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I'm having troubles understanding the function of the bridge patch used by many (most?) on classical guitars. I guess the thing that confuses it for me is that they seem to be close to the same width as the bridge so I don't see how they help in spreading the load from the strings as is the case for a steel string guitar bridge plate that is wider than the bridge. It also seems to me that notching the fan braces right in the area that you want strength would be counter-productive. I'm sure I'm just displaying my ignorance here, but if someone can explain it to me, I'd appreciate it.

Thanks,
Pat

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There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

Torres did not use it, and Romanillos stopped using it years ago deciding it does nothing. Some think it acts towards reducing stress in the plate-bridge sandwich. Tonally it does little: it adds a bit of weight and stiffness at the same time, so nothing changes really, except the "impedance". More weight, harder to move, but more headroom, all this in tiny, hard to perceive amounts. I think you can get a larger amount of variety in terms of weight and stiffness from the various bridge pieces used.

I do not use it but I would for a very light and flexible bridge. Some rosewood pieces can be unusually light. You either make a clunky looking big bridge to compensate, either compensate with something in the interior and make the bridge look normal...

Another case I see is with very heavy rosewood. Once you thinned to a reasonable weight, it will have very thin floppy wings....

I really do not appreciate the fan notching too.

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Build log

Alexandru has given a good explanation. I built my first 20 classical guitars or so without a bridge patch. I then started using them to experiment. I remember Richard Bruné telling me that he used them and thought it added "uniformity" to the cross grain stiffness. On the last few guitars I have been experimenting with the tornavoz and have removed the bridge patch. Like Alexandru said, it is nice being able to attach the fan braces without having to notch them first.

The second classical guitar I built I didn't notch the braces but rather I notched out the bridge patch right to the top such that there were individual patches between the bracing. I actually did this because I didn't read the directions properly. Looking back, I see nothing wrong with doing that and it would keep your bracing at full strength, but then properly notching is probably just as well. I'm thinking on my next build I will eliminate the patch all together.

I've used them & have not used them .
I find the guitars without them are usually louder .
very traditional sounding tone.

The 51 Barbero plan by Brune' shows pieces added between the braces so they were not notched.
I've used this style on many guitars -especially Flamencos and I like the results.
I've experimented with the type of woods, thicknesses,and width.
It's hard to say if it was the patches or something else that made the guitars sound good .
If you do use a pad do not leave it more than 1mm thick or you'll have a stiff ,tight tone to your guitar.
Mike

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Mike Collins

In a lecture that he gave to our guitarmaking group, Ervin Somogyi offered the following.

The bridge, being glued to the top, restricts the expansion and contraction of the top in that area due to changes in humidity. But only on one side.

The patch does the same for the other side, making the top more stable with changes in humidity. Without a patch, one side moves and the other side doesn't.

It's not about strength, coupling of braces, or transmission of sound.

Makes sense to me. And it's consistent with the woodworking rule of thumb that what you do to one side of the wood, you do to the other, as with finish. Which is probably the origin of the practice, as many early luthiers began as woodworkers.

So, Somogyi advocates a bridge patch, Antonio de Torres never used one. Whose opinion should I follow? Oh I know I'l go with the greatest builder of guitars the world has ever known. So no patch for me.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

No bridge patch for me either.
I have indeed noticed some very minor movement of the top due to cross grain expansion in some of my older (20+ years) guitars as mentioned above. The only reason it was noticable at all is because it is right against the smooth contour of the bridge mating surface.
The requirement of notching out the fan braces to accomodate the pad seems to me the greater of two evils so I've chosen to live with the lesser.

A tops longitual stiffness is much greater than its cross one.
Maybe notching the fans helps to make them more flexible in that direction.
Just a thought.

Mike

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Mike Collins

This, I really do not comprehend but who am I to question Hauser. Thanks for the replies. I've decided to go sans patch since I still don't really yet see a benefit yet I can understand a downside.

Cheers,
Pat

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There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

One interesting thing to note about the Hauser I design is that in the area where he's notched out the fan braces over the bridge patch he's also left them square in cross section rather than "gable end shaped" as they are in the rest of their length.

