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Plate graduations
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=25203		 Page 1 of 1
Author:  the Padma [ Mon Dec 28, 2009 1:16 pm ]
Post subject:  Plate graduations
Apparently a Jeffrey S. Loen has published work that provides hard evidence that that (60%) of the studied plates the Cremonese masters, were thinner, not thicker, in the center than at their edges.

Apparently only a handful of the plates examined were thicker in the center of the arch.

Also that irregular and non symmetrical arching on most plates was common.

This has some heavy implications for the violin family and Archtop guitar builders as well as arch tops are basically an extension of the violin top in design concept.

So the question is....

Does anybody have any info to share on this?

Drawings, numbers, scantlings would be really neat to see.


thank you

the
Padma
Author:  truckjohn [ Mon Dec 28, 2009 3:11 pm ]
Post subject:  Re: Plate graduations
I believe Al Carruth has mentioned the same thing several times....
Common knowledge and practice in apprentice training was that the plates were thicker in the center and thinner at the edges.... but apparently no one bothered to measure and verify...

Until someone finally did... and found that the good ones were mostly thinner in the middle!

It was probably one of those "Secrets" -- you couldn't just let anyone make great instruments Willy Nilly... so you taught folks to do it "The wrong way"... till the Master finally gave up the secret to his oldest and most trusted son on his death bed or some such...

My guess is that it is very easy to teach people to thin plates around the perimeter (You can look at the edge and see how you are doing!)... and more difficult to teach them to thin them in the center (How will you know how thin it is?)....

And after spending a year as a school teacher.. I know this 1 thing... One reason that certain things are taught is that they are easy to teach.. not because they are either Absolutely Right or Useful!

Thanks

John
Author:  Haans [ Mon Dec 28, 2009 4:30 pm ]
Post subject:  Re: Plate graduations
the, good question. I do know this. Mandolin family instruments are thinned a bit in the center between the feet of the bridge. How much? idunno Depends. I've seen many good and expensive mandolins that were thinned a bit too much and there ended up a bulge between the feet. Gibson H-5 mandolas are famous for that. I've seen a good number of "modern high buck" (I'm not going to name anyone here) with the bulge also.
The other thing that happens is a slight "caving in" of the top if you go too far.
I've made plenty of VG mandolins both with and without thinning in the middle. I've also made them very thick, but never have gone over to the thin side. Thin mandolins sound thin, thick mandolins sound FAT. I suspect the same holds true for archtop guitars.
How thick is thick and how thin is thin? Don't know about guitars, but mandolins... oops_sign All my fingers broke. laughing6-hehe
Author:  Alan Carruth [ Mon Dec 28, 2009 4:56 pm ]
Post subject:  Re: Plate graduations
This info has been floating around for a while: I remember discussing it at the NVFA Convention in '05. What's most interesting to me is that 'reverse graduation' seems to go with 'curtate cycloid' arches, and seems to have started with Nicolo Amati. There are a couple of other arching schemes, and they each seem to have their own graduation system. It makes sense; both the arching and graduation are ways of controlling the distribution of stiffness and mass in the plate, and that's where the sound really comes from. It seems to work best when they work together.

Right after I heard about this stuff I made my 'Winter' archtop, using CC arches and a uniform top thickness (I chickened out at making the center thinner, and, besides, the #5 mode was already low enough). So far nobody has complained about the sound. I've used that scheme an all of may arched instruments since, both guitars and fiddles, and I'm quite happy with the results.

There is some data suggesting that reverse graduations tend to lower the pitch of the 'bridge hill' resonance on violins, keeping it out of the 'irritating' range.
Author:  the Padma [ Mon Dec 28, 2009 6:04 pm ]
Post subject:  Re: Plate graduations
Alan Carruth wrote:
This info has been floating around for a while.... 'curtate cycloid' arches, Nicolo Amati......


Haans wrote:
... thinned a bit in the center between the feet of the bridge.....


Thank you dudes...."cycloid arches" ... and ....that scoop between the feet. Here me thought that Jeffrey S. Loen dude was into something new.

Yes Alan, Haans, thank you for posting and saving me a lotta time running down this great "secret" that Loen "discovered"

I owe you dudes one.


blessings
the
Padma
Author:  Alan Carruth [ Tue Dec 29, 2009 2:02 pm ]
Post subject:  Re: Plate graduations
Loen is the source for a lot of that data; he's just been at it for several years. He's a cartographer by trade, and has lots of maopping software. He and several other folks have been going around to museums and collections gathering data on archings and graduations, that he then feeds into his software. Once it's mapped up it's easy to look for common threads. This is the result both of a more open attitude in the violin making community, and the availability of the processsor power to make use of the reams of data.
Author:  woody b [ Tue Dec 29, 2009 3:45 pm ]
Post subject:  Re: Plate graduations
Quote:
were thinner, not thicker, in the center than at their edges.



Kinda like scalloping braces on a steel string wow7-eyes
Author:  the Padma [ Tue Dec 29, 2009 4:19 pm ]
Post subject:  Re: Plate graduations
Thank you Alan for bringing me up to speed on Jeffrey S. Loen.

Although me knew about cycloid arches, My first searches didn't come up with anything about him. So me didn't put the 2 of them together.

Now that I know, guess me gonna take a look into just what him finding.



Gonna digress here.

Is accepted that the "masters" of the past used maths, mainly Golden section and Fibionach as thats what the consciouness of Europe was into exploring at the time.
Here it is a few hundred years later, the consciousness of the planet is now into "exploring consciouness expansion" ~ the finding and taping into ones own intution.

Now is pritty well known fact that me don't use calipers and often don't bother with drawings or even a sketch, when me build. Much prefer to go with the flow, the feeling of the woods thickness between me fingers and whats in me gut. I know there are a few other dudes building like this and no you won't be finding them on OFL or Luthierforum or Luthiercom or at NAM or Heidelberg or the Montrea shows...but
me can't help but wonder if this type of building just be a by product of the '60s or if in a few hundred years form now dudes like Loen gonna be tryin to figure out how we arched tops, or braced it thata way or did what we did do....thats of course if the consciousness of this plane gets it together to survive and evovle in to a sustanable future.

Just another one of them oh wells me sometime wonder about.

Thank you for reading me babble Alan.


blessings
the
Padma
Author:  LanceK [ Tue Dec 29, 2009 4:27 pm ]
Post subject:  Re: Plate graduations
woody b wrote:
Quote:
were thinner, not thicker, in the center than at their edges.



Kinda like scalloping braces on a steel string wow7-eyes


Thanks Woody, my thoughts exactly!
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