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Reasons for Stressing Plates with Tapered Ribs.


Joe Swenson
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22 hours ago, David Burgess said:

Sanding??? Heavens to Murgatroyd! :blink::P

 

7 hours ago, Joe Swenson said:

I know right?  I was excited to see Davide Sora sanding away to even out the blocks and rib structure using the same technique I use!! I thought this whole time it was cheating. But now... well... :rolleyes:

I know, but I am aware that for this I will go to the makers' hell, we'll see you there Joe.... :lol:

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4 hours ago, Davide Sora said:

 

I know, but I am aware that for this I will go to the makers' hell, we'll see you there Joe.... :lol:

Too funny!!!  :lol:  

But seriously. Its whatever gets the result you need.... Right?

I checked my flea market cello (posted on this a few years ago) Rib height is 119 mm  bottom block and corner blocks and 116 mm at neck block.  And looking from the side it appears all the taper in in the neck. The back plate looks dead flat.

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2 hours ago, Joe Swenson said:

Too funny!!!  :lol:  

But seriously. Its whatever gets the result you need.... Right?

I checked my flea market cello (posted on this a few years ago) Rib height is 119 mm  bottom block and corner blocks and 116 mm at neck block.  And looking from the side it appears all the taper in in the neck. The back plate looks dead flat.

Honestly, in cello it is difficult to understand the extent of this taper and if it were only on the top or even in the back, too much distortion is there in old cellos to be really sure.

Anyway, looking at my notes, not all my instruments have this taper because it is not what they taught me at school. I started to make the two staggered planes starting from the upper corners from 2003 "only", when I start going deeper into the study of the original cremonese making method acquiring the necessary knowledge to build up my own ideas to be able to question the teachings of the masters of the school and what indeed all the other makers did in those times, at least here in Cremona. It is not easy to get out of patterns that seem to be the consolidated tradition, but often people do things only by repetition without asking too many questions and sometimes going against the tide is interesting and rewards the daring....:)

But everyone chooses his own way and as far as the use of the sandpaper plane is concerned, I chose mine, going against the tide compared to Stradivari who certainly did not use it. Even if sometimes it may not seem so, I'm not an extremist of the old fashion and for this I deserve to burn in the flames of hell...;)

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On ‎2‎/‎8‎/‎2020 at 1:40 PM, martin swan said:

The neck angle in relation to what?

Sorry, I meant fingerboard angle. Or even more accurately, since the fingerboard is slightly bowed: string angle.

So my question is; Does the 2mm rib taper on the belly relate to a 2mm lower arching height, or the generally lower arches of the 'Golden Period' relative to his earlier instruments?

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On 2/8/2020 at 6:38 PM, Davide Sora said:

But everyone chooses his own way and as far as the use of the sandpaper plane is concerned, I chose mine, going against the tide compared to Stradivari who certainly did not use it. Even if sometimes it may not seem so, I'm not an extremist of the old fashion and for this I deserve to burn in the flames of hell...;)

To be completely honest, I worked in the same building with the American Case Company for many years. They had a disk sander which was approximately four feet in diameter, removed material very quickly, and the "industrial grade" abrasives left so little abrasive debris in the end grain of the blocks, that taking the final .5mm or so using a plane was a breeze, without rendering the plane blade dull very quickly. Embedded abrasives can be a bit problematic, when followed by fine-edged cutting tools.

Now, while it as not as fast as the monster disk sander, I find it acceptable to hand-plane as much a 4mm off blocks and ribs when the rib assembly is complete, rather than try to micromanage the block heights in the first place. But it took me lots of practice, and some mistakes to get there, with a plane alone.

This isn't to take anything away for Sora's very valuable posts.

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54 minutes ago, Jim Bress said:

This is from 1690. I think the taper is present. The numbers alone leaves much for interpretation. It’s easier to see with full size photographs and a straight edge. 
84FFD40C-6B95-48A1-A082-4C3BAC7ECE1F.thumb.jpeg.8f4a96d684c6404dc14d3df559c9842a.jpeg

Hmm, dunno bout them numbers?

What about the 1679 'Hellier' It has the taper and it's well before the 'Golden Period'? It also appears to have a low arch

https://www.roger-hargrave.de/PDF/Artikel/Strad/Artikel_1987_09_Stradivari_Antonio_Hellier_PDF.pdf

https://tarisio.com/cozio-archive/property/?ID=40237&l=yes

https://www.alamy.com/hellier-stradivarius-image184233735.html

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1 hour ago, sospiri said:

Sorry, I meant fingerboard angle. Or even more accurately, since the fingerboard is slightly bowed: string angle.

So my question is; Does the 2mm rib taper on the belly relate to a 2mm lower arching height, or the generally lower arches of the 'Golden Period' relative to his earlier instruments?

The circles inscribed on the form indicates the rib taper.

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22 minutes ago, Michael_Molnar said:

The circles inscribed on the form indicates the rib taper.

