SOUNDBOARD BRACING - TRANSVERSE BRACES

PREPARING THE BRACES

The transverse brace where brought to final dimension in the same manner as the fan and finger braces, width first and then the height; 6.5x14mm for the brace below the soundhole and 7x15 for the two above. At this point I also numbered each brace on the end from 1-3 to be able to easily distinguish the three.

Once the planed to size, the lower transverse brace had to be arched to fit the dome of the lower bout. This was done using and scalpel and a 25' radius template I made. Then the arch was done with my block plane on the shooting board.

CUTTING THE APERTURES
The apertures were cut using a drill press and a 3/8" forstner bit, set up to cut a semi circular hole with the bit extending halfway, about 5mm, into the brace. First I tried to do this without any support to the protruding part of the bit but the bit wandered a little and left as skewed hole. It also left a somewhat rough cut in the soft spruce.

I changed the bit to a bradpoint to see if that would work better, but it did not. Though the cut seemed to be a smoother I had a hard time holding the brace in place. It simply bit into the brace and chewed it up to the extend I had to make myself a new one from scratch.

In the end, I did the cut with the forstner bit and supports clamped to the drill press table on both sides of the brace, leaving a snug fit for the brace to slid back and forth in.

The waste in between the holes was pared away with a chisel - first with broad stroke and then gradually finer until a flat surface between the holes was achieved.

Each end of the apertures were given 3mm long notches, to accommodate for the overlap of the underlying grafts. I used a small ruler as a fence to mark the initial cut by laying it on the braces flush against one side measuring 3mm beyond the aperture and butted the back of the chisel up against the ruler to score a mark, flipped the chisel over and made the 0.5mm deep cut. The waste was pared away in a similar fashion to the bridge graft notches of the fans.

TRIMMING APERTURE GRAFT
The aperture grafts were done a little on the long side to allow for inaccuracies in their initial gluing to the soundboard, cutting of the apertures and their notches. To make a nice fit I had to trim the ends. Each transverse brace were place on top of their corresponding graft and marked with a scalpel.

Then the ends were carefully cut with a 1/4" chisel. I say carefully because the first cut nearly penetrated the soundboard as the chisel went though the graft. The consecutive cuts were done much more caution, less pressure and a little more wiggle and sliding back and forth of the edge. I used the polished back of the chisel to monitor that the cut was executed square to the graft.

Last, the waste was pared away and the braces were ready for a dry fit.

GLUING THE TRANSVERSE BRACES
As with the other braces I had made caul for these out of 1/8" maple, each stuck on with doublesided sticky tape.

I glued the lower brace on first using the 25' radius dish and four go-bar rods. The braces was butted tightly up against the soundhole doughnut and held down with one rod. This work very well in preventing sliding as did the aperture grafts. Once the first rod was in place I added a rod to each of the ends and last a rod was added to one end of the middle section and the first rod was repositioned to the other side of the middle section and after some glue cleaning with a chisel the whole setup was left to dry.

The two upper braces were glued on the same way, however, they were done flat without the dish and in conjunction with the lower fingerboard graft. The fingerboard graft had been fitted to a nice and snug fit that held all three item in place between the soundhole doughnut and the upper fingerboard graft.

PEAKING THE BRACES AND TRIMMING THE END
The peaking was done to with a 3/4' paring chisel in the same way I did the fans, though not to the same extend. Studying photograph's of Jeffrey Elliott's soundboard I tried to emulate the look of his by carving only small bevels, 1/16" x 3/16", across the top starting and ending about 1/2" from the ends, roughly above the outer ends of the apertures.

The end of the braces were trimmed to the template plus about 2mm (the thickness of the sides) with a small razor saw stopping short of the soundboard surface in order to minimize potential marring. The last bit was pared away with 1/4" chisel.

FINAL CARVING AND FINE TUNING
Well, I didn't really do much fine tuning. In Cumpiano's book he mentions that the final graduation of the braces is the ultimate test of the luthier's mastery and that the beginner should just strive to get a clean looking bracing job. I somewhat resigned myself to this. I had a huge urge to start carving away, a temptation I just had to resist as I felt the bracing is on the thin side dimensionally as it is. Also, the whole thing felt somewhat meaningless and arbitrary as I had nothing to compare with.

