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Author: Subject: Something Completely Different - Metal Bowls - and a Colascione
jdowning
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[*] posted on 1-20-2015 at 12:32 PM


Due to the curvature of the end of the bowl it has been decided to make the wooden clasp in three main section to obtain a close fit.
The lower part of the clasp is to be made in segments hot bent to fit the curvature of the bowl with ebony lines between the segments. Not sure how this will work out.
A rubbing on paper was first made of the end of the bowl to determine the approximate size and geometry of the segments.
The ebony lines were easily bent on the attachment to my propane heated bending iron - specifically designed for bending lines and purfling. Ebony is brittle so plenty of heat is required with gentle persuasion to avoid breakage.
The attached image shows the clasp segments, with lines glued in place, roughly assembled. These will now be fitted and glued together on the bowl before final trimming and shaping.

All a bit fancy to set off against the plain metal of the bowl.
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[*] posted on 1-24-2015 at 10:35 AM


To obtain a close fit to the bowl, the segments of the clasp lower section must be fitted and glued together on the bowl itself.
The bowl was first covered with kitchen KlingWrap plastic film as protection and the individual segments cut to size, joints planed flat and glued together piece by piece using adhesive tape to hold everything together as work proceeded. A bit like making an oud or lute bowl.
Fish glue was used as a strong quick drying adhesive - soluble in water so adjustments can be made in the event of any inaccurate fit. This is a tricky fitting and assembly task hence the benefit of using ebony lines at the joints to disguise any slight discrepancies - an old luthier secret! In the event only one joint required resetting the remainder being OK.

The back of the assembly was then covered with thin cotton cloth glued in place - for strength when being handled and shaped at the next stage.

The rough assembly was then smoothed with a single cut file and trimmed to a close to final shape with a fine razor saw. Figured maple and ebony are brittle woods to work with so a sharp file is required for all shaping work. The file also smoothly cuts the wood so that the maple is not stained by fine ebony dust (as it would be if abrasive sand paper was used).

A central ebony disc - hand filed to fit - has yet to be glued in place. A contrasting brass button will eventually be installed on the disc for attaching a shoulder strap required for supporting the completed instrument when being played.
As an additional decorative feature, the maple pieces are to be 'fluted'. This will also provide additional flexibility of this component for a close fit when finally clamped and glued to the bowl.

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[*] posted on 1-25-2015 at 11:25 AM


The fluting is made with a half round file and finished with a curved cabinet scraper. Guide slots are first made with a round file in each section to prevent the half round file slipping sideways while filing and causing damage.
This component of the clasp is now almost complete and ready for final fitting and gluing to the bowl.
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[*] posted on 1-26-2015 at 01:58 AM


Wonderful little hand fan !
Very tasteful, as usual, John. :applause:
Can't wait to see the wood/metal combination.

Robert
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[*] posted on 1-26-2015 at 07:37 AM


The design will be dictated in part by the wood to metal physical considerations so may change and evolve as work proceeds.
The attached image shows the remainder of the clasp partly assembled to give some idea of how it should look when finished. What started out to be a basic simple construction is getting a bit more fancy!! The clasp and side strips on the bowl will look even more decorative once varnished as they are made from highly figured tiger stripe maple.

Additional interior reinforcement of the bowl rib joints has been achieved with tabs soldered in place.
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[*] posted on 2-10-2015 at 07:49 AM


The wooden clasp and side strips have now been glued to the metal bowl with epoxy cement ready to be trimmed.
I do not use epoxy for instrument construction so have not tested the effectiveness of this particular brand by 'PC' but it seems to work OK for wood to metal joining. It is a two part epoxy and comes in a convenient dispensing double tube. Unlike hide glue where maximum joint strength requires perfect fitting of smooth surfaces, epoxy has some gap filling latitude but requires the surfaces to be 'roughed up' for optimum joint strength. The joint surfaces must also be 'squeaky' clean. The metal surfaces were first washed with detergent and then cleaned with alcohol. Epoxy is messy stuff to work with so plastic gloves must be worn and metal surfaces protected with painter's tape against any cement squeeze out.

