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Wood Butcher

Stradivari scroll compass method

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I’ve seen pictures of the templates for marking out the back of the scroll in the Sacconi book, so I understand the principle of how it works.

I have never seen anywhere information on how it is generated.
Does anyone know the position of the compass locations? Presumably the chin is the starting point, and it works from there. How do you work out the changing distances between the points, and how to work out the widths of the circles for a violin scroll?
 

Any help is appreciated.

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Get a violin scroll, measure the widths every few cm, and draw it out. adjust if you want and take note of the widths at the apex and trough of any curves. Since you can get most of these width measurements from nice fiddles already, from online or Strad posters, books, etc., make a template and then decide how you're gonna do it the next time.

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Somewhere on MN there is a picture or PDF from Addie I think.  It shows the diameter of each circle and the distance from the previous circle.  I'm going to need that soon too so I'll post it if I can find it.  

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4 hours ago, Wood Butcher said:

I’ve seen pictures of the templates for marking out the back of the scroll in the Sacconi book, so I understand the principle of how it works.

I have never seen anywhere information on how it is generated.
Does anyone know the position of the compass locations? Presumably the chin is the starting point, and it works from there. How do you work out the changing distances between the points, and how to work out the widths of the circles for a violin scroll?
 

Any help is appreciated.

I tried to understand what relationship there could be in the positioning of the centers and measures of the circles in the Stradivarian drawings for the back of the scroll, but without success. I concluded that there was no particular geometric or proportional relationship, just a simple system of making measures. But of course, I can be wrong, although to my consolation, it does not seem that any of the experts and scholars of these aspects have managed to find it in a credible way either. So I found my own system for positioning them that had a logic and was adaptable to any scroll size, somehow consistent with the compass marks visible on the original instruments and drawings. You can see it in this video :

I am convinced that the work was done by eye, obtaining the measurements from previous scroll and using the marks mainly to speed up the roughing work. In fact, the measurements of the circles found on the Stradivari's paper drawings (only for viola and cello, those for violins are missing) are always wider than those of the real scrolls, indicating that the arches of the compass were systematically removed, and once you remove a marks it means that you let yourself be guided by the eye, not by the marks themselves.

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The full compass work for a scroll is complicated, and includes the pegbox.

It's also sort of organized in frames.  

Think of a frame around the outer volute, in old Cremona work this is generally a 3 by 4 or a 4 by 5.   

I'll try to post more soon. Maybe tomorrow.

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1 hour ago, David Beard said:

The full compass work for a scroll is complicated, and includes the pegbox.

It's also sort of organized in frames.  

Think of a frame around the outer volute, in old Cremona work this is generally a 3 by 4 or a 4 by 5.   

I'll try to post more soon. Maybe tomorrow.

Did you find any correspondence with these drawings? (see image in the previous post)

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I find that logical points along the back of the scroll seem to have proportional relationship with the main box width.

But I've not tried to look at these issues in that template.

(Do you perhaps have a good flat on picture of that template?)

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Thanks for all of the replies.

I had assumed that the sequence of circles was somehow generated mathematically or proportionally. I did not consider that maybe Stradivari just chose a scroll he had finished, and used this to make the pattern from.

It's interesting to read Davide's point that the marks are wider than the scrolls themselves. I had been thinking these were the final measure, but it seems the circles are actually the line to cut to when roughing out.

From your help I now understand better what is going on, and will take the advice to transfer some measurements from an existing scroll, and make my own series of circles to replicate it.

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12 hours ago, David Beard said:

I find that logical points along the back of the scroll seem to have proportional relationship with the main box width.

But I've not tried to look at these issues in that template.

(Do you perhaps have a good flat on picture of that template?)

I have no better images, sorry. I got it with a screenshot from the cd attached to the museum artifacts catalog.
But it seems to me that it is flat and not bad at all.

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16 hours ago, Davide Sora said:

If you can pull a Fibonacci sequence out of here, I'd be happy to learn:)

1144711422_DorsocelloBms277.thumb.jpg.11c85812a0bf1df5812d061f45cc2baa.jpg

what do you think is the purpose of the markings on the right side of it?  looks like small arcs of a circle,  some dots,  and straight lines.  

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22 minutes ago, MikeC said:

what do you think is the purpose of the markings on the right side of it?  looks like small arcs of a circle,  some dots,  and straight lines.  

I think these are the shoulder widths and diameter of the chin for a cello scroll.

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3 hours ago, Wood Butcher said:

I think these are the shoulder widths and diameter of the chin for a cello scroll.

Yep, the circles refer to the volute, the pegbox lenght is not marked except the end with the widths of the jaws. This is one of the reasons that leads me to think that the beginning of the volute is aligned with llower part of the volute, without geometric relationships with the length of the box. The complete drawing would look like this for Contralto Viola:

1589290198_DorsoCV.thumb.jpg.a7e3db429b7874e8b0118af3a5377ea2.jpg

Maybe the distance between the small dots on the centerline could be correlated with the measuring unit?:)

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On November 9, 2020 at 9:54 PM, Wood Butcher said:

Any help is appreciated.

I couldn't figure out anything either so I started to look on good photographs of Strad scrolls. 

What I found quite remarkable is what I pictured below. 

The design of the peg box and the back of the scroll seems to come from only two plane surfaces . (Marked in green and red) the angle between both is almost always invariably 172 degrees (maybe a pinch more) 

It is usually rounded off as indicated by the purple colored line in the left. 

However, this does not appear in the paper design which is a complete riddle to me.

