|Building my 2nd
Acoustic Guitar - Page 2
January 4, 2008
In the last couple of weeks I've gotten a fair amount done, working around work, the holidays,
etc. As promised, I did a good bit more bending. I found (though it's not much of a secret, I
guess) that when you've come to the end of a bending session, once you've got a side bent to the
point where you can get it into the mold, it's best to wet it down thoroughly and then clamp the
heck out of it. Here's a fully bent side wet and strapped down...
By the way, I'm working on the sides first because I want to hold off on the neck, top, and back
until I receive the supplies I ordered. Anyway, while I worked on bending the sides I also fiddled
around making other body-related parts. Heel and neck blocks, for example. On my last guitar I
used a straight mortise and tenon for the neck joint, but for this one I'm going to try a modified
dovetail. I'm not going to cut it with a router but with saw & chisels and maybe a router plane. At
least that's the idea. Here's the neck block laid out for cutting. Where the dovetail stops at the
bottom I cut off the block so I can make through-cuts, then I'll glue it back on when the dovetail
mortise is done.
I also made my linings out of mahogany. Linings, of course, are the reinforcing, roughly triangular
pieces that expand the gluing surface between the sides and the top and bottom. I copied a clever
little jig of Paul Lloret's that makes it easy by using a sled and ganged circular saw blades. Similar
to a box joint jig, I marked a line continuing the spacing and then just moved the last cut over to
that line each time:
I cut a whole pile of linings in about 15 minutes. Then I dressed them up a bit by
chamfering/radiusing the bottom edge with a little block plane. This is really just for appearance
inside the guitar, but there is a marginal weight relief benefit too, I guess.
Here's my stock of linings, as well as some spruce bracing I roughed out of the billets I bought (the
raw billets are on the far left and the roughed out braces are next to them). I also made the small
mahogany cross-grain braces that will reinforce the back joint -- they're on the far right.
Once I finally got both sides very close to stable in the right profile, I set about cutting the extra material
off the ends so that I could butt joint the sides at the neck and heel.
OK, so the plan shows the back braces radiused to put an..equatorial? crosswise? curve in the
back. This strengthens the the back and gives it a nice appearance. So I made a template of
about 16 inches of a 15 foot radius circle. I planed two sides of my braces straight and drew the
pattern on them (both sides of each brace) using the template. Then I planed the braces to that
curvature. The curved surface is the one that is glued to the inside of the back to pull it into a
gentle arc; the straight side, obviously, is for the clamps. Here I'm gluing up the first brace. I'll
trim the braces to their final shape after they're glued up because a) I want them to be strong
during the glueup to keep the curve steady, and b) I need them to be flat on top for the clamping.
To help ensure strong clamping pressure along the entire curving length of the brace I used a stiff
but flexible piece of spruce as a caul on the outside. This also of course helps protect the surface
from the clamps. Here's the other side of my clamp-up.
The chalked '5's are the original lumber supplier's marks. They are still there because I haven't
yet sanded or scraped the outside of the back. I did all the thicknessing from what I decided
would be the inside, to avoid planing tearouts and other insults to the 'good' side.
January 15, 2008
My plan was to remove an end plate from the mold and spread the sides just far enough to
accommodate my ryobi saw. Then I would cut through both sides simultaneously, with the mold
serving as a saw guide. Then when I closed the mold back up and reattached the end plate the sides
would come back together in a perfect butt joint! Here I am set up to begin sawing the bottom joint.
The end plate is gone from the mold, the mold is clamped to the bench, and the sides are clamped in
place. I secured the overlapping ends of the sides with two sets of clamps, using two of my side cauls
to hold the sides securely and to provide a saw guide on the inside. Note: It looks like the upper bout
is up off the bench, but that's just a shallow tool tray in that part of the benchtop. The whole thing's
flush to the benchtop, I promise.
Unfortunately, of course, nothing is perfect. Here's the completed cut from the inside. Apparently I
didn't exactly register both sides flat against the benchtop (despite my promise) because the cuts aren't
both 90 degrees. And when I tried to trim them to 90 degrees of course I shortened them somewhat, so
there's a gap left. However, it won't matter, because that'll be covered by (in fact, replaced by) the inlaid
Here's a closer view, showing how I've turned the cauls to present flat surfaces both to the sides and to
the saw so as to guide it as it passes between them. I've just barely started the cut... should be perfect...
... and the same thing happened when I cut the sides at the neck end. Here we're a little farther along,
with the neck block cut and glued in and linings applied, but you can see the significant gap between the
sides. You can also see that I didn't do color correction on this picture! This gap matters even less than
the one at the heel though, because the entire area will be cut away to open up the mortise.
Anyway, here are the completed sides in the mold. I have glued on small spruce cross-braces to
ensure that the sides don't split, and I have glued in the tail and neck blocks and linings as well. I made
the spruce cross-braces as long as the sides are wide, which I'm not sure is a good idea. It maximizes
the effectiveness of these braces, but when I trim the sides/linings to match the top and back it will be
a pain to trim the end grain of those braces. Regardless, you can see where I glued lining blocks over
the spruce braces so there's no gap in the linings.
After I finished the construction of the sides I turned to the back. I had received my orders from
LMI and Stewmac, so I had my center backstrip in hand. I was shooting for .09 to .095 inches for
the thickness of the back, and the backstrip was right at .12 inches. So I planed the back halves until
they were just a bit thinner than the center strip, then glued them up with the strip in a sandwich.
Last time I inlaid the backstrip, but it's easier this way. Once that was dry, I planed and scraped the
backstrip flush with the back and glued on the cross-grain center reinforcing strips to the inne
surface of the back. Then when that was dry I sanded the strips to give them a nice rounded profile
and laid out the positions of the back braces. Then I cut away the reinforcing strips where the
braces cross. That's where we are below, in a closeup view.
And then I laid the completed sides over the back, traced the outline onto the back, then
bandsawed the back to its profile, just a bit oversized. The waist-brace issue wasn't a
problem this time (see Acoustic No. 1) because the profile of the sides was OK outside the