Tuesday, April 19, 2011

Core ready to add veneer

So after 48hr of curing !! the rails are finally set in place and the core is ready to add the balsa veneer.
Already the board is feeling more like a board than this time last board. Things actually fit nicely!

There is still overflow epoxy/qcell on the foam which I am going to thin back and rough up to make sure when the veneer goes on it will have a grippy surface to attach to. After having to wait 48 hours for this slow curing epoxy to harden I'm definitely going to be investing in some quick curing resin to put the veneer on.

With the tapered tips on the board my estimate is that the tips are going to be around 20% stiffer than the last board which had a step profile. So ideally I'd like to do what I can avoid the veneer contributing to any further stiffness of the tips. While the elastic modulus of balsa is much greater than Klegecell ( 1.5-2 GPa vs 30 MPa) it is still an order of magnitude smaller than that of the laminate which as near as I can find out is likely to be around 15-20GPa)  So this means that the veneers contribution to the board strength and stiffness still primarily derives from the core thickness it adds (stiffness being proportional to core thickness cubed: 10% increase in thickness - > 30% increase in flexural rigidity).

Why am I bollocking on about this. Well I'm trying to figure out whether I need to be concerned about where the joins are in the veneer. If the balsa was adding significantly to the strength through its intrinsic properties then having all all the balsa planks aligned at the short end would introduce a 'fault' line because the grain will be discontinuous. However, this is not the case and so I'm thinking that it doesn't matter and that what I should do is just do whatever looks good.

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