Soundboard

A flamenco top in progress.  It's a five-bar pattern with an angled treble brace and no "cut off" bars near the tail block. I found that leaving these off adds a certain raucous quality to the overtones that seems in keeping with the spirit of flamenco. The barring above the sound hole is quite robust. I run the transverse bars at full height right across, without scalloping.

Thicknesses start at about 2.4 mm in the vicinity of the bridge, thinning to about 2.1 at the periphery.

One thing I've learned from looking at older instruments is to leave a little space between the end of the bars and side. The box of a guitar is apt to shrink a little bit over time. The top and back can contract, but the transverse bars don't shrink much at all, oriented longitudinally as they are. If they butt right up against the sides they inhibit the contraction and can cause cracking.   I store my materials carefully and build in a controlled environment but one never knows what humidity conditions an instrument might find itself subjected to during its lifetime.

Some Rosettes.

I recently spent some time making and installing rosettes, and I've updated my methods a little with some high-tech gadgetry since the last time I outlined my procedure.  Here's a little compass cutter I use to outline the channel.  This produces a much cleaner margin than simply plowing through with the router.  The scalpel blade is compressed by a block simply screwed to the beam. It rides right on the surface and cuts to a depth of 2mm.  There is a 1/4" (6mm) pin which protrudes through the soundboard and into a bushing housed in a workboard beneath. This makes adjustments really precise.  A bolt ties the beam to the platform with a plastic speed-knob. Simple, and it works like a charm.

A similar setup serves to adjust my laminate trimmer.  You can see that I set the cut about a millimeter away from the knife line. Depending on grain direction, in some places the residual material gets blown off by the force of the router. The stuff that remains is easy to pare away with a chisel.

I've followed Eugene Clark's method for rosette construction for some time, including the use of waxed spacer lines to take the place of border and tile elements.  That makes for a lot of work -cutting an extra 20 veneer strips, waxing each one, etc., and they're not reusable!  I thought I'd try some of this UHMW (Ultra High Molecular Weight) plastic sold through various woodworking suppliers as jig-making material for table saw miter tracks.  It's durable and glue does not stick to it at all.  I ripped pairs on the band saw in increments of 2, 2.5, and 3mm, color coding them and trimming them to length to fit into the rosette channel.

Border material is cut on an angle in a tiny little miter box sized to fit my fine backsaw.

The plastic strips pop right out, and the tiny little pieces are glued in the resultant channel.

I've decided to keep things simple and bold.  I've been looking at a lot of rosettes recently, and coming to some conclusions.  I think I'm most attracted to the early Spanish designs which rely more on geometric patterns than pictorial representation. In the one on the left, in fir, I made the border quite large.  It seems to me that there are two trends in modern classical rosettes - one being the use of spalted or other highly figured woods as a focal point, the other being extremely detailed mosaics.  To my eye, they seem out of proportion to the instrument as a whole and get completely lost unless you happen to be right up next to them. A position neither the player or the audience is likely to find themselves in.  Though I'm fond of spalted wood, I'm not eager to jump on that bandwagon.

There's a quality of mechanized precision to most of the commercially available rosettes that I think is at odds with a handmade aesthetic.  I like the little irregularities this process imparts. They're not jarring, but they do add a floating quality, and visual movement.  It takes quite a while to make one of these things, but there's a kind of novelty to the process.  It's contemplative. In the example on the right in red cedar, I decreased the size of the border and flip-flopped the border tile (made from the exact same veneer lamination), and it creates a significant contrast. I thought the larger field of pearwood might echo the color of the cedar in a pleasant way.

(These photos were taken after scraping the surface level, but prior to sanding or the addition of finish.)

An Update

For the last couple of weeks I've been busy preparing a small storefront to act as an office/meeting place to establish a more visible profile in the Hamilton music community. Recently, we were able to find a place in a nursing home for my mother and I've regained some freedom to pursue my creative endeavors.

Currently, I have classical and flamenco guitars on the go, and I'll document them when they're closer to completion.  I realized recently that I have very few photos of finished instruments on here. I hope to redesign woodfordinstruments.com and turn it into a profile and presentation page which will maintain a link to this blog.  If you have this page bookmarked, you might be redirected.

It's a busy time.  I apologize if I haven't responded to your comments recently -I haven't been checking in with much regularity.  You can always reach me via email: ted@woodfordinstruments.com.

To the Extreme! Adventures in Neck Setting. Carson J. Robison

Sometimes repair brings surprises.  I recently did some further work on the Carson J. Robison guitar that I discussed a month or two ago. "Can of Worms" might be a better title for this blog.
Let's start at the beginning.  The action is the highest I've ever seen on a real guitar.

