woodcore thickness

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mowgli1996
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woodcore thickness

Post by mowgli1996 » Wed Mar 27, 2019 4:09 pm

hi!

looking on the internet i have not found specific studies on the thickness of woodcore, which is critical to performance!!
I read that it must be between 8 and 12 mm, but I would like to know more specifically how to calculate the most suitable thickness for different types of skis, and how this value affects performance!
and also how it varies depending on the insertion of extra layers of carbon or titanal.

so I would be grateful if someone could help me with advice, experiences or material to study

thank you in advance.

Michele

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vinman
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Re: woodcore thickness

Post by vinman » Wed Mar 27, 2019 5:05 pm

The thickness of your core will determine a large portion of the flex characteristics of your ski. In general a ski core should be no less than 9.5mm thick. This is so that it can accommodate adult binding screws which are 9.5mm long. Anything less than this and you run the risk of drilling thru your ski when mounting. For a kids ski you can go thinner, down to 7.5mm due to shorter binding screws on youth bindings as well as the shorter length of kids skis.

a core 9.5mm thick at the waist would generally equate to a very soft flexing ski, unless that ski is very short. I typically start with a ski core that is around 10.8mm which with a flat area for mounting. The length of this mount are will also have some impact on how stiff/soft your ski is. The longer this is the more stiffness it will add to your flex profile.

Don't forget that length has a huge impact on stiffness. The shorter your ski the thinner your core profile will need to be so that your ski does not end up too stiff.

A decent start point for a ski around 180cm would be a core thickness of 10.8-11.1mm at the waist tapering down to 2.2mm at the tip and tails. 2.2mm is equal to the thickness of the tip/tail spacer material) This would give you a medium to medium-stiff ski depending on the length of the mounting zone and how you chose to taper your cores down to your tip and tail thickness. How you chose to do this varies widely.

Do some searching and reading about core thickness on the forum, there is a wealth of knowledge here.
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chrismp
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Re: woodcore thickness

Post by chrismp » Thu Mar 28, 2019 1:45 am

You will probably not find any study that gives a comprehensive overview on this topic as it is way too complex. Stiffness of a ski is affected by many factors (e.g. core thickness, reinforcement layers, length and width, etc.) that all work together as a system. Even for big manufacturers that have access to FEM analysis software, a huge part of developing a ski is going through a bunch of prototypes to get the flex right. A famous Austrian ski racer is said to have gone through about 100 different prototypes for his ski until he settled on a few models he would like to race.

skidesmond
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Re: woodcore thickness

Post by skidesmond » Fri Mar 29, 2019 11:51 am

you can use this spreadsheet that somebody created awhile ago. Its a great help. But I found that it only gives a good starting point because the numbers it gives you wont have a lot of meaning until you make the ski and ski on it. Then the numbers will have meaning because you'll have experience on that ski with a set of numbers from the spreadsheet. Then the fun begins.

http://www.mediafire.com/file/w2zhdmuzk ... mmsexe.xls

NicolaL6
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Re: woodcore thickness

Post by NicolaL6 » Sun Apr 21, 2019 9:46 am

Wow thank you very much! I'm planning to compare other ski stiffness to make an idea, doing some fem calculations and build and test che models on torsional and bending stiffness,
This thread come in help to some of what I need for the core!

Vostok61
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Re: woodcore thickness

Post by Vostok61 » Fri Apr 26, 2019 12:12 pm

Well thanks for that, it's awesome! I've started designing skis as a hobby and thought it'd be easier; it isn't, but it just makes it more interesting.
So far, my prototypes have had terrible flexibility, but hey, they'll work perfectly as sled parts in winter, or in the worst case scenario, as fence pickets :D

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