This site has something for you if you are either making a violin or you want to improve a low cost violin or viola.

By tuning the top & back plates you can get a good instrument that responds well to the bow and that can sound like a £1500 instrument.

Arching of the front and back

For arching the plates, the best guidance I’ve found is in Sacconi’s book on Stradivarius’ violins called “The Secrets of Stradivari”, where he gives the ideal ‘contours’ of front and back plates, and tells us just where to put the highest point of the plate.

I like the method that Juliet Barker teaches at CVM in Cambridge that can also be found in her book. Instead of using the long and cross ‘arching templates’ that so many books get you to cut out and use as a guide, while the inside of each plate is (perfectly) flat use a pencil gauge to create the arching contours of your choice. This ties up well with Sacconi’s ‘contours’ in his book mentioned above.

This summer I had cut elaborate cardboard contour guides like Dale Langsather for use with the pencil gauge at the CVM workshop, but the reality is that a tutor comes along a says “You don’t want to do it like that!”. So all the painstaking work was for nothing: it’s about a feel and look for that arching, and in retrospect, I think they are right - the contour guides are just guides.

There’s also guidance in any of the various books on violin making in the ‘Really Useful Links’ page.

The front and back should have different arches. The front or belly has a longer, flatter long arch and cross arching than the back. Bruce Ossman in his book on your first violin (see here) has them the same for simplicity, but there is no need to do so.

Here’s how Onnes Violins sets the arching on the back of a ’cello he’s making using various workshop tools, including power tools!. The same technique could be applied to a violin or viola. He also has an interesting page on thicknessing and tuning the plates of a ‘cello here using a laptop and Apple’s ‘Perfect Pitch’ program.

Darren Molnar has some interesting things to say about arching on his site, particularly about using Curtate Cycloids .

The Strad Magazine has a scanned copy of Quentin Playfair’s article on cycloids from The Strad, 1999: you can download: Part 1, and Part 2. I met Quentin again when he taught at Cambridge (CVM, UK), and here’s a picture of him (centre) in the workshop. A skilled craftsman who knows a lot, and can tell it with tact.   These cycloid shapes are much easier to create than to describe - especially in maths, as they use parametric equations. But it’s quite easy to create an arching profile using a spreadsheet, and then use the pencil gauge shown on the Tools page.

Thicknesses of the front and back

  The thickness of front and back plates for great Guarneri ‘del Gesu’ violins can be found here, reprinted from ‘The Strad’ Sept. 2005. And Erik Jansson also gives guidance on thicknesses in his articles “Acoustics for Violin Makers”, Chapter 5, Fig. 5.21, page 24.

 I have derived a Fig. 1 below to show where to thin a front plate (the belly) to reduce either Mode 2, Mode 5 or both frequencies. Click on it to see the Figure in more detail.

This is a revamp of Erik Jannsson’s work referenced above, which itself seems to be based on Carleen Hutchin’s work of 1982, published in the CAS Journal.

 [Front and back thicknessing: continued ]                         As an example using this data, I recently needed to reduce Mode 5 of a viola belly without reducing Mode 2, so I took areas marked the colour orange in Fig. 1 above from 3.0 mm to 2.4 & 2.5 mm. This took Mode 2 from 278 Hz to 263 Hz, but left Mode 2 unchanged at 112.8 Hz.

 I have also derived Fig. 2 below to shows where to thin a back plate to reduce either Mode 2, Mode 5 or both frequencies. Again, click on it to see the diagrams in detail..

   There is some agreement between the various reference books, and the other sources for back thicknesses as to where the thickest point on a violin back should be. Summarising these sources, and ignoring differences in plate shape :-

• Stradivarius put the thickest point ~46% down from the top of the back plate [source: Sacconi and Courtnall and Johnson.],
• Other sources (e.g. CVM, Juliet Barker and her team] and others) put the thickest point about halfway (50%) of the way down the back, and
• Guarneri del Gesu usually put it ~55% of the way down,

all distances measured from the bottom of the top block to the top of the bottom block. This ‘thickest point’ then acts as the centre point of the ovals or circles that guide the thicknessing of the central area. It is sometimes slightly offset towards the sound post.

   So choose your model, make your choice.

Raising Modes 2 & 5 in a thin back.

This thickness data is especially useful if you need to add a maple patch to the middle of the inside of a back that is too thin i.e. has too low a Mode 2 or 5. I’ve found that a wide patch of say 4 mm thick increases mostly Mode 2, and a long (lengthwise) patch of 4 mm thick increases mostly Mode 5. You will need to shape and then ‘chalk fit’ the maple patch before gluing, but I have used fluid Araldite (resin 2-part glue) on cheap factory fiddles, as it is much quicker - the resin glue acts as a filler, where animal hide glue cannot.

There’s also first-hand guidance on thicknessing in Sacconi’s book on Stradivarius called “The Secrets of Stradivari”, and in other books to be found on the ‘Really Useful Links’ page.

‘Fiddlehead’ has been working with the famous Jeff Loen on Strad plate thicknesses, and these can be found here for the Harrison Strad of 1693 for front and back.

Have a look too at David Langsather’s website page for a quick and practical approach. He uses an very useful ‘overlay sheet’ method to give guidance on thicknesses. He has the thickest point about 55% of the way down the back.

Osnes Violins in Alaska (!) shows how thickness graduation is done here on a ‘cello, and shows plate tuning, cutting the ff holes, and fitting the bass-bar. He uses a power router/cutter to remove the excess wood from inside the back of a cello.