What's on the Bench?

Having swapped plane and chisel for scalpel and scissors, here's a picture of a recent project!

A Cane Toad gives his life for science.

I may have left it a little late in life to go "back to school", but the move has at least provided me with a new and exciting challenge as well as a much-needed sense of direction. Having said that, I'm already looking forward to a break at the end of the year and the opportunity to resume my regular woodworking pursuits.

I'll be back!

Cheers
Pete

Preparing Bindings and Purflings

When it came to preparing purflings for two of the guitars I'm currently building, the first step was to laminate veneer sheets into a black/white/mahogany/white/black sandwich. Rather than the black-dyed maple I used as the outer veneers when preparing an earlier batch of strips, I substituted black fibre sheet (sometimes called fish paper) this time to minimise the risk of deformation or splitting when the strips are bent to fit the purfling channels; the last time around, some of the black maple veneers collapsed slightly in the area of the waist and had to be discarded.

The brayer pictured above is a tool commonly used by printmakers - I sourced mine from a local art supplies store. It's the ideal tool to quickly and evenly spread glue when laying up the veneer sandwich. Titebond III is a glue well suited to this task; it's relatively heat and moisture resistant and the layers of veneer are less inclined to de-laminate when the strips are moistened and bent to shape.

With a small circular saw mounted under my table-saw bench and equipped with one of Stewart-MacDonald's fret slotting blades, I switched the saw on and raised it slowly, cutting through a masonite sheet I'd clamped over the table until the blade was fractionally higher than the thickness of the veneer sandwich, at which point I locked the saw's adjusting lever. Feeding the veneer sandwich through this very fine blade minimised wastage and resulted in an extremely clean cut. I was quickly able to produce enough purfling strips for two guitars, with a couple of strips left over as spares in case of breakage or buckling.

Preparing purflings for the rosewood guitar was an even simpler exercise; they're a simple combination of one black and one red veneer strip - thin enough that strips could be cut from the veneer sheet using a steel rule and a craft knife and pliable enough that pre-bending the strips is unnecessary.

Where the bindings are concerned, I chose to glue contrasting veneers to the edges of the binding strips - again using Titebond III - prior to bending them. Ebony bindings can be a pain to bend so I took the precaution of spraying them lightly with SuperSoft 2 veneer softener the day before I bent them - the softener plasticises the wood strips somewhat, reducing the chance of breakage. Taking care to arrange them into matched pairs, I taped the strips together, misted them with distilled water then wrapped the assembly of strips in brown paper and aluminium foil and bent them in my Fox bender. I began cranking down the press screw at the waist when the thermometer reached 240F and, when I'd bent the upper and lower bouts and applied full tension at the waist, let the heating blanket climb to 310F where I let it sit for a further 5 minutes. I switched the blanket off and removed the binding strips when the machine had cooled to room temperature.

Despite the fact that I'm currently working full time and distracted by those unpleasant but unavoidable weekend chores, I'm setting myself modest targets every week and making steady progress. Installing these purflings and bindings on the three guitar bodies is my next task.

Cheers
Pete

Guitar-Shaped Objects

With these guitar bodies assembled at last, I'm better able to imagine what the completed instruments might look like. It's very satisfying to have reached this stage, but I know there's a lot of work remaining.

Sitka Spruce/Claro Walnut; Sitka Spruce/East Indian Rosewood; Redwood/Claro Walnut

Having laminated the veneers from which I'll slice the purflings, my next job is to prepare purfling and binding strips, then rout out the ledges on the bodies to accommodate them. With the right jigs and tools this shouldn't be a particularly challenging job, but as a "hobby builder", the interval between guitars is significant; I'm not usually able to perform this task frequently enough that I ever feel entirely at ease with the process. With three instruments in the pipeline though, I should be feeling more confident by the time I carry out this step on the last of the current crop.

Cheers
Pete

Soundports

I've posted Matt Mustapick's observations on soundports before, but it seems an opportune time to do so again:

"This concept came originally from the great classical maker Robert Ruck, who puts two small holes on each side of the guitar, very close to where the neck joins the body, rather than one larger hole. The main advantage of the soundport is that it gives the player a "front row seat" to enjoy a strong direct signal from the soundbox. This feature takes nothing away from the forward projection of the instrument. From 20 feet away the guitar is just as loud. For anyone closer to the guitar, it adds a great deal of richness to the sound, owing to the dual sound source which creates a stereo field."

Prior to marking and cutting the side soundports, I took the precaution of gluing two thin layers of veneer to the inner surface of the sides as reinforcement.

