Carving expensive bridge to make best out of cheap chinese violin Stentor Standard

[SCorrea]

Sharp tools are necessary to create solid glue joints.  The FAA's reference work for Aircraft Repair is quite specific that sand paper never be used for preparation of any glue joint.  The problem is crushed fibers which render the strength of the joint to be of a questionable nature.  I really suspect that Violins are the same.  Crushed fibers seem to be a thing that attenuates sound transmission and deadens the instrument.    For the curious, I have included AC43.13-1B for your reading pleasure.

 

1-6. PREPARATION OF WOOD SURFACES FOR BONDING. It is recommended that no more time than necessary be permitted to elapse between final surfacing and bonding. Keep prepared surfaces covered with a clean plastic sheet or other material to maintain cleanliness prior to the bonding operation. The mating surfaces should be machined smooth and true with planers, joiners, or special miter saws. Planer marks, chipped or loosened grain, and other surface irregularities are not permitted. Sandpaper must never be used to smooth softwood surfaces that are to be bonded. Sawn surfaces must approach well-planed surfaces in uniformity, smoothness, and freedom from crushed fibers. It is advisable to clean both joint surfaces with a vacuum cleaner just prior to adhesive application. Wood surfaces ready for bonding must be free from oil, wax, varnish, shellac, lacquer, enamel, dope, sealers, paint, dust, dirt, adhesive, crayon marks, and other extraneous materials.

 

Enjoy..

[Marty Kasprzyk]

5 hours ago, SCorrea said:

Sharp tools are necessary to create solid glue joints.  The FAA's reference work for Aircraft Repair is quite specific that sand paper never be used for preparation of any glue joint.  The problem is crushed fibers which render the strength of the joint to be of a questionable nature.  I really suspect that Violins are the same.  Crushed fibers seem to be a thing that attenuates sound transmission and deadens the instrument.    For the curious, I have included AC43.13-1B for your reading pleasure.

 

1-6. PREPARATION OF WOOD SURFACES FOR BONDING. It is recommended that no more time than necessary be permitted to elapse between final surfacing and bonding. Keep prepared surfaces covered with a clean plastic sheet or other material to maintain cleanliness prior to the bonding operation. The mating surfaces should be machined smooth and true with planers, joiners, or special miter saws. Planer marks, chipped or loosened grain, and other surface irregularities are not permitted. Sandpaper must never be used to smooth softwood surfaces that are to be bonded. Sawn surfaces must approach well-planed surfaces in uniformity, smoothness, and freedom from crushed fibers. It is advisable to clean both joint surfaces with a vacuum cleaner just prior to adhesive application. Wood surfaces ready for bonding must be free from oil, wax, varnish, shellac, lacquer, enamel, dope, sealers, paint, dust, dirt, adhesive, crayon marks, and other extraneous materials.

 

Enjoy..

 Does this suggest gluing the bridge onto the top plate?

[ctanzio]

Crushed fibers are only mentioned in your quotation in reference to sawn surfaces, not sanded surfaces.

The main issue with sanded surfaces is that the dust will settle into the porous structures of the wood and, depending on the wood, can compromise the mechanical bond formed between the glue and the surface. But a thorough cleaning can resolve this problem.

Planing and scraping, even with well sharpened tools, will shred and crush the walls of the top layer cells. It can be very dramatic for woods like spruce and pine. As long as the surface is cleaned to remove loose debris, one can still expect a good mechanical bond between wood and glue.

It is possible to use very fine sandpaper techniques to prepare wood surfaces to see fine, undeformed details of cell structures that match the finest microtome techniques. Such surfaces are of questionable use as a glue surface because of lack of mechanical interlock between glue and wood.

I am not questioning the validity of the FAA standard practice for prepping wood surfaces. I am saying the reason you cited for not sanding is most likely not due to "crushed" cells, but rather wood dust accumulating in the open cell structures.

