Guitar top bracing


In a guitar, the braces act as beams to help support the string loads. The bracing on the underside of a guitar top is an array of beams designed to strengthen the top and control the static deflections due to the string tension, whilst allowing sufficient vibration to couple the strings’ oscillations to the surrounding air; quite a tricky balance to achieve.

The basic principles of beam mechanics that guitar designers need to know are:

Deeper sections make stiffer beams than broader sections. If we double the width, we double the stiffness. If we double the depth, the stiffness rises by a factor of eight, i.e. by the factor cubed. If we double the length, the stiffness of the beam reduces by a factor of eight, i.e. the factor cubed.



Stiffness Map

If we have a look at what that means for a typical X-braced steel string guitar and plot out a mapping of a guitar top’s stiffness we get a diagram like that on the right. It’s somewhat lumpy and in most X-braced guitars the stiffer parts of the bracing structure are not best placed to support the loads. That’s an inefficient use of materials, meaning that the structure is heavier than it need be and the strings have to overcome greater inertia than they should have to in order to produce sound. 


Click to enlarge

 I have developed a more efficient design which puts the stiffness where it’s needed, to satisfy both structural and acoustical requirements.  It uses less material and so the structure weighs less and is therefore more sensitive, more responsive and delivers more sound.  I call this new style of bracing Falcate bracing.  Falcate means sickle shaped.  This new style of bracing is one of the factors that contributes to the high monopole mobility of my guitars that is discussed in "Responsiveness"


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