Category Archives: Cello #2

Cello No.2 – Beryl – Completed

I finally completed my second effort at cello making and delivered the finished instrument to George (who christened her “Beryl”)  just in time to play the Stratford Symphony’s summer concert.

Here are a few recordings made at George’s Bank Cottage studio:

And a set of pictures of the finished instrument kindly taken by George .

A complete pictorial record of Beryl’s 6 month build process can also be found here.

Cello #2 Underway

Really exciting day – I just collected the wood from David Dyke down in Sussex to start on cello number 2.

Procuring the cello wood

A whole lot of wood!
A whole lot of wood!
Rough cut neck to let it settle
Rough cut neck to let it settle

Front and back plate preparation

And here are the belly and back book matched pairs getting glued up after spending hours getting a perfect joint – lovely flame on the maple back.

Back halves glued up
Back halves glued up

Managed to do the back without clamps but the spruce always seems to move a bit when heated up for gluing so I just needed a slight clamp pressure to get it tight.

Top all clamped up
Top all clamped up
Gluing the book matched top
Gluing the book matched top

 

The belly wood has a wonderful ring to it and great grain even and straight structure.

I also started to thin the maple ribs down to size on the drum sander but not to finished size so that I could scrape a finish on what will be the outside.

 

 

Top trued up
Top trued up
Back trued up
Back trued up

The cello ribs

Ribs getting down to size
Ribs getting down to size

Will have to scrape them next because I don’t want to see any sanding marks on the finished instrument.

And here are the blocks cut ready to to glue into the form. The end blocks are in spruce, corner blocks in willow as it is more forgiving to carve.

Blocks cut ready to glue into form
Blocks cut ready to glue into form
003
Blocks glued in and trued up
Blocks being carved
Blocks being carved
Gluing the ribs
Gluing the ribs
trimming the rib edges to match the form
trimming the rib edges to match the form
In the middle of fitting the linings
In the middle of fitting the linings
Linings fitted to the ribs on the top side - just need trimming down
Linings fitted to the ribs on the top side – just need trimming down
Gluing up using homemade peg clamps
Gluing up using home-made peg clamps

Note I have added some removable sections to the central form at top and bottom to make removal easier after gluing the linings.

Merlin inspecting the ribs just removed from the form
Merlin inspecting the ribs just removed from the form

 

Just need to carve the blocks to shape and chamfer the linings.

 

Carving the cello back plate

Top and back roughly cutout on bandsaw
Top and back roughly cutout on bandsaw
Getting ready to carve the arch
Getting ready to carve the arch

I built a simple jig to use with my small router so that I could cut the edges to the right thickness (5.5mm all around, 5mm in the C-bouts and 6mm at corners) with the top firmly clamped down onto the workbench.

Simple router attachment for thicknessing the edges of the back and top
Simple router attachment for thicknessing the edges of the back and top

This is an enormous improvement to the approach used on my first cello and as well giving a really consistent edge thickness, it gave me something to aim at when rough chiselling the back profile.

Back rough carved
Back rough carved

 

 

 

 

 

 

Edges cleaned up on the drum sander and slots for purfling marked up.

Outside of back profile finished ready to add purfling
Outside of back profile finished ready to cut purfling slots
Getting ready to glue up the purfling laminate
Getting ready to glue up the purfling laminate
Purfling in, channels cut and profile rough scraped
Purfling in, channels cut and profile rough scraped
Thickness contours marked
Thickness contours marked

I used my new pillar drill to good purpose to drill out depth guide holes across the whole back (the old drill didn’t have a wide enough throat to reach the centre of the instrument).

Thickness guide holes drilled
Thickness guide holes drilled

 

Now to start the long process of thumb planing the inside to give the correct thickness profile and plate tuning to get the right mode shapes and frequencies.

Back hollowed out roughly ready for plate tuning
Back hollowed out roughly ready for plate tuning

Carving the cello front plate

Now to start on the spruce top. I got to this point in just a day.

Working on the profile of the top. Spruce is so much quicker to work than the maple!
Working on the profile of the top.
Spruce is so much quicker to work than the maple!

Came across a resin inclusion when carving out the top.  On scouring the internet this is apparently quite common in good tops (1 in 10 maybe) and no problem – just have to to shape a plug to fit the cleaned out hole.

Resin inclusion cleaned out ready for plug
Resin inclusion cleaned out ready for plug
Plug shaped and ready to glue in
Plug shaped and ready to glue in
Plug glued in
Plug glued in

Then a final bout of scraping to get a perfect profile before marking out the purfling channels and deepening with a scalpel.

Top profile finished and purfling channel marked
Top profile finished and purfling channel marked
Top purfled
Top purfled

 

Next step is to cut the channel and fair everything in before hogging out the back side of the plate.

Outside finished
Outside finished
Inside roughly carved ready for plate tuning
Inside roughly carved ready for plate tuning

Cello plate tuning

Top plate mode 5
Top plate mode 5

I thinned the plate until I got good clean mode 2 and 5 shapes but before going further on the top I have to cut the f-holes and fit the bass bar.

f holes carved out - just need to undercut them and do the V's
f holes carved out – just need to undercut them and do the V’s
f-holes cut and bass bar glued in
f-holes cut and bass bar glued in

 

 

 

 

Tuning the bass bar

Started with a bass bar 11mm wide and initial depths set according to the following table:

Proportion of length 0 1/8 1/4 3/8 1/2
Depth (mm) 9 15 21 27 29

Then progressively reduced the depth to get the changes of mode shapes shown in the gallery below.

