Tuesday, November 23, 2010

Closing the Box

Here we have the finished interior. In this instrument I've used "tenelones", or individual glue blocks, to secure the top to the sides. This is a technique borrowed from traditional Spanish practice which works well when a "solera" or dished workboard is used. In my experience there is also a palpable sonic difference in guitars constructed this way vs. the use of continuous kerfed lining. It's not so much that the voice is different, but there seems to be an immediacy to the sound.
In any case, I've used the kerfed lining on the back. This is Spanish cedar, by the way. It costs a little more, but it imparts the most wonderful aroma when one holds one's nose up to the soundhole in search of a lost plectrum.
I've doubled up the tentelones in the lower bout where I intend to install a wide chamfer for forearm comfort.
I'm trying something different in this guitar, using douglas fir for the top and bottom blocks. I got the idea from watching Robert Bennedetto's archtop construction video. I was surprised to find that he often uses spruce for his blocks. Since I had appropriately sized offcuts, I decided to give them a go. For my steel stringed instruments I've settled on a bolt-on neck attachment system. I've tried dovetails, straight tenons, and various bolt configurations. I like to make things easy for future repairs.
There are a number of different ways to close up the box. I often use rope. In some cases I've used go-bars. Today I had my box of spool clamps handy.
Spool clamps are a holdover from violin construction. They're a low-tech solution. They're also indispensable for repair work if one is trying to fix cracks in the sides, or if you've removed a top or back for interior repairs. At the top of the upper bout you can see a brightly coloured smear. A hairline fracture occurred during bending, which has been stabilized with thin superglue.
I suppose the alternative would be small quick-grip trigger clamps, but I'd need $1000 worth. I made these up from theaded rod and closet pole for less than a dollar apiece. They provide just the right pressure. A slightly oversize through-hole means they can pivot to accommodate the back arching. Cork lined surfaces prevent marring.
Front view. This illustrates a subtle little thing I've learned through experience. I've left the soundhole rough, and won't complete it until just before the finishing process. This ensures it will be clean, and any little dings or divots incurred via clamping the fingerboard in place or fretting will be sanded away.

Monday, October 25, 2010

Bending Sides

Time to bend some sides. For this instrument I selected some Honduran Rosewood I've had seasoning for quite some time. It's pretty hard, and it has an almost glass-like tone when I knock on it. I've planed and scraped the sides down to slightly more than 2mm (.085"thick). I'm comfortable bending things by hand using my electric iron, but it's much faster to use this bending fixture I made. The form is glued up from MDF board and the pattern has been reduced in size to account for the thickness of the sides and a silicone heating blanket.

At one time I had the more traditional "Fox bender" setup where the sides were sandwiched between metal sheets and a veneer screw put pressure on the waist. It was heated with 150watt light bulbs. I was never really happy with the results it produced.
My current bending system just relies on some gentle pressure from my hand on a block of wood. It takes less than two minutes to get things clamped in place using the threaded rod and knobs. I dampen the side slightly with a sponge and clamp it fast at the bottom, then apply pressure, moving forward to the waist. The heating blanket is draped lightly over the upper bout and it slides down into the curve with no problem at all! When all is in place, I turn off the heat for about ten minutes to cool down, then turn it on again for a further five minutes. This seems to set the bend a little better.

Here's my steel-string mold, with an attachment I screw in place for the cutaway. The side is clamped in while still hot, and it seems to relax into shape. I use springy maple slats (reject lute ribs) to hold the sides in place, sometimes with the help of F-clamps. There's a nice snug fit.

Monday, September 27, 2010

Some bracing work.

It's time to brace up a steel-string top. I rely on the tried-and true X-bracing system. Here, I've glued the supporting members above the soundhole. I don't play around here - these are large in dimension and made from the stiffest spruce I have in my stockpile. So much of the guitar's longterm stability relys on the support system that carries the fingerboard and transfers force to the sides of the instrument. My x-brace however, tends to be a little lighter than the typical factory instrument. When coupled with adequate design, this will increase the output and sustain. A delicate balance is required. I pay very careful attention to the interlocking lap joint which occurs at the intersection of the X. This has to be perfect.