[Pianootaku]

I'm thinking about another experiment, I wonder if anyone tried it and can predict the result. What if one would carve bridge in such way with proportions recommended from https://trianglestrings.com/carving-a-violin-bridge/ but left the feet vertical thickness at their original blank size. Resulting in shape like in this attached drawing. Would the bigger surface of the feet touching the violin plate increase better transmission of the vibrations and energy while keeping the benefit of reducing mass of above feet part? Or maybe the unconventional shape would make the sound too high in higher frequencies?

[David Burgess]

2 hours ago, Pianootaku said:

I'm thinking about another experiment, I wonder if anyone tried it and can predict the result. What if one would carve bridge in such way with proportions recommended from https://trianglestrings.com/carving-a-violin-bridge/ but left the feet vertical thickness at their original blank size. Resulting in shape like in this attached drawing. Would the bigger surface of the feet touching the violin plate increase better transmission of the vibrations and energy while keeping the benefit of reducing mass of above feet part? Or maybe the unconventional shape would make the sound too high in higher frequencies?

Your illustration appears to show increased horizontal width or area, rather than increased vertical thickness. Which were you asking about?
If it is increased width along the axis of the strings, I probably make that thicker than most, and haven't observed anything harmful from so doing. If is leaving the feet thicker vertically, I make mine much thicker than many bridges from famous shops of yesteryear, and haven't observed any downside to that either.

[Pianootaku]

54 minutes ago, David Burgess said:

Your illustration appears to show increased horizontal width or area, rather than increased vertical thickness. Which were you asking about?
If it is increased width along the axis of the strings, I probably make that thicker than most, and haven't observed anything harmful from so doing. If is leaving the feet thicker vertically, I make mine much thicker than many bridges from famous shops of yesteryear, and haven't observed any downside to that either.

I meant leaving the lower part of the feet as it was originally in blank size 5.75mm like on the left picture. The piece of uncarved part would point towards the fingerboard. Instead of doing it traditionally like on the right picture with recommended on trianglestrings thickness 4.2 mm and without boot like shape. Note that everything on the left is carved with the same thickness above the feet, I think it would require additional tool than plane to do this. I have never seen anyone carving bridge this way and was curious if bigger surface touching the surface would improve transmittion of vibrations.

 

[FiddleDoug]

4 hours ago, Pianootaku said:

I'm thinking about another experiment, I wonder if anyone tried it and can predict the result. What if one would carve bridge in such way with proportions recommended from https://trianglestrings.com/carving-a-violin-bridge/ but left the feet vertical thickness at their original blank size. Resulting in shape like in this attached drawing. Would the bigger surface of the feet touching the violin plate increase better transmission of the vibrations and energy while keeping the benefit of reducing mass of above feet part? Or maybe the unconventional shape would make the sound too high in higher frequencies?

I would think that trying to carve that complex shape, and still having it fit perfectly to the belly would be very difficult if not impossible. A waste of effort in my opinion.

[Brad Dorsey]

1 hour ago, Pianootaku said:

I meant leaving the lower part of the feet as it was originally in blank size 5.75mm like on the left picture. The piece of uncarved part would point towards the fingerboard…

If they are as thin as they are shown in your left picture, I think the bits pointing toward the fingerboard would easily break off if the bridge leaned slightly in that direction.  And it is very common for bridges to be pulled towards fingerboards when the strings are tightened.

[Marty Kasprzyk]

53 minutes ago, Brad Dorsey said:

If they are as thin as they are shown in your left picture, I think the bits pointing toward the fingerboard would easily break off if the bridge leaned slightly in that direction.  And it is very common for bridges to be pulled towards fingerboards when the strings are tightened.

The bits pointing forward can be made with separate pieces of wood glued onto the bottom of the bridge feet with their longitudinal grain direction going parallel to the top plate which would be much stronger and less likely to break.

"Its difficult to make predictions--especially about the future."  But if you try it I predict the violin's sound will either get better, stay the same, or get worse.

 

[Don Noon]

4 minutes ago, Marty Kasprzyk said:

The bits pointing forward can be made with separate pieces of wood glued onto the bottom of the bridge feet...

Acoustically, I don't think it would work any different than footpads glued to the top plate, which I have done for extremely low-density top plates.  I believe Joseph Curtin has done that too.  And as far as I can tell, acoustically it doesn't work any different than without the footpads.

