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New ground all round
You may have
seen the guitar-cittern I built immediately on my return from Vashon
in May after becoming enthused about the instrument whilst visiting
Wally Bell. With a 595mm scale length, it turned out much better
than I dared hope but as a guitar maker, I did have a head start and
simply set about applying those principles and methods to an
original design from which I first of all constructed the mould. It
fired me up sufficiently to begin this latest instrument to a more
traditional tear-drop design and with a carved and graduated top of
sitka spruce. Incidentally, that piece of wood was obtained from an
Alaskan Native American by the name of Ishmail whose family name now
escapes me and who produces stuff like 20 foot totem poles. I lugged
it back from Vashon in July 2007 in the bottom of my suitcase having
left most of my clothes behind, and laid it up with the intention of
cutting 3 guitar tops from it. It was pretty dry when Ishmail gave
it to me so after another year, it was ready for use and when I ran
it through the thicknesser, it just came to life. Oh joy! It was
sawn perfectly on the quarter with medullary everywhere. Beautifully
straight and even of grain, it had "carved top" written all over it
and so, I split it lengthways, thicknessed the 2 book-matched halves
and set-to jointing it.
Having alluded to the wood being dry, I'll digress for a moment to
deal with the subject of safe storage of materials and the absolute
need to be sure that the materials used to build any instrument, are
as dry as possible and have therefore shrunk to their minimum
possible dimensions. Its not the absorption of moisture that kills
stringed instruments, but the process of rapid drying. Stringed
instruments have to be able to deal with atmospheric moisture but if
allowed to dispel it too quickly on a repetitive cycle, the
shrinkage will cause the wood (usually top first) to split.
"Shrinkage cracking" will be accelerated if the original materials
were still "wet" when fixed together with glue. Over exposure then,
to hot and dry conditions will too quickly expell moisture absorbed
by the wood which then has no freedom to contract because it's fixed
solid to other pieces and the result is invariably, matchwood. I
therefore keep a de-humidifier running constantly and I regularly
test the wood and over the years, have become a congenital
hygrometer watcher and for very good reason. You just cannot take
chances with this stuff. All of you makers and repairers will know
exactly what I'm talking about as I'm sure will those of you who
have had to have expensive restoration and repair work done on
vintage (and maybe not so vintage) instruments that have cracked up
over time. If this subject is new to anyone then best advice is to
take appropriate care of instruments, especially if travelling
between climatic extremes, to control moisture content and to avoid
too much exposure to excessive heat and dryness.
In the next blog, I'll summarise the work completed to date with
some appropriate photos. I'm now at the stage of closing the
soundbox when things really begin to take shape.
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There are more pics in the
gallery!
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Preparation - early stages
Before
construction can begin, thought must be given to shape and
dimensions of the finished article and I always try to have a clear
image in my mind of how I want an insrument to look when its done,
even down to the details of binding and decoration. As a matter of
personal taste, I'm not big on elaborately decorated instruments and
my mantra has always been "elegant simplicity" alongside the use of
only the best materials I can source because quality of sound begins
and ends with the materials used.
So, you need a mould made of two layers of threequarter ply glued
together and bandsawed and sanded accurately to shape. For this type
of instrument I build on the outside of the mould rather than the
inside as for guitars. I do this because the blocks of vertical
grained brazilian mahogany need to be fixed precisely in place as a
first stage. These are spot glued into recesses in the mould and the
glue seals remain unbroken until the sides and one set of linings
have been installed. I will have routed the dovetail mortice to the
heel block before fixing the block to the mould, after which I will
bandsaw the block to shape, keeping the offcuts to use as cauls when
glueing in the sides.
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Back and Ribs(sides)
Having selected these in Indian Rosewood, the first task is to thin
the wood and joint the back. Preferred thickness is normally 2.3 to
2.5mm though it is possible to go slightly thinner than this. Any
thicker and the wood does not bend easily and you risk it
fracturing.
For this type of instrument the sides are cut to a wedge taper. I
want the instrument to finish at 95mm tail depth and 80mm at the
heel (inc. top and back thicknesses). Its very important not to cut
the sides exactly to finished length but to leave at least 50mm at
each end and therefore make the required curvature easier to
produce, trimming off the excess later (my tail blocks are never
flat and always curved on the glueing surface). The tapered edge of
the sides is always the edge to which the back is glued, on any
instrument and the tapering of the box towards the heel increases
the rigidity and strength of the instrument, while at the same time,
increasing the volume of air in the soundbox. I soak the sides for a
few hours before bending and the electrically heated oval aluminium
pipe quickly expells the moisture and so with moderate pressure, the
wood bends easily. Once bent roughly to shape it is clamped to the
mould and when dry it will have "set" to the shape of the mold with
only fine adjustments required, if at all. The tail ends are cut off
so that the joint is tight and perpendicular to the baseboard. It's
very important to work with the mould "top-down" on a flat
baseboard, ensuring that the sides remain in contact with that
surface when glueing and clamping. I leave the excess length at the
heel block to be trimmed off flush after glueing.
