Choosing a bridge blank for a Guarneri, and fitting it

[LongNeck]

I've made a half-dozen bridges for Strads, but now I'm making a bridge for my first Guarneri, and I'm wondering whether I should do anything different for the Guarneri.

Do people usually use the same blanks for both?

Should I change any of the specs for say string height, foot thickness, bridge thickness, angle with the belly, etc.?

I'm not looking for perfection or extreme optimization---just ordinary, accepted practice.

Please advise.

[Thomas Coleman]

Same blank.  Same string height , and all other specs.  There is no reason to change any of those specs. 

[PASEWICZ]

It depends on the instrument, not the model.

[______]

12 hours ago, Jerry Pasewicz said:

It depends on the instrument, not the model.

That's the way I feel it. Good to hear same words from such a pro.

[martin swan]

What do you mean exactly by "a Guarneri"?

[LongNeck]

3 hours ago, martin swan said:

What do you mean exactly by "a Guarneri"?

It has two labels, both viewed through the bass f-hole:

Label:
Copie
Josef Guarnerius del Jesu
zhotovil mistr
FRANTISEK L. DUCHON
Nachod 1920.

Other label:
Joseph Guarnerius fecit
Cremonae Anno 1714  IHS

 

[martin swan]

I don't think you should assume that a C20 Czech/Schoenbach violin with an apocryphal Guarneri label has anything to do with a Guarneri model. Mostly "Guarneri" labelled violins from this part of the world are just very standard trade violins with the usual arching, and maybe a bit of additional length to the f-holes or some concessionary pointy bits.

We've had some discussion recently about whether high arched violins benefit from a lower bridge than a flatter arched violin, but even amongst genuine del Gesus there's quite a bit of variation in arching height.

I would think the bridge blank on any violin should be chosen firstly for width in accordance with the position of the bassbar, and then cut to fit the exact arching of the specific violin with complete disregard for what the label says.

 

[LongNeck]

Of course I intend to fit the feet precisely to the top.

BTW I ordered what I thought was a Teller bridge blank, but when it arrived I was unhappy to find that it was a "fitted" bridge, and too short or barely tall enough for sufficient string height on any of my violins.  The fit of its feet on the "Gaurneri" in question was horrible, while the fit wasn't nearly as bad on the "Strads".  Of course I'm not using it, but it indicated a difference in arching.

Okay, I then I'll compare the bass bar position of this violin to that of the others.

[not telling]

They make fitted cut bridges? This is not the bridge with the little ratchet on the side to make the feet adjust, right? I saw something like that in the Metropolitan catalog and tried to unsee it. I guess I'm surprised at the concept of precut normal bridges. I can't imagine that being useful. Can you return it? 

[LongNeck]

I did return it, and after some little negotiation, the seller promised to refund the price and shipping.  It cost me a dollar for return postage.

No, not talking about the bridges with the jointed revolving feet.  Apparently the idea is that you just stick it under the strings, and you're good to go.  Like I said, the bridge was so short that I couldn't have taken much wood off the feet, or the strings might be too low.  The product concept is more or less appalling, but they seem to sell a lot of them (many hundreds) on the big auction site.  The listing didn't have any description at all---just a title and a photo.   The title didn't include the words 'fitted' or 'pre-cut' or similar.  The seller acted like I was supposed to know from the picture that it was fitted, also stated in poor English that a shop would charge $50 to fit a bridge, and so  I shouldn't have expected much for $10.  Ha, ha, what I expected was a bridge blank, and I would cut it myself.  I measured the height/width proportion of the pictured bridge, and it did not match the proportion of the bridge I received.  I looked through the Teller catalog, and they do not list any fitted bridges.  It was a 3-star with an ebony V-inlay.  I emailed Teller asking whether it was their off-the-shelf product or whether someone modifies these after Teller sells them.  I haven't heard back from them yet.

[martin swan]

https://www.dictum.com/en/musical-instrument-making/bridges-accessories/teller/340611/teller-bridge-fitted-violin-44-41-mm?ftr=_8__96.2_1_12_12

I assume the idea is that a standard bridge on a standard trade violin is about 34mm high at the centre point. This seems to require a bit of minor fitting of the feet and of the top curve, otherwise ready to go.

What's not to like ?

[LongNeck]

I didn't like that the feet would be left a lot thicker than usual.  IDK how important that is.  And the bridge is left damn thick too, as thick as a blank.  It seems that all it saves is cutting the top edge.  It doesn't look like much of a gain, and it seems to reduce options.  Not sure what fitting of the top curve you have in mind. 

Maybe you're pulling my leg.

[not telling]

He isn't, other than saying that the needed adjustment is minor. I'm sure the devil is glad to have such a wonderful advocate as Martin. Do you use a bridge template? Many luthiers do bridges by eye, as they have been taught to do. Templates are useful though..the professional luthiers I know always use a template.

[martin swan]

I always forget that in American English, "irony" means "tastes like iron" 

I think these fitted bridges would have a very limited application, for instance if you were setting up masses of very standard trade violins, otherwise it seems that there are probably very few violins they would actually fit without a good deal of additional fitting.

[ctanzio]

As far as I can tell, the height of the bridge foot at the edges is a non-issue for tonal performance. The fit of the foot to the surface is the critical dimension. But structurally, making the foot "too thin" towards the outer edges will dramatically increase the local pressure on the varnish and cause it to compress and deform over time, and sometimes to flake off. The outer edges of the foot will bear progressively less of the string pressure than the center as the edges are thinned. 

In the structural engineering world, considerable research has been done on the design on these "bearing surfaces". So when there is metal-on-metal or wood-on-wood contact, one can look in a manual of standard practices and it will tell you how thick the footing should be to prevent permanent deformation of the surface. The challenge in the violin world is to apply it to the variety of varnishes one encounters.