Rib Taper hypothesis #43,759


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3 hours ago, Wood Butcher said:

So a top without a uniform thickness makes it a “well observed Amati model” and English?

not quite sure how you came to that conclusion.

It was suggested that the pin isn't seen on the front of the instruments which have it on the back (i.e. Amati family) because they used it on the back as a point to establish the back thicknesses, and this was not necessary on the front because they made the front a uniform thickness. 

My point is that we cannot presume that the Amati family made the front a uniform thickness. Some people believe Stainer received his training in Cremona, and there is at least one example I am aware of which the front is not a uniform thickness. Cozio writes that the Amati family thicknessed their fronts the same as the backs.

Betts made violins on the Amati model which I would consider "well observed". Being one of the foremost dealers and experts of his time he would have seen plenty of Amati violins, presumably many still in a state closer to original than we see today. Maybe along with the outline, ffs, scroll etc he also copied the thicknesses he observed.

I have seen, for example, Betts Amati model violins which have fronts thicknessed the same as backs. You say this is different to your reading of English thicknessing. My experience is different to yours, but either way we have both seen fronts on English violins which don't have uniform thicknesses.

Again, my point is really that we cannot presume that the Amati family made their fronts a uniform thickness.

 

 

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On 11/21/2020 at 9:34 AM, Laurentius said:

Why would there be no pin in the top?  I am conjecturing that since the rough thicknessing was simple, basically starting out with a one thickness measurement,  no hole and compass was thought necessary.  

I can't speak for you as a maker but the bellies of my work are quite a bit higher than the back plates.

Assuming the marks are from a clamping system why run the screws deeper into the spruce when the extra turns just to leave marks inside a plates aren't needed.

As for Stainer, it's a simple matter of " hey uncle duke, how do you like my leftover screw/bolt clamping remnants for all to see later down the road?" 

My reply to that is "pretty good Sir, that's better than what I do in regards to neatness.

I still have my own boards, templates and such to prove my own theories but why?

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17 hours ago, Wood Butcher said:

This is entirely different to my reading of English thicknessing, which has a thick spine running down the centre of the plates, becoming thinner towards the edges.

 

A thick central spine thinning to the edges could be considered a typical thicknessing profile of the Amatis (at least in the backs)

https://www.roger-hargrave.de/PDF/Artikel/Strad_Amati/Artikel_3_pdf_PDF.pdf

It is also interesting that although this viola retains its original neck, the strad poster notes that the front thicknesses have been reworked.

11 hours ago, David Beard said:

This is some sort of confusing.  There is no basis for thinking the Amatis put 4 or 5mm of wood in the tops near the bridge.

This is an interesting read, thickness diagrams at the end

https://www.roger-hargrave.de/PDF/Artikel/Strad/Artikel_1987_09_Jacobus_Stainer_1697_PDF.pdf

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On 11/23/2020 at 3:07 AM, MikeC said:

Another mystery is why the hole is only on the back, not the belly?  Any theories? 

- it is also the case on the friedberg instrument

-If one of the goal is the check of the thickness the upper F holes on the table  could play this role  making the hole useless...

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There is another possibility that hasn’t been mentioned.

My own theory is that the hole may have to do with centering the c bouts. There was a long thread about this several years ago that I can’t find now, where I posted some pictures of a jig I used when I was making “baroque” violins. I can’t find any picture of that now, either, and the jigs are in a box somewhere, but it was just a piece of wood, about 50mm tall and 140mm wide, and about 7mm thick or so. There were two slots about 3mm wide and 32mm tall cut into it at the distance of the ribs, so the jig slipped over the ribs rather snugly at the narrowest point of the c bout. In the center of the piece of wood is a small hole that is drilled through, from top down.

I made the jig because I was trying to emulate the process that Hargrave described. The system worked well, but I ran into a problem - using locating pins keeps the upper and lower blocks on the center line, but the rest of the ribs are free to move around, and are hard to corral when it comes time to glue things together. I wanted to keep the center of the fiddle on the center line as well, especially the part between the upper eyes of the ff’s.

