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robbo25

B45 12 string

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Hi

 

I'm retired and an amateur guitar maker. So here is my next project. I got this guitar from ebay at £170. The serial number puts it at 1963. It is as you see in the photos attached (no top, fingerboard chopped off at fret 12 and also lifting, probably as a result of an abortive attempt to remove the rest of it) with a couple of extra difficulties, which I will describe:

 

No adjustable saddle for the bridge (I believe this guitar was made in 3 conformations: adjustable saddle, pin bridge; fixed saddle, pin bridge; bridge plus tailpiece); several back braces loose; several cracks in the back (possibly with amateur repair attempts); top block detached from back of guitar; some bowing in of sides around the neck/top block area. On the plus side, the seller has sourced and included the necessary bindings and bracings from StewMac (these alone would cost about £50). A very exciting and extensive project. I've taken the first step by buying a torrified spruce top (£70), recommended by someone on a guitar makers' forum I'm a member of.

 

I do have some Gibson specific questions which I hope members will wade in and help with. Given the extent of the repairs necessary, I'm presuming this guitar isn't collectable, but I would like to retain as much of the original fabric as possible. With that in mind, should I keep it as an adjustable saddle, pin bridge configuration, or do you all have any thoughts about the comparative merits of fixed saddle, pin bridge and bridge plus tailpiece? Second, the scratch plate is long gone. Were any B45 12s made without a scratchplate (I'm guessing not), and if not, does anyone know of a source of replacements? Finally, the fingerboard is rosewood (although someone has painted over it rather crudely in black!), and since the spec for B45 12s fingerboards of this era is Brazilian, I would naturally like to preserve it. The cleanup and likely refret doesn't disturb me (although the f'board itself is very thin), but does anyone have experience of re-fixing a fingerboard which has been cut in this way (I have both the pieces...).

 

Sorry for the long post, but thanks in advance for any help, thoughts or just good luck wishes you may have.

 

Cheers

 

Rob

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I really commend you for taking on this project. As you rightly point out, the guitar does not have any real collectible value, but you may well be able to turn it into a nice mid-60's 12-string, and learn a lot in the process.

 

Not sure on the dating, but the serial number should be reasonably reliable if you don't mind sharing it. Also not sure when they went to the two-piece diamond MOTS (mother of toilet seat) headstock inlay on the Gibson 12's. I had a 1968 ES 335-12 with the same headstock configuration, including the MOTS inlay.

 

If that bridge is original, it is obviously meant for an adjustable saddle. String wear around the pin holes looks fairly normal. One question would be whether or not to retain the adjustable saddle. I might be tempted to, since the high string tension may make it difficult to get the neck angle absolutely correct during the neck re-set the guitar is going to require. The adjustable saddle gives you a little latitude in the neck angle.

 

New adjustable saddles are readily available, and if you can't find an adjusting mechanism from this period, I may be able to help you out with the bits and pieces.

 

You can see what appear to be wedges in the neck joint on either side of the dovetail, probably to try to correct for the fact the it looks like the neckblock has broken free from the rims and been pulled back into the guitar by string tension. The neck block is probably going to have to come out and the body geometry in plan view around the neck block corrected after the neck is removed.

 

As far as saving the fretboard, assuming you have both pieces, that's a more complicated question. The break in the board is over the neck heel, which is a fairly strong portion of the neck. Normally, the fretboard adds stiffness to the neck, and you will lose a bit of that because of the discontinuity caused by the two-piece board. At the same time, that discontinuity occurs at a fret slot, so the addition to stiffness is not necessarily as great as it first appears. Some of the stiffness should be re-gained by compression fretting when you re-fret.

 

You will also lose some board thickness when you plane down the board to get rid most of the divots after removing the frets, which reduces the total thickness (and therefore stiffness) of the neck. What you might consider is planning the existing fretboard to the thickness required by the divots, then laminating that to a thin piece of EIR or other available rosewood to build it up to the original thickness. Done properly, that glue line will be virtually invisible, and you will re-gain any stiffness lost by the discontinuous fretboard and its previous reduction in fretboard thickness.

 

You may want to consider going with an oversize bridge plate, while still making it of 3mm (1/8') maple.

 

I note that at least some of the top bracing is scalloped. Can't tell about the x-brace from the photo. The top bracing in 1963 would not have been scalloped. These were originally braced pretty much like their six-string siblings, but they were carrying some 50% more string tension. There is a fundamental question of whether the original top bracing or its modern equivalent would be up to snuff. If you go with lighter strings, and tune down a half step or full step, you may be OK.