The back is jointed along its centre via traditional "sandstick"
method, in my case the stick being the edge of a two foot aluminium
spirit level to which 100 grit garnet paper is glued. I joint, using
a tried and tested method which involves the wood laid flat on a
board to which one side is clamped while the other is pressured
against it by hammering wooden wedges along its outer edge and the
centre prevented from bowing up by a long heavy caul and clamps. I
really love doing this operation but don't ask me why. The back is
bandsawed to shape, leaving around 5 or 6mm excess to be trimmed off
after glueing to the sides On this instrument, a thin filet of
boxwood picks out the centre joint but I like to vary this on
different instruments and sometimes I will just have a plain back
without centre strip.
On the inner surface of the back, a strip of cross-grained spruce is
glued for strength and the braces are cut from vertical grained
spruce with their glueing surface curved to a 15 foot radius. This
produces a gentle curvature to the backwhich apart from being
aesthetically right, makes the instrument much more rigid and
strong. One thing I have learned over the years is that there is
seldom an operation done for aesthetic purposes only and there is
usually a very practical reason to do with structural integrity that
dictates why instruments are constructed in the way that they are.
The braces are set equidistantly apart and they are glued to the
back using hardwood cauls along their length to spread the clamping
pressure evenly. During this process the back must be supported by a
strong but flexible plate of hardboard to protect it from the clamps
and again, to spread pressure evenly. Its worth mentioning the
method used to make the braces. It would be time-consuming to make
each brace individually. I worked out a long time ago that you could
make several in one operation by taking a block of spruce, scribing
on the curvature with a template cut to the desired radius,
bandsawing out the shape, smoothing out the curve on the belt sander
and then slicing up the block on the bandsaw. This method also
ensures that the curvature is consistent on all the braces.The
braces can then be run through the thicknesser to the desired width
and there you are - minutes only.
The braces are shaped with a small thumbplane, finished with garnet
paper and either scalloped or tapered towards their ends. Again,
this is not done because it looks pretty but because the back would
be too rigid to vibrate properly if left the way it was. The ends of
the braces also need to fit into notched linings later but more
importantly, whilst instruments need to be strong, they also need to
be "loose" if the soundbox is to perform efficiently so always, the
luthier tries to achieve the perfect balance between quality of
sound and structural integrity.
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Fitting linings and preparing
the sides
to receive the back
The linings
provide the glueing surface for the back and top and I make these,
again from vertical grained spruce, 6mm wide and 15 mm deep. Once
thicknessed they are kerfed on the bandsaw and fitted using clothes
pegs and the odd clamp if necessary. The cuts in the linings go
almost through, which allows the lining to conform to the curvature
of the sides. I bevel one edge rather than cut triangular sectioned
linings which don't, in my view, provide any real advantage and
which are more difficult to glue in. I want to be absolutely sure
that the linings are tightly clued in place with no gaps.
The small vertical spruce struts reinforce the sides against
cracking and prevent any damage-induced cracks from spreading along
the length of the side.
Once the carcass is completed, the tricky process of fitting top and
the back especially, can begin. Fitting the back to any instrument,
especially the guitar. is one of luthiery's more difficult
operations bearing in mind that when braced, the back is arched
which means that the waist on a guitar back for example, is higher
than the extemity of the upper bout, where it strikes the side of
the instrument, which in turn is higher than the extremity of the
lower bout. This means that the side of the instrument must be
profiled in a series of rising and falling curves if it is to meet
the back neatly and be glued at its perimeter without excessive
clamping down in order to make it fit. "No stress" is the mantra
here to ensure that the instrument remains "loose". Fitting the back
to a tear-drop shaped instrument is less exacting but still requires
the same degree of care. Forcing it to fit will distort and stress
the back unnecessarily and this will be clearly visible, especially
under lacquer. Patience is the key but like everything else, it gets
easier with practice.
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The carved-arch top 1
The top is
very much the business end of the instrument and I've been working
on it simultaneously with the other operations already described.
Even more care needs to be taken and the work on it proceeds
methodically. The top needs to be profiled on its outer surface
first and with both the neck angle and the string height at the
bridge in mind. I want the latter to finish as close to the optimum
height as possible with a small tolerance built in, ie 18 to 21mm.
The neck angle or "set" can be adjusted slightly by tapering the
underside of the "tongue" of the fingerboard, if necessary but I'll
try to avoid having to do this if I can.
An accurate full scale drawing of the long profile of the top is
useful in helping to maintain the correct neck angle and lie of the
fingerboard on the finished instrument. Having worked on both
violins, F-style mandolins and the Les Paul that I built for my son,
I'm reasonably confident enough to work by "eye" and without
recourse to cross-section templates. This goes back to what I said
earlier about having a clear image in my head of the finished
instrument.
Wood is removed as quickly and as economically as possible from the
outer surface using a sharp block plane until I have the rough-out
of the shape and a symmetrical curvature to each half of the top,
working outwards from the centre joint which is always the datum
line in the construction of any instrument.
