1975 Guild F-212 Re-build

1975 Guild F-212 on the bench

Introduction

One of my 1975 Guild F-212 12 strings needed a neck reset. Over the years, I had attempted to counter the ever-raising string height by lowering the saddle. I had sanded it so low it was practically buried in the slot. I had long since passed the point where I might have planed the bridge down, in some effort to maintain any semblance of break angle on the strings. Not doing so, and continuing to lower the saddle (to chase the raising action and try to keep the guitar playable), resulted in a very quiet 12 string. And the action continued to grow higher. And it went into a case and I didn't play it for ages.

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Assessment

Years passed, and one fateful day I pulled it out of its case and set on the work bench. To the casual observer, this Guild would look to be in remarkably good shape for a nearly-50-year-old guitar. Further inspection, however, would reveal issues that could not be ignored.

Cracks in lacquer finishes often are the result of the sudden exposure of a warm guitar to very cold temperatures. It is not common to find a 40 to 50 year old guitar without any. This was one of those more rare guitars that not only had very few finish cracks (it had one itty, bitty crack), but also lack the dings and dents and scratches I have all over my other F-212 from the same year.

Actual cracks and splits in the wood are either the result of impact damage (accidental or otherwise) or that potentially destructive combination of humidity and/or temperature conditions along with all that string tension that is being constantly applied to a wooden instrument. The dreaded neck block shift / soundboard split had occurred at some point in the guitar's recent history, shearing the soundboard along the bass edge of the fingerboard extension, from the neck heel and into the soundhole. Admittedly, I can't tell you when that happened. I suspect it was decades ago, and i simply didn't notice. It wasn't grotesque, but it visible. Regardless of how it looked, I believe it was largely responsible for the high action.

A neck block should never shift, and a soundboard should never shear. If either occurs, it is evidence of glue failure and/or insufficient structural reinforcement. Under string tension, both glue failure and insufficient structural reinforcement will contribute to unfavorable results.

Soundboard shear along the fingerboard extension
Soundboard shear along the fingerboard extension

Glue failure can occur for a number of reasons, perhaps the most common being a combination of temperature issues and string tension, such as when a guitar is left in a hot car. Glue softens and parts slip and slide and shift. Adjoining pieces of wood may continue to be perfectly glued together and yet they have shifted away from their original position(s). Under certain conditions, where an insufficient amount of glue was applied, parts may rest against one another but no longer be bonded. Brace failure is a common example of this, where the soundboard appears to be securely attached to the X-Brace beneath it, but it is merely resting on the brace, and you can slide a thin feeler gauge between brace and board.

The other factor that can be responsible for a soundboard split is the shifting of the entire upper bout, where the upper bout above the soundhole rotates or tilts forward or to one side. Such a shift can certainly occur as the result of glue failure, but a sudden jolt applied to an instrument having insufficient structural support will allow for just enough movement to do the same damage.

General splits and cracks in woods (and finishes) can and will occur under humidity extremes, especially where pieces of wood are restricted in their ability to swell and/or contract, having been glued in place.

These Guild guitars were constructed without using a fingerboard patch (or "popsicle" brace), a thin horizontal strip applied to the backside of the soundboard just behind the transverse brace and extending across the width of the upper bout. This extra strip of wood is found on 12-fret Martins dating back to the 1850s, and was added to 14-fret Martins around 1939. The idea behind the thin brace was to mitigate the soundboard shear, though shearing still occurs, especially under extreme conditions.

Fingerboard Patch / Popsicle Brace
Fingerboard Patch / Popsicle Brace

A superior design is available in the trapezoidal brace, where two sticks are glued to the soundboard running between the transverse brace and the neck block. They splay out and across the parallel grain of the soundboard, crossing the point where the fingerboard extension lays (on the other side of the soundboard).

