Torrefaction and no tongue brace build

[BrunoBlack]

I'm not sure where to post this, but it seems like this might be the best place. I notice that Collings and other builders are using torrefied guitar tops AND leaving out tongue bracing. It is widely known that Torrefaction degrades wood cellular structure and as a result compromises mechanical properties (for those who like scientific journals, here is a very typical report. http://www.afs-journal.org/articles/...7/07/f7071.pdf) ----

And there was a belief at one time that designing guitars WITH a tongue brace was a good idea. As Collings points out on there support web page: "The tongue brace is a flat, thin brace that runs across a guitar's upper bout underneath the tongue of the fingerboard. String tension is always pulling the neck and fingerboard towards the body of an acoustic guitar and a tongue brace helps to reinforce this area to prevent the top from cracking along side of the fingerboard tongue. This cracking is only a potential problem and one that most likely wouldn't be an issue for 40 or 50 years. The tongue brace was originally developed in the late 1940's after cracking occurred on some popular pre-war instruments.........In the long run, a tongue brace is a good safeguard against tension cracks, however if you would prefer to have it left out it should not appreciably affect the structural integrity of the guitar for many years." http://www.collingsguitars.com/faq.html#23

Since these "Authentic" and "Traditional" builds are lightly constructed to mimic pre-war builds, doesn't the combination of degraded wood, lighter builds and the elimination of the tongue brace seem to be tempting fate.

Of course, almost anything can be reduced to appropriate engineering when all the variables are understood. But the combination of these features at least has my attention. Any thoughts out there?

Paul

[Truckjohn]

I think its been pretty well established that ebony fretboards and their forever shrinking nature is responsible for the fretboard edge cracks on the soundboard that the Popsicle brace is supposed to prevent.

Seems like manufacturers have figured out how to work around it by now for the most part... Or they stopped using ebony....

Thanks

Originally Posted by Haasome

And there was a belief at one time that designing guitars WITH a tongue brace was a good idea. As Collings points out, String tension is always pulling the neck and fingerboard towards the body of an acoustic guitar and a tongue brace helps to reinforce this area to prevent the top from cracking along side of the fingerboard tongue. This cracking is only a potential problem and one that most likely wouldn't be an issue for a long time. The tongue brace was originally developed in the late 1940's after cracking occurred on some popular pre-war instruments.

Martin always used a "tongue" or "popsicle" brace on their 12 fret guitars. It was omitted from the OM in 1929 and subsequent 14 fret guitars until 1939.

I'm not convinced it adds significant stability to the upper bout, and it surely doesn't prevent cracks. John Arnold, Brian Kimsey, and others use a short trapezoidal brace between the neck block and #1 cross brace. That doesn't limit vibration of the upper bout and adds considerably greater structural stability. Lot's of builders have come up with other solutions.

I have several guitars without a tongue brace. Some started life that way and others have had it removed. I don't baby them too much and none have shown issues. Building without that brace would be high on my list of choices in a custom build. I believe the tone is better without them.

And Collings isn't the first to build with torrefied tops and without the brace. Martin 14 fret Authentics based on pre-39 guitars don't have them either.

[John Arnold]

The tongue brace was originally developed in the late 1940's after cracking occurred on some popular pre-war instruments.

The popsicle brace predates the 1940's. All 12-fret Martins had them, starting in the 1800's. Martin added the popsicle brace to their 14-fret models in mid-1939.
What you may be missing is that torrefaction makes the wood more stable, which means less movement that could create tension at the fingerboard edge.
There are two factors that enter into this failure:
1) Age related shrinkage at different rates (ebony and spruce).
2) Heat, which can loosen glue joints that are cross-grain.
If you are serious about eliminating the failure, I recommend the trapezoidal brace instead of a popsicle. It avoids cross-grain construction, leaves the top in the upper bout free to vibrate, and eliminates neck block shift.

[BrunoBlack]

Todd and John, I appreciate your contribution to this commentary. I do not build guitars, so your perspective is very useful to me. FYI, I did edit the statement in my OP to provide proper attribution to Collings Support for the statement on tensile stress.

BTW, I own & enjoy 3 guitars with no tongue brace and live/play those without concern. My concern is with the potential influence and long-term viability of Torrefaction.

Paul

Originally Posted by Haasome

...I do not build guitars, so your perspective is very useful to me...

Nor do I. I know you know this, but before anyone else counts my opinion along with John Arnold, I want to be clear on that. I'm an engineer. I like math and I'm prone to tinkering.

While material science is not my area of professional engineering, I did read the report you posted. I would that the mechanical properties were changed rather than degraded. Impact strength seemed to be reduced the most, but compressive strength parallel to the grain actually increased. I'm not sure how this particular treatment compares to the way tone woods are treated either.

All in all, I'm not terribly concerned about longevity of instruments from the major manufacturers. If just one company was using it, I might wonder if they'd thought it through. With so many relatively conservative makers using it, I have to think they're pretty confident in the product.

I've been able to play a few otherwise identical guitars where the only change was a torrefied top. It consistently and definitely makes a tonal difference, and in most cases I preferred the torrefied top. That was in two brand new guitars though. I'm anxious to hear the difference 5-10 years down the road. Even with all that, I do not think I would choose a torrefied top for a custom build.

[BrunoBlack]

Originally Posted by Todd Yates

...
While material science is not my area of professional engineering, I did read the report you posted. I would that the mechanical properties were changed rather than degraded. Impact strength seemed to be reduced the most, but compressive strength parallel to the grain actually increased. I'm not sure how this particular treatment compares to the way tone woods are treated either.

