Vintage archtop guitar, neck backbow - the right way to go fixing it?

[Robert Dobra]

Hi, I've recently bought a beautiful 1930's jazz guitar that unfortunately has a bowed neck (no truss rod and a backbow, see attached picture). I've been getting into guitar repairs for some time and have fixed quite a few problems successfully, but I've never dealt with this before and I'll be grateful for any practical advice. The guitar had a set of strings under tension (probably 11 or 12) before I removed the neck, but the bow looked the same even under tension (the neck was partly dislodged, but it still held in position quite firmly).

I believe that I have three choices now:

1) Remove the fretboard, level the neck and reglue the fretboard. Is this a viable thing to do?

2) Remove the frets and level the fretboard itself (at least from 0 to 12th fret, doing the whole lenght would mean sanding off too much, the higher action at higher frets could be bearable I think) – seems like the easiest option to me, but it would involve leveling the binding too and removing/returning the position inlays. I would not like to do this, it feels like cheating and will probably be noticeable.

3) I've been thinking about getting a heat press (a friend could easily build it for me), but I heard that it does not lead to reliable results (even less so that the other options). Perhaps I could straighten it with heat only so that I can install the rod?

The guitar is worth it. Thanks a lot in advance!

The pics:

[Marshall Dixon]

That guitar looks in such good shape that I wonder if it wasn't played much because of that back bow being there from early on.

First thing to figure out is if the glue used on the neck is water soluble. Made in the 1930's there is a good chance that it's hide glue, but casein glue was popular and isn't water soluble.

Removing the fingerboard is going to be a challenge even if hide glue was used. Just recently tried this. I pulled the frets and applied heat but could get no moisture into the joint and ended up cutting the fretboard off so that only about 1/16" was left and moisture could penetrate and heat softened the glue.

Option #2 would leave the binding an uneven eyesore. And inlay work is my least favorite thing to do. You could remove the bindings and recut the channel but you'd be cutting into the neck material to replace.

The binding material is another issue. If it is the type of plasticized stuff (celluloid?) they used back then it may not take heat. Maybe it could be replaced with a modern equivalent.

Heating the neck to soften the glue and with gradually increasing clamping pressure over a period of day(s) to reshape the neck is something I've read about different times. It seems that this is a piece of recalcitrant wood and the fix might be undone in time, as the wood's memory asserts itself. But with a little luck this might cause the fingerboard joint to separate somewhere so you could get moisture in there (if HHG) and work it off with a hot palette knife.

I don't know how you'd get a truss rod into it without removing the fingerboard, though.

If all else fails, you could salvage the fretboard and headstock veneer, make a new neck and reapply them.

[Barry Daniels]

I like to take necks off guitars and do stuff with them. Whether the fretboard will come off easily or not depends on the state of the glue joint. An iron on the fretboard and a hot knife are your friends. If you can get the fretboard off cleanly, then all options are open. At that point, the neck will be fairly easy to straighten with or without heat. And then carbon fiber can be installed into the neck to stabilize the new orientation. A truss rod too, of course. If you want to see a thread where I did this kind of work to a Gibson J-45, let me know and I will add a link.

[Robert Dobra]

Thanks a lot for the replies! When I removed the dislodged neck, I found out somebody actually had removed the original varnish and had applied a new one (it originally looked exactly like this one - https://www.facebook.com/24118001255501 ... =3&theater - except for a different headstock veneer). The previous owner told me his grandfather played in a swing band, so I believe he might have had it remade because the original lacquer was not in a good condition anymore and then something happened to the neck joint). I'll do my best to save the original neck, we'll see.

I hope that I'll manage to remove the fretboard as cleanly as possible. Please do post the link, I'll be glad for any guidelines. If the fretboard comes off cleanly, is it viable to straighten the neck without heat by just clamping it to a straight surface (is it likely to stay that way long enough to allow for a carbon rod installation)? Also, should I consider inserting 2 rods right away, or is 1 centered rod usually enough to keep a neck straight (I found some articles where the author mentioned inserting multiple ones)?

[Barry Daniels]

Here is the link:viewtopic.php?f=8&t=5637&hilit=gibson+J+45

With the fingerboard off you should definitely install an adjustable truss rod. So if you install carbon you do a pair on either side of the truss rod.

[Paco Jimenez]

A bit OT, sorry.