Once this stage is completed, I begin to smooth out the dome shape
of the top with a smaller thumb plane followed by a hand-held belt
sander. The top is securely clamped throughout. A straight-edge
helps to keep a check on the smoothness of the curvature and any
flat or high spots are "humoured" away until I'm satisfied that it's
right. The oval sound hole is scribed on with a pencil around a
half-oval template to ensure complete symmetry of the soundhole
which is then pierced and carefully cut out with a coping or fret
saw, hand held, cutting just inside the pencil line. The soundhole
is finished off with a knife with recourse to as little sanding as
is possible to get away with in order to preserve, clean, sharp
lines. (same principal as knife-cutting "F" holes in a violin top).
The slope and glueing surface where the fingerboard will eventually
lie has already been done with the plane and bench mounted belt
sander and finished of with flat sanding blocks.
The exacting bit comes next with the hollowing out of the inner
surface to produce an "arch" which graduates from 6mm thick at the
centre line to 3mm at the line where the inner perimeter of the top
meets the inner surface of the linings. This leaves a dead flat
surface where the top sits flush on the glueing surface formed by
the linings and side thickness (some 8.5mm wide). I will have
already scribed this very important pencil line by placing the
carcass on top of the inverted top, making sure that the centre line
through the heel and tail blocks correspond with the centre line of
the top. Wood is carefully removed from the inner surface using a
curved sole plane which if kept sharp, can move easily across the
grain as well as along it. The curved sole naturally produces a
hollowing effect, augmented by careful use of a gouge where
necessary.
Work progresses concentrically and thickness is checked using a dial
caliper. Mine is home-made with a clock gauge mounted in a rigid
beechwood frame which is clamped to the bench and the work pushed
into its jaws to accurately measure the thickness at any given
point. I tend to think predominantly in metric but as this old gauge
is imperial, a quick mental calculation converts thousandths of an
inch to millimeters. It works for me and produces accurate results.
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The carved-arch top 2
With the inside surface of the top finished with 100 grit garnet
paper and the thickness checked all over, it's time to fit the "X"
brace though I did note that even with so much wood removed, it was
remarkable how light and yet how stiff and strong the top felt. With
guitars, stiffness is a very desirable quality and will determine
the thickness to which spruce can safely be reduced. The same
principle applies here and there is no doubt in my mind that this
particular piece of sitka is of very high grade all round (AAA).
Nevertheless, it will have to bear an enormous downward pressure
with 10 strings and a very steep break angle from bridge to
tailpiece and will still require further stiffening in the form of
the "X" brace. The position of the "X" brace is a moot point but
both intuition and common sense seem to suggest that to support such
a large top evenly, it would be best placed centrally. The most
vulnerable portion of the top on this type of instrument, apart from
the soundhole area, is that portion between the bridge and the tail
block where the downward pressure has the most potentially
distorting impact. I therefore decided to place a short transverse
brace at right angles to the centre joint, close to midway between
bridge and tail and slightly nearer to the block to further stiffen
the top.
The "X" brace is made from two pieces of vertical grained spruce
joined with a glued, cross-lap joint but before this is done, the
position of the final position of the "X" brace is pencilled onto
the inner surface of the top. The trick now is to draw the curve of
the arch top onto the brace while holding it steady to the pencil
line. To do this, I use a small block of softwood with one end
rounded to a semi-circle and a hole drilled through it, into which a
very sharp pointed pencil is inserted as a snug fit. Holding the
brace steady and with the rounded end of the block in contact with
the inner surface of the top, the pencil point is drawn along the
length of the brace, automatically tracing the curvature of the top
onto each brace in turn. It is vital to ensure that the braces are
marked and held at the point at which each brace crosses the centre
line and where the cross-lap joint will sit at the centre of the
"X".
The braces are then carefully bandsawn along the curved line just
drawn, leaving a little to be planed and sanded to a finish which
ensures that this glueing surface of the brace meets the curvature
of the top accurately. Needless to say this is a very exacting
operation which takes both patience and care and there is no room
for sloppy work here.
The ends of the braces are trimmed off to a precise length which
ensures that they will taper to nothing at the point at which they
will touch the linings when the top is eventually glued in place.
One important trick here is to chamfer the ends of the braces on the
glueing surface so that when laid in place, they actually begin to
leave an increasing gap between the brace and the inner surface of
the top, requiring the ends to be "forced" down with clamps. This
has the effect of producing an upward pressure onto the top,
pre-stressing it against the load that will be placed on it when the
instrument is strung up.
The braces were thicknessed to 10 mm before shaping and jointing and
were around 35mm tall. Once glued in place, the "X" brace is planed
down to a height of 12mm at the the cross-lap, tapering steadily to
zero at the four ends. I use a hardwood "X"-shaped caul which pivots
at its centre joint, to glue the brace in place, ensuring that
clamping pressure is evenly spread, while protecting the outer
surface of the top from the clamps with small soft wood cauls. The
pivot point of the caul ensures it can be simply adjusted to fit any
angle of brace. You will find that the tap-tone of the top increases
in pitch with the "X" brace in place and by planing wood off the
braces, the tap tone will gradually lower in pitch as the top
becomes less stiff. I don't have a particularly scientific approach
to tap tuning and whilst I will try to bring the pitch to a C to D
range if possible there is always an optimum clarity of tone to be
found and which I will always try to find as I remove wood from the
braces.