Trapezoidal Brace
Trapezoidal Brace

A small block of wood was added to the top front of the neck block, forming a ledge or shelf. Why? In theory, this would add more real estate to glue the soundboard to, well above and beyond what you would expect to find in the traditional 6 string guitar neck block. The extra buttressing would potentially aid in resisting the pull of the strings on the headstock and the resultant tendency of the fingerboard extension to want to depress the soundboard, pushing it in toward the back of the guitar, as the cantilever of the neck tries to pivot at the body joint, essentially folding the body in half. This is also the theory behind the use of the "transverse" brace that runs side-to-side, just above the soundhole. The idea is that the fingerboard extension (and the soundboard beneath it) won't plough downward under string tension. This "collapsing" of the soundboard into the soundhole at the upper bout is not a pretty sight. At the very least, it demonstrates the failure of the components, if not the actual design, itself. I do not subscribe to the transverse brace design, preferring to reinforce the upper bout differently.

Fretboard Extension Collapse
Fretboard Extension Collapse

On this particular 12 string, such dramatic collapsing is not the problem. In fact, there is no evidence of any such collapse. At whatever point this neck block shifted and/or tilted forward, it simply took the section of the soundboard that was glued to it along for the ride, shearing away from the adjacent wood of the soundboard. This occurred in spite of all that extra protection of the additional ledge added to the neck block, or the presence of the transverse brace. Whether or not a fingerboard patch would have prevented it is unknown.

Neck block (as viewed from inside)
Neck block (viewed from inside)

Thin, flat braces were glued to the underside of the soundboard, running diagonally from the transverse brace near the neck block out toward the centers of the shoulders of the upper bout. It is interesting to note that when a soundboard split along the fingerboard extension occurs in one of these guitars, it always happens along the edges of the fingerboard between the fingerboard and these diagonal brace(s). Hmm...

Sufficient force and/or inertia applied to the neck block/upper bout area would telegraph and be concentrated at the soundhole, resulting in a shearing of the soundboard along on or both sides of the fingerboard.

Diagonal bracing (as viewed from inside)
Diagonal bracing (viewed from inside)

The fingerboard is made from a very dense hardwood (Brazilian Rosewood, in this case). The grain direction of the fingerboard runs lengthwise from the headstock, down the neck and out onto the soundboard. It will expand and contract from side-to-side when exposed to moisture variations. The fingerboard extension is glued down to the soft Spruce soundboard beneath it. The grain direction of the soundboard also runs lengthwise, and it will also expand and contract from side-to-side when exposed to moisture variations. The soundboard is glued down to the neck block.

The neck block's grain direction is perpendicular (rotated 90°) to the soundboard and fingerboard. Traditionally, the thinking behind this has been to position the neck block in such a way as to expand and contract in the same direction of the sides, up and down. Of course, wood moves in more than just one direction. In this photo I have drawn a double-headed arrow indicating the direction the neck block will expand and contract due to moisture variations. Let your imagination be your guide, and consider what may occur should the neck block ever swell!

Neck Block Grain Direction
Neck Block Grain Direction

The primary culprit in our neck block/soundboard shift is related to the soundhole itself. When tightened, the strings are quite capable of ripping the bridge off the face of the guitar. A 4 inch diameter hole has been cut into a thin wooden plate in front of that bridge, in a location that is supporting well more than 200+ lbs of pressure/tension.

The neck is a cantilever. It is affixed to the body at the upper bout. On many (most?) acoustic guitars the neck joint can act as something of a hinge, allowing the neck/neck block (as a unit) to tilt or pivot forward. This action will result in the concentration of force onto the precise location of the soundboard where 12-1/2 square inches of very needful support material is now non-existent. What could possibly go wrong? The fact that soundboards having no soundholes (or significantly offset soundholes) do *not* experience shearing along the fingerboard extension is clear evidence of the actual problem.

