Viola build

So I have just started with my new viola build based on a late Guadagnini from about 1830.  This is a small instrument with a body length of only 390mm (15.4″) but it is remarkably resonant and a joy to play.

Design

I started by measuring up the Guadagnini in great detail and then transferred those measurements to a set of drawings done using the solvespace parametric drawing package.

The resultant drawings are here as pdfs:

guad top mold

viola guad side profile

viola guad neck

viola guad ff holes

I procured some nice looking spruce and maple from Stefan Novak in Bristol.

Split spruce and nicely figured maple for the viola

Making the templates

Next I embarked on making the templates by transferring the drawings onto polystyrene sheet and then cutting out on the bandsaw.

The arching and neck templates

And built the body form from 10mm plywood.

The polystyrene body template and form made from 10mm ply

I used the neck template to roughly cut out the neck blank to give it a chance to move while I built the rest of the instrument.

Neck blank roughly cut out

I also did the rubbed joints on the back and belly after sawing the blanks on the bandsaw to give me bookmatched sets.

Bookmatched sets after doing the rubbed joint

which I then planed flat.

Back planed flat
Belly planed flat

and thicknessed on the drum sander about 1mm more than the desired arching.

The ribs

I carefully made block blanks by splitting spruce for the end blocks and willow for the corner blocks, cut to the correct height and glued into the form.

Then I shaped them using gouges and finished with japanese files.

Blocks shaped ready for ribs

Then I carefully prepared the ribs using the drum sander and scrapers to get them to 1.1mm thickness, cut them a few mm oversize on the bandsaw and then bent them on the bending iron before gluing onto the blocks with pre-made cauls.

After roughly levelling the edges with a plane I made them absolutely flat and true  by rubbing the rib assembly against a sheet of sandpaper on a flat surface. Then I cut the linings from some willow at 2.1mm thick and sightly oversize at 10mm deep and fitted them to the ribs.

Linings added

Belly and back

First I marked the outline of the back and belly using the ribs and a washer to give the 2.8mm overhang. These were then cut out on the bandsaw before using a router with a homemade attachment to cut a shelf around the edges where the purfling would go. Then I used gouges, thumb planes and finally scrapers to set the arching shape against the already made templates.

Rough shaping of the arching on the back
Back arching (outside) complete
Front arching (outside) complete

The next task is to glue up the box temporarily and file the edge overhang. I decided to use pins this time to make the assembly and re-assembly easier so I selected some small panel pins about 1.4mm dia and after clamping top and back together on the mold when all trued up,  I drilled small 1.4mm holes on the pillar drill about 6mm in from the edge. The plan is to then drill out the holes on the back and front to 2mm after final assembly and fill with small wooden plugs. With a bit of luck these will be hidden by the purfling on the back and covered by the neck joint and saddle on the front.  I snipped the heads off the panel pins before pushing into the holes on the top and bottom blocks and then tacked it all together with weak animal glue – worked really well.

Box glued up temporarily ready for filing the edge overhang

I cut a small offcut to 2.8mm thick and a bit shorter than the depth of the ribs and fixed to a file with some masking tape. This is a great way to get the edge overhang constant but I used a knife on the corners to get them looking even.

Edges filed to 2.8mm and corners rough shaped

Next I marked the purfling channels. I used a new toy – a marking gauge by Veritas that uses a circular cutter – very effective at resisting grain following but can only use on the outside curves. I think I may make an adapter with some brass tube so that I can use on inside curves too.

New marking gauge
With simple attachment for managing inside curves

Then I used a scalpel to deepen the marks and chipped out with a 1mm chisel.

Purfling grooves cut on the top
Purfling channels cut on the back

Finally I bent and fitted some purfling I had left over from the last violin.

Purfling glued in on the belly
Purfling glued in on back

The next job is to cut the purfling back and then cut the channel with gouges and fair into the body with scrapers.

Purfling channels cut and faired in on belly
Purfling channels cut and faired in on back

Next I separated the plates from the body ready for thicknessing the plates.

I started with the back, using the pillar drill to give me holes at roughly the right thickness and then used gouges and thumb planes to bring in the correct profile checking the mode shapes and frequencies regularly.

Back marked for initial thicknessing
Back drilled for initial thicknessing

I am aiming at 125Hz for mode 2 (x mode) and 250Hx for mode 5 (ring mode). I left them a bit higher on the back at this stage until I have finished the front.

Tuning x-mode on the back
Tuning ring mode on the back

Then I repeated the process on the front finishing up with scrapers. Much easier on the top with the soft spruce.

Top marked for initial thicknessing
X-mode on the front tuned to 125Hz
Ring mode on front tuned to 250Hz

The top plate is nice and light too at only 74 g so hopefully it will be responsive.

Next job is to cut the ff holes. I marked the ff-hole outline by pricking through a scale drawing with a pin and carefully drilled the holes undersize before opening out to designed dimensions with a reamer.  Then I used a fine toothed coping saw to rough cut the outlines before opening out with a scalpel and cutting the nicks.

ff-holes roughly cut
ff-holes after carving out with a scalpel

Then I marked the position of the bass bar and cut and drum-sanded the piece I had initially sawn from the top blank to make the bass bar 6mm wide. This was then chalk fitted to the top, glued in and roughly planed to profile before tuning.

Gluing in the bass bar

I discovered that the x-mode had increased from 125 to 127 Hz but the ring mode had gone from 250 to 280 Hz so I was going to have to be careful to maintain the x-mode frequency.

After a lot of patient adjustment on both bass bar and top plate, I managed to get the the two modes back to the target 125 Hz and 250 Hz.

x-mode on the top @125Hz after tuning the bass bar
Ring mode on the top @250Hz after tuning bass bar

The bass bar ended up being quite low at about 10 mm in the middle and 4 mm at the ends.

