Lattice braced classical guitar build

[escpg]

Hello,
I purchased the contemporary acoustic guitar design and build. After building 30 classical guitars, I am about to experiment a little and try to build the lattice braced classical described in the book.
To me, I feel like I am about to start a walk in the dark, since I do not have any idea on where I will get to. I am a bit concerned especially about the stiffness of this soundboard. I will work on a traditionally braced classical soundboard just to have a referring point in terms of stiffness. Does the lattice braced need to be tuned to a specific note? I will thikness spruce to 1.5 mm, as described in teh book. That is not too far away from the 2 mm that I usually use for my standard bracing. Do I need to aim to a specific note? Rigidity, flexibility? Or just take it easy and go ahead, trusting the mearurements provided in the plan? Also, how about long term stability? I think I will use two linings lengthwise. Anyway, I think I read somewhere that Smallmann thicknessess his lattice braced soundboards to much less than 1 mm, although I am not sure about this. I would like to know if you can share your experience about this and would love to know something from Gore or Gillet in person. Thanks Enrico

[woodrat]

Hello Enrico, Welcome to the Forum, You will find it a friendly place. You have plenty of build experience with 30 classicals behind you so that is great. With regard to the note a soundboard should be that correlates to a stiffness. The book does not look at free plate tuning but rather what that note/stiffness is/should be in the fully coupled system of the closed sound box especially in the finished instrument and gives you strategies to be able to tweak the frequencies post construction. For classicals that would be 180Hz or 190Hz which is as close to exactly between scale tones . That is done so that you dont get tuning problems and wolf notes from a body resonance being near to or exactly on a scale tone causing high admittance of energy on that note.
I wish you well with it. Trevor being the extremely generous chap he is may chip in and answer your questions himself....

John

[Trevor Gore]

Enrico,

It's pretty well all in the book. There isn't any more to add.

Does the lattice braced need to be tuned to a specific note?

In terms of free plate tuning, no.

For a lattice braced classical, aim for a T(1,1)2 of ~214Hz or higher. Because the soundboard doesn't subdivide very much there tends to be a lack of high frequency resonant peaks, which can lead to a rather muddy sound. This can be avoided by pitching the top higher than the more typical 190Hz. Make the guitar as per the book and control the T(1,1)2 by edge thinning (carefully!) and bridge mass. There's a lot that is impossible to tell you because people work differently and to different levels of precision, so don't expect your first lattice guitar to be brilliant, but it should be at least respectable if you work to the guidance/plans in the book.

[woodrat]

Looks like I got my targets wrong Enrico....a bit on the low side.... but exactly between scale tones (or as closely as you can) is important.

John

[escpg]

Ok, thanks for the reply. I will keep it in mind. Enrico