To better support a center soundhole design, especially on a 12 string, it is necessary to reinforce the entire upper bout. My approach focuses on unifying the soundboard above the waist, the back, the neck block, and the sides into one immovable (or nearly immovable) mass. No more neck block shifts. No more soundboard shears/splits along the fingerboard extension. No more neck resets as a result of either of the two aforementioned issues.

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Disassembly

If I was simply intending to reset the neck, I would remove the neck as a unit, make the necessary corrections, and re-attach it. If I was simply intending to address the aesthetic issue of the neck block shift/soundboard shear, I might add a patch to the underside of the soundboard. Some refer to this effort as "stabilizing" a crack though, once you understand what has gone wrong and caused the shearing it seems a bit silly to think a small patch has stabilized anything.

I am going to first take this guitar apart and then decide how I want to rebuild it.

The bridge will most likely need to be completely replaced, as it is relatively thin. But, we'll see. At this point I know I am going to replace the soundboard, so I could just leave the bridge on and cut the soundboard off. But, whether I re-use the bridge or not, it should lift off easily with a little heat.

Removing the bridge
Removing the bridge

The Brazilian Rosewood fingerboard was also really thin, well worn, and had a lot of divots in it. These shallow gouges are typically a result of some combination of repeated fingernail and/or string contact, and/or a softer fingerboard material. They don't technically impede playability as much as they are unsightly. They can be filled (under certain conditions) or the board can be leveled by planing or sanding. Over time, if enough material gets removed, eventually the whole thing will need replacing.

The old fingerboard
The old fingerboard

It was time to take off the neck. I removed the appropriate fret and drilled an angled hole through the fret slot, hoping to emerge in the recess between the dovetail of the neck and the mortise of the neck block. I missed the cavity, burying the drill in solid wood. I tried it again on the opposite side of the fingerboard, adjusting the angle slightly. I missed, again! See why neck resets are so much fun?

Drilling into the neck block
Drilling into the neck block - missed it by *that* much

Refusing to be beaten, I moved back to the original side, starting the angled hole closer to the center of the fingerboard, and SUCCESS! I repeated a second successful hole on the opposite side.

4 holes in fingerboard
4 holes in fingerboard (the 2 inside holes were successful)
Guild Dovetail Measurements

If I am steaming off a neck (as opposed to using a heat rod), I like to apply a small amount of steam to both sides of the dovetail, instead of concentrating all the heat and moisture on one side. The second hole into the joint provides for an egress for water, an inevitability as the steam cools and condenses once inside the guitar. If you can hold the instrument fretboard-side down while applying steam, you can prevent the pouring of water into the body - a definite no-no in my book. If you have one of those guitars with visible white rivulets of powdered residue running down the inside of the back and/or sides, you know what I am referring to.

Using a jig that presses against the top rim of the body while simultaneously pressing against the heel cap (I think of it as my reverse steering wheel puller), I pushed the neck up and out of the socket it was glued into. And I experienced another misstep. Note that as substantial as the necks on these Guilds are, the neck heels can be surprisingly thin at the heel cap, not leaving much to push against.

Thin neck heel
Thin neck heel

In the days before CNC, guitar necks were made utilizing some combination of sawing, carving, sanding or routing. Fitting a neck having a heel to a body typically requires removing some of the heel material in order to arrive at the correct geometry. I have reset many a Guild guitar neck, and some necks have thicker heels than others. That may be due to deliberate design, or the neck was hand-made, and/or a batch of generally sized necks were fitted to a variety of less-than-consistently-glued-up bodies. This particular neck heel was very thin. Upon adding serious heat in the form of steam, and applying sufficient pressure to the end of the heel, guess what happened? The wood of the neck heel, right at the heel cap, compressed and curled, actually de-laminating slightly.

