For Peter KG, Don Noon, and others interested in engineering.

[David Beard]

Personally, I much prefer historical observation to an engineering approach to violin making.  But I do agree that the role of curvature in stiffness deserves greater consideration.

 

Effective stiffness is not just a matter of material stiffness and thickness, but also of geometric stiffness.  

 

Perhaps people focus on the material stiffness and thickness because the geometry aspect seems harder to grasp?  But it's probably sufficient to be familiar with the principles that are and were well known in architecture, rather than bogging down in complicated math equations. 

 

If we basically understand why a thin flat metal yardstick is stiff in one direction but floppy in the other, why a T bar in contrast is stiff in each direction, that a cupped dome is geometrically stiff in all directions, that the crest of an arch only moves up and down if the ends of the arch can move in and out, that a curved channel shape is geometrically stiff along the channel but floppy across it, etc; then we are well positioned to consider geometric stiffness as we carve a plate.  No math required.

 

But even so, we still have the problem of understanding where and when stiffness and flexibility are desired in a good instrument.  This is where historical observation seems much more fruitful to me than an engineering approach.

 

(Also, thank goodness for the various animations showing the actual motion of classical instruments!)

 

 

 

 

 

[John Masters]

Personally, I much prefer historical observation to an engineering approach to violin making.  But I do agree that the role of curvature in stiffness deserves greater consideration.

 

Effective stiffness is not just a matter of material stiffness and thickness, but also of geometric stiffness.  

 

Perhaps people focus on the material stiffness and thickness because the geometry aspect seems harder to grasp?  But it's probably sufficient to be familiar with the principles that are and were well known in architecture, rather than bogging down in complicated math equations. 

 

If we basically understand why a thin flat metal yardstick is stiff in one direction but floppy in the other, why a T bar in contrast is stiff in each direction, that a cupped dome is geometrically stiff in all directions, that the crest of an arch only moves up and down if the ends of the arch can move in and out, that a curved channel shape is geometrically stiff along the channel but floppy across it, etc; then we are well positioned to consider geometric stiffness as we carve a plate.  No math required.

 

But even so, we still have the problem of understanding where and when stiffness and flexibility are desired in a good instrument.  This is where historical observation seems much more fruitful to me than an engineering approach.

 

(Also, thank goodness for the various animations showing the actual motion of classical instruments!)

I can't do the math,  just make the observation.  The balloon illustration (See "Apologies" thread)  suggests that the web outside the inflection may be the more stretchy portion.

[curious1]

Personally, I much prefer historical observation to an engineering approach to violin making.  But I do agree that the role of curvature in stiffness deserves greater consideration.

 

Effective stiffness is not just a matter of material stiffness and thickness, but also of geometric stiffness.  

 

Perhaps people focus on the material stiffness and thickness because the geometry aspect seems harder to grasp?  But it's probably sufficient to be familiar with the principles that are and were well known in architecture, rather than bogging down in complicated math equations. 

 

If we basically understand why a thin flat metal yardstick is stiff in one direction but floppy in the other, why a T bar in contrast is stiff in each direction, that a cupped dome is geometrically stiff in all directions, that the crest of an arch only moves up and down if the ends of the arch can move in and out, that a curved channel shape is geometrically stiff along the channel but floppy across it, etc; then we are well positioned to consider geometric stiffness as we carve a plate.  No math required.

 

But even so, we still have the problem of understanding where and when stiffness and flexibility are desired in a good instrument.  This is where historical observation seems much more fruitful to me than an engineering approach.

 

(Also, thank goodness for the various animations showing the actual motion of classical instruments!)

We can all watch the rising of the sun and the changing of the seasons but without language we are enigmas even to ourselves.

[curious1]

Well,  you can try to go as light as you can for a specific M5, for example 345 Hz. 65 g for top and 95 g for back is quite optimal.

 

No distort! The contrary actually, tuned top:

 

Top_arch_tuned1.jpg Top_arch_tuned2.jpg

I can say nothing for or against what I see Peter (except lay off the sandpaper). Is it optimal? Ask Zuckerman what he thinks of Perlman's Strad?

[Peter K-G]

I can say nothing for or against what I see Peter (except lay off the sandpaper). Is it optimal? Ask Zuckerman what he thinks of Perlman's Strad?

 

Not optimal for Zuckerman he is a DG guy (Seen the clip, Two gentelmen from Cremona)

 

The beauty is that you can choose to make what ever plates you want, (again) weight and M5. The arching turns out "Cremonese" style when doing this.