In case you are wondering that guitar is a late '30s built in the former Czechoslovakia. In Schönbach to be precise (renamed as Luby after the WWII). It seems to be an Albo (ALred BOrst) No. 23. In the '37 catalog it's described as all solid woods and carved, but I've seen many variations of this and other models looking identical but being laminated and lacking the usual duraluminum neck reinforcent. Also the typical ebony fretboard was commonly replaced by a stained something else.

At first instance, all the hardware is original, which regarding tuners is not very good news. The higher-end models had very good tuners, the budget models use to have really crap machines instead.

Sunburst was the typical finishing (a la Gibson) but blonde finishing was common too.

[Robert Dobra]

I like to take necks off guitars and do stuff with them. Whether the fretboard will come off easily or not depends on the state of the glue joint. An iron on the fretboard and a hot knife are your friends. If you can get the fretboard off cleanly, then all options are open. At that point, the neck will be fairly easy to straighten with or without heat. And then carbon fiber can be installed into the neck to stabilize the new orientation. A truss rod too, of course. If you want to see a thread where I did this kind of work to a Gibson J-45, let me know and I will add a link.

Thank you! So its not really viable to install only a carbon rod or a couple of them (in case I wanted to preserve the looks of the guitar as much as possible while losing the possibility of adjusting the neck)? The heating blanket on the pics in your repair thread looks great, is it possible to purchase one somewhere / do you have to build it yourself?

A bit OT, sorry.

In case you are wondering that guitar is a late '30s built in the former Czechoslovakia. In Schönbach to be precise (renamed as Luby after the WWII). It seems to be an Albo (ALred BOrst) No. 23. In the '37 catalog it's described as all solid woods and carved, but I've seen many variations of this and other models looking identical but being laminated and lacking the usual duraluminum neck reinforcent. Also the typical ebony fretboard was commonly replaced by a stained something else.

At first instance, all the hardware is original, which regarding tuners is not very good news. The higher-end models had very good tuners, the budget models use to have really crap machines instead.

Sunburst was the typical finishing (a la Gibson) but blonde finishing was common too.

Thank you for the information! I was wondering, would you be willing to share the catalogue, or at least the particular page from it? This guitar has a laminated top for sure, I discovered that when I removed the neck, the fretboard and bridge do seem to be made from ebony though (I am no expert though, still learning). The tuners seem quite sturdy and nice, although someone hacked apart the one side, I'll try to find a proper replacement (I am located in Czech Republic and started collecting vintage guitars some time ago, so I tend to stumble upon Schonbach and Markneukirchen guitars – or sometimes what remains of them - quite often, we'll see).

I've attached some more pics, the bottom picture is another Borst guitar that a friend showed me yesterday - If I manage to repair the one I have, hopefully this one will be next

[Barry Daniels]

Holy cow that is a twisted neck. Similar to my J-45. That is going to be a challenge. Not using an adjustable truss rod is only going to make your job more difficult.

I rebuilt an early 30's martin and added 3 carbon fiber bars in lieu of an adjustable truss rod. It can be done, but I would only do when the original look is worth preserving for an historical/vintage instrument. Also, I would only do it if you can get the neck back into a very straight and stable condition.

You can get the fretboard sized heater here: https://www.lmii.com/bending-heating/25 ... watts.html

[Robert Dobra]

Holy cow that is a twisted neck. Similar to my J-45. That is going to be a challenge. Not using an adjustable truss rod is only going to make your job more difficult.

I rebuilt an early 30's martin and added 3 carbon fiber bars in lieu of an adjustable truss rod. It can be done, but I would only do when the original look is worth preserving for an historical/vintage instrument. Also, I would only do it if you can get the neck back into a very straight and stable condition.

You can get the fretboard sized heater here: https://www.lmii.com/bending-heating/25 ... watts.html

Thank you so much for all the information! I'm cleaning the neck joint now, soon I'll be gluing the neck back (as I believe this is the best method instead of working on the neck separately?) The heating blanket, carbon rods and a truss rod are on their way to me, as soon as I come back from holidays, I will start the next phase. And I'm really looking forward to it!

[Barry Daniels]

If a neck is already separated from the body, I usually do most of the work while it is off. Also, it is better to have a straight neck first so you can determine if any angle adjustment is necessary on the dovetail.