The thin metal edges of the bowl are quite flexible so conform to the hot bent wood pieces - too well as it happens - as there is now some slight deformation of the edges of the bowl but the edges are now suitably stiffened by the wood.
To level the edges of the bowl some material must be trimmed - the precise amount determined in the usual manner by laying the bowl inverted on a flat surface (packed equally levelled front and back) and tracing around the bowl with a pencil. In this case a flat sided carpenter's pencil was ideal for the job. The maximum amount of material to be trimmed is about 2-3 mm.
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[*] posted on 2-10-2015 at 03:18 PM


The sides of the bowl have now been trimmed using a fine razor saw to cut a guide line for a knife to cut completely through the wood components. The exposed surplus metal was then removed with curved tinsmith shears and filed level. Furthermore the exposed edges of the metal ribs have been filed at an angle (towards the inside of the bowl) to a 'knife edge' to minimise the amount of metal needed to be removed for the final levelling operation on an abrasive surface.
Getting close!

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[*] posted on 2-12-2015 at 07:09 AM


Now that the bowl distortions resulting from fabrication work have been corrected and the bowl edges levelled the sound board geometry (determined by tracing around the bowl edges onto card) must be adjusted to determine final bridge position and sound hole position and diameter - the latter dimensions dictating the position of the two braces. Wooden supports for the brace ends have yet to be glued to the bowl interior as hot hide glue will be used for gluing sound board to bowl.

At the same time the volume of the bowl has been measured and is 3660 cm. This is needed in order to calculate the air resonance frequency.

From the revised geometry, the bowl is about 4% larger than the Dean Castle model so string length will be 79 cm rather than 76 cm. It has been decided to have three (rather than four) single strings as on the Dean Castle original. Three single strings appear to have been the norm for colascioni of the 17th C. Tuning will be (A440 standard) G 98 Hz g 196 Hz d' 294 Hz. String tension per string will likely be in the 4Kg to 4.5 Kg range.
Calculated air resonance frequency with a sound hole diameter D of 7.8 cm - assuming a 'dead zone' diameter of 0.67D - is 177 Hz, just about 2 semitones below the pitch of the middle string which should be about right. We will see!
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[*] posted on 2-12-2015 at 07:14 AM


I am loving your progress on this John!

very intrigued to hear the results! do you have a lute of similar dimensions so we can hear the difference?




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[*] posted on 2-12-2015 at 09:44 AM


Hi Samir - no I do not have a lute of similar dimensions to this so I am looking forward to the final acoustic result as well! The project will provide some additional data concerning air resonance frequency determination.

I also intend to fret the instrument with Pythagorean fret spacings - as the early Tanburs on which the Colascione is thought to have been based would have been fretted (as were the early fretted shorter necked ouds). The Pythogorean spacings are determined by ratios of string division 1:2, 2:3, 3:4 and so on. This means 18 frets to the octave (compared to 12 for the European equal temperament fretting) - additional double frets being at the 1st , 3rd, 6th, 8th, 10th and 11th positions. The long neck allows sufficient space between the double frets at these positions (about 0.6 cm to 1 cm). However, more on that later.

For those interested in the air resonance calculation see the attached sheet. This assumes that the inner area of the soundhole (diameter 0.67D) that I call the 'Dead Zone' has minimal participation in the resonant air flow through a sound hole - confirmed by my recent resonance chamber trials reported recently on the Forum.

http://www.mikeouds.com/messageboard/viewthread.php?tid=14874

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[*] posted on 2-18-2015 at 12:00 PM


The remaining wood/metal interfaces have now been epoxy glued to the bowl and levelled - these are two short liners that the brace ends will be glued to and a maple plate glued to the neck joint position to cover the ends of the metal ribs. The liners will stiffen further the area in which the sound hole is located.
A decorative metal collar has also been glued to the bowl at the neck block position as additional reinforcement of the ribs. All that remains is to finish and clean up the wooden components.

The neck and peg box have been drawn full size and will be made from solid maple. The neck joint will be slightly narrower than on the Dean Castle instrument.

