iangibson Posted May 5, 2011 Share Posted May 5, 2011 Hi all. My 1989 J-180 and 2004 60's J-200 seem to have the neck/fingerboard front-bowing from the neck joint area and no, it's not an usual gentle curve that you can correct easily by turning the tross rod, but rather the fingerboard is straight from the neck joint to the end of the fretboard and from the neck joint to the string nut, with a sharp angle just where the neck meets the body. The string action is 8/64" on low E at the 12th fret. I knew the truss rod would not alleviate this problem, but anyway tried turning it 180 degrees clock-wise in three turns with 30-min intervals each turn. All it did was back-bowing the lower portion of the neck (like from the nut down to the 5-7th-ish fret). The action at the 12th fret still reads 7 to 8/64". I’ll take them into a repair shop for a professional view about the neck condition as soon as I get time this weekend or next week, but I think these necks need straightening with a jig and heat application (neck ironing). If that's the treatment these necks need indeed, I think whether it works or not is dependent on what kind of glue these guitars are constructed with. I don't know if the customer service reads and replies to a post here on this forum, but if not, I'd appreciate any information from any forum members about the types of adhesive Gibson has used on their acoustics since late-80's up to date. I'd like to know if heat-melting adhesive such as hide glue was used on these guitars, between the neck and fingerboard in particular. Thanks in advance for your input. Link to comment Share on other sites More sharing options...
BigKahune Posted May 5, 2011 Share Posted May 5, 2011 . Sorry to hear about your misfortune. Besides straitening the necks, the truss rods will most likely need replacing. Most guitars are built with glues that are heat/steam sensitive, which is what's used in some disassembly for repair procedures. This is also why warm, moist air can cause all kinds of problems for glued wooden instruments. One guitar neck bending like you describe is very unusual. Two, belonging the same owner, is unusual in the extreme. Please forgive my curiosity - How are the guitars stored? What is the storage environment (location, temp, humidity), and how consistent is it? Link to comment Share on other sites More sharing options...
Hogeye Posted May 5, 2011 Share Posted May 5, 2011 Hi all. My 1989 J-180 and 2004 60's J-200 seem to have the neck/fingerboard front-bowing from the neck joint area and no, it's not an usual gentle curve that you can correct easily by turning the tross rod, but rather the fingerboard is straight from the neck joint to the end of the fretboard and from the neck joint to the string nut, with a sharp angle just where the neck meets the body. The string action is 8/64" on low E at the 12th fret. I knew the truss rod would not alleviate this problem, but anyway tried turning it 180 degrees clock-wise in three turns with 30-min intervals each turn. All it did was back-bowing the lower portion of the neck (like from the nut down to the 5-7th-ish fret). The action at the 12th fret still reads 7 to 8/64". I’ll take them into a repair shop for a professional view about the neck condition as soon as I get time this weekend or next week, but I think these necks need straightening with a jig and heat application (neck ironing). If that's the treatment these necks need indeed, I think whether it works or not is dependent on what kind of glue these guitars are constructed with. I don't know if the customer service reads and replies to a post here on this forum, but if not, I'd appreciate any information from any forum members about the types of adhesive Gibson has used on their acoustics since late-80's up to date. I'd like to know if heat-melting adhesive such as hide glue was used on these guitars, between the neck and fingerboard in particular. Thanks in advance for your input. The dovetail joint is done with hide glue and the fretboard to the neck and over the top is titebond. The symptoms you describe are usually caused by the top being severely dehydrated. This causes the top to drop or shrink and when it drops it pulls the end of the fretboard down with it. This is the cause of most neck resets. You might try re hydrating the top but it probably won't fix the entire problem.The truss rod only goes to the 14th fret so it won't help at all. Link to comment Share on other sites More sharing options...
iangibson Posted May 6, 2011 Author Share Posted May 6, 2011 . How are the guitars stored? What is the storage environment (location, temp, humidity), and how consistent is it? Thanks for the reply. I live in Japan where the summer is hot and highly humid. I hadn’t played these guitars for a long while. They were tuned down and kept in their own cases for over a year in a room which is located in the northeast corner in my apartment unit where the temperature does not rise so high, but I think the humidity level is consistent across the entire apartment. I took them out of the cases and put them on a stand a couple months ago because I wanted to start playing them again, but didn't get to just until the other day when I noticed this problem on the necks. The neck being bent like this is not unusual - at least not where I live. And the common treatment is what I mentioned above. Link to comment Share on other sites More sharing options...