I, like most North American luthiers, tend to describe action in terms of 64ths of an inch. This, gentle reader, is a stiff action. 14/64". A full 7/32"!  The owner of this instrument plays slide, and I decided to get confirmation from him as to what we should be done. He asked if it was possible to lower it to within reasonable levels, and I agreed to do a neck re-set.  I spent some time doing the trigonometry and realized that changing the neck angle this much would remove a huge amount of material from the heel. I reasoned that it would be possible to insert a filler under the fingerboard extension to alleviate some of the problem. More about this later.

It's important to protect the fragile finish on the top from heat damage, so I made up a mask from heavy card. The tongue of the fretboard was heated using a regular household clothes iron.

Releasing the tongue was easy. You can see I added several layers of masking tape to insulate the area I didn't need released, and to protect the old plastic dot inlays.

While the 15th fret was still hot, I pulled it up. There are several ways to do this, but I like to use a thin chisel.  Having pressure against the board as the fret is pried up seems to keep chip-out to a minimum.

Pretty clean.

To reach the space at the end of the dovetail, one needs to approach it from a slight angle.

On Martin guitars, and most modern factory-made instruments the neck is finished separately from the body. This guitar was assembled before spraying. I would later find a lot of filler in the intersection between neck and sides. The dark stain hides the less-than-fastidious fit.  It's important to score along all the seams with a sharp blade to prevent as much damage to the finish as possible.

Here is a shop-built tool for applying steady pressure to the heel as steam is injected.  This is where where the fun begins.  I applied steam in the usual doses and cranked a little.  Nothing happened. I let it go a little longer, -still nothing.  I worried about letting the guitar get too hot, so I cooled it down and wiped off any moisture before re-trying.  Still nothing.   I tried using a mallet.  It didn't budge at all! (In retrospect it was lucky I tried this operation with the guitar all clamped up like this. Too much steam could have loosened the joints between the plates and side assembly.

I was stymied.  There was no reason for this to be happening!  I've taken the necks off a dozen other guitars, mostly Japanese dreadnaughts from the 70's and the odd Harmony.  This instrument was definitely put together with hide glue. What was the issue?

Something jogged my memory and I went searching through my archives.  I found a reference to a specific group of Gibsons in an old issue of the Guild of American Luthiers journal....

This guitar was shipped out of the Gibson workshops in 1936. What were the odds?!   I informed the owner and advised him that I would have to go oldschool and cut the tongue free.  Nobody does that anymore. It's a technique from an earlier time. It's not nearly as clean, but there seemed no way around it.

Suspicions confirmed -but it wasn't so easy. I cut the fingerboard extension off and revealed an unsullied soundboard surface. A little excavating revealed the dovetail pocket.  I had access to the cavity and steamed it for the fourth time. Still no luck. It refused to come free. If you look closely at the pocket above, you'll see that it was cut using multiple passes from a table-saw blade. (What a laborious way to do things - imagine being that guy who had to stand there dragging the same chunk of wood over the blade 15 times...)  This was not a fancy guitar. It was put together with haste. Its original price of $9 was roughly a quarter of the cost of a similarly appointed "official" Gibson. That included a case and a harmonica.  If you look closely at the top of the dovetail cavity you'll see it's really chewed up. The fibers have been squashed.
This thing was literally hammered together.  There was no neck "angle" originally. The neck and body were in one plane. No time was spent finessing the attachment. In engineering terms it's what might be called an "interference fit". The angles weren't quite identical, and with the addition of some glue to swell the wood - there was no way it was ever coming apart. I figured this out when a hairline crack started to appear on the heel surface. That did it.  Out came the finest Japanese flush-cutting saw, and I cut the neck free, leaving the dovetail in situ. I cleaned it out using a chisel.
(Sorry I didn't take a photo of the sawing. At that point I was a little exasperrated!)

I was seriously tempted to drill some holes and turn it into a bolt-on.  The purist in me knew that wasn't the way to go.  I pulled out a dovetail template and cleaned up the cavity to make it square and regular. I then found a suitable piece of mahogany and carefully laid out a tenon to mate with the now pristine mortise.

It took some time to get the fit just right. I then sanded the heel area, removing a wedge of material to effect the angle correction (as much as I dared). Getting everything lined up, I applied epoxy to the tenon and stood the neck upright on it, making certain that it aligned properly with the bridge.

 When the epoxy cured, I could then remove the neck from the guitar and drill for two large screws to really secure the tenon to the heel surface.  The joint is side-grain to end-grain - not ideal, so I also drilled for a large dowel, which was then cut flush.  I felt satisfied that this arrangement would remain secure.

