Notes and observations

Here are some photos of #3, a concert ukulele in Rio rosewood / Swiss spruce, 385mm scale, ebony fingerboard, spanish cedar neck, rosewood bridge, french polish finish. I've listed it on ebay this evening. Its a nice ukulele. You can read more about it in the note i wrote while building it.

After playing #3 on and off for a couple of days, and doing some very minor top tuning, i've decided to call it the crystal bell. The combination of Rio rosewood and Swiss spruce in a deep concert sized body work together to give it a very bright, clear and nuanced sound. Good sustain, openness, clarity, articulation (does vibrato well). The spruce should open up further over time to become even more exceptional. I'm french polishing it now. I'll post pictures when i'm done. This combination should be really nice in a tenor ...

I just strung the model A4 #3 concert uke for the first time. It hasn't been french polished yet, i wanted a chance to do any top tuning necessary before i polished it. I used Aquilla strings.

First impressions: the Rio rosewood gives the instrument a very focused and bright sound. It projects very well. The spruce top is phenomenal - really nice tone color, sustain, clarity and loudness. Its about 1.5mm thick in the bridge area and is graduated to about 1mm in the recurve area. The deeper body of #3 gives the sound a very interesting depth. The braces were split from the same piece of wood as the top and are about 4mm x 3mm, triangular in section. You can see it under construction here.

More later. I need to adjust the nut and saddle and then i'll take some photos. #35 (Rio rosewood / swiss spruce classical) and the first model A3 tenor uke in flamed maple / cedar are coming along nicely and i'll be talking about them soon.

The top of a stringed instrument vibrates in complex ways. As the string vibrates and energy is transferred through the saddle and bridge to the top, two primary modes of vibration dominate. The first is the up and down diaphramatic motion of the top on its compliant recurve. This mode causes the volume of the air cavity inside the sound box of the instrument to change with changes of the top. The second primary mode is lateral rocking of the top in the axis of the bridge. In this mode, the volume of air inside the sound box is not significantly modulated because as one end of the bridge rises, the other end falls and the motions tend to cancel each other.

Anyone who has listened carefully to a stringed instrument quickly observes that they sound different when listened to near by and from afar. For performers, the near field experience is important, because it is what they hear and it is what provides feedback and guides their creative energies during a performance. For an audience, the far field experience is important, because it is what they hear. I have played classical guitars that sounded very lively when played but when listened to from an audience position projected poorly and sounded dull and i have played classical guitars which sounded like they were ho-hum when played but when listened to from an audience position really projected well and sounded beautiful. The perfect instrument needs to provide excellent near field and far field performance.

This note will examine the effect of the two primary vibratory modes on near and far field performance.

... to be continued

I'd like to briefly discuss the relative merits of two different top construction techniques. Antonio Torres (1817-1892), a Spanish builder known as the father of the modern guitar, introduced the technique of arching the lower bout of the guitar top in order to allow him to build a light top that remained strong enough to resist the pull of the strings. A light top allows a finer and more nuanced response from the instrument, and Torres quickly became famous for the wonderful musical qualities of his guitars. Torres life and work is documented in an excellent book by the classical builder Jose Romanillos called Antonio de Torres Guitar Maker - His Life and Work (ISBN 0-933224-93-1). This practice of giving the top strength with an arch has continued to this day, and a couple of different construction methods have evolved to facilitate it. This note briefly discusses two of these techniques, and looks at their respective merits.

The first technique is the one used by Torres and virtually all classical guitar builders from his time onwards. It is the one i use in my building practice. Torres built his instruments on a solera, or workboard, face down. Torres imparted an arch to his top in the area between the bottom harmonic bar below the sound hole to the tailblock thru the expedient of a solera which was concave in this area. The top would be placed face down on the solera, and the fan braces would be glued to the top and, when dry, the fan braces hold the top in the shape of the concave solera. Torres employed what is now known as the Spanish method of construction and his neck would be attached to the sides and top through the mechanism of a 'Spanish foot'.