 

DG's have genarally heaviar backs and higher A0. I made a misscalculation of MC% with my ongoing restoration project, see how it turned out on my bench. For this project i can not change the arches, so the back will be heavier and f-holes are bigger compared to the inner volume -> A0 is also higher.

[curious1]

Personally, I much prefer historical observation to an engineering approach to violin making.  But I do agree that the role of curvature in stiffness deserves greater consideration.

 

Effective stiffness is not just a matter of material stiffness and thickness, but also of geometric stiffness.  

 

Perhaps people focus on the material stiffness and thickness because the geometry aspect seems harder to grasp?  But it's probably sufficient to be familiar with the principles that are and were well known in architecture, rather than bogging down in complicated math equations. 

 

If we basically understand why a thin flat metal yardstick is stiff in one direction but floppy in the other, why a T bar in contrast is stiff in each direction, that a cupped dome is geometrically stiff in all directions, that the crest of an arch only moves up and down if the ends of the arch can move in and out, that a curved channel shape is geometrically stiff along the channel but floppy across it, etc; then we are well positioned to consider geometric stiffness as we carve a plate.  No math required.

 

But even so, we still have the problem of understanding where and when stiffness and flexibility are desired in a good instrument.  This is where historical observation seems much more fruitful to me than an engineering approach.

 

(Also, thank goodness for the various animations showing the actual motion of classical instruments!)

It doesn't matter where you start, historical observation or engineering, after the first instrument, unless you make purely on visual criteria, it is engineering.

When you select wood do you pick it up and gauge how heavy it is? Density

Do you listen to its pitch? Stiffness

Why would one make an arch higher or lower than another but for principals of engineering. (Unless of course you are copying the visual criteria of another instrument)

Etc....

Material stiffness and geometric stiffness go hand in hand for a successful outcome.

In my own work, what I don't I don't know. For the moment, I pick the low hanging fruit and try to master that. Hopefully enlightenment will come.

[Torbjörn Zethelius]

I am dissatisfied with copying Cremonese arching and with carving it until it looks right. I would like to find a way to define the arching in an architectural/geometric way without using templates.

Curious1, Have you read my article Inside Information? In that article I explain the way to make the various arches that you find in Cremonese instruments without the use of templates. All you need is a straight edge or a chain. Also, if you think of the arch from the inside (when you get it), it becomes apparent that its purpose is purely acoustic.

[curious1]

Curious1, Have you read my article Inside Information? In that article I explain the way to make the various arches that you find in Cremonese instruments without the use of templates. All you need is a straight edge or a chain. Also, if you think of the arch from the inside (when you get it), it becomes apparent that its purpose is purely acoustic.

Hi Torbjorn,

I have read your article and found it very interesting.

Here is my dilemma.

I don't want my outcomes dictated by the limitations of my construction methods. I don't want the arch to be an artifact of the physical act of creating it but instead an artifact of my understanding of material and structural properties. I want to define the shape not let the chain define it.

[Don Noon]

I don't want my outcomes dictated by the limitations of my construction methods.

I'm in absolute agreement here.

There is no logical connection that can be made between a formula-based construction method and a desirable tonal result. The only benefit, perhaps, might be a small measure of consistency (if you think that is a benefit), and the feeling of non-randomness by the practitioner.

To me it is far more logical to seek out fabulous-sounding instruments and trying to understand what makes them so... or at least follow the concept of the form, arching, graduations (and if possible the properties of the wood they used) to see what happens. Cherry-picking 300 years of trial-and-error.

[FredN]

Hi Curious 1-

I've made around 8 sets of templates  for arching the top and back using a bent stick. A bent stick will produce a catenary, but you can get other shapes, depending on where you place the pin or pins around which the stick is bent. The method is simple- you space out cross lines (I found 8 templates was sufficient)  on your outline of the ribs, draw your long arch, shaping to your desire with pins and draw the long arch. The long arch establishes the height of each cross arch (template for that station) and the cross arch line height is determined by sticking a pin in where the crossline and long arch line intersect. Shifting the pin location or multiple pins can give you a sharper or flatter shaped template. The recurve, or gutter area, is constructed by also using bent sticks where a tangential line from the main arch meets the recurve, so the gutter width is reflective of the arch at each station. Forgot- you also make a template for the long arch, which is where you first start to remove wood to shape this arch.  fred

[Marty Kasprzyk]

