Violin #5 - Strad Body modes

[Don Noon]

I now some on the forum find the discussion of tap tones rather annoying and irrelevant. How then do these makers know when to stop thinning the plates and what thicknesses to use and where. ...Seems like tap tones are a quantitative guideline ...

The key word is GUIDELINE.  I think taptones are fine for that, and I definitely use them as such. 

The problem I see is a tendency to go nutty about exact numbers, ratios, and possibly doing odd things to the graduations to achieve these numbers. 

 

I don't know how to track back plate coupling frequence on a finished violin, but you should match the top to the calculated free back plate M5 from that coupling frequency.

 I know I'll regret this... but what the heck is a "coupling frequency"?

[Joe Swenson]

The key word is GUIDELINE.  I think taptones are fine for that, and I definitely use them as such. 

The problem I see is a tendency to go nutty about exact numbers, ratios, and possibly doing odd things to the graduations to achieve these numbers. 

I completely get that. And the idea of making the the measurements on the rough slabs a determining whether you have a good piece of wood before carving seems like the most important first step so when graduating you don't have to fight to get good results. It seems you can only force the tap tones only so far towards any given target for a given piece of wood. After that you're fighting against what the wood is willing to do. They definitely seem to go quickly toward their final values and stabilize upon further graduation. Then I would imagine you invite all the little demons tones in which cause you to tear your hair when the instrument is finally played.

Cheers,

Joe

[Peter K-G]

The key word is GUIDELINE.  I think taptones are fine for that, and I definitely use them as such. 

The problem I see is a tendency to go nutty about exact numbers, ratios, and possibly doing odd things to the graduations to achieve these numbers. 

 

 I know I'll regret this... but what the heck is a "coupling frequency"?

No you won't regret It's the M5 when plate is glued to the ribs 287 for back plate on ribs for this one

http://www.maestronet.com/forum/index.php?/topic/327921-violin-5-strad-body-modes/page-8#entry585960

[Don Noon]

 It seems you can only force the tap tones only so far towards any given target for a given piece of wood. After that you're fighting against what the wood is willing to do.

 

I must be too much of a pacifist to get into fighting with the wood.  I do track the M5 taptone and mass as I'm thinning it... and then stop when I get into the right neighborhood.  Lighter wood usually prefers to live in the higher taptone, lower mass neighborhood, and heavier wood in the lower taptone, heavier mass neighborhood.   That's just the way it is.  You could do funny stuff, like thinning the edges and the center of a heavy plate to get the weight down and M5 up, but why?  The M5 mode disappears when you glue everything together... agan, it's just a guideline, not a goal.

 

I could see that anyone trying to reach a specific M5 and specific M2 and specific weight could be in for a fight with the wood.  You might get your numbers, but the wood won't be happy about it.

[Peter K-G]

Here is a topic about cleated center seams:

http://www.maestronet.com/forum/index.php?/topic/312213-cleated-center-seams/

 

I'm happy with cleats, dont like to have unglued back plate seams. It's a bad thing

 

I have woundered if the Cremonese masters used another glue for the seams, read somewhere about casein glue.

[Marty Kasprzyk]

 

The problem I see is a tendency to go nutty about exact numbers, ratios, and possibly doing odd things to the graduations to achieve these numbers. 

I don't think thinning in "odd areas" is necessarily bad. Jeff Loen's book "Thickness Graduation Maps, Classic Violins, Violas, and Cellos" shows many examples of thinning plates in "odd" areas resulting in highly non uniform and unsymmetrical thicknesses maps.  Some of these might be good sounding instruments.

[Peter K-G]

If you look at my graduations on both back and top you will find there is nothing odd about them. On the contrary they are pretty much like average Strads

[Peter K-G]

Before closing the soundbox, and the fast way to do it

 

 

 

I decided to put some cleats on the top also, just in case.

[Peter K-G]

Working on edges and finishing purfling channel, really want to master this. This is the stage that I like least!

Soundbox without neck and soundpost

A0 = 241

A1 = 462

[Peter K-G]

"The violin cannot be brought to perfection without the strong heat of the sun"

I nice tan can't be wrong.

