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Greg Sigworth

Plowden violin top graduation

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On the Strad poster for the Plowden Violin from which I have just made an inside mold I noticed in the graduation mapping for the top that in the upper and lower bouts in the region of the bass bar that the plates were thinner. What I also noticed from the CT scans of the plates and the corresponding line drawings and CT scans of the archings was that these areas appear to have been thinned from the top of the plate not from the inside. The inside of the plate has a smooth curve form, but the top is a bit concave in these areas. Did Guarnarius assemble the instrument in the white, play it, and then selectively thin the top from the outside to enhance the sound and then finish the instrument with ground/varnish? Any thoughts on this. I plan on making two violins from the Plowden mold I have made from this poster.

Edited by Greg Sigworth
Spelling error, and again, sorry.

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12 hours ago, Greg Sigworth said:

How do I get it approved by a moderator?

You wait till I review the posts.  

New members are subject to having their first 10 posts reviewed before they are approved.  This is an unfortunate result of spam and trolling.

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I'm by no means an expert, but I'd imagine after a couple hundred years the top no longer has its original shape due to its overall age and being reworked/patched multiple times. It's much easier to patch/graduate the inside to appear smooth than the top, where you have the finish to contend with. Myself, I wouldn't read too much into how the top was originally worked by what the instrument looks like today.

Having said that, I am interested in how makers go about adjusting the plates of an instrument in the white after closing the box in order to adjust its sound. 

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Maybe some folks who know the history of the Plowden can say something more certain, but 1) There is so much distortion that I wouldn't try to guess what was the original surface, 2) Those very thin graduations don't seem like something GdG would have done in the first place.

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Details on the Plowen can be found on the Strad3D project unfortunately my DVD won't run as it requires Firefox 2 ??.  The grads seem normal except for the bassbar area.  To my mind I think the bass bar has been replaced (original bars were much shorter) and this area might have been thinned in the process.  Just disregard this area.

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23 minutes ago, catnip said:

To my mind I think the bass bar has been replaced (original bars were much shorter) and this area might have been thinned in the process.  Just disregard this area.

and the replacement bar was replaced at least once, the 2011 Strad article mentions that. If you can get that article it is packed full of discussion about the graduations of both front and back, and much more.  you will find it helpful.

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I guess much of the deformation may be result of typical arch bulging. The bass bar makes the area stiffer and surrounding areas bulge out due to stresses in the top - that especially on relatively thin tops. Inside has been reworked probably quite a few times and that's why it is smoother.

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13 minutes ago, HoGo said:

The bass bar makes the area stiffer and surrounding areas bulge out due to stresses in the top - that especially on relatively thin tops. 

I think we're mostly looking at the cross arch distortion, where the bass bar doesn't directly have much of an effect, other than keeping the whole thing from caving in more on that side.

The bass bar is also not very tall; about 9mm max from what I measure, or 11mm including the top thickness.  And the top is relatively low density.  Thin, low-density top and a wimpy bass bar = lots of distortion.  I wouldn't copy all of that exactly, even if I wanted to copy the Plowden.  And I certainly wouldn't copy the distorted arching.

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Thank you for the comments. There appears to be other very good reasons the present distortion exists, both on the top and its absence on the inside. The top finds itself in compression longitudinaly and also being depressed in the area of the bridge. The upper and lower bouts could possibly bulge upward by this compression and the area in the bass bar would have extra support to resist this, resulting in the upward bugled  surface in the two bout regions when seen against the bass bar supported area. The inside having been reworked at least once would be smother. I think I said that right.

I made the inside mold from the line drawing of the back plate on the poster. The view appeared to be from the inside of the plate so I used only the bass side as the treble had wear on the upper treble corner where the hand rests in upper positions. I will try to include a picture of the mold and templates I made from the poster. The stop, mensur, is listed at 191mm. I noticed that the f holes show the treble about 1.5 to 2.0 mm farther down the instrument. When I correct this I should pick up a few mm for the stop.I plan on using the form for the plate shape but will try to make adjustments to increase the stop towards the 195mm standard in the placement of the F holes. I can't over state how dependent I have been to the free comments of other violin makers. I was not able to upload the image. Will have to work on that. 

 

Edited by Greg Sigworth
error in stop number

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On March 1, 31 Heisei at 11:50 PM, Don Noon said:

Maybe some folks who know the history of the Plowden can say something more certain, but 1) There is so much distortion that I wouldn't try to guess what was the original surface, 2) Those very thin graduations don't seem like something GdG would have done in the first place.

I have seen the Plowden once 20 years ago. Stunning instrument and my overall impression was that it was in pretty mint condition.

If we are talking about deformations in the arching, I am not quite sure any more if GdG built symmetrical archings from the beginning. So it is a kind of vague guesswork what is deformation and what was made from the beginning. 

From restoring I can only say that deformations by age are mostly on a macro pattern except the deformation under the bridge feet. So with the bass bar I would expect the whole bass bar side tilting down. 

There is on most GDG after maybe 1735 a sort of dipped in area under the bass side f hole which I suspect to be original. (For what reason ever) On the Leduc it is so extreme that it takes some guts to copy it. But trusting the audacious experiments by @Evan Smith arching can be pretty deformed and still sound good. 

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A while ago I took the CT scan of the upper corner crossarch and flipped it around to show how distorted it is.  I don't think any violinmaker (with any pride at all) would build them new this way, and it is the kind of distortion you'd expect with creep under load.

2030258847_Plowdenuppercornersymmetry.jpg.cabd7413f17e7731e27a707acc8ca638.jpg

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There's a possibility that the distorted arch sounds better than a symmetrical one.  So the maker has a choice of making it sound good now or waiting a few hundred years of creep before it sounds good.

