Acoustic Construction Lab - Week 5

  I started the week by cutting my neck out of a Honduras mahogany block, which was large enough to include the headstock and heel without having to use a stacked heel or scarf joint. I figured out my desired neck extension height and routed the dovetail to an appropriate angle, fitting the neck to the body.

 I decided on a heel shape and started to rough it in using a rasp, switching to sandpaper to work it out to shape and size. I also prepared the fingerboard to size and cut the fret slots. I used the finished fingerboard to determine the heal width. 

  Next, I began to fit my dovetail to the body. This is a very important process that involves setting the right neck angle, keeping the neckline centered while avoiding twist, and finally setting the neck flush to the height of the body. I did this using freshly sharpened chisels and a little sandpaper to achieve a tight fit. 

  After setting the neck, I glued blocks of mahogany to the headstock as wings to increase the width of the peghead. I used a template as a clamping caul to glue an ebony veneer to the headstock before shaping it to the desired shape. 

  I also took some time to inlay pearl dots and diamonds into my ebony fingerboard. I started by marking a centerline before finding the center of each fret. I laid out my pattern and used a small router to cut the diamond shapes, and a drill bit for the dots. I glued them in place and sanded a 14" radius into the ebony to level the inlays and finish the fingerboard. 

  I routed a channel into the neck for the truss rod, tapering the depth slightly to the body to allow adjustment through the soundhole. I marked the neck taper from the nut slot to the 14th fret and cut the excess material off using a bandsaw. At the end of week 5 my guitar had a neck that was almost ready to be glued on.

- Justin Ness

Acoustic Construction Lab - Week 4

 With the kerfing glued to the ribs, I sanded the radius into the top and bottom of the sides. I notched the ribs for the bracing and fit the top to the body. I drilled holes in the side of my work board and placed screws staggered every 1 inch around the entire edge.

 For clamping pressure while gluing the top, I used 45 feet of bungee cord and laced it back and forth around the screws firmly. The top was glued with Titebond and allowed a few hours to set before removing the bungee. Once dry, I routed the dovetail pocket into the neck block. I notched the ribs for the back bracing and fit the back, repeating the same process with the bungee to glue it in place.

 With the body now completely constructed, I used a router to flush trim the top and back to the sides. I sanded the ribs flat and square in preparation for planing the purfling and binding. 

 I decided to use wooden rope purfling for the guitar top, with a wooden 4 ply black and white purfling strip for the back. This was all bound with plastic tortoise shell binding. I used a router to cut the purfling groove into the top, and cut the the binding groove into the side with a second cut. I flipped the guitar over and repeated the process for the back. 

 To attach the binding, I started by shaping the purfling strips using a bending iron. Since the purfling is wooden, I used Titebond to glue it in place and stretched strapping tape over the edges for clamping pressure. After the top and back purflings were set, I used an acrylic cement to glue the plastic binding. 

 I spent Friday scraping and sanding the binding to bring it flush with the top, back and sides. I started to layout my fingerboard on the blueprint, and prepared the ebony board to thickness. Another week of construction complete, next I will be building a neck and fitting the dovetail. 

- Justin Ness

Acoustic Constriction Lab - Week 3

   I started the week by preparing my guitar side ribs to the appropriate thickness and length for bending. I added moisture to the mahogany by running the pieces under warm water briefly before wrapping each rib individually in paper towels and tinfoil. I placed a heating blanket on the rib and sandwiched it between two spring steel sheets, placed it on the side bending mold and started the heating process. While applying heat for three minutes, I slowly pressed the center waist clamp down. Next, I bent the lower bout by slowly pulling the spring clamp, repeating the same process for the upper bout.

  

  After the bending was completed,  I let the rib sit in the mold and come back down to room temperature. Once cool to the touch, I reheated for another three minutes and let it cool back down again. 

  The side was now ready to be removed from the bending mold and transferred to the body mold, repeating the same process for the second rib. After placing the ribs in the mold, I clamped the cauls in place to prevent the wood from springing back and left them to sit over night. 

  The next day, I removed the ribs from the mold and trimmed the ends to size. I used mahogany to construct my neck and tail blocks, and glued them to the ribs joining the sides together. I clamped the blocks heavily and allowed the glue plenty of time to set. 

  After drying, I installed my mahogany kerfing to the inside edges of the ribs. I wrapped rubber bands around the ends of clothespins to increase the clamping pressure, and used them to firmly hold the kerfing in place while bending and gluing.

  While waiting for the kerfing to dry, I installed my center strip and braces to the back of my guitar. I used sitka spruce for the center strip, and Adirondack spruce for the back braces. I glued them using the go bar clamping deck in a 20" radius dish. Once dry, I shaped the braces with a chisel and finished them off with sandpaper to give them a clean appearance, as they will be visible through the sound hole once assembled. 

  With the weeks end, the pieces of the sound box are completed and ready to be glued together. Next week will be spent assembling the body, installing the binding, and laying out the neck and fingerboard. Step by step, its all coming together. 

- Justin Ness 

Martin or Gibson, what's the difference?

I like comparing the designs of the classic Martins and Gibsons because while I love the sounds of both, they have distinct tonal differences. The tonal differences and the design differences have helped me to form some opinions and understanding of what I can do as a maker to affect the sound of the instruments I build.
Just to be clear, I'll talk about pre war Martin Dreadnaughts, and Early 40's Banner headstock Gibson Dreadnaughts I've gotten to work on and examine. Trying to describe sound is always tricky, but in general I'd say the Martins sound fuller, warmer, and perhaps a bit louder. The Gibsons have more edge, focus, and clarity. Just my opinions, and I'd really rather you listen to as many as you can and formulate your own ideas on their sounds. I'll list the main design differences, and then go into more detail about each of them in future posts.
Body shapes are similar enough that if you take the Gibson sloped shoulder body style and do everything else in a Martin style, it sounds like a Martin. They are both X-braced with 2 lower transverse braces and 2 finger braces off each side of the X-braces.

3 of the main design differences are;
Scale lengths;
       Gibson 24.625", Martin 25.4"
Arch built in to the top;
       Gibsons had quite a bit of arch, about a 20' radius,
       Martins were built flat, though over the years string tension has pulled an arch into them
Angle of the X-braces;
        Gibsons were around 103 dgrees
        Martins 98 degrees
I've seen some variation from these numbers in the guitars I've seen and I'm sure there are more. These guitars were in ways more hand made, though in factories by many pairs of hands, then most of the modern instruments from individual makers. It all depends on your definistion of "hand made", but my point is there was some variation.
Now go play lots of cool old guitars and we'll talk more about all of these differences and others.