However, I did try it out a little bit just to see what all the fuss was about, in particular by shaving the peaks down a little on the outer four fans, feathering the ends a little and going over irregularities on the whole. I was fun to listen to the soundboard drop in pitch as it loosened up, though not dramatically so in any way.

It was also quite revealing how big a difference it made to hold the top as well as tapping it in different places. Just by holding the soundboard one way as opposed to another, would change the sound from a dead "Thud" to a distinct "Dooong" and visa versa. I also noticed the bridge area would produce a more ringing sound whereas tapping the periphery seemed to give a more rumbling sound.

I did wonder though, whether I wouldn't have better off doing this final voicing before the transverse braces were glued in place as they were in the way of paring down the fingerbraces and the upper part of the outer fans.

PLANING TRANSVERSE BRACES TO FINAL THICKNESS

MEASURING TRANSVERSE BRACES WIDTH

JOINTING TRANSVERSE BRACES TO FINAL HEIGHT

MARKING THE ARCH FOR LOWER TRANSVERSE BRACE

PLANING 25' RADIUS IN LOWER TRANSVERSE BRACE

DRILLING HOLES FOR THE APERTURES

PARING WASTE FOR APERTURES

CUTTING REBATE FOR APERTURE GRAFTS

PARING REBATE FOR APERTURE GRAFTS

TRANSVERSE BRACES READY FOR GLUING

MARKING APERTURE GRAFTS

CUTTING APERTURE GRAFT ENDS

PARING APERTURE GRAFT END WASTE

GLUING UPPER TRANSVERSE BRACES AND LOWER FINGERBOARD GRAFT

CARVING TRANSVERSE BRACES

CUTTING TRANSVERSE BRACE ENDS

PARING TRANSVERSE BRACE END WASTE

FINAL CARVING

THE BRACED SOUNDBOARD

THE BRACED SOUNDBOARD

THE BRACED SOUNDBOARD - DETAIL

THE BRACED SOUNDBOARD - DETAIL

THE BRACED SOUNDBOARD - DETAIL

THE BRACED SOUNDBOARD - DETAIL

SOUNDBOARD BRACING - FAN AND FINGER BRACES

Initially, when the fan and finger braces were prepared, I had left them oversized and partly jointed with the gluing surface planed flat, some with all surfaces square while others still had sawmarks showing from the bandsaw, but all needed to be planed to their final size, 4x5mm for the three center fans and 4x4mm for the rest.

PLANING TO FINAL DIMENSION
I fabricated a little stop from some soundboard scrap, stuck it to the bench with double sided tape, butted up against two bench dogs. I laid all the braces on the side that was jointed to the bottom or gluing face, butted up against the stop and secured to the bench with double sided sticky tape, and proceeded to plane them all down to a 4mm width, constantly monitoring the progression by carefully measuring the stack around the periphery.

Once the fans were planed to width the whole procedure was repeated, this time with their gluing surface facing downwards. The whole group was planed down to 5mm thickness and the three middle fans were removed and the rest of the stock was planed down to 4mm.

Last, the fans braces were numbered in consecutive order from 1-7 and the fingers braces 8 and 9.

TO ARCH OR NOT TO ARCH...

...... That is the question. There seems to be a great variety in how builders prepare and glue their braces. Some arch the gluing surface to match the desired dome of the lower bout, while others leave them flat and force them into the dome when they are glued to the soundboard, arguing that it will build a certain amount of tension in the soundboard that will make it more lively and responsive.

Whether this is true of not, I don't know, but I decided to go with the latter. If nothing else it saved me from arching the bottom of seven thin pieces of wood.

FITTING AND NOTCHING THE BRACES
First each brace was cut to length with a small dovetail saw.

The next thing to do was to carve out little notches so the fans would fit over the flat bridge graft and the transverse aperture grafts. I carefully marked where the notch was needed on each fan and proceeded by using a little trick I learned from Bogdanovich' book. He basically kept a few pieces of scrap from the corresponding graft that he stuck on top of the vise jaws and used them as spacers for positioning the braces in the vise, leaving them to protrude the exact thickness of the graft.

I used my patternmakers vise for this job, prepped by planing the top of the clamped jaws flat and square. I positioned the braces by having them protrude a little over the shims with only light clamping pressure, enabling me to press them down flush with a piece of scrap spruce, then clamping them fully. Once in the vise making the notch was just a matter of cutting the ends of the notches and pare the waste down flush with the vise jaws.

