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shrinking tenor viola


avandesande
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I am looking into possible building Andrea Guarneri viola, I don't have access to the ‘Conte Vitale’ Andrea Guarneri viola poster but there is a 48cm tenor in luthier library.  The outline looks pretty much the same, but I am not sure if I can shrink the other dimensions the same amount (about 85%).  Could someone supply a few dimensions for rib height, arching height and thickness? Hopefully I can extrapolate the other measurements.

Thanks!

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Rib dimensions are given as 38mm at endpin, 35.5mm at neck.
Aching height is 19.8mm for the belly and 19mm for the back.

Seems you won't be making a conte vitale, if you are shrinking it, so I don't know how the measurements will even help. I don't believe violas fit the scale model theory.

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9 hours ago, Wood Butcher said:

Rib dimensions are given as 38mm at endpin, 35.5mm at neck.
Aching height is 19.8mm for the belly and 19mm for the back.

Seems you won't be making a conte vitale, if you are shrinking it, so I don't know how the measurements will even help. I don't believe violas fit the scale model theory.

Thanks, for sure I will just call in 'Guarneri Inspired'.

The tenor is 45.0 button, 40.9 neck so it looks like ribs follow the 85% rule

But arching is 21.4 front, 20.45 back so it looks like a different factor

The belly thickness is really strange 3.8 in the c bouts and actually thicker in lower bout 4.2

The back is a little more what you would expect 6ish in c-bouts and 3 in the upper/lower bouts

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On 5/18/2021 at 3:04 PM, avandesande said:

I am looking into possible building Andrea Guarneri viola, I don't have access to the ‘Conte Vitale’ Andrea Guarneri viola poster but there is a 48cm tenor in luthier library.  The outline looks pretty much the same, but I am not sure if I can shrink the other dimensions the same amount (about 85%).  Could someone supply a few dimensions for rib height, arching height and thickness? Hopefully I can extrapolate the other measurements.

Thanks!

I'll tell ya, my 45.1 cm tenor viola is plenty big and has a distinctive and lovely tenore sound..  It's modeled after the Ashmolean's 1592 Amati.

Careful building too gigantic.

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On 5/18/2021 at 3:04 PM, avandesande said:

I am looking into possible building Andrea Guarneri viola, I don't have access to the ‘Conte Vitale’ Andrea Guarneri viola poster but there is a 48cm tenor in luthier library.  The outline looks pretty much the same, but I am not sure if I can shrink the other dimensions the same amount (about 85%).  Could someone supply a few dimensions for rib height, arching height and thickness? Hopefully I can extrapolate the other measurements.

Thanks!

The shape of a viola can be approximated by a circular disk which has a fundamental mode frequency f  proportional to its thickness t divided the radius R squared:

f ~t/R^2

This can be rearranged to show the the thickness t is proportional to the frequency f times radius R squared:

t~f R^2

So if you want to keep the same mode frequency to keep the same sound character of the Quarneri viola the thickness of your 85% smaller viola should be reduced by about 0.85^2 or 0.72 or 72%.

This assumes the wood has the same speed of sound which never happens.

 

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On 5/20/2021 at 7:26 PM, avandesande said:

Thanks, for sure I will just call in 'Guarneri Inspired'.

The tenor is 45.0 button, 40.9 neck so it looks like ribs follow the 85% rule

But arching is 21.4 front, 20.45 back so it looks like a different factor

The belly thickness is really strange 3.8 in the c bouts and actually thicker in lower bout 4.2

The back is a little more what you would expect 6ish in c-bouts and 3 in the upper/lower bouts

When you reduce the size, I think you should be more concerned in the width of the Cs and the height of the top arching which are among the most responsible for the playability for a correct bow action.
And the stop length > string length, of course

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7 hours ago, Marty Kasprzyk said:

So if you want to keep the same mode frequency to keep the same sound character of the Quarneri viola the thickness of your 85% smaller viola should be reduced by about 0.85^2 or 0.72 or 72%.

Isn't that a bit much ?

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