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Kallie

Fingerboard wedge instead of correcting neck angle

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Brad, I think accepting that there is "some" forward force on a bridge (given that the front angle is flatter) is not the same as claiming that it is the cause of a bridge bending. To repeat: I see bridges bent in both directions even with identical setup parameters. It is the direction of tuning (with pegs, or with fine-tuners) which determines this.

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Peter, those figures are fudged. Just two of the flaws: adding the thickness of the tailgut to your calculations, and including the bridge "wedge". Your illustration in fact shows a back angle of 76.6º. If the total string angle is 158º, that would make the front angle 81.4º. I'm not familiar with the branch of trigonometry which allows one to DIVIDE a triangle by making a portion of one leg disappear. That sounds like alchemy to me.

 

They are not fudged, instead I'm trying to illustrate an example that shows how close to equal calculated angles you can come.

=> It seems that it's not possible to have perfectly equal angles!

 

I'm in favour of balance between the angles, but not fixed with it, as I sayd in earlier post. I just focus visually on the neck angle, together with the measures and make the sadle to fit with that.

 

- http://www.maestronet.com/forum/index.php?/topic/328814-fingerboard-wedge-instead-of-correcting-neck-angle/page-2#entry592307

- post #24 - "As the tail piece angle is more "fixed" it's easier to just look at the neck angle."

 

Playability and sound is the most important for me.

 

The angles are sensitive to millimiters, as the calculations shows:

sin-1(325/330) = 80º

sin-1(326/330) = 81º

 

I think that 76º after the bridge is pretty much average on violins with proper setup

 

The Lady Blunt Stradivari had the most visually "correct" angles that I found. Measuring by drawing lines, the angles are about

81/76, that means 157º over the bridge edge.

 

And I'm not a mathematician either. It took me an hour to figure out the trigonometry formulas by googling :huh:

 

Simply put;

You are right! - If you focus on the 158º angle over the bridge you will most likely end up with 79º/76º, with 3º deducted for the bridge wedge (82+76=158).

 

Thanks for the mind crunching

 

Peter

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David,  I don't follow you.  I thought I had this all figured out.  Can you explain how my conclusion is flawed?  Faulty logic?  Flawed premises?

 

I'll try, and hope that it doesn't end up being an undecipherable jumbel of words. :o

 

If the string doesn’t move in the bridge groove in our thought model, think of the section of string at the front of the bridge, and the section of string at the back of the bridge as two separate cables, each attached to the bridge with a screw. Let’s call the string at the back of the bridge a “backstay”.  The cable on the front is pulling forward. The cable on the back is pulling backward. Of course, it’s angle isn’t very efficient for a backstay, so it will be pulling down on the bridge much harder than it will pulling back, but it will still have a component of the total force (a vector) pulling straight back with a force equal to that of the cable pulling the bridge from the front.

 

The zero angle of the backstay in your example threw me a curve, and had me rethinking a few times. How can a backstay do anything if it’s parallel with the back surface of the bridge, and there is no space between the anchor point and the back of the bridge? I realized how it could do that when I considered that he bridge isn’t two dimensional. It has thickness. If the bridge is 4mm thick at the base, the backstay is anchored 2mm back from the center of the bridge, and 4mm from the front of the bridge. Again, that’s not  a very efficient angle for a backstay, but it’s enough of an angle to work. For the bridge to lean forward, the backstay would need to increase in length. We’ll assume it can’t, but if it did stretch a little bit and the bridge leaned forward, you tighten the backstay a bit to return it to it’s original length, and the bridge comes back to it’s original position.

 

Yes, the backstay is under a lot more tension than the cable in the front, but because of the difference in string angles on the two sides of the bridge on a normal violin, the afterlength is under a little more tension than the "playing" side of the string as well. If that's hard to understand, I suppose one could think of it this way: Because of the difference in string angles, the bridge "wants" to pull forward, and that places an extra tension load on the afterlength to keep it from happening.

 

Whew. :lol:

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Peter,

 

The Pegbox is like a big slow merry-go-round (despite a shortage of merriness at times). It goes round, and it comes round. The same questions and theories come up periodically, and get resolved the same way. At least now you have caught up with where I was about eight years ago on this one ^_^

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I'll try, and hope that it doesn't just get totally confusing. :o

 

If the string doesn’t move in the bridge groove in our thought model, think of the section of string at the front of the bridge, and the section of string at the back of the bridge as two separate cables, each attached to the bridge with a screw. Let’s call the string at the back of the bridge a “backstay”.  The cable on the front is pulling forward. The cable on the back is pulling backward. Of course, it’s angle isn’t very efficient for a backstay, so it will be pulling down on the bridge much harder than it will pulling back, but it will still have a component of the total force (a vector) pulling straight back with a force equal to that of the cable pulling the bridge from the front.