I have a number of sound board blanks in stock glued up and ready for finishing. The smallest of these is a two piece rough sawn spruce blank. Nothing special but it has a 'ring' to it when tapped that sounds promising. The wood was cut from a log years ago on a large commercial, power feed band saw with a 6 inch wide blade so the saw marks are quite deep. The first task then is to hand plane the saw marks out. The sound board will then be reassessed for suitability.

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[*] posted on 2-19-2015 at 12:38 PM


The current low humidity winter conditions (about 45% RH) are ideal for working the sound board. The neck blank material must also be brought into the house from covered outside storage for final drying.

The neck and peg box proportions have been determined from full size drawings and a template for the peg box has been made from card. For ease of working/handling and economy of material the peg box will be made separate from the neck and the two parts joined together with a glued 'V' joint. The original had neck and peg box made in one piece.
No CAD (Computer Aided Design) drawing here!

The peg box is similar to that of a violin as found on original colascioni. To keep things as simple as possible and avoid fancy, time consuming carving, the head of the peg box will be left with a plain flat 'scroll' to which some decorative embossed detail will be added.
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[*] posted on 2-19-2015 at 01:56 PM


I am looking forward to hearing more about your fretting approach.



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[*] posted on 2-20-2015 at 10:56 AM


This colascione when complete will be very much an instrument for 'hands on' research including fretting (and, hopefully, so advancing my limited knowledge and appreciation of the complexities of temperament as applied to fretted instruments). Research into the instrument is ongoing.

It is generally accepted that the colascione (or calascione) was introduced to Naples, Italy by Turkish prisoners in the late 15th C where they were observed playing a long necked three stringed instrument - shaped like a spoon - that they called a 'Tambura'. It is impossible to now know what form of 'Tambura' or long necked lute was being played from the multitude of types in use across the entire Ottoman Empire or how it was fretted or the musical style - even if we knew from where in the Ottoman Empire the prisoners in Naples came from. No doubt the style of music and unfamiliar intonations raised admiration among the local population allowing the performers to be eventually integrated into Neapolitan society so starting a long tradition with this new instrument the colascione.

The colascione's Turkish (i.e. Ottoman Empire) origins tend to be confirmed by early writers Marin Mersenne (1636) who compares the colachon (French for colascione) to a single stringed Turkish instrument (that looks like a Tanbur), Kircher (1650) who calls the instrument "A type of Turkish Trichord commonly known as a Colachon" and Bonanni (1776) who published an engraving of a "Calascione Turchesco" that again looks like a Tanbur - see attached images.

Both the Mersenne and Kircher engravings of a Colachon although unlikely to be precise in their execution indicate some peculiarity of the fretting. Mersenne identifies the frets by number and French tablature alphabet icons but makes no mention of fret spacing in his description of the Colachon. The description of the fretting may be in some other part of his massive theoretical work but I have yet to find it. Both authors show some closely spaced frets - here identified in the Kircher engraving - where each fret closer to the nut is drawn heavier in gauge than the lower fret of the pair - an arrangement that would be necessary to avoid string contact with the lower fret when stopping the upper fret. Exactly what the fretting is meant to be is not clear but may suggest some kind of quarter tone fretting?

The performance of the colascione in the folk idiom may have had a strong middle eastern flavour Here is how it appeared to Englishman C. Burney visiting Naples in the late 18th C.
"The national music here is so singular (i.e. unique) as to be totally different, both in melody and modulation, from all that I have heard elsewhere. This evening in the streets there were two people singing alternately; one of these Neapolitan Canzoni was accompanied by a violin and calascione. The singing is noisy and vulgar, but the accompaniments are admirable and well performed............ The modulation surprised me very much: from the key of A natural, to that of C and F, was not difficult or new; but from that of A, with a sharp third, to E flat, was astonishing; and the more so, as the return to the original key was also so insensibly managed , as to neither shock the ear, nor to be easily discovered by what road or relations it was brought about". Burney then later describes a similar experience with a singer accompanied by a colascioncino (or discant colascione), mandoline and violin he again writes "It is a very singular species of of music, as wild in modulation, and as different from all that of the rest of Europe as the Scots (?!), and is, perhaps, as ancient, being among the common people merely traditional"
Other writers have commented in a similar vein describing sudden modulations (to the European ear) from major to minor keys.
We will never know but I have to wonder if what these writers heard was similar to Anatolian folk song, with baglama saz and frame drum accompaniment, as performed today?


