National Resonator neck reset

I do a fair bit of neck resets in my shop. It’s a pretty common job, and just about every acoustic guitar needs a neck reset during it’s lifetime – the strings pull the neck forward, and eventually the neck/body joint needs to be re-carved to get the neck back to the proper angle. I feel like I’ve gotten pretty good at it over the years, but this past week I was presented with a unique challenge I’ve never faced before: doing a neck reset on a 1934 National Dobro. This resonator, affectionately named “Rusty” by it’s owner John Lisi (who is one hell of a slide player), was completely unplayable as a standard guitar. The action was really high: the neck angle was extremely underset, and the neck had a significant bow. John wanted an instrument that he could shred on, and Rusty just wasn’t cutting it. John’s only instructions were to “make it awesome”.

Rusty showed up with no strings, and mostly in pieces:

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I first had to string it up to see what I was dealing with. Even without strings the neck looked pretty bad, but with a set of 12s installed it was downright atrocious. Unfortunately it’s impossible to get a good photograph sighting down the neck, but let’s just say you could shoot arrows with this thing. Before I took the neck off, I took careful measurements, and I inspected the guts of the guitar to make sure there weren’t going to be any nasty surprises that I would have to deal with later on.

Resonator necks attach quite a bit differently than a standard acoustic guitar. Acoustics utilize a dovetail joint where the neck and body meet, which is pretty elegant; resonators screwed into a block at the neck joint, and are then stabilized by a long bar that presses against the back and tail. The neck angle is determined not only by the neck’s heel, but also by the bar’s position in relation to the back and top. I know this may not make much sense – bear with me here, and hopefully it will become clear.

Here’s the crossbar, with some round shims under it, pressing against the back:

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The crossbar against the top and tail block:

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And here’s the crossbar attaching to the neck, and the neck block that the fingerboard is screwed into:

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The first obstacle in removing the neck is the screws holding the fingerboard in place. They are hidden under five dots, which normally I would be inclined just to drill out and replace. But since this is a vintage piece, and it has ivory dots, I wasn’t about to just rip ’em out. I softened the hide glue that held the dots in place, and then gently pried them out with a razor blade:

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Once the dots are out, removing the neck is easy: unscrew the fingerboard and the crossbar, and then slide the whole thing out:

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This was going to be tricky: the neck didn’t have a truss rod, and it had way too much relief, plus the neck angle was grossly underset. I was going to have to straighten the neck, build in just the right amount of relief, all the while anticipating the proper neck angle. Measurements and calculations were only going to be helpful as guideposts, but exact results were going to gained largely through intuition. Good thing I’ve done lots of vintage pre-truss rod Martin neck resets before: I would need all that experience here to nail this thing.

Since the neck was so severely warped, I did a series of heat presses to get the neck to a reasonable degree of straightness. Getting it as straight as possible before refretting it would keep wood removal to a minimum while planing the fretboard.

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Once the neck was straight-ish, it was time to reshape the heel to kick the neck angle back. First I carved away the insides of the heel, so the edges would cup the round shoulders of the resonator body:

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Here’s where my measurements and intuition came in to play: I opted to take 2mm off the bottom edge of the heel. This would kick the neck angle back quite a bit, which would actually overset the neck ever so slightly. I did this for several   reasons: it would require a taller saddle, which would increase the break angle of the strings towards the tailpiece (making the strings more stable in the saddle); it would bring the strings closer to John’s hand under the cover, making it feel more like a standard guitar rather than a resonator;  it would increase the downward pressure into the cone, which could conceivably increase projection and volume; and it would extend the life of the low action, as the neck would eventually pull forward over the decades – all a player would have to do would be to lower the saddle as the neck moved.

I marked off a line 2mm back on the heel, made a matching sanding block, and carefully sanded away all the wood I wanted to remove.

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Once the neck heel was shaped, I reinstalled the neck and then set the cross bar back in place. Since the neck angle had been kicked back so much, the large shims where the bar pressed against the top and tail block were now way too large, and the shims at the back were now not large enough to reach the bar. I removed the top shims, and made a new block for the back so the bar was firmly in place, stabilizing the neck:

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As you can see, doing a resonator neck reset is more akin to carpentry rather than luthiery. Pretty fun stuff, methinks!

I tested my neck angle, which was pretty close to where I wanted it. I wouldn’t be completely sure that it was dead on until I refretted the neck (planing out a huge hump in the fingerboard and then building in the appropriate amount of relief), so I was slightly nervous about forging ahead – normally this would be easy to deal with, but without an adjustable truss rod, every step was fairly permanent. Fortunately, my intuition paid off! I absolutely NAILED the angle I was aiming for. Sweet!

I refretted it with stainless steel fretwire, made a new bone nut, a rosewood saddle, and installed a Lace Ultra Slim humbucker, and gave it a complete setup. What an amazing transformation this was: from completely unplayable to a blues shred machine! The final action came down to 1.5mm at the 12th fret, which is right where John usually likes it. Every note plays clean, and this thing really roars! Rad!

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John Lisi and his band, Deltafunk, are scheduled to play Jazzfest this year, and I hope to see ol’ Rusty here hitting the stage with him.

 

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