.

You might not be a guitar builder, but you are incredibly knowledgeable about these things. So, your opinion is valued. And not to belabor the point, but...

Todd, from the abstract : "The possible effect of degradation and modification of hemicelluloses, degradation and/or crystallization of amorphous cellulose, and polycondensation reactions of lignin on the mechanical properties of heat treated wood have been discussed."

Also, from the Conclusions: "The tensile strength parallel to the grain showed a rather large decrease, whereas the compressive strength parallel to the fibre increased after heat treatment. The bending strength, which is a combination of the tensile stress, compressive stress and shear stress, was lower after heat treatment."

While I am not an expert on Torrefaction, my use of the word "degradation" in my OP extends beyond the article to conversations with other researchers who are expert in this area and my personal review of other literature on Torrefaction that I have read over the years. To be clear -- I don't know. I'm only concerned.

We heard about all kinds of issues when torrefied wood first started to be seen in the guitar market. Normal finishes wouldn't stick to it, glue wouldn't stick to it, and so on. Most of the builders are now saying it's not difficult to work with, so I don't really know if the early issues were overblown, imaginary, or what. I do think it sounds different, better in some ways. However, I don't see it as a silver bullet or a huge leap forward. But I was always a cautious child.

[Bruce Sexauer]

I use the equivilent of a tongue brace in my 12 fret guitars, but not for the reasons ascribed by the "Martin analysts". It seems highly unlikely to me that there is any original information on the implementation of the concept, and I increasingly believe that the popular guitar world misunderstands the purpose of this class of brace.

[BrunoBlack]

Originally Posted by Bruce Sexauer

I use the equivilent of a tongue brace in my 12 fret guitars, but not for the reasons ascribed by the "Martin analysts". It seems highly unlikely to me that there is any original information on the implementation of the concept, and I increasingly believe that the popular guitar world misunderstands the purpose of this class of brace.

So Bruce, what is your take on the purpose of this brace?

Paul

[CaffeinatedOne]

Does a Spanish heel (with its fingerboard extension support) offer a similar structural benefit? I'm not thinking of the side inlay construction, but of the nature of the top and back support offered by the neck block itself.

Ibanez:


Haxton:

[Bruce Sexauer]

Originally Posted by Haasome

So Bruce, what is your take on the purpose of this brace?

Paul

I use the brace as one of the controls for tonal balance in the top. I have seen no evidence that it creates or prevents cracks in the top beside the fingerboard. I believe those usually come from stresses caused by the neck collapsing into the top. I do address that problem, so well known in older Martins, but through a different means.

IF cooked wood is less stiff cross grain, as I think I read here in this thread, then tossing the "tongue" brace is questionable in my concept. There are a number of "known" things about how acoustic guitars work which are similarly debatable. This is one where I am increasingly confident that my POV is working for me.

I imagine that most readers will favor the party line, and that's alright with me, but for those who like to question assumptions, this is a good one.

[printer2]

Degradation of the wood components, mainly hemicelluloses, is not so much that they have been changed in a way but rather that they have been cooked out of the matrix. The hemicelluloses is the component of wood that is mainly the reason wood shrinks and swells in different humidity's. Reduction of this component means that the wood is more stable and may have an extended life because of it. So if a guitar with baked components is strong enough when it is made maybe it will be strong enough 50 years on.

[BrunoBlack]

Originally Posted by printer2

Degradation of the wood components, mainly hemicelluloses, is not so much that they have been changed in a way but rather that they have been cooked out of the matrix. The hemicelluloses is the component of wood that is mainly the reason wood shrinks and swells in different humidity's. Reduction of this component means that the wood is more stable and may have an extended life because of it. So if a guitar with baked components is strong enough when it is made maybe it will be strong enough 50 years on.

I'm afraid this is where we diverge from the practical and perhaps lose readers with general interest in this topic. I would offer that the role of hemicellulose is extremely complicated. It does many things, but one of the primary functions is the coupling of cellulose and lignin to enhance the mechanical properties of the cell walls of wood. Wood is made of cellulose, hemicellulose and lignin (with a minor contribution ~5% of other things). Hemicelluloses constitute 20%-35% of the total dry weight of cell wall matter. That's a high percentage of material to be "cooked out" of wood - if it is in fact removed. I think a lot of what happens to the constitution and properties of "baked" wood depends on the temperatures, duration and overall process that is used. And then we do not have good (or any) evidence about how all this influences the long-term performance of a guitar.

[printer2]

Originally Posted by Haasome

I'm afraid this is where we diverge from the practical and perhaps lose readers with general interest in this topic. I would offer that the role of hemicellulose is extremely complicated. It does many things, but one of the primary functions is the coupling of cellulose and lignin to enhance the mechanical properties of the cell walls of wood. Wood is made of cellulose, hemicellulose and lignin (with a minor contribution ~5% of other things). Hemicelluloses constitute 20%-35% of the total dry weight of cell wall matter. That's a high percentage of material to be "cooked out" of wood - if it is in fact removed. I think a lot of what happens to the constitution and properties of "baked" wood depends on the temperatures, duration and overall process that is used. And then we do not have good (or any) evidence about how all this influences the long-term performance of a guitar.

Only a portion of it is removed. Their is enough material available on the internet on what happens to organic material when it goes through the torrefaction process. Just need to wade through it and determine how it relates to the mild process used for guitar wood.