What I did was

1)  drill a hole on the center line of the form at the narrowest spot (same size hole as the one for the jig)

2) with the finished ribs still on the mold, place them on the back using the locating pins and take the first outline for sawing. At the same time, place the gimlet through the hole in the form and drill all the way through the plank for the back, which has been thicknessed pretty much to the finished height, but is still just a flat board. Put your finger on the other side so you can feel when the point starts to emerge.

3) finish the back except for the final outline and purfling/edgework

4) take the ribs off the mold, attach the neck

5) place the ribs w/neck on the back using the center pins, place the jig on the ribs, slide the gimlet through the hole in the jig and rescrew the gimlet into the hole in the back that it made before.

Now the upper block, narrowest point, and lower block are all on the center line, and will stay there while glueing up.

This system works pretty well, but it doesn’t explain exactly the ventral pin thing. For one thing, the placement of the pin is not normally the narrowest point of the ribs. But maybe it could be that whatever jig they were using was designed to go wherever they decided the thickest point was going to be, as when you reinsert the gimlet there’s just not that much wood to hold it in place. It might also be handy to have a hole already where you’re going to measure the thickness from, so you don’t have to keep re-measuring it as you go.

I don’t strongly believe that this is the reason for the pins, but I think it’s possible that it’s something like this. my idea may be some primitive version of the actual model. thought I'd throw it into the mix.

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On 11/24/2020 at 2:42 AM, uncle duke said:

I can't speak for you as a maker but the bellies of my work are quite a bit higher than the back plates.

Assuming the marks are from a clamping system why run the screws deeper into the spruce when the extra turns just to leave marks inside a plates aren't needed.

As for Stainer, it's a simple matter of " hey uncle duke, how do you like my leftover screw/bolt clamping remnants for all to see later down the road?" 

My reply to that is "pretty good Sir, that's better than what I do in regards to neatness.

I still have my own boards, templates and such to prove my own theories but why?

:)

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3 hours ago, Kevin Kelly said:

There is another possibility that hasn’t been mentioned.

My own theory is that the hole may have to do with centering the c bouts. There was a long thread about this several years ago that I can’t find now, where I posted some pictures of a jig I used when I was making “baroque” violins. I can’t find any picture of that now, either, and the jigs are in a box somewhere, but it was just a piece of wood, about 50mm tall and 140mm wide, and about 7mm thick or so. There were two slots about 3mm wide and 32mm tall cut into it at the distance of the ribs, so the jig slipped over the ribs rather snugly at the narrowest point of the c bout. In the center of the piece of wood is a small hole that is drilled through, from top down.

I made the jig because I was trying to emulate the process that Hargrave described. The system worked well, but I ran into a problem - using locating pins keeps the upper and lower blocks on the center line, but the rest of the ribs are free to move around, and are hard to corral when it comes time to glue things together. I wanted to keep the center of the fiddle on the center line as well, especially the part between the upper eyes of the ff’s.

What I did was

1)  drill a hole on the center line of the form at the narrowest spot (same size hole as the one for the jig)

2) with the finished ribs still on the mold, place them on the back using the locating pins and take the first outline for sawing. At the same time, place the gimlet through the hole in the form and drill all the way through the plank for the back, which has been thicknessed pretty much to the finished height, but is still just a flat board. Put your finger on the other side so you can feel when the point starts to emerge.

3) finish the back except for the final outline and purfling/edgework

4) take the ribs off the mold, attach the neck

5) place the ribs w/neck on the back using the center pins, place the jig on the ribs, slide the gimlet through the hole in the jig and rescrew the gimlet into the hole in the back that it made before.

Now the upper block, narrowest point, and lower block are all on the center line, and will stay there while glueing up.

