I decided to build another cello but with a few differences from the previous 4 which were all to the same pattern. For this one I decided to re-draw the plate outline based on the Cremona school 5 circles approach with a few tweaks to give me control on where to position the lower corners using the FreeCAD Part Design workbench. I also redrew the f-holes and positioned so them so the centre portions were slightly angled from vertical and using a system that allowed me to position them easily/accurately on the finished top plate.
Main dimensions are:
Body length: 752mm
Upper bout: 350mm
C-Bout: 237.5mm
Lower bout: 435mm
Rib depth at base: 119mm
Rib depth at heel: 115mm
String length: 690mm
F-stop: 400mm
Fingerboard length: 580mm
Overstand: 22mm
Outlines were exporting as dxf files to my CAM system so I could cut out templates on my CNC router. Using FreeCAD also enabled me to 3D print some accurately shaped cauls which were used for clamping up the bouts at the corners.
As the outline was new I also had to build a new form which I designed to be collapsible to make it easier to extract once the back plate had been glued in place.
The finished instrument came in very light at 2840g all up and is very responsive with a beautiful tone and very easy to play.
I have decided to call her “Ella”.
The build can be seen in the gallery below:
Did you find that matching mode 2 and mode 5 (front and back plates) in cello #4 made the sound better than the other cellos 1/2/3? Or and description of any differences?
No.3 mode 2 belly was a little low and the result was a sound not quite as strong as the others. Otherwise on the first 4 cellos I managed a pretty good matching of modes 2 and 5 and between front and back plates. No.2 had the lightest front plate and had a very strong voice. I’m changing a few things on my 5th cello (pattern and f-hole shape/placement) and the front plate was from a lovely piece of spruce which has turned out the lightest yet so it will be interesting to see how that turns out.
Thanks David for the explanation. Sorry for my typo, looking again at the mode frequencies, yes cellos 1/2/4 pretty much match for the front and back plates. I was drawn to the near exact match on cello 4. Indeed it will be interesting to hear how an even lighter front plate will sound please post details once complete!