Hi Curious 1-

I've made around 8 sets of templates  for arching the top and back using a bent stick. A bent stick will produce a catenary, but you can get other shapes, depending on where you place the pin or pins around which the stick is bent. The method is simple- you space out cross lines (I found 8 templates was sufficient)  on your outline of the ribs, draw your long arch, shaping to your desire with pins and draw the long arch. The long arch establishes the height of each cross arch (template for that station) and the cross arch line height is determined by sticking a pin in where the crossline and long arch line intersect. Shifting the pin location or multiple pins can give you a sharper or flatter shaped template. The recurve, or gutter area, is constructed by also using bent sticks where a tangential line from the main arch meets the recurve, so the gutter width is reflective of the arch at each station. Forgot- you also make a template for the long arch, which is where you first start to remove wood to shape this arch.  fred

I've used your method for designing many of my top and back longitudinal and cross arches.  Its simple and quick but it totally lacks the mystique necessary for widespread use.

[Torbjörn Zethelius]

.... its purpose is purely acoustic.

 

Hi Torbjorn,

I have read your article and found it very interesting.

Here is my dilemma.

I don't want my outcomes dictated by the limitations of my construction methods. I don't want the arch to be an artifact of the physical act of creating it but instead an artifact of my understanding of material and structural properties. I want to define the shape not let the chain define it.

OK, I see. You didn't get it.

 

Of course you need good materials for a start.

 

I guess that begs the question, how much control do you need?

[Carl Stross]

I don't want my outcomes dictated by the limitations of my construction methods. I don't want the arch to be an artifact of the physical act of creating it but instead an artifact of my understanding of material and structural properties. I want to define the shape not let the chain define it.

 

 

Torbjorn's method seems to do just that. Though I wish he would re-write the article with more photos and "how to's".

[David Beard]

I'm not sure the historical examples support the notion of letting the materials govern the shaping of the arching.  Of course, if you're aiming to engineer a superior result without first understanding what worked for the old masters, then I guess the historical practices don't matter?

 

It seems that virtually all the variation in the old Italian examples lies in the approach to edges and channel, rather than the central section of the arch.   The central arch sections seem to be extremely consistent in shape, across different regions and centuries of Italian making, and even looking at other arched bowed instruments.   Through the central section of classical Italian arches, you find pretty much the same shape on any instrument for a given distance from the center line and a given fall/rise from the level at the centerline. 

 

This suggests that some fixed method of making did indeed set the shape for any given amount of fall fo a given distance from the center line.  The apparent differences in various old Italian arches lay not in the central curve of the arches, but in the shape and height of the edge, the level at the centerline, the channel, and in the transition from the channel into the central section of arching.

 

This shape in the central section of the arches is very very similar to a catenery curve, but I don't the evidence supports an actual match.

[FredN]

I've used your method for designing many of my top and back longitudinal and cross arches.  Its simple and quick but it totally lacks the mystique necessary for widespread use.

 

Hi Marty, it is nice to know at least one person tried it. As you say, too routine.  Hope you are still saying  "what if I ...". fred 

[FredN]

I'm not sure the historical examples support the notion of letting the materials govern the shaping of the arching.  Of course, if you're aiming to engineer a superior result without first understanding what worked for the old masters, then I guess the historical practices don't matter?

 

It seems that virtually all the variation in the old Italian examples lies in the approach to edges and channel, rather than the central section of the arch.   The central arch sections seem to be extremely consistent in shape, across different regions and centuries of Italian making, and even looking at other arched bowed instruments.   Through the central section of classical Italian arches, you find pretty much the same shape on any instrument for a given distance from the center line and a given fall/rise from the level at the centerline. 

 

This suggests that some fixed method of making did indeed set the shape for any given amount of fall fo a given distance from the center line.  The apparent differences in various old Italian arches lay not in the central curve of the arches, but in the shape and height of the edge, the level at the centerline, the channel, and in the transition from the channel into the central section of arching.

 

This shape in the central section of the arches is very very similar to a catenery curve, but I don't the evidence supports an actual match.

 

Hi David, such a thought or to look for this never entered my mind, but I can see this in a journeymen's system where your only knowledge is what you are taught.  fred

[David Beard]

A catenary would seem a very reasonable curve to control this.  However, catenaries appear to be slightly more curved than the classical examples.  Also, the greater the fall/rise for a given distance from centerline, the greater the discrepancy.

[curious1]

OK, I see. You didn't get it.

Of course you need good materials for a start.

I guess that begs the question, how much control do you need?

I guess I didnt get it.

But then....