 

The zero angle of the backstay in your example threw me a curve, and had me rethinking a few times. How can a backstay do anything if it’s parallel with the back surface of the bridge, and there is no space between the anchor point and the back of the bridge? I realized how it could do that when I considered that he bridge isn’t two dimensional. It has thickness. If the bridge is 4mm thick at the base, the backstay is anchored 2mm back from the center of the bridge, and 4mm from the front of the bridge. Again, that’s not  a very efficient angle for a backstay, but it’s enough of an angle to work. For the bridge to lean forward, the backstay would need to increase in length. We’ll assume it can’t, but if it did stretch a little bit and the bridge leaned forward, you tighten the backstay a bit to return it to it’s original length, and the bridge comes back to it’s original position.

 

Yes, the backstay is under a lot more tension than the cable in the front, but because of the difference in string angles on the two sides of the bridge on a normal violin, the afterlength is under a little more tension than the "playing" side of the string as well. If that's hard to understand, I suppose one could think of it this way: Because of the difference in string angles, the bridge "wants" to pull forward, and that places an extra tension load on the afterlength to keep it from happening.

 

Whew. :lol:

 

 

 

 

Why keep something simple when it can be made really complicated ?

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Peter,

 

The Pegbox is like a big slow merry-go-round (despite a shortage of merriness at times). It goes round, and it comes round. The same questions and theories come up periodically, and get resolved the same way. At least now you have caught up with where I was about eight years ago on this one ^_^

 

 

Yes!

 

MN is a great place to exchange experience and learn, for both newbies like me and experienced luthiers like you and David.

 

Reading Davids last post, I think he is about to discover why there is truth in my post #21:

http://www.maestronet.com/forum/index.php?/topic/328814-fingerboard-wedge-instead-of-correcting-neck-angle/page-2#entry592307

 

- I should start doing some work instead of posting here, but it's summer and I'm too lacy for that  :)

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...If the string doesn’t move in the bridge groove in our thought model, think of the section of string at the front of the bridge, and the section of string at the back of the bridge as two separate cables, each attached to the bridge with a screw...

 

David,

 

Continuing to look at this as a thought experiment, I think you have committed the logical error of begging the question.  You are trying to prove that unequal angles do not move the bridge to one side.  But by attaching the strings to the top of the bridge with screws, you have made it impossible for the bridge to move.

 

But I'm not sure.  I might have to investigate this further with some real-life (as opposed to thought) experiments.

 

Edit:  You have assumed as true the fact that you are trying to prove.  What you said would make sense to me if the strings were screwed to the bridge, but they aren't.

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Why keep something simple when it can be made really complicated ?

 

LOL, a set of formulas would probably make it a lot simpler for a few. But I find that it doesn't communicate effectively to most people. Makes 'em go all glassy-eyed.

 

It would be great if someone would provide a simpler text version.

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David,

 

Continuing to look at this as a thought experiment, I think you have committed the logical error of begging the question.  You are trying to prove that unequal angles do not move the bridge to one side.  But by attaching the strings to the top of the bridge with screws, you have made it impossible for the bridge to move.

 

Sort of, but not really. Attaching the strings with a screw is analogous to what happens on a real, typcial violin, if someone isn't diliberately trying to move the bridge. I employed the screws in an attempt to make that clearer, because there seems to be some confusion about that (for Peter too).

 

The bridge can still move on it's own, but it happens primarily for the reason Jacob and I described earlier. The slack in a string is typically taken up at the pegbox end, and the entire string is displaced in the direction of the pegbox, taking the the top of the bridge with it. Even if the bridge is tilted back far enough to bisect the string angle, this will still happen.

The bridge doesn't move because the angles are different, unless you lube up those grooves with something exceptionally slippery. :)

Or unless the violin has an uncommon and radical lean in the bridge. In either of those cases, it tends to move very quickly in a rather dramatic way. :lol:

 

I realize that's oversimplified a bit, but I was trying to avoid making it even more complicated.

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The bridge doesn't move because the angles are different, unless you lube up those grooves with something exceptionally slippery. :)

 

 

I hesitate to enter this discussion among 800 pound gorillas, but isn't the application of graphite to the bridge grooves intended to prevent bridge deflection and equalize tension by minimizing string/bridge friction?  It looks to me as if, the slipperier the better at the bridge string contact.  If the string is free to slip laterally, the vertical tension resultant should be the only force on the bridge,at the top, it seems to me.  If the bridge is properly carved, there should also be a nearly microscopic force triangle at the groove itself, helping to keep the string tension resultant normal to the bridge.feet.