The two outer fans as well as the smaller finger braces on each side of the soundhole had to be notched to fit the aperture grafts of the transverse braces. This was done in a similar fashion.

These last four braces also need to have to be mitered at one end. The outer fans to butt up against the soundhole doughnut and the finger braces to butt up against the outer fans. This I did it on the shooting board using a sliding bevel set at the corresponding angle as a fence. The braces were stuck to the bevel with, you guessed it, doublesided stickytape.

GLUING THE FAN AND FINGER BRACES

Like the flat grafts, I had made a handful of clamping cauls out of 1/8" maple to distribute the clamping pressure of the go-bars a little. In hindsight I might have made them a little thicker, 3/16' or so, to facilitate this but this is how they ended up this time. Each fan was mated with a caul using double sides sticky tape and a modest film of glue was applied to the bottom of the brace.

First the fan braces went on. I started with the middle fan and worked my way out alternating from side to side, followed by clean up of the squeezed out glue on the previous fan, until all seven fans were in place.

Each fan was initially held down by hand pressure alone until the glue started to grip. Then one go-bar rod was inserted in the middle of the fan holding the brace down into the domed shape. Then a rod was added to each end and last yet another rod on either side of the middle, between that and the end rods, making up a total of five rods for each fan.

CARVING THE FAN AND FINGER BRACES
I experimented a little by using different tools, a block plane, a little shoulder plane, different sized chisels and my little flat soled Ibex finger plane. I ended up using a 3/4" paring chisel for the 'peaking' or carving the cheeks.

In Cumpiano's book he suggests holding the chisel like a pool cue when carving the cheeks, however, I found 'pinching' the edge of the chisel against the fans gave me more control. This way the fingers holding the edge functioned like a fence preventing the chisel from accidentally slipping and marring the soundboard while the other hand controlled the force as well as the cutting angle. I found a wider chisel the worked better for the particular method.

It was quite revealing how even slight changes in grain direction impacted the ease of the carving. With the grain it presented no problem, but as soon as it was against the grain, I could feel how the chisel wanted to dig in. Sometimes I ended up changing direction and started to carve from the other side, while other times it was purely a matter of taking less material of at each stroke to prevent tear out.

In the beginning I also tried to even out small irregularities from the chisel with a few strokes of the finger plane, but I eventually gave that up, partly because it was difficult to hold the plane off the soundboard and partly because the chiseling eventually got smoother as the work progressed and I started to get the hang of it.

The feathering of the end of the braces was done with a 1/4" paring chisel followed by a few strokes with the finger plane. I found the narrower chisel easier to control as the corners of the edge were less prone to dig into the soundboard once the ends started to thin out.

Once all the fans had received their preliminary carving the finger braces were glued on flat and carved in the same manner as the fans.

LAST THOUGHTS
Even though I tried to be very careful with my chisel I did mare the soundboard several places during the carving. I found the biggest problem was that curls generated by the chisel obscured my vision of the corner of the chisel closest to the soundboard and it was hard to follow when it was getting to close (or digging in). And it was virtually impossible for me to feel it when it happened as the chisel went through the soft spruce so easily.

Some builders advocate precarving the braces before gluing them as this minimizes the potential marring of the soundboard. This, I believe, is a very good idea, however, I also speculate that the clamping would have to be done with specially made cauls that would fit the pracarved profile or with something other than a go-bar deck.

FINAL PLANING OF FANS

MEASURING FAN WIDTH

MITERING OUTER FINGER BRACES AND OUTER FANS

MARKING THE NOTCHES ON THE FANS

CUTTING BRIDGE GRAFT NOTCHES

PARING BRIDGE GRAFT NOTCHES

GLUING THE FANS DOWN

PARING THE FAN 'PEAKS'

FEATHERING THE FANS

MARKING FINGER BRACES

CUTTING GRAFT NOTCHES

PARING GRAFT NOTCHES

GLUING THE FINGERS DOWN

PARING THE FINGER 'PEAKS'

FEATHERING THE FINGER ENDS

HUMIDITY CONTROL ON A SHOE STRING

It's been raining a bit recently here in Southern California. Needless to say that humidity have gone up, which is something that is close to lethal when you glue braces on your soundboard.