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Bracing
considerations and why an "X" in this case?
The theory and development of the bracing of stringed instruments
and especially their soundboards, has been the subject of endless
fascination and experimentation while luthiers over the centuries
have wrestled with the age-old problem of sound vs strength. It is
very soon apparent that they don't work when built from thick, heavy
material which can't vibrate easily. A solid electric guitar
"unplugged", graphically makes this point and so, when a hollow
wooden box of flimsy and perishable material with a wooden appendage
protruding from it, has strings stretched very tightly across it
from end to end, the laws of nature basically determine only one
possible outcome, that is, the contraption will endeavour to crush
or fold itself in half as quickly as it can contrive unless a way
can be found to prevent it from doing so. The answer may be simply
to stiffen it by glueing thicker, heavier pieces of material in
various strategic locations but, if it is a musical instrument that
one is trying to produce, the answer isn't quite as simple as that.
Early luthiers approached the problem with "ladder" bracing - pieces
of wood placed at intervals directly across the width of the
soundboard at right-angles to the grain. This certainly had the
desired stiffening effect but such a configuration pretty well
dampens much of the sound produced. The problem wasn't solved until
the 17th/18th century Italian violin artisans discovered that the
placement of a solitary brace along the length of the grain and
cutting only slightly across it, had the most exhilarating and
disproportionate impact on the sound produced from a small wooden
box by a bow drawn across its strings - and so we have the "bass
bar" and the secret was out - or was it? The violin is a miracle of
ingenuity which has remained a virtually flawless concept since its
perfection by the great makers, in the way it balances and counter
balances the stresses imposed upon it by the strings. It combines
the two fundamental components of carved-arch construction and
longitudinal bracing, which in the violin, produce an instrument of
breath-taking efficiency and strength. But the guitar is not the
violin and its size and shape do not easily lend themselves to a
working combination of strength and sound quality, with the same
pretty much applying to the modern cittern with its larger body
sizes and longer scale lengths).
It took until the mid 19th century for classical guitar makers to
really catch on to the effects of longitudinal bracing although to
be absolutely fair, the development of the modern classical guitar
as we know it and the use of longitudinal bracing, do go hand in
hand. The "fan bracing" experiments of Antonio Torres proved
conclusively that a system of longitudinal braces, fanned out across
the lower bouts of the instrument produced a remarkable mixture of
enhanced tone, volume and sustain. Of course, to maintain the
structural integrity of the instrument, it still required two
strategically placed transverse braces either side of the soundhole,
which graphically exemplifies the fact that the art of the luthier
is the quest for the most efficient compromise between the quality
of the sound required and the structural integrity of the instrument
itself. With gut or nylon strings, this was not too great a problem
for classical guitar makers but the advent of the steel-string
guitar in the USA of the 1920's posed much more serious problems
which "fan bracing " could not solve but which the "X" brace could.
Larger soundboards on instruments of long scale length with steel
strings which almost double the load applied by the gut strings of a
classical guitar, simply magnify the problem of "fold-up". The worst
examples of this phenomena result in the forward rotation of the
bridge, producing an "S" curve in the top which distorts it upwards
in the area behind the bridge with a corresponding dipping of the
soundhole area and the raising of the guitars playing action to
unplayable levels. This is further exacerbated by the sinking of the
top below the tongue of the fingerboard and sometimes the rotation
of the heel block, all of which contrives to further stress the neck
in a forward bow. The pin bridges on most steel string guitars play
into the hands of the instruments propensity to fold itself up
because the force exerted by the strings at the bridge is upwards
and therefore contrary to the force exerted on carved arch top
instuments with tailpieces. The "X" brace brings fundamental
stability to the guitar top without having to resort to ladder
bracing and still leaves the bracing running more with the grain
than across it. The steel string guitar still requires considerably
more strategic bracing than just the "X" on its own, in order to
retain it's stability and whilst it is no longer the only way to
brace a steel string guitar top, it is probably still the most
widely used method, which speaks volumes for its efficacy in
providing that great compromise between sound quality and structural
integrity.
In terms of the instrument I'm building just now, the similarities
with violin technology are obvious in the inherent strength and
ability of the arch to withstand a lot of downward pressure, coupled
with the longitudinal stiffening and stabilising effect of the "X"
brace which, if I get it right, should result in a strong but loose
and freely vibrating diaphragm. We shall see!
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Closing the soundbox
In an earlier blog I talked about fitting the back of the
instrument. This basically entails carefully planing down the sides
and linings together, with a small, flat-soled thumb plane, to the
correct curvature so that the arched back meets the sides neatly and
without having to be forced into place when glueing. When I glued
the linings in place, I left them slightly "proud" to make it easier
to plane them to a slight angle of around 2 degrees so that the
sloping curvature of the back will lie flush on the linings.