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I hesitate to enter this discussion among 800 pound gorillas, but isn't the application of graphite to the bridge grooves intended to prevent bridge deflection and equalize tension by minimizing string/bridge friction?

It can certainly help, during the usual musician string change scenario, in which one string is changed at a time.

Lets say the musician starts replacement of the string set by removing the D string. Graphite is used on the upper nut and the bridge grooves. The new string is installed, and wound up to pitch. Since the most recently lubricated D string groove is the most slippery, the string can slide over the groove as the slack is taken up by the peg, with the other strings tending to hold the bridge in place.

 

I mostly think of the graphite in the bridge grooves though as a way to reduce wear, to reduce the chances of windings separating at the bridge when bringing a string up to pitch (especially if you remove and reinstall the same string repeatedly), and to make it easier to reposition the bridge when it has been pulled forward by the strings. A combination of a tight groove, rosin on the strings, and no lubrication can make that nearly impossible to do.

 

Graphite (graphite and the clay binder, actually, if we're talking about pencil lead) is a pretty good compromise. One can get into serious trouble by using a lubricant which is too slippery. Ask me how I know. :lol:

 

It's also readily available.

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Sort of, but not really. Attaching the strings with a screw is analogous to what happens on a real, typcial violin, if someone isn't diliberately trying to move the bridge. I employed the screws in an attempt to make that clearer, because there seems to be some confusion about that (for Peter too).

 

The bridge can still move on it's own, but it happens primarily for the reason Jacob and I described earlier. The slack in a string is typically taken up at the pegbox end, and the entire string is displaced in the direction of the pegbox, taking the the top of the bridge with it. Even if the bridge is tilted back far enough to bisect the string angle, this will still happen.

The bridge doesn't move because the angles are different, unless you lube up those grooves with something exceptionally slippery. :)

Or unless the violin has an uncommon and radical lean in the bridge. In either of those cases, it tends to move very quickly in a rather dramatic way. :lol:

 

I realize that's oversimplified a bit, but I was trying to avoid making it even more complicated.

 

No David, I'm with you on that the strings are kind of attached to the bridge top. That's why the bridge will bend. The feets are also fixed and they have a surface they stand on. Think of what happens if the neck is so that the string angle is perpendicular to the bridge (and the tailpiece stays the same)

 

Another surprise at first hand is, if the neck is set that way, the strings will feel more tense, because the violin body stops acting like a spring.

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Is this any good? (very exaggerated)

 

post-37356-0-17341800-1375284144_thumb.jpg

 

post-37356-0-73234500-1375284166_thumb.jpg

 

 

The other interesting thing is how the violin body behaves, when you play the violin. That's more difficult to explain. Pushing the strings on a small angled neck does kind of squeeze the violin more lenghtwise instead of pushing down the top and thereby the back. (bad phrased explanation I know)

 

 

 

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Interesting thread.

 

I have a couple of questions. While I completely understand the math I am confused how the base of the triangle is resting. If we rest it as per Peter's drawing I believe this would give us false angles. Shouldn't the base rest on top of the saddle and the nut not extend through the tail piece ? I took a look at a number of my violins they all come in @ 155 degrees string angle. When I tried to bisect the angle with the bridge the bridge would have to lean dangerously towards the tail piece. Plus if one were to do that then the feet of the bridge would need to be cut to accomodate that angle wouldn't they ?

 

The bridge being a wedge or triangle means that one would need to take measurements through the bisected bridge as a proper bisection requires a

single line.

 

Thoughts ?

 

r.

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I'm not sure if what follows is on topic or not but might be of some interest to some folk. 

On my most recent visit to the current Stradivari exhibition at The Ashmolean in Oxford, UK, I happened to notice that the neck overstand on several of the very well preserved and relatively un molested but never the less modernized at some point violins was about 2-3 mm lower than what is now considered 'standard' set up. This is quite visible in the catalog also and not altogether uncommon.

Melvin you're right on the spot. On both the Lady Blunt and the Messiah the neck was blocked up at the heel (increased overstand and lengthened neck) by Vuillaume. At the time the French method for setup included a low overstand at the end of the neck, a position for the upper nut below the line of the ribs and a fairly low saddle.

 

Melvin, could you take a quick look in your catalogues (Stradivari Exhibition and Ashmolean Collection) and post the vibrating string lengths of these two instruments? Thanks and sorry for the bother.

 

Bruce

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Interesting thread.

