After I looked at a number of guitar building books in the sections dealing with bracing the top and back of the instrument, I began wondering what the effect of various bracing cross-sections might have on the stiffness in the finished instrument.
Some braces are triangular, others rounded and others simply rectangular.
Along their length, braces can be more or less the same height or tapered in various ways. In order to sort out some of the geometries, let's first look at the effect of cross-sectional shape on brace stiffness. Please note that the author is trying to present a simplified view of the problems. Since both cases use the same material, the weight per unit volume of brace is constant. So it's clearly more effective from a weight standpoint to make the triangular brace taller rather than wider to achieve the same stiffness.