Week two of Acoustic Construction Lab was spent focusing on bracing the guitar top. I chose to use a few pieces of Adirondack spruce that I had purchased, tilt the bandsaw table to match the end grain vertically and re-saw the spruce to get the best quartersawn stock possible. After cutting my braces slightly over-sized, I thickness sanded them to width. The Larson Brothers are known for their unique x braces consisting of a three-ply lamination, with a strip of hardwood between the spruce. I decided to use rosewood to do this for my upper transverse and x braces. Their OM sized guitars also have a top radius of 15’, so I used an edge sander jig to shape a radius on the edge of the brace that is to be glued to the top. After all my braces were radiused and cut to size, I notched and fit the x braces together. Moving right ahead, I began the gluing process using a go-bar clamping deck. I placed a dish with a 15' radius in the bottom of the deck, and bent strips of maple to apply clamping pressure and hold the brace firmly in place while letting the glue set.
The first round of gluing installed the x brace, as well as the upper transverse brace that has a radius of 25'. After the glue had completely set, I started tapering and shaping the laminated bracing using my block plane and chisels.
Next I prepared my lower transverse and finger braces, by tapering and rough shaping them to size. These pieces were constructed using the Adirondack spruce.
I used the scrap Adirondack from re-sawing my brace stock to construct small clamping cauls to fit over the finger braces, preventing them from being damaged by the wood strips used to apply the appropriate clamping pressure.
Both lower transverse braces were also installed during round two of gluing, they were all pressed in a 15' dish and allowed two hours to set.
For the third round of gluing, I installed the maple bridge plate as well as the upper graft, sound hole braces and x brace cap, all made from scrap Sitka spruce pieces left from my guitar top.
By the time Friday rolled around, the top was completely braced and I spent a good part of my day carefully shaping the braces with a finger plane and chisels. While my guitar brace work is laid out true to the Larson Brothers design, I decided to shape the braces themselves in a more triangular approach that closer resembles the Larrivee guitar bracing.
During my down time waiting for the glue to set, I started to prepare my Honduras mahogany back and sides for week three. I joined my back, thickness sanded it and cut out the shape slightly over sized. I also thicknessed the sides and prepared them for bending. With every new day the pieces continue to come together and resemble a guitar more and more.
- Justin Ness