 

These were great 12-strings sonically, but not so great structurally. Back when these were made (about the time I started playing), we tended to put heavier strings on all our guitars in an attempt to get more volume out of them. I always used medium or even heavy strings on my 1948/'50 J-45 (which I still have, by the way) to try to hold my own with the D-18's and D-28's I envied, which seem very loud compared to my Gibson. That massive additional string tension could be death on a 12-string if it is not designed for that extra tension.These particular early B-45 12 guitars are notorious for structural failure in compression due to string tension. The result was often the top collapsing inward after the top braces loosened.

 

Keep us posted. This is the type of project that is beyond most of us here, including me. Be sure to document the process.

 

To clarify, I am not even an amateur guitar builder, but I do have a practical engineering background, and am experienced in building much larger structures (racing yachts) where light weight and stiffness are critical. The principles are pretty much the same: analyze the loads, and figure out how to counteract them with the least amount of materials and structure you can get away with.

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J45Nick and Bassetman

 

Thanks for your support. Nick, I am conflicted about adjustable saddles generally, as, in theory, they should lead to bad transmission from the strings to the top because a) there are only two small points of contact between saddle and top (the adjustment screw bearing points) and B) there is no opportunity for the whole bridge to transmit vibrations, as there is with a well-fitting fixed position saddle. On the other hand, in practice I had two guitars in the past with adjustable saddle and they both had great sound. I should have mentioned that, as I am left handed and intend to repair this guitar for left hand playing, I would be making any bridge from scratch, including an adjustable one. A few lefties were made of this model, I believe. As to the wedges, they look like the result of a reset which chewed up the dovetail. There have been further wedges stuck to the outside of the block, but these are just hanging on.

 

Finally, I think you are right on the money with the fingerboard. A very thinly planed EIR board beneath the original sounds a great way to go. Good call on the top bracing. Apparently the early slope shoulder B45s (1961) had scalloped bracing, but probabably not the square shoulder ones, which also had extra braces running parallel to the X braces. Also the braces supplied have very extreme scallops. I'll probably save them for another project and go with either less pronounced scallops or some sort of parabolic bracing.

 

Thanks for the input

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Just a passing thought about the adj bridge - I am a fan of them, some aren't, and both views have merit. On a B45-12, considering the sound that's likely to pour out of it (a good one is a real beast - ROAR! - I doubt that you'd notice a great amount of subtle nuance either way.

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Just a passing thought about the adj bridge - I am a fan of them, some aren't, and both views have merit. On a B45-12, considering the sound that's likely to pour out of it (a good one is a real beast - ROAR! - I doubt that you'd notice a great amount of subtle nuance either way.

 

My thoughts exactly. Volume and sound transmission are not likely to be a problem with this guitar.

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Interesting. So that just leaves the problem of bridge lifting. However, I have also read several accounts of tailpieces being ripped out. Food for thought.

 

 

The pin bridge for this guitar has maybe 40% more gluing surface than the analogous 6-string bridge. Properly braced, with a new, tightly-fitting slightly oversized bridge plate, and properly glued, the bridge should stay put. It also depends very much on keeping string tension low by the use of light-gauge strings, tuned down at lest a half step.

 

This is pretty standard procedure for an acoustic 12, except maybe the Guilds from the same period, which were built like tanks. There's a reason they were so popular. Some later 12's went to 12-fret necks, maybe in part to create a shorter neck lever and a better-supported column.

Edited by j45nick

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Good luck and please keep us posted. A completed effort such as that will be noteworthy for certain ,,,,,,, and feel plain good also!

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The rounded edges of the split triangle on the headstock alone would have told you the guitar was built prior to 1965. The 1963 & 1964 B45-12 while not valuable are considered the best of the square shoulder 12 strings. This is because they had the same top bracing as Gibson six strings. While this was great for sound it was not the best thing for survival and these guitars could literally twist themselves apart. To solve the problem in late 1964 Gibson seriously beefed up the top bracing. As yours has no top I guess it does not matter as you can use any bracing you like.

 

With regard to the pickguard, the B45-12 came with the same large pointy pickguard Gibson began putting on all their guitars in 1955. Regarding bridges, Gibson used both the belly up fixed pin bridge and the tailpiece in 1963. I owned a very early '63 that had the tailpiece. There is a thought that the tailpiece setup was preferable for a lightly braced 12 string. Mine did have an ADJ saddle. I have never seen any bridge configuration on a B45-12 that did not have the ADJ saddle.