 

I have a couple of questions. While I completely understand the math I am confused how the base of the triangle is resting. If we rest it as per Peter's drawing I believe this would give us false angles. Shouldn't the base rest on top of the saddle and the nut not extend through the tail piece ? I took a look at a number of my violins they all come in @ 155 degrees string angle. When I tried to bisect the angle with the bridge the bridge would have to lean dangerously towards the tail piece. Plus if one were to do that then the feet of the bridge would need to be cut to accomodate that angle wouldn't they ?

 

The bridge being a wedge or triangle means that one would need to take measurements through the bisected bridge as a proper bisection requires a

single line.

 

Thoughts ?

 

r.

 

Thanks for this post Rick. It basically outlines what I was talking about when I told Peter his numbers were "fudged", but I'm running out of gas with this topic.

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Hi Kalie, if you had phoned me i would have told you that shims can be placed on violins with a thin neck, but I should have used ebony and it would not have been noticed. Yes I did revarnish the violin and as you know I do a very good job, so the Violin did not go down in value.I was an apprentice for three years before going on my own so I think I know a little about being a luthier.

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Hi Kalie, if you had phoned me i would have told you that shims can be placed on violins with a thin neck, but I should have used ebony and it would not have been noticed. Yes I did revarnish the violin and as you know I do a very good job, so the Violin did not go down in value.I was an apprentice for three years before going on my own so I think I know a little about being a luthier.

 

Hi, I hope Im correct here in assuming who you are. If yes, please let me clarify that I did not at all refer to any violin that you repaired. The violin I was referring to was a German violin that I saw and considered buying on eBay. (I'm talking under correction here, but I believe the person selling it mentioned being an amateur repairman from the US.)

About the re varnishing, I recently saw the violin again that you repaired last year, and as you mentioned above, you did do an excellent job at that. I had the chance to admire that again when adjusting the violin.

Please take this explanation into account, and know that I did in no way refer to any of your repair work. If I wanted to find out about that, I would always have contacted you first. :)

P.S. I tried contacting you through a personal message just now, but you need 10 posts to use that.

Kallie    

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Newby here.  Lurking for several years.  I have the same questions as the OP and this discussion went off on a tangent sort of.

1.  Is there any more recent opinion or experience regarding the effect on the sound of using a shim rather than doing a neck reset.

2.  Did I read correctly that the neck wedge is reversible?  I hope.

I ask because luthiers are rare here.  One of unknown ability and experience (my stupidity for using) just did the wedge when I  thought I was paying for a reset.  He offered a longer neck included in the price, but after what I have learned recently, I'm glad he didn't try to replace it.  Now the thick neck is feeling awkward and giving me problems.   At first I was sure that must be my imagination.

The sound is not as good as before, nasal, my second biggest concern.

 I asked several times if he had run into anything unexpected or if there were any problems.  Could not get an answer.  I don't know if it had a through neck.  If there was a problem, we should have discussed it, my ignorance and inexperience notwithstanding.  Yes, it was an old trade instrument, which was  pointed out at least every other sentence, but it was very sweet sounding.  Strings were too far off the fingerboard, but I managed to learn on it.  Different bridge but height of the new one is the same as the old one.  (I measured.)  Different sound post.  Longer tail piece and the ratio of before and after string length is not, as I read on these forums, that which it should be.  I bought a shorter tail piece as an experiment (he tossed the old one, and the almost new gut core strings) and am trying to decided if I should try to install or hire someone different.  Will eventually put same brand of strings back on, but they cost a lot.  Not going back to same place.  

There were other problems as well, but I guess you can't devalue an instrument with little value to begin with.  Unfortunately I didn't know that was going to be the standard for the work being done.  At least I got it back.  I was becoming concerned about that.

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11 hours ago, Olo said:

Newby here.  Lurking for several years.  I have the same questions as the OP and this discussion went off on a tangent sort of.

1.  Is there any more recent opinion or experience regarding the effect on the sound of using a shim rather than doing a neck reset.

2.  Did I read correctly that the neck wedge is reversible?  I hope.

The change in sound you mentioned could be related to any of the things you mentioned. In my opinion, it would most likely be related to the soundpost, or the bridge. As you mentioned, both of these were replaced. The soundpost might be incorrectly placed or fitted, and the bridge might be too thick and the kidneys (the 2 holes on the bridge) too small. That usually causes a nasal sound. 

 

A better option than a shim, would've been to do a neck pullback. I think it was also discussed in this topic long ago, and it is almost standard for every trade instrument I encounter with neck angles which is too low. Unless the neck angle was too low to begin with, where a neck pullback would not work. 

 

A shim should be reversible, granted that he didn't shave the neck down to allow for a thinner neck. From what I gather, he didnt as you said the neck is very thick now. 

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