Sunday, December 27, 2015

Building a Louis Panormo - Part 2

I finished the model of a Louis Panormo guitar that was the subject of my post from 10/10/15. It is closely based on a Panormo that I restored in 2014 ( see 7/9/14).

Harris Becker, director of the guitar program at Long Island University Post, had commissioned a renaissance lute and when he came to Toronto to pick it up I showed him the work I was doing on my Panormo. Harris reserved the instrument and last week he was back in Toronto to pick it up.

My previous post about this guitar focused on my description of assembling the guitar on a solera.  The technique requires finishing the soundboard with the rosette in place and most of the shaping done on the heel and slipper foot part of the neck. In this post I will take up the story where I left off.

There are a number of steps that are required before the side ribs can be glued to the soundboard. The first step I had done earlier - drawing the contour of the top on the back of the soundboard before I assembled the fan struts and harmonic bars. The side ribs will be bent precisely to this shape and then glued to the top positioning them on that line.  But the front edge of each rib needed to be trimmed so that it fits in the slot that is cut into the side of the front block. This needs to be a tight fit both for strength and appearance.

The tail block has an interesting shape - fairly wide (80mm) but bevelled on the edges so the maximum gluing surface to the back is reduced while the gluing surface to the soundboard is rectangular and measures 80mm wide by 13mm front to back.  The tail block was previously glued to the top taking care that it was perfectly up-right.

The side ribs are held in place while the glue dries with threaded rod screw clamps.

The  top lining for the soundboard is composed of dozens of small triangular block glue in place separately. I made these from Spanish cedar, the same wood as the neck assembly and tail block. They are glued by setting them in a puddle of hot glue, holding them in place for a few seconds and moving to the next one. I wanted to feel more secure about this technique so I used a small stick of wood the height of the sides and a small spring clamp. After setting the piece in a puddle of glue I place one end of the stick against the top of the rib and the other against the  face of the block. When the spring clamp pinches the rib and stick together at the top, the bottom of the stick pushes the block down against the soundboard and in against the rib.  With a few sticks and clamps I work from one quadrant of guitar frame to another thus allowing the glue a few seconds longer to set-up.

Panormo No. 2154, built 1834

Panormo tied down the ends of the fan struts by gluing the lining block right on top. This was probably his usual method as I have seen this in several of his guitars. Note the toothed plane marks on the side ribs.

The inside linings for the back need to be carefully bent to the proper contour. I made a simple but accurate template out of plywood, heat bent two strips of Spanish cedar and allowed them to set in the form until they were needed.

The back slopes forward from the tail where the rib depth is 92mm to the neck joint where the depth is 87mm. This is not an abrupt change but it is still necessary to account for this when gluing the linings.  The difficulty arises in bending the interior linings because they must conform to both the outline of the guitar and the sloping profile of the sides as well as fitting snuggly against the inside of the ribs.  I employed the same technique as I did when assembling the terz guitar. See my post: Building a Stauffer Terz Guitar - Part 2 from 20/11/15.

Panormo used deep back linings, perhaps because he also used thin sides.  These linings are about 19mm by 3mm.  Of the original Panormo's that I have examined the sides vary from 1.6mm to 1.0mm with perhaps a general thickness of 1.2 - 1.3mm.  Areas on one guitar     measured .5mm! From what I understand about Spanish guitar making tradition, thin sides are standard and Panormo did advertise himself, "Guitars in the Spanish Style". The back linings are tapered to a thin edge. In the photo I lined the side with a strip of duct tape to protect them while I vigorously scraped and sanded the linings to a thin edge.

The back  of the original guitar is arched 5mm across the lower bout, 4mm at the waist and 3mm across the upper bout. I made an arched contouring jig out of flexible plywood about 35cm wide and glued  three concaved forms to it; one with a 5mm arch over the 35cm width, the middle one 6mm and the last 7mm. Coarse sandpaper was glued to the business side of the jig. By thoughtfully rubbing the board over the guitar sides both before the back linings are made (as seen in the photo) and again to level them once they are glued in place I can create a smooth transition from one end of the guitar to the other. When it is time to glue the back with its corresponding arched braces to the sides the contours will match perfectly.

