Making Cello No.4

Design

I decided to have a go at another cello because I enjoy building them so much!  Of course I also wanted to improve on the cellos built so far by making a few judicious design changes and tweaking the build process based on experience with the earlier builds.

The key design changes were:

  • Sight changes to the archings (25mm belly and 23mm back)
  • Reduce f/b side thickness to 7.5mm from 8mm
  • Change break angles over the strings to improve playability (19.5 degrees ADG and 24 degrees DGC)
  • Changed f/b profile to match change in bridge profile
  • Increase over-stand by a few mm to 22mm
  • Attempt to increase Mode2 and Mode 5 plate frequencies to around 65Hz and 130Hz
  • Colouring the instrument a richer chestnut brown 

The resultant design drawings done using solvespace are below.

cello template da2 top

cello #4 back profile

cello #4 belly profile

fingerboard profile #4

cello #4 side view

cello #4 neck

I also decided to make use of my CNC router to build new 6mm MDF templates based on these drawings.

Build process

As usual, not everything went perfectly to plan but most of the desired changes seemed to work.  The one area I had real difficulty with this time was tuning the plates especially as i was trying to hit higher resonant frequencies this time around.  As I was trying to tune the top I was having real difficulty getting mode 2 and 5 and octave apart – the ring mode just didn’t want to drop.  Then I happened to wash the outside of the top to get rid of some surface bruising (from when the top was drilled out) and the following morning it suddenly started to behave properly!  My assumption is there must have been some latent stresses in the spruce and the wetting allowed them to settle out – a bit like annealing.  Anyway I ended up with Mode 2 and 5 exactly an octave apart and matching on back and top at 60Hz and 120Hz respectively.

The finished instrument is a beautiful chestnut colour and has wonderful a rich singing tone using a set of Larsen Magnacores.  I have christened her “Doris” and she weighs in at 3.01kg.

I am delighted with her – a definite keeper!

The finished instrument

The following gallery illustrates the build process.

2 thoughts on “Making Cello No.4”

  1. Fascinating! How did you like the new string angles (19.5 degrees ADG and 24 degrees DGC)? And what were your previous angles? Lower numbers or higher? I am a nut case who decided to make an electric cello even though I have never played a cello before. I reckon I can learn it when it’s done. So I should definitely make something that’s not too hard to play! I had curved the fingerboard to accomodate angles 15 degrees ADG and 20 degrees DGC, but I’m early in the process and can change that with a little extra work.

    1. I was using 20 and 20 before which can make the G a tricky to bow when up the fingerboard. On this cello I ended up with about 20 degrees and 23 degrees and it’s great to play.

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