Violin Forum/Message Board

[ctviolin]

I'm curious who is willing to talk about what shape they use for their long arches?

Do you use a standard arch shape?
Follow a poster?
Is every one different?
How close are the top and the back arch shape?
Does anyone else put the apex of the belly under the bridge and the apex of the back dead center?
Etc?

[Michael Darnton]

I use a circle for the back. A friend who's a well-known maker disagreed, telling me that a catenary fit all the del Gesus in the Biddulph book. I drew him out, on the computer, a circle against a catenary. They were exactly the same over that distance with that (minimal) curvature. I'd sort of expected that, but not to that extent. You can check that yourself: http://darntonviolins.com/images2/allcurves.jpg

For the top, I use a flatter circle between the widest parts of the bouts, then get down to the ends gracefully. The highest points of the top and back, both, are at the midpoint.

I extract as much data as I can from the poster and pictures, then try to fill in the blanks and generally straighten things out.

[kubasa]

Michael, that is a fantastic image. Thank you for sharing this. To a visual learner like myself, this is a big help.

[Dave Chandler]

I found a site somewhere that had a catenary curve formula in a program where you simply plugged in the length and height you wanted at apex, and it drew it out for you in full size so you could print it out from your computer. I hated math in high school, so any formula more complicated than a+b and my eyes start to glaze over. Darned if I didn't lose that "program" last time I cleaned out all my extraneous files.

Does anyone know where to find it? It REALLY was helpful.

I also took one of those laser level devices, and in a dark room, with the laser "locked" rather than free floating, moved the laser line up and down the center of the back, and you could really see very well whether you had a symetrical curve on either side of the center of the back/front at any point. Really cool.
_________________
Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo

[Mark Sullivan]

Here is a link to a Curtate Cycloid generator.

http://www.cgl.uwaterloo.ca/~smann/ccycloid/

[Dave Chandler]

Great, that's the one I was looking for. Its on my desktop now.
_________________
Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo

[L P Reedy]

[Michael Darnton]

Dave, don't just go for the numbers you need: play with the extremes. Some interesting things happen at the extremes that are also mimicked in Cremonese archings. For instance, higher and narrower = less, tighter scoop, wider convexity in the center. You can see how this develops if you go to the extremes. The cool thing is that Cremonese arches do this, too, exactly as the cycloid would predict.

[CT Dolan]

I have mentioned this elsewhere before, but one thing that intuiges me is the manner in which the long arch in the belly of the violins of Stradivari and del Gesu (as if these guys are the only two who made violins before, but I digress...) lacks the flat area near the bridge. Actually, with regard to del Gesu it almost appears as though this flat area diminishes over time, disappearing altogether late in his career (but I may be wrong with regard to the "diminishing" aspect and need to spend more time studying those for which I do have information). Anyway, intruiging stuff. Not sure what to make of it yet, but it is intgruiging nonetheless.

By the way, ever hear the ex-Leduc del Gesu of 1745? Buy Szeryng playing the Bach S&P's and you'll hear one very, very fine violin in the Leduc. I guarantee it will have you wanting to attempt to reproduce that same gorgeous tone, graceful long arch in the belly and all.

[ctviolin]

[Michael Darnton]

Think of the violin as a designed object, not a logical object. :-)

I was just reading the notebooks of Leonardo da Vinci. He proposed a system for moving rivers uphill by a system of locks combined with siphons to move the water upwards (think about that one for a minute). He also suggested that the continuation of the sound of a bell might be because the bell continues to vibrate after it was struck. There were other things in the book that remind me that the average 5th grader of today might know more about science than Leonardo did. If he was the one who designed the violin, as some have suggested, the smartest man of his time certainly wasn't looking at it the same way we do!

[ed s]

Craig - just some more food for thought, you may want to check out this web
site http.//www.kcstrings.com/anton-krutz-geometry.html you may have
seen this before, in case you havn't he describes in condensed form how he
develops the top and bottom plate arch.

[Mikes]

"]I use a circle for the back. A friend who's a well-known maker disagreed, telling me that a catenary fit all the del Gesus in the Biddulph book. I drew him out, on the computer, a circle against a catenary. They were exactly the same over that distance with that (minimal) curvature. I'd sort of expected that, but not to that extent. You can check that yourself: http://darntonviolins.com/images2/allcurves.jpg"

Michael, In your drawing I see that you drew in the 1 and 5 cross arches, in application would you expect the long arch curve to run thru those points? Or would you adapt the long arch curve to the cross arch points?

[Michael Darnton]

I adapt the long arch to fit those templates, more or less. Obviously if you tip them up on the inside, until they merge with the circle, there won't be a step as there is in the illustration. I use half-templates in those areas.

[MANFIO]

Michael, my approach is the same of yours. But some makers also use a circle for the top for some models, but I find it too rigid for the top, what's your opinion about that?
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