Froggy Bottom Methodology:
How a Froggy Comes to Life
In 2008 we decided to create a new model and offer the prototype guitar to L.A.C.E. in Barre, VT for a raffle. We documented the building of the guitar in a blog for the website. Now in start-to-finish order, this remains a valuable resource, documenting our methodology from start to finish.
January 25 – Day 1
Off camera, we’ve selected the wood for the guitar, highly figured Brazilian rosewood for the back and sides and Adirondack spruce for the top. The bookmatched halves of the top and back have been rough sanded and joined together. Channels for the back seam inlay and the rosette, as well as the soundhole in the top have been cut. A neck blank has been laid up, gluing heel block and headstock to the running stock of the neck. The tenon which will join the neck to the body has been cut on the table saw. A channel for the truss rod has been routed, and the truss rod installed, and a highly figured rosewood peghead overlay has been glued to the face of the headstock.This
A ‘set’ of wood: the top, back and sides for the ‘LACE’ SJ; Adirondack spruce for the top and Brazilian rosewood for the back and sides.
Michael cutting the SJ mold. This will be used to bend the sides of the guitar.
Andy has taken the side out of the hot water ‘bending tank’ and placed the side onto the bending form or mold. An electrically heated element is used to cook the side for 12-15 minutes; the side will remain on the form overnight until it is completely dry.
Eric has routed the channel for the inlay on the seam of the Brazilian rosewood back, and is inlaying strips of Paua abalone bordered by black and white lines.
Detail of the center seam inlay on the back. After the glue is dried thoroughly the back will be sanded to an exact final thickness and be ready for bracing.
The bent sides ready for kerfed linings.
Kerfed mahogany linings are glued to the sides. These will increase the gluing surface area for attachment to the top.
The various top braces are glued to the top and carved in five stages. This photo shows the second of those five steps, in which the upper and lower face braces are being attached. When the clamps are removed, these braces will be carved and the next group of braces will be placed, glued, and carved.
The final carving of the braces, often referred to as ‘voicing the top’. The builder must be able to hear the subtle change in tap tone resulting from carving.
Michael has suspended the top on his finger so as not to restrict vibration. A sharp tap with a fingertip from his right hand will tell him if the top is done. If the response is not clearly as intended further carving is required.
The braced top is attached face down to a building stand. Neck and tail blocks are precisely placed and glued to the top. Unlike most steel string guitars, these instruments are built without an exterior mold and face down in the tradition of classical guitar construction. This methodology allows unparalleled flexibility but also requires a high degree of skill and attention to the process.
Glue has been applied to the lined edge of the side and to the neck and tail blocks. The side has been positioned and is held in place by wooden cam clamps. The builder must move rapidly and decisively; the entire process of attaching sides to top and blocks takes about five minutes.
The first clamp on each side is located at the waist; the second next to neck block. This step is repeated on the second side.
Once the sides are properly positioned on the upper bout, wooden cawls which span the body are inserted beneath opposing pairs of clamps. These are much more stable than free standing clamps. A metal C-clamp (visible behind Michael’s left hand) clamps the sides to the neck block. Additional wooden cam clamps are then used to position and secure the sides progressing from the waist down the lower bout.
When four sets of clamps with cawls have been placed across the body, two more cam clamps position the sides adjacent to the tail block.
Four C-clamps are used to fasten sides to the tail block. At this point all eight cam clamps on cawls are released and re-tightened in order to release any undesired stress or tension in the sides.
Tomorrow morning the clamps will all be removed and we will be ready to secure ends of all top braces with kerfing chips and prepare the rim of the guitar for the fitting and installation of the back.
A thin graft of cross-grain spruce has been glued to the back, supporting the back seam. Here Andy is shown removing chips of spruce where the braces will be installed.
The back braces, curved, but still rectangular in cross-section, are glued on using wooden cam clamps. The brace with the tightest radius is done first and the one with the greatest radius is done last.
Another view of the clamping of braces as the process proceeds. Notice the work board beneath this assembly which allows the work to be moved after all clamps are in place and also maintains continuity of curvature among the four back braces.
Andy is using a small block plane to carve back braces to an appropriate cross section for this particular guitar. This is varied with each instrument depending upon how lively we wish the back plate to be.
A paring chisel is being used to feather the brace ends where they will be notched into the kerfed body lining. If too much is removed here the back becomes vulnerable to pressure or impact; too little and the back is too stiff, reducing the overall liveliness of the instrument.
Braces have been carved and sanded. The back is now ready to be fitted to the body.
The arch on the back of our guitars is critical to the instrument’s ability to project sound well. Off camera, the rim of the back has been carefully arched using a paring chisel and a very sharp, low-angle block plane. Kerfed mahogany linings are then glued to the edge of the rim, as shown here. Once the clamps are removed, the back of the rim is carefully sanded with a large, perfectly flat, plywood sanding board, faced with 60 grit sandpaper.
The kerf-lined crown of both upper and lower bouts is being feathered with the block plane matching perfectly the surfaces of the back and the rim for gluing them together.