I shape the X brace by paring away at it a little at a time. I use auditory information to help arrive at the proper dimensions. Before doing this work, I'll put on a pair of hearing protective headphones for an hour. All extraneous noise is eliminated from the shop. I want to be attuned to the task, my sense of hearing at it's optimum. I excite the soundboard with this little mallet I made from a superball and a stick. It gives me a more uniform and repeatable tone than my knuckle. I don't tune the top to a particular note - what I'm looking for is a certain clarity and complexity to the tone when I tap in various areas. This is augmented by using my thumb and forefinger to gauge the flexibility of the top. At a certain point, I'll get the impression that the top is flexible enough to provide good projection (without being floppy), and will have arrived at it's optimum response sensitivity. This is different for every guitar.

Following the shaping of the main braces, I'll glue on the secondary bars. This is all done in a special shaped carrier I made for my go-bar deck. I don't use a spherical dome, as is so often the case. The spherical design is an excellent aid to speeding production, but I prefer to graduate the degree of arch in the soundboard from nearly flat at the fingerboard end to a gradual arch of about 1.5mm in the center of the lower bout. I see no benefit to the severe doming employed by some luthiers. Some degree of arch is necessary of course, to alleviate of the tendency of the soundboard to crack in dry weather. The arch also counteracts some of the deformation caused by string pressure. The scalloping in the main braces below the soundhole allows a greater degree of sensitivity. I definitely strive to make the top much more flexible as it approaches the area of the sides. This produces a larger active vibrating area, which in turn gives us more volume.

Saturday, September 11, 2010

Staking his claim

This little creature has been visiting every day for the last week to check on progress. He/She has definitely picked out a favorite instrument for napping on. Puns abound. Perhaps it wants to play "Cat Scratch Fever", "Cat's in the Cradle", or simply holler, "Go Cat, Go!" before tearing off into a wicked four bar rockabilly solo. Dunno. But one look in the eyes, and you know you'd better keep your hands off that guitar.

Friday, September 3, 2010

Weathered Electrics

Here's the beginning of a project that I don't expect to see completed for quite some time. I had a bit of a trans-cendent vision when driving back from the Lute Society symposium in Cleveland this summer. Passing countless farms and fields I was struck by the wonderful colors and textures present on the fence posts and barns. It solidified an idea I've had brewing in the back of my mind for a while.

I've always been attracted to objects that show a heavy patina from use and age. The leather of a well worn baseball glove. The polish that develops on a tool handle from much use. I'm not much of a fan of modern synthetic finishes and their bulletproof gloss that locks wood away in suspended animation. In thinking about music and what it means to me, I'm reminded that it's the human quality and variation that makes it exciting. In a world where AutoTune can smooth and polish the human voice into robotic uniformity, I cling to old recordings and live music to grab hold of something inherently truthful.

A while back I recall reading about a guitar that had been commissioned by Billy Gibbons of ZZ Top fashioned from a plank taken from the walls of a ramshackle cabin that was the birth place of blues legend Mckinley Morganfield, aka Muddy Waters. "How exciting!" I thought. The emotion was immediately replaced by a feeling of real disappointment when I finally saw the instrument. I was picturing a weathered gray body, fissured and cracked, bleached by Mississippi sun and scoured by floods and rain, a real embodiment of the place and conditions where the blues was born.
Instead, luthier John Bolan had produced a slick looking white guitar, with racy pinstripe and rockstar-ready shape. I'm sure it sounds great.

I purchased a beautiful plank of quatersawn Douglas fir. I know that Doug fir is a staple in dimensional lumber used for house framing in western parts. We don't see much of it around here. For our framing, spruce is the mainstay. Douglas fir is incredibly tough stuff for a softwood. It has a neat texture.