Saz fretting is variable but an interesting article in English describing the fretting and other aspects of performance can be found here:

http://www.khafif.com/rhy/saz

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[*] posted on 2-20-2015 at 11:22 AM


Another point of interest is that the Saz comes in a variety of sizes, open string length 112cm (Meydan), 104cm (Divan), 88cm (Baglama), 80cm (Tanbura), 56cm (Cura Baglama) and 48cm (Cura Tanbura) and so does the colascione to judge from surviving museum specimens.
So the full size colascione would have been in the range 100cm to 114cm string length, the Mezzo-colascione in the 70cm to 95cm string length range and the colascioncino with a string length around 50cm to 57cm range (i.e. tuned an octave below the large colascione)

So my experimental Mezzo-colascione with a 79cm string length is about equivalent to a Tambura saz.
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[*] posted on 2-23-2015 at 11:33 AM


The neck and pegbox will be made from Sycamore (a kind of soft Maple) as I have several sawn planks of this wood purchased from a wood yard 40 years ago as old air dried surplus stock. The planks were black though exposure to the air so goodness knows how long they had been in store before I bought them - several decades no doubt - so the wood should be pretty stable by now.
Rough blanks for the neck and pegbox have been cut and are final drying in a warm kitchen at low Relative Humidity.
There is some organic stain in the wood (due to the high sugar content of the wood prior to air drying) - typical with this species of wood. The stain does not affect wood strength and is otherwise of no consequence as the neck and pegbox will be stained black when completed.

The neck joint is currently being fitted using the drawing board as an accurate layout surface. The neck joint is to be vertical - as on an oud - not sloping as on a lute as there is plenty of width available at the neck joint. The neck joint will be reinforced with a screw through the neck block.

The Dean Castle colascione is not perfectly symmetrical the neck being offset to the bass side, the grain of the sound board wood sloping towards the treble side and the joint of the two piece sound board being made well over on the treble side. See my attached sketch made when the instrument was examined 35 years ago.
My project colascione will not replicate this asymmetry.



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[*] posted on 2-24-2015 at 09:54 AM


My sketch illustrating the Dean Castle colascione's lack of symmetry is, of course exaggerated but it does bring into question the sound board originality when compared to the costly construction of the rest of the instrument (ivory/ebony ribs, ivory engraved panels and the carved ivory lion or dog head on the pegbox).
It should be remembered that many of the old instruments in the European museum collections are fakes - from the workshop of instrument dealer Leopoldo Franciolini actve in Florence between 1890 to 1910 - sold then to unsuspecting antique instrument collectors. These 'instruments' may have been completely bogus or made from some genuine parts recovered from original instruments or, at best, mostly original with some 'improvements' or repairs. Most have been weeded out from the major instrument collections and properly attributed to the 19th workshop of Franciolini.

As I recall, a number of the instruments in the Dean Castle collection that I examined at the time were suspect in my opinion. The colascione appears to compare in proportion and construction to some of the other genuine colascioni in the major European collections (see attached images - including that of the Dean Castle instrument). However, the sound board, bridge and rosette, being of lesser workmanship/materials than the rest of the instrument, may be later additions - possibly at the hands of Franciolini?
For comparison a 'lute' in the Stearns collection of instruments - originally purchased from Franciolini - has a parchment rosette similar (but superior) in design and execution to that of the Dean Castle instrument. See attached images.

Not that any of this will have much influence on the design of this experimental colascione that is only inspired by the Dean Castle model and is obviously not intended to be a copy apart from the general proportions.

One interesting point of detail seen in the attached images as well as in the iconography is the positioning of the three tuning pegs - sometimes one on the treble side of the pegbox sometimes two. The 'logical' arrangement might be to have the two pegs on the bass side for convenience of tuning - the second and third courses being tuned an octave apart? (Unless, of course, a player is left handed).

