How low can you go? Or how to underbuild a guitar

[Herman]

Hi guys,

I just had a mail from Darren about his baritone-project. He gave me the idea to make build on the edge. All my guitars are still healthy after some years. Maybe I make them too heavy. Always followed the industrial standards. So this is the thought:

I'll make a guitar that is significant lighter than usual built.
Stiff material, 30% lighter braces, thinned top-perimeter, bolt-on neck, no glued fingerboard overhang, simple binding, cheap top. This with the possibility I will have to take off the top if things go bad.

Give me your thoughts, How low would you dare to go?

Herman

[Darryl Young]

Till the bridge rotates 3 deg under string tension. You could measure this and keep shaving braces till this occurs. A seperate issue is how thin to make the top. I think it starts affecting tone and purpose before it will loose stuctural integrity. In other words, at some point it won't be that great for strumming but may still be a good finger picking guitar.....and at some point it won't yet fail, but it will creep/belly over time and require a neck reset.

Did you see the spreadsheet on my Cuban Mahogany/Lutz post in the Blog-Your-Build section? You can measure the frequencies of your top, plug the numbers into the spreadsheet, and it calculates the Modulus of Elasticity etc. then calculates the top thickness. This is from Trevor Gore's new book and the values are for a fingerpicking guitar so this is as low as I would go. His emphasis is to not overbuild and to have a very responsive guitar. This might help you set your top thickness and then bridge rotation might help you set the brace height/stiffness.

Edit: BTW, Gore targets 2 deg of bridge rotation.

[Kevin Sjostrand]

I HATE it when it happens.
I made a post, clicked submit, and it must have gone into lu lu land.
And it was so profound at that.
Here it is again.

Herman,
That makes me think of an old Chubby Checker song, "Limbo Rock"........"how LOW can you GO?"


I say build it, it will be an experiment, and it may turn out really great.

Kevin

[Jim_H]

I'm actually doing some experimenting myself.

Nothing scientific (that stuff isn't fun!).

I have the makings of three dreads that I've collected over some time. Two are EIR, one generic Mahogany. I'm going to do some non-scientific experimentation with the two EIR guitars. They will be pretty much identical, except I intend to build one with a thin'ish top/heavier bracing, one with a thick'ish top and lighter bracing. I'll probably do something more to standard on the Mahogany machine.

Exactly what constitutes thick or thin, or heavy or light is still to be determined. It will be subjective on my part, with the decisions to be made while I'm standing at the thickness sander, feeling the stiffness.

I fully expect to maintain my very low standards for notes and documentation, and not write anything down. I also no doubt forget to take pictures too, all of which will make the entire process a ginormous waste of time. And with my memory, I'll probably forget which one is which!. :p... But that's fine, as long as I have fun along the way.. if I learn something, that's even better. >.<

[kencierp]

If at some point I ever get time or the inclination to build and sell guitars again -- my gimmick -- will be that the sound boards are constructed and pre-tested -- for responsiveness using the device outlined in Roger Siminoff first publication --- it's very doable and to me, makes perfect sense --- the idea indeed is to build as light as possible based on a small range of total string tension. The beauty is that you can decide what gauge strings you intend to use.

[tippie53]

I have seen great guitars that withstood the test of time with tops as thin as .070 and some that failed at .125. The point is that the top is a structure and the bracing needs to match the top.

[darren]

so would you start with .25" bracing or wider? if the strength is in the height of the brace, you'd start with skinny and tall, right?

[tippie53]

I never go under .250 My preference is .280 to .300

[kencierp]

The point is that the top is a structure and the bracing needs to match the top.

John I would say that we all agree on that concept -- the point however, is that Siminoff and Gore are of the opinion that the components can be matched. Siminoff based on mechanical testing and Gore has a range of dimensional metrics -- both guys it seems to me believe there is real guitar science as opposed to the sometimes mystical practices of guitar makers in general. I am actually way out of bounds making comments about Trevor Gore since I do not have his book -- I purchase all the publications on this subject so I will be getting it in the near future -- I do find some of his ideas interesting to say the least.

I like to start with 5/16" wide bracing and work down from there -- on smallerr body guitars "00" 1/4" is my normal.

[Darryl Young]

Ken, with your engineering background you would get a lot out of Trevor Gore's books. I finished the "Design" book but haven't yet read the "Build" book. It's a methodical, structured approach and he gives the reasoning behind his approach. In fact, the equations are derived just like a college text book for Engineering classes. Impressive piece of work.

Another topic he discusses is how we hear things. The initial transient (or attack) has a large influence on our perception of a sound. So the attack may give us the impression of loudness that may not actually be there.

One change I will make after reading the book is using solid (well, laminated) bindings to connect the top to the sides. Not as improtatnt for the back so I may go with regular or reverse kerf linings for the back. May toy with adding some mass on the perimeter as well (maybe add some weight to the tail block etc. and see how things change. This can be done on the finished box and it would be reversable so not a big risk.