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Davide Sora's bench


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6 hours ago, Christian Pedersen said:

Very pleasant wear. (other than the possibly poor technique) Thank you! 

6 hours ago, Nick Allen said:

That's just playing with gusto! I like seeing this kind of stuff on my violins!

I think the damage to the edges of the Cs and the corners (especially the upper right corner) is hard to avoid with heavy professional use. When I see fast, complex passages played, I'm always amazed how don't happen much more frequently.:) The corners are aesthetically pleasing and a legacy of the Baroque style, but they don't make life easier for the player. I always tell my clients not to be afraid of this type of damage, and I always fix it for free.

For those who don't have a perfect technique yet and feel intimidated by doing this type of damage, or to be more relaxed during rehearsals or study (or if the luthier charges for repairs...), there are always these protections who do their job very well: https://www.sharmusic.com/C-Clip-Protector-Violin?quantity=1

But they wouldn't look good at a concert.:wacko:

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1 hour ago, MikeC said:

Davide show an example of repair if you have any pictures of that.  Would you make it look like new again or would you smooth it out so it begins to take on an antique look? 

Unfortunately I don't have any photos, I don't bother taking them because they aren't real repairs, just touch-ups. However I touch up with the same colored varnish to make sure they don't catch the eye too much (the exposed wood doesn't looks good effect just after a fresh chipping) but I don't go crazy making them invisible to a close inspection. If instead of chipping it is just uniform wear, such as for example on the upper edge where contact with the hand smoothly wears out the varnish, or on the rib itself, I only apply clear protective varnish without touching up the colour, leaving the effect of wear.

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On 11/30/2022 at 7:02 AM, Davide Sora said:

Unfortunately I don't have any photos, I don't bother taking them because they aren't real repairs, just touch-ups. However I touch up with the same colored varnish to make sure they don't catch the eye too much (the exposed wood doesn't looks good effect just after a fresh chipping) but I don't go crazy making them invisible to a close inspection. If instead of chipping it is just uniform wear, such as for example on the upper edge where contact with the hand smoothly wears out the varnish, or on the rib itself, I only apply clear protective varnish without touching up the colour, leaving the effect of wear.

This is the way. 

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  • 1 month later...

I made this new video that illustrates how I measure the speed of sound using @Don Noon's system, which he kindly shared in this old Maestronet topic:

https://maestronet.com/forum/index.php?/topic/321492-ridiculously-easy-way-to-measure-speed-of-sound/

 

I made two versions of the same video, this is the one with English texts and captions: https://www.youtube.com/watch?v=jU4h2Ievtq4


Here is the version with Italian texts and captions: https://www.youtube.com/watch?v=oqFVRiWaXdQ

 

Measuring the speed of sound has never been easier, thanks @Don Noon !:)

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  • 5 weeks later...

The center joints topic is always hotly debated and pops up from time to time on the forum. The truth is, there's no single good way to do them, just different approaches, and anything can go as long as the glue joint holds up over time and is invisible and reversible.

Since they were still missing from my video series, I started making them to show the way that works best for me and the criteria I use. Here are the first two on preparing the pieces before you start the actual jointing. As usual, they are too much detailed, I apologize in advance for any boredom they might cause.:P

Four more will complete the series in the coming days.

Find the English translation of the Italian text on the description page under each video.

1) Center joint of the violin top plate - Part one - Wood selection and preparation of the pieces

https://www.youtube.com/watch?v=DrcRycPbj6s&t=134s

2) Center joint of the violin back plate - Part one - Wood selection and preparation of the pieces

https://www.youtube.com/watch?v=bL_pw1vTSUQ

 

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18 minutes ago, MikeC said:

Awesome videos as always!  Do you ever use a one piece back?  I'd like to see that, since I have one that I need to start working on.  

Yes, of course I also use one-piece back. But what exactly would you like to see? The criteria are the same for the two-piece back, except that it doesn't have to be joined:)

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8 hours ago, MikeC said:

It's just an odd shape on the back side.  That would be a lot of wood to plane off.  Maybe I should saw off some of the excess?  I've only ever done the two piece type

Yes, usually a wedge is cut off and if it's worth it (good flames and fairly perpendicular grain) it's used to make matching ribs. I use a Japanese Ryoba or even Kataba saw, however one for making through cuts. A bandsaw could also be used if you have a proper one, you will need to make a special jig to make the slanted cut and you will take away more wood with the cut. But it's riskier, I prefer to cut by hand so as not to risk throwing everything away.:P

Onepiecebacksawandribs.thumb.jpg.fd80080049637601cfed72dbb5671b8d.jpg

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Thanks Davide,  I'll get one of those Japanese saws since they make a thin cut.  I have a western style rip saw but it would waste a lot of wood and my band saw is a small table top saw suitable for cutting necks and plate outlines but not big enough for this kind of cut.   

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In this video I show the tricks I use to hold the pieces to be planed to make the joint, and the planes I use. It is very important that when clamping the pieces in the vise they do not deform, causing the gluing surface to twist when removed from the vise even if you plane it perfectly flat.

 

Center joint of the violin plates - Precautions for the vice and planes used

https://www.youtube.com/watch?v=uicxFdod5Rg&t=199s

 

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In these videos the actual jointing and the dry test with the clamps:

Center joint of the violin top - Part two - Setting up and finishing the joint

https://www.youtube.com/watch?v=fhTka5_yLK4&t=903s

Center joint of the violin back - Part two - Setting up and finishing the joint

https://www.youtube.com/watch?v=POGJmMzBy9E&t=628s 

Coming soon is the final video where I show the glue I use and the gluing of the joints.