I have a two hygrometers, one that sits in a clock I have on the wall in the garage/shop, and a little digital cigarbox one I bought a while back for our piano. I while ago I took the little one out to the shop only to find that they were not displaying the same value at any given time. When the digital one showed 38% the analogue one in the clock read 58%. I couldn't believe that they are so far apart.

Two weeks ago I took my little digital hygrometer with me to my local wood and tool shop Rockler, who sells analogue hygrometers for clock makers. I wandered about in the shop until mine had settle and compared it to the ones they had on display. They all consistently read about 9% higher than mine. When I got home I adjust my shop hygrometer down about 10% and have used that as my reference, and now it is at least fairly consistent with the local weather forecast. I'm still not sure how precise it is and I might try and go to one of our local museum and compare it to one of their hygrometers. They should be quite accurate.

But to deal with the damp weather conditions, I choose to try out a trick from Bruce Hoadley's book "Understanding Wood". He suggests wrapping your wood in plastic until humidity is back to normal.

I'm in the middle of bracing the soundboard and hope to avoid to many unpleasant surprises. Ideally you want to get the soundboard braced and glued on to the body in a close to ideal humidity conditions as possible, otherwise you will be in for some nasty surprised later on.

A fellow builder from LuthierForum just posted several pictures of what looked like someone had stuck a hose to the soundhole and sucked out all the air from the guitar. It was not a pretty sight. Basically he had been building in too humid condition and when the guitar settled in the drier indoor winter air, the thin soundboard and back had contracted and caved in showing all the braces that were still trying to hold these plates in place.

Nasty business!!

HUMIDITY CONTROL ON A SHOE STRING

SOUNDBOARD BRACING - FLAT GRAFTS

INITIAL PREPARATION

Before any of the grafts could go on I traced the whole bracing lay-out onto the top very lightly with a soft pencil using the soundhole center and glue seam as reference points. Once that was done I cut the soundhole with my little Dremel router and a 1/16" carbide downcut spiral bit.

Before cutting the hole, I lined the bottom of the circlecutter attachment with cellotape to prevent the smudging I got when the rosette channels were done. The hole was cut it in two goes. First a little more than halfway down with the rosette facing up, then a second run with the soundboard flipped over with the rosette facing down. This was done to minimize potential tear out.

I also made clamping cauls out of 1/8" maple for all the braces and grafts.

GLUING THE UPPER FINGERBOARD GRAFT - FITTING THE SOUNDBOARD TO THE NECK
As I mentioned in the previous post, the final fitting of the soundboard to the rebate on the neck had to be done on the upper fingerboard graft, so that one went on first. In order to keep things aligned I clamped the adjacent transverse brace in place as a reference to but the graft up against. The bottom of the brace was covered with non stick cellotape to prevent the glue from the graft to adhere to it. Having the brace in place also helped preventing the graft sliding around in the wet glue. The squeezed out glue was cleaned up with a chisel.

When the glue had dried, the top of the soundboard was cut down to the template line with a saw and trimmed to fit with a plane on the shootingboard. As the graft was slightly wider than the neck, little notches were made at the end of the graft to allow for the sided. Likewise, about 3/16" of the lining on each side of the neck was pared down flush to the rebate.

When I did the clamping cauls for the braces, I also made a 'slope', a thin piece of maple tapering in thickness from 3.0mm to 1.5mm, that eventually will be stuck onto the solera to set the neck angle.

This slope was used as a guide for planing a slight taper into the fingerboard graft. I knew that the depth of the soundboard rebate was about 3.6mm, matching the desired thickness of the soundboard and graft at the 12th fret. Getting the right taper and thickness was then simply a matter of calculating where to place the slope on the soundboard and plane away until the correct thickness was achieved. However, I left it slightly proud to allow for some final sanding.

GLUING THE SOUNDHOLE DOUGHNUT
Next up was the soundhole doughnut. This was glued on in a similar fashion to the fingerboard grafts, thus with the two lower transverse braces as guides.

PREPARING THE TRANSVERSE BRACE APERTURE GRAFTS
One thing that I have chosen to modify from the original plan is adding little 0.5mm flat graft under the aperture of the three transverse braces. This is something that Jeffrey Elliott, who I loosely modeled the bracing pattern after, does. These were fabricated from soundboard scrap by planing an oversized piece down with my jack plane. They ended up a little thicker, about 0.58mm, but I figured that was close enough.

