Violin rib construction methods
The sides or “ribs” of the violin are most commonly constructed of six thin strips of wood, reinforced where they meet at the corners and ends by small blocks of wood. The problem during construction is how to hold those blocks and sides in place while they are being shaped and assembled. There have been several solutions to this problem, the most popular these days being the “inside mold” as used by the major classic Cremonese makers. Other methods include the “outside mold”, “building on the back” and “spanish guitar style”.
Each method has its own advantages and demerits depending on what the maker’s aim is, the outside mold for instance gives a high degree of control over outline and has been favored by copyists looking to reproduce the non-matching outlines of the back and top of an individual old instrument. It is also favored, by odd contrast, by makers seeking extreme symmetry and reproducibility, it is famously used by 19th century French production manufacturers and is partly responsible for the uniformity and relatively stiff look of some of those instruments.
One method that is rarely mentioned is a “skeleton mold”. I came to the idea a couple of years back when I wanted to make a Guadagnini model violin but was too impatient to go through the process of constructing a new inside mold. I decided to make a mold that had just enough structure to hold the blocks in place but carried no information about the outline of the finished instrument. My skeleton mold was born partly from laziness and partly from the enjoyment of trying new techniques and seeing what they will reveal.
What I found surprised me, a rib construction method that is simple to set up and which allows a broad range of control or improvisation depending on the maker’s personal inclination. I don’t think that this method is new, since adopting it several years ago I have heard passing reference to some older German makers using it (and I would be grateful for any further references to it’s use), but it is not mentioned in most reviews of construction techniques that I have seen. The skeleton mold has some significant advantages over other rib construction techniques which I list here and will demonstrate in contrast to the popular Cremonese style, inside mold.
Advantages of the skeleton mold
- Quick set up: one mold serves for an infinite variety of rib outlines.
- Adaptability: improvements to an outline can be made simply by producing new templates rather than by correcting imperfect molds. On-the-fly adjustments and improvisations can be made with easy reference to a baseline.
- Control: I was surprised to find how easy it is to bend ribs to fit a drawn line.
- Access to inside of rib/block and rib/lining joints. Joints can be checked and cleaned up during construction rather than having to correct any errors after glue has dried and the mold is removed.
- The inside line of the rib structure can be directly traced onto the top and back plates removing any guesswork about how far the internal hollowing can be taken.
- Light weight and easy handling: particularly significant on cello molds.
- Storage: store only drawings and templates for each new model of instrument.
- The work board provides a cheap, disposable surface for cutting and trimming on, it also allows the job to be easily and safely clamped to the bench. This is particularly handy when chopping in the C-bout lining mortices.
- Every construction technique leaves some tell tale signs (beloved of connoisseurs) on the finished instrument. If capturing every detail of a given instrument is your aim then adopting the identical construction technique might be a more fruitful path to follow.
Using the skeleton mold
[I’ve stopped using the wood screws, its easy enough to bend to the line. Jan 2015]
The linings can either be trimmed now or after the ribs are removed from the mold.
A skeleton mold for cello. I was nervous that the larger ribs would be uncontrollable but my worries proved to be unfounded. In this case I cut the shape of the C-bouts into the mold so this mold is not as universal as the violin and viola molds – you can easily vary the upper and lower but shapes but the C-bout is fixed. This mold was an absolute joy to use: light (only 1Kg compared to 3.2 Kg for my traditional mold) and with many convenient hand holds. When I recently made a double bass I balked at using a skeleton mold; the ribs were just too big for me though I would imagine that an experienced bass maker could do it fairly easily.
Making a copy of a smaller Guadagnini cello was an ideal application for the skeleton mold. I wasn’t sure how many of these I would be making, but by using a skeleton mold the setup investment was small and the turn around quick.
Copy of the Kochanski Del Gesu made for Robertsons and Sons Violins, constructed on a skeleton mold. In order to capture the feel of the looser outline on the original instrument I made a full body template of the rib line for the back incorporating some of its asymmetries.
The skeleton mold became the basis of my journey into the wild world of Freestyle Violinmaking