Build page 2

ROSETTE

The rosette is a design element surrounding the sound hole. With only a few exceptions, the primary components of the guitar—the top, back & rim that form the body, and the neck, head stock and fingerboard—are more or less identical from one instrument to the next. This is for good reason because when they are designed and constructed with care, they come together and consistently deliver the great sound I’m striving for. And while I get tremendous satisfaction from making all these various parts, it’s a true pleasure to reach a phase in the build where I can ditch the routine and scratch my creativity itch. The rosette is one of these phases.

The visual splendor of a guitar is realized in the types of wood we make it from, the shapes of some of the various components like the bridge and head stock, the choice of binding and purfling, the design of the headplate veneers as well as the design of the rosette. I will often choose an overall design scheme that has overlap between many of these elements to tie it all together visually.

In this build, I’m going to use koa wood with a combination of dark colored heartwood (old growth) and light colored sapwood (new growth) as the common design thread. The body’s back plate and the head stock have already incorporated these elements, now it’s the rosette’s turn. This design will have radial segments, so I lay it out on paper, on thin cardboard and the actual sound board where it is centered on the future sound hole. This is very important to get the symmetry correct, and have guidance for cutting and laying out each segment.

I have some scrap pieces of koa with sapwood along one edge, but they are too thick to be used for this process so I use my bandsaw to re-saw them to the proper thickness. My idea is to flip-flop each segment so the heartwood/sapwood alternates, creating a sort of checkerboard pattern. The thin cardboard pattern has one segment cut out of it and I used it to draw the shape of individual segments on the material, a fret saw cuts them out to rough shape. One of my favorite tools, the shooting-board and hand plane is used to very accurately trim each segment to size. This is repeated over and over until I have enough to fill my pattern. The fretboard will cover the top part of the rosette, so none are needed there, and I’m adding a different design element at the opposite side.

I hold the segments together with masking tape and glue five together at a time. By stretching the tape across them it draws each segment together tightly. Once each group is dry, I glue each group together in the same way. There are two separate halves on either side of the sound hole.

The paper pattern is glued to a thin piece of plywood, and the glued up segments are spot glued to the pattern. A hole is drilled at the center-point so it can be slipped over a pivot pin in my rosette building board. I use a Dremel tool on a swivel base to cut the glued up segments to width. I use a thin feeler gauge to get under the segments and pry them off the plywood.

This instrument will have Master Grade purfling of black and yellow pin-stripe lines. It’s not commercially available, so it has to be made. I take sheets of black and yellow veneer and cut off enough for what I need; in this case it will be just enough to make the black/yellow/black lines to surround the rosette. I glue them together with polyurethane glue between two thick pieces of UHWM plastic so the glue won’t stick. Once dry, the band saw cuts the individual strips to width.

The headplate on the head stock has a triangular piece of jet black ebony as a design element, so I want to include a similar element on the rosette. Like the rosette, it will be surrounded by purfling lines. I cut a piece of ebony to the proper thickness and use a similar method as was done for individual segments to trim it to shape. The very acute angle and sharp point presents a challenge for making the purfling miter, but the shooting-board makes quick work of it. I set up a temporary “fence” at one half the required angle, and the hand plane trims the purfling to the correct angle. The purfling miters at the short end of the triangle are done with zen-like patience and a sharp chisel.

I use the Dremel and swivel base to cut the inlay recesses in the spruce top. I want the rosette to fit very tightly because once it’s inlayed, I come back with the router and a purfling sized bit to span the margin between the koa and spruce to make the channel for the purfling. For the triangle, I clear out as much as I can with the Dremel, and finish it by hand with chisels. I glue the triangle in first and flush it level with the top. After gluing in the rosette, I rout the purfling channels. I must take care to stop short of the corners and finish them by hand. The channels on the ends also need to be done by hand. Again, much painstaking effort is put into fitting the purfling so the corner miters fit perfectly. The area at the top of the rosette need not look too great, as it will be covered by the fingerboard. The final step is to send the top panel through the thickness sander to level the rosette with the top.