Official Luthiers Forum!

I think that's an oxymoron when it comes to guitars

And re: murrmac, I think Trevor and Gerard are the first to to such an in-depth mathematical analysis of guitar building, and the number of related posts is due to the book still being new. I'm pretty good at math, but even better at intuitive calculations. I understand the concept of young's modulus, cube rule of stiffness, etc., so I use that in my decision making process, but in the end it's my fingers and ears that tell me when to stop. The range of stiffness we work in is so "human", it seems like a waste of a joyful process to make it all technical

For your instrument (11" lower bout, 15" body length, spruce, steel strings), I'd estimate 2mm + or - a bit would be good. Depends on the particular piece, as well as the exact string tension you're planning, and string height at bridge, and bracing style...

Todd, I've just closed a box, what should the top compliance look (or feel) like, can it be described?

_________________
We are all in the gutter but some of us are looking at guitars.

I fine tune the closed box on every guitar by thinning the edges of the lower bout with an air sander. After a number of guitars I am getting better at knowing when it's right by the tap tone and vibration. The binding is not on yet so you can see the thickness. I seldom go less than .090 on an OM, maybe .085 on a size 2. It's a big part of my voicing process.

I got this idea from Dana's voicing article (http://www.pantheonguitars.com/voicing.htm) and from a young man that graduated from the Red Wing MN program. He spent a summer in my shop and Dana had come to the school for several lectures and demonstrations of voicing techniques. I learned a lot from him.

I feel like I hear the top kind of "open up" at some point. That's usually where I stop. The feedback vibration under your finger as you tap is helpful as mentioned in the article and by Todd.

I've always wondered if wide top purfling like herringbone or abalone does something as you are essentially removing a significant portion of the top/lining gluing surface and replacing it with something else. When I thin the edges of a top I only use one 0.060 strip of purfling.

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

[quote="Todd Stock"] I look for sensible movement out to the rim, along with consistency in the lower bout area, and thin to achieve it. Very seldom do I find myself doing anything on the bracing.quote]

Thanksfor the description, Todd. That sensible movement is the factor that I'm not sure about.
Do you, like Terence, thin the top to gain consistancy? If you need to thing the braces whats the best way of doing it through the soundhole. I tried, as you, just for grins, with a chisel but it very awkward to get a clean cut.

_________________
We are all in the gutter but some of us are looking at guitars.