Cross-grain veneers provide a measure of protection against cracks

In recognition of the veneers' primary purpose which is to strengthen the area around the ports, their grain runs perpendicular to that of the sides. Some builders argue that cross-grain veneers actually promote cracking by restricting the expansion and contraction of the sides that would otherwise occur. While I accept that such veneers do indeed limit the capacity of the sides to move with fluctuations in humidity, the distance between the linings in this area of the upper bout is small and any potential dimensional change is minimal. If it was a credible risk, we'd surely see cracks developing where the headblock and tailblock similarly restrict the sides' movement across the grain.

In addition to their practical role of protecting against cracks, the veneers also provide me with an opportunity to introduce a contrasting maple line around the walnut guitar's port and extend the rosewood guitar's black and red theme.

Dremel extension handpiece with mini circular saw blade fitted - before and after

A mini sanding drum in the Dremel handpiece takes me to the line

Final sanding required, but essentially, they're done

Very soon, I'll prepare myself mentally for the onerous job of installing purflings and bindings - a task that never seems to get any easier or less stressful!

A recent guitar, with soundport

Useful links:
The Shrinkulator is an online tool that calculates dimensional change in wood with variations in moisture content or relative humidity.



Cheers
Pete

Back at the Bench - Headstocks

Hopefully, this post marks a transition to business as usual after the disruptive and sometimes stressful process of moving house. As if that wasn't enough of a distraction, our newly acquired house and garden required a time-consuming facelift, but with much of that work now behind us, I can at last devote some guilt-free time to my hobbies.

Macassar ebony headplate

To ease myself back into normality, I've spent a little time working on the headstocks of the two guitars I'm currently building. Using a masonite template as a guide, I've band-sawn the headstocks to within a couple of millimetres of their final shape then accurately affixed the template to the headstock face using the indispensable and ever-present double-sided tape; a few taps from a soft-faced hammer ensures that the template is firmly attached to the headstock's face. The laminate trimmer I use to complete this job is adjusted so that a bearing on the shaft of the router bit rides along the edges of the template. Using this arrangement, it's then a relatively straightforward task to reduce the headstock to its final shape.

I've learned the hard way that when using this method consideration needs to be given to grain direction and the trimmer's direction of travel if damage to the headstock is to be avoided. Trimming the extremities of the headstock's end where they transition into its long edges demands special attention. On the upper corner of the headstock corresponding to the bass side of the neck, I guide the trimmer in a clockwise direction, effectively "climb-cutting" as the bit begins trimming the headstock's end adjacent to that corner; on the opposite upper corner of the headstock corresponding to the treble side of the neck, I guide the trimmer in an anti-clockwise direction. As an added precaution, I trim the end of the headstock before I trim its sides so that any minor chipping will be removed when the long edges are trimmed as a final step. Needless to say, different headstock shapes will require their own unique approach.

Observing the same precautions described above, I've also routed out the ledge that accommodates the headstocks' purflings and bindings, this time using a spiral-downcut router bit and the trimmer's adjustable guide. The rebate on one of the headstocks is pictured below, with the final result on the other shown for comparison. Hopefully, I'll have both of the headstocks completed before the weekend is over.

Laminate trimmer, with bearing guide fitted

Binding rebate prepared

Bound and ready for clean-up

I mentioned in my previous post that my plan was to construct a purpose-built workshop at the rear of the house. It's still an attractive proposition, but after much thought, I decided that at this point in time I'm unwilling to sacrifice what could easily be another twelve months of my life to such a major project - spare time is in short supply as it is. Another significant factor in my shelving of those plans is that once we'd found homes for the assortment of bits and pieces we all seem compelled to accumulate, a generous amount of usable space remained in the double garage at the front of the house. Importantly, with an abundance of fluorescent ceiling lights in the garage, lighting is more than adequate for my purposes. If there's a downside to my use of the garage for guitar building, it's that my partner may find her car coated in wood dust from time to time - I'm sure she'll understand!

Cheers

Pete

Another Moving Experience

When we were forced to find a new rental property last year, my guitar-building pursuits were seriously disrupted while we hunted for a suitable house, packed innumerable boxes, moved our accumulation of "stuff", then found homes for everything once we'd made the move. During the weeks that followed, my attention was focussed on building a workbench from scratch and establishing some semblance of order in my new workshop. Having achieved all that, I enjoyed more productive times and was pleased to be able to complete a couple of guitars and make good progress with the others I've featured recently on this blog.

Stability hasn't lasted long however, and barely 12 months later we've taken a critical look at our situation from the point of view of finances and lifestyle and have purchased our own home. As a temporary measure, I'll set up shop in the double garage, but the long-term goal will be to build a workshop at the rear of the property with the luxury of being able to give consideration to the heating and cooling, lighting and storage requirements best suited to our budget and the specialised needs of my guitar building hobby. In many respects it's a distraction I'd rather not face, but I'm confident that the planning, expense and hard work involved will pay off in the long term. It's my hope that I'll be much more inclined to spend time building guitars, particularly through our extreme summers when it's too easy to spend what spare time I do have lounging around in the air-conditioned house!