Inscribed on the mold as Roger Hargrave suggests? Strad was using inches so the ribs would presumably be 1 1/4 which is exactly 31.75, but how much shrinkage if any has happened? Do ribs shrink much across the grain?

The neck root ribs heights seem to vary.  I'm suggesting it's possibly related to arching height, so 2mm taper for a 14mm belly arch?

 

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  • 1 year later...
On 2/6/2020 at 9:27 PM, Davide Sora said:

Making a gentle curve in the taper would be much more complex

 

On 2/7/2020 at 9:45 AM, Davide Sora said:

Some Del Gesù have the lower block a bit lower than the corner blocks, that is, the four corner blocks are higher than the upper and lower blocks, with the usual more accentuated taper in the upper bouts. I don't know if this depends on interventions of posterior restorers, but the aesthetic effect is not bad at all, giving a strong appearence to the box  from the side wiew.

Davide, your videos are wonderful. thanks.

I contemplated some Del Gesu tapering data before making my last violin.   I decided to sand the top of the garland in a 10m spherical radius dish which I use for guitar tops.  This allowed me to achieve; lower block 30.5mm, lower corners 31mm, upper corners 30.5mm and upper block 29mm.  These are nearly identical to the Kreisler numbers.  Bass bar was shaped with the top held in the radius dish. 

The Violin looks really nice, particularly now it has settled with a small curve in the back.

 

 

 

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7 hours ago, David Stiles said:

 

Davide, your videos are wonderful. thanks.

I contemplated some Del Gesu tapering data before making my last violin.   I decided to sand the top of the garland in a 10m spherical radius dish which I use for guitar tops.  This allowed me to achieve; lower block 30.5mm, lower corners 31mm, upper corners 30.5mm and upper block 29mm.  These are nearly identical to the Kreisler numbers.  Bass bar was shaped with the top held in the radius dish. 

The Violin looks really nice, particularly now it has settled with a small curve in the back.

Thanks for your appreciation of my videos.:)

I know the radiused dish technique for guitars, but I don't think it was the one used by del Gesù, who probably worked with just a plane. In fact the only trend I see in the ribs of the Gesù are the corner blocks left protruding with respect to the upper and lower blocks, probably both on top and back side. But it is difficult to be sure given the "slovenly" work:lol:

Out of curiosity, how did you make your 10m radius spherical dish?

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Hi Davide,  'slovenly', great choice of words!   I imagine that large sheets of self adhesive sandpaper would have been hard to come by in the time of Del Gesu also.  

I do like the radius dish method, it is repeatable and gives perfect contact on the gluing surface.  I think I will continue with it.

There is an excellent guitar making book by Gore & Gilet in Australia.  It gives full instructions for making radius dishes starting with a traditional device known as a shipwright's compass to draw the radius.  Curved guide rails are then made which rotate around a centre pivot such that router is drawn back and forward over the rails as they are slowly rotated.

Having said this, I bought mine ready made by CNC router.

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6 hours ago, David Stiles said:

I imagine that large sheets of self adhesive sandpaper would have been hard to come by in the time of Del Gesu also. 

Of course not, he used the sand of the Po river glued with casein glue on a flat wooden panel.

I'm just kidding ... even if it can't be ruled out entirely. I seem to have glimpsed something like this on my last trip back in time with my modified DeLorean DMC-12:lol:

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Volcanic pumice deposits are common around the Mediterranean and it is a commonly used sanding grit.

I use it loose on a flat granite slab concentrating on the larger end blocks first and then the corner blocks. And I test for overall flatness on the saw table surface. It is a fairly slow process but I find it the only reliable way to get the blocks, lining and rib surfaces flat.

In my experience sanding sheets glued to a flat surface always wear the rib/lining surfaces below the level of the block ends. And it is not too hard to imagine why that occurs.

I should add that I do that with the inside form still attached.

 

 

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9 hours ago, Dennis J said:

Volcanic pumice deposits are common around the Mediterranean and it is a commonly used sanding grit.

I use it loose on a flat granite slab concentrating on the larger end blocks first and then the corner blocks. And I test for overall flatness on the saw table surface. It is a fairly slow process but I find it the only reliable way to get the blocks, lining and rib surfaces flat.

In my experience sanding sheets glued to a flat surface always wear the rib/lining surfaces below the level of the block ends. And it is not too hard to imagine why that occurs.

I should add that I do that with the inside form still attached.

Very interesting, thanks for reporting, I had never heard of anyone using this sanding method, although I have thought several times to try something similar.

Regarding the blocks that remain proud of the ribs and linings when flattening on sandpaper board, this is true if you don't pay attention (usually happen when too much pressure is applied), but once you are aware you can avoid it. The trick is mainly keeping your hands directly on the blocks and not on the form or on the ribs,  applying the pressure gently and carefully checking that the level is uniform on an accurate reference plane (I use a thick glass plate).

Then I have to say that this problem is much more marked with spruce blocks, but with low density willow is really non-existent.

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