This system works pretty well, but it doesn’t explain exactly the ventral pin thing. For one thing, the placement of the pin is not normally the narrowest point of the ribs. But maybe it could be that whatever jig they were using was designed to go wherever they decided the thickest point was going to be, as when you reinsert the gimlet there’s just not that much wood to hold it in place. It might also be handy to have a hole already where you’re going to measure the thickness from, so you don’t have to keep re-measuring it as you go.

I don’t strongly believe that this is the reason for the pins, but I think it’s possible that it’s something like this. my idea may be some primitive version of the actual model. thought I'd throw it into the mix.

That's a complicated idea.

I attach the neck and ribs as soon as the sides are made.

Then I pin the length and position of the sides onto the flattened (on inside) board for the back.

I wiggle and push/pull neck and sides around pins until the center line is good and the ribs at the main bout lines support the ratios I want.

I clamp things in place and use dividers to check everything.

It isn't difficult or complicated at all.

Once I like the positioning of the sides, I scribe this into the back.  The etched line and the pins make it easy to restore the allignment later for gluing.

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4 hours ago, Kevin Kelly said:

There is another possibility that hasn’t been mentioned.

My own theory is that the hole may have to do with centering the c bouts. There was a long thread about this several years ago that I can’t find now, where I posted some pictures of a jig I used when I was making “baroque” violins. I can’t find any picture of that now, either, and the jigs are in a box somewhere, but it was just a piece of wood, about 50mm tall and 140mm wide, and about 7mm thick or so. There were two slots about 3mm wide and 32mm tall cut into it at the distance of the ribs, so the jig slipped over the ribs rather snugly at the narrowest point of the c bout. In the center of the piece of wood is a small hole that is drilled through, from top down.

I made the jig because I was trying to emulate the process that Hargrave described. The system worked well, but I ran into a problem - using locating pins keeps the upper and lower blocks on the center line, but the rest of the ribs are free to move around, and are hard to corral when it comes time to glue things together. I wanted to keep the center of the fiddle on the center line as well, especially the part between the upper eyes of the ff’s.

What I did was

1)  drill a hole on the center line of the form at the narrowest spot (same size hole as the one for the jig)

2) with the finished ribs still on the mold, place them on the back using the locating pins and take the first outline for sawing. At the same time, place the gimlet through the hole in the form and drill all the way through the plank for the back, which has been thicknessed pretty much to the finished height, but is still just a flat board. Put your finger on the other side so you can feel when the point starts to emerge.

3) finish the back except for the final outline and purfling/edgework

4) take the ribs off the mold, attach the neck

5) place the ribs w/neck on the back using the center pins, place the jig on the ribs, slide the gimlet through the hole in the jig and rescrew the gimlet into the hole in the back that it made before.

Now the upper block, narrowest point, and lower block are all on the center line, and will stay there while glueing up.

This system works pretty well, but it doesn’t explain exactly the ventral pin thing. For one thing, the placement of the pin is not normally the narrowest point of the ribs. But maybe it could be that whatever jig they were using was designed to go wherever they decided the thickest point was going to be, as when you reinsert the gimlet there’s just not that much wood to hold it in place. It might also be handy to have a hole already where you’re going to measure the thickness from, so you don’t have to keep re-measuring it as you go.

I don’t strongly believe that this is the reason for the pins, but I think it’s possible that it’s something like this. my idea may be some primitive version of the actual model. thought I'd throw it into the mix.

Interesting thoughts, Kevin, which seem to have more correspondence with real craftsperson working methods, than some of the more "airy-fairy" theories.

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On 11/24/2020 at 7:40 AM, Kevin Kelly said:

There is another possibility that hasn’t been mentioned.