The back has been carefully positioned, orienting it to the body according to the center seam and longitudinally. Each brace end is precisely scribed to indicate its proper trimmed length and its location is also scribed on the rim of the guitar.
Andy is shown notching the pocket in which the brace end will fit snugly. Notice that the end of the brace which he is fitting sits very close to the pocket for accurate reference and a perfect fit.
When all of the brace ends are properly fitted, the back is positioned on the rim and is scribed on it’s underside, around the perimeter of the guitar. The excess on the back is cut off on the bandsaw and the ends of the back support graft are trimmed to length.
When everything has been checked, double-checked, and the back is ready to go on, each of us signs the guitar.
The back is glued to the rim, clamped with cam clamps and wooden cawls and then strapped around the perimeter with a long rubber band fashioned from an inner tube of a truck tire.
The back completely clamped in place will dry for several hours before removal of the clamps.
This method of face-down construction has evolved from classical guitar construction and is extremely important to the sound of a Froggy Bottom guitar. This free-standing assembly system also allows enormous flexibility in the design and construction of our instruments.
Our jig for routing the end graft inlay channel. After routing, a wedge of wood and the adjacent purfling lines are glued into the channel with epoxy.
This is the same process at the other end of the guitar body: the ‘heel grafts’ inlaid on the shoulder of the upper bout adjacent to the neck heel.
The completed end graft.
The completed heel grafts
Our wall-mounted laminate trimmer, used to route the various channels for the binding and purfling on guitar bodies.
All the routing is done; now comes the handwork. There are a dozen mitered purfling joints on a Standard or DeLuxe grade Froggy, sometimes more. Take a look at them the next time you pick up one of our guitars and compare these details to what you see on most guitars. Details, details…….
Mitering these purfling joints takes time, patience, and a great deal of skill. There are no shortcuts; no fancy jigs or tools. Here Eric is shown cutting the miters at the heel grafts.
Mitering the purfling lines on the back center seam inlay.
Once the purfling has been cut to the perfect angle and the curly maple binding butt joint has been cut and fitted, all six pieces (four purfling strips and two pieces of binding) are ready to glue in. This begins at the lower bout of the body and proceeds up to the top of the upper bout.
The full weight of Eric’s body presses on his thumb to seat the binding & purfling while his other hand applies heavy masking tape to hold the pieces in place while the glue dries.
The fit of all pieces must be perfect before gluing, otherwise it must be routed off and the entire process repeated.
Too much of this can lead to a severe case of ‘purfler’s thumb’. Ouch!!!
After sitting overnight, the tape will be removed and we’ll see how she looks!
Today we pick up our SJ neck, already in progress. Our first photo shows the ‘rough’ neck, with the classical style three-piece layup of the heel block, the running stock, and the peghead clearly visible. We use this traditional method for its superior strength and stability. After the neck pieces are glued together as shown, the tenon for attaching the neck to the body is cut; the tenon sides then get a thin cross-grain mahogany lamination on each side, once again for superior strength and structural integrity.
A channel for the truss rod is then routed into the running stock. The two-piece over/under rod of 3/16 inch steel is set into the channel; a 1/16 inch mahogany cap is glued on top of the rod, so that it is completely embedded into the neck. The rectangular rod has greater bearing surface than a round section device. Notice that the rod works independently of all other parts, and that it is designed to oppose perfectly the tension of the strings. (Truss rods are designed to ‘true’ a guitar’s neck, NOT to adjust the action.)
After being certain that the neck blank is perfectly flat, the fretboard is positioned, located with two small wooden dowels, and glued in place.
The peghead overlay, in this case of Gaboon ebony, is then glued to the peghead face. Spanning the running stock of the neck and the peghead as it does, this creates a headstock of greater strength than a one-piece neck.
The truss rod is the tightened slightly, back-bowing the neck a bit. The fret board is then planed perfectly flat and the appropriate radius on our CNC router.
The small bandsaw is used to trim the excess stock from all areas of the neck in preparation for rough carving on the CNC router. We only use the CNC to do rough stock removal on our necks, preferring to do the finish carving by hand. This allows a much wider range of neck shapes in response to the widely varied and highly specific needs of our customers.
She’s starting to show her personality now! After a thorough scraping to remove rough scratches and level all surfaces, the body has been sanded down to 320 grit sandpaper. Sealer has been applied in preparation for grain filler which, after scuffing with fine sandpaper, will make the wood surfaces smooth enough for lacquer.
Another view at the same stage, showing the sides. Please note the difference in color of this and the previous picture. Color presentation on different computer monitors can vary greatly! On our Mac, the previous picture (of the back) is much closer to the actual color of the rosewood.
Imagine coating your guitars’ rosewood back and sides with almost black mud! That’s what allows your instrument that glass-like lacquer finish, giving the grain such three-dimensional depth. The paste filler is painted on with a brush; after drying for about an hour the filler is wiped off with burlap cloth, leaving little residue except what fills the pores of the wood grain. Any smudges, etc. are wiped off with cheesecloth.
