Kevlar

gketcham · Post by **gketcham** » Fri Sep 16, 2011 3:23 pm

Has anyone used a whole ski length/ width sheet of Kevlar? In place of Carbon or Fiberglass?

mattman · Post by **mattman** » Fri Sep 16, 2011 5:14 pm

I am sure it has been done...in fact we have used triaxial kevlar for airfoil parts (available from Raka). However, I wouldnt recommend it for skis for a couple reasons. It would provide core-shot protection (but this can be done with a small 5oz strip and doesnt need to replace any structural layers)...but for a full size glass-replacement layer the kevlar will be a NIGHTMARE to trim after the ski is pressed (cant emphasize this enough). Second, kevlar has a tendency to creep...so retaining camber would probably be short lived (could also affect the consistency of the flex). We played around with this idea before and decided against it because of the many downsides. Plus, the core-shot protection isnt really as grand as it seems...kevlar doesnt stop a bullet, it "catches" it. For skis this means, your core would still be dented, you just couldnt see it because the kevlar would still be intact.

twizzstyle · Post by **twizzstyle** » Fri Sep 16, 2011 6:13 pm

Another vote here for "Kevlar sucks to cut". I used it a lot in school on airplane stuff and I always hated working with it. The real benefit of Kevlar is it's impact and damage resistance, but in a ski where you're looking for stiffness, carbon is reall the most efficient, and fiberglass is dirt cheap.

COsurfer · Post by **COsurfer** » Fri Sep 16, 2011 6:35 pm

I tested some samples using kevlar to replace the bottom layer of fiberglass. I used 10 oz biax kevlar because that is the thickest I could find. Under compression it failed when fiberglass didn't at the same weight. I never used in it a layup because I don't think it provides any benefit.

Richuk · Post by **Richuk** » Sat Sep 17, 2011 1:33 am

There is/was a french co-op video kicking around the forum - they use it in their lay up. Used next to CF, if I remember rightly. Maybe this is the reason: http://digital.library.okstate.edu/OAS/ ... 98_101.pdf

Would like to know more about the experience of creep - can only find issues expressed in terms of constant load.

bobbyrobie · Post by **bobbyrobie** » Mon Sep 19, 2011 6:51 am

Kevlar also like to absorb moisture too.

Richuk · Post by **Richuk** » Tue Sep 20, 2011 4:42 am

Put it in the airing cupboard overnight before use. Use elevated temperatures when wetting out the fibre and keep the fibre within the boundaries of the ski/board.

Kevlar can be used, but like Twizz has stated, not really a replacement for GF or CF.

gketcham · Post by **gketcham** » Mon Oct 24, 2011 1:21 am

Thanks for the input. For added strength then, more glass and carbon would be the trick instead of 1 layer of Kevlar. What about the Fiberglass w/ kevlar stringers that "snowboardmaterials.com" sells. That would add strength without the hassle to cut and deal with, right?

twizzstyle · Post by **twizzstyle** » Mon Oct 24, 2011 7:14 am

gketcham wrote:Thanks for the input. For added strength then, more glass and carbon would be the trick instead of 1 layer of Kevlar. What about the Fiberglass w/ kevlar stringers that "snowboardmaterials.com" sells. That would add strength without the hassle to cut and deal with, right?

I still think it's a waste. If you want to add stiffness go with the fiberglass with CF stringers, the cost is nearly the same.

Also - for what its worth, I made two pairs of identical skis last year, one with just triax fiberglass wet layup (19oz), and the other using the precured fiberglass sheets with carbon stringers from SBM. The skis with the precured sheets were much stiffer, but were also heavier. I think a wet layup with 19oz triax and some added uni CF would be as stiff as the precured stuff, but lighter.

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