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Marty Kasprzyk

Inflection points of polynomial cross arch shapes

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That idea is efficient if you make the shape from the strip.

My proposed approach is much easier for carving classical arching in the workshop.

It really couldn't be any easier. And it fits the historical evidence.  Why not consider my proposal? It does the job.

 

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On 10/24/2020 at 1:02 PM, David Beard said:

That idea is efficient if you make the shape from the strip.

My proposed approach is much easier for carving classical arching in the workshop.

It really couldn't be any easier. And it fits the historical evidence.  Why not consider my proposal? It does the job.

 

David, there are so many good ideas in your work.  Some has nice evidence in marks on old forms and such.  A couple of principles that keep showing up pose questions.  Perhaps you would consider weighing in on them.  

Circles.  The old masters used circles pretty much wherever they could.  Constructing outlines, constructing scrolls, ratio-making for everything.  I find that I see circles more easily than other shapes, and tools often form circles (e.g., rasping an edge).  We all like circles.    We can mechanically make circles (compasses, pieces of string, feel of a tool) and like to see circles (my observation).

While we have evidence for making circles as a method of generating some parts of the violin, I am unaware of any circle drawings or patterns for making the arching and channel, those dating from the original period of making.  Am I missing some evidence?

Another very key issue is in tooling.  Take the channel model you present, with different arcs for different sections.  I look at your drawings and immediately want to see a nice set of circular gouges of graded sizes keyed to rib height (let's take that, for example, as an inch, so the breakout into radii of fractions of an inch would be natural).  And a set of graded finishing scrapers of various radii.  These don't seem to be present.  Did I miss some?

Then add our tendency to like to see circles.  They would apparently like to see circles in design, and we like to find them in reverse engineering.  

And add in the fluctuations in manufacture, the wear and weathering, the imprecision of measurement.  

Given all the above, can we reject the hypothesis that the old time makers in Cremona made things that looked good to their eyes, and that because circles looked good they tended to scrape in circular sections that looked good, and that because of that we can find circles in arching, mainly the channels?   

I'm just having a hard time linking these nicely linked up conceptual systems with workshop practice in a busy shop.  Help me out.  I've got a plate.  The outline is designed with circles.  I thin it to about the arching height.  How do I decide this height?  Can I reject this height as simply being a half inch, more or less?  What do I do next?  I'm not trying to be difficult, I'm just trying to get this as simple as possible.  Set the edge height and start gouging?  When do I start measuring?  Is the longitudinal arch set from math, or is it a result of other decisions?  How do we prove that?

I'm not saying the various systems don't work, just that there's so much noise that any number of systems will work to get more or less into the window of what Cremonese arching sort of looks like.  So I'm looking at the tool set and trying to see how to get to that arching through a clear, simple, efficient sequence of operations with those tools and the other information.  We don't see templates or boards with cycloids marked out or boards that show the run-fall rule.  We do have scroll back widths worked out on a reference.  What else is there?  We have straight edges.  Did these play  into things?  Compass, straight edge, dividers.  A pile of sharp things to cut wood with.  How do you think this worked?

I'm reminded of the clove hitch.  There are all kinds of complicated ways to tie one, but it's a flick of the wrist to be performed very quickly when one jumps from the boat to the dock and has to secure that line RIGHT NOW.  There should really be a super simplifying principle, but I don't see it yet.

Thank you

 

 

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Interesting thoughts, Stephen. There are almost no spherical forms observable in nature, aside from the sun, and the moon (from time to time).  Both have been worshiped, perhaps because they were so uncommon?

The only exception I can immediately think of is waves propagating in a circular fashion when an object is tossed into a pond.   That may have been too common and easily attainable, to be worship-worthy.

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14 minutes ago, David Burgess said:

>

The only exception I can immediately think of is waves propagating in a circular fashion when an object is tossed into a pond.   

They only look like circles if you are looking straight down at the propagating waves.  Your idea is for the birds.

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24 minutes ago, David Burgess said:

Interesting thoughts, Stephen. There are almost no spherical forms observable in nature, aside from the sun, and the moon (from time to time).  Both have been worshiped, perhaps because they were so uncommon?

The only exception I can immediately think of is waves propagating in a circular fashion when an object is tossed into a pond.   That may have been too common and easily attainable, to be worship-worthy.

Circular forms show up a lot, in essence.  Tree growth.  Stalagmites.  Sun. Moon.  We built with circles so much.  

I carve things and I notice I like circles.  I look at great paintings and there are circles all over in faces and so on.  The basic shapes.  Squished maybe.  I had a funny late 17th C violin for a while, likely N. Italian.  Rather dishy, and extremely beat up.  The top looked like there was a beer can imbedded, with the arching draping over it.  I can't forget the obvious circles in it.  Kind of doubt a template of any kind was used.  This wasn't super crisp in any execution, but wasn't totally cringeworthy, either.  

