness of a powder ski but I'm sure some of the other more experienced ski builders can answer that.

In regard to the poplar core, the carbon will stiffen it, this is the same thing that happens when you laminate it with fiberglass. The carbon fiber has a higher specific modulus than fiberglass though. This means that for the same mass, weave, and matrix mixture %, the carbon fiber is stiffer. This is the reason why people use carbon fiber; with a few calculations and some trial and error they can decrease the mass and retain the same stiffness, or create a stiffer ski with the same mass.

So will the ski fail sooner? This depends on what type of failure you are talking about but generally speaking it will take more force to deflect the ski the same amount if you replace 22oz triax glass with 22oz triax carbon. This means that by observation it will appear the carbon ski is weaker (it fails with less deformation) but in reality the specific tensile yield strength of carbon is much higher so if both the carbon ski and fiberglass skis were to fail the carbon one would take about 3x the load before failure.

Now in your example you are replacing 22oz triax fiberglass with 21oz uni carbon. The results I'd expect from this is a ski that more stiff in axial loading (not usually a concern for ski design) and much less stiff in torsional and bending loading conditions (The ones that matter). You can tune all these chericteristics with different core profiles but I'd imagine that you would have a much higher weight penalty modifying the core compared with modifying the glass.


*Disclaimer I haven't built any skis yet, this is just what I'm thinking. The best thing to do is experiment and let us know the results.

Thank you for your input i really appriciate this

I'll be sure to update on how this project develops.

[MontuckyMadman]

I used a 12oz biax 45/45 glass and a 9oz uni carbon with my thin core profile.
Substituting ash or maple for poplar in stringers will increase both the 0 degree and torsional rigidity but only slightly increase weight.
An all poplar ski doesnt perform very well in my opinion.
You could make a 8.5mm core and then use 21oz uni carbon maybe but you will always need something on the other bias otherwise the ski wont really turn on any semi firm snow, it will be more like a shovel than a ski most likely.
You want the ski to retain the shape when torsionaly flexed not give and deform and deflect across the ski and make new shapes.

[Sonny]

I used a 12oz biax 45/45 glass and a 9oz uni carbon with my thin core profile.
Substituting ash or maple for poplar in stringers will increase both the 0 degree and torsional rigidity but only slightly increase weight.
An all poplar ski doesnt perform very well in my opinion.
You could make a 8.5mm core and then use 21oz uni carbon maybe but you will always need something on the other bias otherwise the ski wont really turn on any semi firm snow, it will be more like a shovel than a ski most likely.
You want the ski to retain the shape when torsionaly flexed not give and deform and deflect across the ski and make new shapes.

Thanks for convincing me that's maybe not the best idea..

New direction!
450g/16oz triax carbon incoming!

Maybe this will be better for ski building, i'm sooo ready to get started now, can't wait for the carbon to arrive!