My own theory is that the hole may have to do with centering the c bouts. There was a long thread about this several years ago that I can’t find now, where I posted some pictures of a jig I used when I was making “baroque” violins. I can’t find any picture of that now, either, and the jigs are in a box somewhere, but it was just a piece of wood, about 50mm tall and 140mm wide, and about 7mm thick or so. There were two slots about 3mm wide and 32mm tall cut into it at the distance of the ribs, so the jig slipped over the ribs rather snugly at the narrowest point of the c bout. In the center of the piece of wood is a small hole that is drilled through, from top down.

I made the jig because I was trying to emulate the process that Hargrave described. The system worked well, but I ran into a problem - using locating pins keeps the upper and lower blocks on the center line, but the rest of the ribs are free to move around, and are hard to corral when it comes time to glue things together. I wanted to keep the center of the fiddle on the center line as well, especially the part between the upper eyes of the ff’s.

What I did was

1)  drill a hole on the center line of the form at the narrowest spot (same size hole as the one for the jig)

2) with the finished ribs still on the mold, place them on the back using the locating pins and take the first outline for sawing. At the same time, place the gimlet through the hole in the form and drill all the way through the plank for the back, which has been thicknessed pretty much to the finished height, but is still just a flat board. Put your finger on the other side so you can feel when the point starts to emerge.

3) finish the back except for the final outline and purfling/edgework

4) take the ribs off the mold, attach the neck

5) place the ribs w/neck on the back using the center pins, place the jig on the ribs, slide the gimlet through the hole in the jig and rescrew the gimlet into the hole in the back that it made before.

Now the upper block, narrowest point, and lower block are all on the center line, and will stay there while glueing up.

This system works pretty well, but it doesn’t explain exactly the ventral pin thing. For one thing, the placement of the pin is not normally the narrowest point of the ribs. But maybe it could be that whatever jig they were using was designed to go wherever they decided the thickest point was going to be, as when you reinsert the gimlet there’s just not that much wood to hold it in place. It might also be handy to have a hole already where you’re going to measure the thickness from, so you don’t have to keep re-measuring it as you go.

I don’t strongly believe that this is the reason for the pins, but I think it’s possible that it’s something like this. my idea may be some primitive version of the actual model. thought I'd throw it into the mix.

I do something similar, although I do it on modern instruments instead of just baroque.  I have mine positioned at the midpoint of the back, although the narrowest point of the c bouts would work also.  
 

A while back Neil Ertz mentioned he’d measured the width of several Del Gesus at the pin, and the width was close to identical on all of them at that point.  Considering the lack of consistency of widths on most cremonese instruments, DG in particular, that probably means more than nothing.

As for the pin left in the back, I just use the location of the c bout jig to position my graduating pin.  Very rarely are the widths off by more than .25mm at the pin, it usually pushes through to the outside a little bit. 

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On 11/24/2020 at 2:40 PM, Kevin Kelly said:

There is another possibility that hasn’t been mentioned.

My own theory is that the hole may have to do with centering the c bouts. There was a long thread about this several years ago that I can’t find now, where I posted some pictures of a jig I used when I was making “baroque” violins. I can’t find any picture of that now, either, and the jigs are in a box somewhere, but it was just a piece of wood, about 50mm tall and 140mm wide, and about 7mm thick or so. There were two slots about 3mm wide and 32mm tall cut into it at the distance of the ribs, so the jig slipped over the ribs rather snugly at the narrowest point of the c bout. In the center of the piece of wood is a small hole that is drilled through, from top down.

I made the jig because I was trying to emulate the process that Hargrave described. The system worked well, but I ran into a problem - using locating pins keeps the upper and lower blocks on the center line, but the rest of the ribs are free to move around, and are hard to corral when it comes time to glue things together. I wanted to keep the center of the fiddle on the center line as well, especially the part between the upper eyes of the ff’s.

What I did was

1)  drill a hole on the center line of the form at the narrowest spot (same size hole as the one for the jig)

2) with the finished ribs still on the mold, place them on the back using the locating pins and take the first outline for sawing. At the same time, place the gimlet through the hole in the form and drill all the way through the plank for the back, which has been thicknessed pretty much to the finished height, but is still just a flat board. Put your finger on the other side so you can feel when the point starts to emerge.