Updates to my blog will slow to a trickle in the weeks ahead, however, normal service will be resumed as soon as possible.

Cheers
Pete

Saddle Slots and Bridge Pin Holes

Although I'm nowhere near ready to make use of them, I've spent some time lately working on the bridges destined for the two guitars I have under construction for no other reason than it's a job I can devote short periods of time to in a spare moment, or treat as light relief between more demanding or time-consuming tasks.

To facilitate drilling of the bridge pin holes in a perfectly straight line, parallel to the saddle slot I've previously routed out, I glue a small wooden block to the front edge of the bridge blank on the treble end prior to cutting the bridge outline. I trim the block carefully using my disk sander so that as the bridge is slid along a makeshift fence attached to my bench drill's table, the centre of each hole will be equidistant from the slot. Having guaranteed alignment in that direction, I need only take care then to align the bit with the string spacings marked on the bridge as I prepare to drill each hole (a white ball-point pen is a godsend when marking dark woods like this ebony). A brad-point bit makes accurate alignment much easier and produces a perfectly clean hole provided it breaks out through the lower surface of the bridge into a backing board of MDF or scrap timber.

With the bridge pin holes drilled parallel to the line of the saddle, there's a consistent break angle for the strings as they pass over it. While some reason that this guarantees an equal downward string pressure along the saddle's length, the fact that string gauges and tensions vary from string to string casts doubt on the validity of that argument. A slight increase in the saddle's height towards its centre and the potential use of radically altered tunings such as "Orkney" tuning (CGDGCD low to high) complicate the matter still further. Whatever its other merits though, it's a neat look and I'm assured of adequate downward pressure on the saddle and therefore good transference of the strings' energy to the soundboard.

It seems there's no hard and fast rule where bridge weights are concerned; popular wisdom has values falling within a fairly wide range. Given that there are a multitude of factors influencing the guitar's sound, I somehow doubt I'll ever build enough instruments to draw any meaningful conclusions where small variations in bridge weight are concerned; there are so many other variables likely to have a more significant and measurable effect should I feel the urge to experiment. That being the case, I'm happy to aim for a more or less consistent bridge weight from one guitar to the next. With ebony bridges such as these, I shoot for a weight of between 30 and 35 grams, making use of a cheap digital gram scale as I shape and shave the bridge wings to their final thickness.

Useful links:
Routing the Saddle Slot

Cheers

Pete

The Fingerstyle Guitar - Gluing the Soundboard and Back

There are several commonly used methods of clamping the soundboard and back as they're glued to the rims, but the technique pictured here is the one I've adopted; it works very well, and I feel no need to explore other options. I use thin bungee-cord to apply the necessary clamping force, with a caul made from masonite and cork sheet in place to distribute pressure evenly around the guitar's perimeter. The caul focuses clamping pressure on the edge of the back or soundboard, preventing any deformation of the top or back plates which the tightly stretched cord might otherwise cause. It also serves to protect the delicate soundboard wood from damage where the cord breaks sharply over its edge. I trim the top and back plates to within a few millimetres of their final dimensions prior to clamping; there's minimal overhang and therefore no leverage brought to bear by the bungee-cord on the edge of the plates.

I haven't become anywhere near proficient enough with hot hide glue to consider using it to attach the soundboard and back plate to the rims, and in any case, I'm not convinced of the benefits of doing so. That being the case, I'm happy to continue using Titebond Original, applying it the gluing surface of the linings with a 1 inch foam roller after the rim assembly has been securely clamped in the outside mould. The roller allows me a high degree of control over the quantity of glue applied and, if I've judged it well, there's negligible glue squeeze-out at the intersection of the linings with the top and back plates and therefore little need for clean-up inside the guitar body. I attach the back first, the advantage being that once the bungee-cord has been secured, I can flip the entire assembly over and inspect the interior of the guitar through an opening in the base of the mould, cleaning up what squeeze-out there is with a damp sponge.

Click any of the photos for a larger view.

Cheer

Pete

The Fingerstyle Guitar - Notching the Kerfed Linings

Once the kerfed linings are glued to the sides, the sandpaper-lined concave dishes I made use of when shaping and gluing the top and back braces serve their other purpose by helping me sand a drop-off onto the edges of the rim assembly to match the curvature of the back and top plates.

I can then use a Dremel rotary tool to rout pockets into the linings to accommodate the brace ends. Using the more traditional kerfed linings whose saw kerfs face into the guitar body, there's always a danger that if one or both edges of a brace pocket happen to be in close proximity to the kerfs, a chunk of wood will be dislodged as the pocket is cut. With reverse-kerfed linings, however, the individual sections of wood between the kerfs are firmly glued to the sides and serious chipping of the exposed face of the lining on either side of the brace pocket is far less likely, provided some simple precautions are taken.

