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  #1  
Old 01-09-2020, 10:53 PM
BRVC BRVC is offline
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Default Gibson b 25 12 with warped top

I have a Gibson spruce top b 25 12 guitar built probably in the early to mid 1960ís. The pressure from the strings is causing a belly in the lower bout. I know a trapeze would solve the problem, but I read that trapezes dampen the sound. Any ideas on solutions would be much appreciated. Thanks!
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Old 01-09-2020, 11:35 PM
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JLD Bridge Doctor might be an option.

Brass pin mount: The pin-mounted version of the JLD Bridge Doctor attaches beneath the bridge using a threaded brass bridge pin. The strings mount horizontally through the tops of the matching brass bridge pins (included).

StewMac Tech Tip: We recommend the brass pin mount version for 12-string guitars.


Here's a link to them at Stewmac - https://www.stewmac.com/Luthier_Tool...ge_Doctor.html
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Old 01-10-2020, 04:13 AM
robroy robroy is online now
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I second the bridge doctor solution. I had the same guitar with the big wooden bridge and a warped top and it worked wonders.
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Old 01-10-2020, 07:57 AM
BRVC BRVC is offline
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Quote:
Originally Posted by Brucebubs View Post
JLD Bridge Doctor might be an option.

Brass pin mount: The pin-mounted version of the JLD Bridge Doctor attaches beneath the bridge using a threaded brass bridge pin. The strings mount horizontally through the tops of the matching brass bridge pins (included).

StewMac Tech Tip: We recommend the brass pin mount version for 12-string guitars.


Here's a link to them at Stewmac - https://www.stewmac.com/Luthier_Tool...ge_Doctor.html
Brucebubs and Robroy, wow, this looks like the perfect solution! Thank you! Iím no luthier, but I am fairly handy, so I imagine I can install it myself. Iíll order one today.
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Old 01-10-2020, 08:22 AM
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I have a 1964 B45-12 pin bridge guitar, these are lightly built 12 strings, and should be tuned down a full step. My guitar has a belly below the bridge and a dip in the top at the sound hole area, the bridge has rocked slightly forward. To a certain extent this is normal. I have seen a photo of Gordon Lightfoot's 1964 B45-12 dated 1966. It is a photo of the piece of paper taped to the side of guitar with the set list written on it, and the photo was taken from a shallow angle to the top, and it shows that although the guitar is only about two years old, it has the described deflection in the top almost exactly like my guitar has now, more than fifty years later. I have owned this guitar for about 20 years and the top is stable and has not seemed to move any further. My point is that this may not be a problem and could be normal deflection. It is also my opinion that a Bridge Doctor may change the tone of the instrument.
I few pictures would be helpful.
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Old 01-10-2020, 03:43 PM
zombywoof zombywoof is offline
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I own a 1961 B45-12 (and previously owned a 1963 B45-12). 1961 was the first year Gibson offered them and they only turned out 77 of them a number of which twisted themselves apart. The slope shoulder versions are distinctly different sounding then the later square shoulder guitars. The '61 has a slight bit of distortion around the soundhole but according to my repair guy as it iis minimal and impacts nothing just let it be.

As has been noted Gibson beefed up the bracing in the B45-12 in late-1964 by adding sister braces to the lower leg of the X. Whether the B25-12 was subjected to the same fate though I do not have a clue as I have never owned one. If your top though is badly distorted and you go the Bridge Doctor route, you will have to keep an eye on the bracing as it can detach as the top starts rising. The Weldwood cement that Gibson began using in the 1960s was not the best choice.

By the way, with the B45-12 the easiest way to tell if it is a pre-1965 guitar is the two triangle doodads on the headstock. If they have a rounded tip they are early. It pointed they are post-64 instruments.
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Last edited by zombywoof; 01-10-2020 at 03:55 PM.
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Old 01-10-2020, 03:52 PM
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Quote:
Originally Posted by zombywoof View Post
I own a 1961 B45-12 (and previously owned a 1963 B45-12). 1961 was the first year Gibson offered them and they only turned out 77 of them a number of which twisted themselves apart. The slope shoulder versions are distinctly different sounding then the later square shoulder guitars. The '61 has a slight bit of distortion around the soundhole but according to my repair guy as it iis minimal and mpacts nothing just let it be.

As has been noted Gibson beefed up the bracing in the B45-12 in late-1964 by adding sister braces to the lower leg of the X. Whether the B25-12 was subjected to the same fate though I do not have a clue as I have never owned one. If your top though is badly distorted and you go the Bridge Doctor route, you will have to keep an eye on the bracing as it can detach as the top deforms.

