Layup questions

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Hannes
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Layup questions

Post by Hannes »

After spending some time now with the simulator of junksupply.com I am wondering how changes in the layup affect the ski.

1. I made a ski with 750g triax glass. It is a bit on the soft side. But I think 1150g glass might be too stiff. So I want to try an asymetrical layup with 750g and 1150g. Will there be a difference if the 750 triax is under the core and the 1150 on top or vice versa?

2. Does anyone have experience in combining glas with carbon? I am thinking about using glas biax and carbon uni with the biax next to the core since I heard that this might improve the durability of the ski.
I could also use carbon triax but don´t want the ski to get to much pop.

Thank you!
Hannes
mammuth
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Post by mammuth »

Regarding the glass only versions: Make the core thicker instead of putting so much fibre. Asym layup can cause problems (concave/convex base .. more likely the wider the ski is) and it will propably change your camber. Beside this it will be more heavy then the thicker core version.

Biax on the core and uni on top is better is generally better if you use more layers.
Tom
Hannes
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Post by Hannes »

I am using Super Sap and the skis are curing just a bit above roomtemperature. Do the problems with convex/concave base occur under these circumstances?
mammuth
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Post by mammuth »

Dont know. But more glass needs more resin so it cures slower ... maybe this is part of the asym layup problems.
Tom
mammuth
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Post by mammuth »

put some carbon strings ... there are lots of topics covering this
Tom
Hannes
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Post by Hannes »

I was already considering this. But I am afraid that I get something like "rails" into the base because of the volume of the carbon.
gav wa
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Post by gav wa »

You wont notice any rails in your base from the carbon.
You will definitely effect the camber with asymmetric layup. Its hard to get right.
Heated cure will give you a stiffer ski. Is super sap even designed for room temp cure?
gav wa
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Post by gav wa »

Why dont you just leave your core 0.5mm thicker? That will stiffen the end product.
Hannes
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Post by Hannes »

I made two pairs during the last few weeks. One .5mm thick than my standard core and 10mm wider using 750g Triax Glas. Flex ist just like I wanted it. Great in groomers but couldn't test it in powder yet.
The next pair got my standard core combined with 300g biax carbon and 400g uni glass. Hasn't seen powder as well but the best ski in groomers I made so gar and I think it will be great for touring. Nice edgehold die to the stiff torsion.

Thanks for your advices!
satch
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Post by satch »

Pics or it didn't happen!!!
I know I'm a bit lazy in that area myself, but it would be great if you posted some photos and wrote a Little bit about your skis.
Thanks in advance!
Gilo
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Location: Somerset - the flatlands

Post by Gilo »

Interesting re-reading this thread and comparing it to some of my experiences and what I have been advised:

I was told to put the carbon next to the wood in my layups - I never questioned the wisdom but it seems to work fine.

I use biax glass and uni CF (250gm)in my normal lay up. I have 2 cores as "standard" an 11mm and a 12mm. In order to further vary the flex I will swap to 100gm on top to soften the ski. I have not had any problems with base flatness nor have I experienced any issues with loss/gain of camber.

Someone said that glass needs more resin to wet out - I have found quite the opposite.

I vacuum press my skis and top heat only. They remain under full pressure for 12 hours and are the allowed to cool for a further 24 hrs in the mould under no pressure or heat. I then demould and deflash.

My workshop is not heated and all resins, fibres and wood are worked with at ambient - it is chuffing cold sometimes.

Gilo
Hannes
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Post by Hannes »

SleepingAwake
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Post by SleepingAwake »

Gilo wrote:I was told to put the carbon next to the wood in my layups - I never questioned the wisdom but it seems to work fine.
I would always use a thin polyester or glass fleece inbetween carbon and the core as a tough transition layer.

To avoid big shear stresses at the interface between different layers you want the smoothest transition in stiffness possible. So if you have a very stiff UD carbon in contact with the low modulus wood this just asks for delamination problems.
For this reason i always put the biax layer in contact with the core followed by the UD layer.
Gilo
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Post by Gilo »

Sleeping - thank you for the tip - I shall change the way I do my lay ups. I had never questioned why, just done as I was advised. Your explanation makes perfect sense.

Going to lay up a pair this morning.

Thanks

Gilo
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