I glued up blanks using Gorilla Glue, a polyurethane adhesive which is excellent for outdoor projects. Waterproofing is important, given the treatment I'm going to subject it to. My choice of body shape hearkens back to the first mass-produced solid body electric, the Fender Telecaster. I've made a few small stylistic changes to the shape. Also, I've never understood why Leo never went back to update some of the comfort issues he addressed in the later designs. I've gone ahead and increased the radius on the edge and planed a relief chamfer where the forearm contacts the body.

And now, into the gravelled area of our back yard which at one time served as a dog run. I've let it go fallow for two summers, and it's become rather untamed. I'll let them sit there, turning occasionally, to soak up sun, rain and snow until I feel they're properly aged. (Interestingly, this hearkens back to the days when I turned bowls. Unsuccessful examples occasionally went outside for a few years to weather, and they ended up looking great!)

Sunday, August 29, 2010

Making an inlayed rosette, Part 2

Scraping is finished when the ends of each line appear square and the pattern looks okay. To ensure accuracy it works best to cut the rows into short lengths about 6" (150mm) long. These are easier to press together and the pattern stays more regular. I'll now repeat the gluing operation to make a little block from which I will saw tiles about 2mm (0.085") thick.

I made a rudimentary diagram showing the dimensions of the soundhole and the channel I'll need to rout for the inlay. This rosette will be about 5/8" wide, which will make for a dramatic statement. I decided to make it two-toned, black and red for visual interest. Each tile displays its own little variations. They definitely don't look machine made, and I like that. Why go to all the time and trouble to make this kind of thing when mass produced ones are available and cheap? I guess there are just some things we have to do that defy rational thinking and economics. Things that make life interesting.

Here's my template. This instrument will be similar in size to a Martin OM, just over 15" wide at the lower bout. I've chosen to include a Florentine style cutaway and that means I'll make some slight changes to some dimensions to make up for the loss of interior air volume this creates. I'll increase the body depth by 3/16" (4mm). I aim for a balanced output that couples power with lots of tone color.
The Sitka spruce top is one I got from David Freeman at Timeless Instruments. It has lots of character, with patches of bearclaw figuring. It's nice and stiff and even at this early stage it produces a complex set of sounds when I tap on it.

The template is 1/8" (3mm) hardboard and I've drilled positioning holes to poke a pencil through to mark brace locations and the cutaway. It's also wider than necessary to allow me to vary the width of the instrument by as much as 1/2".

My wife jokingly describes much of my working practice as, "getting jiggy with it". Now, -I actually use more hand tools and less machinery that a good many luthiers, but it's true. Guitar makers spend an inordinate number of hours creating devices designed to save a few minutes. Here's a $3 router compass made up from some hardboard, a wing nut and a dowel.

I hand planed the top just enough to clean up the surface. No matter how careful one attempts to be, it's easy to put scratches in with the router compass and inlay procedure. Also, the large volume of glue involved can cause the top to expand if it's too thin. To prevent any misalignment I went ahead and partially routed the soundhole. If I left it until afterwards, it's likely that the rosette would appear oval. Rout them at the same time and everything expands and contracts together. I didn't cut all the way through because I'll be hand planing the top to final thickness from the other side, and it's just easier if the hole isn't in the way.

The bordering lines are individual strips of veneer, 5 strips on each side. BBWBB The black strips are actually the result of a dying experiment gone slightly wrong. I didn't get complete penetration to the core so when they're planed down I end up with a complex grayish-black variegated appearance. The first time I used them I cursed, looked again and realized I really liked the effect!

Here's a little tip - by having the strips as individual lines rather than prelaminated, and not gluing them in place (they're dry at this stage, just held lightly in place with the pins), I've found I get a much tighter finished product. After the tiles are in place I'll wet the whole thing down really well with thinned glue. It seeps into the cracks, the lines all expand and everything sort of melts together.