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[*] posted on 2-26-2015 at 10:07 AM


Due to persistent extreme sub zero temperatures it is best not to run machines in my unheated main workshop such as the band saw. Progress is therefore currently restricted to limited work with hand tools and set up/layout work that may be done in comfort of the house.

Now that the neck joint has been made, the neck blank must be temporarily attached to the neck block in order to layout the neck geometry and adjust neck alignment. The neck has, therefore, been attached with a long wood screw passing through a hole drilled in the neck block. This hole was drilled by hand and rises at a slight angle to the surface of the neck joint towards the fingerboard surface. For everything to remain in alignment after the screw has been tightened a pilot hole at exactly the same angle as the screw hole in the neck block must be drilled in the neck blank.
This was achieved by first making a guide hole for the drill in the neck blank with a nail of the same diameter as the screw hole. The bowl was placed and held in correct alignment with the neck blank and the nail - guided by the screw hole in the neck block - was driven a short distance (about a cm or so) into the neck blank with a hammer. The resulting short hole in the end of the neck blank was then used to guide a drill bit of the same diameter as the nail to lengthen this pilot hole for the screw.
For this operation a standard wire nail had to be modified by filing the pointed end into a flat surface - in effect making the nail into a punch. Otherwise the pointed end of the nail - acting like a wedge - would have followed the wood grain and thrown the guide hole out of alignment.

So far so good. Now to temporarily assemble the neck blank to the bowl.



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[*] posted on 2-26-2015 at 10:45 AM


With the screw fully tightened the neck joint surfaces are a perfect fit so work can proceed with establishing the final centre line of the neck in relation to the bowl and to check that the upper surface of the neck blank is in the same plane as the sound board. As it happens the final centre line is offset by about 4mm from the centreline of the blank at the nut position. No problem as plenty of extra material has been allowed in the oversized blank.
The plane of the neck upper surface - checked with a metal straight edge - is in perfect alignment with the sound board joint surface.

As it is difficult to assess how much 'pull up' of the neck under full string tension - if any - there will be, I will probably plane back the finger board joint surface a few mm and make the fingerboard correspondingly thicker at the nut end. This will allow for some action adjustment (by planing back the fingerboard) in future without having to reset the neck.

If the neck is to be glued to the bowl with hot hide glue then the screw will be replaced with a nail that may be driven quickly into position with a few taps of a hammer before the glue has had time to gel (a second or two). This is the traditional method used by European luthiers, the nail (or nails) providing proper alignment and clamping force as well as some reinforcement of the neck joint.
On the other hand, if a screw is to be used a slower setting synthetic glue - such as PVF or epoxy must be employed. I am tempted to use the latter adhesive for convenience given the good alignment of the neck at this stage. Should this be the decision, the screw will be waxed before assembly so that it may be easily removed at a later date allowing the neck to be cut off with a saw should any neck reset work be necessary.

Lots of waste material now to be removed from the neck blank!

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[*] posted on 2-27-2015 at 11:55 AM


For ease of handling the peg box will be made separately from the neck (rather than in one piece with the neck).

The sides of the peg box taper from nut to 'scroll' so the first step is to drill the three pilot holes for the pegs through the parallel sided blank to ensure that the pegs when fitted run 'square' to the peg box.

The sides of the blank are then cut and planed smooth to the required taper.

Finally the profile of the peg box is laid out on the tapered blank, cut out and shaped approximately to size with a coping saw and wood rasp. The cavity of the peg box will next be carved out before the peg box is finished to size.
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[*] posted on 2-28-2015 at 11:45 AM


Before cutting the pegbox cavity, the three peg holes have been cut to size with a peg reamer. This provides full peg box width guidance for the reamer. The peg arrangement - unlike the Dean Castle model - is to be two pegs on the bass side and one on the treble side

The first step in cutting the pegbox cavity is to drill out as much waste material as possible. The cavity is then carved out close to finished size with chisels. As on the Dean Castle colascione the cavity is wider at the top of the pegbox and tapers down to a width of about 5 mm at the bottom.