 Here the back is ready to glue onto the sides. There are only two bars. Other early Spanish makers built guitars with only the two lower bars. They obviously felt there was an acoustical advantage and that the size of the slipper foot compensated structurally for the missing third bar.


Panormo No. 2154
The bridge design deserves special attention. This is the original Panormo bridge. The raised front edge acts as a saddle. The bridge pins sit in a trough that is about 6mm deep. As a result the strings have a lot of down bearing. The bridge is ebony and the central block measures 23mm front to rear and 230mm wide. The strings span is 62mm and the string height is 10mm. The "eyes" are add-on pieces but the wings are shaped as part of the central block.

I modified the Panormo design in one important aspect. The raised front edge of the Panormo design is straight and does not compensate for the slight difference in pitch between strings of different diameters when each is depressed. As a result such guitars always play a little out of tune. I modified the front edge by creating a flat surface where the ridge had been and cutting a saddle slot as found on modern guitars.  I then fashioned a saddle in ebony and shaped it to compensate for each string. The result is visible as a wavy line.

This close-up shows the depth of the bridge pin trough, the sharp angle of the strings over the saddle, the high string height and the angled sides of the bridge block.

Since the soundboard is domed a few millimetres I shaped the bottom of the bridge to match.

I used African Blackwood for the fingerboard and small mandolin style T- frets. The tuners are Rogers' replicas of Baker tuners that Panormo frequently used.  I planned to fill the grain of the rosewood and spanish cedar so I applied enough shellac to the soundboard and maple peg head to seal those woods against accidentally staining them.

The Indian rosewood  was filled with a commercial filler with a little burnt sienna  pigment added to the mix to bring out the red undertone. The neck was filled with a light mahogany filler mixed with enough neutral colored filler to lighten the mix.

Once the filler was thoroughly dry and lightly sanded I started applying shellac with a French polish technique using blond flakes dissolved in alcohol. 

After allowing the finish to harden for several weeks I rubbed it down first with fine pumice and finished it with rottenstone using mineral oil as a lubricate.

I'm finishing a thirteen course baroque lute after Hanns Burkholtzer and anonymous E. 25. I'll soon have details and photo album.

All photos by the author.

Sunday, December 6, 2015

Stauffer Terz - a Photo Album

Terry McKenna is a long time friend and client. He had stopped by to pick up a lute repair that I had finished for him. The terz, strung up but unvarnished, was lying on my bench begging to be played. Terry gigs, records, teaches, lectures, tours and has fun playing an eclectic variety of early string instruments. He would have taken it on the spot, but I needed to varnish it.

The back and sides are two different types of maple. The sides are a hard North American maple while the back is a less dense European maple. I wanted to argument the tone of the guitar with a little extra snap or a kind of percussive quality. I thought using hard maple for both the back and sides would result in a brittle tone but using the harder maple for the sides only would be about right.

This created a problem for varnishing. The European maple back was nearly white while the sides ribs were considerably darker. I used several applications of a chicory tea stain to darken the back before I applied any finish. Then I French polished the back and sides with blond shellac.

I put the guitar aside for several weeks to allow the shellac to harden and then I rubbed it out with fine pumice followed rottenstone using mineral oil as a lubricate.

Even though the back and sides are two different species of maple the curl  figures compliment one another.

The soundboard is finished with multiple applications of tung oil allowing each to dry thoroughly and then rubbed out with a lamb's wool pad. It is important to be sure the previous coat of oil is dry before a further application of oil. If it isn't, uncured oil will migrate to the surface over time and result in a permanently tacky finish.

The bridge was sprayed with black lacquer before I glued it to the soundboard. The saddle is a length of T-fret, the same size as I used for the frets.

The neck is finished with black French polish. I add a small amount of lamp black to my usual shellac and alcohol mix and apply it with a small polishing pad. It is important to round off the edges of the peg head sufficiently before beginning the polishing procedure. Otherwise, the polish will not build up leaving bare wood visible .

It is necessary to use a brush to apply polish right into the angle of the heel joint. I use a brush that is shaped to a chisel edge to build up a layer of polish. Alternating with a polishing pad blends the colour onto  the brushed area.

