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Cork for core ?

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dimitrisGramma
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Cork for core ?

Postby dimitrisGramma » Thu Jun 18, 2009 12:00 pm

Hi,

I need to know your opinions and advices on using cork for core (perhaps two laminated sheets).

Thank you in advance!

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zob
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Re: Cork for core ?

Postby zob » Thu Jun 18, 2009 1:30 pm

This is not so bad idea at all! :thumb:

zfennell
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Re: Cork for core ?

Postby zfennell » Thu Jun 18, 2009 1:55 pm

not sure exactly what you have in mind but ....opinion only.
i think the density will be a bit heavier than balsa (sg=.15-.2)
i also think cork is similar to bark veneer,
meaning pretty good compressive strength (150psi) and poor tensile and poor flexure strength

so a core filled with cork used only for its compressive and shear properties (all flexure strength provided by glass laminate) will be heavier than using eps or xps foam.

and comparable weight to a balsa end grain core.

but i dont think it can compete with balsa, cedar or pawlonia planks (long. grain) that will provide a lot of plexural strength.
and its not much stronger than cheap/light styrene core materials
( again, opinion clouded by total lack of any facts)


perhaps thin sandwich applications over a lighter core of something else.

but wood always looks good.

-regards,
bill

zfennell
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Re: Cork for core ?

Postby zfennell » Thu Jun 18, 2009 1:59 pm

someone posted this a long time ago.
the link is dead but i saved the attachment

material properties of various woods:
(download attachment)

also material properties for structural foam cores
http://boatdesign.net/articles/foam-cor ... /index.htm
Attachments
wood.xls
(55.5 KiB) Downloaded 131 times

dimitrisGramma
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Re: Cork for core ?

Postby dimitrisGramma » Thu Jun 18, 2009 2:33 pm

zfennell wrote:someone posted this a long time ago.
the link is dead but i saved the attachment

material properties of various woods:
(download attachment)

also material properties for structural foam cores
http://boatdesign.net/articles/foam-cor ... /index.htm


Thank you!
This seems like excellent information. However, where could I read for the definitions of all these coefficients since my knowledge on materials mechanics is not so extended?

zfennell
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Re: Cork for core ?

Postby zfennell » Thu Jun 18, 2009 8:50 pm

the application of the terms may be more involved than you wish.
but here is a good place to start.
http://physics.uwstout.edu/Statstr/Stat ... Forces%20I

generic google search for:
-bending stress in simply supported beam
-design stress sandwich construction

if you're still interested keep asking questions.
in the meantime, copying existing layups will be extremely educational.

regards,
-bill

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Re: Cork for core ?

Postby Nico » Sat Jun 20, 2009 4:52 am

Hi.
I,ve used cork on a board, but not for the core, I used it for pads and works great.
I believe you flex factor will also not be right and you will have to compensate with extra layers of glass or wahtever you intend using.
Nico

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Re: Cork for core ?

Postby BWD » Sat Jun 20, 2009 4:59 am

cork for some parts of core, not all the core is cork, ok, a thin layer, maybe in some places....

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Pablo
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Re: Cork for core ?

Postby Pablo » Sat Jun 20, 2009 6:31 am

hi
found this great link explaining the role of the core
http://www.oneoceankayaks.com/Sandcore.htm
IMO the cork shear modulus is too low (see the pic "layers slide past each other" in the link)

besides cork seems to have a really low E ( elasticity modulus, is too flexible). the compression side might buckle under heavy load. But I'm just guessing, it'd be easier with actual numbers.

still, i'd give it a try on the "flextips" that many boards have nowadays.

pablo

dimitrisGramma
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Naish Haze 2008 135x44, Custom Carbon board 138x42
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Re: Cork for core ?

Postby dimitrisGramma » Mon Jun 22, 2009 10:43 am

Thank you all for this valuable information! :D


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