Violin Forum/Message Board

Cliff Green · Posted: Thu Oct 25, 2012 9:57 am Post subject: Arching

Michael, in the past you have been a proponent for using curate cycloids for to design the cross arching. How do you develop the long arches? My earlier violins had a flatter section thru the center area but of late I have been using the same curate cycloid for the ends of the long arch as used in the widest portion of the upper and lower bouts and a gentle curve in the center section with a high point near or just north of the bridge.

Also, in a recent post you commented that you had the best power with top arching of 16-18 mm. Do you compensate the back long arch perhaps to match the combined arches to your magic number, 32mm?

Michael Darnton · Posted: Thu Oct 25, 2012 11:35 am Post subject:

I usually make the back and top about the same height. I realize that I'm not doing something that's strictly traditional by my 32 definition, in that sometimes the total is pretty big, but it's what works for me. I may compensate with rib height--I'm always experimenting.

My back long arch is a simple circle, and the top is slightly flattened in the middle. Any system you use that has a circle for the long arch involves some song and dance at the ends, because a circle has no recurve, and I simply try to handle that gracefully, sometimes using half templates swung around through the upper and lower blocks, as I think you're indicating you do.

From my measurements on real instruments, it's very clear that the long arches are derived from circles, one way or another. This has a tonal effect, but not as large as what you do with cross arches.
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kubasa · Member Joined: 13 Sep 2007 Posts: 212

Michael, what do you mean when you say you may compensate with rib height? Are you saying that if, for example, 30mm is the desired rib height and then if the ribs end up being 29mm, that you might add some height to the arching and vice-versa if the ribs were more than the desired number? I think this is what you are saying but I wanted to make sure. Sometimes I really dis-like being a visual person.....Thanks in advance for any clarifications on this.

James

Michael Darnton · Posted: Thu Oct 25, 2012 4:01 pm Post subject:

IfI know I'm making high arching, I'll trim the ribs a bit more. My ribs are always plenty high to start, so never the first case.
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kubasa · Member Joined: 13 Sep 2007 Posts: 212

Thanks Michael. I appreciate the insights that you share on this forum!

Michael Darnton · Posted: Sat Oct 27, 2012 8:48 pm Post subject:

This is just one example--I have lots; for instance you can see this same thing with the backs of many of the del Gesus in the Biddulph book. This photo is the Brothers Amati violino piccolo, but the rule applies to many Cremonese violins:

http://darntonviolins.com/images2/ForumPix/BrosAmatiVP-back-arch.jpg

The red line is a laser line on the back, and the green is simply a circle overlayed on the photo. I misaligned my green line a bit--otherwise it would perfectly cover the red one and you'd miss the comparison. You can see that they coincide for most of the back, just not at the ends where they really can't if there's going to be recurve and an edge. Given the age of the instrument and the potential for distortion through 400 years, the fit is remarkable.

I'm going to be a tease and say that I have a similar plan for the top, but it's something I reserve to teach at my summer workshop. Suffice it to say that it's definite and as clear as the concept above, and it wouldn't be too hard to work out for yourself from photos, as I did. Or, you can come to my summer workshop. :-)

Tonally, the strategy works so good that I have no interest in the theoretical criticisms of critics who haven't done their homework. :-)
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Cliff Green · Posted: Mon Oct 29, 2012 11:59 am Post subject:

Thanks Michael,

I've learned so much from you free that I guess it's about time I pony up for one of your courses. Do you have plans to offer your course on the East Coast?

Do you have any idea how the magic 32mm is derived? Multiples of 16mm give a lot values that are close to those I use.

Michael Darnton · Posted: Mon Oct 29, 2012 12:01 pm Post subject:

Beyond the fact that an arc of around 32mm or a bit less appears on almost all of the Stradivari forms, I don't know any other concrete source. I do know, however, that this measure began to be used around 1620 in the Amati family, coinciding with a change in Amati fs, for the placement of f-holes, so it dates back pretty far. I suspect it's something important in the original violin plan, whoever made that (Andrea Amati, or possibly someone previous to him, perhaps in Florence).

There could possibly be an East coast workshop some day, but in these days of cheap air fares via Southwest flying directly into Ontario airport, which is 10 miles from the workshop, I don't understand people's reluctance to just fly to California. Most of the attendees do, and I have people come from as far as Australia and Hong Kong.
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kubasa · Member Joined: 13 Sep 2007 Posts: 212

I finally broke down and purchased a laser level last year. I'm amazed at the things I can observe that I didn't necessarily see before. Thanks for the link to the photo.

I'd really would love to attend a course someday - after I get done with a few more years of paying for braces and kids activities and who knows what else related to parenting! I had a rather lengthy email conversation with Diane Gravlin from over at the fiddlehangout about the classes a while back. She's doing a good job promoting them as well. They really do sound top notch!