Official Luthiers Forum!

Re: Best/Worst Practices...Monkey See Monkey Do.....

Yes! It always frustrates me when people cite old guitars with poor upper bout structure as proof that all steel strings will eventually need a reset. Here are my thoughts on the matter...

To minimize the chances of needing a reset, you want the rigidity of the box to decrease gradually as you move away from the neck joint. Every degree of angular bending at the neck joint will make a large difference in action, necessitating a large drop in string height at the bridge to correct it. Every degree of angular bending at the soundhole makes a medium difference in action. Every degree of bending below the waist makes a small difference in action. So you want to encourage any cold creep to happen as far south as possible.

Firstly, there should be a lot of continuous stiffness between the neck and upper transverse brace... no gaps or unglued butt joints. 3 good styles I know of:
1. A-frame, notched into the headblock and UTB, and optionally continuing further south as soundhole braces as well.
2. Glued butt joint between the headblock extension and UTB. Hide glue can make a pretty strong endgrain joint if you size it first (thin coat of hide glue to plug the endgrain so it won't starve the joint when you glue it for real).
3. Buttresses, such as carbon fiber rods connecting the top of the headblock to the waist area of the back.

Secondly, don't carve down the ends of the UTB very much (exception: If using buttresses and an elevated fingerboard extension, then you actually can loosen up the upper bout and get it vibrating). When using a headblock extension or A-frame, more stress is concentrated on the UTB, so it needs to be beefed up compared to vintage Martin style. The fingerboard extension pretty much prevents the upper bout from being tonally active anyway, so make it good and solid. Make it both tall and fat, because it's also resisting the longitudinal compression force of the neck, which is pushing into the side of the UTB. Mine is wedge shaped, 1/2" wide at the base and 3/4" tall.

Thirdly, don't carve down the upper legs of the X too much (but do carve them more than the UTB, because they do affect the sound).

Fourthly, unless the soundboard is relatively thick and the upper legs of the X notch into the linings fairly close to the UTB, the soundhole should have some pretty strong braces beside it. Cutting a hole in the plate creates a major weak point, right where the string tension is trying to fold it up. This is also in the active vibrating area though, so like the upper X legs, there's a balance between strength and tone.

Excellent thoughts.

One way to help get solid continuity between the headlock extension/fretboard support and the top brace is to leave a small gap when gluing the top and then wedge in/glue a piece of wood after the box is closed or if you glue the top first after the top is on. I learned that from looking at some Bourgeois guitar construction pictures. It helps.

Support is especially important with a double tenon bolt-on neck as there is no stabilization from the glued fretboard extension.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Yes! It always frustrates me when people cite old guitars with poor upper bout structure as proof that all steel strings will eventually need a reset. Here are my thoughts on the matter...

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To stir things up a bit. All guitars that need resets do not of necessity have poor upper bout structure in the top. Given that rotation of the neck block happens to cause a need for reset and the pivot point of rotation is the conjuncture of fingerboard, top, and heel of the neck, the reason for most resets is flattening of the back curved surfaces. The longitudinal curve of the back is placed in tension and flattens thus getting longer and allowing the neck block to rotate on it's pivot point.
Tom
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A person who has never made a mistake has never made anything!!!

Agree with Dennis here big time. I use a Spanish foot or similar on the bottom of the heel block and two scrap blocks running from the heel block to the UTB like in the attached picture. I also make sure the UTB and top of the X's are tucked into the linings. I've seen a big improvement in how much the neck angle wants to change over time.

A very good point The soundboard may be under the most stress, but it's the whole box that deforms.

For this particular problem of the back flattening, use a cylindrical back radius so it's flat to begin with. Or at last a headblock foot or A-frame between the headblock and first back brace. Or A-frame all the way to the second back brace if using the buttress structure. If you look at it in 3 dimensions, the headblock, buttresses, second back brace, and A-frame braces all combine to form a (slightly stretched) tetrahedron... one of the most naturally rigid geometric shapes

But of course it's possible to need a reset even with all the tricks. This thread is about understanding and avoiding common design elements that virtually guarantee the need for a reset.

Why is needing a neck reset a bad thing?

My car will need a timing belt replaced at 100,000 miles. My house will need a new roof in 20 - 30 years. My central air will likely be toast in 10 years. Sheesh I may be toast in 10 years....

Neck resets are an expectation of owning a fine acoustic steel string guitar.