 

 

 

With soundpost:

 

weight = 228 g

A0 = 272

A1 = 463

C2 = 408

 

I can already hear how awsome it's going to sound

[Peter K-G]

This violin is about to get the neck attached. A very strong cup of Early Gray, took all the whiteness away.

 

 

 

Anyone has an opinion on gelatin as a sealer?

[Patrick KREIT]

The edges and the corners are nicely rounded. I like them very much.

You just have a little problem with an inappropriate knife that chips off the tip of the lower wing. Otherwise, it’s fine!

 

www.kreitpatrick.com

[Peter K-G]

I will certanly buy some more tools for my next violin, especially knifes. Until now I have mostly used one or two small knifes and used sandpaper to fix the ugly cuts. I carved my first scroll only with one of the small knifes. I like carving wood and have nothing against doing work. Now I want to speed up the process and start learning the profession the "right" way.

 

(ps. I already master The Sound of Stradivari, couldn't resist  )

[Peter K-G]

You only get one shot at attaching the neck so it's always an exciting moment. Got lucky this time also, 27 mm at bridge following a temporary finger board. The scroll is sideways right in the middle, but I had to trim down the heel to 18 mm for it to be in the middle of back plate joint.

At this stage I usually test the virtual body modes without and with a temporary fingerboard (430 Hz) attached with Blu tack and tape. This is not how Patrick describes the procedure in the book but I want to move on to varnishing.

 

This method is not valid but I use it as a quick test to se if i should string up the violin in the white or not ->  I will not.

I'm going to play the finished violin in two weeks

 

Holding the violin with one finger under the scroll, knocking on the opposite side where the upper saddle will be:

 

MC ~ 5%

 

Without fingerboard:

 

A0 = 270

A1 = 461

B0 = 248

B1- = 455

B1+ = 570

C2 = 403

 

With temporary fingerboard:

A0 = 270

A1 = 461

B0 = 263 (will be around 273 with a finished 430 Hz fingerboard)

B1- = 446

B1+ = 550  (Violin #4 was 538 at this stage it ended up around 526)

C2 = 403

 

[Patrick KREIT]

The figures are exactly as determined at the outset.

If you do not want to set up the violin in the white, before varnishing, you must install a sound post and wait a few days before taking a reading of the B1+ mode frequency: it can rise more than expected. Then install a chin rest to see how much the B1- and B1+ mode frequencies drop. You must not lose all the work you have invested on a whim!

 

Haste makes waste.

 

www.kreitpatrick.com

[Peter K-G]

Okay, I more rational now in the evening   It's no hurry. The Readings are with soundpost installed.

[Peter K-G]

The figures are exactly as determined at the outset.

If you do not want to set up the violin in the white, before varnishing, you must install a sound post and wait a few days before taking a reading of the B1+ mode frequency: it can rise more than expected. Then install a chin rest to see how much the B1- and B1+ mode frequencies drop. You must not lose all the work you have invested on a whim!

 

Haste makes waste.

 

www.kreitpatrick.com

This post saved my work! If I had carried on to varnishing I would have ended up with a finished violin with B1+ around 560 Hz. I was about to take the day of and start the varnishing process. This is why action research involving other people on a forum works so well. Late yesterday the virtual B1+ was up to 575.

The back plate had/has not fully stableized yet. We have had +25 C for 7 days here now and humidity is 40%.

I know there is a lot of people questioning all this (nonsens), but there is a "sparkling" sound coming out of the soundbox now. I have sanded the back evenly without lowering the height. The frequncy was 560 after that. It's 562 now. B1- is 457, it did not go down by sanding the back plate.

[Peter K-G]

New Discovery - Our homes in Scandinavia are becoming violin killers!

 

I took of strings, pegs and tailpiece of Violin #1 to compare with this one - It had a long 7 cm crack in top plate joint, starting from the bottom sadle. I also talked to a senior violin maker nearby, he have had 3 incidents with cracked tops lately. He have made nearly 100 instruments.