The glueing surface of the tailblock may also need a slight angle
for the same reasons. The heelblock is first trimmed off to the same
angle as the tapered edge of the sides but this angle usually needs
to be increased further so that the back will lie perfectly on the
block and at the same time, accentuate the longitudinal curvature of
the top when glued in place. If the back does not lie perfectly on
the block when glued and clamped, you will end up with a visible
"kink" in the backand the world will know that your craftsmanship is
not what it should be. I may do several "dry-runs" with the back
clamped but not glued until I am satisfied that I can proceed to
glue it in place. You can adjust the blockangle carefully with a
small plane and sanding blocks but I do it quickly with a bench
mounted belt sander. You need strong nerves and a good eye to do
this type of operation so I wouldn't recommend you try it with your
first cittern at least, as a mistake could prove very costly.
Once you're happy that the back will lie neatly on the sides and
blocks, you can trim off the ends of the braces having marked where
they cross the sides when the back is "centred" accurately. Its
important to mark both the braces and the linings so that you know
exactly where to cut notches in the linings and exactly how much to
trim off the braces so that they fit neatly into the notches. Think
these operations through very carefully, mark accurately and do
several dry runs until you're sure you're right before you remove
any wood. This is knife and chisel work and tools should be razor
sharp. I still get a buzz when the back drops into place, perfectly
centred and with very little slack movement which means you can then
glue it in place without fear of it sliding out of alignment on the
glue. Alignment and overall fit need to be as near perfect as you
can possibly achieve. I use cello spool clamps with cork pads for
this operation with heavier clamps and cauls at the blocks.
After several hours the clamps can be removed and the back overlap
trimmed off now or else left until the top is fitted.
Fitting the top is an easier operation simply because the arch has
been carved and the glueing area around its perimeter left dead flat
to fit onto the flat surface formed by the sides and linings
together. The blocks are similarly left flat for the same reason.
I'm not fitting the ends of the "X" brace into the linings because I
want the top to "float" more freely and remain "loose", relying on
the inherent strength of the arch and the reinforcing, stiffening
effect of the "X" brace to deal with the downward load of the
strings. Again, centering the top accurately is vital and is
achieved in this case by tapping in a fine panel pin into the heel
and tail blocks, bang on the pencilled centre line drawn onto the
gluing surface of the blocks. These lines have been there since I
started. The pins are cut off with nippers to a height of only 2 mm
to ensure that they don't come through the top when it is pressed
down onto them. The top is easily centred but bear in mind that it
too has an overlap of excess wood all around it, to be trimmed off
later so make sure you allow for this before you gently press the
top onto the pins or else the soundhole will end up in the wrong
place and you'll have to compensate with a longer fingerboard. Two
small holes will be left when the top is then removed while glue is
applied to the blocks and linings, before relocating the top to the
pins and clamping as for the back. When the excess wood is later
trimmed off, you will see the soundbox in all its glory for the
first time. A clean up with garnet paper and there you are, ready
for binding. Its now that a sense of heightened excitement is felt
as the finished instrument really begins to take shape and you will
marvel at your own handiwork - hopefully!
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What's in a neck?
There are several ways to construct a neck as there are different
woods to be used and while generally my choice would normally be
quartersawn Honduran, Cuban or Brazilian mahogany, in this case I've
chosen to use a nice piece of maple with a bit of "curl" to it.
Maple is usually very strong and stable but harder and more
difficult to work but I've chosen it here for aesthetic reasons - I
think the instrument will look good with a bright, white neck with
ebony fingerboard laid on it.
Starting with a single piece around a metre long, I've cut and
thicknessed it to finished dimensions of 80mm wide and 25mm thick. I
start by marking it out along its length with rule and try square
allowing some 220mm for the peghead and nut, for 12 frets to
neck/body joint (of scale length 595mm), 25mm for the tapered
dovetail tenon and 2 pieces each 100mm in length which when glue
together will form the heel area. Marking off 88mm up from where the
nut will eventually sit, a diagonal line joins up the opposite
corners of the rectangle drawn on the edge of the piece which is
then sawn through on the angle, both sawn faces sanded absolutely
flat and with the sawn off piece flipped over to form the angle of
the peghead. (The photo above explains this far better than words.)
Glueing the two pieces is done with them laid on their edge on the
bench overlap with greaseproof paper under them to prevent the neck
being glued to the bench. The paper will be folded up over and lie
between the two wooden cauls which will squeeze the two parts
together. The two sanded faces must not be allowed to slip laterally
out of perfect alignment so the longer piece is clamped to the bench
while the shorter piece butts up against a wooden stop. Its vital
that neither piece moves during the operation. A dry run ensures
that you're ready to go and the two pieces are clamped and glued
between the cauls mentioned above, forming a 15 degree (approx)
angled peghead, long enough to accommodate machine heads, 5 left and
5 right and with a bit to spare for final shaping. This laminated
method ensures that the long grain runs largely parallel with angle
of the peghead and therefore stronger in construction than if the
peghead were cut from one large block, which would leave too much
short grain running across the edge of the head and it's also very
wasteful. By laminating the heel area from separate pieces, the same
result is achieved - stronger and less wasteful. I've never had
either a peghead or heel area fail, using this method so I stick
with it.
