Thicknessing. When to stop?

[tango]

Hi
I am thicknessing a violin back up to achieve a "F" or "F#" note when tapping the plate with knuckles.
I just arrived at "F" but some zone is thick (low bout 3mm) and I don't feel enough elasticity. I guess  that I must continue the thicknessing, in spite of go far from F note. The note is clear.
 The weight is 102 gr. Don´t know the pg of the wood (peso específico in spanish)
 Thinking that the central cross arch is a little low (14mm) I think it would be better to leave a little  thick. But how much I asked to myself.

So the question is.
When to stop Thicknessing?
Any opinion would be apreciated.

Thanks in advance 
Tango

[Jim Bress]

Hi Tango,

I have been taught to thickness by flexing and sustain by way of "here, feel this".  Which I don't know how to put into words.  However, I still look to have thickness, M5, and weight in a reasonable range.  For me greater than 120 g is too high, M5 between F# (ish) and Fb (ish), 3mm in the lungs for me would be ok with the low arch.  In other words, with the information given, I ask myself if I have any reason to expect that taking more wood off will make the plate better (I left the quotes off on purpose).  In this case, I would not be able to argue (with myself) that removing more wood is better than leaving the plate as is.  Therefore, I would stop.  There is always the option to take more wood off after the violin has been finished and had time to settle in.  I hope that helps.  Stand by for the more experienced makers to give better advice. 

-Jim

[duane88]

Ah, the question...I don't like to go below 4mm in the center of the back and don't like to go below 2-2.2 at the ends, regardless of flex or tone. I don't tune plates, but I do make a record of what the pitch is. Really, tuning plates only works when you have chosen the correct density piece of wood for what you want the note to be.

So, for me, the lower limits are: 4mm in the center of the back, 3.3-3.5 at the edge of the c-bouts, 2-2.2 at the thinnest in the flanks. I'll make an exception for highly arched models, although I don't really ever want to make any part of the plate less than 2.0mm on purpose, top or back. If it is too stiff and heavy at that point, it is better to simply discard the back and choose a different piece of wood and go forward with the new plate.

edit: one friend wants his backs to be under 100gm, I've heard violins with 120gm backs that sounded just fine.

[Ken_N]

When I was thicknessing the back of my Archtop guitar, the weight dropped tremendously, (500 to 325g.) but the tap tone didn't.   It even seemed at some point to raise up, and get clearer with more sustain.

Could it be that since my inside arch is already there, and finished, all I have to do is get rid of the wood on the outside that is hindering the vibrations?  I rough violins and violas out to about 5-6 mm thick, (8 or so on the center of the back, if the stock is tall enough).  It seems that if I was looking for a number, I could decide early on if the wood wanted to have a higher arch, or could be fine with an even lower arch, and see what it does for it.

I could even try for high, and low ones, and different kinds of wood, just to see what it does.

It might not do anything; maybe the wood is just what it is.  I haven't tried making 3 or 4 at the same time with the same kind of wood, and the same pattern.

I finish the recurve after gluing up, so I don't know what the final tap tone is.  F# or so and less than 120 grams is a usual starting point.  Some wood won't make F# ever.  Some can be 105 grams and at G before gluing on, but they still need the recurve.

In the end, I don't think the numbers mean much.  The tap tone and weight just gets you in the ballpark.  You have to decide where to stop, and what your arches look like.

[tango]

This is the first time i made the archings with CURTATE CYCLOID software and not by eye as I used

[Don Noon]

I have had two violins that won the top tone award at the VMAAI competition.  Both were made on the same form.

One had a back 93g and taptone at F#  (362 Hz)

The other had a back 107g and taptone between E and F (340 Hz).

Based on these results, I'd  say you're in the range that can work.  You could also take out some more wood if you  feel so inclined, and still be within the workable range.  But being within my range doesn't mean it will work, and being outside of my range doesn't necessarily mean it won't work.

[jezzupe]

You're asking a question that everyone asks themselves until eventually one stops asking themselves that question.

I always like to answer this question with "when it's done" or "you know you got it if it makes you feel good"

but ya somewhere between E and F# is usually about right, lower than that your getting kinda thin and flabby or have some funky material, higher than F# your probably pretty stiff, heavy and thick....in general, most times, but not always, maybe, but usually, something like that, you get the idea.

[Don Noon]

On 9/19/2019 at 4:51 PM, tango said:

When to stop Thicknessing?