Neck heel wood has curled
Neck heel wood has curled

Now that it had curled, I had to make a decision. I could re-cut the heel and thin it even more. I could attempt to re-shape the heel, reversing the steam process, and risk greater damage to the neck. Or I could overreact entirely and re-make the neck. I opted to take the easy way out and re-make the neck! To be fair, I had thought about doing this for several years in order to significantly lighten the neck. As you may be aware, Guild 12 string necks of this era were constructed using twin steel compression rods. Apart from the discussion of the pros and cons of one-way adjustability, the steel makes for very heavy necks. This would also give me a chance to document the dissection of one of these necks, something I realized I had never done.

As the fingerboard extension lifted off the top it took a chunk of the top with it. This can happen if I am being overly aggressive in trying to pry off the neck and have sufficiently released the fingerboard extension from the soundboard, first. But that was not the case, here. The shearing off of this piece of wood revealed severe grain runout in the soundboard (little or no runout would have prevented such shearing). If I was on the fence before regarding replacing this soundboard, the degree of grain run-out I encountered is more than enough to confirm the need.

Tearout
Tearout

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Finish Removal

The old bridge along with the old fingerboard are simply too thin to be re-used and will be replaced. I will completely replace the soundboard, thanks largely to the split caused by the neck block shift, along with the amount of grain runout I found. I have decided I will also replace the neck entirely. I definitely want to refinish it, too. There is a tinted lacquer finish on the neck and back and sides, hiding the underlying wood. What were they hiding? Even if the wood beneath the tinting is not perfect in appearance, I prefer to see the wood grain. I grab my scraper and start to work...(it's not like I haven't done this a hundred times, before).

Scraping off the old finish
Scraping off the old finish

There is often a surprise waiting beneath these dark tinted lacquer finishes; either a painful surprise as I discover exactly why someone chose to paint the guitar, or a pleasant surprise as I uncover lovely blemish-free wood. This guitar did not disappoint. Lo and behold, the underlying Mahogany is quite lovely. I can already envision a new finish on this guitar that showcases that Mahogany.

Mahogany Back and Sides
Mahogany Back and Sides

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The Body

Perhaps the most well-known of the Guild 12 string guitars happen to be jumbo body styles from the 1960s and 70s, though Guild has offered 12 strings using their dreadnought body shape, as well. The largest of the Guild 12 strings, no longer offered, was the F-612. With an 18" lower bout, this beast could be referred to as a "super-jumbo." The more ubiquitous 17" jumbo bodies were featured in models such as the F-212XL, F-412 and F-512. A slightly smaller body, with a lower bout between 15 and 16 inches, was reserved for the F-112, F-212, and F-312.

The body of the F-212 I am rebuilding, which I will refer to as a "mini jumbo," is still quite heavy. Weighing more than 3.1 lbs, it is a testament to the Guild legacy of this era of being built using more wood than is technically needed to structurally support the guitar. The extra wood actually contributes to the unique sound of the Guilds of this era. By way of comparison, my own jumbo guitar bodies, wider, deeper, and longer than this Guild, weigh a mere 35 oz, nearly 1 pound less than the Guild.

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The Soundboard

I carefully removed the old soundboard, intending to preserve it, as it makes for a good reference top. There is very little difference between the soundboards of the mini jumbos and the jumbo 12 strings.

Old Soundboard
Old Soundboard

An "a-Ha!" moment has occurred. As I took off the soundboard, I noticed a tremendous amount of tension in the body. As I was completing the cut to remove the soundboard, the body of the guitar actually "sprang" open (as opposed to simply staying put, in a rigid position). This amount of movement is evidence of the tension the soundboard was under whenever whatever force(s) caused the neck block shift and resultant soundboard shear along the fingerboard extension.

I selected a set of wood from a group of really stiff Bearclaw Sitka tops I picked up ages ago. I glued the two plates together and, when dried, gave it a tap. As I had hoped, this wood rings like a bell.

Bearclaw Sitka
Bearclaw Sitka

I have some lovely, old Sitka brace wood that I will use. The X-brace will be narrow and tall. I cut several pieces to size and shape them to follow the radius of the top using a router, a flush trim bit, and a template.