An adjustable truss rod is essential on steel stringed instruments
to counter the forward bowing of the neck when under full load and
in this case I'm using an aluminium, box-type with threaded steel
rod, adjustable at the peghead. With guitars I normally prefer the
soundhole adjustable type rod but there are added difficulties
fitting such rods to this type of instrument with steeply raked
neckand smaller soundhole.
A 10mm square channel is cut using a router mounted upside down
below the bench with the workpiece moved along a straight fence,
having first been accurately centred and tested. When glued in
later, the box will be flush with the surface of the neck and the
adjusting nut will protrude slightly beyond the bone nut on which
the strings will rest, and into the pocket cut to take the Allen key
used to adjust the rod. I won't go into the mechanics of how the rod
actually works, at this stage.
The upper surface of the peghead is covered with, in this case, a
veneer of rosewood which is not only aesthetically attractive but
performs the practical function of covering the angled lap joint and
strengthening it. A similar veneer can be glued to the back of the
peghead if desired though I don't normally go in for this.
This is the neck construction method I use and whilst there is a
great deal more work to do by way of bandsawing and carving, setting
the correct neck angle and forming an accurate and well fitting
neck/body joint, the basic construction is done.
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Making and inlaying the rosette
I made this
rosette from one piece of black and white linear purfling sandwiched
between two pieces of black/white checked purfling. These are wound
tightly around a plywood oval cut exactly the same dimensions as the
soundhole. The purfling is first dipped in hot water for 2 or 3
minutes, enough to soften the glue and make it pliable before
applying glue to the edges of the linear purfling, glueing the 3
pieces together and pinning down one end tightly to the oval
template and its baseboard. Working quickly, the whole assembly is
wound around the template, pinning it down as we go until the end
meets up with and overlaps the other. This loose end is carefully
trimmed of to butt tightly against the other end. This joint will
lie on the centre joint of the top above the soundhole and will be
covered by the fingerboard later.
A step is then cut around the edge of the soundhole to take the
rosette, using a purfling cutter and sharp chisel. Once this ledge
is true and flat, the rosette can be glued in place using clear tape
to pull the rosette in tight to the step. Once dry, the rosette is
scraped and sanded flush with the surface of the top, having been
made thick enough to allow this to be done, after glueing.
Apart from giving the instrument an aesthetically pleasing focal
point, because it cuts across the open grain of the soundhole edge,
an inherently weak area of the top, the rosette seals and
strengthens, guarding against the shrinkage-cracking that might
occurr later in the instruments life.
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Making and bending the
binding
I made this
particular set of bindings by superglueing fine boxwood flats to the
edges of some plain rosewood binding. This is a straightforward
operation done with the rosewood laid out flat against a straight
edge clamped to the bench, with greaseproof paper beneath it to
prevent it being glued to the benchtop. Superglue is carefully run
along one edge and the boxwood flat is then pressed up against it
with a caul. I do about 6 inches at a time so that the job doesn't
get too messy and remains manageable. It takes but a few minutes per
strip to accomplish and the superglue won't breakdown during the
bending process.
Bending:
The binding
strips are soaked in cold water for a short time before bending by
the same method as the sides. Thin strips such as these bend very
easily and I use the mould to test the curvature as I go, dipping
the binding in water to keep them moist. Once bent to shape they are
held tightly to the edge of the mould with heavy rubber bands and
allowed to dry.
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Cutting the binding channels
There are
various ways to do this and a variety of tools and gadgets to aid
the process, depending on the situation.
The most common method is to use a router mounted upside down
beneath the bench and a 6mm straight bit protruding to the desired
height above the surface of the bench. I used this method to cut the
back channels but because of the back's curvature, a tapered wedge
with the cutter protruding through it, is needed to compensate for
the curvature of the backand to keep the sides perpendicular to the
cutter. Test cuts are done on scrap pieces of wood to ensure the
correct depth and height of cut and as in this case, where I will
also be inlaying inner boxwood strip a deeper cut will be needed and
more than one pass necessary to avoid break-out caused by trying to
remove too much wood in one go. The depth of the cut is regulated by
the roller bearing guide which is bolted to the bench, sits directly
above the cutter, and which is adjustable for depth of cut. This is
a scary operation if you've never done it before but the results are
superb.
Because of the very severe curvature of the top, especially at the
heel end of the soundbox, the above method is neither suitable nor
possible so these channels were cut using a Dremel moto-tool with
the appropriate channel-cutting bit but with some specially designed
fitments which screw onto the cutting end of the dremel and which
allow it to be held flat against the sides of the instrument. These
fitments provide 4 different cutting depths so that only a small
amount of wood is progressively removed at each pass. This can be
even scarier than the above router method because fingers are very
close to the cutting tool but with care and patience, a good clean
job results.
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Binding the soundbox
The
channels were cut as described in the last blog with the top channel
cut deep enough to take a linear inner purfling of
black/white/black/white with the outer black adjacent to the lighter
coloured spruce to give it a strong contrast and more definition. To
the back, I decided to cut a two-stepped ledge with the inner-most
and shallower of the two ledges cut to take a brown/white
herringbone which, when sandwiched between the dark rosewoods of
binding strip and back, provide another strong and crisp contrast.