My usual practice is to stop at some point after I should have. 

[tango]

I am inclined to take off more wood looking for more flex. But not surpassing "E" note.
Thanks all for spread your knowledge and help me to think.

Regards

Tango

[Kae Han]

On 9/21/2019 at 10:48 AM, jezzupe said:

...

but ya somewhere between E and F# is usually about right, lower than that your getting kinda thin and flabby or have some funky material, higher than F# your probably pretty stiff, heavy and thick....in general, most times, but not always, maybe, but usually, something like that, you get the idea.

Is there a rule of thumb for viola also?

[Delabo]

As a supplementary question it would be interesting to know when this idea of tuning plates developed ?

The tuning fork was not invented until 1711 so how would Amati \ Stradivari etc have tuned their plates ?

Could they have been born with the ability to hear perfect pitch and just tapped until what they heard sounded good ?

 

[Emilg]

2 hours ago, Delabo said:

As a supplementary question it would be interesting to know when this idea of tuning plates developed ?

The tuning fork was not invented until 1711 so how would Amati \ Stradivari etc have tuned their plates ?

Could they have been born with the ability to hear perfect pitch and just tapped until what they heard sounded good ?

 

I think it is not about some absolute pitch, but rather a design parameter where the plate has reached a certain stiffness to weight ratio. When the plates are glued the M5-mode (taptone) will be gone anyway, but there seems to be a relation/correlation between M5 and B1-modes, which are more important.

[Andreas Preuss]

For the back stiffness is more important than weight. Furthermore I started to watch the x mode (cross stiffness) more  than the ring mode. (Lengthwise stiffness) 

when to stop? I guess every maker established his own parameters.

 

[Don Noon]

1 hour ago, Emilg said:

...there seems to be a relation/correlation between M5 and B1-modes, which are more important.

The correlation is not that great, and...

Has there ever been a study showing player preference for any particular B mode frequency?  I am not aware of any... there just seems to be a tendency to latch onto a value that is held as a goal, perhaps a result of Hutchins' teachings.

[MANFIO]

In order to keep things a bit "objective",  I  keep notes about the weight of the shaped (unscooped) top and back, and of the finished plates so that I can negotiate thicknesses in a more consistent way. 

[Emilg]

53 minutes ago, Don Noon said:

The correlation is not that great, and...

true, i think you also tried the formula/spreadsheet on platetuning.org for predicting B1's and found it did not work very well. However, somehow B1- is affected bij the top and B1+ by the back wasn't it? (or v.v., i always forget)

53 minutes ago, Don Noon said:

Has there ever been a study showing player preference for any particular B mode frequency?  I am not aware of any... there just seems to be a tendency to latch onto a value that is held as a goal, perhaps a result of Hutchins' teachings.

I think (like you also mentioned) they should be around the "right places" and perhaps not too weak or strong. My idea is that A0, CBR, B1- and B-1 just support the lower register and preferably not causing wolfyness. I think you mentioned every mode spreads around 5 semitones?

[MANFIO]

It is always good remembering, also, that the archings are fundamental for sound.

 

Perhaps 95% of Del Gesù violins were regraduated and they continued sounding good.

 

It is good having in mind the two extremes in thicknesses, and what they can cause.

 

If the plates are too thin you will have hollow and unfocused sound,  the basses will sound bad from the very beggining, wolves in the high positions of the G and D strings, the instrument will choke under the bow in fortissimos.

 

If you leave the plates too thick, it will be hard for the player to modulate the sound, it may sound metalic, the dynamic range may be too narrow, the instrument will not respond well to the bow.

 

 

 

[Don Noon]

46 minutes ago, MANFIO said:

It is good having in mind the two extremes in thicknesses, and what they can cause.

If the plates are too thin you will have hollow and unfocused sound,  the basses will sound bad from the very beggining, wolves in the high positions of the G and D strings, the instrument will choke under the bow in fortissimos.

If you leave the plates too thick, it will be hard for the player to modulate the sound, it may sound metalic, the dynamic range may be too narrow, the instrument will not respond well to the bow.

These I think are the important issues. 

I notice there was no mention of the B mode frequencies being too high or too low 

So although the B mode frequencies undoubtedly will be inversely  correlated with plate thickness on a given instrument (unless the graduation pattern is altered radically), it is the playing characteristics that matter, not the B frequencies... and once you have different wood and arching, the relation between the thickness, B frequencies, and playing characteristics can be completely different.  As usual, it's complicated.