I'm just finishing the polishing of a Panormo model guitar. I last reported on this instrument on 10/10/15 and continuing this story will be the subject of a post or two in the near future.

All photographs by the author

Friday, November 20, 2015

Building a Stauffer Terz Guitar- Part 2

In my last post I focused on constructing the adjustable neck and the corresponding V slot.  Now it is time to describe assembling the body of the guitar.

Since I had cut the V slot before I glued the front block onto the side ribs it was essential the everything remained properly aligned. With the side ribs clamped securely in the mold I then clamped the mold to the edge of my bench with the axis positioned on one of the lines on the mat. Then I glued the front and rear blocks in place.

The back slopes gently toward the waist and then plunges by nearly 15mm to the neck joint. The height of the side ribs are contoured from 77mm at the tail to 70.5mm at the waist and then to 56mm at the neck joint.

 This creates difficulty in bending the interior linings for the back because they must conform to both the outline of the guitar and the sloping profile of the sides as well as fitting snuggly against the inside of the ribs. When the profile is less drastic the linings can be bent and twisted into the proper shape. But here that is not possible. I solve the problem by making my lining material extra deep, bending it to the contour and clamping it to the ribs, letting the extra width overhang. Scribing a line, as shown, denotes the correct profile. A second line scribed parallel to the first and then removing the excess makes the linings uniform in depth.  

Once the linings are cleaned up I complete the frame by shaping and fitting the struts for the top and back. These all follow the size, shape  and placement given on the museum's drawing - with one exception. I added a smaller strut, thinner and lower,  in a position behind the bridge.  I like to assemble the backs and tops in this manner. The ends of the struts fit perfectly into notches in the linings, and as a result, the frame is perfectly stable and remains so when the top and back are glued in place. The three back struts are arched as much as 4mm for the lower bout and nearly 3mm for the upper.

The two lower struts on the top are arched 3mm while the two above the rose are flat. These values are my choices.  I also include a thin maple bridge plate that conforms to the arch of the top. The museum's drawing has no information about arching, nor is a bridge plate part of the original guitar.

I describe my technique for gluing the back and top onto the struts and frame in  "older posts" from 1/20/13, 9/19/11 and 9/10/11.

The original Stauffer soundboard is thin. The area from the bridge through the sound hole and up to near the front block is 2.1 - 2.2mm. Other areas are 1.9 - 1.7mm. I used the same sort of gradation but I started at 2.4mm.

J.G.Stauffer MIM 4152, Berlin

 The museum plans do not include details of the purfling or the design of the bridge. I photographed the guitar but only in its location in a free-standing display case. The photo is of little value because of poor light and reflections.

N.G. Ries, private owner

I do have a Nicolaus Georg Ries guitar circa 1840 in my shop.  I consulted it for the design and details of the bridge, purfling, peghead and neck contour.

The Ries purfling design is similar to that found on many of Stauffer's instruments so I chose a variation of that for my terz.

Because the waist is so tight I didn't trust the strength of the my masking tape to hold the multiple strips in place at the waist. Also, I chose   not to glue on the thicker hardwood outer piece  at the same time as the others. I substituted a plastic strip and glued everything in the normal way. A special purpose caul with a large cam clamp that spanned the waist secured a tight fit. Hide glue doesn't stick to plastic so the next day I peeled the strip off and glued  on the final ebony strip.

The Ries bridge (see previous photo) is a delicate design that was often used by the Viennese builders. The original is made with a hardwood painted black. I photographed the Ries bridge, re-sized it to the dimensions I needed, printed it and from that made a simple template. I chose a piece of European plum, drilled the bridge pin holes and cut the saddle fret slot.

Here's the finished piece ready to be blackened.
Viennese bridges are usually very low. This one is 5mm high, tapering to less than 2mm at the ends. The rear slopes to about 2.5mm.

Next time, I'll post a photo album of my finished guitar with further descriptions and explanations.

All photos by the author.

Tuesday, November 3, 2015

Building a StaufferTerz guitar

I recently finished a model of Johann Georg Stauffer's terz guitar  Cat. No. 4152 in the Berlin Musical Instrument Museum. This guitar was on display when I was in the museum examining their Christoph Koch theorbo several years ago and that piqued my interest.