Here's a close-up photo of the Spanish foot of a classical guitar i built showing the top, sides and neck in place on the solera. In the Spanish method the Spanish foot receives the sides, top and back of the guitar. Builders who adopt this method typically do not use a neck set. The top and neck are in a single plane, and a flat fingerboard remains flat when glued to the guitar. When they do adopt a set, the neck often tilts forwards a degree or so to obtain a lower bridge height and mass, and when this is done the solera is often progressively thinned or tapered from the top of the soundhole to the top of the body so that the neck and top half of the sound board remain in one plane.

The second technique is one that is popular amongst steel string acoustic guitar builders and some other small stringed instrument builders. This technique domes the entire top, from the top to the bottom. The top is placed face down on a concave form and the fan braces and harmonic bars are glued to the top, similiarly causing it to retain the shape of the concave form. Unlike the first method, the entire top is domed, not just the area from the lower harmonic bar to the tail block. In this method, the bottom of the harmonic bars are arched to match the dome of the top. Builders who have adopted this method typically use a neck block instead of a Spanish foot, and the neck is attached after the body is finished using some form of dovetail joint or mechanical fastening method. Builders using this method typically give the neck a set backwards by a degree or two to align the plane of the neck with the rising dome of the top half of the sound board, so that they remain a plane surface to accept the bottom of a flat fingerboard.

Here is a picture of a typical fan braced classical guitar top, showing the harmonic bars and fan braces. Many small stringed musical instrument builders have also adopted this style, using 2 or 3 fan braces instead of 5 or more. In this picture the two harmonic bars and 5 fan braces are clearly visible. The 2 harmonic bars (running vertically in this photo) cross the top, one above and one below the sound hole, providing strength in this area. The combination of 2 harmonic bars and the fingerboard keeps the top rigid from the area of the bottom of the sound hole to the top of the guitar body. The small areas to the left and right of the fingerboard provide small high frequency resonators, but by and large the upper part of the sound board can be considered rigid and not free to vibrate. Every builder has developed his own top bracing method and there are many variations, but the use of fan bracing and harmonic bars is common, though there are exceptions. Steel string acoustic builders generally adopt what is called an X-bracing system instead of fan braces, but in this bracing style variation the top half of the soundboard is also held rigid by the fingerboard.

In practice, the energy from a vibrating string is transfered by the bridge to the top, causing it to vibrate and produce sound. But to be responsive it must be free to vibrate. Because the top half of the sound board is restrained by the harmonic bars and soundboard, it is the bottom half of the sound board that does most of the work. And work it must, because it must be free to vibrate while resisting the pull of the strings, which would cause it to collapse if they could.

Some builders view the top conceptually as a rigid plate suspended from the sides by a compliant area (the recurve, or thinner parts of the top near the edges). But if you look at Romanillos's analysis of Torres graduation methods, or think a little about the problem, you'll see that strength is needed in the top mostly in the area between the center of the bridge and the bottom of the sound hole, because this is the direction is which the static tension of the strings pull. So in this conceptual model, we don't just have a simple rigid top suspended by a compliant recurve, we have something that looks more like the reed of a stringed instrument starting at the lower harmonic bar and extending down the center of the top to the bridge area and slightly further, with a compliant recurve continuing around the lower bout to the lower harmonic bar, thus forming a diaphram centered on the bridge and occupying the lower bout of the top.

Lets look now at these two construction methods and their consequences. In the Spanish method, its very easy to establish a plane surface for the fingerboard. In fact, you must work hard to avoid it. In the second method, you must correctly set the neck angle or/and flatten the fingerboard after it is glued on. The domed method is very frequently found in a factory production setting where bodies and necks are being manufactured separately and assembled, though individual builders have adopted it. The simple concave forms used to shape the top can be purchased from suppliers in quantity, ready made. The Spanish method is found more commonly amongst individual builder who are responsible for construction of an instrument from beginning to end and who are interested in understanding the ways and methods of those who came before them and are willing to build a solera and experiment with its rich potential.

