Violin Forum/Message Board

KenN · Posted: Wed Apr 23, 2008 6:34 pm Post subject: how thin is a viola belly

The belly for the Grancino viola I'm making is supposed to be 2.7mm max in the middle, 2.5mm max on the lower bout and 2.3mm max on the upper bout. Are these normal dimensions? The only other one I have dimensions for is the Amati on the luthier library site, and that is outrageously thick. I know Manfio said violas are thinner than violins proportionaly, but having the same thickness as a violin would make it 80% thinner. The back is 3mm max on the uppper and lower and maxes out at 7.4mm in the middle. It has the same kind of arching as the Maggini violin back. It seem like that stiff back could support a thinner belly.
Right now I have the thinnest parts at those numbers, and the edges and recurve are 1-2 thick. The belly is still heavy at 130g, but it does have a lot of stock on it.
I know viola makers don't have tap tones to shoot for but I was quite surprised to hear how high they still are. If I hold the lower corner I get 80, 199 and 263, and if I hold the upper corner I get 350 and 500. Don't know if they mean anything, but they sound nice!

MANFIO · Posted: Wed Apr 23, 2008 7:12 pm Post subject:

Hi! I'm using 3 mm, and I try not using less than that, even on the edges.

With the thicknesses you gave I found it too heavy at 130 grs, but I don't know your model, size and archings. Are you using European spruce? I find 1 and 2 milimeters too thin on the edge.

The 41.8 cms. viola I've just finished (and posted pics here) the numbers are the following

Table (European) without bar: 104 grs. tap tone D
Table with bar: 111 grs tap tone E
Back (red maple): 165 grs. tap tone C#

I was looking for more focus so I left my top giving an E, and it worked.

Some other successfull violas had this numbers:

table (European) without bar: 113.1 grs
table with bar: 122.7 - D
back (Bosnian Maple) D
soundbox total 369.9 This one is with Andrès Lepage, a professional with a big sound.

table (allways European) without bar 120 grs C#
table with bar 130.9 D
back (Bosnian Maple) 179.7 D
soundbox total 385 grs.

All that will vary with archings, model, wood, set up, etc. Good luck!
_________________
www.manfio.com

http://www.flickr.com/photos/7875988@N02/with/464604020/

KenN · Posted: Wed Apr 23, 2008 8:52 pm Post subject:

Thanks for the information. I'll file it away so I don't lose it.
The edges aren't 1-2 thick! They are 1-2 thicker than they will finish up.
I glue the plates on the ribs and finish the profile, purfling and recurve then. Kinda like the old masters did.... what a concept. I don't know what the plates end up sounding like, but I like to know where they start out. When I glue them on they lose their sound, but when I thin the recurve the sound comes back.
The belly is sitka spruce, not real light but it seems strong. I drew the plan up 418 long. It has low arches, only 17.5mm. It's small at the c bouts at 129mm, but the c bout is short so it seems wider. Here is a photo I hope. If I can get it to look like that!

[/img]http://www.flicr.com/photos/19584049@N08/2437791168/[/img]

KenN · Posted: Wed Apr 23, 2008 8:54 pm Post subject:

Oh well that didn't work. Where is a teenager when you need them.

KenN · Posted: Wed Apr 23, 2008 9:00 pm Post subject:

[img]http://www.flickr.com/photos/19584049@N08/2437791168[img][/img]

KenN · Posted: Wed Apr 23, 2008 9:01 pm Post subject:

yes I am pathetic.

violinarius · Member Joined: 14 Dec 2007 Posts: 171

http://www.flickr.com/photos/19584049@N08/2437791168

Works for me.

I just cut and paste the URL.

KenN · Posted: Sat Apr 26, 2008 2:39 pm Post subject:

Thanks. Don't know what I did wrong. This belly still seems pretty stiff for as thin as it is. The back is sycamore that seems pretty light in weight. Even with the thick center area maybe that will make up for the heavier belly.