Usually I like to see a straightedge lying on the surface of the frets land right on the top of the bridge, that way any action adjustment falls within the dimension of the saddle. In this case it's a little high -this is very low bridge, and I don't believe it's ever been planed down. In doing the math, it seems certain that the guitar left the factory with an exceptionally high action.  Marketed for strumming cowboy chords, I don't think it was designed to be played beyond first position.

The only way I could get things in reasonable shape was to use a shim of rosewood under the fingerboard extension. Without it, the board would drop off precipitously over the body, but it also allowed me a 1/16" "boost" to get up close to the string plane.  I still shaved more than 2mm of material from the distal end of the heel.  I would have made the fingerboard shim even higher, but I didn't want to pull the heel up past the edge of the back:

There's now a little step down to the heel surface where before it was flush.
There was also a lot of finish touch-up. The steam softened things a little in various areas. I used shellac and french-polished it along with alcohol dyes. The effect is okay. It's hard to know when to stop. This wasn't a refinishing project, after all.

I managed to reduce the action by almost 6/64".  Remember that any numerical change at the 12th fret is doubled at the bridge, so we're talking 3/16"(almost 6mm) theoretical change in string height at the saddle! That's *huge*.  You can see why the booster-shim was necessary.

This is the original saddle. It's glued in. Deep notches had been filed into it to lower the strings a bit, and the blank was very square and pointy looking.  I filed off the extra bone and gave it a more graceful profile, but didn't have to change the height.

What an experience.

Carson J. Robison, Part 2.

What should I clean my guitar with?    I usually suggest one of the proprietary cleaning polishes available at any music store. (Never use furniture polishes like Pledge which contain silicone. Silicone is bad news.)  For the relics coated in goo, naptha lighter fluid is the best choice and use only Ronsonol brand, if for no other reason than it was the one employed by Jimi when he burned his Strat at Monterey Pop.

The pickguard crack needs to be bulldozed clean. Using a scalpel blade upside-down, I pull out any dust and also gently compress the sides of the crack so it's slightly V-shaped in section. The spline will also be shaped to a taper. When moisture is absorbed from the glue  it will expand and lock things tightly in place.  For spline material I split pieces from an old viola soundboard.

I carefully apply paste wax with a cotton swab up the the edges of the crack and then tape it off using low-tack painting tape. Hide glue is worked in and the spline is quickly inserted. I use the back of my carving knife to press it firmly in place.  Here, I'm just beginning to pare away the excess. When I near the surface of the guitar I switch to a razor blade used as a scraper.

A little bit of touch-up work is necessary on the surface where one's arm contacts the face. The owner wishes to seal off this area to prevent sweat infiltration. I'll use a tiny paintbrush and some shellac tinted with alcohol-soluble dye. It took a few tries to come up with the right density of color.

Going...going...

That's better than it was.
To reglue the loose section of pick guard I decided to use inexpensive white glue.  Usually maligned in the luthiery community because of it's propensity to "creep" under load, that property seemed advantageous in this instance.

Here's the setup for gluing on the bridge-patch overlay.  A piece of hard maple is cut and planed to about 2mm thick. I don't want to make it any larger than it needs to be. You can see in the photo that the grain runs out at an angle and I feel this is important.  Recall the torn fibers from the photo in the last blog entry?  At first glance it looked as though the patch had split clean through in line with the grain. As it turns out, the blowout from the exiting drill bit tore those fibers at the time the pin holes were drilled!  Using a patch with the grain at an angle can prevent that to some extent, as will using a block to back up the drilling. 

The patch will be kept in position using two #10-32 machine screws which go through the sacrificial block and patch, both pre-bored to the correct placement of the outermost pin holes. That block is heavily waxed, as are the screws. The screws aren't long enough to interfere with a clamping caul placed on the top surface of the bridge.

All clamped. Normally I would remove the saddle but there was enough bearing surface. The saddle may have been glued in place. We'll have to see what happens during set-up. Luckily there is plenty of exposed bone.  Pro-tip : snip a length of surgical tubing down one side and the soundhole periphery will remain free from clamp damage!

Incognito! A 1936 Carson J. Robison

Here's an interesting guitar ready for some care and attention.  The headstock bears the name of Carson J. Robison, a cowboy crooner who got his start working as a whistler on WDAF in Kansas City, in the mid-1920's. That's right. The man was a professional whistler...

He later appeared on The Grand Ol' Opry and penned the lyrics to Barnacle Bill the Sailor and was inducted into the Nashville Songwriter's Hall of Fame.  In the 30's he also gave his endorsement to a line of guitars sold through the Montgomery Ward catalog.  As it happens, they were produced by the Gibson guitar company. Gibson made a number of low[-cost models during the depression, most prominently under the Kalamazoo badge.  This instrument is essentially a budget L-00, being 14-5/8"  across the lower bout. 