 

New energy saving regulations forces us to install Heat recovery ventilation systems, costs a fortune and gives us all kinds other problems too, increased allergy, dry skin...

 

 

With this system when the temperature outside drops under -15 C, the humidity gets near 0% with an inside temp of +23 C

 

So now we also have to by humidifiers, no wonder it's a sparsely populated area.

This winter have also been unusually dry.

[Patrick KREIT]

Gluing the fingerboard on lowers the B1+ mode frequency: this is why it must be installed temporarily, but nonetheless properly, using 4 or 5 little dots of light glue on each side of the neck, in order to learn the true frequency of mode B1+.

 

To lower the B1+ mode frequency, you must not sand the entire surface of the back plate. If you are not sure of what you are doing, draw a circle on the extrados having a diameter of 2 cm centered on the sound post and leave that area untouched. Sand all the rest of the center, then wait a few days and check the frequency again.

 

What occurred was entirely predictable. Tuning with 0% MC on wood that had been heated made the edges curl up. The back plate was not at its true frequency. After regaining moisture, the arch yielded to the sound post’s pressure, thus increasing the arch height and hence raising the frequency. You experienced and discovered this phenomenon yourself by wetting and drying the back plate.

 

Try to lower the  B1+ mode frequency without a chin rest to 550 Hz, for the wood is not at 0% MC. Once it has reached 0%, the B1+ mode frequency will rise by 5 to 10 Hz. In addition, take a reading of the B1+ mode frequency with a chin rest: this frequency generally drops by 5 to 10 Hz.

 

You will then have a back plate that weighs 95 g, as expected.

Sanding the back plate does not lower the B1- mode frequency.

Your B1- mode frequency (457 Hz) is appropriate, but borderline.

The B1- mode frequency never rises after installing the sound post, when the violin is set up in the white. It rises only when the moisture content in the wood decreases. This frequency can fall slightly due to the pressure of the strings which slightly lowers the height of the arch when the back plate yields a little.

 

The only valid solution is to set up the violin in the white with a temporary fingerboard (even if the latter has not been tuned) and wait several days until the back plate stabilizes. Then you can adjust the height of the B1+ mode frequency, and also obtain an appropriate delta. This takes a week, but you thus avoid losing a year’s work and the violin along with it, when you are so near your goal!

 

 

www.kreitpatrick.com

[Peter K-G]

Thanks!

The frequency has risen to 564 I will take the time it needs now.

The sound box, with sound post and neck is now 292 g

 

weights now are likely to be as follow:

 

Top:                    67g   (had quite oversized overhang before edgework )

Back:                  97 g

Ribs:                   58 g

Neck:                 68 g

SP:                       1 g

 

 

[Peter K-G]

(Maestronet has obviously been down for a couple of days, It happens every now and then I have noticed)

 

Dust in the workshop!

While wating for the violins frequencis to settle I did test varnishing on some samples, looking good but full off dust. Have to do something about that before I start the varnishing process.

 

I'm using Oldwood varnishing system for this one also http://www.oldwood1700.com/

Great results but time consuming (and really expensive);

 

 

Violin #4 finished grounding stage and first coat of varnish:

 

 

For my next violin I'm going to try someting else.

[Peter K-G]

After sanding down back in the middle a little bit more 0,5-1 g.the modes has now stabilized.

With temporary glued finger board and 40 g center attached chin rest:

 

B1+= 541
B1- = 439 (444 if the clamps are adjusted so that the chin rest is more to the edge)

 

I started grounding today

[Peter K-G]

I'm using System 6, from this table: http://www.oldwood1700.com/sistemas_aplicacion.aspx

 

Insulation with gelatin and first coat of golden ground A.

 

 

 

second coat of ground A and B

 

 

 

sorry about the bad picture quality, too dark in the workshop.

 

Next step is sizing with Doratura Minerale

 

 

[Peter K-G]

Mineral ground applied, now I have to wait a couple of days before starting the final varnishing:

 

 

 

[Janito]

Mineral ground applied,

The mineral rubble is rather coarse, ne c'est pas?