iangibson Posted May 6, 2011 Author Share Posted May 6, 2011 The dovetail joint is done with hide glue and the fretboard to the neck and over the top is titebond. The symptoms you describe are usually caused by the top being severely dehydrated. This causes the top to drop or shrink and when it drops it pulls the end of the fretboard down with it. This is the cause of most neck resets. You might try re hydrating the top but it probably won't fix the entire problem.The truss rod only goes to the 14th fret so it won't help at all. Thanks for your reply. The body top is flat with no cave-in or swollen belly (below the bridge) both of which are common on an old acoustic guitar. This sounds to me like the portion of the fingerboard that’s on the body top is in a healthy state. And the neck/fingerboard above the body/neck joint area is bent upward (that is, upward towards the ceiling when the guitar is placed with its belly up). Is titebond heat-reactive? If not, how would one separate the fingerboard from the neck? Link to comment Share on other sites More sharing options...
Blaster Posted May 6, 2011 Share Posted May 6, 2011 Is it possible that the truss rods were tightened too much, or left that way during severe weather changes? From your description i sounds like the fretboard and necks have expanded or shrunk at different rates. I've heated necks before and softened the glue bond so the fretboards could reposition. It's a fairly straightforward process, but I had a tool especially made for it, which was an aluminum bar with an adjustable thermostat that was placed over the fretboard. I think LMI sells them. The guitars I used this tool on were National resonators from the early 1930s, so I don't know what type of glue they used, probably Hide Glue that could be heated. Link to comment Share on other sites More sharing options...
guitarstrummer Posted May 6, 2011 Share Posted May 6, 2011 Gibson acoustics should have a slight hump below the bridge. If it's flat, it's probably on the dry side. You can place a ruler on it's side edge immediately below the bridge. If the ruler touches the top on the side edges of the guitar top, it's too dry. Link to comment Share on other sites More sharing options...
iangibson Posted May 6, 2011 Author Share Posted May 6, 2011 Is it possible that the truss rods were tightened too much, or left that way during severe weather changes? From your description i sounds like the fretboard and necks have expanded or shrunk at different rates. I've heated necks before and softened the glue bond so the fretboards could reposition. It's a fairly straightforward process, but I had a tool especially made for it, which was an aluminum bar with an adjustable thermostat that was placed over the fretboard. Is the tool something like this? This is how most repair shops fix a neck that shows the symptom over here in Japan. I don't think the truss rods were tightened too much ever. The guitars just went from one dry winter to wet summer then to another dry winter. And now the weather is a lot warmer and here they are with the ****ed up necks Link to comment Share on other sites More sharing options...
iangibson Posted May 6, 2011 Author Share Posted May 6, 2011 Gibson acoustics should have a slight hump below the bridge. If it's flat, it's probably on the dry side. You can place a ruler on it's side edge immediately below the bridge. If the ruler touches the top on the side edges of the guitar top, it's too dry. I don't have a straight edge handy at the moment, but the tops do look to have a slight hump you refer to. I always thought that it was correct only when a flat top model had a complete flat top. Thanks for teaching me a new thing. Link to comment Share on other sites More sharing options...
iangibson Posted May 6, 2011 Author Share Posted May 6, 2011 Here's how the neck of the J-200 looks. Link to comment Share on other sites More sharing options...
iangibson Posted May 6, 2011 Author Share Posted May 6, 2011 And the neck of the J-180. Link to comment Share on other sites More sharing options...
Jeremy Morton Posted May 6, 2011 Share Posted May 6, 2011 I think a setup by a professional would likely help you out. Nothing really jumps out by how the neck looks. Maybe the truss rod is a bit too tight giving you back bow in the first position. A good setup would be a good start IMHO. Link to comment Share on other sites More sharing options...
BigKahune Posted May 6, 2011 Share Posted May 6, 2011 . The J-200 has something going on around 14 on the bass side (treble side doesn't look bad at all). It looks to me like the frets are fairly level but the binding might have been filed a bit to much around 14 on the bass side. I agree with Jeremy. Before you attempt anything, have a good shop/luthier give you an opinion. Link to comment Share on other sites More sharing options...
Blaster Posted May 6, 2011 Share Posted May 6, 2011 Is the tool something like this? This is how most repair shops fix a neck that shows the symptom over here in Japan. I don't think the truss rods were tightened too much ever. The guitars just went from one dry winter to wet summer then to another dry winter. And now the weather is a lot warmer and here they are with the ****ed up necks Yes, that looks exactly like the one I used, except the one I used had a thermostat gauge and control knob. Link to comment Share on other sites More sharing options...
Hogeye Posted May 6, 2011 Share Posted May 6, 2011 And the neck of the J-180. Neither guitar needs repair. Just a little set-up. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.