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Violin #5 - Strad Body modes


Peter K-G

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Here again when all is said and done with all this, when the ribs and plates are done and free. Will they move the same as the target violins plates? In my opinion the only way to even closely mimic another instruments tone is to mimic the range of motion in various modes of stress of the individual plates on a macro level.

 

edit; using very similar material

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  • 2 weeks later...

Fresh from the owen, Medium rare;

 

Top

 

Half 1.

330 g -> 305 g; M5,  574 Hz -> 578 Hz

Half 2.

405 g -> 379 g; M5,  695 Hz -> 701 Hz

 

New back plate Wood

 

Back

 

Half 1.

719 g -> 684 g; M5, 514 Hz -> 518 Hz

Half 2.

677 g -> 643 g; M5, 468 Hz -> 471 Hz

 

I am very suprised that the M5 modes did not change more !!!!

(M5 is wrong term for the mode as Don pointed out)

 

Time to glue the plate woods together

 

The climate has been very dry here so the wood haven't absorbed any more water. Five days after heat treatment (Mars 2) the readings where as follow. Readings today shows the same:

 

Top

 

Half 1.  309 g,  580 Hz

Half 2.  384 g,  704 Hz  

 

Back

 

Half 1.  688 g,  522 Hz

Half 2.  648 g,  477 Hz

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Top plate glued together, planed flat on the inside and down to 18 mm, 522 g (perfect seam, huh..)

 

Clean and loud ring tones at 555 Hz and 270 Hz

 

The wood is high performance. I also did Don's end wood knocking test, 7596 Hz on both halfs (glued together), very easy to find. With this method C would now be ~ 6250 m/s 

 

Edited 26.3:

 

Back plate glued together, planed flat on the inside and down to 17 mm, 986 g
 
405 Hz and 251 Hz
 
(End wood knocking test, 5740 Hz on both halfs C would be ~ 5100 m/s)

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6250 m/s is about as high as I have seen.  It tends to go with the higher density spruce, over .4 g/cc. 

 

The stabilized properties of your wood may not be quite that good, as it appears to be only 30 days since it was cooked.  It should have some more weight to gain before the moisture content really reaches equilibrium, and longer if the weather is very dry.  Here's a chart of moisture content vs. time from one of my bakes, so you can see that the stabilization time is more like 3 months.

post-25192-0-87491300-1364239189_thumb.jpg

 

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6250 m/s is about as high as I have seen.  It tends to go with the higher density spruce, over .4 g/cc. 

 

The stabilized properties of your wood may not be quite that good, as it appears to be only 30 days since it was cooked.  It should have some more weight to gain before the moisture content really reaches equilibrium, and longer if the weather is very dry.  Here's a chart of moisture content vs. time from one of my bakes, so you can see that the stabilization time is more like 3 months.

attachicon.gifAdsorbtion.jpg

 

Nice chart! Based on your own experiments? It concides with experience with cooking wood for my last violin (#4) it absorbed about half the weight it lost. I waited a lot longer then (2-3 months ) before I started working with it. I have to consider this when I start tuning :)

 

This cooked wood haven't changed for 25 days now, very dry winter days here.

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It is possible that your cooking didn't get down to absolute zero moisture content.  My chart is from my processing, which comes out as low as you could possibly get on moisture (a couple of days at 300F under high vacuum).

 

Regaining half of the water loss looks about right... that's what I got for the cooler (i.e. less aggressive) processing.  Stronger processes showed more permanent loss, regaining only ~30% of the lost mass.

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Nice chart! Based on your own experiments? It concides with experience with cooking wood for my last violin (#4) it absorbed about half the weight it lost. I waited a lot longer then (2-3 months ) before I started working with it. I have to consider this when I start tuning :)

 

This cooked wood haven't changed for 25 days now, very dry winter days here.

 

 

Peter, it is imperative that the moisture content in the wood be brought back up to at least 6%: otherwise, the back plate will become deformed as you sculpt the arch on the extrados. Leave the back plate in your bathroom for a while.

www.kreitpatrick.com

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That's a very distinctive top arch. Dare I say unusual?

Sloan's ex-Jackson Strad definitely has high, full arching, with plenty of flat in long arch, center.  Unusual I can't say, as I'm not an expert on all of Strad's stuff.  My main interest is to see if this arching and graduation is responsible (at least partly) for this instrument's notable acoustic performance.

 

The Habeneck has a similar side profile.

 

http://apollo.ram.ac.uk/emuweb/pages/ram/display.php?irn=329

Unfortunately, I don't see any side profile photos on the site.

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I should point out that my stabilization plot is only for spruce.  I haven't tracked maple, but would expect it to adsorb moisture more quickly, as maple has much greater crossgrain permeability. 

 

One possibility to speed things up would be to rough carve the plates, but leave plenty of material to allow for some distortion.  10mm thick wood will stabilize much faster than 20mm thick.

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Peter, it is imperative that the moisture content in the wood be brought back up to at least 6%: otherwise, the back plate will become deformed as you sculpt the arch on the extrados. Leave the back plate in your bathroom for a while.

www.kreitpatrick.com

 

I'm going to go for it anyway, can't wait to the middle of may

 

I have had this problem (tuning opportunity) before. Found som pictures of Violin #4, this is what's going to happen when arching is finished, I know how to handle it:

 

post-37356-0-45360500-1364459714_thumb.jpg

 

post-37356-0-98021000-1364459791_thumb.jpg

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Minor warping wouldn't bother me. I'd be much more concerned about the long-term integrity of a center joint which was made before the wood had attained moisture stabiliby.

 

Glad you pointid that out so others won't make this mistake, because it's exactly what would happen (has happened on 2 violins) If you glue together too dry, back plate wood with hide glue. (both cooked or uncooked wood in wintertime -20 C outside, + 23 C inside)

 

There is however a solution (Sorry about this, might ruin my reputation as a violin maker  :unsure:)

 

post-37356-0-21463900-1364468968_thumb.jpg

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Glad you pointid that out so others won't make this mistake, because it's exactly what would happen (has happened on 2 violins) If you glue together too dry, back plate wood with hide glue. (both cooked or uncooked wood in wintertime -20 C outside, + 23 C inside)

 

There is however a solution (Sorry about this, might ruin my reputation as a violin maker  :unsure:)

 

attachicon.gifCascoOutdoor.JPG

No! - This glue will creep! I know from experience with the indoor version. I will never use it again in joints subjected to stress in a fiddle. 

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Is your experience particularly with Casco? I have only used outdoor PVA glue (Kiilto B3) with no creeping problem.

Never used Cascol outdoor before. I have to admit it got me a little bit worried. I'm not going to try hide glue with dry maple again, it won't work.

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