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Lightening a Violin Bass Bar
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Irv
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March 6, 2020 - 3:09 pm
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Well, I finally got around to removing the top plate on a beater violin to repair cracks (I would not want to attempt this on something nice or something not owned by me).  The bass bar is substantially more bulky than the one pictured below.  I can chisel down the material to remove weight.  That is easy.  I will also make sure that the width is not over 6 mm.

I think that it would be possible to introduce a hole through the highest portion of the bass bar (the portion under the bridge) to further reduce mass.  I do not think it would significantly reduce strength.  But I have not heard of anyone doing this.  Any thoughts?868E58C4-7729-4222-A3B2-954A23725608.jpegImage Enlarger

Without deviation from the norm, progress is not possible.         —Frank Zappa

The future is already here—it’s just not very evenly distributed. —William Gibson

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Peter
West Sussex, England UK
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March 6, 2020 - 3:29 pm
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Have you made any acoustic measurements before dismantling, or will you just rely on your memory of the sound?

This thread will be of great technical interest but I will generally sit it out.

Peter

"It is vain to do with more that which can be done with less"  - William of Ockham

"A crown is merely a hat that lets the rain in" - Frederick the Great

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Irv
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March 6, 2020 - 3:48 pm
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@Peter and others.  I purchased it with three major cracks that were “repaired” with hot glue (which is a good thing because other types of glue would have been beyond my ability to remove).  A little saturation with alcohol made the hot glue pliable and easy to remove.

A useful repair is definitely going to require the use of spruce cleats.  So the top had to come off.  Once the top was off, I noticed the size of the “timber” used to construct the bass bar.  Hence my question.  

No idea how it originally sounded.  It, other than the bass bar, appears to have been nicely constructed and has reinforcement blocks in all corners.  

I intend to integrate a piece of newsprint around the interior perimeter of the top plate when I finally glue it up.  Tertis did this when he set about the development of his viola design to ease plate removal.  This makes a lot of sense to me.  I would rather have stress released at that glue joint than crack the plates of the corpus.

Without deviation from the norm, progress is not possible.         —Frank Zappa

The future is already here—it’s just not very evenly distributed. —William Gibson

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Peter
West Sussex, England UK
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March 6, 2020 - 4:32 pm
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You have a very sound plan there @Irv.

The reason for my interest is the very skimpy nature of the bass bar in my own violin. When I took the table off to repair the cracks, I noted that I have a thin, shallow carved-in bass bar which had cracks of its own. I treated the bar to a thin dressing of hide glue to consolidate it, and had to splint the top end for around 2-1/2" of its length. The result is great to my ears, and raised approval from my teacher.

I would like to know how a violin's sound changes when the bass bar is changed in profile; an option for me is to remove the compromised bar and replace it with a glued-in one. I guess I should get a fixer-upper from eBay and experiment.

(So much for watching the traffic...)

Peter

"It is vain to do with more that which can be done with less"  - William of Ockham

"A crown is merely a hat that lets the rain in" - Frederick the Great

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Irv
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March 6, 2020 - 5:41 pm
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@Peter and others.  The only luthiers who make use of that wasteful practice in current times are those that make fakes!  It takes a lot thicker piece of spruce with an integrated bass bar.  

A special treat for you.  Go to YouTube and look up “putting a kettlebell on a Violin.”  27 kg is the amount of pressure an average set of strings puts on a violin.  

It might be entertaining to express some loose tea on the back of the top plate and see what patterns I can create when I shoot it with various frequencies.  But since the end goal is to make it into a “hole in the heart” viola, it would only benefit academic interest.

Without deviation from the norm, progress is not possible.         —Frank Zappa

The future is already here—it’s just not very evenly distributed. —William Gibson

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Irv
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March 6, 2020 - 10:16 pm
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I found a “before” picture. 8B38EBEC-3218-488B-884F-24CF52906882.jpegImage Enlarger

Without deviation from the norm, progress is not possible.         —Frank Zappa

The future is already here—it’s just not very evenly distributed. —William Gibson

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Mark
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March 7, 2020 - 12:50 am
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That's some cracks it has

Master the Frog and you have mastered the bow.

Albert Sammons

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