Acoustic Bass Guitar Lattice Brace

[Redwood]

Hi, I'm interested in building an acoustic bass guitar using lattice bracing, and would like to ask if there are recommendations for top thickness, bracing depth, bracing species, that can be adapted for use on a considerably larger sized body and steel core strings.

I noticed in the first paragraph on section 11.2.4. of the Build book; "It (a Lattice braced top) is a very efficient structure and consequently we have used it in (among other instruments) acoustic bass guitars. For the steel string instruments we tend to upgrade the substrate to western red cedar or even to Sitka spruce in order to achieve satisfactory shear strength in the lattice"

I'm building a prototype guitar and it's specs (as I've drawn them) are as follows;

4-string acoustic bass guitar, E-G
Scale length; 864mm
Body length; 670mm (13th fret at the body/neck joint)
Body width at lower bout; 490mm
The body has a tone-well chassis; 500mm long and 480mm wide
Top is Redwood (only because its what I have in this size)

According to my drawings, if I use a 10m dished top, and the neck is attached so it is coplaner with the top at the upper bout (and using a saddle protrusion of 5mm, the bass will end up with a bridge that is 11mm thick and a 16mm string height over the body.

I'll assume that spruce should be used for the lattice elements, but I'm unsure of the their depth, and the top thickness.

I tend to have an "over the thumb" approach. My intuition says; bump the top thickness to 2.5mm, lattice elements of spruce at 9mm deep. Two things I've learned over the years about this approach; it is prone to error and make prototypes

Does anyone have experience with this?

[lamanoditrento]

I am building a 34in falcate braced acoustic bass at the moment. When I looked at the string tension of four strings, they sit at about the same tension as a 6 string guitar so I have left the bracing height pretty much the same as a falcate steel string.

[Redwood]

Hi, Trent,

Thanks for pointing that out. You're right, based on the info on the packaging, a light gauge (.100-.045) acoustic bass set has 85kg of tension, and a light gauge six-string set (.053-.012) has 76kg.

Have you tested your top and come up with a target thickness?

With the 34" scale instrument I'm designing, I'm concerned that by having the string at a greater height over the body (as a consequence of a longer/larger body,) the equation for this target thickness needs to be modified. Specifically the Vibrational Stiffness Value f (Equ. 4.5-6 on page 4-61 Design book)

Perhaps the only way is to build a prototype and measure the top deflection.

I'm curious, have you heard an acoustic bass guitar with Falcate bracing?

--Oliver

[lamanoditrento]

I am building with a huon pine S/B. Wouldn't have been my choice but that is what the owner wanted. The target thickness came at 3.2mm. With my design, I have minimal changes in the string height from the SB at 14mm.

I have heard a falcate bass a few years ago right when I started building. There are a few bass build threads on here I reviewed before I started though.

My biggest concern is the bridge as it will have to be pinless so getting the weight down is going to be challenging. Though to tell you the truth, I've put a 3 transducer pick up in and I think it will probably mostly be played plugged in gigging.

[Redwood]

Thanks Trent. I'll post some in-progress pictures along the way, let you know what I'm trying. Best wishes-Oliver

[WilliamDavidReynolds]

Thanks Trent. I'll post some in-progress pictures along the way, let you know what I'm trying. Best wishes-Oliver

How did that bass come along? Acoustic basses are my main focus in guitar building and love seeing others approaches