Official Luthiers Forum!

Can anyone give me, or direct me to a website which will give me, a formula for calculating long grain Modulus of Elasticity from deflection testing, preferably in metric units?
I've spent a fair bit of time looking and have turned up nothing, although I'm sure I've seen it before somewhere.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Design P1-24 or P4-39/40.

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

http://www.goreguitars.com.au

Got it, thanks and
The volume was actually at my elbow as I read your post, I'd looked it out to search.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

You got that? I didn't

The P's and Q's that is.

I just started deflection testing too and tried searching as well for others methods and so on. I finally came to the conclusion that it's a big secret and you have to figure it all out yourself. So I have a brick with cork glued to it, a dial caliper, some blocks to raise the top up on and just add the weight, repeat 3 times, take the average, and record it. I guess after about 20 more guitars I will have a personal data set that will start to provide results.

Page references for the book. A lot easier than trying to write out math formulae on a text-based forum.


No need to re-invent the wheel. According to Charles Fox (referring to the book) "This is exactly what you want, and you can begin wielding this valuable knowledge almost immediately instead of waiting a lifetime to attain it."

Thank you Charles!

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

http://www.goreguitars.com.au

Oh I see! Yes, been meaning to get the books for some time now. My problem is I buy books, shelf them, and never read them. That or I spend all my money on wood

Holiday weekend coming up might give me time to finally sit down and finish the Somogyi books and then move on...

Looks like it's out of stock? Is there a digital version?

It's not really the sort of book that lends itself to digital. I'm currently proofing the 2nd edition pre-prints from the printer. Should be back in stock toward the end of August, if all goes to plan.

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

http://www.goreguitars.com.au

Trevor, will there be significant differences between the 1st and 2nd editions?

+1

Also very interested to know.

Probably greater than 98% the same. I've changed out a few of the "free standing" photos for better/more interesting ones; the photos in Build are all a little bit larger and better colour balanced; there's a bit more on intonation/compensation, there's a better double-acting truss rod. There's minor changes to some of the equations so that they are easier to check (there was a residual error of ~0.5% (iirc) that was driving people mad when trying to check their calcs, but of no consequence in real life). There's the new foreword by Charles Fox (referred to above) and a commendation by Tommy Emmanuel. Otherwise, it was about correcting typos and re-wording a few explanations to help reduce the possibility of any ambiguity. So if you already have Edition 1, I wouldn't be rushing out to update to Edition 2, unless you have plenty of spare cash that you want to throw in my direction!

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

http://www.goreguitars.com.au

Trevor, are you going to have the updates online for those of us that have the first edition?

Bob

Bob, quite a lot up of updates came as a consequence of discussions in "the book" section of the ANZ Luthiers Forum. So in a sense many of the updates are already on line.

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

http://www.goreguitars.com.au

Are they complied in one thread?

They are all in one sub-forum. Just follow the link above.

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

http://www.goreguitars.com.au

Thank you Trevor!