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I am currently making my second violin and have graduated the top plate to 2.9mm in the top and bottom bouts and 3.3mm in the centre between the C bouts.  The thickness is ~3.5mm just inside the gluing platform all the way around.  The overall plate weighs 89g which I believe is high.  Attached is a photo of the Chladni patterns of modes 1, 2 & 5 along with the respective frequencies.  Mode 5 is currently at 353Hz.  My aim is to keep the modes in octaves and for mode 5 of the back plate within a tone of the top mode 5.

Question:  How should I proceed with graduating the top?  Should I be aiming to drop the weight and if so what is a realistic target  as 0.2mm will reduce by  2-3grams

Happy New Year

P.S the back plate has been graduated to a starting point for plate tuning as follows:

Weight 129g

Mode 1  114Hz

Mode 2  182Hz

Mode 5  376HzModes.thumb.png.a5e6ed733c4c858955b90e6f0f805411.png

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5 hours ago, Paul McClean said:

I am currently making my second violin and have graduated the top plate to 2.9mm in the top and bottom bouts and 3.3mm in the centre between the C bouts.  The thickness is ~3.5mm just inside the gluing platform all the way around.  The overall plate weighs 89g which I believe is high.  Attached is a photo of the Chladni patterns of modes 1, 2 & 5 along with the respective frequencies.  Mode 5 is currently at 353Hz.  My aim is to keep the modes in octaves and for mode 5 of the back plate within a tone of the top mode 5.

Question:  How should I proceed with graduating the top?  Should I be aiming to drop the weight and if so what is a realistic target  as 0.2mm will reduce by  2-3grams

Happy New Year

P.S the back plate has been graduated to a starting point for plate tuning as follows:

Weight 129g

Mode 1  114Hz

Mode 2  182Hz

Mode 5  376HzModes.thumb.png.a5e6ed733c4c858955b90e6f0f805411.png

If you thin any x areas between the node lines the resonance frequency goes down and if you thin the areas outside the node lines the frequency goes up.  For your mode 2 example:    )x(    and  x)(x

By alternating these thinning areas back and forth you can greatly reduce the plate's weight while maintaining the same resonance frequency.  

 

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6 hours ago, Paul McClean said:

My aim is to keep the modes in octaves and for mode 5 of the back plate within a tone of the top mode 5.

Why?  Seems like a lot of effort with no proven payoff.

The weights DO look high, and mode frequencies also correspondingly high.

IMO use a reasonable graduation pattern and take it down to a reasonable weight with reasonable taptones... the last being not that big of a deal.

Best use for glitter patterns:glitter.png.5b678f2171aced89a79133263fecd524.png

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7 hours ago, Paul McClean said:

I am currently making my second violin and have graduated the top plate to 2.9mm in the top and bottom bouts and 3.3mm in the centre between the C bouts.  The thickness is ~3.5mm just inside the gluing platform all the way around.  The overall plate weighs 89g which I believe is high.  Attached is a photo of the Chladni patterns of modes 1, 2 & 5 along with the respective frequencies.  Mode 5 is currently at 353Hz.  My aim is to keep the modes in octaves and for mode 5 of the back plate within a tone of the top mode 5.

Question:  How should I proceed with graduating the top?  Should I be aiming to drop the weight and if so what is a realistic target  as 0.2mm will reduce by  2-3grams

Happy New Year

P.S the back plate has been graduated to a starting point for plate tuning as follows:

Weight 129g

Mode 1  114Hz

Mode 2  182Hz

Mode 5  376HzModes.thumb.png.a5e6ed733c4c858955b90e6f0f805411.png

Hi,

The plates are heavy and stiff like some mass produced chinese instruments. I have regraduated a few of these as part of a «research program». Octave tuning is not a good idea because you end up with too thick central parts of the top and probaly also the back plate. I would look more on mode 2 than any of the other and get the top plate weight below 70 g, even down to 65 g or lower without the varnish, and with bar and ffs. I would varnish the insturment before the last «plate tuning». I would aim for a mode 2 frequency around 145 Hz and I would remove the platforms in the ends of the plate which makes the mode 2 frequency too high in relation to mode 5. In normal instruments the relation between the mode5/mode2 frequenciues are around 2,2 to 2,3 with average Strad or del Gesu graduations, pretty even in the tops.

I think the back plate could work better around 100g or even a little lower with the varnish on. I agree that the back can have a little higher tap tones than the top. I think graduations and the weight is more important than the mode frequencies. There are of course also other factors that matters as arching, wood peroperties etc.

There is no evidence I know of in the violin acoustics literature or research that support the idea of using octave tuned plates. A double bass professor friend liked the violin octet double bass, though. Maybe it works better for violas. Hutchins played the viola.

