|Building my 2nd
Acoustic Guitar - Page 3
February 6, 2008
Here's the back all braced up and ready to go. I have cut away the center reinforcement
strips where the neck and heel blocks go and I have trimmed the ends of the braces so that
they will fit inside the guitar's sides. Speaking of sides, I trimmed the linings on the sides to
allow for the back's braces and profiled the sides and linings so that the back fits nicely with
a tight joint all the way around.
Then I did some work on the top. I thicknessed it the same way I did the back, reserving one side as
the eventual face and doing all planing and sanding on the 'back'. Then located the centerline of the top
and traced the outline of the completed sides onto the top referencing that center line. Then using the
plan I located the center of the soundhole and punched it with an awl. And then I went to work on the
rosette. I had purchased a solid wood lacewood rosette from LMI. It was rather wide in circumfrence
and rather skinny in width, so I planned to use it as the outer ring and put plastic black/white/black
rings as the inner rings.
To make the cuts I usesd a Dremel Moto-tool with a jig built by Paul Lloret:
The greyish center strip is a sliding
section, adjusted by loosening the screw
in the rear, with the pivot point being the
nail that you see just behind the Dremel.
Now, the SAGA OF THE ROSETTE.
First I cut the inner ring (to be occupied
by the b/w/b binding). This worked out
fine and I gained confidence. I moved
on to the outer ring. I carefully calculated
the radius of the lacewood rosette, but I
didn't have the right size bit to cut it in
one pass, so I used a small (1/16") bit.
My plan was to make my first cut in the
center of the rosette area and then sneak
up on it outward and inward if you get
my drift. Anyway, I made a critical
mistake with that first cut: I didn't drive
the nail in firmly. As a result, halfway
around the circle, the jig shifted a bit and
so I ended up with sort of a spiral.
To make a long story short, I ended up having to back up and make my own rosette. In the end it
worked out fine and looks better than my original plan would have. To clean up the mess left by the
'spiral' cut I had made I had to widen the slot to about 9/16 or 5/8 inch, rendering the original wood
rosette moot. I had a nice pice of thin lacewood on hand, which was the peghead overlay I had
ordered. It was just large enough for me to get two semicircles out of, and I bordered the lacewood
with the b/w/b/w/b that was going to be individual rings. Here it is... kind of a fuzzy photo but you
get the idea. The area at left where the rings don't quite meet will be covered by the fretboard.
Then I bandsawed the top roughly to shape by tracing around the sides and cutting about 1/8 inch
outside the line. I'll take care of any overlap once it's glued up of course. Since this will be a 12th fret
neck joint, the upper bout looks strangely bulbous, doesn't it? Like it's hydrocepalic or something.
Next I marked out the positions of the top braces. This can be done any number of ways, but I did it
by laying my acrylic side profile on the plan and marking the spots where the braces meet the sides,
then laying the acrylic profile on the top and transferring the spots, then flipping the profile and
marking the other side.
The top braces, like the back, are curved to impart a slight belly to the top. Here I am gluing on the
second leg of the main X brace. The X brace's center joint is a notch, which needs to be extra-tight
for strength. Again, I left the top profile of these braces sqared for secure clamping. I'll trim them
later to an inverted 'v' shape, sort of like a gothic arch. After that, substantial portions will then be
'scalloped', cut out to make the brace look sort of like a suspension bridge.
And here's the completed X-brace, with the rest of the main bracing roughed-out and resting on the top.
Feburary 14, 2008
And here's the top with the bracing completed. The pattern, including the scalloping layout, are per
the plan I used, which is of a prewar Martin. The smaller braces are all 'tucked into' the larger ones,
with the ends poking into little slots carved into the X-brace and the upper bout cross brace. The
flat plate below the soundhole is the bridge plate, which is maple and reinforces the spruce top from
underneath against the string ends and bridge pins. All the other bracing is spruce.
So the next big job will be gluing the top and back to the sides. I still need to trim the brace-ends on the
top and shape the linings on the sides to make a perfect fit when the back and top are attached. I will
attach the top and back seperately, clamping them with rubber bands while the sides are in the mold.
But the next little job for me is fashioning the bridge. This will be an older style 'pyramid' bridge as
opposed to the modern and more common 'belly' bridge. The belly bridge was developed so as to
provide more gluing surface, but the pyramid style is period correct, so that's what I'll be going with.
Basically, there is a rectangular center section with, oddly enough, a four-sided pyramid at each end.
Here I have created one face of each pyramid and defined the center section. I did both tasks with the
table saw, but now it gets tricky and will take hand work from here out I think. I'm not exactly sure
what species of ebony-type wood this is, but it's very dense and hard, so it'll be a challenge, but a fun
Well, you can see the fate of that bridge in this next picture. It's the one on the bottom
(completely different color is just photoshop artifact). I tried to do the inner planes of the
triangles with a chisel, cutting across the grain, and you can see on the bottom left where I
blew it out completely. I decided to try and do it on the tablesaw and came up with a
workable method which I tested on the blown out blank (bottom right).
Jume 3, 2008 Oim beck!
After defining the center section with the right-angle cuts on the tablesaw, I did the inner and
outer planes of the pyramids on the tablesaw like this: Note: measurements and angles in this
diagram are only to show the setup -- they are not to scale or accurate.:
I clamped the bridge to a sliding auxillary fence to carry it past the blade (the diagram doesn't
show the clamp) -- you could use doublesided tape but the sides of the bridge have to be
absolutely square to the table and it's easier to adjust if you use a clamp. The outer faces are
straightforward as shown in the top diagram. For the inner faces, I moved the fence to the other
side of the blade and tried to make the very tip of the sawblade just barely project into the center
section crosscut. If your saw is right-tilting, reverse the fence positions for the inner and outer
faces. Let me stress again that the sides of the bridge when clamped have to be exactly 90
degrees to the tabletop.
After establishing the inner and outer faces with the tablesaw, it's relatively easy to do the front
and back faces with careful chisel-and-file work. The top bridge in the picture above is fully
roughed out and ready to slot for the saddle.
Here's the body all glued up. After I do the bindings I'll open up the neck mortise by sawing
away the top and sides.
I did a lot of work without taking any pictures...sorry, lazy. But it was all just like my first
acoustic, so check there for details on attaching the top and back to the sides. Only difference
was new mold vs. L-hooks.