 

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On 1/21/2023 at 2:05 PM, Davide Sora said:

I made this new video that illustrates how I measure the speed of sound using @Don Noon's system, which he kindly shared in this old Maestronet topic:

https://maestronet.com/forum/index.php?/topic/321492-ridiculously-easy-way-to-measure-speed-of-sound/

 

I made two versions of the same video, this is the one with English texts and captions: https://www.youtube.com/watch?v=jU4h2Ievtq4


Here is the version with Italian texts and captions: https://www.youtube.com/watch?v=oqFVRiWaXdQ

 

Measuring the speed of sound has never been easier, thanks @Don Noon !:)

I think there should be a factor included for density. From my experience higher density wood gives higher frequency even if the wood is not as high performance. The method then indicates too high speed of sound.

Higher density wood does have some correlation with higher speed of sound but not always.

 

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36 minutes ago, Peter K-G said:

I think there should be a factor included for density. From my experience higher density wood gives higher frequency even if the wood is not as high performance. The method then indicates too high speed of sound.

Higher density wood does have some correlation with higher speed of sound but not always.

That may probably make sense, but I'm not able to give you an answer. You should ask @Don Noon , I don't have the scientific knowledge necessary to argue.

As for wood with higher density, I have the same impression as you, higher speed but not always, other factors such as the direction of the fibers could be more decisive

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Last episode of the center joints: finally it's the gluing time!!

https://www.youtube.com/watch?v=VfYmqI52g8Q&t=184s

Hot hide glue is highly recommended (a must!), beware of synthetic glues.:)

Anyone who had the patience to watch them all without skipping even once, wins a voucher for a visit to my workshop!

Travel excluded, of course...:lol:

 

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22 hours ago, Peter K-G said:

I think there should be a factor included for density. From my experience higher density wood gives higher frequency even if the wood is not as high performance. The method then indicates too high speed of sound.

Higher density wood does have some correlation with higher speed of sound but not always.

You might be confusing effects here. The method detects the frequencies of the natural modes of vibration of the sample. These frequencies are directly dependent on the sound speed, sample geometry and boundary conditions (suspended in air, lying on a table, held in hand, etc.)

Of course the sound speed is affected by density and elastic modulus of the material but no need to add in a correction because that sound speed is what it is.

Think of it as density plus stiffness determines sound speed, then sound speed plus geometry determines frequency.

The formula for the natural longitudinal vibration of a beam is roughly...

Sound Speed = (Geometry Factor) x (Natural Mode Frequency) x 2 x Length

For a beam with no restraints, say suspended in the air, the geometry factor is 1.

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23 hours ago, Peter K-G said:

Higher density wood does have some correlation with higher speed of sound but not always.

A given piece of spruce won't necessarily have the speed of sound be a fixed ratio of density, but "correlation" refers to a larger set of datapoints.  So, yes there is a definite correlation between density and longitudinal speed of sound, but the scatter is huge.  This is my inventory, after being torrefied.

Cvsrho.jpg.deb63d6b26adf039443fd949e8fe9625.jpg

46 minutes ago, ctanzio said:

Sound Speed = (Geometry Factor) x (Natural Mode Frequency) x 2 x Length

For a beam with no restraints, say suspended in the air, the geometry factor is 1.

True, as long as the "beam" is perfectly straight and uniform.

Lest we get too carried away with longitudinal speed of sound, it is important to remember that the rarely measured crossgrain stiffness matters as well, and I do have some crossgrain data (via borrowed Lucchi meter)... but the correlation between speed of sound and density is close to zero.  It's even closer to zero when you look at damping correlation to density (this is ONLY damping for longitudinal bending).

And then there are other unknowns, like stiffness in the radial direction, shear stiffness, and how these all vary with the slope of the arching, runout, off-quarter, etc., and how damping in all of these directions might matter, and how the damping might vary with frequency.

So although density and logitudinal speed of sound aren't UNimportant, it's only a modest start in knowing what you have, and how things will ultimately turn out (in spite of what some makers might claim... and you know who you are :)).

 

 

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On 2/24/2023 at 3:31 PM, ctanzio said:

You might be confusing effects here. The method detects the frequencies of the natural modes of vibration of the sample. These frequencies are directly dependent on the sound speed, sample geometry and boundary conditions (suspended in air, lying on a table, held in hand, etc.)

Of course the sound speed is affected by density and elastic modulus of the material but no need to add in a correction because that sound speed is what it is.

Think of it as density plus stiffness determines sound speed, then sound speed plus geometry determines frequency.

The formula for the natural longitudinal vibration of a beam is roughly...

Sound Speed = (Geometry Factor) x (Natural Mode Frequency) x 2 x Length

For a beam with no restraints, say suspended in the air, the geometry factor is 1.

I don't think I'm confusing effects, I do understand the maths. It is the method itself I have thoughts about, regarding how higher density wood may give a higher frequency just by it being more dens, which in turn might  give an indication of higher speed of sound than it actually is.

The only way I can think of to confirm this hunch is by testing the method with a lot of different dens wood against lucci meter readings.

I use this method all the time and you could say it's a good enough method for sorting out tone wood you will discard or use.

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