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1 hour ago, Don Noon said:

Best use for glitter patterns:glitter.png.5b678f2171aced89a79133263fecd524.png

LOL, good one, Don!

While there were some who tried it once upon a time, I am not aware of any successful maker who uses glitter (Chladni) patterns on free plates any more.

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Really appreciate the feedback so far guys.  Looks like I need to drop the weight by at least 19g.  Do you think that is achievable ok given I'm currently at 2.9mm in the upper and lower bouts and 3.3mm in the middle? How thin should I target?

Also, the edges inside the gluing platform are 3.5mm. It is difficult to thin here without producing a steep concave slope.  Any advice on the thickness I should target?  The thickness at the purfling is 3.5mm and 4mm at the edge so fluting is quite shallow.

 

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It looks like the platform at the bottom block could be contoured, particularly on the bass side.  I think most makers don't do the full platform there.

The Sacconi pattern that I've seen gives 2.4mm for most of the top, with up to 2.7mm around the FF's, and a spot for the post.  That would get you down near 70g.  A lot of Strads are even thinner than that, but I wouldn't want to go there for a 2nd build.  Deeper fluting at the purfling seems like a good idea.  It would be good to know the density of the wood to guess where things might end up...  but given what you have so far, your wood is most likely on the dense side, so thin-ish graduations might not be out of line.

I wouldn't do any more graduations until I AT LEAST fluted the FF's on the outside, or make sure you leave a lot of thickness where the fluting will be done.  I made that mistake on my first violin, and the F wings had to be left pretty featureless.   I prefer to cut and flute the FF's after graduating down to ~6mm everywhere, just to be safe, and to know where things really are.

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Does the plate feel flexible?  Try flexing and twisting the plate a little and see what it feels like. 
You don't want it to be floppy but if it feels overly stiff you can probably bring it down under normal grads. 
It's probably the furthest thing from a measurable scientific approach but I've had much more success just feeling the plates with my hands than trying to match modes. 

 

 

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I have tried objective measurements of plate stiffness as a guide, and it seemed even more questionable than tap tones.  I'm sure my hand-flexing would be even worse.

I would just watch M5, and think about quitting if it dropped to near 310 Hz... with everything done, FF's cut, but no bar.  Or if the weight dropped below 60g, which seems unlikely for this wood.

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Thanks for all the tips above.  I was working on the lower bout today graduating to an even 2.7mm.  However the weight only dropped by 3g down to 86g.  The middle bout is still around 3.2mm and the upper bout 2.8mm so I will work on them next but I think at the rate the weight is dropping I will be lucky to get under 80g even if I graduate to 2.4mm in the upper and lower bouts.  I have already marked and fluted the f holes so don't need to worry about leaving extra thickness there.  I think the plate is 1 mm too long and 1mm too wide as the overhang is closer to 3mm instead of 2.5 but I was leaving extra for when I work on the edges.  I don't think that would attribute to a lot of weight though.

So far as contouring the platform at the bottom block do I just do this  on the bass side or more on the bass side than treble?  I assume the platform at the top block should be left alone for strength?  How does this affect the tone?  I would love to see a photo if anyone has one.

 

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From here it doesn’t seem  quite right, I would expect to be closer to 400 or above at this point ,,I would do exactly as Don said, get the f-s finished on the outside,, but I wouldn’t touch the Saconni plateaus to get the weight down. Weight at the end of the plate does not matter at all, there are chin rests and necks attached there any way. Right now they are producing a smaller vibrating surface area, it is actually the weight of that ,,related to the stiffness that matters, not the weight of the entire plate, though that is how it is  normally measured. Removing mass from the center will help, but how stiff is it?

What we really need to know is the height of the arch to make sense of it in any reasonable fashion. What the arch looks like also matters, also a close up of the wood, might give some clues.

Is it 14,,16,,17,,? It makes a huge difference.

For now, I would leave the ends, and leave the c-bouts no thinner than 3.5 clear up to the upper eyes of the f’s, straight to the upper corners. This can be taken down later as necessary. Some times Strad left eyebrows above his f’s, sometimes not, saving this area for last, I find to be a nice option to get things really dialed in.

. Keeping a reserve of stiffness here can help save mediocre wood, and still end up with a halfway decent fiddle.

I usually start with 3 in the channels of the upper and lower bouts, and  end up from 2.6-2.8

. Run the inside straight out to the glue surface of the linings, remove the thickness of the channel on the outside.

Leaving the ends, and the c-bouts thick for now will give you  a few more options if the wood is sub-par,,,,(my guess)

And Oh by the way,,

Have Fun!