[curious1]

I'm in absolute agreement here.There is no logical connection that can be made between a formula-based construction method and a desirable tonal result. The only benefit, perhaps, might be a small measure of consistency (if you think that is a benefit), and the feeling of non-randomness by the practitioner.To me it is far more logical to seek out fabulous-sounding instruments and trying to understand what makes them so... or at least follow the concept of the form, arching, graduations (and if possible the properties of the wood they used) to see what happens. Cherry-picking 300 years of trial-and-error.

[curious1]

I'm not sure the historical examples support the notion of letting the materials govern the shaping of the arching.  Of course, if you're aiming to engineer a superior result without first understanding what worked for the old masters, then I guess the historical practices don't matter?

 

It seems that virtually all the variation in the old Italian examples lies in the approach to edges and channel, rather than the central section of the arch.   The central arch sections seem to be extremely consistent in shape, across different regions and centuries of Italian making, and even looking at other arched bowed instruments.   Through the central section of classical Italian arches, you find pretty much the same shape on any instrument for a given distance from the center line and a given fall/rise from the level at the centerline. 

 

This suggests that some fixed method of making did indeed set the shape for any given amount of fall fo a given distance from the center line.  The apparent differences in various old Italian arches lay not in the central curve of the arches, but in the shape and height of the edge, the level at the centerline, the channel, and in the transition from the channel into the central section of arching.

 

This shape in the central section of the arches is very very similar to a catenery curve, but I don't the evidence supports an actual match.

"The central arch sections seem to be extremely consistent in shape, across different regions and centuries of Italian making, and even looking at other arched bowed instruments.   Through the central section of classical Italian arches, you find pretty much the same shape on any instrument for a given distance from the center line and a given fall/rise from the level at the centerline". 

That is indeed a broad statement and I don't believe is true.

[curious1]

Torbjorn's method seems to do just that. Though I wish he would re-write the article with more photos and "how to's".

What is the "that" it seems to do?

[curious1]

Hi Curious 1-

I've made around 8 sets of templates  for arching the top and back using a bent stick. A bent stick will produce a catenary, but you can get other shapes, depending on where you place the pin or pins around which the stick is bent. The method is simple- you space out cross lines (I found 8 templates was sufficient)  on your outline of the ribs, draw your long arch, shaping to your desire with pins and draw the long arch. The long arch establishes the height of each cross arch (template for that station) and the cross arch line height is determined by sticking a pin in where the crossline and long arch line intersect. Shifting the pin location or multiple pins can give you a sharper or flatter shaped template. The recurve, or gutter area, is constructed by also using bent sticks where a tangential line from the main arch meets the recurve, so the gutter width is reflective of the arch at each station. Forgot- you also make a template for the long arch, which is where you first start to remove wood to shape this arch.  fred

Thank you Fred for describing your methods. They are elegant in their simplicity. I would suggest an even simpler method. Using a similar grid and a calculator the heights of the various points can be generated from known formulas. The advantage here is that instead of defining a surface that may be in compression or tension a median point can be defined and perhaps a truer arching created. It also eliminates the intermediate step of creating templates.

[curious1]

OK, I see. You didn't get it.

 

I guess that begs the question, how much control do you need?

A lot.

[Torbjörn Zethelius]

I want to define the shape not let the chain define it.

The chain is a guide, like arching templates but flexible. For years I used only the shadow from a straight edge. It worked fine, but the chain gives full control. I feel that I make better instruments with it.

 

Torbjorn's method seems to do just that. Though I wish he would re-write the article with more photos and "how to's".

Hi Carl, you're getting it.   I may do it one day. There was a limited amount of space to write in, but overall I think the message got through.

 

What is the "that" it seems to do?

It allows you to make the various types of archings that you see in Cremonese instruments. If you want to do something other, then by all means invent a different method. But I would still recommend you use a chain. Because it works.

 

When all is said and done; you do what you're comfortable with.

 

 

Edit: I'll be gone for a couple days from now...

Edited September 15, 2013 by Torbjörn Zethelius

[curious1]

The chain is a guide, like arching templates but flexible. For years I used only the shadow from a straight edge. It worked fine, but the chain gives full control. I feel that I make better instruments with it.

 

Hi Carl, you're getting it.   I may do it one day. There was a limited amount of space to write in, but overall I think the message got through.

 

It allows you to make the various types of archings that you see in Cremonese instruments. If you want to do something other, then by all means invent a different method. But I would still recommend you use a chain. Because it works.

 

When all is said and done; you do what you're comfortable with.

 

 

Edit: I'll be gone for a couple days from now...

It works making arches or making violins that sound great?