Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Sat, 26 Apr 2003 14:44:02 -0400
Message-ID: <redirect-2148339@logan.com>
From: Newlan2dl@aol.com
Subject: Re: [LML] Re: Core for Structure in Compression
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Hi David

I'm having a hard time picturing what you are describing but do you know how 
many psi you are talking about in compression?  If you know that you can go 
to Diab-Barracuda to check the compressive strength of the cores for 
Divinycell.  If it's a concern, balsa will give you a pretty awesome amount 
of compressive strength and modulus.  You can also taylor the compressive 
strength  by varing the density of the balsa.  For very high loads, under 
bolted on fittings for example, I've switched from the common denities like 8 
lb/ cu. ft. to 12 lbs.  For low loads, I've used 4-5 lb density in balsa.  
This has a higher compressive strength than foam and outwardly is lighter in 
density but can sometimes end up weighing more due to resin absorbtion.  This 
can be largely mitigated by using AL600 coated balsa from Baltec which 
precoats the balsa to limit resin absorbtion.  Be aware however that if you 
sand the balsa, you will need to recoat the balsa with a "hot coat" to limit 
resin absorbtion later which can starve the interface and lead to poor 
adhesion.

For really high load stuff you can use end grain cedar (24 lb/cu ft) or fir 
(33 lb/cu ft) for core.  End grain will withstand compression MUCH better 
than grain running lengthwise since wood is like unidirectional composite.  
It is afterall a natural composite (cellulose reinforced lignin).

Dan Newland

Super ES