The tiles as they are cut from the block are close to square in cross section. A slight angle is necessary to keep the pattern centered and prevent gaps. It's not necessary to belabor this! Just grab a wide chisel and do it by eye. Again, the slight variety is what makes the whole thing come alive! The regularity of machine precision ends up being visually static. Having the slight irregularity in the spacing and angle gives the characters a certain optical illusion. They seem to be moving across the colored background in a kind of dance.
I put a dab of glue on the bottom of the channel, and on the side of the adjoining tile before nestling things in place with the end of my brush. Any little spaces will magically disappear when the glue expands the veneer.

After brushing on a really thick coat of thinned glue (still using the yellow aliphatic), I let it dry thoroughly before planing things level. There's one little spot there on the treble side where the white line split and flaked off below the surface. I've been using some dyed white maple, but it's got some figure in it and tends to be a bit chippy. No problem. I'll just scarf in a little patch and it'll be invisible. The entire surface gets coated with thin superglue to seal off all that end grain even further and make it less likely to absorb dust or dirt in the interim before I apply the finish.

What does one do with the inevitable leftover tiles? You can pair them up with the scraps of ebony that every luthier can't bear to throw away. They make good tags to put on the key chains for a lockable guitar case. Or you could make jewellery for rebellious youth. A little time with the sandpaper and I came up with these vaguely plectrum-shaped forms.

Making an inlayed rosette, Part 1

I've started work on a new instrument this week, a midsized steel string. I intend to follow the construction closely with frequent blog updates!

Here I'll describe my process for making the traditional Spanish-style mosaic inlay used to decorate the soundhole perimeter on classic style guitars. I've scaled the size down a little to be more in keeping with the steel string aesthetic.

I credit this entire process to master luthier Eugene Clark, who's method was detailed wonderfully in the Journal of American Luthiers, issues 71 and 73.

My rosettes are constructed from strips of veneer (0.5 mm/.025" thick). Some of these I buy in sheets ready dyed, others I color myself using aniline stains cooked in a big pot on the stove, not unlike spaghetti, but even more al dente'.

I've devised some interesting jigs to cut the strips. In the end I came to the conclusion that by just making little pencil marks and going at it with a wooden straightedge and sharp knife, my eye quickly becomes adjusted to gauging the size. It's much quicker and accurate enough. They end up about 2mm wide, a convenient size to work with. Eventually they'll be scraped square in cross section.

Traditional steel string instruments often have designs made up of concentric lines- a quick and easily accomplished solution for the factory. Early Spanish luthiers often employed geometric or floral patterns. Eugene Clark associates the design process with weaving and textile arts. To me, it feels more akin to the Italian art of Millefiori glass.

The pattern options are boundless! As individual craftspeople we have the opportunity to be a little more personal with the motif. I'm using this little character here, a skull figure that in this format has a definite old-school Space Invaders aspect. (Yes, I know there's no nasal hole! Don't ask me why - that's just the way it is!)

I plotted the design out on graph paper and transcribed the squares of color into a sequence to assemble the lines into individual rows.

Having a big sink nearby is important. It's a messy business. The top of the washing machine becomes a ready made workbench! I'll be using yellow carpenter's glue as an adhesive. The laminate workboard has a piece of hardboard screwed down to make a straight fence to press against. It's hard to see, but the edge has been covered with clear packing tape to provide waterproofing.

I'm not stingy with the glue. It's important to get every strip thoroughly saturated. The glue has been thinned with a small quantity of water to extend the working time. I cover five or six strips at once and line them up. They are then squeezed lightly between thumb and fingers and excess glue wiped off before adding more lines to complete one row of the pattern.

A couple of thin Plexiglas sheets provide a light, even pressure to hold the now assembled row straight against the fence. The surface of the workboard and fence has been slightly dampened to prevent the row from sticking too firmly, but also to provide a little surface tension to hold the plexiglas down flat on the board. The five minute interval required will allow the glue to seize up before I run a pallette knife around the row to free it. The next row goes in, and the previous row gets set aside to dry.

The rows have now been readied. These are about 12", (300mm) long. This length is easy to work with and cuts down on the incidence of breakage during the thicknessing process.

Rough thicknessing proceeds with a block plane. I hold the rear end of the row in my hand - there's no safe means of butting the row against a stop block as it's too thin and would bend or break.

