Rib Taper hypothesis #43,759


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10 minutes ago, Laurentius said:

 Maybe the conical  hole was driven so deeply because the master wanted whoever was doing the thicknessing not to bother him further about it, as he had better things to do, and so he decided where it should be thickest,  augured a good deep hole in the spot, and then passed it off to others in the shop to finish the job.   The tiny spot left on the outside may not have been considered a big issue in that case, considering the annoyance of having apprentices or family members continually asking for guidance when they planed away a hole that wasn't deep enough. ;)

Given the immaculate finish on Amati instruments, this idea seems like nonsense. Why would they go to the trouble of such precise work everywhere else, but somehow it’s ok to poke a compass right through the back.

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You can dig that deep with a divider or compass leg.  But, as people are asking, why would you ever by accident on a 5 or 6mm back.  I why whole families so frequently dig all the way through unless somehow they wanted to?

I've always guessed it's likely related to working the central thickness of the back.  But that's just a guess.   I do believe that concentric circles are helpful in working the back mass, even when it is given an elongated form.  Concentric circles give you equal distances to measure thicknedd for symmetry, even if you make an elongated mass.

But still, why allow yourself to frequently punch through?

I can see digging that center mark deep as you work.  That way it doesn't disappear as you carve down the thickness.  But all the way through?

Punching through does show you the location from the outside. But why is that so valuable?  And, they don't punch through consistently. So that seems an unlikely motive.

A hole that goes all the way through, or nearly so, does allow you to see that max central thickness.  Perhaps that was the benefit.  Simply seeing the thickness easily you worked, rather than measuring in some other way?

Perhaps they combined the several motives.  Start the hole with dividers to help you govern thicknessing of the central back mass.  Dig the hole deep enough not to disappear as you carve.  As you get closer, dig nearly or actually through for just a convenient eyeballing of thickness at max point?

 

But this is all just fantasy speculation. 

And without widely publicly available very accurate plate maps, 3d imaging, or adequate photo imaging putting the position in context, only a very few people have any opportunity to examine or meaningful consider enough examples to shed light in this puzzling detail.

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2 minutes ago, Laurentius said:

Well, by the little emoji I put in I meant this to be a little tongue in cheek, but not completely.  If you have seen one of these little spots, they are barely noticeable.  At one time they were a secret that dealers used to authenticate instruments, not known to the rest of us.  The first time I was shown one, I was told  'keep this to yourself".  I haven't had the chance to look inside an Amati, but I once read somewhere that some of the inside work could be quite a bit less immaculate, as if the kids were put to work doing some of the tasks.  Maybe Bruce could enlighten us on that.


Many of the old makers left the interior work straight off the tools, in the case of blocks and linings. What wasn’t easily seen just needed to be functional.

If you were thicknessing a back, using a compass method, how many times would you need to redraw this circles, for one leg to go through the back completely?
Whatever they were doing, I doubt it needed to be remarked so many times that the dividers went through on their own.

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On 11/21/2020 at 2:02 PM, Wood Butcher said:


Many of the old makers left the interior work straight off the tools, in the case of blocks and linings. What wasn’t easily seen just needed to be functional.

If you were thicknessing a back, using a compass method, how many times would you need to redraw this circles, for one leg to go through the back completely?
Whatever they were doing, I doubt it needed to be remarked so many times that the dividers went through on their own.

:)

 

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On 11/21/2020 at 4:00 PM, Davide Sora said:

how it was possible to leave a hole so deep

It was the origine of my lack of enthusiasm  when i wrote "need to be describe"

because  the thickness process  mentioned doesn't explain this feature

it's also why I propose these multiple  finalities 

a clamping device could "fill a bit, the hole of the theory" 

What we could imagine that:


- the nail  help to hold the back 

- the nail can be a reference for the heigh of the back

- the nail can be a reference for the thickness 

- the nail can be a reference for the soundpost (al least for the only untouched violin we know )

 

 

Capture d’écran 2020-11-22 à 18.47.29.png

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4 hours ago, francoisdenis said:

 

It was the origine of my lack of enthusiasm  when i wrote "need to be describe"

because  the thickness process  mentioned doesn't explain this feature

it's also why I propose these multiple  finalities 

a clamping device could "fill a bit, the hole of the theory" 

What we could imagine that:


- the nail  help to hold the back 

- the nail can be a reference for the heigh of the back

- the nail can be a reference for the thickness 

- the nail can be a reference for the soundpost (al least for the only untouched violin we know )

 

 

Capture d’écran 2020-11-22 à 18.47.29.png

I do not remember having seen a hole on an Amati or a Guarneri that was not visible on the outside of the back, sometimes just barely visible. Along with other theories, the idea of an identifying mark is intriguing.

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9 hours ago, David Beard said:

I would guess that most likely it relates to the extra mass/thickness of back.

That could be since the back has the obvious thickness graduation and the belly is 'almost' uniform thickness. 

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16 hours ago, Bruce Carlson said:

I do not remember having seen a hole on an Amati or a Guarneri that was not visible on the outside of the back, sometimes just barely visible. Along with other theories, the idea of an identifying mark is intriguing.

I might add with all different arching heights. High to low.

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1 hour ago, MikeC said:

That could be since the back has the obvious thickness graduation and the belly is 'almost' uniform thickness. 

 Cozio claims that the Amati family thicknessed their fronts the same as the backs. There is at least one known Stainer violin front which measures 4.5mm in the middle, tapering to 2.4mm at the edges. Many English makers who made well observed Amati model violins were thicknessing the front the same as the back well into the c19th. 

 

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13 hours ago, MikeC said:

Another mystery is why the hole is only on the back, not the belly?  Any theories? 

Your Wed. Nov 16, 7:15am post shows the x-ray of an instrument in the Freidberg Cathedral that had a central soundpost with a metal pin in it with its end sticking into a hole in the back plate.

My hypothesis is that the sound post was inserted after the body was assembled.  The pin and back plate hole were used to ensure the desired location. 

The same thing couldn't be done on the top plate because another extending upper pin would obstruct the sound post insertion and its sliding into position.  Since an upper pin couldn't be used there was no need for a locating hole in the top plate too. 

 

 

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39 minutes ago, Three13 said:

Which British makers have you seen go whole hog on ample, Cannone-style graduations?

Can't say I have any experience of that. If anything the backs can be on the thin side, sometimes thinner than the fronts

31 minutes ago, Wood Butcher said:

This is entirely different to my reading of English thicknessing, which has a thick spine running down the centre of the plates, becoming thinner towards the edges.

 

Either way, they are not of a uniform thickness

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