Ken Parker Installs Carbon Fiber D-Tube Neck Stiffener

Ken Parker installs the Carbon Fiber D-Tube Neck Beam in an Archtop Guitar

Ken Parker
Ken Parker

This project began with our local jazz guitar genius, Peter Fedele, and his wonderful 1953 Epiphone Archtop guitar. The top is laminated spruce, and the rail braces (see scary photos!) are poplar. This old archtop has a cool vibe, and a nice history, having been used extensively by Duke Robillard for recording and live performance. It really sounded great, and there were no problems with it except for a terrible built - in shortcoming! Because the fret slots were sloppily cut, and out of position, (some frets even were crooked!), there was no way for the guitar to play in tune in any position on the neck. Peter loved the vibe and provenance of the instrument, and made it sound delicious, but was exhausted and discouraged with trying to play in tune.

Over the years, various repairmen tried every trick in the book to improve the intonation, including installing a tunable, adjustable nut (!) , adding a Gibson style 6 way intonable bridge top, and even screwing the bridge base to the top!

The only real fix was a new fingerboard with correctly placed fret slots.

Because of the large, three part pearl and abalone inlays and the many plastic binding and purfling stripes in this particular fingerboard it looked like a daunting project to a guy like me who does neither of those things in his own work.

Fortunately my friend Brian Galloup at Galloup Guitars encouraged me to let them help with the project! I mailed him the guitar so they could take accurate measurements and see what they could do about making a faithful replica with correct fret slot positioning.

Their capable young team went to work, and It wasn't long before I had a lovely rosewood fingerboard with perfectly executed mother-of-pearl and abalone inlays as well as the goofy original style plastic binding, ready for side dots and frets!

The young geniuses at Galloup decided to faithfully misposition the inlays to match the original fingerboard. Color me thrilled!! Funky old vibe retained!!

When all was back at my workshop, I removed the fretboard with the aid of an old iron and an old-fashioned wedge-shaped table knife. One issue complicating the removal of the fretboard was the odd placement of the unique truss rod in this guitar, right underneath, and even within the fingerboard!

Before I describe the rest of the rod's miserable features, the innovative feature of this rod was a nicely hot forged 5/32" allen socket for turning the useless rod. Credit where credit is due.

At Epiphone, the "engineers" had decided to place the rod above the neutral plane of the neck instead of below it, so the rod was set partly in the neck material, and partly in the fingerboard. It adjusted at the body end of the fingerboard, just above the top. The idea was to push apart the wood fibers, and thereby lengthen the fingerboard side of the neck, instead of compressing the wood fibers on the back of the neck, as most other truss rods are designed to do. The truss rod itself was turned to perform an "adjustment", and thereby forced apart two small blocks of steel, a threaded one set below the 12th fret, and a dead stop block set below the first fret.

You can see in the photographs that the rotating 1/4" 28 tpi rod was supposed to be restrained and damped by four rubber pads (1/8" slices of pencil eraser) designed to keep it quiet. Seriously. No, really, that's what they are. I wonder what they used when they needed to erase something??

You guessed it, this arrangement turned out to be a total failure. Those of us who have worked on Epiphone guitars so equipped over the years know that there isn't much that can be expected from these odd truss rods, except for infuriating resonances and rattles. I have seen examples where the fingerboard had been blown off the neck due to overzealous "adjusting" behavior. The .060" layer of sliced soft maple veneer that was bonded between the neck and the fingerboard seemed to be part of this problem. Yikes!!

There's no practical way to retrofit a proper adjustable rod to these instruments. I opted to install a Gemini 3/4" Tapered D Tube, designed and built by the team at Allred Associates to replace the original disastrous steel contraption. The D Tube is an innovative musical instrument neck reinforcing structure made from Carbon Fiber and high strength Epoxy Resin.

The D Tube is a great engineering solution, giving lots of stiffness in both bending and torsion. In this application, the rod helped to reinforce and stiffen the neck/body joint, further improving the response of the structure. The tube itself sounds lively and clear when dropped on the bench, and I know it will breathe new life into this guitar by stiffening and thereby brightening and focusing the sound of this neck. Another benefit is a substantial reduction in weight, which helped the balance of this instrument substantially. The original truss rod weighed in at a mighty 108 g whereas the D Tube that replaced it weighed 64 g. Also, the extra wood we removed weighed more than the tube, so the neck lost quite a bit of weight as it gained lots of stiffness. We made a 8/4" poplar guitar nest you see in the photos, and cut the tapered, half-round slot on a Bridgeport Mill. Next, we bonded the tapered D tube to the 5 piece laminated maple and walnut neck with 105/205 West System Epoxy, positioning the top of the tube about .020" below the fretboard gluing surface.

A nice fret job with beautiful gold colored EVO fret wire, and Pete is happily playing his guitar again. One thing he doesn't miss is the crazymaking odd reverberations of the original truss rod!!

We are all very pleased with how much better the instrument sounds! it has new clarity and punch, and really put an already great sounding guitar over-the-top.

This turned out to be a wonderful way to heal a stylin' old instrument that showed up with a noisy neck and misplaced frets.

Thanks to all the team members for your good work!

Comment from Peter Fedele (guitar owner)
"The D-tube is amazing! I was hoping it would stabilize and rectify the neck issues I was experiencing with my 1953 Epiphone Zephyr Regent Deluxe, but I didn't realize it would improve the tone quality. With the installation of the D-tube, the tone, definition and resonance has greatly improved. This innovative idea has brought my instrument to another level!"

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Allred and Associates, Inc.
321 Route 5 West, PO Box 321
Elbridge, New York 13060
p: 315.252.2559   f: 315.252.0502