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I'm building an OM and want to use a non-adjustable neck with a single 1/4" X 3/8" carbon fiber central reinforcement rod.
Questions:
I'm planning on using West Systems epoxy to glue the rod in the neck channel and the .045 ebony cover strip/shim. Any cautions regarding the epoxy use?

I understand that relief is going to be non-adjustable. Back in the day of ebony reinforcement and the use of bar frets selective fret thickness has allowed some "adjustment" but since the days of "Tbar" and "Square Channel" along with "T-frets" is seems that proper geometry during neck/fingerboard/fretting seemed to be the rule….. Am I correct here and is there any "geometry" I should be particularly aware of??

Thanks for any advice.

Mike

My only concern regarding eliminating the adjustable truss rod is that wood is far from being a static material. The rod is sometimes needed to compensate for the inevitable movement of wood.

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Joe Beaver
Maker of Sawdust

At least use 1/2" tall. Should be about 2.4x the stiffness. If you have to, sand a little taper into it toward the nut end (but be careful of the dust). Or if you can afford it, these D tubes look good http://www.dragonplate.com/ecart/categories.asp?cID=130

From various past threads, it sounds like you'll need to use compression fretting to make it stable, which has a learning curve. So don't be too surprised if you have to pull the frets and try again.

Here's a thread with some info from Burton LeGeyt, who has a nifty method of making wood core D tubes (which is linked to from one of this posts in this thread): http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=43737

And here's a long AGF thread discussing non-adjustable necks: http://www.acousticguitarforum.com/forums/showthread.php?t=352157

I've built many banjos using only a CF bar for reinforcement without any problems. I run the rod all the way through the peghead to add some reinforcement there at what can be a weak spot. I use 1/2 X 1/8 inch bars.

For setting relief, I built a simple jig that pulls down on the peghead area and heel, and holds the center of the neck steady, creating a slight back bow. I use a dial indicator to get the amount of relief introduced that I want to introduce. I flatten the fingerboard with the neck in the jig, then I install frets and repeat the process for leveling the frets. When the tension is released, the desired relief is in place.

Banjos don't have nearly as much tension on them as guitars do, and the fingerboard is typically the length of the neck only with no extension, so things would be somewhat different on a guitar. But I've had very good luck using this method and something similar would undoubtedly work with guitar fingerboards.

Dave

+1 to what Joe said.

Truss rods are important and not using one these days will impact negatively the "serviceability" of the instrument in the future, possibly not to distant future too.

For example the decades of Martins without truss rods come refret time or in the event that something moves, and wood often does... the only way to reshape the fret plane requires creative leveling and compression fretting. We have all of the various sizes of fret wire for compression fretting (including bar frets...) being an authorized Martin service center but not every place that one may go for service will. It's expensive and not unlike being a hardware store where you have to stock stuff, and tie up your coin, for at times a decade or more.

I also can't tell you how often seasonal adjustments are required even to well cared for instruments where the presence of a truss rod makes this simple, quick, and easy. No truss rod and that seasonal adjustment may require an expensive fret dressing or worse.

There is also the issue of who's going to be the current steward of the instrument some day too. More specifically you may like mediums on an ax but someday it may be gifted to someone who likes lights. If you build the fret plane for mediums and it ends up with lights there may not be enough relief and even some back bow.

If you are considering a CF reinforcement a truss rod is no more difficult to accommodate and install. Just keep that excellent West Systems away from the truss rod especially the moving parts.

Serviceability is important and if anyone has creating something that will someday be a family heirloom in mind please be proactive and avoid making as Rick Turner once said on this very forum "GLOs" or "guitar like objects" that one day may be relegated to being a wall hanger because the thing became unplayable and was built unserviceable so it could not be easily repaired with out unnatural acts.

So to directly answer your last question - yeah you should be concerned about the fret plane geometry as well as neck angle geometry. Install a truss rod and you have the fret plane geometry covered.

Not high enough in my opinion.............should be at least .500". When I first started to build I used .250" by .500"steel bar stock as put forth by David R. Young. Worked but was quite heavy in the neck. That was before CF became common place. With the steel bar one had to build in some back bow to allow for pull up by the strings. I assume you will have to build in some with the CF. Be careful about having the frets to tight in the fret slots. Too tight and you put in too much back bow that will leave the frets at the center of the board standing high under string tension. With the steel bar I would allow about .020"back bow on both ends of the board. After fretting one would have .005" to .010" relief with some drop off at the end of the board............if you were lucky. The stiffness of the neck it's self came in play and one had to account for that. That's about all I can add. Hard to put a handle on it when one is doing it for the first time.
Tom

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A lot to think about…. Thanks Lads.
I don't intend the instrument for anyone but me. May try the experiment anyway. Worse that can happen is I learn a bunch and or end up having to make a new neck. Kinda like shavings and dust anyway so what the heck. Seems like there must be close to a million old non adjustable Martins out there that have served [or still serving] well, we'll see.

Mike

I have done quite a few non-adjustable reinforced necks, with CF, steel, or Texas Ebony reinforcement, and there is a learning curve to it. There is a lot more to it than just how much CF you put in the neck, it starts with the neck wood, and the steps in achieving a stable neck with a slight relief.
I would use at least 2, 1/8 x 1/2 bars, or 3, 1/8x3/8 bars.

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I don't see enough of them to know if this is true. All I know is that when ever I do see one come over my bench I know it is going to be extra work. And I find myself wishing they had a truss rod.

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Josh House

Canadian Luthier Supply
http://www.canadianluthiersupply.com
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House Guitars - Custom Built Acoustic Instruments.
http://www.houseguitars.com

Michael, I had a beautiful 1974 (big name guitar/model deleted) with a non-adjustable truss rod. Unfortunately, I live in the south with high humidity. The guitar would have been awesome if only I could have adjusted the truss rod 1/16".

The guitar is gone, but the memory of the lost 1/16" remains. Thx, Tony

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Tony Flippo

I like the idea of CF reinforcement and use 2 X 1/8 x 3/8 bars epoxied into parallel slots on either side of two way truss rod.
Have done one neck without truss rod. I think the truss rod could be eliminated but many players want the "notion" of adjustibility.

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Greg
http://garibaldiinstruments.com/

The thread that Dennis linked to from the AGF is a good read, it made me think about a few things differently.

Not much more for me to say than what I have already said in the linked threads-
If it is a guitar for yourself and that is what you want then by all means go for it! As others have said, use as tall a CF rod as you can if that is all you are using and do build a very slight bit of back bow into the nut end of the neck before stringing.

Good luck!

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Most of my 50 years of playing the guitar centered around open string folk style and bluegrass with the occasional excursion above the fifth fret. Capo if it was in a weird key. Relief was not all that critical as long as there was enough to prevent buzz. A lot of it was done on a 1975 D28 built like a tank with no rod. It is stable to this very day!

When I got into playing jazzy stuff using all closed chords and the whole neck I became amazed at how important even a few thousands of relief could be for optimal playability especially as I hit 70 and my hands are weaker and tendons and joints are talking back.

If someone had told me 10 tears ago that you could feel a .002 change in relief I would have laughed at them but it is true for me now.

For me at my current stage an adjustable rod is mandatory.

That AGF thread was great especially John Greven's posts. Thanks!! It really boils down to what works for you and your playing style doesn't it. I think it's great that folks are still interested in the skills needed to build a viable truss rod free neck. They are not insignificant.

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