Bass bar thickness - not height!


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I receive so much wonderful support through my SCAVM membership that I feel adulterous coming here for help! :) But I don't want to wait for the next meeting, so I respectfully ask this forum's advice...

This is really a two-part question:

1) Having fitted, glued, and shaped the bass bar to my violin top I only now remember that I forgot to thickness it to 5.5mm. Any thoughts on how to thin it from 6.3mm to 5.5mm without removing it? Using a knife to carefully pare it to the proper thickness might be best, but there is danger cutting into the top.

2) What if I left it at 6.3mm - what effect might a wide bar have? There would be no risk of plate damage if I leave it as is...as long as there is minimal or no negative effect.

I have seen many discussions about the height of the bar but nothing on the thickness. Perhaps one consideration is the ratio of a bar's height to its width, which also relates to its total mass.

Thanks in advance,

--Bruce

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Bruce,

I did the same thing on my first cello bass bar. I didnt worry too much about the final thickness but how well the tap tone sounded. Fortunately you remembered before putting the top back on unlike me. I used a 10mm flat finger plane to reshape the barr but considering the size difference you may want a smaller one. Also reduces the chance for damaging the top.

Jesse

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A few things.

Is every other aspect of the violin just as you would like it?

The arching? The graduations? If you left it, would it bug you?

If so, then take it out and do it again. You can NEVER fit to many bass bars.

However, I don't think 6.3 is all that thick.

Thicker then the norm, and mine, but not too terrible.

That being said, I would still take it out.

Or not. :)

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I'd leave it. The weight difference is less than 1 gram. Reduce the height slightly to get the same strength.

If you want to go after that 1 gram, you could plane a small scallop in both sides using a finger plane, where height will allow. Same principal as an I-beam. :)

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I don't think you have any choice, you have to fix it. Not that what you have is terribly wrong, but it will bug you. Even if the fiddle turns out to sound as you want it you will still think, if only I'd have fixed the bass bar. The only question is how to fix it. Try to thin it first, you can always cut it out if thinning doesn't work. Try making a small sanding block and glue some 180 grit to it and sand it a bit. The paper doesn't have to go the the bottom of the block leave a tinny area not covered with paper so you won't cut into the top. Clean that area up with a knife or scraper. I'm sure there are many other ways to fix this, this is just a thought. In the end do what ever you think will work for you.

Berl

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OK Bruce, you're in BIG trouble now. The SCAVM gestapo has been monitoring your activity, and we don't like it... going behind our back to get illicit information from the likes of David Burgess when you could get all the misinformation you want from the proper channels! :):):)

That being said, the choice is up to you on the bass bar. You can look at it as the opportunity to do another bassbar fitting, which is always good practice. Or it might just be too depressing to undo a few hours of work. If it was me, I'd take it out and replace it, because fitting a new bass bar doesn't seem like too much trauma (having regraduated and re-bassbarred enough old junkers to get the hang of it). I also agree with David that the extra weight of the existing bar won't make that much difference.

So, pick your poison. You're going to be just as dead either way. B)

D. Noon

SCAVM Librarian

and internet enforcer

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In school (Salt Lake City) two bass bar configurations were discussed, either the usual 5.5 mm thick bar or a sort of pre-tapered bar, 6.0 at the bottom and 5.0 at the top. If you shape your 6.3 mm bar with a little more taper than usual you wouldn't be far off the latter method. Height has much more to do with the final stiffness and you may find that you don't need to reduce the height much below nominal to get the right amount of flexibility.

Doug

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Unbelievable...7 replies, 7 answers - just what I expected! :)

In another sense though, they are all the same: consider the overall structure of the BB, and do what I think is best for this violin.

This was really useful from all of you because rather than just dictating the "right" answer, you've asked me to make my own judgment after giving me the key points to consider.

So I've decided: I will leave it alone. A few of you mentioned the overall mass and since my plate is about 3 or 4 grams lighter than my target this adds some back - albeit at the expense of a little more longitudinal stiffness.

I have a second rib garland finished and top plate rough-arched already, so I'll get more bass bar fitting practice soon enough!

Don - I'm shaking in my boots :)

Thank you all so much! I hope to be able to contribute some day.

--Bruce

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Please tell me how you balance or tune your bassbar.

Mike

Hi Mike,

I wish I could say I used some well-established (if there is one) method, but I didn't. Reading and talking with others it seems there are three camps:

1) sophisticated electronic means (requires sophisticated electronics - or a day in Don Noon's garage)

2) manually tapping/flexing (requires experience :) )

3) formulaic (40mm from each end: 13mm at peak; peak placed in middle (or somewhat lower). Requires a ruler (and remembering to properly thickness the bar before gluing)

I chose #3. For this one.

--Bruce

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Bruce,

If you want to tune mode 5 to anything in particular, that's more like a few minutes, not a day. Mode 2 is more of a "that's what it is" measurement rather than something to tune, unless you want to regraduate the plate.

I'm semi-available all the time, if you want to stop over. Let me know. I'll get the cyanide tea ready.

-dn

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Bruce,

I'm semi-available all the time, if you want to stop over. Let me know. I'll get the cyanide tea ready.

-dn

Don - I just might take you up on that! My employer is forcing us to take 5 days vacation this quarter (it helps their bottom line by reducing the vacation backlog) so I'll coordinate with you offline on a good day for you.

--Bruce

------------------

"Do not fret; it leads only to evil." :)

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