Violin Forum/Message Board

[John Cadd]

I have a good question about Strad posters .Looking at the most modern , detailed ones with Xrays and thicknesses and all the bells and whistles included there is still something missing. Have you noticed what that is ?
Compare them with the Sacconi book . He shows relief map style diagrams . Why do Strads not include that? It would automatically contain all the arching information .Lasers can tell if a volcano is rising or falling by a few centimetres from space. Lasers will not fry the varnish .What`s going on Strads ?

[Michael Darnton]

That kind of relief map doesn't really show enough definition in the fast-moving areas. I don't know if you are aware that I've been using lasers for a couple of decades and have written a bit about it--
https://violinmag.com/book/Laser%20Scanning%20Violins.pdf
https://darntonviolins.com/arching-revealed-over-the-last-few-years-ive/
https://darntonviolins.com/for-no-other-reason-than-that-its-so/
https://darntonviolins.com/laser-scans-of-cremonese-arching/
Check out the video at the bottom of that last post!

I use these scans to make arching templates, both directly or by generating curtate cycloid templates that don't have the distortions of the old violins but do fit almost perfectly. I use this online program:
https://cs.uwaterloo.ca/~smann/ccycloid/

There's a subscription site on the web that took this idea and has been scanning violins this way for a while.
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[John Cadd]

Does the distortion matter for backs as much as fronts? Have there ever been bellies with a higher bass side and a lower sound post side? Have they tried lasers on the Messiah violin that nobody is allowed to play. Also Has the Messiah been strung up or left with slack strings . Did they ever change the bassbar on that violin ?
In the disagreement between Catenary curves and Cycloid curves is there any solid reason to prefer one against the other. The word Catenary appears in the Sacconi book but not the word Cycloid .Is there a reason for that ? That`s asking a question rather than stating a fixed position . Do bridge builders prefer Cycloids or Catenaries ?
Why is there an almost automatic preference for Cycloids without a detailed reason which abolishes Catenaries when they are so close in shape . A guillotine preference within the world of distorted bellies seems hardly good mathematics or physics .

[Michael Darnton]

Distortion doesn't seem to hurt the sound. I think that's because the original concepts remain even through a little distortion.

The bar falls under pressure, the post pushes up, so violins always end up sunken on the G side and pushed up on the E.

I don't know what recent things have been done with the Messiah. You're right---that would be a great one to laser! I don't kow about the bassbar.

I have a lot of trouble getting people on the cycloid idea. Catenaries are for bridges so people like the idea for violins. But bridges are built for strength, to resist movement. They're not violins, built to move. The Germans built violins for strength. How well has that worked out for them?

Cycloids do one thing that catenaries can't. If the violin top is supposed to move, where do you suppose that happens? The catenary doesn't provide any information, not a bit, for the scoop around the edge, where the hinge for the vibrating top is. I have come to believe that the center of the curve means absolutely nothing--that all of the important stuff happens around the edges. The cycloid is all about edges. Catenaries are all about the middle.

In that context the catenary is absolutely useless.
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[John Cadd]

I made a violin from the instructions in Strad Magazine given by a reader . The idea was to make all the long and cross curves with Parabolas , which involved much calculations with a simple calculator . After that one I thought a thin chain would produce quicker results . That was using a white plastic covered chipboard sheet clamped vertically and a grid sratched on the surface. The chain produced immediate readings to be written down. I always assumed these were Parabolas but No. These Catenary curves are not Parabolas , If you made a sattelite dish with catenary curves the dish would not focus properly like a parabola. So now we have Three contenders in the ring which look similar .Cycloid--Catenary --Parabola .
Catenary is more direct and needs less calculating. Some would say the Cycloid "looks right " in an artistic way but a bridge builder might not agree just based on a visual impression.

[Michael Darnton]

And again, parabolas don't specify edge contours. I don't consider a strategy to be useful when it ignores the most complex part of the problem.

There's an interesting thing happening in Stradivari violins where the deeper the scoop the farther it is from the edge, or when it's shallow, the bottom of the scoop is right up against the purfling. You can see this in other Cremonese violins as well, and I know an Amati with a VERY deep scoop, VERY far from the edge on which the edge is uniquely 5mm thick, because that scoop forces this. This kind of coordination only happens when you are using a complete template which includes the rise towards the outside from the bottom of the scoop--the outer edgework. Modern makers who use templates don't--they cut off the part of the template past the purfling. They also insist on using whole templates, which are only useful for one arch. With a single half-template you can recreate many of the Cremonese archings around the edge by pushing it farther and nearer to the center, keeping the exact shape of the arch from the inflection point outward exactly the same. If you then just blend the center to get the missing blend where the halves meet you'll get a very Cremonese-style arch. One place Cremonese violins ARE inconsistent is in the center of the arch.

Think about the implications of that for a bit.
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[John Cadd]

For some reason I have always assumed your Curtate cycloids method was just using the top ,main part of the curve and not the outer edges that reverse the curve. But it sounds as though you still need to freehand blend between the main top curve and reaching towards the edges. But Physically what form is your template? Is it wood or plastic or metal ? How do you arrive at the shape ? What is the detailed process . The top half of the plate looks to cause more confusion as the "bulge " looks narrower on some Del Gesu models. It does not try to spread out to fill the full width .
I am feeling a conflict or contradiction between the generally broad brush aspect of making plates and the exact ,precise clinging to cycloids but watered down precision because of the "joining the gap "part of it all .A lot of the instructions are either too rigid eg xray thicknesses which are conflicting with Thicknesses don`t matter--Weight does not matter--Tap Tones do not matter --Varnish does not matter.All balanced by the exact opposite opinions from any commentators . We need relief maps for the exact out of shape instruments as they are to get a decent comparison . Then if they work really well and collapse in 20 years --Who cares ?