By the way, with the B45-12 the easiest way to tell if it is a pre-1965 guitar is the two triangle doodads on the headstock. If they have a rounded tip they are early. It pointed they are post-64 instruments.
Good information, I'm always interested in learning more about these guitars, thanks Zombywoof.
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Old 01-10-2020, 05:43 PM
zombywoof zombywoof is offline
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Quote:
Originally Posted by Bill Kraus View Post
Good information, I'm always interested in learning more about these guitars, thanks Zombywoof.
Somewhere I have a sketch of the bracing footprint of a post-1964 B45-12. If I can find it I will post it. Here is an old interview with Leo Kotte where he talks about the benefits of the ADJ saddle bridge on his Gibson 12 string.

http://www.guitarmusic.org/kottke/ggpa773.html
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Last edited by zombywoof; 01-10-2020 at 05:48 PM.
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Old 01-10-2020, 06:44 PM
zombywoof zombywoof is offline
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Here is the bracing footprint of a post-64 B45-12. You can see where the braces were added along the lower legs of the X.

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  #10  
Old 01-10-2020, 06:53 PM
BRVC BRVC is offline
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Quote:
Originally Posted by zombywoof View Post
I own a 1961 B45-12 (and previously owned a 1963 B45-12). 1961 was the first year Gibson offered them and they only turned out 77 of them a number of which twisted themselves apart. The slope shoulder versions are distinctly different sounding then the later square shoulder guitars. The '61 has a slight bit of distortion around the soundhole but according to my repair guy as it iis minimal and impacts nothing just let it be.

As has been noted Gibson beefed up the bracing in the B45-12 in late-1964 by adding sister braces to the lower leg of the X. Whether the B25-12 was subjected to the same fate though I do not have a clue as I have never owned one. If your top though is badly distorted and you go the Bridge Doctor route, you will have to keep an eye on the bracing as it can detach as the top starts rising. The Weldwood cement that Gibson began using in the 1960s was not the best choice.

By the way, with the B45-12 the easiest way to tell if it is a pre-1965 guitar is the two triangle doodads on the headstock. If they have a rounded tip they are early. It pointed they are post-64 instruments.
Zombiewoof, thanks! I am not sure of the date on mine, but have read that the later B 25ís have trapezes and mind doesnít. Iím pretty sure miner is a B 25, but donít actually know for certain. It just looks like the B 25ís Iíve seen online. It doesnít say on it anywhere what it is. Just a serial number.
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  #11  
Old 01-10-2020, 06:56 PM
BRVC BRVC is offline
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Quote:
Originally Posted by Bill Kraus View Post
I have a 1964 B45-12 pin bridge guitar, these are lightly built 12 strings, and should be tuned down a full step. My guitar has a belly below the bridge and a dip in the top at the sound hole area, the bridge has rocked slightly forward. To a certain extent this is normal. I have seen a photo of Gordon Lightfoot's 1964 B45-12 dated 1966. It is a photo of the piece of paper taped to the side of guitar with the set list written on it, and the photo was taken from a shallow angle to the top, and it shows that although the guitar is only about two years old, it has the described deflection in the top almost exactly like my guitar has now, more than fifty years later. I have owned this guitar for about 20 years and the top is stable and has not seemed to move any further. My point is that this may not be a problem and could be normal deflection. It is also my opinion that a Bridge Doctor may change the tone of the instrument.
I few pictures would be helpful.
Bill, I will try to post a few pictures. I need to upgrade my membership, I believe.
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  #12  
Old 02-05-2020, 03:30 PM
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BRVC I sent you a private message.
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  #13  
Old 02-05-2020, 06:47 PM
mirwa mirwa is offline
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The guitar is decent enough not to do a hack repair on, visit a local luthier and get them to assess it first.

Steve
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  #14  
Old 02-08-2020, 01:45 PM
Howard Klepper Howard Klepper is offline
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I am in awe of those who are able to diagnose the problem and prescribe a fix (in this case a cheap, quickie fix--the Bridge Doctor--that should be a last resort and only for a guitar not worth a good repair) for a guitar based only on being told that it has a belly. No measurements. No photos. No reason given yet to think there is even a problem that needs fixing--a belly is usually not a flaw at all.
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Last edited by Howard Klepper; 02-09-2020 at 02:57 PM.
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