Planing yields a big fuzzy ball of gore.

This is an old #90 Stanley shoulder plane in bullnose con-figuration clamped to a maple block at close to 90 degrees. The rows are slipped between the blade and fence at a point about 1/3rd their length and pulled (carefully) toward me. I then reverse the strip to scrape the other end. As I started with veneer 0.025" thick, that should be the final thickness of these strips to ensure the ends will as tiny squares in the finished product. Work progresses by advancing the blade in very small increments, flipping and rotating occasionally to ensure even stock removal, and eventually things get done. It takes some time, but it's a good opportunity to reacquaint ones'self with an old album, in this case it was Muddy Waters' "More real Folk Blues".

Wednesday, July 28, 2010


Today I completed bridges for two instruments - the current 7 course Renaissance lute and the replica Stradivari guitar. I decided not to photograph the actual carving procedure, as it simply involved using a knife to remove everything that didn't look like a bridge. The ebony and bone overlay on the Strad was a fiddly bit of business. The European pear carves so nicely, almost as if it has wax incorporated somehow in the grain. The fun part came when I drilled the string holes. I have in my possession a Black and Decker drill from the late '50's which is wonderfully precise, and has a Jacob's chuck that will hold a 3/64" bit. I weighs twice what a modern cordless does, it's geared very fast, and it emits an interesting ozone smell when used for long periods. Perfect for this job.

Thursday, July 22, 2010

Making some points

Today I am fitting some points to a lute body. Here are a couple of pieces of ebony which I've planed to the appropriate thickness and taped together to encourage symmetry in my carving. I drew a little arc for guidance, but it's only a rough indication. I'm just aiming for an interesting curve.

My pride and joy. This is the sharpest knife I've ever owned. It's a small slojd pattern forged for me by Del Stubbs http://www.pinewoodforge.com)/
It's capable of powerful shaping cuts, but the tapering design allows for really delicate work too.

A couple of swift carving motions leaves this result. I'll use some thin double-sided tape to fix these in position and trace around with a fine pencil.

A scalpel blade ensures a clean cut. I aim to bisect the pencil line down it's centre. The little "o" is a reference mark to keep track of which piece goes where.

When the glue (fishglue in this case) hits the freshly cut spruce, it will swell the fibres just a bit. A little firm pressure is sufficient - they don't need to be clamped down. It's hard to make out in this photo, but I've left the spruce in the area of the top block just a bit thicker than need be. I learned this one the hard way- it's much easier to scrape it down to the level of the points than vice versa. Cleaner too, as the ebony dust loves to lodge in the pores of the spruce, leaving a dirty grey appearance.
The ebony fingerboard overlaps the sides of the neck by a small margin to allow me to blend the curve later in the final scraping. Note the arrow indicating grain direction near the nut. It's another precaution to make sure I don't end up crushing black dust into the lute's face during leveling and scraping. I'll press a couple of tacks in place at the nut end to keep the board pressed firmly against the points.
Surgical tubing. It's the most positive clamping system. Robert Lundberg apparently used a series of laboriously shaped cauls, which I find interesting - given that he used rubber strapping to glue on neck veneers. Strange.
Here's another instrument on the go these days. It's a five course baroque guitar. Points originated as a pragmatic solution to to cover up repair and alteration work as larger necks were grafted to old instruments when more strings were added. Interestingly, by the time the inspiration for this guitar was fashioned in the early 1700's, they had become a design convention and were fitted to new instruments at the time of their construction.

Thursday, July 15, 2010


I have yet to find a manufact-urer in North America that produces lute cases. The only options for a novice builder on a budget seem to be limited to ordering a beautiful (and costly) custom case from England, making do with one of the accessories designed for the so-called "student" lutes imported from Pakistan, or to construct your own.
I decided to take a shot at the latter. The material I'm using goes by the trade name Sintra. It's a medium density expanded PVC used in the sign industry. I recall experimenting with it in art school. It bends readily with heat, is very stable, durable and pretty inexpensive. I envisioned using this handsome mold to heat-form the case sides. As it turned out, the mold is unnecessary! I found it easier to just use a drawing for reference angles.