3) finish the back except for the final outline and purfling/edgework

4) take the ribs off the mold, attach the neck

5) place the ribs w/neck on the back using the center pins, place the jig on the ribs, slide the gimlet through the hole in the jig and rescrew the gimlet into the hole in the back that it made before.

Now the upper block, narrowest point, and lower block are all on the center line, and will stay there while glueing up.

This system works pretty well, but it doesn’t explain exactly the ventral pin thing. For one thing, the placement of the pin is not normally the narrowest point of the ribs. But maybe it could be that whatever jig they were using was designed to go wherever they decided the thickest point was going to be, as when you reinsert the gimlet there’s just not that much wood to hold it in place. It might also be handy to have a hole already where you’re going to measure the thickness from, so you don’t have to keep re-measuring it as you go.

I don’t strongly believe that this is the reason for the pins, but I think it’s possible that it’s something like this. my idea may be some primitive version of the actual model. thought I'd throw it into the mix.

In summer this year I was thinking about these strange pins/ pinholes and thinking about some of Roger Hargraves writings on ensuring the nailed on neck is correctly alligned and 'pivoting' the ribs assembly on the part finished back until things are lined up to establish the final outline.  I wondered if some kind of straight edge having a sharp pin in the middle engaging into the pinhole in the back  and some other pins  could have been used to line things up and hold things together when this was being done. I made this sketch of my thoughts

P1070616.JPG

Now I have been informed that these holes are usually all the way through, I think this must have had some really useful purpose. Perhaps the very small spike could have 'engaged' with the bench top and help stop this slippery assemblage from wriggling about, especially if a maker was working on their own.

Like some other commentors I believe these holes must have had a pretty important practical purpose but find it hard to believe repeated compass use would bore through or necessitate such a substantial hole. I can't help thinking that to make a hole all the way through and make such a blemish on a beautiful violin back would have been acceptable only if it served some important practical purpose?

As usual I freely admit I am only a novice violin maker and have a tendency to try look at things from a practical/ making standpoint and hope more knowledgable people don't mind me joining in with my thoughts

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15 hours ago, Andrew tkinson said:

Now I have been informed that these holes are usually all the way through, I think this must have had some really useful purpose. Perhaps the very small spike could have 'engaged' with the bench top and help stop this slippery assemblage from wriggling about, especially if a maker was working on their own.

Like some other commentors I believe these holes must have had a pretty important practical purpose but find it hard to believe repeated compass use would bore through or necessitate such a substantial hole. I can't help thinking that to make a hole all the way through and make such a blemish on a beautiful violin back would have been acceptable only if it served some important practical purpose?

When the dorsal pin can be seen from the outside it is never any larger than a pin hole. You have to look for it. In order for the pin to engage the bench top the hole would have to be much bigger than it actually is.

They certainly would have taken the time to do it if it didn't have a purpose, it's just that there is endless speculation about what that purpose might be.....

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I think we can safely say three things:

1) it's too small to have role of physically secure the plate to the bench or anything close to that.

2) too many examples poke thru for that not to notivated.

3) any explanation should show a benefit not just for the hole being there at all, but for it poking through in a small delicate way.

 

It would be very nice for people, particularly Bruce, but orhers also, to weigh in on several points:

1) Have you personally seen Amati examples where the hole seems to be missing?

2) Where the hole doesn't poke through?

3) Where the hole does not seem to correspond to the Maximum back thickness?

 

 

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6 hours ago, Bruce Carlson said:

When the dorsal pin can be seen from the outside it is never any larger than a pin hole. You have to look for it. In order for the pin to engage the bench top the hole would have to be much bigger than it actually is.

They certainly would have taken the time to do it if it didn't have a purpose, it's just that there is endless speculation about what that purpose might be.....

Occam's razor says my answer is the bestest.

