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Hello,

I’ve been testing a few sets of torrefied Sitka from SM using the plate thickness formula from the Gore book.

The formula is spitting out thicknesses in the less than 0.090 range (as low as 0.086) which is very thin for top wood. I’m assuming the lightweight nature of the torrefied wood is throwing things off. Anyone have experience with using torrefied wood and following the book recommendations? Should any of the variables be tweaked if the wood is torrefied?

Brad


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Torrefied shmorrefied, material properties should be whatever they actually are, quantifiable.

It could be that the wood you have is particularly dense/stiff. What is the density?

While I agree that the material properties are what they are, the formula that takes that as input and spits out a thickness is derived, at least at some level, from the experience of it's creator. Is that not correct? Don't get me wrong, I have about half understanding of 20% of the majority of this topic.

I took the recordings again from a set that first indicated 0.93. It's now recommending 0.103. So perhaps I need to retake recordings on the others as well. The mic setup I have here is finicky.

Here is an example.


Wow, was fighting with the image attachment for a while, but I think this is the right resolution now.

Brad

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Looks good to me. Once you get consistent and easily readable freq. responses the rest is pretty straight forward.
I didn't run the math but at a glance everything looks good, even the .103. 'Bout where mine are.
Ken

Mine aren't terrified tho.
It is very important to get those freq. readings accurate.

Thanks, Ken. I was thrown for a loop with the really low thicknesses I was getting in the spreadsheet. I’ll retake them all again to see if they are consistent. I really need to get a decent USB mic that I can go right into my laptop with. The mixer in my setup now is wonky.


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2.62 mm is what most of my spruce SS tops come out to be. So sounds good to me!

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First, decide which answer is right. If it is the 2.62mm number, that is a fairly normal number, as others have mentioned, and matches what I get using your input data.

It appears to be a low stiffness, low density sample, so will likely make a low mass top (relatively speaking) and should suit a 000 style guitar.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

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Please check your oscillation frequency formulas. You have different numbers listed as variables and as SI system. These are Hertz and should be the same in SI system as measured. Or am I getting this wrong?