The fitting of these strips simultaneously needs careful planning to
ensure everything needed is to hand including short strips of clear
tape lined up along the edge of the bench to be pulled off at will
in a systematic approach, starting at the tail of the instrument and
after first making sure to start them off on the centre line of the
soundbox. Doing one half of the instrument at a time, glue is
generously applied to the channel(s) and also to the inner surface
of the rosewood binding strip. A clean, damp rag is kept to hand to
clean up the "squeeze-out" as tape is progressively applied, pulling
the strips hard into their channels while at the same time, pulling
them hard down against the base of the ledge. In awkward areas where
more pressure is needed, a double layer of tape is used to stop it
shearing when pulled hard over the angle formed by side/back or
side/top.
On reaching the heel end of the soundbox, the excess binding/purfling
strip is trimmed of flush with a fine toothed saw. And so the four
composite strips are glued in place and left for 3 or 4 hours before
the tape is removed. Removing tape from spruce needs care to ensure
that the soft summer grain is not torn out so its best to pull this
obliquely back on itself while keeping it pressed down with the
other hand. With book-matched spruce halves it helps to discern the
direction of grain "runout" and to remove the tape by pulling it in
the same direction. A little test at each end will tell you which
direction of pull will do least potential damage and its worth
taking care over this as it will save a lot of heavy sanding later.
The strips are always left a little "proud" to be scraped and then
sanded flush with back, sides and soundboard after the tape has been
removed but its important to get rid of any remaining surface glue
in the process. The aim is to finish with as narrow a glue line as
possible to avoid unsightly gaps which can be a devil to get rid of.
Some gaps are inevitable along the outer lip of the binding ledge
where the router may have removed small slivers or chips. By running
superglue along this line and raising some rosewood dust, these gaps
will disappear and because the colour match of the dust is perfect,
these small gaps are filled and become undetectable. If you don't
attend to this, they will appear as gaping chasms as soon as lacquer
is applied and will remain as an unnecessary and unsightly blot on
what ought to have been a smooth and level side.
Finally the matching rosewood/boxwood tail fillet is fitted using
knife and chisel. With a single boxwood purfling strip, mitering the
joints is unnecessary which would not be the case if the purfling
was multi-layered with contrasting coloured strips, but that's for
another day.
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The neck/body joint and neck
"set".
The "set"
of the neck refers to the angle at which the neck lies, relative to
the leading face of the heel block or in other words, the neck/body
joint. (The photo above shows the "set" angle very clearly
with the neck angled steeply back.) I first clamp the tongue of
the fingerboard in position and simply use a bevel to measure the
angle it forms with the leading face of the heel block which has
already had the tapered dovetail mortice routed into it. This angle
is then transferred to the heel area of the neck at the 12th fret
position following which I bandsaw off the excess, leaving around
15mm to spare where the tenon will be routed. Using a belt sander
with tilt table set to the same angle and ensuring that the neck can
be held perfectly square to the belt, the "set" angle is sanded flat
and square. Using router templates which I made myself, the tenon
template is centred and screwed onto the face of the "set", clamped
into a "workmate" and the tenon routed in seconds. The tenon is cut
slightly bigger, requiring a little filing of its glueing faces
until it makes a tight fit all the way down to the base of the
mortice. The centering of the neck is checked with a long
straightedge, which, if your preparation has been thorough, should
be perfect or at least no more than a degree or so off centre.
Because the neck has not yet been cut out to shape, when centering
of the fingerboard later you have a little tolerance to play with if
the neck happens to be slightly off-centre. Sorry if this isn't
absolutely clear but if you're really into the details of this then
you could do worse that read the work of either David Russell Young
or Irving Sloane for a full explanation. There are many methods of
jointing necks to bodies and I've used most of them. Done properly,
one is pretty much as good as the next provided that the basic
universal principals of extreme accuracy in measuring and marking
out are adhered to and the type of joint used is cut just as
accurately, remembering always that the "set" and "centering" of the
neck are crucial.
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Neck, fingerboard and final
blog
In an
earlier blog I described how the neck was fabricated along with the
fitting of the truss rod but it is now time to bandsaw it to shape
and to thickness it. Remember that a centre line was drawn on the
face of the neck and the tapered shape of the fingerboard clearly
marked. The dovetail tenon has been cut on the line of the 12th fret
where the neck will join the body and a 5mm gap has been left
between the head veneer and the narrow end of the fingerboard where
the bone nut will lie. Parallel lines are drawn 3mm outside of the
fingerboard area to be bandsawn, leaving a bit extra wood for final
shaping. Using the centre line the shape of the peghead is
transferred to the head veneer using a half template to give perfect
symmetry. Marking out the whole of the neck should be done very
accurately for obvious reasons.