The neck blank has now been trimmed of most of the waste material and is being allowed to season further in a warm dry place before being finishing to size. This will allow any hidden stresses to be dispersed - stresses that might otherwise cause deformation of the completed neck.
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[*] posted on 3-1-2015 at 12:45 PM


The first sound board blank has grain 'run-out' revealed by planing so is rejected and a second choice has been selected from stock. This sound board blank has already been partially worked so will save a bit of time. Final thicknessing has been done first with a fine set block plane working across the grain direction alternately, followed by a cabinet scraper to remove any plane marks and bring the surface to a smooth and level state. Final finishing is done with a scraper blade that cuts to produce fine shavings. I never use sandpaper that abrades the wood surface to produce an inferior finish.

The two braces have been cut and planed from a piece of spruce split from a billet rather than sawn. This ensures that there is no grain run-out for maximum strength and sound transmission. The edges of the braces have been cut straight and square on a shooting board.
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[*] posted on 3-3-2015 at 12:21 PM


Peg box meets neck!

The peg box has been glued to the neck blank with a simple scarf joint. A wooden dowel will be added later for additional strength. The peg box and neck will now be carved and finished as one piece.

I do not make violins so this violin type carved peg box is a first for me. The decorative 'scroll' will be kept plain and simple to save time.
To level and finish the bottom of the peg box cavity a scraper tool has been made from a cheap screwdriver. The screwdriver tip has been ground to an angle and sharpened and honed like a chisel. The sharp cutting edge is then turned into a hook by forming a burr on the sharpening oil stone. This burr - that would normally be removed when sharpening a chisel - is left in place and removes fine shavings when used as a scraper - being dragged along the bottom of the cavity.
Screwdrivers are low cost readily available tools and are made from hardened steel so can be used to quickly make custom purpose wood chisels.

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[*] posted on 3-4-2015 at 12:37 PM


The sound board has been planed and thicknessed - measuring about 2.5+ mm over the neck block area reducing to about 2 mm at the sound board edges. The sound board edges may be later cut for a half depth binding - as on the Dean Castle model. The surface will be hand scraped to final finish after the sound hole has been cut and prior to bracing.

The sound hole will be open as on a guitar so that experiments with different diameters may be carried out. Later, a fancy parchment rosette may be added similar to that on the Dean Castle colascione.

I cut open guitar sound holes - for speed, accuracy and convenience - with a router that has a baseplate modified with a series of radial placed holes at different radii from the cutter bit. The router then spins around a nail to cut the required diameter.

The sound board blank is first firmly clamped to a flat piece of MDF board and a standard nail of appropriate diameter is hammered vertically through the sound hole centre in the blank into the board underneath. The nail is then cut off to a short length (about 5 mm or so). The nail is then positioned into the appropriate hole in the base plate to cut the required diameter. Needless to say, care must be taken to check (and double check) that the set up is correct before starting up the router!
For this project I used a solid carbide router bit 3 mm in diameter set to cut a slightly oversize sound hole diameter of 8.4 cm (compared to 7.9 cm calculated). This will give some scope for adjustment of sound hole diameter later. The router bit is set to a depth that cuts through the full sound board thickness and partly into the MDF board underneath.

So far so good. A nice clean vertical circular cut of the required diameter.

This method can, of course, also apply to the cutting of oud circular sound holes.

[file]34616[/file] [file]34618[/file] [file]34620[/file]
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jdowning
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[*] posted on 3-5-2015 at 12:24 PM


The X-ray image of the Germanisches National museum colascione previously posted show a guitar like bracing - relatively wide braces on each side of the sound hole with their ends set into shallow supporting pockets cut into the interior rib liners. As wooden liners are a necessary part of the metal bowl construction I am following a similar design here. The brace ends must fit precisely without forcing or 'springing' the ribs of the bowl

The plan - once the braces have been fitted precisely into the pockets - is to temporarily clamp the braces to the sound board with clamps set through the sound hole. The sound board will then be removed with the braces clamped in position and the brace locations precisely reference marked. The clamps will then be removed and the braces glued to the sound board where marked. If all goes well the brace ends should then fit exactly into their respective pockets when the sound board comes to be glued in place. We will see!
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