We can build them like a brick crap house... heavy as can be too and likely avoid that neck reset but who wants an instrument that sounds like and outhouse with strings on it.....

These days CF is promising and many folks have done some pretty creative things with it. But at what cost in terms of sacrificing future serviceability, real-time enjoyment right now.....etc.

It just may be.... that those who came before us..... had things pretty much understood all things considered. Imagine that!

I wanted to add that a lot of this will depend on one's individual view of what a guitar is.

For me it's a tool for musicians and as such the big three for them is tone, playability, and serviceability/reliability. Purchase from a decent company or maker and the neck reset will be covered under warranty.

As such it does very much seem to me that a reset proof guitar is not a goal that's more important than a great sounding, great playing, easily serviced and well backed by the maker instrument available today.

I applaud any effort to find a better way forward but I'm also keen to keep an eye on what the tradeoffs might be as well. As such this is kind of a solution looking for a problem in my view.

Even the universal atomic clock needs calibration occasionally -- what's the shame?

The purist believes they can hear HHG -- I am thinking a HD28 with a bunch of carbon fiber rods/reinforcements may not be accepted with open arms?

We are artisans working with an organic medium -- what's the old saying -- "you don't want to mess with mother nature"

McPherson's have a metal reinforced necks, but they still made mechanical provisions to deal with the forces of nature.

Interestingly, Bob Taylor designed guitars with a user friendly neck joint -- which includes a more robust upper bout construction.

And how about the owners taking care of their instruments -- It was rare when I saw deformity and/or damage that was not initially caused by dehydration.

Sorry to ramble -- I am comfortable with how most guitars are constructed and what is necessary to keep these musical tools going.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Money. Even under warranty, most guitars will need shipped back and forth to their maker, which is expensive. And what if the maker is dead?


But all the time I see people do things that encourage excessive creep in bad places for no clear tonal benefit. The beauty is that you can have stability and tone at the same time. The guitar naturally lends itself to it.

The upper bout is damped by the fingerboard extension, and coincidentally is the place where rigidity is most beneficial. The soundhole area is pinched by the waist so even if you put the hole somewhere else, you don't gain that much vibrating area. And in the normal style, making it stiff isn't going to hurt much, since vibrating a hole up and down is sort of ineffective at moving air anyway. And then below the soundhole, you can loosen it up, get it moving, and let it creep since it's going to take a lot before the bridge is raised above the fret plane.


The steel string guitar is still a young instrument, and there's a lot of variety in how they're built. As far as I know, Ervin Somogyi is the first to produce a significant number with a design that's intended to resist needing reset without sacrificing tone. And as of the writing of his first books, it's apparently pretty successful. Maybe not permanently eliminating the need for them, but at least lasting a lot longer than most. It would be interesting to know what his current statistics are, now that a larger number of his guitars have reached age 30. I'll shoot him an email and report back if he's willing to share...

My car has a timing chain. 240K, and no issues. Spanish guitars from 150 years ago had a slipper foot, a mostly cylindrical back profile, and a faired in trailing edge on the bridge. It just may be that those who came before the "American steel-string guitar" had pretty much understood many of the structural issues that still plague the "traditional" design.

Exactly! We're the newbs....

Let's look at what neck reset time is all about with real-life examples. In the last 30 days we reset two pre-war Martins. In addition to resets both instruments needed maintenance as most guitars that need resets do and did.

In this case both required fret work, a refret and a partial refret, both had splitting bridges that needed to be replaced, both needed new saddles and nuts, and both needed their tuners serviced to keep em working nice and smooth. Additionally both guitars who belong to professional performers had old UST pup systems that the crystals had oxidized and were no longer performing reliably so new, modern USTs were obtained and retrofitted with the saddle mill in the saddle slots of the new shop-made bridges.

Point being that when it's neck reset time it's often time for fret work, bridge plate caps, bridge replacements, etc. We unaffectionately call it the "whole nine yards."

Now had these guitars been purchased by the stewards today much of this would have been covered under warranty. I've seen and participated in Martin covering warranty repairs 50 years out with the only proof of being the original owner was a black and white photo of a 9 year old toothless kid smiling and holding the D-35.... What a company by the way backing clients with little and even no documentation on a case by case basis.

