Top thickness on small guitars

[Gary Nutt]

I have built 3 rosewood body 12-fret 00 guitars (like a Martin 00-21) in the last few years. The first one had an Engelmann top, the second had a Sitka top, and the third had an Adirondack top. The thickness of each of the tops was (very close) to 0.100", and all had the same bracing pattern. The Engelmann top guitar sounded terrific, but the Sitka and Adirondack topped guitars sounded stiff (I think boxy might be the right description of the tone) with less bass (even for a 00). The 2nd and 3rd guitars opened up some over time, but not as much as the Engelmann top guitar. Because of similarities in construction, I am led to suspect that a large factor in the difference in tone might be in the stiffness of the tops made from different types of spruce: (1) Does that sound plausible to you? (2) Should I be thinning the tops on stiffer spruces another 0.010" or so? (3) Is it plausible that this is just a difference in the time for the spruce varieties to open up, (4) Are there other things that you imaging might be causing the differences in tone. (5) Other advice?

Thanks in advance for sharing your thoughts and knowledge,
Gary

[Ned Knepp]

Hi, Gary, I'm an amateur so my opinions are questionable when it comes to this sort of thing but I've spent a LOT of time working with wood.

It seems to me that the species of a wood could only approximate any individual piece's flexibility. I know that I have read about the importance that some builders place on assessing the stiffness /flexibility of ever pieces they are using on an instrument to determine how to utilize it best. The little bit of building that I've done seems to indicate that I need learn to do this with each piece too. I guess that what I"m saying is that it seems to me that each piece will need to be handled independently as it is worked, what ever it's species, to determine if it will act and react as wanted and needed. I don't know if it is possible to set a single dimension that will work on every top. I think that this is one of the reasons that so many builders tap tune while building their tops.

But then again, what do I know. I'm sure that someone else with better knowledge and a lot more experience will come along soon and perhaps let us know that my views are balderdash. I do know that wood can be variable and that it sometimes matters more what tree it came from than which species it is.

Ned

[David Houchens]

Gary, I go by the stiffness that Ned talked about. I mainly build mandolins,I have only built 8 guitars. Its a little different for me because of the size of a guitar top compaired to a mandolin top. Also my mandolins arched top is graduated heavier in the middle to lighter as you move out toward the edges.
Something I mean to do soon is build a defection board. A jig that would allow me to test how the top reacts to a certain amount of preasure. With a guitar on the jig before the back is on, you can alter bracing or sand the outside of the top to achive the desired flex. The mandolin one( or archtop guitar) would press down on the top. The belly bridge guitar jig would of course pull up on the top.
Without others input, it will take me awhile to know exactly where to stop. Although doing repairs I do from time to time have the backs off of instruments. These tests could add to the pool.

[Tim Mace]

I was going to mention, though I probably have the least experience of anyone above,no matter what is used for the top or back that I tap for a good "clear" tone that I can pin my ear on.Not a
specific note but a musically audible one.If it don't ring it probably won't sing is my theory.I'm not locking into a static thickness.Some woods need to be thinner to be heard "clearly" IMO.
Read Manuel Velasquez interview on Cunpiano's website. That man knows his stuff about getting
the most out of tone woods.Very informative.

[Rob Mercure]

Hey Tim,

I'm not familiar with the site and I've tried several google searches to find it - could you post the URL or some other information as I seem to been kinda dense in finding it.

Rob

[Evan Bradley]

Google searched - Cumpiano website Manuel Velasquez

http://www.cumpiano.com/Home/Newsletters/Issues/twentythree.htm

and

http://www.cumpiano.com/Home/Newsletters/archive.html

[Rob Mercure]

Thanks, not being familiar with the person the name misspelling (sp? ) threw me.

Rob

[Tim Mace]

I misspelled Cumpiano in my fervor.Did I also mispell misspel?