Davide Sora

I like to cut the F-holes when the plate is very close to the final thickness. I leave the C-side and lower wing thicker to allow for later fluting of that area. To trace the F-holes, I use the Stradivari system, which begins with placing the eyes inside the plate, using the rib-tracing marks as a reference. First, draw the two horizontal lines, then position the center for the lower eye and, based on this, the center for the upper eye. This tracing and cutting system can lead to some asymmetry in the position of the eyes on the outside of the plate. I double-check the position of the upper eyes on the outside before drilling, just to be sure. Once the eye holes are drilled, I use a plastic template (acetate, 0.25 mm thick) to trace the stems on the outside of the plate. Stradivari used paper templates to trace the stems, which are still preserved today in the Museo del Violino in Cremona. Once I've traced the F-hole stems on the outside of the soundboard, I use a fretsaw to cut them. I follow a precise cutting sequence to minimize board flexing caused by cutting.

I have some doubts that this is the M5. With the top plate without the Fs and those thicknesses, it would definitely be too low. Maybe it's the M2? Are you sure about your method of detecting the mode frequency? On my last viola of a similar size to yours (415 mm), the M5 before cutting the f-holes was about 280 Hz (C#), and the thicknesses were already lower than yours. The quality of the wood and the shape of the arching can make a big difference, but it seems like an excessive difference to me. In any case, if I were you, I would still cut the f-holes and see what happens before taking any drastic decision. PS Taking frequencies without considering weight doesn't make much sense (other than chasing a golden standard, which I suggest you don't do), because mass greatly influences frequency.

I'd say no, too. Tap tones tell you something about the stiffness of your plate and the stiffness-to-mass ratio. But I wouldn't throw a board in the fireplace because tap tones don't hit a supposed "gold standard".

In addition to specifying the basic information mentioned in the previous post, what tap tone are you referring to? M5, M2, M1? Knowing the frequency would help. The size of the soundboard (your viola's size) and its weight would also help. Violas vary greatly, so narrowing down the field is essential.

Another thing I write on the maple blocks is a mark (letters or dots) that I also repeat on the corresponding blocks for the scrolls and for the ribs. I almost always buy sets, and this saves me time pairing the scroll and ribs through a jumble of jumbled blocks. On the shelves, I keep both the scroll and the ribs side by side with each back, or at least alongside (or on top) the same set of backs of the same wood, or from the same year of purchase.

Yes, setting it to a fine cut works fine, but even if it is a little more aggressive, the softness of the spruce allows you to adjust the depth of the cut effectively simply by applying more or less pressure. I think I haven't adjusted the blade protrusion on my toothed fingerplane in years, nor the sharpening.

After using the standard blade fingerplane, I move on to a smaller fingerplane with a toothed blade. Until some years ago, I didn't use it for spruce, which can also be cut well with a standard-blade plane, but now I find it useful and practical. Things are always evolving. The marks left by this type of blade are clearly visible and allow for more uniform and controlled wood removal. Furthermore, although the surface is rougher, it will also be less wavy and irregular than with the standard blade, making subsequent work with the scraper easier. To remove the marks of the fingerplane and to finish the thicknesses, I use a scraper, which allows for progressive, controlled wood removal. Definitely one of my favorite tools.

With my two 120cm-long tubes, each rated at 40W (I admit I don't know the actual UV power), there's certainly no risk of burning anything. In the past, I've even done continuous exposures for three or four days. After a certain time, the temperature and humidity stabilize and stay there, provided there's good air circulation. If I placed the violin at a 45° angle to the tubes, there wouldn't be any need for rotation, but I prefer to rotate the violin to be safe. With four tubes, there's theoretically no need for rotation. I have two more 60W tubes that I'll install sooner or later, bringing the total power to four tubes with a total of 200W. This will certainly speed up tanning or varnish drying times, but I haven't done it yet, so I can't tell you how the temperature and humidity inside have changed compared to now. In any case, in addition to power, another aspect that can significantly change efficiency (or problems) is the distance from the light sources. The intensity drop depends on the inverse square law. To put it simply, if you double the distance, the intensity is reduced to 1/4 and not 1/2 of that at the closest distance. This law would apply to a point light source; for diffused light, it will not be exactly like this, but it gives you an idea. This is my not-so-technological UV box:

For me, writing the year of purchase and the supplier on each piece is essential. I write it with red marker on the waxed ends, so as not to contaminate the wood. I organize the pieces on the shelves by year and purchase, with the ends facing outward, so I can keep all the dates in sight. When I measure the density, sound speed, or other numbers, I write it in pencil somewhere on the wood, usually on the narrow side. I tried keeping a log, but it's much more cumbersome, and it's difficult to put the wood back in the right order when you take it all out to check it or to choose pieces. P.S. My metal shelves are enclosed in a lightweight cabinet made of mosquito nets, just to be on the safe side regarding woodworms.

When I've finished the back, I move on to the top plate thicknesses. With the gouge roughing, I arrive at a thickness of about 3.5 mm in the upper and lower bouts, 4 mm in the center, and 4.5 mm in the Cs. I start carving with a more curved gouge (#6 x 35mm) to remove most of the wood and finish with a flatter gouge (#3 x 35mm) to get a more evenly blended surface. To remove gouge marks, I use a 48 mm long, 21.5 mm wide curved-sole fingerplane, with an 18mm wide blade sharpened with a curved profile. When I work on the thicknesses, I evaluate a series of parameters. Frequency is one of them, but it is not possible to rely on just one because it would easily be misleading. The mass (weight) of the plate and its flexibility in longitudinal and transverse bending, as well as in torsional bending, are fundamental parts of the overall picture. The correct balance of all these aspects will determine the final thickness.

Place it vertically, at the height of the violin. Direct light is much more intense and effective than reflected light. 20W might be a bit low; mine has two 40W tubes (so 80W total) and isn't the most powerful. The most popular UV lamp in Cremona these days is this one, which has 300W of power: https://www.cremonatools.com/uv-365nm-300w-lamp-with-dimmer-547222.html A little expensive, but if you manage to order it directly from China, you can maybe pay half the price or so.

I agree with David's observation. Do the two maples (the old one and the new one) have the same material properties? Have you measured them? Without removing this unknown, you risk being easily misled.

I use a "special" tool adjusted to various measures to draw lines of equal thickness. This helps me visualize the distribution and decide on any adjustments. To adjust the thickness tracer, I use a graduated wedge with measurements marked every 0.5 mm. I check that the set measurement is correct by measuring the trace left on the wood, changing the setting if necessary. For measurements smaller than the edge thickness, I use the tool's elasticity to widen it and allow it to enter, bypassing the edge. Once the thicknesses are complete, I record these distribution lines in my notebook for reference. For every instrument I make, I record all the measurements and construction details, varnishing and set-up included. I prefer paper because it guarantees unlimited and reliable durability, something that digital files never offer. I started collecting this data in 1984, the year I became a professional violin-maker. I have accumulated a lot of data, which is very useful as a basis for comparison with the new instruments I make, and even more useful when a violin comes back to the workshop for maintenance, to recall its construction features.

Back thickness. After an initial general roughing and having carved the five transverse channels with a more curved gouge (n°6), I blend all the rest with the flat gouge (n°3 x 35 mm), arriving at a provisional thickness of approximately 5.5 mm in the centre, 4.2/4.5 mm in the Cs, and 3.2/3.5 mm in the upper and lower bouts. I check the weight and frequencies, writing them down in a notebook for reference. To remove gouge marks and make the surface more uniform, I use a toothed blade fingerplane. I check the weight and frequencies, writing them down in a notebook for reference. To remove the toothed blade fingerplane marks and make the surface smooth, I use a scraper 0,5 mm thick sharpened at 90° (double cutting edge).

Your target weight for the back is too high for my taste, but well, to each his own. With a density of 0.55, I'd expect a final weight of around 100 g or less, and I'd be happy to go below 100 g if the frequency (stiffness-to-mass ratio) remained in the 350 and 370 Hz range. An experiment distributed on a sample of 8 violins seems very interesting and reliable, keep us informed of the results.