Contemporary Guitars without Truss Rods

[jackaroo]

Ugh! Neck sets are caused by body deformation... Nothing to do with necks.

Please folks...Martin guitars do have truss rods, they just aren't adjustable. Big difference..

Nice debate though.

[mot]

Originally Posted by Kent Chasson

Is there an advantage to building without an adjustable rod that can't be achieved using an adjustable one? If not, why do it?

Originally Posted by rogthefrog

Forgive me, but I'm still trying to understand why you would *not* want an adjustable truss rod. "My guitars don't need one" seems inadequate as an argument. All of mine have benefited from an adjustable truss rod. So is there a structural or tonal reason to forgo such a useful piece of engineering?

Yes.

There are at least two advantages that I can think of and why I just ordered my latest guitar without a truss rod. All my other guitars have truss rods. I should add that the guitar I ordered is carbon fiber though, so some of the issues I have seen in wood guitars aren't likely to be seen in this one.

1) Weight - A light guitar makes a difference after a few hours of playing.
2) Hollow neck - Can't easily do this with a truss rod stuck in the middle. Changes the sound in ways you just wouldn't expect when there is a sound port on the head too.

[SongwriterFan]

Originally Posted by kydave

In the case of building a rigid non-adjustable neck you are making an inherently stiff neck with negligible flex in the tension range of various guitar strings; i.e., the relief does not meaningfully change regardless of string gauge.

My 1937 D-18 Authentic plays without buzz using 13's.

Put 12's on there, and it buzzes.

If it had an adjustable truss rod, I could easily fix that without having to take out a glued-in saddle and replace it and/or work on the frets.

[jgreven]

Let’s talk about necksets, one of my favs...

All of the posts so far are partially correct and partially incorrect. There are three issues that come up for repair regarding necks; neck bow, neck angle to the body, and body compression.

Bowed or scoped necks mean it has bent (usually upward) under string tension or because it might have been a less than stellar piece of neck stock.

Correct neck angle (or set) means the neck attached to the box at an angle that makes for comfy action up the neck and that the string pull is directed into the box structure at or below the level of the top for greatest strength.

Body compression occurs mostly in older guitars that have been under full tension for a long time (remember wood is plastic, after all) and involves the stretching of the sides and to some degree the back plates while the top is compressing downward ahead of the soundhole. I have seen any number of old guitars that have a visible dip on either side of the neck as much as 1/8th to 3/16th inch. Looking at them from the back side does not show much deformation, but it is obvious looking at the top. (This is often accompanies by the dreaded fingerboard top cracks that the tongue brace is there to help prevent.)

So.... as a repairman, one can be presented with any and all of the above in a particular guitar.

Body compression is not fixable but the bad neck angle it causes is a simple neck reset. A bowed neck is just that and will not be “fixed” with a neck reset, but it might help. A bad neck set is fixed by a simple neck reset.

Most guitars have either a bad set or a bowed neck or a combination of the two issues. I can tell what is going on by simple sighting down the neck from the body end using the top as a reference plane. Often high action is just a matter of the neck not being flat and the set if fine. I fix the bow and all is good.

More often, it is a set problem and that is most obvious sighting down the neck from the nut end. The neck is flat but the tongue is pointing up and the rest of the fingerboard is pointing well below the bridge or saddle or into the soundhole. Popping the neck and putting it back in at the correct angle brings the entire fingerboard back to one plane and the action to a comfort level.

Honestly, it is still a bit of a mystery why neck set angles change over time when there is little body compression and the set angle was correct when the instrument was made. I suspect that the entire shank of the neck rotates slightly at the transition to the heel area as a result of the plasticity of mahogany under tension over time. Don’t know for sure, but it happens over and over and makes me suspicious.

Most of the resets I have done were on Martins before the advent of arching tops now in vogue. The earlier nearly flat tops had accompanying neck sets that were nearly flat to the top so the tongue was level with the rest of the board. But it doesn’t take much time before the pull of mediums with the old standard heavy factory string setup caused said rotation and the guitar needed a neck reset. The necks were straight but the set was now wrong. With a reset and other action adjustments, the playability could be brought back to comfortable.

A bowed neck is a separate issue from the set and gets dealt with a such. Truss rods make this SO easy. Non-adjustable necks require heat treatment, compression fretting and other mechanical processes to correct. Once the neck is straight, then the set can be addressed.

All older guitars made with minimally arched tops (they are called “flat tops” for a reason) will show differing degrees of box distortion over time and that also has to be taken into account during the neck reset operation. I refer to it as correcting for drift. It calls for a best guess as to how the set needs to accommodate the geometry for the distortion in the box. This distortion can be the CAUSE of the set being off, but usually it is only a contributing factor.

My old all original 1935 Gibson L-00 has top distortion bordering on a catastrophe waiting to happen, but I did a re-set using my best guess estimation and it now plays like butter and has remained totally stable ever since. (You should play this thing, it will make you cry it is SO good.)

Most instruments only need one correction of the set, but I have done repeated re-sets as often as three times over a many year period on a very few guitars. Why was it needed? I think there was more elasticity on the box structure than in most guitars, or perhaps the necks themselves were softer. Not sure, but it has happened. Not the norm, however.

The advent of the highly arched top designs now in common use virtually eliminates the need for re-sets. The arching provides a very strong neck angle to begin with and the arching itself stiffens the entire box structure exponentially reducing any tendency to distort. All good structural advances. Tonally, however, I take major issue with top arching as a killer of the lovely woody bass notes, but that is another issue altogether....
John

ps.
If you have any further questions, write them on the back of a $100 bill and send them out to me.

[Larry Pattis]

Originally Posted by jgreven

<<snip good info, of course>>

ps.
If you have any further questions, write them on the back of a $100 bill and send them out to me.

If I "borrow" this line, John, will I owe you mechanical royalties...?