I'm torn between the peace of an elegant system, with everything falling into place on paper, all the circles and lines and angles dancing - and the need for speed, to actually transfer idea into wood.  

 

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19 minutes ago, Stephen Perry said:

Circular forms show up a lot, in essence.  Tree growth.  Stalagmites.  Sun. Moon.  We built with circles so much.  

I carve things and I notice I like circles.  I look at great paintings and there are circles all over in faces and so on.  The basic shapes.  Squished maybe.  I had a funny late 17th C violin for a while, likely N. Italian.  Rather dishy, and extremely beat up.  The top looked like there was a beer can imbedded, with the arching draping over it.  I can't forget the obvious circles in it.  Kind of doubt a template of any kind was used.  This wasn't super crisp in any execution, but wasn't totally cringeworthy, either.  

I'm torn between the peace of an elegant system, with everything falling into place on paper, all the circles and lines and angles dancing - and the need for speed, to actually transfer idea into wood.  

 

You are using circular reasoning.

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The dividers make both cirles and proportions easy.  The center arch fall is governed by proportions but not circles.

The channel shapes from either side of the channel bottom are based on circles, sized by proportions.

You could potentially do these things by eye.  Our you can use dividers.

You could use a portion of scraoer you know be a good radius.  You could make an arc template from a scrap of wood.

You can draw the radius with and shape some pumice stone to it.  Use that to check.

I'm busy all today, so will respond more in the evening.

 

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1 hour ago, David Beard said:

The dividers make both cirles and proportions easy.  The center arch fall is governed by proportions but not circles.

The channel shapes from either side of the channel bottom are based on circles, sized by proportions.

You could potentially do these things by eye.  Our you can use dividers.

You could use a portion of scraoer you know be a good radius.  You could make an arc template from a scrap of wood.

You can draw the radius with and shape some pumice stone to it.  Use that to check.

I'm busy all today, so will respond more in the evening.

 

Thanks.  I'm not trying to be confrontational at all.  This kind of thinking - from both directions, the conceptual/theoretical v. working methods - has always interested me.  I have the dual impediments of training in science and in law, so I have to make sure I'm thinking halfway straight!

In the meantime, I'm shaping a pair of arches down in the shop without using templates and without trying to create anything in particular, except to make something that feels right.  I have enough meat to do corrections later.  In a bit, I'm going to get a socket set out, see whether the channel has worked itself into circular sections!

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Regarding various people's comments regarding surviving tools as "proof" of anything, I think a reminder is appropriate that without the Stradivari tool set, we would have exactly zero evidence that all of the Cremonese makers used anything at all in the way of drawings and tools. And the notation which has already been made elsewhere that anything that was generic enough to be useful was removed from the collection and used. If we don't allow that, then we have to conclude that they didn't use any tools except a purfling cutter (hard to imagine carving a head with that!)

So absence of evidence is definitely not evidence of absence regarding what they had and used.

Leaving only detective work. Or defective work, depending on who's talking.

--------------------------

On another point, I have enough experience making, and also teaching others to make, to see that at least one of the features that I regard as a definite sign of Cremonese work is easily removed if you believe that you just let the tools do their own thing without supervision. And I've seen evidence on Cremonese instruments that they avoided scraping out this feature even to the point of slightly sacrificing the smoothing of the surrounding territory. If, however, you follow cycloid templates carefully and don't let the tools rule, you will get there. 'Nuff said.

Carry on.......

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Mr. Darnton:  Things let unsupervised do seem to cause issues.  Especially tools.  Working on auto engines extensively really shows that enough is enough, once you're where you need to be stop doing things!  I loved doing engines.  We don't do that any more in old ways.  Which is probably "better" but takes a lot of the fun out of it.  

My notes and observations of random modern and the few nice old Cremonese I get to visit through glass has me suspecting I know where you are pointing.  I'll go look tomorrow at The Greffuhle, I made an appointment to get into the museum.  I usually bicycle down to say hi.  I always learn something new to forget on the way home!  

Thank you for all your useful observations over the many years.  Some stuff is actually sinking in!!!  

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On 10/3/2020 at 8:59 PM, Marty Kasprzyk said:

I found it easy to sketch an arch with whatever inflection point I imagined.   If the sketch was done on a thin wood it would be easy to cut it out and smoothed to make a half arch templet.

What else is necessary?

 

2020_10_03_0356.JPG

I now think I was wrong in suggesting that the arches could have been easily sketched long ago for making templets.

I now agree with David Burgess that the arch shapes were probably carved directly into the wood and that templets were unnecessary.  Once you've seen or imagined a shape it is not necessary to then draw it.  The Old Italian makers could have been talented  sculptors rather than artists or draftsmen.