Reducing the ends helped to close the ring-mode shape but also reduced the x-mode frequency which I was generally trying to maintain. Reducing the centre of the bar predominately reduces the ring-mode frequency but I also had to thin the edges of the top and the centre of the upper bout between corners to try and get the ring-mode down to an octave above the x-mode.

A final tap tuning allowed to identify and remove any thick or high stiffness spots both on the top and the bass bar.

The final bass bar ended up only 18 mm high in the centre with X-mode of 58.2 Hz and ring-mode of 121.5 Hz.  I then thinned the back to match those frequencies – much easier – and got 59.2 Hz and 120 Hz.

Making the box

Started by gluing the sides onto the back after first re-enforcing the sides with strips of linen.

Back glued on
Back glued on
And the all important label! You can also see the rib re-enforcement strips of linen
And the all important label!
You can also see the rib re-enforcement strips of linen
Gluing on the top
Gluing on the top
Now what about the neck!
Now what about that neck!

The Cello Neck

The neck blank I cut back in March had settled a bit so I squared it up with the plane and then marked up and cut it out on the band-saw.

Neck blank roughly cut to size on the bandsaw
Neck blank roughly cut to size on the band-saw
Scroll finished
Scroll nearly finished
Scroll detail underneath
Scroll detail underneath

Next step is fitting the neck to the body.

I did a drawing of the fingerboard profile to give an even break over the strings at the bridge of 21 degrees and then an action over the end of the fingerboard ranging from 4 mm at the A-string to 6.5 mm at the C-string. This showed I needed a 2.4 degree slope on the neck towards the bass side.  I have heard of 1.8 degrees being used so ended up going for 2 which still looks quite a slant!

Marked up the heel with this 2 degree slant narrowing the heel down to 27 mm at the bottom with enough material to give me a 22 mm overstand on the A-string side.

Before fitting the neck I will cut and shape the fingerboard and stick it in place temporarily to aid in getting the set of the neck right.

Setting the neck angle before shaping the neck and heel
Setting the neck angle before shaping the neck and heel
Neck shaped and ready for gluing to the body
Neck shaped and ready for gluing to the body
Cello completed in the white - now for a bit of a tan in the light box
Cello completed in the white – now for a bit of a tan in the light box

 

 

 

 

 

 

Finishing the cello

I started by making up a varnish ground coat from a recipe I found on the internet in an article by Harris, Sheldon and Johnston.

This consisted of cooking up Boiled linseed oil and rosin at 180C for a few hours in the ratio of 1 part linseed oil to 1.5 parts rosin by weight until the mixture achieved a sticky toffee like consistency when cooled.  I used my trusty mini fat fryer to do this safely in a double boiler arrangement using cooking oil instead of water.  I then added turpentine so that the resultant cooled varnish had a golden syrup like consistency.

Then I ground in 10g of Kaolin (china clay) to 30ml varnish with 7ml of rabbit skin glue and added water until I had a nice creamy consistency that could easily be applied with the fingers and then ragged off to give an even finish.

Ground coat applied
Ground coat applied

Then into the UV cabinet for a day.

In the UV cabinet
In the UV cabinet

I added a few coats of shellac to make sure it was all sealed properly, cut back with  600 grade wet and dry and then a final wiped on coat of shellac before applying the first colour coat and drying in the UV cabinet.

After 1st colour coat
After 1st colour coat
After 1st colour coat
After 1st colour coat

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Back after smearing in oil pigments by hand
Back after smearing in oil pigments by hand

Next I mixed up some oil pigments – 1 squirt of burnt umber, 1 squirt of burnt sienna and, a bit less than half a squirt of alizarin crimson and a little boiled linseed oil and then smeared on by hand until the colour was the right depth and fairly even and then back into the UV cabinet.

Wasn’t entirely happy with that – a bit streaky on close up – so rubbed most of it off with a turps soaked cloth and put it back on with several much thinner layers so as to leave no marks.

Result has a nice warm glow and enough variation to look interesting!

Nearly there on the colouring - think I might add a bit of blue next!
Nearly there on the colouring – think I might add a bit of blue next!

It will darken up a bit more after another 3 or so colour coats.

The back after next colour coat
The back after next colour coat

 

Next colour coat applied
Next colour coat applied
After 2nd colour coat - curing the old fashioned way under the sun!
After 2nd colour coat – curing the old fashioned way under the sun!

 

Back after 2nd colour coat - curing in the sun
Back after 2nd colour coat – curing in the sun

One more colour coat and then a couple of clear coats before cutting back and polishing.

Curing outside in the sun on one of the few sunny weekend days this year! – Just like the old Cremona makers used to do.

It all looks a bit shiny at the moment but that will go once the finish it has been cut back – aim to get a nice satin sheen.

Clear coats next.

Applied 2 top coats and then cut the varnishing back with micromesh down to 4000 grit and then finished with rotten stone and linseed oil.  The cello has a wonderfully rich chestnut sheen to it.

The finished back
The finished back

Glued the neck on after removing the keeper, and then fitted the pegs, saddle and endpin.

Only things left now are oiling the neck, and fitting the nut and bridge
Only things left now are oiling the neck, and fitting the nut and bridge

Just finished the instrument and delivered to a very happy customer (George) who christened it “Beryl” in time for our weekend concert with the Stratford Symphony Orchestra!

"Anna" right (with me - David) and "Beryl" left (with George) at rehearsals
“Anna” right (with me – David) and “Beryl” left (with George) at rehearsals