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30 minutes ago, HoGo said:

One should also ask why Stainer used five of them. That somewhat rules out the thickest spot theory... And on other extreme Strad used none (or never drilled deeper than final thickness of back)

Not really.  As long as one is one the max, then the others mighy be just a different choice of where to measure the tapering.

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7 hours ago, David Beard said:

Not really.  As long as one is one the max, then the others mighy be just a different choice of where to measure the tapering.

But why would all the holes be so deep? It is often explained that the central hole is so deep because it was repeatedly used by compass/dividers to mark the thickness areas, but why would the rest of the holes along the back go through? What would they be used to mark?

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Reread the thread. People are suggesting that the compass point theory is insufficient even to explain the central mark.  Why would you so often push through the plate without some further benefit??

Seversl ideas were presented. One being that a deep hole let's you easily see the plate thickness.  And you even push a stick in to get something you can measure.

If that was the purpose for digging the center hole deep, Stainer might have applied the same idea at multiple points.

If you look at the existing Cremona artifacts, you'll see many kinds of calipers that might have helped measure plate thicknesses.  Many are metal, some are simple things made of wood.  And we don't which tools apply to which time periods.

I don't know how many folks have made replicas of the wooden calipers? I have. The end up being a little squishy.  It's hard to obtain an exact read off those calipers.  But, they're very good for feeling the direction of change.  You can find bumps in thickness easily, and direction of taper.  But it's difficult to determine exactly where your thickness is with these calipers alone.

Perhaps the Amatis felt comfortable just seeing the center thickness, then feeling out the taper.  But Stainer maybe wanted to see the thickness at more points.

But do we even know if Stainers extra points are also dug deep? 

Bur this is all just speculation.  And it will stay that way.  Someone would need to create a survey of such markings with sufficient accuracy and detail, and embracing a large number of instruments.   Otherwise we have enough information to entice all sorts of fanciful speculation, but not enough to test, affirm, or dismiss any of these ideas.

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14 minutes ago, David Beard said:

Perhaps the Amatis felt comfortable just seeing the center thickness, then feeling out the taper.  But Stainer maybe wanted to see the thickness at more points.

But do we even know if Stainers extra points are also dug deep?

That's what I suggested in the other thread as one possible use...

I think I misunderstood your quote about "measuring the tapering" versus "marking of tapering" which was mostly suggested in perevious posts or threads in the past. Two different things.

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  • 1 month later...

Here is just another idea about the taper. 

Could be for glueing in two steps . First the top is glued in the tapered area to the ribs. Then, after the glue has dried the rest is glued.  I wonder if it is possible to fine adjust with this approach the neck angle. This would mean the fingerboard is already glued when closing the instrument.

I didn't test it, so I have no idea if it really works.

 

 

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8 hours ago, Andreas Preuss said:

This would mean the fingerboard is already glued when closing the instrument.

Not possible because the instrument is purfled after the box is closed and the purfling goes under the F/B

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14 hours ago, Sapiens said:

Not possible because the instrument is purfled after the box is closed and the purfling goes under the F/B

Rats! You are right. 

Though in theory you could cut just the groove under the fingerboard, glue the top as I described and then make the purfling on the finished body. 

Doesn't sound convincing....:unsure:

 

 

 

 

 

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On 1/2/2021 at 4:38 PM, Three13 said:

It’s worth looking at the unaltered Andrea Guarneri tenor and Storioni small violin at the NMM in order to see how they handled purfling under the board, I think.

True, but also loads of examples where the purfling goes further away under the fb 

It’s worth remembering that both finishing the outline and cutting the groove for purfling were done after closing the box. Wouldn’t make much sense to glue the board before these steps.

I guess makers were more or less fussy about the look of purflings under the fb.

 

22 hours ago, David Beard said:

Also. Neck angle a non issue for the old makers, since they used a wedge system

Would you develop a bit more on that? I tend to believe despite the wedge system, neck angle is crucial.

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