[John Cadd]

The interesting difference between a parabola (which is a better curve for bridges )and a catenary is the center of a catenary flattens out more which would suit a violin bridge better .It`s not as rigid as a parabola. Maybe we should get the Spanish Staircase builders to try it out with their terra cotta tiles all slapped together with weak and runny mortar .

[John Cadd]

Violins are made to move --but you have also said that a violin vibrating is wasting energy that should be turned into sound.
A Parabola is used for strength or rigidity but that depends on the material it`s made of.Steel or concrete would be rigid . A curve made of strands of hard and soft wood grains side by side would be very weak and flexible unless supported by a bass bar and a sound post .The cycloid and catenary and parabola drawn on paper can hardly be distinguished from each other .
Calling any parabola or catenary rigid is suddenly leaping to a verbal extreme. A cycloid made of steel would also be rigid .Was Guarneri bothered about scoops ? Amati might have gone too far and weakened the sound with his scoops . The Hill book mentions Strad late period violins where the arching begins straight upwards from the purfling edge. That is a reliable source of verifiable fact that needs no scientific proof or theories. If it worked Strad would not need to know any more .He was very selfish not to write out how or why it worked. It just did .

[Michael Darnton]

Hills oversimplified. Late Strads still have channels with a concave rise inside the purfling. Just less than some previous examples.

This is the back of a 1731 Strad:



The common modern misinterpretation of Hill is to start right off the purfling with either a straight line up, instead of a rising concavity, or even to turn immediately convex at the purfling.
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[John Cadd]

I just enjoyed a rambling conversation on Maestronet dragging all sorts of measurements into the mix --all about the Golden Strad era.The phrase I liked most was ---"Slurry of confusion ", which neatly sums up the whole subject .
But the general feel is that the Late period was not as good as the Golden era for whatever reason. (Looking back to my query ,whether Strad knew exactly why his violins sounded better than the others .) Like using the plus or minus symbols on a map the stand back (minus) position avoids getting bogged down in details that Strad would not have used or even understood .On the Plowden Strad poster the Xray cross section shows the edges clearly enough. That scoop may be there for visual appeal as much as anything. If a scoop is desired then it should be planned for as the plate is worked on . Anything else is just painting yourself into a corner . Has anyone tried a deep scoop and had to cut underneath to get back up to the edge of the ribs? Very unlikely .
Is there any truth in the rumour that violins were put together first and purfling was done afterwards ? Have all "authentic " makers had a go at fixing the neck on with a big nail ?How ridiculous to do that ? How about varnishing after the fingerboard is glued on? Just leave the difficult bit bare .
On a furniture site the rcomendation for curves is to use a long steel ruler bent to give a smooth curve. Quick and simple . A slurry of confusion. Just use a thin lath for the curves. Now we have to see if that`s mathematical . I have never used a thin lath for a violin (not a Lathe btw in case anyone sets up some heavy machinery ). I did that when I made our headboard for the double bed. It looks better than shop versions .

[Michael Darnton]

Just added a photo to yesterday's post. A 1731 Strad Back.
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[John Cadd]

The cello picture with a total split is just in my area right now. The back of a Telesforo guitar I received had suffered a similar fate when it was trodden on and the imprint of a foot showed up on the packing .The back had separated full length with another large piece hanging by a thread.
Should I describe my repair method here or make it another topic ?
My home made clamping method was using pairs of wooden clamps with a kind of tongue and groove appearance. I used fish glue to fix the clamp blocks and small wedges for applying pressure .The fish glue was placed away from the split , in areas that could be released with patches of damp tissue taped on the surface. The soft wood clamps allowed moisture to penetrate onto the fish glue with minimal wetting of the instrument surface . Levelling the top surface and maintaining the original curves was the crucial thing to work on .The row of clamps could be slackened and released for edge adjustments as they meshed together .I should have photographed it . I kept the used blocks in a bag just in case I see another disaster . A fun project .
The main thing I learned was to fit all the blocks at 90 degrees to an imaginary straight line along the meandering split . If the blocks were fitted square to each part of the split it would be difficult to disengage the main sections half way through the job . In a cello the spruce would mostly split in a fairly straight line but running "off grain" parts would be the worst thing . How to be a Dinosaur Dentist .That`s the look of all the clamp blocks poking out before they mesh together .

[John Cadd]

Catenaries are for bridges falls into the thinking about the external visual appearance and most people would not bother what was under the surface of a violin. There are no bridges supported by a wooden post and a wooden beam running crossways . So taking that logic too far makes a verbal impact with a large slice of truth being ignored just to make the verbal point . Without going further we need to examine what standard of logic is being used . It moves towards smoke and mirrors . The fine distinction between catenary and cycloid is destroyed by the sound post and the bass bar and also long term distortion .Three undeniable influences that have to enter the Pure Mathematics aspect of Perfect Curves .