Bending of the Spruce Top - Cordoba Gk Studio Negra

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DavidLobo

Posts: 2
Joined: Aug. 10 2021

Bending of the Spruce Top - Cordoba ...

Hello everyone, :)

i just recognized that the top of my guitar is bending.
On the internet i just found some articles about the bending behind the bridge (traditional Spanish buildingstyle).
But i measured with a ruler a slight bending of the top between the soundhole and the bridge (to the inside). Now i worry if my bridge is rising. The guitar is quite new, maybe 2 months.

Is there anybody who knows if this is normal?

Sorry but i am quite new in the flamencoworld.

thanks for you help

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 10 2021 21:05:20

Echi

Posts: 1131
Joined: Jan. 11 2013

RE: Bending of the Spruce Top - Cord... (in reply to DavidLobo)

I suppose you mean the top doming. In this case yes, it's normal.

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 10 2021 21:09:23

Tom Blackshear

Posts: 2304
Joined: Apr. 15 2008

RE: Bending of the Spruce Top - Cord... (in reply to DavidLobo)

quote:

i measured with a ruler a slight bending of the top between the sound-hole and the bridge (to the inside). Now i worry if my bridge is rising. The guitar is quite new,

Most flamenco guitars that are loosely braced do bend between the sound hole and bridge a little. Many times this bending causes the bridge to rock forward a fraction, and if too much then it may cause a little harmonic off set, but most of the time, no.

50 years ago, I heard a Spanish builder say that if the top didn't bend a little, it was not a good one

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REPORT THIS POST AS INAPPROPRIATE | Date Aug. 10 2021 22:15:36

DavidLobo

Posts: 2
Joined: Aug. 10 2021

RE: Bending of the Spruce Top - Cord... (in reply to DavidLobo)

Thanks for the replies!

Now i am relaxed and can go on practicing.
I really fell in love with the sound of this guitar, would be sad to send it back.

And Tom, what do you mean with loosely braced?
Is this standard for flamenco guitars or you mean a construction issue?

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 10 2021 23:00:20

Echi

Posts: 1131
Joined: Jan. 11 2013

RE: Bending of the Spruce Top - Cord... (in reply to DavidLobo)

The top is supported by a sort of fan bracing made of wood underneath. If you want the top to bend forward under the string tension, the bracing has not to be too stiff and the top not too thick.
I used to have a guitar made by German Perez Baranco of Granada: the top was 1.5 mm thick and the main transverse bar was shaped as an arc. As a consequence the top used to have an extremely pronounced S shape and yet it was fully functional and good sounding.

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 10 2021 23:58:51

Tom Blackshear

Posts: 2304
Joined: Apr. 15 2008

RE: Bending of the Spruce Top - Cord... (in reply to DavidLobo)

quote:

And Tom, what do you mean with loosely braced?
Is this standard for flamenco guitars or you mean a construction issue?

Like Echi said, a lot of this depends on the top thickness, along with the number of fan braces and how they are placed on the top.

Then, it is according to the builder's knowledge, how to articulate the top, ( with certain top graduation techniques, ) to get a response that is pleasing to the performing artist.

I've come to believe in the 58 years of my building practice, that tonal quality and proper top tension are the two most important things for the flamenco guitar. After this, cosmetic value. etc.

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Tom Blackshear Guitar maker

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 11 2021 18:12:02

zendalex

Posts: 137
Joined: Sep. 4 2010
From: New York area

RE: Bending of the Spruce Top - Cord... (in reply to Tom Blackshear)

Hi, my Glenn Cannin also bent just about a year ago (its about 10 years old now), and in that same spot.
I was blaming humidity - so this might not even be the humidity then?
Just the instrument maturing, so to speak?

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 11 2021 21:51:15

Echi

Posts: 1131
Joined: Jan. 11 2013

RE: Bending of the Spruce Top - Cord... (in reply to DavidLobo)

Is that a double top?
Some double top are purposely loosely braced and therefore show a concavity in front of the bridge.
There’s a very nice interview of Matthias Dammann in the web. For those who don’t know, the guy is probably the most sought after modern guitar maker and the first one finding out the double tops method.
Anyway, he said he looks after a huge bending of the top, so that even his bridge rocks up to 5 mm forward his original position in a couple of months. He studied a lot the geometry of the guitars of Torres.
Dammann is a little extreme, the closest example of this idea I’ve seen is the Barranco I spoke about above.