To effect the bends, I clamped the Sintra in place over a board and applied gentle pressure using a piece of scrap wood to keep the line of the bend square. It doesn't take much heat! Sintra has gained a following among the strange subculture of Star Wars aficionados who like to dress up in storm-trooper armor. There are several excellent YouTube videos of fans molding the various pieces necessary to become Boba Fett. All very entertaining. I'm working with 6mm material, and it has the right combination of stiffness and weight.

A quick check with this ancient ebony and brass bevel. You can see that the Sintra has compressed slightly on the inside corner and taken on an attractive radiused appearance on the exterior.

It's possible to correct overbends while the material is still warm by gently coaxing it. I left the ends long, marked the case center line on them, and trimmed them to fit. The joints were reinforced with a strip glued on the inside. I planned the dimensions so that one case would accommodate a number of lute patterns by adjusting the padding and neck support placement.

I used regular plumber's PVC pipe adhesive to join things together. This substance is nasty! In fact, it's so toxic that although I worked outside when gluing large areas and used a respirator, I think next time I'll try a slow cure epoxy instead. To be clear: this is just a demonstration of my method. If you decide to replicate it you do so at your own risk and I will not be held responsible for any damages! Do not put your health in danger.

Here I'm clamping a secondary thickness in the area where the piano hinge will go. Similar reinforce-ment is placed under each latch and the carrying handle. I fastened the hardware using small 1/8" round headed bolts, with washers. I wasn't sure I trusted the Sintra's capacity for holding screws.

With the top and bottom glued in place I used a bearing guided roundover bit in my laminate trimmer to clean up the edges. A block plane worked well to remove the bulk of the overhang. Even with a vacuum hose held close to the bit, there was a whirlwind of plastic fuzz everywhere! The green tape was a precaution to keep the solvent-based adhesive from spilling and staining the case walls. Speed is of the essence and it's hard to be neat. It's best not to slow down the feed rate of the router, as the Sintra can melt if the friction becomes too great.

I used a standard woodworking marking gauge to delineate the parting cut between case top and body, then finished up the job with repeated knife cuts -which are remarkably clean. All in all, Sintra is a very friendly material to work with.

I'm fortunate to live close to a specialty foam supplier. I lined the case with some 1" closed cell foam and adhered it with a hot glue gun. This was a fun experience, but it took about a day's labor. Also, it's not nearly as classy in appearance as the Kingham cases. The materials amounted to about $100. It seems there really is no such thing as an inexpensive lute case.

Wednesday, June 16, 2010

Go-Go Gadget Go-bars!

I'm gluing braces today. Go-bars are one of the idio-syncratic tools developed by luthiers to facilitate clamping with minimum headache. Given that the soundboard is so thin, the spans long, and the assembly awkward, the go-bar deck is an elegant solution.

My go-bars are salvaged strips of glass-fibre reinforcing. They appeared one day at Lee Valley Tools for sale on the "scratch and dent" table and I grabbed a bunch at $.75 a piece. They're not a regularly stocked item. Here I'll be gluing the treble bars. You can see that I've already got the bass or "J" bar in place.

I dab on the glue and press a bar into position, flexing it between my purpose-built table and the bulkhead above. The bars provide firm, even pressure. Another nice feature of this system is that the intersecting corners remain free and clear for me to get a chisel in there to remove squeeze-out.
Luthiery buffs who specialize in guitars might note that the grain in these braces runs parallel with the soundboard, contravening modern wisdom. This is historically accurate. Surprisingly, there is little difference in stiffness over a given span between this orientation and that of vertical grain assuming bars of similar dimensions.

I suppose the early lute makers would have used weighted blocks spanning several braces, or perhaps they simply relied on a "rub joint", where the bars are pressed into place with a little sliding motion and held until the hot glue seizes and begins to gel.

I like the way the deck looks when the bars are set up. It's a neat piece of sculpture.