The Spanish method differs in an important way from the doming method in another regard, its effect on the sound of the instrument. If you imagine a cross section of a domed top just below the lower harmonic bar, you'll see that it is most arched at this point. If you look at a top built using the Spanish method, you'll see that it is most arched near the bridge and the area just below the lower harmonic bar is flat. This difference has very important consequences to the way the top behaves and consequently to the tone and sustain of an instrument. There is an optimum degree of compliance in this area necessary for the top to remain responsive and still retain the strength to resist the static pull of the strings. For any given compliance, a domed top must be thinner in this area than a top whose arch is highest near the bridge. And the smaller the doming radius used, the thinner this area must be to achieve this optimum degree of compliance. In general, doming of the soundboard requires thinner soundboards for optimum compliance than the traditional method of construction. I hope to find time in a future note to cover the effects on tone and sustain of these two different methods.

This is a topic about which there is much controversy. I hope that builders who use the domed method of top construction will take the time to think these remarks through and experiment with the traditional method of construction. There are fashions in all things, and doming is a contemporary fashion in some circles of lutherie. I'd advise anyone beginning upon this path of adventure and discovery called lutherie to explore the methods of those great builders of the last 150 years, learn to understand and appreciate their collective wisdom and the potential of their methods before chasing fashion or attempting innovation to something as highly evolved by many people over many many decades as the classical guitar and its smaller relatives.

While i'm making fingerboards for this set of instruments i'm working on, i want to illustrate how i taper the fingerboards once they have been slotted. Here are a couple of photos of another jig i made that i find extremely useful. This table slides across top of my shaper and holds work as it moves past the cutter head. Both ends of the cross rail are adjustable in such a way that it can form arbitrary angled tapers. Sliding clamps in the rail hold the fingerboard securely while it is being shaped. You can see it here in use tapering the edge of a fingerboard i just slotted using the method discussed in the previous note.

You'll find many such home made jigs in the typical small guitar maker's workshop. Jigs for fretting, jigs for shaping bridge arms, jigs for joining tops, jigs for cutting an arch on the bottom of bridges, jigs for cutting arches in back braces, all kinds of jigs.

Some ask if this use of jigs is consistent with the ethic of a hand made instrument. I have found that there are some things best done this way, and there are some things best done entirely by hand. I'd rather spend time graduating and bracing a top by hand then hand planing fingerboards. Most working luthiers that i've met would agree. But most of us have also spent a lot of time doing everything by hand when we first entered upon this path, and the knowledge thus acquired is essential to the appropriate use of jigs and such tools.

Accurate fret placement is essential to the accurate intonation of a fretted instrument and accurate intonation is essential to the musical quality of the instrument.

While i'm working on the matched set of Rio rosewood/Swiss spruce instruments i'm building (a classical guitar, a concert sized uke and a tenor sized uke) i took the opportunity to illustrate the method I use to produce fingerboards and accurately cut the fret slots.

Pictured to the left is a sliding table i constructed. Runners on the bottom of the base of the sliding table fit in the keyways machined into the top of the table saw, ensuring that the sliding table moves at exactly 90 degrees across the saw. The photos show an ebony fingerboard attached to a CNC machined fret template and an indexing system consisting of a steel pin resting in a holder clamped to the rail of the table. The steel pin has a tapered end which automatically centers in the small slots in the fret template. Finally, a specially machined blade .023" thick, the correct thickness for a fret tang, is mounted between two thick steel anti-vibration collars to the saw arbor.

In operation, the saw height is set so that it cuts the correct depth slot in the fingerboard, the fingerboard is mounted to the underside of the template using two small pieces of double sided adhesive tape, then each fret is cut by indexing the steel pin in the correct slot in the fret template, moving the sliding table past the blade, returning the table to the free position, lifting and reindexing the pin to the next slot on the template, and repeating. The template shown here supports two different fret scales, 650mm and 660mm, but many other fret scales can be cut by choosing an appropriate starting point on the template. I'm using a 385mm scale for the concert and a 430mm scale for the tenor ukulele. All my classical guitars use a 650mm scale.