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Don, I'm not so sure that all of that is creep.  I think that much of it was already there from the beginning.  We know that Del Gesu was experimenting, just like Evan.   What's wrong with having a tight stiff curve on the treble side, and a looser, more flexible curve on the bass side that could more easily drive the body?

I start mine on the inside, and purposely set the inside off to the treble side.  I tried to make it thicker there, and thinner on the bass side.  Not much, but some.  I don't think I went as thin as the poster, but I don't know about the edges because I do them after it is glued together.  I didn't check the countour on the outside, but I just did, just above the outside f notch.  

It isn't as drastic as the poster, and no one noticed at the MVA meeting.  At least they were kind enough not to call me a crazy lunatic to my face.  I've been called worse.  

20190303_095736.thumb.jpeg.f8adeaded58ccab4227baa1ff81db365.jpeg

 

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One way of generating the cross arches is to use a hanging chain (cantoid).  If the chain's end support points are level you get symmetrical arch.  If one support point is higher you can get a smooth asymmetrical arch which is flatter on one side and more bowed on the other similar to the Plowden's arch. 

The amount of difference between the end support heights determines the amount of asymmetry.

If one leg is longer than the other there's a tendency to walk around in circles.

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Yes. It isn't just an offset arch. The center is offset, but the curve is wider on the bass side than the treble side.  I never thought about how I was holding the chain, just about how it was getting to the points I wanted it to get to.

I just tried it with the arches I drew.  It works just as Marty said.  He knows more about what I'm doing than I know.  I am clueless.

Ken

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On 3/2/2019 at 12:02 AM, Greg Sigworth said:

I made the inside mold from the line drawing of the back plate on the poster. The view appeared to be from the inside of the plate so I used only the bass side as the treble had wear on the upper treble corner where the hand rests in upper positions.

If I remember correctly the Plowden poster includes the CT scan of the ribs taken at the level of the form.  I think this is a very precious information, how come you did not use this for your form? 

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2 hours ago, Ken_N said:

Don, I'm not so sure that all of that is creep. 

I don't think anyone can be 100% sure, but it does happen to conform quite nicely to the typical creep scenario.

Tops are so flexible, and most from the 17th century have been "re-arched" so many times, that I would be reluctant to take anything we see today as representing the original, or the original intent.

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The line drawing of the back I refered to that I made the inside form from was the back plate shape. I then used the method in The Best Of Trade Secrets volumn One by John Dilworth to make the mold. First patern of half plate, then second patern inside this for overhang and ribs thickness which put me at form edge. A lot of work when you have the CT scan of that form, but not sharp image. I never thought of using the CT scans images to make the mold. The CT scans were fuzzy at the edges and did not have a sharp border to follow, but a good idea though.

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The Plowden top is very asymmetric. The punctum maximum is in the breast area but it continues very far into the bouts. The cross arches in the bouts are fuller than the rest of the cross arches. The back isn't nearly as distorted as the top. The treble  f hole is a lot more opened in the side view than the bass side, where the edges of the f hole are hardly visible.

It has a breast patch which indicates that maybe someone already thought there is a strong distortion going on. 

A few thoughts and questions:

1. If the intentional asymmetry would be that important for sound, why dG should leave this concept? (For example cannone: healthy grads, almost no distortion).

2. The top is not randomly asymmetric but rather exactly in the way I would expect it for a distortion, especially the fuller bout cross arches.

3. If it was by intention, why isn't the back comparable asymmetric as well?

4. That shape of arch is less efficient when it goes to strength. I would expect the thicknesses to compensate for that, which they don't. (Of course there is the regraduation bias). 

5. What reason would I have to make the bass side more straight and the treble more curvy?  I  Don't think there are a lot of people who believe that certain areas of the plate are responsible for certain strings. 

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5 hours ago, Davide Sora said:

If I remember correctly the Plowden poster includes the CT scan of the ribs taken at the level of the form.  I think this is a very precious information, how come you did not use this for your form? 

The ribs on the Plowden have a very strong belly in the center area between the linings. Taking these as an outline would lead to a larger instrument than it actually is. At least that was the reason why I didn't use the CT rib scan for my mould.

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I have a "European" fiddle probably from early/mid 19th that has the same arch "distortion/asymmetry".... also has belly and back SP patches and crack repair.

I always assumed that the distortion was probably due to the repairs and a too long SP for too many years....

Its body measurements are very close to the Plowden...... can't imagine some Mitt/Mark/Shoen/Mira.... shop or maker of the era would copy the distortions of a DG...... if the Plowden was even as distorted 200+/-  years ago....

Just called mine Quasimodo..... and keep playing it.

BTW.. the asymmetric arch does make cutting/fitting a bridge for it a Real Treat.

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On 3/3/2019 at 6:56 AM, Andreas Preuss said:

There is on most GDG after maybe 1735 a sort of dipped in area under the bass side f hole which I suspect to be original. (For what reason ever) On the Leduc it is so extreme that it takes some guts to copy it. But trusting the audacious experiments by @Evan Smith arching can be pretty deformed and still sound good. 

Hi Andreas  !

Yes sir !  audacious should about  cover it!

Maybe a bit foolish, pig headed, stubborn, I'll take all compliments,,,,

I have made about a half dozen with the bass side very flat, like the Le Duc,  Top and back plates the same. The soundpost as the highest point, top and back.

They all found homes rather quickly, good players. Then I made a half a dozen with the bass bar as the highest part, top and back. They worked fine as well, none of them are hanging around, maybe wish they were. I will say that I had a retired concert master to tell me if my fiddles were worth a hoot, and they loved to tell me they weren't, so when they gave the go ahead it meant something.

Now I go for symmetrical as the mental capacities allow,,,,

 

 

 

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