 

Notice that the second arch is reverse graduated and thick in the c-bouts,,

bottom photo shows straight lines to the edge on the inside.

1167856519_amatiDGarching.thumb.JPG.0532527ab9f2f8705377756ef42d7e1e.JPG1804341806_bassbaratwidestpartoflowerbouts.thumb.JPG.68daef03081f4f61a5ebf25fe2b4be27.JPG

 

 

 

 

 

 


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In progress top (0.51 density, arch height 18 mm)

As Evan wrote, it should be around 400 at that stage.

You can't expect tuning to desired frequencies at the stage when hollowing out. You have to know the wood so you get the right height and shape first. Only then you can get what you want.

 

Top    
weight M2 M5
117 262 459
110 236 451
105 220 442
100 209 434
95 193 416
90 178 403
85 166 387
80 157 365
75 153 355
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I calculated the density from a piece I cut off the wedge before splitting and it is 0.48.  With my arching height of 15.7 does that influence the final graduations I should be targeting?  Although the wood is dense the tap tones seem lower than expected and I don't think the wood is noticeably stiff.

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On 1/2/2021 at 7:48 PM, Don Noon said:

Why?  Seems like a lot of effort with no proven payoff.

The weights DO look high, and mode frequencies also correspondingly high.

IMO use a reasonable graduation pattern and take it down to a reasonable weight with reasonable taptones... the last being not that big of a deal.

Best use for glitter patterns:glitter.png.5b678f2171aced89a79133263fecd524.png

Do you mean the patterns are no use and tap tones are enough or I am missing something? :-))

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So I have continued to graduate as suggested above.  Both the upper and lower bouts are at 2.5 mm graduating into 3mm in the centre and 3.2mm at the sound post area.  The weight is now 82g.  I calculated the density at 0.48.  Chladni patterns are similar to the above (without the chicken ;).  Modes are now as follows:

Mode 1    79Hz

Mode 2    154Hz

Mode 5    334 Hz

The plate feels flexible but not floppy, firm but not stiff.

 

Should I continue to graduate further and try to reduce weight more or should I cut the f holes and fit the bass bar??  Would love to hear your suggestions.

 

PS.  I play in an  orchestra and have had a few professional players try out my first violin and they were impressed by the evenness of tone and playability, but it is heavy and does not project well.  My goal is to improve on the first and produce the best tone I can.

 

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Your wood seems to be very heavy. So from this point it is probably impossible to go down under 70g with bass bar. For heavy wood I wouldn't hesitate to make a 18-20mm high arching.

I am wondering if another mistake isn't somewhere else. Just at the border line of the block plateau the arch curves inside very rapidly.  How thin is it there? Especially in the stressed area around the top block you need meat.

For the modes I Can't say anything. Somehow I have given up to see there any significant measure whether or not the violin will produce a good sound. 

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7 hours ago, Sapiens said:

Do you mean the patterns are no use and tap tones are enough or I am missing something? :-))

I can see no logical reason to use glitter patterns on free plates, so I don't.  Even taptones don't seem to indicate much, other than general stiffness range.  They are easy to measure, so I do... but don't "tune".

5 hours ago, Paul McClean said:

So I have continued to graduate as suggested above.  Both the upper and lower bouts are at 2.5 mm graduating into 3mm in the centre and 3.2mm at the sound post area.  The weight is now 82g.  I calculated the density at 0.48. 

10 minutes ago, Andreas Preuss said:

Your wood seems to be very heavy. So from this point it is probably impossible to go down under 70g with bass bar.

All indications are that you have extremely dense wood, so the challenge is to find a reasonable stiffness/weight value.  70g with bass bar looks like a reasonable goal to me, but it depends on how stiff the wood is.  My method is to cut the F holes and then see what the mass and taptones are, and then do the final graduations.  I don't have much data about graduations and taptones without the FF's... except for the back, of course.

 

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6 hours ago, Andreas Preuss said:

Your wood seems to be very heavy. So from this point it is probably impossible to go down under 70g with bass bar. For heavy wood I wouldn't hesitate to make a 18-20mm high arching.

I am wondering if another mistake isn't somewhere else. Just at the border line of the block plateau the arch curves inside very rapidly.  How thin is it there? Especially in the stressed area around the top block you need meat.

For the modes I Can't say anything. Somehow I have given up to see there any significant measure whether or not the violin will produce a good sound. 

The thickness just inside the border of the top block platform is 3.5mm graduating quickly to 3mm for about 10mm and then into 2.5mm and n the upper bout. Is 3.5mm ok? I assume it is steep die to the arching on the outside.  Thanks for the comments...I'm learning a lot

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