wood/carbon core matrix

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Gilo
Posts: 62
Joined: Sun Feb 03, 2013 7:36 am
Location: Somerset - the flatlands

wood/carbon core matrix

Post by Gilo »

Just got back from the French Alps and some good skiing with the kids - did some nice off piste at the beginning of the week but it crapped out thereafter.

Just thinking about a new build also - in particular core construction. In the past and as per I use a vertical laminates. I am currently considering an ash/spruce combo for my next skis. The lay up would be thus

base
15.5oz biax
3.5oz UD CF (full width)
Core (11mm)
3.5oz UD CF (full width)
15.5oz biax
fabric
Topsheet

So far so normal, although a critique of the lay up would be appreciated. I am hoping that the light biax glass would be offset by the carbon in terms of flex, torsional strength and pop etc.

This leads me to my question - have any of you ever tried interleaving the original core lay up with UD carbon between the strips of wood? so the core lay up would go (using epoxy to bond):

Ash
UD
Ash
UD
Spuce
UD
Ash
UD
Ash

That would then be sliced as normal to produce two planks for the cores. On a couple of my surfboards, the central stringer has a line of carbon down each and it is just an extension of this idea.

Any input greatly received - I have done a pretty thorough search but haven't been able to find anyone posting about this.

Happy NY everyone

Gilo
sammer
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Location: Fernie B.C.
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Post by sammer »

I did this on my last core, unfortunately it exploded on the finishing pass with the router.
I used 24k carbon tow between the wood.
It was very hard on the planer knives after planing the rough cores down (to the proper thickness to start with the router) the new knives were gouged and tearing the wood.
The router bit, which was fairly new when I started, was also pretty dull by the end.
This may have been the reason for the failure of the core.

I don't think you have to have a carbon stringer between each layer of wood.
You already have a fair bit of it in your layup.

sam
You don't even have a legit signature, nothing to reveal who you are and what you do...

Best of luck to you. (uneva)
twizzstyle
Posts: 2204
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Location: Kenmore, Wa USA

Post by twizzstyle »

It's a waste of CF. The layers of CF towards the middle of the core will not be adding any stiffness at all. The CF layers by themselves have very little bending stiffness, you get the stiffness by placing them far from the center of the core so that as it flexes, the CF is put in tension. You get the stiffness by pulling on the CF - same goes for fiberglass. The further away from the center of the core, the stiffer it will become (that's why thicker cores give stiffer skis)
ben_mtl
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Post by ben_mtl »

what Twizz says... It would be as effective and cheaper (probably heavier though) to put 1/4in strips of a stiffer wood while you make your core... would it really show ? not even sure !
I use a mix of poplar (good weight) and maple or ash (for strength) on my cores, I'm very satisfied... to adjust the stiffness I play with the amount of UD carbon fiber on top and bottom... (the bottom UD carbon has more influence on the stiffness while skiing.. but symetrical layup is a must IMO !)
A bad day skiing is always better than a good one at work...
twizzstyle
Posts: 2204
Joined: Tue Mar 07, 2006 8:25 pm
Location: Kenmore, Wa USA

Post by twizzstyle »

Another option, rather than laminating wood/CF in a horizontal laminate, is to do a normal vertical laminate of wood, but put a layer of CF oriented at +/- 45 deg between each piece of wood. The CF acts as a shear web, just like an I-beam. Would be VERY difficult working with biax CF cut that way though, it'll just want to fall apart...
Gilo
Posts: 62
Joined: Sun Feb 03, 2013 7:36 am
Location: Somerset - the flatlands

Post by Gilo »

Thanks for the input chaps - I think that this is one of those ideas I won't be following up on.

Gilo
FlamingYeti
Posts: 45
Joined: Tue Sep 25, 2012 5:46 pm
Location: Park City, UT

Post by FlamingYeti »

A while ago, we did this idea of vertical laminates between the core stringers and it worked out fairly well. For the process, we essentially did a pre-cure of the carbon. We put 12 K triax Carbon in the press with some epoxy and just cured a big sheet of it, then cut it up on the table saw and laminated it between the core stringers. Profiled it on the router and added some more triax horizontally laminated and it worked out pretty well.
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