Many of my lute/baroque guitar clients play 19th century guitar and I have tried to finish one or two guitars a year for the last twenty years. Recently I have been able to spend more time with them; either by scheduling museum visits, doing restorations and repairs and other opportunities. These occasions are recorded in my 'Older Posts'.

A technical drawing for this instrument is available from the museum.

The guitar's dimensions:
string length 554mm
body length 390mm
upper bout 228mm
waist 161mm
lower hour 290mm
maximum rib depth (tail) 77mm, minimum (neck block) 56mm

I built an inside mold  and immediately set about assembling the side ribs. The model has a very tight waist and I was extra careful while making this bend. I made the side ribs about 1.7mm thick over-all but thinned out the waist area to 1.4mm. I wear heavy deer-skin gloves while I bend guitar  ribs. The gloves enable me to cup my hands over the wood and to hold it firmly on the hot iron. In this way I can feel the wood fibers soften and gauge the amount of pressure I can safely apply. I clamped the bent side ribs securely in the mold and set it aside.

The guitar has a raised fingerboard that rides above the soundboard.  The heel of the neck sits in a deep V shaped slot cut into the front block. A simple screw mechanism allows the neck angle to be adjusted with a clock key. It is an ingenious device that was an important  and popular feature of nineteenth century Viennese guitars.

The mechanism is simple in principle but constructing it needs to be done accurately in order for it to operate smoothly. I find it easier to achieve this if I rough out the front block and neck/heel right after the ribs are assembled. This photo show the rear of the block with part of the mechanism in place. The guitar is upside down and you can see the bottom of the slot in the front of the block.

Here is the slot shown in the finished guitar. A wood dowel (shown in both photos)  protrudes through the centre of the upper part of the block. This fits into a blind hole (visible in the next photo) in the rear of the heel.

The dark area is discoloration

The dowel and the surrounding area acts as the fulcrum for the neck to pivot. It also keeps the neck from shifting out of position. The area beneath this is cut back in such a way that only the upper most area is in contact with the rear of the slot. Since the neck pivots on this point the hole must be slightly larger that the dowel.

Here is the mechanism laid out and partially assembled.

From the left, the anchor is the square plate attached to a hollow cylinder that is threaded inside and out. The square part is visible in one of the above photos. It is inlaid into the rear of the block. This keeps it from turning when the mechanism is adjusted. The washer is threaded and securely locks (as shown above) this part of the mechanism in the front block. The hexagon shaped cylinder is open at the front as seen in the photo below, but closed at its rear, except for a hole that allows the adjustment rod to pass through.

The rod passes through the heel. It is threaded at the rear end so that it screws into the rear cylinder. At the front it has a collar (above photo) that holds the rod in the front cylinder. The clock key fits the squared end of the rod.  A quarter turn in direction or the other will change the pitch of the neck raising or lowering the height of the strings above the fingerboard.

This has been a wordy description but here's one last photo that shows the roughed-out nature of the neck. The heel is a separate block glued to the neck. The sides of the heel are cut and planed to the contour that matches the V slot. At the rear part, the heel is cut away leaving a ledge. This is the location of the dowel and the point where the neck pivots in the slot.

And here is the entire neck showing all of the details of its construction. The peg head is attached with a v-joint. The extension that supports the flying fingerboard is attached with a half-lap joint and then tapered to achieve the characteristic Viennese fingerboard.

In the next post on this guitar I'll describe constructing the soundboard, back and bridge and my procedure for polishing the guitar.

All photos by the author.

Saturday, October 10, 2015

Building a Louis Panormo Guitar - Part 1

  I have just about finished this model of a Panormo guitar - it still needs to be varnished. I built this guitar as an extra project when I could borrow time from work on my commissioned instruments so it has taken longer than usual to complete. I always string up my new instruments before I varnish them to see if I need to make any changes - such things are easier to do at this stage. Also I think it is important to allow time for the wood and the various glue joints to acclimatize to both the tension of the strings and atmospheric changes unimpeded by a protective finish. Panormo traditionally finished his guitars with French polish and I am now ready to begin that process.