Brace Radiusing Jig
Brace Radiusing Jig

Having repaired, rebuilt, and re-engineered several of these Guild 12 string guitars over many years, I have developed my own bias, my own preferences for the bracing layout. This guitar will be no different, and I will follow the format I have proven to work, and work well.

I will apply carbon fiber tow beneath and atop the X-Brace. This effort significantly (as in, measurably) stiffens the bracing. Too stiff a brace will kill the sound. Too supple a brace will kill the soundboard. I achieve the proper stiffness through an iterative process that includes measuring the deflection of the soundboard under a particular load, removing brace material, and re-measuring. Over the years, I have arrived at optimal target numbers for that deflection depending upon the desired performance of the soundboard.

I tape off the soundboard to help position the X-Brace and to assist with cleanup of the glue. The braces along with the upper bout reinforcement are all bonded to the soundboard using Superbond epoxy. In addition to adding stiffness, this epoxy eliminates glue failure issues, such as creeping or popped braces. These soundboards produce a bright and crisp response, and I can be confident of their performance over time.

Tape for positioning the X-Brace
Tape for positioning the X-Brace

First I lay the tow in a bed of epoxy...

Carbon Fiber Tow
Carbon Fiber Tow

...then I rest the X-Brace on top of the tow, secure the braces, and wait for the glue to dry.

X-Brace Glue-Up
X-Brace Glue-Up

It is now time to add the bridgeplate, butting it up against the lower legs of the X-Brace. I have had such success with my laminated Rosewood/Maple bridgeplates on these guitars that I see no need to alter my technique. I get both the bright response of a Maple bridgeplate and the more gnarly, hard-to-tear-up bridge pin holes of a Rosewood bridgeplate.

The so-called "Tone Bars" extend across the lower bout, touching the lower leg of the X-Brace on the "treble" side and terminating just short of the kerfing on the "bass" side. The "Finger Braces" extend from both lower legs of the X-Brace up toward the waist. The original soundboard tied these small braces into the sides. I have discovered better performance by terminating them short of the sides This leaves only the four (4) ends of the X-Brace to rest upon the rims of the sides.

Additional Braces
Additional Braces

You may have noticed that, up to this point, there is no soundhole. Traditionally, the hole is cut in the soundboard prior to adding any bracing. Because I add reinforcement to the upper bout in the form of two (2) layers of Mahogany, careful to achieve three (3) separate grain directions, I "can" cut the hole first, laminate the veneers, then re-cut the hole through the veneers. But I have found it preferable to first add the X-Brace, then add the veneers, then add the additional braces, then flip the soundboard over and address the soundhole.

I have decided to appoint this F-212 with Walnut binding instead of plastic, and that includes the soundhole. Using Paua shell and wood purfling I approximate the look of the plastic rings used on the original soundboard. Personally, I prefer my version.

Soundhole
Soundhole

Before I can add the tow to the top of the X-Brace, I need to carve the brace(s), reducing unnecessary material. To determine how much material to remove I suspend the soundboard on the four ends of the X-Brace and, using a weight and a dial indicator, I am able to measure and target the deflection I am looking for. Once the braces are carved, I add the tow to the top surface of the X-Brace.

X-Brace Tow
X-Brace Tow

Once the glue is dry on top of the X-Brace, the soundboard has stiffened up again (significantly). I continue the iterative deflection test process and remove the rest of the material from the Tone Bars and Finger Braces until I am satisfied.

Carved Tone Bars
Carved Tone Bars

The soundboard is now complete.

Soundboard Complete
Soundboard Complete
Soundboard Complete
Soundboard Complete

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The Arm Bevel (Interior)

I will be adding an arm bevel to this 12 string. This feature makes for a more comfortable player experience, especially on wider, deeper-bodied instruments. I have no knowledge of this ever being done on a Guild. Perhaps this is a "first?"

Once the soundboard is removed, I need to cut the curve into the side of the body to accommodate the arm bevel. I rough out the curve with a saw, then use a template to guide a router bit, resulting in a very accurate and smooth line.