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I find it reassuring that so many people "know" just how the folks 300 years ago did things. I'm guessing that this super power comes without having done any research into that time period at all. It's reminding me of a post some years ago where a poster managed to stretch the years of the Renaissance forward about 300 years in defense of a particular position.

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Context is everything. I understand the position that people just do what they like to do, make what comes out, and that's what they feel is best for them.  No problem. I get more wrapped up in the details of context when people start claiming to understand what someone in an entirely different culture some hundreds of years ago was thinking. That's a whole different level of task.

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3 hours ago, Michael Darnton said:

Context is everything. I understand the position that people just do what they like to do, make what comes out, and that's what they feel is best for them.  No problem. I get more wrapped up in the details of context when people start claiming to understand what someone in an entirely different culture some hundreds of years ago was thinking. That's a whole different level of task.

I'm happy to just be able to get some of our modern ways of thinking out of the way.  Thinking in an XYZ rigid system, for example.  Even if something happens to get some evidence behind it, there's no way to know what another is thinking, even with contemporaries.  

 

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Surely pi {3.14} was available to violin makers during the 1600's to fiddle around with - gotta have something to do while varnish is drying between coats don't you?

What are those three circles on that old Stradivari paper template?  Cycloid work or something else?

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12 hours ago, Marty Kasprzyk said:

I now think I was wrong in suggesting that the arches could have been easily sketched long ago for making templets.

 

Maybe you are right. Given the top centre of the arch, a low point or line for the recurve, the end of the arching figure at the edge crest, and most importantly the inflection point, it is possible to draw freehand an arch profile. Of course the inflection point has to be in a realistic position.

I've done it numerous times. If you check your drawn line against french curves, one for the upper convex part and one for the concave lower part, you will realise just how accurately it can be done.

 

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7 hours ago, uncle duke said:

Surely pi {3.14} was available to violin makers during the 1600's to fiddle around with - gotta have something to do while varnish is drying between coats don't you?

What are those three circles on that old Stradivari paper template?  Cycloid work or something else?

What if a circle the diameter of the larger scribed arc on the Strad molds were just the right size to roll a cycloid across the c-bout? Why would pi x arc = c-bout width, anyway?

Nah. . . . . why do that? It must just be a coincidence. . . .

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I did envision Mr. Burgess trying his hand with the bigger wheel diameter for cello making and then thought afterwards he deserves more respect than that.  That would seem foolish rolling a big wheel and pin to make a template.

Why does the pi equation work?  It is not up to me to have an explanation - I'm just a product of the smarter people here at maestronet.

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32 minutes ago, Michael Darnton said:

What if a circle the diameter of the larger scribed arc on the Strad molds were just the right size to roll a cycloid across the c-bout? Why would pi x arc = c-bout width, anyway?

Nah. . . . . why do that? It must just be a coincidence. . . .

what about the smaller scribed arc?  Where does it fit?  Or would that be the location of the hole for drawing the cycloid?   

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I have this unprovable idea that the original plan of the violin might have had the bottom of the scoop on the purfling, (an idea so logical that many makers unwittingly think that's how it's actually done) but then it was quickly discovered that moving the scoop in a bit would improve something so that's what they did thereafter. Given that the whole violin design uses the larger circle as a basic measuring unit, that couldn't be just abandoned. Perhaps the smaller arc is the actual circle used for throwing the cycloid to fall inside the purlfing, then? Of course it also appears to be the height of the upper block while the larger circle is the height of the lower block, and I think that's why many people stopped thinking when they noticed that.

We're hampered in our reverse engineering by not knowing if we even have any violins based on the original drawing model (which might have preceded even Andrea Amati). I think we have to assume that everything later is derivative in some way, not a replication, so it's interesting when basic features like the use of the 31.X mm measuring unit appear to have survived throughout the violin to the end of the Cremonese golden period.

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I don't think I've mentioned before that I think it would be MUCH easier to draw an outline using a set of circle templates derived on 31.X mm multiples (given that this is the source of all of the circles that make a violin outline) pushed against a drawn framework of boxes derived from the same distance than all of the circle-center-based fuss that people usually throw at the problem. That business of locating the circle centers seems like way too much in the way of rationalized gymnastics (and if you are a student of this, you will know that there are dozens of designs based on the location of the circle centers with all sorts of squirrly magical logic connected to finding those centers) given that the external measurements of the mold are extremely close to 31.X mm,  31.X mm x pi multiples, or derivatives of those.

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Speaking of squirrel logic in violin design, someone who was recently mentioned here came up with a plan some years ago for locating f-holes, and I did a drawing at the time for friends showing my version of his plan that I will share below.

Notice that none of the lines pass through any principle points on the f-hole, just as in his own design! Apparently a feature of his plan, not a bug. :-) One sees a lot of that kind of related-to-nothing thinking in violin analysis these days.

ffff.jpg

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