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

[Farrold]

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.

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.

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).

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

The pics:

[Ben M.]

I’m no professional guitar tech by any means, just a hobbyist but since no one else is responding I’ll give you my two cents.

I’ve only heat pressed a neck straight once. It had a forward bow. It worked but only lasted about a year and it was a banana again. I’ve read a lot about the process and the general consensus seems to be it’s a temporary fix. Wood has sort of a memory and will eventually return to it’s original state.

Since you have a back bow I would think the string tension would help keep it straight and maybe keep it from back bowing again. I don’t have any experience with this so I’m just assuming.

As for options 1&2 both would probably work. I don’t think either would necessarily be easier than the other.

Getting a fretboard off cleanly is a challenge.

Removing frets cleanly is too. You’d probably be better off replacing them rather than trying to get the old ones back in.

The best thing to do would be remove the fret board heat press the neck straight then route out a channel in the neck and install a carbon fiber rod to keep it straight.

Again I’m no professional so take this with a grain of salt.

Good luck!

[MC5C]

For me, shaving the neck, either the neck itself or the fretboard, is going to make the neck profile thinner in the shaved area, which I would find potentially unacceptable. You have no truss rod, so installing a dual action truss rod after taking the fretboard off and heat-pressing just the neck to straight would probably be possible, and would eliminate the problem. A little less invasive and "changy" would be installing a couple of carbon fiber stiffening rods under the fretboard. I guess I would start out slow, to be honest, and attempt a heat-press on the neck, dressing the frets, and installing medium gauge strings and see what happens, with the idea being maybe it will work and last (sometimes they do), maybe it will stabilize and reduce the bow to the point where plaing the fretboard is a minimally invasive procedure, and no harm no foul if you need to try something else in a year.

[Farrold]

Thanks a lot for the replies! I am increasingly inclined to the neck straightening and installing a carbon fiber rod (after I let it sit straightened and stringed up for a while as you suggested).

If I go for this, should I consider installing 2 rods instead of 1 centered? Or is 1 usually enough to keep a neck straight?

[Howard Klepper]

A straightedge is supposed to have a straight edge, but it is not supposed to have a straight broad surface--especially when supported only in the middle. So not much that is meaningful can be seen in your first photo. And in any case, what matters is what happens when it is strung and tuned to pitch. Have you done that yet?

[Farrold]

Originally Posted by Howard Klepper

A straightedge is supposed to have a straight edge, but it is not supposed to have a straight broad surface--especially when supported only in the middle. So not much that is meaningful can be seen in your first photo. And in any case, what matters is what happens when it is strung and tuned to pitch. Have you done that yet?

There is quite a lot that is meaningful to be seen in the first photo, since it shows exactly how significant the back bow is (after all, I wouldn't have included it if if weren't so, a 3 mm thick solid steel straight edge doesn't bend just like that and especially not when you're making sure that it does not – which is making this debate entirely pointless).The neck has been under string tension for the last 40 years, I think that is quite enough for it to make (or not to make) a difference.

At this point, I have decided (based on all the advice I got) to remove the fretboard, straighten the neck with heat, insert two carbon rods and a dual action truss rod. Hopefully all will go as planned and the guitar will get a second chance, we will see.

[Howard Klepper]

I believe you misunderstood me. But you have decided, so best wishes.