Take that Mike!!!<grin>

Do you guys know any builder using the patch before Hauser? Maybe those building with pins? Perhaps Hauser used the patch in his Viennese style builds and felt more comfortable using it in his Spanish builds too.


In terms of humidity, what I see happening is that the top shrinks across the grain and at a point that is prevented by the bridge. Lengthwise shrinkage is quite imperceptible. Maybe a patch increases the chance that a shrinkage crack stops at the bridge instead of crossing under or beyond the bridge.

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Build log

I use it, and for me it does have at least 2 benefits:

First and formost, for an additional 2 grams, my extended bridge patch has a very noticeable impact on the lateral stiffness and brings the frequency response of the top up a full tone. This means that I can go lighter on the bracing without losing on the high end (this is as technical as I can get... ). I have not noticed any difference in volume with or without the patch.

Secondly, with the very steep changes in RH that we get here up North, the bridge patch will help diminish the contraction/expension differences between the Rosewood bridge and the top. This difference can lead to cracks or buckling of the top where it is in contact with the bridge.

The extended bridge patch (it runs almost all the way to the sides) works for what I do, but it may or may not have as much of an impact on what others are doing. It's all part of a system, and every system responds in its own way to the numerous variables that it's composed of. My advise is that if you want to raise the frequency of your soundboard without adding a lot of weight, give it a try. It worked for me.

Cheers

Pat

I noticed that Ramirez uses them a lot, but I think Ramirez is notorious for guitars cracking, so I think that the patch for Ramirez may be an attempt to restrict cracking.

Here is the bridge patch on a 1959 Hernandez Y Aguado:

Dave -are those initials circled??

There is NO definative answer to this question.
Only what works for each maker to achieve his or her sound.

Love you reply David !!!!

All things -weight,stiffness,size of box & port(s)would have to be the same to give a so to speak definitive (scientific) answer-Maybe!!
Mike

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Mike Collins

I just looked inside a 1979 Contreras and aside from four curved fan braces and one central straight brace there were two thin cross grain spruce patches about 11/2 inch square
under the ends of the bridge wings.....best of both worlds??
My best sounding guitars do not have a BP

Interesting discussion! Thanks!

Steve-
Do you have any pictures of the details of a Contreras?
I'm thinking of building a guitar with some Contreras features- I know that Contreras Sr was quite an innovator, so lots to choose from! I'm thinking of 'double top' (actually more 'double back', as I understand it.)

Cheers
John

These posts should help us all to find the answer -if there is one !


Mike

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Mike Collins

Mike, It's actually an ink stamp with a circle and "Hernandez Y Aguado" around the periphery.The number of the guitar is written on the spruce in the middle of the circle.

Maybe I’m kicking a dead horse here but I think the bridge patch will increase the chance of the top cracking. The top will bow up or flatten with humid changes. Restricting this by making the bridge stiffer might be good for the sound of a particular guitar but the wood movement will be forced to take place between the bridge ends and the sides.
Differences in speed of wood movement between various parts would be better slowed down with a light coat of shellac on the inside of the top. This would be lighter too. I sometimes wonder about the impact of super stiff sides in this regard. A guitar has to accommodate moisture swings, not fight them. that’s why stiff brace ends tend to be the ones that pop loose

Make a guitar witha bridge patch or bar and glue the bridge on with nothing supporting the top (traditional spanish technique) You will see that the surfaces mate very well. Now glue the bridge on a guitar with no bridge patch and you will see that the top has slightly less contact with the bridge between the fan braces. (Use newspaper as a feeler gauge when the bridge is coupled). I use a patch on my guitars and none on the Torres copy and the flamenco and both work well but I feel better about the contact (and hence the glue joint) when I use a patch. The plywood effect also reduces what David has observed but I am not sure that Somogyi is right in his explanation of why.

John Ray
Granada

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John Ray
Granada, Spain
blog: http://www.granadaexpert.com/johnray/

John, I believe that would only be true if you didn't use a bridge caul to clamp the bridge to the top. I don't use a patch, and my bridge has full contact all the way across, however, my fan braces do telegraph slightly in the thinner areas of the top, mostly between the bridge and the tail.

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Waddy

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