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Braces
Related Topics: | Bridge Reglue | Bridge Plate | Body Cracks |
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| Gibson TG-3:
Repair Loose Back Braces |
What are braces and what do they do?
Braces, also called struts or tone bars, are designed to both reinforce the plates (top and back of the instrument) and transmit soundwaves to specific parts of the soundboard (top). Bracing patterns are designed to transmit the string tension away from the bridge and toward the rim (side assembally) which is strong and stable. The braces on flat top steel string guitars are commonly referred to as "braces", on classical guitars the term "struts" is frequently used and on mandolin family instruments as well as arch top guitars the term "tone bars" is used.
Steel String Flat Top Bracing
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| The X-Braced Top of a 1960's Gibson B-25. We replaced the top
of this guitar because it was so damaged that it was less time consuming to replace than repair. It should be noted that the manufacturer placed the bridge plate too far forward. This was a significant contributing factor to the demise of this guitar top. |
The steel string flat top acoustic guitar has approximately 180 pounds of string tension to contend with. The bracing makes this possible by spreading tension away from the bridge toward the rim (sides) which is rigid and, thus, significantly more stable than the plates.
X-Bracing
The soundboard of flat top steel string guitars typically have a pattern of bracing commonly referred to as "X-bracing". The "back bone" of this bracing pattern are the cross braces. This is widely agreed upon as the choice bracing pattern for flat top steel string guitars because of its balance between long term structural stability and pleasing tonal characteristics.
Ladder Bracing
There is, however, another bracing pattern seen on flat tops called "ladder bracing" (aka: lateral bracing). Ladder bracing is commonly associated with lower end models of yester-year because it is a simpler bracing pattern to manufacture and does not stabalize the top of an instrument as well or as long as does the x-bracing pattern.. Lateral bracing does produce a distinct tone which has acquired a cult following.
The gluing surfaces of flat top braces are usually not flat, rather, they are radiused (+/- 20') to further aid in the strenthening of the plates. The braces are radiused then glued to the plates. The braces force the plates to conform to the radius of the braces. This means that the plates of a flat top acoustic guitar are not really flat.
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| Ladder Bracing was used by many
manufacturers on the tops of lower or student line guitars. For many years Gibson employed lateral bracing on a number of their ins- truments including their LG series and the above pictured TG-3, a 1960's tenor guitar. This bracing pattern exhibits multiple braces (usually of more substance than those used on x-braced guitars) that run perpendicular to the grain of the soundboard. |
Back Braces on steel string and
classical guitars are of a similar pattern. This is the rim and back of a Gibson LG-1. |
More on Bracing Coming Soon...