Build Thread: Todd Rose Allegheny with adjustable neck

[Todd Rose]

Now it's epoxied into the groove in the neck block. The back is not glued on yet, but that's how it will fit together. The top of this piece will soon be sanded flush with the main part of the neck block, as the whole top of the rim is final sanded in the 28' radius dish in preparation for gluing on the top. But what is that big hole for?

[Todd Rose]

Hmmm... another big hole in the tail block. What's going on here?

[MBE]

It's really great to see this kind of detail narrated by the luthier. Helps the lay people like myself understand the intricacies of the work that you put into your instruments. Really enjoyable to watch. And it's coming together beautifully! Can't wait to see what the final shots look like.

[Todd Rose]

Thanks, MBE! I appreciate your interest.

[Burton LeGeyt]

Hmmm... another big hole in the tail block. What's going on here?

I feel like I should know but I don't!!
I'm looking forward to finding out though-

[Todd Rose]

Things are really beginning to take shape now, as I'm getting ready to glue on the plates, and now you see what those big holes were for: The Axial Strut. Fancy sounding name, but what else am I going to call it?

[Todd Rose]

The top is not glued on yet. I just have the rim sitting on there to check the fit before gluing on the back.

The axial strut will keep the box, especially the neck block and upper bout area, from distorting under string tension. Depending on string gauges used, the strings put roughly 170 pounds of tension on a guitar. An internal support like this is one way to save guitars from problems that develop as string tension takes its toll over time, but it is especially called for on a guitar like this with the kind of neck joint this will have, with a floating fretboard extension. If you're not sure what I mean, that will become clearer from the photos I'll post in later stages of construction.

[Todd Rose]

The strut is made of carbon fiber wrapped around a hardwood core. J.B. Allred custom made this for me. Here you can see the clearance between the strut and the X brace intersection.

J.B. Allred's company:
http://geminimusical.com/carbon-fibe...forcements.asp

[Todd Rose]

There's less clearance, but still plenty, between the strut and the upper brace.

[D.Kwasnycia]

Todd, Interesting build, looks great!

[lpa53]

What's your take on how the strut affects tone?

[Todd Rose]

Originally Posted by D.Kwasnycia

Todd, Interesting build, looks great!

Thanks, Dennis!

[Todd Rose]

Originally Posted by lpa53

What's your take on how the strut affects tone?

Not an easy question to answer, for several reasons. For one thing, this is the first guitar I've built this way, although I see this as a variation on what I've done before (see pic below), and similar things have been done in the past, notably by the Larson Brothers, with a single rod (they used steel) positioned axially like this one.

The short answer is this: I expect any effect the strut directly has on tone to be subtle, not dramatic. Being part of the rim, it has little direct effect on the most acoustically active parts of the guitar. Not to say that it has no effect -- and we could make conjectures based on how it's likely to affect certain modes of vibration of the instrument -- but predicting or analyzing the precise effect the strut itself has would be nearly impossible, because it is part of a whole system which has so many variables and is incredibly complex. In the case of my guitars, it is integral to the whole design, interconnected with all the other things (floating fretboard extension, very light bracing of the upper bout area of the soundboard, etc) that make my instruments different.

Though this is the first guitar I've built with an axial strut, rather than with struts like you see below, I see it as being very consistent with the way I design and build guitars, so I expect this guitar to sound like one of my guitars, which is to say, awesome. Seriously, though, the feedback I get from players affirms my own perceptions of the sound that results from the way I put guitars together: rich, powerful, responsive, and well balanced; a well-defined bass, very colorful midrange, and clear, singing highs; wide dynamic range; great projection (but also, with help from the side sound port, giving the player great sound, too); and my favorite quality -- a really full, muscular tone when playing single notes, especially noticeable in the trebles when playing melodies or leads up the neck.

I hope I don't sound like I'm bragging. I'm really just trying to give you the most useful answer to your question that I can offer.

[JonBarclay]

I remember seeing a Gwaltney guitar built with a similar arrangement to your (older) model above... Looks cool, a very engineered organic construction! Always assumed it would make for a super-stiff rim, really giving the vibrating plates a stable base?

Jon B

[Todd Rose]

Originally Posted by JonBarclay

I remember seeing a Gwaltney guitar built with a similar arrangement to your (older) model above... Looks cool, a very engineered organic construction! Always assumed it would make for a super-stiff rim, really giving the vibrating plates a stable base?

Jon B

In my mind, the jury is still out on the super-stiff rim concept. You'll notice that I'm now using ordinary kerfed linings (I have used much stiffer linings in the past). On the other hand, I have what I might call an "intuitive theory" about stiffening the guitar in certain specific ways, to improve what I think of as "strength of tone". It's not easy to articulate... it has to do with thinking of the force of string tension, and the strategy to design the instrument to appropriately resist that force, as a tonal ally rather than an enemy. Can you get a sense of what I mean? I need to work on explaining this better...