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Gibson viola


tommyfiddler
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Hello everyone,

I am wondering if you know if there was a Strad poster about the Stradivari Gibson viola. I am interested in the back of this instrument. Its a 1 piece cut on a slab maple back. In his article about this instrument, Mr Hargrave couldn't measure the back so he copied Sacconi's graduation pattern in the article. This give a good indication of the general thickness. But in case of a slab cut, are these measures very different from quarter cut ?

-Tom

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Thanks Oded, although I am looking at data fro actual instruments.

So far, looking in the "Luthier Library" I have found 3 violas that have a slab back (and thickness data) :

Gasparo da Salo

Gaetano Sgarabotto

Lorenzo Storioni

If I look at the thickness, I don't find any consistencies between all of them besides being definitively thicker than a quarter cut one (although looking at only 3 instruments is not a great statistic):

The Da Salo one seem to have a more or less uniform thickness back (around 3mm) varying from 2.7 to 3.3 (apart some odd measure not consistent with the rest) the upper bout is a little bit thinner, but the center of the plate is not really thicker than anywhere else.

The Sgarabotto back is a bit similar to Da Salo, but it is more around 4mm thick than 3, and the center bout seems to be a bit thicker than the rest.

amd the Storioni is a bit all over the place ranging from 2mm to 6mm with apparently what I could call a big "spine" in the middle going from the middle of the upper bout to the middle of the lower bout (although its difficult to tell exactly as the number of measure is not big enough).

-Tom

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Thanks all,

Then, I guess mine is really more flexible than usual. The density of the maple is 0.49 ! And right know the back thickness ranges from 3.0 to 5.0mm. It weights 135gr, feels quite flexible and I wouldn't want it to be more flexible. Its nice though, look here (right click on the image and select "view image" if you want to see it bigger).

I guess that I am going to leave it as it is.

-Tom.

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Ill see if i can find some info for you, around 10 years ago i bought several boxes of items from a deceased violinmaker and one box was just full of drawings ,notes ,plans ,graduations ,moulds, etc... all for the Gibson viola,i think he must have had an obsession with it.Hopefully i will remember where i put them.

There was a Strad poster for it in 1986.

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Since slab cut wood is not as strong as quartersawn wood of the same dimensions, I'd PRESUME that a slab cut back would be thicker than a quartersawn back in order to achieve the same level of strength. How much thicker? I'd GUESS about 20 percent.

Chris

Hi,

20% thicker would also make the back 20% heavier. As far a strenght is concerned, the properties of the wood are different. A slab-cut back is more elastic and the quarter cut stiffer but not stronger.

Perhaps one chooses a slab-cut back for a softer, darker sound. Making the back thicker would defeat the purpose.

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Would not the amount of variation in stiffness in quarter cut backs overlap the slab backs?

Wood being a natural product, connected to a varying environment, varies quite a bit.

The stiffness relates to the internal structure of the wood. Imagine bending a 4x3 towards the 4" and towards the 3" The reeding inside the wood is similar. The quarter sawn has the 3" on top, the slab cut the 4".

The shape of the reeding varies from species to species, from tree to tree, and from one part of the tree to another. Apart from that tension and compression wood differs from the even growth!

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This is a little off the topic but, speaking as a violist I'd say lighter weight is better than heavier weight for player comfort and even player health. Violists have the highest injury rate among string instrument players and weight of the instrument along with length are important factors related to injuries.

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Thanks all for your idea's, insights and concern.

I agree that the weight for a viola is a critical issue. And I have been paying attention to that. But what is a typical weight for a viola top and back ? So far, my top is at 86 gr (f-holes cut but the bass bar is not in yet) and the back is at 135gr. For a 16 1/4 inches viola is that OK ? This is my first viola so I am making a lot of assumptions from data I find here and there. And notably from this document: Making Violas: Reconciling Size and Sound

I stopped carving the back, as it felt flexible enough, the weight seems to be right and the mode 5 is close to the one on the top. Even if it is thicker than I would have left it. But I am taking into account the fact that the density of this maple was .49 which is quite light compared to the other maples I am used to work with. This low density can explain the thicker plate with a lower weight.

-Tom

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