[jezzupe]

8 hours ago, Kae said:

Is there a rule of thumb for viola also?

Meh' I think I would say , "a little lower" . I don't really put much into the "marimba bar" frequency at this point in a build. A chunk of wood that is "this" big and that is "this" thin will ring around "this" or "that" pitch.

Now I suppose if we were making marimbas out of violin shaped wood bars any of this might make more sense, but I haven't found any holy grail in this "general" information and find that target thickness and over all dimensions of the plate pretty much yield similar data as at that point if your tapping and hearing a pitch all your doing is tapping a marimba bar, one that barring extreme material properties seems to act the same across the board as long as the dimensions fall into a certain range.

It's all very arbitrary information that at this point is nice to know, but nothing I pay much attention to other than it helps to have some benchmark note to shoot for when doing the final shavings.

At this point I've pretty much blocked out "lalalala" any "scientific "  information as it relates to "using" it  in anything I build, it's fun to discuss and think about things, but I find "data" does zero for me these days and generally prevents me from, you know, work.

I'm convinced at this point that no one will be coming up with a "do xyz procedure " and you will have a great sounding instrument, and I am also convinced that the only way to build instruments that sound great is to simply do it as many times as you can before you die and that everything you will need to know will make itself known along the way.

[David Burgess]

17 hours ago, Delabo said:

As a supplementary question it would be interesting to know when this idea of tuning plates developed ?

The tuning fork was not invented until 1711 so how would Amati \ Stradivari etc have tuned their plates ?

Weren't there church and tower bells in Cremona?

[Andreas Preuss]

21 hours ago, Delabo said:

As a supplementary question it would be interesting to know when this idea of tuning plates developed ?

The tuning fork was not invented until 1711 so how would Amati \ Stradivari etc have tuned their plates ?

Could they have been born with the ability to hear perfect pitch and just tapped until what they heard sounded good ?

 

Savart was the first scientist who tried to solve 'Stradivaris secret' by looking into Chladni patterns of the loose plates and reportedly he could find some basic rules of plate tuning. So thereafter violin makers started to use the idea. Vuillaume who apparently provided Savart with loose plates of Stradivari and Guarneri (!!!) was maybe the first maker who tried to tune the loose plates 'scientifically'.

However I am sure that other makers of the past must have noticed that if plates are thin enough the get a sort of ring when tapped. 

You dont need a tuning fork to have a reference. Kantuscher in Mittenwald used a Guitar. He would tap the plate in front of the guitar and listen how loud the guitar would resonate. 

IMO most makers are focused too much on the pitch of the tapped tone. I think it is more useful to listen to the quality of the tapped note, is it long or short and do I get the same quality tapping in various locations.

[Jim Bress]

I've always disliked the use of scientifically in this context.  As do many others that will place quotes around "scientifically".  Quantitative may be a good substitute.  As in, relating to, measuring, or measured by the quantity of something rather than its quality.  For example, I inflate my car tires using a quantitative method (tire gauge).  Which is certainly not considered a scientific method.  Sorry for the soap box commercial break. 

[jezzupe]

7 hours ago, Jim Bress said:

I've always disliked the use of scientifically in this context.  As do many others that will place quotes around "scientifically".  Quantitative may be a good substitute.  As in, relating to, measuring, or measured by the quantity of something rather than its quality.  For example, I inflate my car tires using a quantitative method (tire gauge).  Which is certainly not considered a scientific method.  Sorry for the soap box commercial break. 

ya but just think of all the science that went into the making of that pressure gauge,both the actual device itself as well as the principles behind the math that make it usable, I do it the old fashioned way and just kick them and hope for the best 

[Marty Kasprzyk]

Keep thinning until the wolf notes just start to be a problem. That gives the maximum sound output without causing big difficulties.

[Don Noon]

1 hour ago, Marty Kasprzyk said:

Keep thinning until the wolf notes just start to be a problem. That gives the maximum sound output without causing big difficulties.

If you mean "maximum sound output for a constant forcing function", then I'd agree.  However, I think that energy, not just force, matters once you consider the realities of the violinist and the bow.  Thin (low impedance) plates remove energy from the string more quickly, requiring more bow speed to keep the string operating in the Helmholtz mode.  The player might run out of bow trying to play a long, loud note, and it might be more difficult to play softly.   I think there's a good reason to go thicker if the player has a strong bow arm, and/or if wider dynamic range is desired.