Off camera, Andy has been in the spray booth. After masking all surfaces except the top, a tinted base coat has been sprayed on the top in preparation for the actual sunburst. After the sunburst pattern itself has been sprayed it is allowed to set up only partially. Then the dark lacquer is removed from the body edges and the rosette rings. In this photo, if you look carefully you can see that the inner ring of lines and abalone shell still has some dark lacquer on it.
Andy smiling at the fret press, installing the frets in the fingerboard. The fret ends will be trimmed and beveled, but not given their final dressing until the last stages of set-up.
All necks are rough carved on the CNC router. Final carving and shaping is done by Michael with rasps, files and sandpaper, to order for each guitar. A few thousandths of an inch can make a significant difference in feel and playability.
The heel is carved first, then the headstock transition area, and finally the running length of the neck.
The binding channel on the headstock was routed and the trim of cellulose lines glued in and allowed to dry. Eric is removing the tape which holds this trim in place.
The headstock is scraped with a cabinet scraper to level the binding. The final carving of the transition area from headstock to the running stock of the neck is then hand carved with a paring chisel and sanded.
The neck is now ready for the precise fitting of the neck to the body of the guitar. Size, shape and mass of the bridge can have tremendous influence on the sound and performance of the guitar and this is the stage which assures that the playability of the guitar is exactly what is required.
Here we see Petria Mitchell working her magic with her graver on the SJ’s heelcap. A piece of 10,000 year old mammoth ivory has been glued to a block of mahogany and polished to a high luster. Working completely by hand and with no magnification, she will etch the picture desired onto this small surface. Here we see acrylic paint being added to the etching. Ah, but it seems so simple, doesn’t it?! Try it yourself sometime. Ooops! Yes, she IS amazing!!!
Our heelcap is shown in an intermediate stage; the Vermont scene of a Sugar Maple tree and an old stone wall coming into focus.
After the neck angle has been set to the body and the engraving has thoroughly dried, the cap will be epoxied to the neck heel with a super-strong, slow setting epoxy. After final sanding of all parts, it’s off to Larry’s Spray booth where his expert hand will bring the SJ’s various woods to life.
The body and neck of our SJ prototype have been completed. It’s time for finishing! Larry is applying lacquer topcoats to the body. There will be several rounds of spraying, with sanding between coats, followed by a period of curing, final sanding then buffing.
Since the last post… Off camera, lacquer has cured for several weeks. Larry has wet sanded neck and body and buffed both on a stationary wheel to a high gloss. Andy has made a bridge of African ebony. The bridge is positioned with a fixture and its outline scribed in the lacquer of the top with an exacto knife. Once the lacquer beneath the bridge footprint has been carefully removed the bridge is glued to the spruce of the top. Clamping is done with a vacuum clamp.
With no string tension on the neck, the frets have been ground and polished. The frets must be absolutely flat at this point. When the guitar is strung up, the string tension should create proper “relief” in the neck which allows comfortable playing without excessive string height.
Mass and height of the bridge as well as saddle height and string height off the face of the guitar are absolutely critical to best possible sound of each guitar. These factors can vary widely from one guitar to another.
Andy is shown cutting the string leads in the bridge with a jig saw blade.
The glue is allowed to dry overnight. Here we see the bridge pin holes being drilled through the top.
A bone saddle blank has been fitted to the saddle slot and curved to match the fretboard radius. In the setup procedure the saddle is left slightly high until string notches in the nut have been set to their final depth for proper playability.
The bone nut blank is being fitted to the neck. Each one of these is unique and fitted completely by hand. This allows complete latitude for varying the feel of the guitar to the individual player.
Once the shape of the nut has been formed and it is perfectly seated in its channel the first and sixth strings are located and notched for lateral position. Preferences for positioning of these two strings vary widely from one player to another. It’s got to feel just right.
Once the two outside strings have been located, the remaining four strings are located laterally and notched. Spacing between strings must be uniform. After all six strings are positioned properly, their depth is set, saddle height is adjusted and all facets of the setup are given final check and any required adjustments are made.
Here we go! This is like being in the delivery room at the hospital and hearing your child for the first time. If we’ve really done our work well we should know exactly what she’ll sound like with that first note.
What do you think Andy?
It’s a Froggy!
Later today we’ll take her to our friend Tucker Barrett to install her pickup. After all those who have had a hand in her creation have had a chance to try her out we’ll be ready to take her to L.A.C.E. on Sunday.
Everyone who has seen or played this guitar has just been blown away by her voice and her beauty.
A view of the back from the formal photo shoot.
The guitar on display at the Sunday brunch at L.A.C.E.
We have a winner — Chris and Jascha from Warren, VT went home with the guitar at the end of the Jackson Browne concert Monday night. left to right: Andy Mueller, Jackson Browne, Chris, Eric Goodenough, Chris’s wife, Jascha and Michael Millard.