Violin Forum/Message Board

[Michael Darnton]

I was upset that I had time fitting a six-pixel line to a sox-pixel line taken from the Strad arch so that a couple of pixels of arch wouldn't stick out for a short stretch, and you use a 1/4" chain, with twists in it, even, and are satisfied if the results are within a couple of mm? Based on Torborg's comment over there, the two of you have been totally blinded by enthusiasm to the point where the concept of a match is meaningless. Clearly we have nothing to discuss here unless it's about visual discrimination and standards in violin making.,

[CT Dolan]

So, perhaps to get to the heart of the matter, I'd like to ask a few questions:

1. What is the form of the back and belly long arch (on the outside)? I know the form of the cross arch is that of a curtate cycloid, but what of the long arch? Surely there is a form present, can it be represented mathematically?

2. If the past masters worked from the outside and developed the form as such (from the outside), what drove their decisions and determined the shape of these outer forms?

3. Why does the long arch of the belly differ from that of the back? What purpose, acoustically, does this difference serve?

I am trying (and hoping) to learn something here and would rather this not become a stale-mate. If someone has answers to the questions above (some or all), please speak.

[Michael Darnton]

[Oded Kishony]

Michael,

In my experience the top deforms noticeably over time after the strings are tensioned. The center flattens and the ends bulge out. Have you accounted for this deformation?

Oded

[Michael Darnton]

I don't account for it, and for what it's worth, the violins I've made in about the last 10 years are remarkably stable--many of them still have the same bridges and posts, and projection hasn't moved a bit. I'm making violins that are not distorted, of course--my method gives an arch which is undistorted and stable, but also resembles the Cremonese arch ( not the collapsed version!) in some important respects that I was unable to figure out until I started using circles and cycloids. I notice tonal effects too--one of them being that even my thickest del Gesu models respond well from the very first day, which was not the case with previous violins on the same pattern. We've also discussed, in other places, the fact that I'm not getting wide variations in pitch from drying varnish in the lightbox.

I believe that all of these effects (and there are others, less verbalizable) are partially a result of the integrity (consistency, internal uniformity, whatever) of the design. Integrity is hard to explain, and harder to execute, but a consistent plan for the entire arching is the only way to accomplish it. I think there are other ways to engineer integrity but they don't result in a product that looks Cremonese in the important respects.

It's an aside, only slightly related, that I have a friend who worked at Hills. He said that they were given only and E and G string when setting up violins, and that the policy was that if the string height changed when the instrument was at full tension with all the strings, something was inherently wrong with the instrument, and that needed to be figured out.

Basically, I think we accept immediate gross deformation because the standard modern ways of arching result in it. I made the analogy elsewhere of a toothpick bridge, made as strong and light as possible. When you selectively add toothpicks (strength) in only one area, you don't make the bridge stronger--you actually make it weaker. That's the type of integrity, or lack thereof, that I'm talking about.

[CT Dolan]

Michael, thank you for taking the time to reply. As I understand it, the book by Francois Denis deals with this subject in pretty thorough manner, am I correct? If so, do you know of anywhere the English edition of the book can still be found? I have not been successful finding a copy in English. Thank you.

[Michael Darnton]

The only place I know that has/had the book is http://amatibooks.com

[CT Dolan]

Christian told me he was out of stock and did not foresee another printing of the English edition, thank you though. Someone on the other site asked the following, feel free to comment if you like:

"As an aside, mr Darnton wrote this in the other forum ;

In my workshop I show a nice method of generating top and back long arches which almost exactly replicate what you see on old instruments. The top arch is a particularly interesting case, inasmuch as the "humps" at the end are not random, but very predictable with a simple plan using circles. Actually, the long archings are much less sophisticated than the cross archings, but a proper long arch "explains" a lot of visual things that Cremonese violins are recognized for.

Can someone who belongs to the other forum ask him about this method, or has any one been to the class, and heard this lesson?"

I realize that people paid good money to be taught what is mentioned above, however for some of us the opportunity to learn in such a setting simply does not exist, so please consider this as well. Thank you.

[M.Lange]

There really is no need to discuss, if the shape of the arching is a catenary or a cycle. In this case you are both right, Michael and CT Dolan.
As a matter of fact, you won't even see any difference between a catenary curve and a cycle at the scale that is of interest for us.
To illustrate that:
The green line is the catenary, the red the cycle.



Now, if you look closer ( only at the section that might be a long arch),



there simply is no (visual) difference between the two.

Matthias

[Andres Sender]

[Michael Darnton]

Matthias, there's also the problem of cross archings, and on those, the recurve and inflection points.

Also, am I incorrect in thinking that the length of the chain matters? You appear to have used an infinitely long chain, something in short supply in most violin shops. What does a catenary look like when the chain is more like violin size, more tensely stretched?
---------------
Later: yes, I'm incorrect, apparently.not.

[CT Dolan]

Yes, Michael has been amazingly generous and very helpful to the development of my understanding, and I'd like to take a moment to personally say "thank you".

[actonern]

To me this has been a vigorous seminar... Michael, I can just see you, deeply close-focused on the final turns of a scroll or purfling corners, needing a back stretching break, whizzing accross your shop on castors to the computer, pecking away at the keys...

We're all very grateful... lots of us, that is, that never had the benefit of a formal apprenticeship/education in a guild like setting and who nonetheless take the hobby very seriously... it would be so difficult to get better without the generous assistance of folks like you.

I'm not obsequious about this, but the fact is that before the internet came along there was MUCH more silence and ambitguity about the craft of making by people who knew a lot. I've been a STRAD reader since the early 80's and the articles on varnish and other critical arcana were much more general and less practically expressed than the open environment that appears to exist these days.

I couldn't be more thrilled!

[M.Lange]

[Roger Hill]

Michael: I am sorry you are upset, but here are the conditions: The two chains are 3mm and 2mm. The 2mm chain has some runout, so prior to starting placement I hold the chain up by one end to allow the entire chain to rotate to its unstressed state. I attempted to fit the upper edge of the heavy chain as close to the line as I could. With my photographic skills, it is difficult to create a high resolution photo showing how the chain lies next to the curve. That is the reason for the shot from above. There are certainly limitations to what I presented, but no gimmickry. Enough said.

Roger Hill