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Why arching shape?


reguz

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15 hours ago, Bill Yacey said:

After about the 4th page, I couldn't be bothered to read any further.

What are you trying to prove or disprove? If you think you know better, get to the point an re-educate everyone here. If not, why waste everyone's time with circular questions?

All right Bill I will let you know my opinion whay we need archong shape. When string load start deflecting the instrument the belly become buckled and stress conditions arise on many different curve shape. A string at pitch produces a specific frequencyu. A bend curve shape also can vibrate with a specific frequency. When we have many curve shapes we can assume we mustr accept that they can vibrate at meny differnt frequency. A flat plate donnot hold this quelity. So my opinion is tha arching shape provide special quality a flat structure does not have.

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34 minutes ago, reguz said:

All right Bill I will let you know my opinion whay we need archong shape. When string load start deflecting the instrument the belly become buckled and stress conditions arise on many different curve shape. A string at pitch produces a specific frequencyu. A bend curve shape also can vibrate with a specific frequency. When we have many curve shapes we can assume we mustr accept that they can vibrate at meny differnt frequency. A flat plate donnot hold this quelity. So my opinion is tha arching shape provide special quality a flat structure does not have.

This is the same mistake Vigdorchek makes.  He considers adjacent areas vibrating while neglecting the fact that they are joined together.  (ignoring boundary conditions)  

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4 hours ago, reguz said:

So my opinion is tha arching shape provide special quality a flat structure does not have.

I would go so far as to say that it is a FACT that curved plates have different vibrating mode shapes than flat plates, and different curves will vibrate (and sound) differently.  I also believe that anyone remotely familiar with violinmaking understands this.

Those more familiar with violins usually understand that there is no single sound that is ideal, all pieces of wood are slightly different, and logically there is therefore no single arch shape that is optimum.  

This seems very much like yelling at a deaf horse, so I think I'll stop now.

 

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26 minutes ago, Don Noon said:

I would go so far as to say that it is a FACT that curved plates have different vibrating mode shapes than flat plates, and different curves will vibrate (and sound) differently.  I also believe that anyone remotely familiar with violinmaking understands this.

Those more familiar with violins usually understand that there is no single sound that is ideal, all pieces of wood are slightly different, and logically there is therefore no single arch shape that is optimum.  

This seems very much like yelling at a deaf horse, so I think I'll stop now.

 

Do, You seem to bee of opinion that it does no matter haw the transtion from one curce shape to the next, the next, the next has any influence on the behaior of stress producing condition and with that influence on how the plate may vibrate not paying any atterntion to how to graduate the plate thickness in relation to the arching shape and the wood fiber condition. 

I state on good ground that the arching shape you find on my interternet is optimal in the transition from the next to the next to the next cross section.

Yes stop now because I see you have difficulty understanding

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2 hours ago, reguz said:

Do, You seem to bee of opinion that it does no matter haw the transtion from one curce shape to the next, the next, the next has any influence on the behaior of stress producing condition and with that influence on how the plate may vibrate not paying any atterntion to how to graduate the plate thickness in relation to the arching shape and the wood fiber condition. 

 

I don't recall Don ever saying or implying anything of the kind. Much to the contrary....

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3 hours ago, reguz said:

Dear Mr. Zuger

 

There seems to be one question that interests me.  For small vibrations,  internal stresses will not affect the frequencies of the normal modes.  At one time I wondered if arching shape and placement of the inflection line might be placed to mimimize the potential energy in the stresses. The idea was to ask if minimizing stresses in some sense was good for tone.

It seemed to me that damping might vary with internal stress in the wood.  Also, I expected that a nearly-optimal arch would allow the inflection line to creap over time to minimize any internal stresses.  This was a view from noting that the curvature of the surface had positive Gaussian curvature inside the inflection and negative curvature outside.  (and zero at the inflection) Would this cause a slow deformation to shift the inflection line slightly?

I was curious because of the views of some that arching was more important than graduations.  The math would be not of vectors,  but of tensors.  I came up blind  because of math deprivation.  Also,  I did not see a way that stresses could affect sound except through some kind of damping mechanism.  One is nowhere near any kind of buckling forces.

I still wonder about the affect of stresses on tone.  There is some evidence for it in for example the tightness of a soundpost.

But this is not the sort of thing that you are talking about anyway.  Or does not seem to be.  But there is still an interesting question regarding stresses and sound.  I think it is a serious physical question.

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2 hours ago, David Burgess said:

I don't recall Don ever saying or implying anything of the kind. Much to the contrary....

To be more clear, I have been consistent in saying that curvature and inflection points of the plate matter a LOT to how it vibrates and sounds.  But I DON'T believe that static stress does much to the vibration behavior (and therefore the sound) of the violin body.  The one exception is a change in static stress, which generally affects damping...  but that's a transient effect, and settles in after a relatively short time.

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1 hour ago, Johnmasters said:

There seems to be one question that interests me.  For small vibrations,  internal stresses will not affect the frequencies of the normal modes.  At one time I wondered if arching shape and placement of the inflection line might be placed to mimimize the potential energy in the stresses. The idea was to ask if minimizing stresses in some sense was good for tone.

It seemed to me that damping might vary with internal stress in the wood.  Also, I expected that a nearly-optimal arch would allow the inflection line to creap over time to minimize any internal stresses.  This was a view from noting that the curvature of the surface had positive Gaussian curvature inside the inflection and negative curvature outside.  (and zero at the inflection) Would this cause a slow deformation to shift the inflection line slightly?

I was curious because of the views of some that arching was more important than graduations.  The math would be not of vectors,  but of tensors.  I came up blind  because of math deprivation.  Also,  I did not see a way that stresses could affect sound except through some kind of damping mechanism.  One is nowhere near any kind of buckling forces.

I still wonder about the affect of stresses on tone.  There is some evidence for it in for example the tightness of a soundpost.

But this is not the sort of thing that you are talking about anyway.  Or does not seem to be.  But there is still an interesting question regarding stresses and sound.  I think it is a serious physical question.

John answering on the two latest sentenses. I have been testing on an violin made 40 years ago and never touched how stress affect the responce on the accoustic outcome. I did this regarding the function of the frame work. arching shape that become stress by the compression forces on the longitudinal curve on the bout shape changes by reducing the varnisch. In the beginning of this polidhing process I was not able observing quality differences. However the player (I do not play) Staffan Borseman the former concert master of the Denish Radio orchestra Chttps://www.thestrad.com/violinist-and-stringed-instrument-expert-staffan-borseman-has-died-aged-60/5940.article), could hear clear difference by each polishing moment. We worked together seven years. Finally I also could hear the diference. We together made the conclusion that reducing varnisch changes the stress on the bout outside and minor on the inside. Also the location I polished had great influence on the acoustic result. I did this process over and over again. Some times it became real bad, which also shoe that stress is involved. Yes al this is an interresting phusical question. I believe I learned over a period of five years to understand what the quality of my geometric arching influences. Looking at the holograpic pictutre opf the back by slight increasing the d string, very little, we get a map that show where the structure bulge outward. The balck lines are principlaly a hinge. + on one side and - on the other. So what we see is inflection point along the line. On the location of the STL they become strtight and tells us that at that point we have resistant, the frame work. Unfortunatally I'm not enough educated being able to discuss Gaussian curvature inluence on arching shape. This is a total open field in my knowledge.

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