When routing the brace pockets, it's important that the Dremel is guided in such a way that the router bit's clockwise rotation doesn't contribute to tearing or chipping of the linings as the pocket is cut. This is particularly important to observe where the left-hand edge of the brace pocket is concerned (i.e., with the guitar side facing me). With that in mind, I make my first cut towards me in the direction of the guitar side along this left-hand margin, easing the router bit into the lining for the equivalent of around half the bit's diameter; a second shallow entry cut on the right-hand side of the pocket defines its width. Several light passes are made from left to right until a single recess is created between the two entry cuts. I repeat this process until the recess extends to the guitar's side and make final adjustments until the end of the brace fits snugly within the pocket. It's difficult to avoid chipping entirely, but by guiding the router in the manner I've described, it's of a minor nature and can be easily cleaned up with sandpaper.


I rout the pockets in pairs, beginning at the tail-block end of the body. If the first pair of pockets is accurately marked and cut, the centre-line of the back will be correctly aligned from that point on. If a minor adjustment to the back alignment is required, the pockets can be modified accordingly. The second, and subsequent pairs of pockets can then be more accurately positioned, with correct alignment of the back more firmly established as each pair is cut.

Some builders postulate that because reverse-kerfed linings stiffen the rim assembly once attached, there are resultant improvements in the sound of the instrument. Occasionally, it seems, views such as this are repeated often enough by individuals held in high regard within the luthier community that they become accepted as fact, whether or not they've been held up to close scrutiny. I acknowledge that I have a lot to learn and always try to have an open mind when reading of the experiences and opinions of other more experienced builders, but after looking at popular wisdom such as this from all angles, I'm left unconvinced. For what it's worth, my personal view is that while it's somewhat helpful having a stiffer rim to work with in the course of constructing the instrument, from the point at which the back and soundboard are attached to the rims, any contribution the linings may have made to the rims' stiffness is eclipsed by the strength of the top and back in compression. I suspect that in the finished instrument, the linings - reversed or otherwise - play little part beyond their primary purpose: to provide a gluing surface for the top and back plates.

Cheers
Pete

The Fingerstyle Guitar - Side Reinforcement

For almost as long as I've been building guitars I've followed the lead of others and have fitted kerfed linings to the rims, then installed wooden reinforcement strips to span the sides between the top and back linings. Although this remains common practice, it seems an increasing number within the lutherie community are coming to the view that this could potentially do more harm than good, the thinking being that if the guitar sustains a significant impact, the area of relative weakness created at the intersection of the side reinforcement and the lining could contribute to a crack developing at that point - it makes sense to me.

For this guitar then - and for its rosewood and spruce companion - I've chosen an alternative approach which is to to glue cloth bias tape across the full width of the sides at regular intervals and install the linings over the top of it. The rationale for this is that as the glue-impregnated cloth spans the entire side and will remain somewhat flexible, the weak point I've described is largely avoided. In the unlikely event that a crack develops in one of the sides for whatever reason, the tape will provide a measure of protection against the crack propagating along the length of the side - at least until a permanent repair can be carried out.

Useful Links:
Installing Side Tapes

Cheers
Pete

New Wood Purchases

I have a love/hate relationship with our strong Australian dollar at present. It's too convenient an excuse to click the "Buy Now" button when I spot particularly desirable pieces of wood on favourite web sites such as Allied Lutherie's but, of course, it's also of benefit once I've given in to temptation. Resistance is futile, it would seem.

Ample evidence of my recent weakness can be seen below. Those poor souls similarly afflicted with "Wood Acquisition Syndrome" can click the pictures for a closer look. 

European Spruce

Port Orford Cedar

European Spruce needs no introduction, but Port Orford Cedar is a relatively uncommon tonewood. Luthier's Mercantile has this to say about it:

Similar in appearance and scent to Alaskan Yellow Cedar, Port Orford Cedar is stiffer, lighter and thus more suitable for soundboards. Indeed, it is highly sought after for the bold, robust, responsive tone that it imparts on an instrument. It is very even textured, with a slight golden-white color and tight, even grain. A great advantage to the builder is that this wood is more immune to splitting than absolutely any other soundboard wood.

The Port Orford Cedar is in transit as I write this and I'm impatient to inspect it, flex it, tap it - and smell it! Aside from its promised tonal and structural advantages, I'm looking forward to experiencing the pungent peppery smell it's said to impart to a completed instrument.  It's almost worth combining it with a back and side set of Claro Walnut for that reason alone given walnut's delicious aroma.  Such an instrument would surely be the ultimate "perfumed guitar"!

Useful links:
Port Ordford Cedar - Stansell Guitars

Cheers
Pete