All my current guitars but one don’t show an evident bending in front of the bridge though.

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 11 2021 23:22:52

Tom Blackshear

Posts: 2304
Joined: Apr. 15 2008

RE: Bending of the Spruce Top - Cord... (in reply to Echi)

quote:

Anyway, he said he looks after a huge bending of the top, so that even his bridge rocks up to 5 mm forward his original position in a couple of months.

Echi, did you mean .5mm?

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Tom Blackshear Guitar maker

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 12 2021 13:30:46

Echi

Posts: 1131
Joined: Jan. 11 2013

RE: Bending of the Spruce Top - Cord... (in reply to DavidLobo)

I meant 5 mm. He builds and glues the bridge foreseeing from 3 to 5 mm movement of the bridge bone.

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 12 2021 14:08:49

zendalex

Posts: 137
Joined: Sep. 4 2010
From: New York area

RE: Bending of the Spruce Top - Cord... (in reply to Echi)

quote:

Is that a double top?

Right.. Double top. So I should stop worrying completely then?

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 12 2021 15:56:34

Echi

Posts: 1131
Joined: Jan. 11 2013

RE: Bending of the Spruce Top - Cord... (in reply to DavidLobo)

Well, not all the double tops are meant to bend that much. Dammann brought it to the extreme really.
In general I wouldn’t worry, particularly if the action numbers are correct.
You have a problem particularly when one of the tranverse bars is too light but if this was the case you would notice it.

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 12 2021 23:16:43

Ricardo

Posts: 14797
Joined: Dec. 14 2004
From: Washington DC

RE: Bending of the Spruce Top - Cord... (in reply to Echi)

I find it hard to visualize a bridge rocking forward that much to achieve decent action over 12th fret, yet staying at 7-8mm at bridge. It would imply that before the “rocking”, the guitar would be super low and buzz like a banjo.

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REPORT THIS POST AS INAPPROPRIATE | Date Aug. 13 2021 18:02:29

Echi

Posts: 1131
Joined: Jan. 11 2013

RE: Bending of the Spruce Top - Cord... (in reply to DavidLobo)

In my understanding the bridge saddle is originally not set at 90 degrees but with a certain angle foreseeing the bridge will rock to a specific amount.
Also Dammann makes classical guitars: with a flamenco set up you would have less room to achieve it.
It’s interesting that the idea comes from observing the geometry of the Torres guitar: Notoriously the guitars of Torres are very lightly made, considering they were born for gut strings and their age. Yet some concert players got an extremely good projection and bright trebles with medium/hard tension nylon strings: Here the idea to use a composite membrane able to bend as much as a Torres spruce top without the risk of collapse.
Current Dammann guitars are not anymore made with a nomex core though.

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 13 2021 23:48:54

Tom Blackshear

Posts: 2304
Joined: Apr. 15 2008

RE: Bending of the Spruce Top - Cord... (in reply to Echi)

quote:

I meant 5 mm. He builds and glues the bridge foreseeing from 3 to 5 mm movement of the bridge bone.

So what you mean is that he marks the bridge an additional length of 3 to 5mm on the top so that when he strings the guitar up to concert pitch, the string torque pulls the bridge forward 3 to 5mm to the correct harmonic measurement.

Boy! that's a lot of top flex.

My Reyes plan has about .5mm adjustment for the bridge to rock forward.

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 14 2021 2:21:04

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: Bending of the Spruce Top - Cord... (in reply to zendalex)

quote:

Right.. Double top. So I should stop worrying completely then?

Hi Zendalex, I think you should have a qualified tech take a look at it. Mainly because you mention the distortion only became noticeable in the past year or so and wasn’t that way for the first nine. Unless you’ve changed string gauge to a higher tension, it could mean something may be going on internally, like a brace failure or top delamination. Regardless, it’s probably safest to have someone physically check the guitar over.

REPORT THIS POST AS INAPPROPRIATE | Date Aug. 14 2021 4:34:20