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Erik,
As far as the properties I measure it was just the MoE and Density of the wood.
Simple deflection testing and a gram scale. I measure the tops in 2 axes but I only check my braces along the grain.

_________________
Jim Watts
http://jameswattsguitars.com

So the modeling doesn';t take into consideration that the top wood is much stiffer in one direction over the other?

And why are the strings pulling down into the top? Is that just part of the drawing, or is that where the actual string pull direction is modeled?


Interesting stuff, but before weighing-in too seriously, we need to establish some basics as to how it was modeled.

[QUOTE=Jim_W]I measure the tops in 2 axes...[/QUOTE]



Grumpy, the two axes must be along the grain and across the grain.

Okee...

Yeah, you'll see squat without some vertical exaggeration in the
plotting routine, the real info is in the numbers (colored
contours).  We geophysicists do this with topography all the
time.  That's why the area around the bridge looks so deformed.

The arrows in the image show the load application points. It looks like he modeled the strings as solids just for effect, but they do look misleading as part of the deformed shape (since the deformation is exaggerated many times). If he had applied the force directly to the string ends, then they would have stayed in line. The bridge and top would still deform exactly as they have, which I think is at the heart of what he was hoping to achieve.

For wood, you need the elastic moduli along the grain and perpindicular to the grain, as well as the shear moduli along both those axes. (Modulus = engineer speak for stiffness!) The shear modulus is really the shear stiffness; you need this in order to evaluate the reactions of the braces and the top under torque. Modern FEA is an incredible tool as long as it is verified with actual data - as he has done!

I'm waiting impatiently for a good modal analysis to come from this....

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http://www.PeakeGuitars.com

I didn't mean to abandon this, I just wasn't around much yesterday. The last few post were good answers.
Thanks Guys.

_________________
Jim Watts
http://jameswattsguitars.com