 

image.jpeg

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39 minutes ago, Andreas Preuss said:

I couldn't figure out anything either so I started to look on good photographs of Strad scrolls. 

What I found quite remarkable is what I pictured below. 

The design of the peg box and the back of the scroll seems to come from only two plane surfaces . (Marked in green and red) the angle between both is almost always invariably 172 degrees (maybe a pinch more) 

It is usually rounded off as indicated by the purple colored line in the left. 

However, this does not appear in the paper design which is a complete riddle to me.

 

image.jpeg

Andreas, my impression is that the "two planes" do not usually appear from the straight-on rear view, the view in your drawing. But that the "red" plane is quite evident when a radial view (looking toward the eye of the scroll) scroll is maintained as the scroll is rotated.

But perhaps that's only true of the particular Strad scrolls I happen favor, and others have escaped my memory because I didn't like them as much. :D

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1 hour ago, Andreas Preuss said:

I couldn't figure out anything either so I started to look on good photographs of Strad scrolls. 

What I found quite remarkable is what I pictured below. 

The design of the peg box and the back of the scroll seems to come from only two plane surfaces . (Marked in green and red) the angle between both is almost always invariably 172 degrees (maybe a pinch more) 

It is usually rounded off as indicated by the purple colored line in the left. 

However, this does not appear in the paper design which is a complete riddle to me.

 

image.jpeg

It seems to me instead that this aspect comes out naturally using the Stradivarian tracing system, where the straight lines of the pegbox necessarily form a well-defined angle at that point, more or less evident depending on the amount of the next blending you want to make. The wider the pegbox, the more evident this typical "angularity". Compared to Amatis, Stradivari has greatly widened the pegbox to create more space for the string on the A peg, inevitably creating this angularity, putting functionality above aesthetics (Amati pegboxes are much more elegant and flowing at this point, in fact).

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3 hours ago, Davide Sora said:

It seems to me instead that this aspect comes out naturally using the Stradivarian tracing system, where the straight lines of the pegbox necessarily form a well-defined angle at that point, more or less evident depending on the amount of the next blending you want to make. The wider the pegbox, the more evident this typical "angularity". Compared to Amatis, Stradivari has greatly widened the pegbox to create more space for the string on the A peg, inevitably creating this angularity, putting functionality above aesthetics (Amati pegboxes are much more elegant and flowing at this point, in fact).

I rather like the form of the Amati pegboxes, without that notchey stuff. With modern strings (lower diameter than gut), I haven't found much of a problem going in that direction.

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Remember, in the width and shape of the pegbox, front and back, Strad was rather innovative.  The old Amati traditon are based on straight lines to a greater extent.

I suspect that both practices used circles set widths.  And both used proportion from other features to set the size if some of these width circle.  (Mostly from main box width or from features from the volute.)  But then made more width circles as 'a part less'.  So you set one or two initial circles, then make more that each reduce by 1/4, 1/5, or 1/6.

But where the practices differ is in their aim, and placement of guide circles.  Strad, and later Deg Gesu, aim to retain width on the box closer longer as you move toward the scroll.

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1 hour ago, David Burgess said:

I rather like the form of the Amati pegboxes, without that notchey stuff. With modern strings (lower diameter than gut), I haven't found much of a problem going in that direction.

Me too, I always tend to remove too much (compared to the stradivarian measures) by cutting away the circle that determines the end of the pegbox, going in a more Amatisè direction, but not too much.

My eye dictates over geometry, I can't resist.;)

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On 11/9/2020 at 8:02 PM, Davide Sora said:

If you can pull a Fibonacci sequence out of here, I'd be happy to learn:)

1144711422_DorsocelloBms277.thumb.jpg.11c85812a0bf1df5812d061f45cc2baa.jpg

I see simple linear progresion from widest part to the narrowest. Those circles are on equidistant centers and you can connect the "widest" points of all the circles with straight line thus the diameters (or radiuses decrease linearly - in arithmetic progression by same amount from one to the next). This would dictate more or less straight pegbox walls up to the start of the curve of scroll which causes the somewhat abrupt angled change of planes. Then from the narrowest point the widths increase again on equidistant centers (the distance changes here because the curvature of scroll tightens as well) though not perfectly in line (perhas to keep the start of upper turn of scroll aligned with the bottom angled plane). I see no intentional ratios or similar relations anywhere in this drawing.

I think Hargrave (in one of his articles?) noted that Amati carved violin scrolls graceful like this but Strad broke this rule on violins and widened his scrolls at the a string (perhaps because of thick strings as noted above).

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42 minutes ago, Davide Sora said:

Me too, I always tend to remove too much (compared to the stradivarian measures) by cutting away the circle that determines the end of the pegbox, going in a more Amatisè direction, but not too much.

My eye dictates over geometry, I can't resist.;)

Same here.

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17 hours ago, David Burgess said:

I rather like the form of the Amati pegboxes, without that notchey stuff. With modern strings (lower diameter than gut), I haven't found much of a problem going in that direction.

I totally agree. Amatis scrolls and the form of the pegboxes are much more refined, and a sort of reflecting the aesthetics of nature.

What intrigues me about Strad is the following. Before 1700 - 1705 you have a sort of different models or you may call it development, and then it stops and the oval shaped volutes repeat in hundreds of minimal variations together with the typical peg box.

Two years ago I analyzed with the help of an intern the proportions of the volute and we found that in horizontal and vertical direction there is nothing really consistent BUT in both 45 degree directions measurements follow very precise proportions with minimal variations in measurements. And  this in a span of over 30 years. Made me think.

 

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