Curved guitar top, dangerous?

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georgemarousi
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Curved guitar top, dangerous?

Post by georgemarousi » Wed May 08, 2019 2:34 pm

Hi !

I have checked out an impressive used lattice-top guitar ( wood-lattice, not carbon ), about 10 years old, with a thin cedar top.

My concern is that I have noticed the guitar top is pretty much twisted around the bridge. You know, from bridge towards the edge it is bumps up, while from the bridge to the soundhole it is much suppressed inwards, creating an big "S" shape when looked from the side of the top.

I dont have a photo, but i guess that the maximum distance from a theoretical straight line would be between 0.5 to 1.0 cm ! I worry that the top may get worse twisted over time or even worse, brake ( ? ). Is my concern right, is it as risky as it looks to me ? What are your thoughts?

Best regards,
George.
Paulino Bernabe Especial 2009
Panagi Brothers 70's
Furch FN 23 CR ( nylon )
Juan Martinez nr 55 2014 (the comeback)
Yamaha cg 110 1988 (the 1st)
Gibson j45
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souldier
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Re: Curved guitar top, dangerous?

Post by souldier » Wed May 08, 2019 2:58 pm

Hard to tell without seeing it, but it is usually safe within reason. I have a 40 year old guitar that has a bit of that but is perfectly fine. If the deformation is too extreme, then I'd stay away. If you get a chance to take a picture and show it to us, that would definitely help.
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James Lister
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Re: Curved guitar top, dangerous?

Post by James Lister » Thu May 09, 2019 9:59 am

Some deformation is normal - if the top doesn't deform at least a little under string tension, then it is overbuilt. Having said that, if it has deformed by anywhere near 1cm, I'd advise walking away from it - that's way too much for a 10 year old guitar.

James
James Lister, luthier, Sheffield UK

astro64
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Re: Curved guitar top, dangerous?

Post by astro64 » Thu May 09, 2019 12:28 pm

Does the guitar still play in tune? If the bridge rolled forward a lot, and it was not by design choice, then it may be playing out of tune since the saddle is no longer where it is supposed to be.

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Beowulf
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Re: Curved guitar top, dangerous?

Post by Beowulf » Thu May 09, 2019 2:16 pm

My 48 year old Yamaha GC-10 has ~0.5cm at most and this will vary a bit with humidity levels; at 1.0cm...I'd be concerned. Is there a difference with lattice-braced sound boards?
1971 Yamaha GC-10 (Hideyuki Ezaki)
2017 Yamaha GC82S (Akio Naniki/Naohiro Kawashima)

UKsteve
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Re: Curved guitar top, dangerous?

Post by UKsteve » Thu May 09, 2019 3:43 pm

James Lister wrote:
Thu May 09, 2019 9:59 am
Some deformation is normal - if the top doesn't deform at least a little under string tension, then it is overbuilt. Having said that, if it has deformed by anywhere near 1cm, I'd advise walking away from it - that's way too much for a 10 year old guitar.
^this all day long.

Some deformation under string tension is a sign of a lightly built top (as is perceiving the bracing underneath) that is likely to be responsive and sound great but too much, and its a sign of imminent implosion: Achieving that fine balance is what characterises a great luthier.

astro64
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Re: Curved guitar top, dangerous?

Post by astro64 » Thu May 09, 2019 4:48 pm

One of my guitars has lived at "imminent explosion" for 15 years. It seems the warping was built into the design. But I agree that it can be disconcerting to look at....

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georgemarousi
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Re: Curved guitar top, dangerous?

Post by georgemarousi » Thu May 09, 2019 5:05 pm

Hi again,

The owner was polite enough to send me a photo of the guitar, what is your opinion ? I m afraid that it is curved too much

( not 100% sideways but you can see the curve from the mirroring of the strings )

Image
Paulino Bernabe Especial 2009
Panagi Brothers 70's
Furch FN 23 CR ( nylon )
Juan Martinez nr 55 2014 (the comeback)
Yamaha cg 110 1988 (the 1st)
Gibson j45
--
2014: the comeback

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Beowulf
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Re: Curved guitar top, dangerous?

Post by Beowulf » Thu May 09, 2019 6:16 pm

What is the string tension of the set on the instrument?
1971 Yamaha GC-10 (Hideyuki Ezaki)
2017 Yamaha GC82S (Akio Naniki/Naohiro Kawashima)

Petter
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Re: Curved guitar top, dangerous?

Post by Petter » Thu May 09, 2019 9:14 pm

Looks more like an imminent disaster rather than a lightly built guitar tbh..
1976 Sakazo Nakade No. 2000

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rojarosguitar
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Re: Curved guitar top, dangerous?

Post by rojarosguitar » Thu May 09, 2019 9:45 pm

I saw quite a strong bending like that in Atocha Conde flamencas last autumn when I was there. Seems some makers calculate that in.
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singlechange
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Re: Curved guitar top, dangerous?

Post by singlechange » Fri May 10, 2019 1:43 am

Just today I was discussing this very same condition with the top at a luthier's workshop. My 1957 Modesto Borreguero has this issue on the super thin sound top. The luthier commented that a lot of the old Torres style guitars get this way and told me not to worry. The big sound is still there in spades after 60 years. The action is still good and the intonation also very good.

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georgemarousi
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Re: Curved guitar top, dangerous?

Post by georgemarousi » Fri May 10, 2019 5:57 am

Beowulf wrote:
Thu May 09, 2019 6:16 pm
What is the string tension of the set on the instrument?
Daddario Medium tension with carbon trebles
Paulino Bernabe Especial 2009
Panagi Brothers 70's
Furch FN 23 CR ( nylon )
Juan Martinez nr 55 2014 (the comeback)
Yamaha cg 110 1988 (the 1st)
Gibson j45
--
2014: the comeback

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georgemarousi
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Joined: Thu Apr 14, 2016 8:10 am

Re: Curved guitar top, dangerous?

Post by georgemarousi » Fri May 10, 2019 12:12 pm

A reversed question is, anyone saw a thin CG curved top brake after some years ?! :shock:
Paulino Bernabe Especial 2009
Panagi Brothers 70's
Furch FN 23 CR ( nylon )
Juan Martinez nr 55 2014 (the comeback)
Yamaha cg 110 1988 (the 1st)
Gibson j45
--
2014: the comeback

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souldier
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Location: Toronto, Canada

Re: Curved guitar top, dangerous?

Post by souldier » Fri May 10, 2019 12:29 pm

georgemarousi wrote:
Thu May 09, 2019 5:05 pm
Hi again,

The owner was polite enough to send me a photo of the guitar, what is your opinion ? I m afraid that it is curved too much

( not 100% sideways but you can see the curve from the mirroring of the strings )
That definitely has a bit more deformation than my guitar. If you ask me though, I think it will still hold up, as long as you don't use excessively high tension strings and properly humidify the guitar. You never know however... If you have any doubt and if it would constantly bother you, then I'd definitely pass and look elsewhere. A key principle when purchasing a guitar is to remember that there are innumerable options out there. Don't get too caught up on one thinking that you'll never find something you like more at a better price. Keep patiently looking, and you're guaranteed to find another guitar that you like without the potential issues.
"Success grants its rewards to a few, but is the dream of the multitudes.
Excellence is available to all, but is accepted only by a few." - Christopher Parkening

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