Violin Forum/Message Board

[John Cadd]

The question comes down to how curtates work and why they make a better sound. Do any copiers get similar results ? That`s a harder question to answer . Vuillaume managed it very well .

[Michael Darnton]

As a general rule Vuillaume missed the target most of the time. When he was true to the original design he did very well but he always thought he was better than Stradivari, which was a mistake. I've seen only one or two Vuillaumes that were really accurate Strad copies and in those he also copied the arching.

In my opinion most modern makers aren't really fully capable of copying Stradivari accurately enough. It's very difficult to completely wash out influences of our own times, and some of our working methods also tend to erase things we should have left. There have been a couple of makers who have done well, but very few, and not the ones you would immediately name.

Of course arching is not the only thing that makes a violin sound good but it's one of the essential components of that.
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[John Cadd]

Linking one design feature to another can be good or bad .It`s also difficult not to link as so many things are inter related .
So at the risk of "too much thinking " here is my latest mad idea .
Some parts of a violin belly must be responsible for supporting the string tension. But maybe Strad decided to allow the recurve areas free reign to vibrate without any physical restrictions. Linking up another Edgar Russ comment about Too Thin plates giving Loud violins which were always loud and never quiet . That makes me question what parts of a violin belly make the most sound. Do some areas (eg the thinnest parts near the recurve areas ) make more sound than thicker ones. Another link now . If a recurve is steadily tapered down to the edge it might behave differently when the tapering gets thicker again before it reaches the edge . That thickening might give the "sea wave approaching the shallow beach effect" . Lots of energy would be used to move the sides up and down instead of keeping the belly vibrating .Waves could be kept flowing along the recurve instead of diverted sideways . A tricky bit of thicknessing needed to get that right .More than just an after thought to make it look right . That is linking to Heron Allen there .More than he thought about it as appearance .

[John Cadd]

To avoid computer programs there is a nicer more direct way to get the curves.
The physical act of rolling anything seems tricky so reduce that down to a set of circular discs fixed at the centres where they pivot . Each disc will be marked with degree lines through the centre. At the circumference you will have marks to indicate degrees of rotation. Draw another circle where the chosen point is placed . That also shows horizontal movement for the chosen point on the radius .The chosen point will change height as the disc rotates and this will give a series of points to record.
I nearly lost my way here . The first point of a curve is when the radius line carrying the chosen point is straight down vertically. The rotation begins and we record the horizontal and vertical positions at each angle of rotation . ( This is where I need to clarify the horizontal positions in my explanation ) Measure the vertical distance from the horizontal line ( through the chosen point at the start) .
Once the numbers are recorded a relief map can be drawn . That will give you the kind of relief map seen in the Sacconi book .
I made a simple drilling machine for this type of map with a set of drills for each height. There is no adjustment possible in the machine. The length of each drill is the only variable .Just double check and follow the relief map lines .
That puts the sequence in writing in case you hate computers . Instead of templates I make a set of relief map shapes .
There is still something not clear here .How far horizontally does the point move as the angle changes ? It`s sines and cosines time .

[John Cadd]

So now I have one curve that hopefully fits the centre arch. But how do I get a very shallow top with a wide shape ? Or can I squeeze it down mathematically?

[John Cadd]

Now I have realised the same trick I used for designing with a thin chain will work with Curtate cycloids. The wider , shallower curves need more precise figures to look right and a hanging chain will not allow that . So for a wide curve the ends are fixed and the depth is increased by 10 or 20 times . The depth figures to suit the relief map plan are recorded and divided by 10 or 20 to give the true depth .
The objections to using a thin chain for parabolas will be overcome by multiplication and division . To smooth out transitions between the points I also used one of those curve guides (Plastic with 2 steel strips inside ).
That makes choosing convenient depths for the relief map easier . Any unevenness in the relief curves will show up clearly when they are all drawn out . Making templates does not have that advantage .You find out (too late ) when you are cutting the surface .
Choosing the widths of each curve comes from drawing a line inside the full outline . Less clearance at the centre and more at the wider bouts.
The lengthways top curve using circle curves , joined up , has to be the starting point. That`s why I mentioned it last .

[John Cadd]

What I call squeezing the curve is what you see on an oscilloscope screen when the X axis or Y axis is altered . The Parabola design I followed was using a calculator (pre internet). That idea came from an article in the Strad . The thin chain method was my own idea and was infinitely quicker and easier . Curtates are not quite so helpful . But similar methods apply .

[Michael Darnton]

It appears that by trying to make the job easier you are making it more complex and harder!
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[John Cadd]

A classic "forum killer" reply . It does not matter . It happened a long time ago .