I'm not against augmenting upper bout structure for more time between resets, etc. and I did and do this myself but I do think that reset time is not necessarily a bad thing and a quality guitar from a quality maker will often cover the reset. Taylor is another example. The extra beef in the upper bout does not preclude the need for a reset but the engineered implementation of how the neck is attached and angled is so very cool that we can reset a Taylor in minutes.... not hours or days.

Taylor's approach is different in that they clearly acknowledge the eventual need for resets so they made them WAY easier to do, faster too and I will add with a degree of predictability as well. Pretty cool in my view as well.

When any of us use a bolt-on we too are making neck resets someday easier so long as we don't finish the steel string beast with the neck on....

I wasn't aware of Ervin's neck joint but I have to suggest too that his "double sides" approach that incredibly stiffens the rim likely goes a long way toward belaying upper bout distortion as well.

So is it mainly the sides that distort causing the need of a reset?

Some of this depends on the maker and specific design but generally speaking because of constant string tension and I'll add likely drying out and being overly humidified as well the upper bout of the instrument distorts over time. In many cases you can see this visually simply by standing the instrument in front of you and observing where the neck meets the body and following the side curves to this point. You can see at times even a depression where the sides in the neck block area are now pushing inward as the upper bout of the guitar is distorting again because of string tension and likely RH cycles over time.

A neck reset does not guarantee that the upper bout distortion will stop and future neck resets may be required as well.

As an observer of all things the worst upper bout distortion that I've personally seen is generally on instruments that have lived their lives with mediums on them, more tension, neck rest time comes sooner.

There are of course contributions to the side distortion from the back (as Dennis mentioned) and even the top likely as well. It's just not the sides but the side distortion can actually be observed in time with the naked eye.

Some of us believe that resets are an expectation of the beasts in time just like many things in life tend to be. Engineering the need for a neck reset out of the designs has been attempted likely for centuries at least to some extent. It's also likely that the benefits had diminishing returns in terms of other unintended things such as less responsiveness, more mass, etc.

With today's material science we do have opportunities that we have never had before, true! But again if I was still building my efforts would continue to be directed toward responsiveness and tone, playability, and serviceability and reliability. I don't view the need for a reset in time as a detriment to reliability. All things including us.... do tend to need some TLC in time and that's not always a bad thing again IMO.

If a guitar can be designed that does not take away in the least from the big three for me AND is neck reset resistant I would be all for it. It's just not where my focus would be knowing as I do that some very bright men and women have already been to this movie before it's not gotten them to where they might have wished to be.

Not to be a space cadet.... but I've always believed that it's mathematically arrogant to not believe in other life in the universe.... I know, I know what's this have to do with guitars? I kind of sort of view efforts to neck reset proof a guitar the same way, it's perhaps in some cases and this is NOT directed at my friend Dennis arrogant to turn a blind eye to the very good work of those who came before us in terms of guitar design and construction as well. They had all the same issues, all the same needs, all the same skills, math, engineering, physics, etc. We do have materials that they did not have this is true.

Even in recent times in the last 5 years or so major manufacturers have also taken on this issue yet we still see pretty much what we saw at the turn of two centuries ago as far as design and engineering with a few exceptions.

One more thing too. A HUGE part of the prospective market is not keen to be the test cases for someone's new engineering thinking. Martin fans specifically where tradition rules the day. To some of them even a B*lt-on neck is sacrilegious and to be avoided at all costs....

[/quote]
To stir things up a bit. All guitars that need resets do not of necessity have poor upper bout structure in the top. Given that rotation of the neck block happens to cause a need for reset and the pivot point of rotation is the conjuncture of fingerboard, top, and heel of the neck, the reason for most resets is flattening of the back curved surfaces. The longitudinal curve of the back is placed in tension and flattens thus getting longer and allowing the neck block to rotate on it's pivot point.
Tom
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Design changes that improve longevity and don't hurt tone are a worthy goal.

I have heard the Idea above before. Is the longitudinal back arch superfluous? Wood sure doesn't like to be bent into the shape of a basketball. Is it just a concession to the ease of holding rims against a motorized bowl? As far as stability enhancements, a cylindrical back arch seems like low hanging fruit.

Very well said. Especially since it is well demonstrated that the upper bout contributes mostly to air volume and little to nothing in terms of resonance.

There are a variety of ways to improve the upper bout structure over a traditional "martin" neck block with zero discernable impact to tonal quality. I'll keep my comments brief and legible - I believe it is the plight of those currently building instruments - that is, craftspeople - to ever advance their craft, based on the work of those prior to and around them.

Andy