This guitar is a close model of an 1834 Panormo that I did extensive repairs on last year. My post from 7/9/14 describes that work. While the guitar was in my shop I was able to study it in detail and that provided the impetus to build a model.

The guitar's dimensions:
string length  635mm
body length  452mm
upper bout width  228mm
waist width  177mm
lower bout   286mm
maximum rib depth   92mm (tail)

This show a later stage of construction but provides a convenient talking point
I built the guitar without a mold, assembling the principal parts on plain work board, called a solera in the Spanish tradition. I enjoy the challenge and different perspective that working like this entails as the sequence of assembling the parts is much different than working with a mold. The solera  is not only a platform for assembling the key parts of the guitar but also a sort of template for determining the arching of the top. It is constructed with a depression carved into the wood in the area of the lower bout. When the fan struts are glued in place they and the soundboard are pressed into this depression. The result is a domed soundboard. Domed tops respond acoustically faster with more strength and the possibility of more nuanced tone than flat tops. The depth and shape of the depression helps to determine the tonal characteristics of the guitar. There is disagreement on whether Panormo domed his soundboards in this fashion. I constructed my solera out of well-seasoned pine, cut it to an over-size contour and taking the liberty of doming my model, carved a concavity into the pine in the area under the fan bars.

Next I thinned the spruce top to 2.6 - 2.5mm through the center and tapered the edges  at the bouts to 2.3 - 2.22mm.
The rosette is a double ring; a thin three band outer ring and a wider, multi-band inner ring composed of alternating bands of kingwood and holly wood.

Here's the finished rose at a later stage of construction. The sound hole opening is 86mm wide while the outer ring is 137mm. The thin light and dark rings are each .6mm thick.

 This photo shows how the fan struts glued in place. The seven struts (seen in a previous photo) are positioned in the typical fashion favoured by Panormo; bunched near the harmonic bar then flaring out to the bottom and sides of the lower bouts. I glue them all at once by using foam and wood gluing cauls to force the bars and soundboard into the concavity. Once the glue dries the lower half of the soundboard is permanently domed.

Here the cauls are laid out in order showing the depressions left from  clamping. I like this method because uniform pressure is applied over the length of the struts and they are all glued at the same time.

The neck and heel assembly is a key in the construction of this guitar and others that are built on a solera. The heel block and slipper foot provide structural rigidity and an uninterrupted acoustical pathway from the nut into the heart of the guitar.

Although this style of neck assembly can be cut from a single block of wood Panormo made the heel and slipper out of a single block and glued it to the neck piece with a long scarf joint. Because the scarf runs at a shallow angle (see the second photo down) there is a much larger gluing surface and therefore a stronger joint than would otherwise be the case.

Here's a close up of the original guitar with the scarf joint labeled.

Note that the neck piece (bottom of photo) continues well past the heel and is left square on the end.  Glued to the soundboard it provides support for the top and fingerboard at a critical location and helps to produce strong clear notes in the upper register.

The slipper foot (top of photo) is rounded and glued to the back. It provides rigidity in the transition from the neck to the body.

Original 1834 head

Panormo's peg head design has a simple elegance that I admire. It is constructed from a single block of maple without a capping. The curve at the top of the string slots match the curve of the head and the long broad ramps are accented by the tapered center piece and the finely shaped edges that terminate at the nut.

This design necessitates a blind V-joint so as to not interrupt the simplicity of the face.

I laid out the design in pencil, drilled a very small hole at the point of the V and using a x-acto saw carefully made the two side cuts using the hole as an exit point for the end of the saw.
I then chiseled away the waste portion that left a rough surface since the bottom of the V angled up against the grain. This was smoothed with a file that I re-shaped for specifically for this purpose.

Peghead string slots are always a lot of work, more so using non-speciality tools. Here I drilled dozens of small holes on the waste side of the prescribed line and then finished by cutting away the intervening material.

To finish the surfaces I fitted temporary edge pieces to the peghead stock to make the slots parallel to my bench. I also made two corresponding supports for the file handle that were parallel to the slot depending on its orientation. Progress was fairly rapid.

The string ramps are long but fairly shallow. They are cut below the top surface even at the nut making for a delicate rounded edge at this point.

There's lots more work to do and I'll describe that in one or two future posts.

All photos by the author.