Edited by zombywoof

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Hi Zombywoof and thanks for that impressive info. I certainly wouldn't have known the date from the headstock detail, and it is nice to know that it is 'right'. The bracing sounds rather frightening and I'm not surprised so many caved in. Must have sounded wonderful though. In terms of what I do, I think it is important to strike a balance. For example, I've seen an extensive youtube clip of a repairman (English, actually, so I'll be on at him) retopping a B45 12 with extra braces running alongside the lower bout parts of the x braces & not much scalloping. I'm sure it'll hold together, but it looks like a sound killer. I'm going to try and find out where he got his info to make that bracing pattern, but I can't see going down that route would be right.

 

About the bridges, I have seen both pin and tailpiece bridges with non-adjustable saddles on auctions sites since I got mine, but most of them were later '60s and '70s. Of course they could also be retro fits. Also, a lot seem to have the belly at the back, like Martin do. Maybe they aren't right or this was a later approach? Regarding pickguards, I found Fox guitars who specialise in retro pickguard copies. $60 ish seems like a lot, but if all goes well, it will be worth it.

 

Incidentally, I am sure you are right on the money with the 'less stress' suggestion regarding tailpieces. With a tailpiece, all the force is downwards onto the bridge, whereas with a pin bridge there is torque back and forth on the bridge, resulting in the twisting you note. Thanks again for your help.

 

Cheers

 

Rob

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Regarding pickguards, I found Fox guitars who specialise in retro pickguard copies. $60 ish seems like a lot, but if all goes well, it will be worth it.

 

 

 

Try these guys:

 

terrapin

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Regarding pickguards, I found Fox guitars who specialise in retro pickguard copies. $60 ish seems like a lot, but if all goes well, it will be worth it.

 

 

I personally would not go with Paul Fox when it comes to pickguards. J45nick's Terrapin recommendation is good. They made a scratchplate for my mid-1950s Epi FT-79.

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Ok. A friend of mine recommended Paul Fox to me, but actually, when I contacted him he came back saying he couldn't do what I wanted, which was a bit of a surprise. I haven't got on to terrapin yet, but looking at their site they look like they will basically do more than Fox at a much better price.

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Hi Zombywoof and thanks for that impressive info. I certainly wouldn't have known the date from the headstock detail, and it is nice to know that it is 'right'. The bracing sounds rather frightening and I'm not surprised so many caved in. Must have sounded wonderful though. In terms of what I do, I think it is important to strike a balance. For example, I've seen an extensive youtube clip of a repairman (English, actually, so I'll be on at him) retopping a B45 12 with extra braces running alongside the lower bout parts of the x braces & not much scalloping. I'm sure it'll hold together, but it looks like a sound killer. I'm going to try and find out where he got his info to make that bracing pattern, but I can't see going down that route would be right.

 

 

Adding the second brace running alongside the X is exactly what Gibson started doing. I own a pre-War Regal 12 string. No neck reinforcement but the way they dealt with it was to slap a massive three piece neck on for stiffness and use a double X brace. Shades of Norlin Gibson. Carl Hozapfel who ran a shop in Baltimore and who, as far as I know, was the first American luthier to build 12 guitars used ladder bracing on his although his six strings were X braced.

Edited by zombywoof

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Paul Fox, of course, did give us a really great book on Gibson off-brands. Unfortunately his expert knowledge of guitars did not translate into guitar building skills.

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Hi Zombywoof. That's what I thought about the bracing in that video. I probably won't bother to contact those guys now. I don't want to end up repeating the exact tactic Gibson used if that led to a diminution in responsiveness. I'm thinking regular 6 string bracing but un-scalloped. I looked at an old book I have by David Russell Young in which he adds a transverse brace crosslapped into the lower bouts of both the x braces. Unfortunately, his guitars were well known for being quite overbuilt.

 

Anyone know of a good source of 12 string bracing information?

 

Cheers

 

Rob

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I'm about to start work on this project. First stage will be refixing loose back braces. Second will be determining neck angle. Essentially, the heel block has come away from the back of the guitar and is flapping around! The neck is completely tightly attached to the ribs. I propose to make a dummy top of the proposed thickness (I'm looking a 0.5mm thicker than a 6 string)and then shim the block with shims till the fingerboard is at appropriate angle to give the correct height,above the bridge/saddle (will use the current bridge and a dummy saddle to determine this. The construct a single mahogany shim of the apporoiate size and profile to go between the block and the back. I will then construct the actual top and brace it. I propose to brace more or less as a 6 string with 5/15 wide bracing non-calloped, but possibly parabolic. Basically, I aming to get as close to the 1963 confifuration (this is '63 instrument) withouth having the thing collapse. To this end I envisage using a non-pin bridge wih tailpiece (although I am still scavenging fo views on the comparative merits of the different bridge configuration types.

 

Does anyone have any comments on my proposed approach establishing the correct neck geometry and to bracing, and/or further advice?

 

Thanks, all

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