Idea for a layup, involving carbon and aramid

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twizzstyle
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Post by twizzstyle » Tue May 07, 2013 6:22 am

arild wrote: And I wasn´t planning on making my first build a $400 venture into exotic fibres. Even I am not that silly.
I was when I made my first pair of skis some 10 years ago or so :( Needless to say, I had no idea what I was doing with the rest of the process, and they were unskiable. But I learned a ton!

arild
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Post by arild » Thu May 09, 2013 6:01 am

twizzstyle wrote:
arild wrote: And I wasn´t planning on making my first build a $400 venture into exotic fibres. Even I am not that silly.
I was when I made my first pair of skis some 10 years ago or so :( Needless to say, I had no idea what I was doing with the rest of the process, and they were unskiable. But I learned a ton!
Thank you for that admission! I have no doubt my first pair will be wall art, but that´s OK.

How elastic is regular 22oz triax? I read in one of the links of the first reply that aramid/kevlar has a 4-5% stretching limit, curious as to how I can replicate that with glass, possibly VDS in strategic places?

Thank you for all your help, everyone. Can´t wait to show you how I progress (or more likely, regress).. :)

twizzstyle
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Post by twizzstyle » Thu May 09, 2013 6:13 am

Why do you want an elastic ski?

arild
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Post by arild » Thu May 09, 2013 8:08 am

Not the ski itself, rather the fibers' properties of stretching before breaking. I may have interpreted those data figures wrong,though.. :)

Richuk
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Post by Richuk » Fri May 10, 2013 8:06 am

Compare fabrics in terms of tensile and compressive strength and modulus.

Ignore the rest for the time being.

24Dave
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Post by 24Dave » Tue Jul 02, 2013 8:43 am

I have made boards with kevlar on the bottom, it is hard to get a good finish if the fibers go out to the edge of the board. Best approach is to soak fuzzy sanded kevlar ends with super glue, then cut with a razor blade using a sawing motion, not just pushing the blade.

The unique thing about kevlar and similar fibers is that they resist tearing and shattering, but, I don't see why we should use kevlar or aramid on the base of a ski or board because:

any rock damage that goes into the wood core is so easy to fill in and fix with a little epoxy, its the ptex that is a shame to damage and takes more time to get right. I guess if you tore across your base diagonally and ripped your bottom fibers apart, one could say that kevlar would have prevented compromising the fibers on the base, but a ski or board should probably be laid to rest after a hit that would do that.

If you are using superlight, softer woods a little kevlar won't prevent base/sidewall compression from pounding into rock either. It seems to me that base hardness comes from wood type and perhaps the amount of resin soaked into the wood, unless you really stacked up a lot fiber.

Fiberglass is cheap, stretches to allow a lot of flex and absorption of terrain, carbon is pretty cheap too, easy to work with and adds a lot of stiffness, I don't think fancier fibers give you much more in a ski or snowboard that has a layer of ptex and a steel edge that can be easily damaged right there on the base

Richuk
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Post by Richuk » Fri Jul 05, 2013 1:31 pm

The size of the damage due to impact should be reduced when using aramid fiber. If weight reduction is the issue, then Aramid fibers demand too much resin, adding weight.

The only reason to use a certain amount of Aramid in a layup is vibration dampening.

PTTR
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Post by PTTR » Tue Aug 06, 2013 12:01 pm

Vinman wrote:Couldn't agree more with Sam and Twizz. Way stiff, way, heavy, way expensive. Get your process down then get fancy.

I have now made 19 pair. I'm just getting to the point that I'm willing to take a chance on exotic material experiments.

I'm going to try for a lightweight ski this season. Basswood core with maple finger jointed under the binding screws, 6mm ash perimeter stringer. 17oz biax glass with 7oz uni carbon. Shooting for under 4 lbs per ski on a 183 cm ski and 107 underfoot. This will be a touring ski mostly.
I have buildt two pairs with abachi and a mix of harder materials under the foot with good results last season. Abachi is very light, 55% of the weight of my birch, and is often used for sauna benches because it does not get hot, my local wood supplier had it, maybe yours does to?

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