[Marty Kasprzyk]

46 minutes ago, Don Noon said:

Acoustically, I don't think it would work any different than footpads glued to the top plate, which I have done for extremely low-density top plates.  I believe Joseph Curtin has done that too.  And as far as I can tell, acoustically it doesn't work any different than without the footpads.

I agree.  Your and Curtin's foot pads and the suggested forward pointing bits are way too narrow to have much of an acoustic effect--but great for durability improvements.

So for having an impact on the sound I suggest that the forward bridge foot extensions be much larger--about ten times larger than the 1.55mm increase that Pianootaku has just suggested: around a 20mm wide bridge foot.

The reason for this is that it might increase the violin's high frequency output.  When a string is bowed the string sticks to the bow hair (that's why we use sticky rosin) as it is pulled transversely away from its static position.  Eventually the string is stretched enough that it breaks away and flies backward.  The string flies past its neutral static position and is eventually comes to a stop where it is stretched again gets stuck to the bow hair.  This one trip string  motion cycle produces one bridge foot motion cycle--hence one cycle of the sound being produced.

But as the string is first pulled sideways by the bow it stretches the string a little which produces a longitudinal tension increase in the string.  When the bow hair looses its grip and the string flies by its neutral position the tension goes to zero.  As the the string continues moving it eventually comes to a far away stop in which the string  is again a stretched a little.

Thus the string produces two longitudinal tension pulses to the bridge for every transversal cycle to the bridge--twice the sound frequency.

This effect is well known in guitar acoustics (1) but it is insignificant in violin acoustics because the very narrow violin bridge doesn't transfer the bridge's out of plane vibrations (tipping back and forth and bending from the 2x longitudinal string vibrations) very well to the top plate.

Therefore by making the bridge foot much much thicker I would expect better longitudinal string vibration coupling to the violin body--The violin might sound a little brighter with a little more high frequency sound output.

Of course if the violin is already too bright or harsh sounding this is in the wrong direction to go.  On the other hand if it is too dark or hollow sounding  this might help.  So you really can't predict if Pianootaku's  idea is helpful or not.

Nevertheless I predict that even though it might sometimes be helpful it will be not adopted because it doesn't look traditional.

 

  1.  "The Physics of Musical Instruments, 2nd edition", Fletcher & Rossing,Springer, 1998,  Chapter 9.3 'Force  Exerted by String'

 

[Pianootaku]

Thank you all for all suggestions when I'll carve the Milo Stamm bridge I'll give feedback on how it went, and ask for more quidance if there will be some need for small adjustments. So far I did experiment and completely cut arms of the spare Teller bridge to see what will happen and the frequency of all strings went too high making it sound very unpleasent. I'll remember to not do that again, lol.

[Pianootaku]

2 hours ago, Pianootaku said:

 So far I did experiment and completely cut arms of the spare Teller bridge to see what will happen and the frequency of all strings went too high making it sound very unpleasent. I'll remember to not do that again, lol.

I brought all the low frequency back by carving an arch in the crotch. Intrestingly Ive heard opinion of luthier that if you make crotch higher it will make the sound empty and weak but here it made low and middle frequencies higher giving it more power. So far carving out more of mass improved the response even more. It made even the A and E strings sound more thick with more power. Im surprised that even though Ive carved so cheap $3 bridge so thin for the sake of experiment, its still enduring the strings tension but maybe it ll break with time.Its gonna go to waste bin anyway. Heres photo, the cuts are not smooth and look terrible because I was carving it with strings on. Im looking forward to carving Milo Stamm soon and see what will be the effects.

[mezzopiano]

Not too dissimilar from this one:

[bridge of a Joseph Curtin Ultralight, one of my favourite modern violin designs, btw]

[palousian]

3 hours ago, Pianootaku said:

Heres photo, the cuts are not smooth and look terrible because I was carving it with strings on. Im looking forward to carving Milo Stamm soon and see what will be the effects.

It looks to me like the bass side foot of your bridge is not well-fitted to the violin top.

