Making a cello and bass mould

A lightweight design for an adaptable method of working

Makers reveal their special techniques

I developed my mould for cellos and double basses in order to give me an accurate means to copy the incongruities of antique Italian instruments, while remaining in control of the process and preserving all the critical measurements. What follows is a surprisingly easy and concise method for bending, fitting and trimming the ribs and linings, using a lightweight and intuitive design.

1 Template layout

I lay out the mould for a template. In the example shown here, I’m using 19mm plywood for its stability and ease of use when followed with a router. I mark the location of the blocks, as well as where the cross-bracing will connect to the brackets that hold them in place. This will ensure that the blocks are all square to each other.

2 Making the cross-bracing

ALL PHOTOS TREVOR DAVIS

I make the cross-bracing by measuring the length and width of the block areas and subtracting the thickness of the brackets that will hold the blocks. The brackets are the depth of the rib minus the thickness of the garland quarter of the outline, and are the also the points at which it will be attached. I cut recesses to allow access for the linings to be mortised into the C-bout blocks, and then drill holes through which the corner-blocks will be mounted.

3 Routing the garland quarters from the template

As basses have differing outlines from top to back (and sometimes from treble to bass), I originally designed this technique to accommodate all those differences, but as this cello is to be symmetrical, here I am mounting the template to the four 19mm-thick quarter garlands through the mounting holes, sawing and then routing all at once to ensure congruence.

4 The completed mould

Next, I drill clearance holes and countersink them so that they may be screwed to the brackets on the cross-bracing, such that the ribs can be planed flush to the mould once installed. This saves time and effort in the eventual flattening process.

5 Installing a C-bout

Cam clamps help remove a ny slack in the outline and hold the rib snug in place as the blocks are firmly clamped.

6 The ribs are installed

The lightweight mould is easily manipulated and provides ample clamping options, which allow me to work quickly and accurately for stressful gluing operations such as the butt joint at the lower bout.

7 Bending and installing the linings

With the quarter garlands now removed, I steambend the linings wet, and leave them to dry in shape, 7 all clamped in position. Then I mark them, remove them and subsequently trim them to their proper length, snug to the blocks before gluing. Speed clamps make quick work of the job, supplemented by C-clamps for even, firm pressure resulting in seamless joints.

8 Trimming the linings

The linings are easily trimmed as every angle is accessible and the light weight of the overall rib structure means the mould is manipulated as one sees fit. After flattening, both the outside and inside of the rib and linings may be traced for accurate graduations out to the gluing surface and perfect alignment upon final assembly.