Gibson dispensed with the expensive and time-consuming truss rod.  The neck is a pleasing hard-V shape and it's in good shape. The head shape and markings tell us this instrument is from 1936.

Some odd chipping has occurred at the end of the fretboard adjacent to the nut. Nut width is 1-3/4" (44mm). The scale length is 24-3/4" and it joins the body at the 14th fret.

The bridge is quite delicate, being only 15/16" (23.5mm) wide and 5-7/8" long. It's only 1/4"(6mm) tall. The string spacing at the saddle is a robust 2-3/8" (59mm).

Here's the issue.  The pickguard has shrunk a little, being cellulose. It's pulled a crack into the top between soundhole and bridge. The owner and I discussed removing the pickguard and regluing it. In the end I deemed it unnecessary. This guard is very thin, and it hasn't created a serious deformation in the top surface. By luck a portion came unstuck on the side opposite the crack, thereby relieving much of the stress. This guard was adhered to the bare wood prior to finishing, and that gorgeous sunburst was sprayed right over it. We can re-adhere the loose portion and maintain the originality.

So, where did Gibson skimp?  They saved 25 cents on the truss rod, and another nickel on the back binding. The bracing is stout and simple, transverse bars above and below the sound hole, and two bars that run fore and aft of the bridge. Decent mahogany was used throughout. The application of glue on the interior was not particularly fastidious. The side depth is quite generous, tapering from 3-9/16" at the heel to about 4-7/16" at the tail.  I can't wait to hear how this thing sounds.

The other piece of structural work to be undertaken lies inside. The ball-ends of the strings have eaten through a portion of the bridge patch and I'll make a small overlay. Isn't it amazing that after 70-odd years the fuzzies from drilling for the pin holes still remain?

1926 Gibson L-3 Part 3

The card in my little point-and-shoot camera gave up on me this week, taking with it several process shots.  Suffice it to say, -I added some binding around half the back, scraped it to size using single-edge razor blades, and tinted it with orange shellac to approximate the color of the existing binding. I put a little on the bare spots on the sides where the finish had flaked off too, but I didn't try to get into exhaustive lacquer repair. This guitar is almost 90 years old and it looks it.

The Stew-Mac tuners went right in the old bushings with no fuss. They seem to be made to much closer tolerances than the old ones. I introduced a beefy set of .013 -.058" medium strings, as I imagine this thing spent most of the dustbowl years strung with Black Diamond baling wire.

Here's a video of me fumbling through some period-appropriate tunes. I apologize for the sound quality. If I do this again I'll get an external microphone.

Gibson Archtop Part 2

There are some places where the kerfed lining is missing.  These are the greatest little clamps. I found them one day at the dollar store, six in a package. I used to use clothespins wrapped in rubber bands, but on triangular binding like this if one doesn't get the placement just right they tend to pull the lining strip up. These things have swiveling pads. Rotate the inner pad out of the way and there's a little notch that keeps everything exactly in position.

Here's a little opening where the top is lifting. I used a palette knife to get the hide glue in there and clamped it in place with spool clamps.

The back was installed in the same manner. I know I'm going to put a coat of spirit varnish over the sides, otherwise I'd be more careful and  use short lengths of drinking straw over the threaded rod to be certain it doesn't scratch up the surface.  The back went on pretty well. There's one area in the upper bout that must have shrunk some across its width, or the sides have sprung a little. It's just shy of a perfect fit.

The binding is quite narrow. I used my veneer scraping tool to shave a little off the height to keep it from tipping inwards during installation.

This is ABS plastic. (The original is celluloid). I picked up on a trick from John Calkin and the crew at Huss and Dalton who use Tightbond glue to secure plastic bindings. Roughing up the inner surface with 80x sandpaper provides enough tooth for good mechanical adhesion. (Better than you'd imagine). It cleans up much more easily than the solvent based plastic glues - they have a tendency to liquify the surrounding finish. This old lacquer is crazed and chippy. Low-tack tape is a must!

The missing tailpiece string retainer had me scratching my head. I found some photos of various original designs. Perhaps the original was made of nickle-plated brass. In the end I decided to fabricate it from aluminum bar stock.  My first attempts with a 1/16" drill ended in failure. Too much heat and friction and the bits kept breaking off in the aluminum.  I beefed up the hole diameter and used a countersink on each side to provide a soft transition for the string.

Smooth radius to prevent string breakage and a place for the ball-end of the strings to sit.

I resisted the urge to buff it up to a mirror shine. It'll do the job and it doesn't call attention to itself.