Hi everyone! I'm new on this forum and i'm happy to have the possibility to discuss with other people with the same passion about violin making. I have a personal approach with the liutherie so basically I consider the thicknesses and the external arching like pure consequence of the inner surface ,that's the most important area because the phenomenal of reflections take place there (the arching are working like a concave mirror)and we can project the inner geometry for creating armonical frequencies(that's my idea).
Thicknesses are a fake friend cause every piece of wood (also took from the same tree)has specific properties and also we can change the properties in the way we work it...there are very small things in the cellula that in italian are called " microfibrille" ,they have directional properties and they have an angle with the axis,more this angle is close to be parallel and more the wood will be flexible and we cn change that angle in the way we work the wood. For this I don't consider thicknesses and external arching when I make a project. It seems that old liuthers used this tecnique of projecting the inner surface first. Till the beginning of 700' makers used same inner curvature for the top and the back,then stradivari changed the curvature of the back,he made the radius bigger(ratio about 9/8) in that way he avoid that the raies coming with an angle bigger than 40 degrees(on the curvature of the back) went more down than the focal point. We have to consider the focal point when we want to find the size of the ribs cause we want the innersurface of the plate to be on the precise focal point(that is not a point but a circle) for having the reflection with the maximum power. Than he made another changement on the longitudinal axis,he made a downhill on the central area(between p40 and p26) on an angle of 10 degrees witn an excursion of around 0,7mm,for this reason his violins have the ribs shorter close to the neck than to the botton ,because he had to do it to make the surface on the central area parallel. That's just something that I would like to talk with you.
Violin project
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Alessandro Defa
Re: Violin project
I forgot to say that before stradivari's system the liuthers put the innersurface of each place on the focal point thats around 1/36 less than half of the radius, but steadivarichanging the curvature of the back had the focal point of the back more up than the surface of the belly but making this chabgement he got multiple reflections! I imagine it 's not easy to understand like this , maybe is better to see photos or video...if somebody want I can do it