[Pianootaku]

I finally carved Milo Stamm Royal but Im very dissapointed, the sound is very harsh probably because of density of the wood projecting too much of the higher frequencies, even though the tone and response is noticably better. Probably it sounds good only with higher density plates. What a waste of money. At least i learned something about bridges.

I bought another bridge Milo Stamm standard for 10 dollars to carve.If i knew earlier that these can be carved as thin as the denser ones i wouldnt buy the royal version. Hopefully this one softer wood will be perfect for my Stentor standard violin.

Ive noticed that both milo stamm royal and standard have different shapes of the grain on front and on back. On front the grain is more like lines and on back is more like dots. Im curious if it matters for the sound if I will reverse back with the front so i can keep the front marking sign 'milo stamm' without carving it out as long as I will carve the bridge 90 degree. I did that for Milo stamm royal, maybe thats why the sound is harsh?

My question is: Do these shapes of the grain affect the sound in any way or it doesnt matter which side i will use for the front?

First photo Milo Stamm Royal carved and standing on ciolin.Second and third photo show uncarved Milo Stamm Standard with different shape of grain on each side.

 

Edited April 18 by Pianootaku

[FiddleDoug]

The grain is different on the two sides because the "grain" that you're talking about are medullary rays. These are VERY specifically aligned with the true quarter sawn alignment. These long rays, and the bridge brand, are typically on the side towards the tailpiece as this side is kept flatter and is the strongest. The side with the "dots" goes towards the fingerboard, and gets rounded some when fitting and trimming.

[Pianootaku]

4 hours ago, FiddleDoug said:

The grain is different on the two sides because the "grain" that you're talking about are medullary rays. These are VERY specifically aligned with the true quarter sawn alignment. These long rays, and the bridge brand, are typically on the side towards the tailpiece as this side is kept flatter and is the strongest. The side with the "dots" goes towards the fingerboard, and gets rounded some when fitting and trimming.

This Milo Stamm Royal when it was blank it had long rays and brand signature on front side (towards the fingerboard), I could clealy see that this side did not have 90 degree angle in relation to feet, and it had dots on the backside towards tailpiece where it was 90 degree with feet. So it seems it was recommended this way by Milo Stamm company. But I reversed because I wanted to keep the pretty brand signature.

I can also see Milo Stamm Royal bridge in this video having lines on the front side and dots on the back side.

But if you say it should be the other way around, then with relief I can say I carved it correctly and I shouldnt be worried that I messed up the sound. Now I found In this old post from 2009 where conlusion is made that it really doesn't matter and there is no tangible evidence for the sound being any different which side one will use for back. When I look at uncarved Milo Stamm Standard I can't say which is 'back' side just by looking how the lines align into 90 degree. It's been carved a little bit imprecise by Milo Stamm in comparison with the Royal version. I guess I will keep the longer rays as back again as I want to keep the brand signature again.

 

[Davide Sora]

1 hour ago, Pianootaku said:

This Milo Stamm Royal when it was blank it had long rays and brand signature on front side (towards the fingerboard), I could clealy see that this side did not have 90 degree angle in relation to feet, and it had dots on the backside towards tailpiece where it was 90 degree with feet. So it seems it was recommended this way by Milo Stamm company. But I reversed because I wanted to keep the pretty brand signature.

I can also see Milo Stamm Royal bridge in this video having lines on the front side and dots on the back side.

But if you say it should be the other way around, then with relief I can say I carved it correctly and I shouldnt be worried that I messed up the sound. Now I found In this old post from 2009 where conlusion is made that it really doesn't matter and there is no tangible evidence for the sound being any different which side one will use for back. When I look at uncarved Milo Stamm Standard I can't say which is 'back' side just by looking how the lines align into 90 degree. It's been carved a little bit imprecise by Milo Stamm in comparison with the Royal version. I guess I will keep the longer rays as back again as I want to keep the brand signature again.

 

I agree that it really doesn't matter, as long as the medullary rays are as continuous as possible looking at the bridge from the sides (section). In my video you see the long medullary rays towards the fingerboard, which is the most traditional way used, but there are opposing opinions and those, like me, who say it makes no difference.

The choice is yours.