I cut a Basswood block to fit the contour of the body and glue it into place inside the body. This block has a dual purpose: it forms a lightweight ledge that will support the soundboard and it provides a base material that I can shape into a bevel.

I add wooden braces to the sides in four (4) specific locations. I also bevel the tail block, removing unnecessary material where the soundboard will rest. Short of replacing the tail block entirely with a laminated equivalent, this step is the next best thing to eliminating that unsightly telegraphing of the rectangular outline of the block, visible in so many soundboards over time.

(If you were wondering about that "notch" in the arm bevel block, I have removed material to receive the lower leg of the X-Brace, as it will no longer extend out onto the rim of the lower bout, but will rest on a shelf.)

Arm Bevel Block
Arm Bevel Block

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The Upper Bout Interlock

The purpose of adding lamination to the upper bout is primarily to strengthen that critical section of the soundboard that we intend to remove 12-1/2 square inches from by cutting a large hole clean through it. To fulfill my goal of unifying the neck, neck joint, and neck block with the soundboard, forming an immovable unit, I "notch" the upper bout to receive the thicker upper bout section of the soundboard, locking it into place. This notch begins at the point where the upper arms of the X-Brace rest, and extends up and across the neck block, lessening the height of the sides by the depth of the lamination I have added to the soundboard. Once glued in place, this interlocked unit of neck block, back, sides and soundboard eliminates any possibility of neck block shift and/or soundboard shear.

Upper Bout Interlock
Upper Bout Interlock

Gluing the soundboard to the body is a matter of fitting two puzzle pieces together. It should not involve wrestling parts into place that must then be clamped in order to avoid unsightly gaps. So doing will introduce unwanted tension into the guitar. Instead, an iterative process of fitting, trimming, and fitting again is necessary until the soundboard and body mate perfectly.

Soundboard Attached
Soundboard Attached

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The Side Port

After the soundboard was attached and trimmed, I decided to add a simple Side Port. These ports demonstrably improve the player experience, and have no deleterious effect on the audience experience. Frankly, I think they should be added to all acoustic guitars. Once again, I am unaware of this feature ever being added to a Guild, so this may be another "first."

Rather than just cut a hole in the side in the upper bout area, I prefer to add a reinforcing block of wood to the side. It would have been ideal to have added the reinforcing block PRIOR to attaching the soundboard, as access to the inside of the guitar is easier. But this is the same process I use when retrofitting/incorporating a Side Port into a completed guitar, so it is not a big issue. In addition to strengthening/supporting the thin side in the area around the hole (which a piece of veneer laminated to the side would also achieve), I believe a wooden block can improve the visual interest/aesthetics.

After determining where my Side Port will be positioned, I fashion the wooden reinforcing block and carefully glue it into place. Once the glue is dry, I drill a hole through the side and block, removing the majority of waste material. I mount a jig to the upper bout and, using a router fitted with a template guide and downcut bit, I trace around the Acrylic pattern mounted to the jig to complete my Side Port.

Side Port
Side Port

The body is ready for the binding channels to be cut at this point.

Side Port
Body with Soundboard

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The Binding

When I bound the soundhole I committed to the decision to use Walnut for the binding. Yes, white plastic binding is traditional and yes, plastic is easier to apply and yes, plastic is even more forgiving should you happen to bump an edge against a hard surface. But I prefer to look at wood binding. And, while it is perfectly acceptable to simply wrap a piece of wood around the rims of the instrument and be done with it, if I take the time to laminate one or more veneers to my binding wood of choice first, prior to ripping off strips of binding, I am able to apply a more embellished binding/purfling combination to the sides, making for a dressier look.

Making Binding
Making Binding

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The Arm Bevel (Exterior)

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The Neck

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The Headstock

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The Finish

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The Fretboard

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The Bridge

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The New Guild F-212

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