Building an Acoustic Guitar - Page 2
January 30 2006 I got a good bit done the past couple of days. As I said at the end of the
last page, I had to do some work on the neck in order to glue up the body. The reason for
this is that I wanted to make and fit the neck joint before gluing the neck block into the
body. It's MUCH easier that way. I am using a mortise and tenon joint here, which will
be reinforced with dowels as you'll see later. It's a method on Irving Sloan's book, and it
looks to me just as strong as the traditional tapered dovetail and with lots less aggravation.
So first I shaped my neck and heel blocks:
The large block is the heel
block , which will reinforce
the butt end of the body.
The smaller block is the
neck block, which will
reinforce the other end of
the body and receive the
Then I joined the sides. In the picture on the last page the ends of the bent sides are just
overlapping and held in place with spring clamps. To joint them I marked the guitar's
center line on the overlapping sections and sawed down through both on that line. Then I
gently trued the edges with sandpaper and glued them with a butt joint. Here those two
joints are clamped up with small cauls to keep the edges aligned. I used tape to keep
tension on the edges to hold them together while gluing.
Then I glued in the heel block. The glued surface of the heel block need to be rounded to
follow the curve of the sides. I intened to use 1/1 inch plywood for the outside caul so that
it would flex around the curve and keep the pressure even, but the thinnest plywood I had
was pretty thick and didn't flex like I wanted. Still, it worked out OK. In retrospect, I
should have kept the sides in the mold for this operation....
....like I did when I glued the neck block below. There are several things going on in
this photo. You can see that the neck block does not come all the way up the side.
This is because the bulk of the taper between the 4 1/8 depth at the heel and the 3 1/4
inch depth at the neck will come off the back. So I want to keep the back of the sides
true until after I glue the top so that the sides will sit straight in the mold for that
operation. Also, because I didn't want to taper the sides until I knew exactly the line I
have to hit for the heel and neck blocks. You can see the prop I wedged at the waist
to keep the sides tightly against the mold while I glued the neck block. You can see
also that the curve of the lower bouts does not quite match my pattern. So sue me.
And lastly, at the heel you can see the decorative maple wedge I inlaid to dress up the
joint there. The guitar will have maple binding on top and back, offset with very fine
black and white purfling. It's going to look pretty sharp. Subtle, but sharp.
While all the joints were drying I used a number 5 handplane sideways to the grain to
get the top thicknessed down to around .11 inch and my bandsaw to rough cut it to
shape. Here is a sort of exploded view of the neck-body join. When I am ready to join
the neck to the body I will cut away the portions of the side and the top that cover the
mortise in the neck block. When this joint is assembled, the top surface of the neck
will be flush with the guitar's top so that the fretboard can sit right on top of both.
Then I glued up my neck blank. I'm using laminations to achieve the long heel that an
acoustic guitar uses.
And that provided me with this lovely neck blank. I will
soon be cutting the scarf joint that will result in a
headstock, but for now I was interested in the other
end. I cut the mortise in the neck block and the tenon in
the neck on the tablesaw, just touching up with shoulder
plane nad file until I had a good snug fit. A good mortise
and tenon should require a bit of persuasion to fit, and
should take a good tug to come apart even before it's
glued. I cut the tenon a bit long to allow a gap for the
And, I finished gluing up and profiling the back braces with handplanes followed by a
February 3, 2006. Once the sides were joined, I put in the taper. To do this I
drew the profile (a simple wedge from 4" to 3" high, the length of the side) on a
piece of heavy paper and traced the line with a pencil, as in the photo below. Then I
glued in the linings on the top (see below). Then I sawed off the bulk of the waste
(which was on the back side) with a dozouki saw and finished by planing to the line
with a small block plane.
Once the back profile was establlished I began gluing on the linings. These are
strips of mahogany in a right triangle profile, kerfed so they can be bent around the
curves of the inner sides. Their purpose is to give a larger contact surface for
gluing on the top and the back.
Here is the next sequence of cuts on the neck. The goal here is to create the
peghead, or headstock, that angles back from the neck and where the tuners are
attached. This method of neck construction is also somewhat stronger than if the
entire neck were carved from a single board because it avoids the short grain at
the junction with the headstock The first cut is the diagonal one. This is called a
scarf joint. After the diagonal cut you flip over the offcut to create the back
angle. I have already done this in the photo. Then I ripped that offcut to the
proper thickness, (which also establishes the length of the neck proper). Lastly I
crosscut the headstock to length. Afterwards I glued on the headstock.
Then I began bracing the top. Here the X-brace is being attached. This is the primary
support for the top. Some builders prefer to put a slight arch in the top for extra strength
and possibly improved tone. I decided to use that method, so just as with the back I
planed a slight belly into the gluing surfaces of the braces so that the top would be pulled
into an arch. Actually the lower section of the top will have a spherical profile. The
upper bout area needs to be flat for where the soundboard is.
Continuing to glue top bracing, Here you can clearly see the X, along with small braces to
support the soundhole area and the large crossbrace on the upper bout. This is the flat
brace. I made it from walnut since I had no more mahogany on hand. The rest of the
braces are spruce, by the way, as is the top itself.
February 6, 2006. After I attached the linings to the sides, I added little reinforcing
strips of spruce to help guard against the sides splitting later on down the road. You
can also see a reinforcing strip running vertically on the tail block. This is a
precaution against the tail block splitting when I drive in the tailpin, which is
wedge-shaped.. The grain of the tail block runs side to side, with the grain of the
sides. The reinforcing strip's grain runs vertically.
Here I have just about finished tapering the top braces. There are many different
bracing patterns and many different ideas about how best to taper the braces, but this
being my first acoustic I decided to stick with the Martin configuration. For this job,
a low-angle spokeshave worked wonderfully in the places where there was room to
maneuver it; I used chisels for the rest.
ACK! At some point I lost the first page of the saga of my first acoustic guitar build!
Instead you have to start with page 2.