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Joining the Top and the Sides
With the top braced and the sides glued to the end and neck blocks, the
top is next glued to the sides. This requires that the profile of the
sides - the edge where the sides will meet the top - be shaped
appropriately. If the top were truly flat, this edge would itself be
flat, which could be achieved by planing the top edge of the sides with
a handplane. However, the top isn't flat - it's slightly arched.
Because of this, the edge of the sides where they meet the top will be
a slightly undulating curve.
The top edge of the sides can be scribed with a line indicating the
correct profile using the arched workboard used to glue the braces onto
the top. The arched workboard is placed within the jig used to support
the top and sides while they are glued, and the sides are placed
inside, with the top edge down. Because the edge of the sides is more
or less flat, the sides will not sit flush on the arched workboard, but
will touch only at the neck and tail block, as seen below.
A gauge is made from a small piece of thin wood, with a 1/16" hole
drilled at a height a little greater than the maximum height the sides
sit above the workboard, at the waist. A pencil or thin-line marker is
then placed in the hole, and the gauge slid along the surface of the
arched workboard along the inner perimeter of the sides. This will
inscribe a line that is an equal distance above the arched workboard
along the entire perimeter of the side assembly. When the edge of the
side assembly is shaved to this line, the sides will sit flush on the
arched workboard, and thus on the arched top for gluing.
The side assembly is then flipped upside down, and the edge shaved down to the scribed line using a spokeshave.
The end and neck blocks must be shaved, too, and are not flat on top, but must be angled to sit flush on the arched workboard.
The angle of the end and neck blocks is checked as they're shaved with
an arched template stick with the same arch as the arched workboard.
When shaving is finished, the side assembly is flipped and the edge
profile checked on the arched workboard. The sides should sit flush on
the workboard around the entire perimeter. If there are gaps, the sides
can be further shaved.
The kerfing can now be glued to the edge to provide increased gluing
surface for attaching the top. The kerfing is glued on in short strips
(maybe 4 - 6" long), and clamped with clothespins reinforced with
rubber bands to give them extra clamping force. Note that the kerfing
is glued so that it protrudes slightly above the edge of the sides.
This is so it can be shaved down at an angle so it will sit flush on
the arched top, just as the end and neck blocks were tapered.
The top with kerfing glued around the perimeter, but not yet shaved.
The kerfing is next shaved down so that it is flush with the edge of
the sides, but angled to meet the arch of the top. The angling of the
kerfing is checked with the same arched template used to check the
angling of the end and neck blocks.
The kerfing must now be notched to accept the top braces where they run
to the sides. The top is placed onto the arched workboard, the side
assembly is placed on the top, and the position of the braces is marked
on the outside of the side assembly.
The sides are then flipped in the jig and the position of the braces
marked on the top surface of the kerfing to indicate the outline
of the area that must be notched to accept the braces.
The edges of the regions marked are cut with a knife and then notched
with a sharp chisel. The depth of each notch is equal to the thickness
of the brace where it meets the sides.
When the sides are inverted on the top, the braces should nestle
into the notches, and the undulating side profile should sit flush on
the arched top (which is on the arched workboard inside the jig).
At this point the sides can be glued to the top. The sides are
inverted, and a thin layer of glue is spread on the surface of the
kerfing and the end and neck blocks. The side assembly is then inverted
onto the top, and the end and neck blocks clamped. You should see an
even bead of glue squeeze-out along the perimeter of the end and neck
A plywood template cut to the shape of the body profile, but
overlapping by about an inch all around, is then placed on the sides,
and clamps placed all along the perimeter to clamp the sides down onto
the top. Note the holes drilled in the template to permit inspection of
the interior. Note also the cutouts at the end and neck block positions
to clear the clamps already in place there.
As an alternative to the clamps, large rubber bands can be used to
provide the pressure to clamp the sides against the top - this is the
reason "L" backets are used in the gluing jig. The rubber bands used
are number 107 bands, which are 7" long and 5/8" wide. These bands will
put tremendous downward pressure on the side assembly as they are
stretched between the "L" brackets. An example of their use can be seen
when the back is glued onto the top-side assembly.
When the clamps (or rubber bands) are removed, the top is glued securely to the side assembly.
Don't worry about the rough edge of the top; this will be removed when
the body is routed to accept the binding and purfling that will run
aroung the edge of the body.
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