Once the stock was thicknessed, three individual graft strips were cut with an Exacto knife and trued on the shooting board until the strips were the right width, each matching their mating transverse brace. This was a fiddly and floppy affair and I had to clamp a little improvised fence on the shooting board to butt the graft strips up against while holding them down with one of the clamping cauls I made for the braces, to keep them straight in place.

Last, the grafts were cut a little proud of their intended length with a chisel. The final trimming will be done once the transverse braces are ready to be glued on.

GLUING THE TRANSVERSE BRACE APERTURE GRAFTS
For this, I wrapped three of the fan brace cauls in cellotape, marked their centers and stuck the grafts onto them with double sided sticky tape, using the already made transverse brace apertures as reference, keeping the grafts straight and flush to one side of the caul. I also placed a little, equally thin shim in the middle of the caul to support a go-bar rod.

When it came to the actual gluing, the upper fingerboard graft and rosette graft were used as guides to butt the cauls up against. First a go-bar rod was added to the center of the caul to hold it firmly in place. Two go-bars were then used added to each graft.

The four top aperture grafts were all glued on flat, while the two lower grafts were done together with the bridge graft on a the 25' radius disc.

GLUING THE BRIDGE GRAFT
This graft was originally done back in July together with the soundhole doughnut and the fingerboard grafts. However, when I revisited the soundboard thickness and thinned it further than I initially intended to, I also started to wonder if 2mm wasn't on the thick side for the bridge graft.

My Israeli luthier buddy, who got me onto the soundboard deflection testing, sent me an article about the Dutch born luthier living in Granada called Rene Baarslag. I the article Baarslag explains how he goes about the thinning his bridge graft, which is about 1mm thick and feathered to nothing at each end.

I have read about other notable luthiers, Romanillos being one of them, speculating about the need for such a graft in the first place. Torres didn't use them and neither has many other world renowned builders that followed in his footsteps.

Rightly or wrongly, I decided to thin my bridge graft to 1mm, flat across the entire length, and with that also making some equally thin spacers for when the fans will be notch. More about that when the fans are going on.

Last the bridge graft and the lower transverse brace aperture grafts went on. This was all done on the 25' radius dish. The bridge graft was the only graft that went on 'freehand' without any reference points to hold it up against. Needless to say that I was a little nervous about it. I applied a modest film of glue on pressed the graft down on the soundboard with my hands. A little sliding did happen initially but eventually the glue started to grip and go-bars were added one at the time starting from the center of the graft and working my way outwards in both direction, slowly letting the glue set for a little before adding another. Once the glue had dried a little the squeeze out was carefully cleaned up with a chisel.

A COUPLE OF NOTES
This is the first time I use a go-bar deck as a clamping device and I must confess that I love it. I don't know how it would have been in comparison to use regular clamps, but the go-bar was a breeze to use - efficient and precise.

Prior to gluing I used a little plumb to mark the underside of the go-bar clamp to roughly know where to put the go-bar rods. This made for a nice, straight downward clamping pressure that also minimized the chance for sliding before the glue was gripping.

TRACING THE BRACING PATTERN

CUTTING THE SOUNDHOLE

GLUING THE FINGERBOARD GRAFT

TRIMMING SOUNDBOARD TOP

TRUING THE SOUNDBOARD TOP

PARING THE LININGS FLUSH TO THE REBATE

SLOPING THE FINGER BOARD GRAFT

GLUING THE SOUNDBOARD DOUGHNUT

GLUE CLEAN-UP

PLANING TRANSVERSE BRACE APERTURE GRAFTS

MEASURING GRAFT APERTURE GRAFT STOCK THICKNESS

ROUGH CUTTING TRANSVERSE BRACE APERTURE GRAFTS

TRUING THE TRANSVERSE BRACE APERTURE GRAFTS TO WIDTH

CUTTING TRANSVERSE BRACE APERTURE GRAFTS TO LENGTH

GLUING TRANSVERSE BRACES APERTURE GRAFTS

PLANING BRIDGE GRAFT AND NOTCH SPACERS

GLUING THE BRIDGE GRAFT