This system ensures that the frets are cut in the fingerboard with the same accuracy with which the template is made. These kinds of templates are produced and sold by luthiers supply houses like LMI and StewMac and are widely used in the luthier community. I've cut many a fingerboard by hand in my day, and still have the set of Starret satin-chrome rules marked in hundreds of an inch i used for layout, but this system produces the very best accuracy, repeatably. If you are starting on the long path of adventure and discovery known as lutherie, you are well advised to consider adopting a system like this.

Here are some photos of version 3 of the Chantus model A4 concert ukulele. This ukulele follows #1 and #2 illustrated earlier in these notes and is the latest step in my attempt to design a standard product offering of a concert sized ukulele. These photos show the ukulele in position on the solera surrounded by the body mould. I'm ready to glue the back linings in. The construction features an arched and graduated top of fine Swiss spruce resawn from a master grade violin top blank and Rio rosewood back and sides. The neck is Spanish cedar and the fingerboard will be ebony. The rosette is ebony and holly. The headstock has a frontplate of rosewood and a backplate of cherry wood. Version 3 of the A4 has a slightly different body shape with a less wide lower bout and the top is braced and graduated differently.

Here are some quick photos illustrating the joining of a few tops and backs using a method which is traditional, simple and effective. And its iron clamp free ! I've discussed this method in an earlier entry in this journal. Its one used by Japanese craftsmen to join large thin panels of wood used for sliding doors. These are rosewood backs and spruce tops for a concert and a tenor ukulele. The third photo shows them leaning against the solera i use to construct a concert sized ukulele, drying in a corner of my workshop.

The original note i wrote describing this method of joining tops and backs can be read here.

If you are in or near NYC, call Beverly at The Guitar Salon on Grove Street if you'd like to see and play #34 - my most recent instrument - a classical in Madagascar rosewood and Swiss spruce. Thanks for the click !

As part of my uke project, i'm evolving the design of a concert uke that i can build as a standard product offering. The design process starts with a sheet of paper and ends with a new version of the model A4 concert ukulele.

I thought it might be interesting to document this process of design and construction with a series of photo essays. I'm working on version 3 of the model A4 right now. Check back for a few notes on this process.

I've had a busy few of days since last writing. I joined a top for #35, a classical in Rio rosewood and Swiss spruce.

I joined 3 spruce fronts, one for a classical guitar, one for a concert ukulele, one for a tenor ukulele. For the two uke tops, I resawed a master grade Swiss spruce violin top wedge i've had for a while. Its been hand split from the log, air dried, has a pretty uniform 25 lines to the inch across the entire top, zero runout and a fine creamy white color. Its extremely light and stiff, which makes for a very responsive and detailed sound. Its a one of a few pieces of wood my supplier selects each season as meeting the highest professional grading standards, their 'master grade'. The classical top is an AAA gradeSwiss spruce top from the same group of sets as #34.

I also joined 2 Madagascar rosewood backs for the concert and tenor. I'm building a matched trio of instruments, a classical guitar, a concert uke and a tenor uke in Swiss spruce and Madagascar rosewood. I'm hoping to have the set ready before the new year.

I also built 3 necks from Spanish cedar, two concerts and a tenor, with nice Madagascar rosewood head plates. Ebony fingerboards will look elegant against the spruce. I also got out a Honduras mahogany classical neck blank i made some time ago for finishing. The heel and spanish foot need carving and the headplate made.

I also joined a nice set of figured American black walnut for a concert back. I think this one will have a cedar top. Lastly, I resawed and thickness planed some ebony and cypress for several rosettes, one for the classical and one each for the concert and the tenor.

Stay tuned. I'm in the process of taking all this incomparably beautiful wood and building what i hope to be an exquisitely sounding set of instruments.