The peghead will finish at 15mm thick so this line is pencilled onto
both edges of the peghead. The neck will taper from a thickness of
16mm at the 1st fret to 18mm at the 9th fret (excluding the
thickness of the fingerboard) and so this line is drawn onto both
edges of the neck while the finished shape of the heel is
transferred onto each side of the neck using a template. The whole
neck profile is then cut out on the bandsaw. The shape of the
peghead and fingerboard portion of the neck is bandsawn next,
leaving that 3mm excess to be trimmed off during that final carving
of the neck and after the fingerboard has been accurately aligned
and glued in place.
The ebony fingerboard was cut to finish at 42mm wide at the nut and
50mm wide at the 12th fret and its edges smoothed and the taper
checked for accuracy. The fret positions were marked on the centre
line with sharp dividers and using a bevel, the fret slot positions
are carefully marked with a sharp knife, the cut from which helps
guide the fretting saw. Using the bevel as a guide, the fret slots
are then carefully sawn to the correct depth. Unlike a guitar, no
position markers will be inlaid to the face of the board but 3mm
lengths of 1mm diameter brass rod are drilled and glued into the
edge of the fingerboard.
With the neck tightly set in its mortice (already checked to make
sure it is perfectly centred through the body of the instrument),
the fingerboard is clamped onto the neck and checked with a
threadline to ensure it is similarly aligned through the centreline
of the soundbox. When done, two 1.5mm holes are drilled through the
1st , 11th and 14th fret slots through which brass pins coated with
soap will hold the fingerboard during the glueing and clamping
operation, preventing it from sliding out of position. The soap
prevents the pins from getting stuck as they will not be removed
until the glue is dry. If the neck joint is good and everything is
perfectly centred and aligned, the neck can be removed from its
mortice and the fingerboard glued to it.
The peghead has been thicknessed using a 10mm router bit in the
drill press. Taking only very light cuts, the back of the peghead is
pushed under the router bit until the desired thickness is reached.
This operation can be a bit scary at first but it ensures that front
and back faces are perfectly parallel to one another, and very
little sanding is then required. The peghead will look sharp, clean
and perfectly thicknessed.
The holes which will take the tuners are marked on lines drawn
parallel to the edges of the peghead and 12mm inside it. The hole
positions are marked at 28mm centres and pilot drilled with a 2mm
bit. The holes are then drilled out with a 9.5mm bradpoint bit but
to prevent "breakout", I never drill right through but instead,
partially drill from each side of the peghead in turn which ensures
that the holes are cleanly cut.
With the fingerboard glued in place, the neck and heel are carved
using a variety of rasps, files and gouges until after good sanding
with 100 grit garnet, the whole neck is as it should be - smoothly
profiled and tapered and ready to be fitted as one assembly. Because
of all the preparatory measuring, centering and pinning, this is now
a straightforward operation with only minimal risk of poor fitting
or alignment. The accurate "set", alignment, and fretting accuracy
are critical to the finished instruments all round playability and
intonation so the utmost care must be taken at each stage.
The fingerboard in this case was thicknessed to 5.5mm but only after
the neck assembly has been fitted, will it be accurately levelled
and the frets installed. I've gone back to flat, rather than
cambered fingerboards but such things are merely matters of
preference and I would profile a fingerboard to the specifications
of the customer. I install frets via the traditional method using a
hammer and hardwood caul and once fully seated, the ends are clipped
off flush with the edges of the fingerboard and using a special
block with file set at 45 degrees, the ends of the frets are
bevelled. Using a heavy machine ground box section with 80 grit
emery cloth stuck to it, the tops of the frets are levelled. This
produces a flat spot which is then removed with a special fret file
drawn along the length of the fret until the flat spot disappears
entirely and the rounded crown has been fully restored. The
fingerboard is masked between the frets with tape to protect it
should the fret file slip and leave an unsightly gouge in the board
which is then difficult to remove. Once crowned, and leaving the
masking in place, the tops of the frets are polished along their
lengths with 240 grit garnet, followed by a final polish with 0000
wire wool. A lot of work in a fingerboard, but absolutely essential
to the instruments performance. I forgot to mention that after the
neck/fingerboard assembly was glued in place and the fingerboard
levelled, it was brought to a high finish with successive grades of
garnet and wirewool, before the frets were installed. (Ebony is
beautiful stuff to work with because its lack of definable grain
lends itself to producing a beautiful glossy finish requiring only
oil or beeswax to sustain its finish). this was done because it is
much easier to produce that finish with no frets in place and it
only then requires going over with wire wool to revive it once the
frets are installed and dressed.
The rosewood/boxwood fillets are fitted behind the heel on each
side. These ensure the cleanest of neck/body transitions and the
boxwood purfling all joins up, dividing the instrument into clearly
defined panels.
A good sanding with various grades of garnet paper, finishing at 320
grit, followed by a good clean with a tack-rag and the instrument is
ready for its first coat of lacquer. The bridge and tailpiece will
be made during the finishing and the bone nut made later during the
set-up process.
I hope that those of you who are not builders, have at least found
these blogs informative and that hopefully my fellow craftsman might
have derived some amusement from them.
A photo of the finished instrument can be viewed
here
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