[Michael Darnton]

I really do not see the advantage of making a basic incredibly simple process more complex and imprecise. If that is a killer comment, I plead proudly guilty.
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[John Cadd]

What was the complication that disturbed you ? Was it using Sacconi style relief maps ? There is one long running question about spike holes in some violin plates .The set of curves showing depths for a relief map need one fixed point to keep them oriented together . The flat surface formed by the two wedges when joined will have the overall outline drawn on it . That is when the first largest outline is positioned and that point needs to be transferred to the opposite side . It can be marked with a pencil or with a spike . But it must be there for all the outlines to fit together from that point. Each outline has the fixed point marked on it.
Anyway the topic title does not restrict us to cross templates.

[Michael Darnton]

Think of some topic that you are skilled at. . . I don't know what you do, so I can't suggest a specific. You get into a discussion with someone and he simplifies it to the point that he's sort of correct, but his summary is something that wouldn't be a bit useful for the task. Like if I told you to get your vault open by turning it to one number, then another, then another, then to the last and open. That's correct, but it doesn't get you a bit closer to an open vault.

That's what Sacconi's contour lines are like. Exactly where does the arch change from convex to concave, for instance. That's the first questions and he doesn't give a hint. There's a lot more to it than that, as well, that the method doesn't describe. How and where is the bottom of the scoop placed? Not a hint. What's between the contour lines? No idea. The more experience you have with violins, them more you appreciate the necessity of knowing theses small details, and understand that contour lines don't go nearly far enough to describing the territory. https://conceptually.org/concepts/the-map-is-not-the-territory

The method of taking a disc and punching a hole in it gives all the necessary information for each spot on the violin. You only need to make one set, use it once, and you have templates for you and future generations. There's no need to use methods that don't give all the information (Sacconi, chain) and there's no need for computers if you don't want to use one.

More importantly, the method is as precise as the drafting of the rest of the instrument--it makes the arch similar in concept to the rest, rather than just taking one last piece of the puzzle, and saying "what the heck---here I'll just guess what to do." In the mindset of the whole instrument, it's consistent.
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[John Cadd]

Thankyou so much for the (for me ) revelation . I had no idea that violins were produced with just those templates . Like --the main line method . I always assumed there was more .
I was never tempted to use Sacconi`s map as it was not referred to one particular instrument . So thanks for writing in another forum that the maps were a kind of compilation .
Not to undermine any good theories but making the belly edges approaching the sides so flat (horizontal ) must save a tiny amount of weight compared to a steeper drop towards the glued edge .
Looking at some pretty awful e bay violins on sale yesterday , there must be a way to discuss topical violin ebay examples to criticise some awful arching examples . It would make a good topic . Probably the makers are long gone especially with no labels or names to blame .
My daft reaction to your message earlier made me feel like a cricketer facing an Indian spin bowler ."I don`t know how to play this googly ".
My very first effort at violins was to replace a belly with woodworm . That was the Heron Allen Strad page. It had plenty of recurve and in Parana Pine still sounded good according to players in my amateur orchestra . I forgot to cut the notches in the soundholes . Parana Pine straight from the woodyard and not seasoned .Tut tut . I was about 16 then .

[John Cadd]

So What would Strad do ? How would he approach the problem?
Also mention of computers on this topic is well offside . Start from what Strad could do ( hundreds of years ago ).
Give him one curve across the violin that looks good .I don`t know the Italian for Curtate Cycloids , But Strad knew about proportions .
With the one curve you can divide it into equal lengths . Start with a wide curve and mark the divisions vertically on some parchment (No expense spared ). Draw lines across to a fixed point . That will give proportional divisions for any length curve. Now repeat that for the vertical points (heights ) on the first curve. You will be able to develop all the cross curves you need .
The drawing eliminates all the mathematics .
Was that near the time they put perspective into paintings ? (No about 1450 ).
There seemed to be some confusion on this forum about computer programs so try a basic method using paper and pencil to get a nice result .
Todays homework .

Bottom line here is why does a curtate cycloid shape sound better ? It`s not enough to say , all the best violins that look right --sound better . What is the physical thing that changes the vibrations ? If we stay at the "Looks right--Sounds better " stage we have not really made much progress .

Cicloidi Curtati.

[John Cadd]

I may be crediting Stradivari with too much insight . If he experimented with various improvements to violins he would not necessarily have understood the scientific reasons for successful outcomes . If it sounded better ,that would be enough to stay with the change . As long as he knew what part of the violin had been changed , he would accept his limitations and be grateful and say a few extra prayers in church . No worries about forums to spoil his days .