Next I tuned the back to match which weighed in at 130 g.  I am extremely pleased with how well I have got the two plates to match with the x-mode and ring modes also being perfect octaves apart.

X-mode on the back @125Hz
Ring mode on the back @250Hz

Then I took the rib assembly and roughly carved the exposed blocks on the back to shape before gluing up using the locating pins in the end blocks.

Gluing on the back

Once the glue was dry I removed the mold ready to fit the linings for the top.  AFter fitting the linings I carved down the blocks, generally cleaned up and fitted the label ready for gluing on the top.

Cleaned up inside ready for gluing on the top

I used the pins again to locate the top when gluing  which I then removed and plugged the holes with small wooden dowels I made up from matching wood.

Assembling the box

Finally I rounded the outside edges with files and then 600 grade emery paper.

The next job is to make the neck.

Finished box ready for fitting the neck

The neck

I started by truing up the neck blank that I had roughly cut out out at the start of the build as it had moved a bit (as expected).

After truing it up and then filing to match the template outline, I drilled the peg holes with a 6mm drill at a slight angle to help the string tension hold them in place.  Then I marked the scroll outline before sawing the scroll a segment at a time.

Shaped neck blank marked up before cutting scroll
Sawing the scroll

After a lot of sawing, gouging, filing and sanding the scroll started looking about right.

Scroll well on the way

I then used gouges and sandpaper to cut the flutings before cutting the pegbox by sawing down the sides and then chiselling out.

Pegbox chiselled out after carving the flutings

Finally I cut the neck root at a slight angle to give me 1mm higher overstand on the C string side before starting the tricky process of cutting and fitting the neck joint. Before I could do that I needed to  cut the fingerboard to size and carefully shape the profile longitudinally to give the correct relief and transversely to get the correct action and make it easy to play.  Then I tacked the fingerboard to the neck with a few spots of weak glue ready for cutting the neck joint.

Fingerboard ready for yacking onto neck

Tacking the fingerboard onto the neck

Fitting the neck joint took the best part of a day ensuring I maintained a whole set of key dimensions:

  • Nut to top plate distance
  • Fingerboard overstand
  • Fingerboard projected height at the bridge
  • Fingerboard central over top plate

while ensuring a perfectly fitted joint.  I got there in the end and it held together perfectly dry.

Dry fitting the neck joint

Gluing up was easy and didn’t even need clamps.

Next I finished shaping the neck and then started the final cleanup before wetting , cutting back and putting into the UV cabinet to give it a bit of a suntan!

Neck shaped – starting final cleanup

Here is the finished instrument in the white after taking the temporarily fixed fingerboard off.  I will fit a keeper before it goes in the UV cabinet.

Finished viola in the white
Finished viola in the white (fingerboard removed for varnishing)

 

 

 

 

 

 

 

 

Finishing

After 2 weeks in the UV cabinet I made up some Vernice bianca from water, egg albumin, rock, candy, honey and gum arabic.  I applied 2 coats with a brush,  rubbing down with 600 grade after each coat and then wiped on some shellac to give a moisture proof ground.

After 2 coats of vernice bianca and a shellac ground
Back after 2 coats of vernice bianca and a shellac ground

It is still very light and next step is to apply some artists oil paints mixed with a little linseed oil to get the colour as close to the wood as possible.

After rubbing in some artists colours

The artists colours make a huge difference. Next was the first colour coat of oil varnish from the range produced by Joha and really starts to bring the wood to life (I have used red brown here mixed with brown).  Only another 5 coats to go!

After 1st coat of coloured varnish
After 5th colour coat
After 5th colour coat

It is all looking rather shiny now and still a bit red. I cut back with 600 grade and applied 2 more brown coats and then 2 coats of clear varnish (8 coats total). 

Viola front after final varnish coat
Viola back after final varnish coat

I will let this harden for a week in the UV cabinet before final cutting back and polishing to a more satin finish. In the meantime I will fit the pegs and saddle.

After cutting back I was not happy with the colour so applied a few more coats of red-brown mixed with brown and then a clear coat. Should be much quicker to cut this back as it has already been flattened.

After final final coat
After final final coat

I cut back starting with 600 grade and working through to 3800 and then rubbed in linseed oil with a bit of rotten stone before polishing. Then I fitted the saddle, fingerboard and nut and then finished the neck with linseed oil mixed with some burnt umber artists paint. I rubbed this in with wire wool and then burnished to a shine..

Setup

Varnish is still a bit soft so might as well make use of this wonderful weather and put it out in the sun for a few days before fitting the bridge and stringing up.

Getting a final tan in the garden before stringing up
Getting a final tan in the garden before stringing up

Bridge fitting took  a good half day and then strung it up for the first time.

Finished viola body
Finished viola back
Finished viola front
Finished viola peg box
Finished viola side
Finished viola side

ASL was spot on and sounds rich and responsive when I play it like a cello!  I will give it a few days to settle down before making any adjustments and then delivering to the client next week who has decided to call her “Carice” after Elgar’s daughter.  She weighs in at just 575g including the Kreddle chin rest which compares very well with the original Guadagnini at 565g.

Tweaking

Client is delighted but I need to reduce the fingerboard cant a little and fit a new bridge. Took the opportunity to get Helmholtz frequency A0 and 1st body mode frequency B0 matched at about 234Hz by increasing the scoop under f/b and undercutting the ff holes.

Full list of measured resonances:

Mode Comment Frequency
A0 Helmholtz or air mode 233Hz
B0 1st body mode 234Hz
B1+ Body resonance 499Hz
B1- Body resonance 360Hz
A1 1/2 wavelength body cavity 404Hz

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