Martin D-28, HD-28, and tension

[Troubador]

Do different kinds of bracing have an effect on tension? For instance, do the non-scalloped braces of the D-28 make it less susceptible to the effects of tension than the scalloped braces of the HD-28? And what about forward-shifted bracing vs. standard shifted -- which exerts more tension on the guitar? Based on the possible/probable ill effects of tension, which of these would be less likely to suffer the harmful effects of tension and likely need a neck reset somewhere along the way? The older D-28 with non-scalloped, standard (non-forward-shifted) bracing; the reimagined D-28 with forward shifted, non-scalloped bracing; the older HD-28 with scalloped, standard sifted braces; or the reimagined HD-28 with forward shifted, scalloped braces? Or does the bracing not make any difference in this matter?

[OldFrets]

Nope. Here is the formula for string tension:



where T = tension, L = scale length, F = frequency (pitch), and μ = the unit mass of the string (related to the gauge, winding material, and construction of the string). This equation holds true whether the string is on an X-braced guitar, a ladder-braced guitar, a piano, or strung up between two walls. Bracing doesn't enter into it.

Source.

[Troubador]

Originally Posted by OldFrets

Nope. Here is the formula for string tension:



where T = tension, L = scale length, F = frequency (pitch), and μ = the unit mass of the string (related to the gauge, winding material, and construction of the string). This equation holds true whether the string is on an X-braced guitar, a ladder-braced guitar, a piano, or strung up between two walls. Bracing doesn't enter into it.

Source.

Interesting, and thank you. It seems to me, however, that less bracing (scalloped) would mean less support for a guitar top, as compared to non-scalloped bracing. How could that not make a difference over the years to the structural integrity of the guitar?

[OldFrets]

Certainly, the bracing can have a major effect on the structural integrity on the guitar. So can the string tension. But the answer to your first question - do different kinds of bracing have an effect on tension - is no.

[Troubador]

Originally Posted by OldFrets

Certainly, the bracing can have a major effect on the structural integrity on the guitar. So can the string tension. But the answer to your first question - do different kinds of bracing have an effect on tension - is no.

I probably asked the wrong question then. So, which of the bracing patterns has the least detrimental effect on the structural integrity of a guitar? I would guess it would be standard shifted, non-scalloped bracing. Or does forward shifted not make any more difference than standard shifted?

[davenumber2]

I don't think any bracing pattern is inherently less stable or structurally deficient. It's a blanket statement you can't make. Take two of the same exact guitar with the exact same bracing. One needs a neck reset after two years, the other never needs one. What does that tell you? Nothing. It comes down to the individual guitar. Wood moves and it's not always predictable.

Then again you could drastically overbrace a guitar to make so it never moves but then it would sound like you're playing a 2x4 with strings. It's a balance between structural strength while being resonant and light enough to produce a pleasing tone no matter the type of bracing.

[jmjohnson]

I would guess it would be standard shifted, non-scalloped bracing

Makes sense - Considering they (supposedly??) moved the bracing rearward due to warranty issues, I would think "forward shifted" may be impacted by the tension more.

[Troubador]

Originally Posted by davenumber2

I don't think any bracing pattern is inherently less stable or structurally deficient. It's a blanket statement you can't make. Take two of the same exact guitar with the exact same bracing. One needs a neck reset after two years, the other never needs one. What does that tell you? Nothing. It comes down to the individual guitar. Wood moves and it's not always predictable.

Then again you could drastically overbrace a guitar to make so it never moves but then it would sound like you're playing a 2x4 with strings. It's a balance between structural strength while being resonant and light enough to produce a pleasing tone no matter the type of bracing.

What you say is undoubtedly true -- "It comes down to the individual guitar." And also your last sentence. But generally speaking, doesn't it make sense that a guitar with more wood in the bracing -- non-scalloped -- would give more structural integrity than a guitar with less wood in the bracing -- scalloped bracing? Wouildn't non-scalloped support the top better than scalloped?

[davenumber2]

Originally Posted by Troubador

What you say is undoubtedly true -- "It comes down to the individual guitar." And also your last sentence. But generally speaking, doesn't it make sense that a guitar with more wood in the bracing -- non-scalloped -- would give more structural integrity than a guitar with less wood in the bracing -- scalloped bracing? Wouildn't non-scalloped support the top better than scalloped?

In theory maybe, but you have to take into account the stiffness of the wood used for the bracing. I just don't think it's simple enough for a yes/no answer.

[Troubador]

Originally Posted by davenumber2

In theory maybe, but you have to take into account the stiffness of the wood used for the bracing. I just don't think it's simple enough for a yes/no answer.

Fair enough. If you had a custom guitar made, what kind of bracing would you choose as the best bracing for structural support combined with desirable tonal quality?

[drtedtan]

You have to take into consideration how much stiffness is required in a given area of the top in order to support the string tension, and that will vary based on the bracing pattern, bracing stiffness, braving thickness, top stiffness, top thickness, top size, top shape, guitar tuning, etc., etc..

In short, this can’t be generalized as there are too many variables in play.

[drtedtan]

Originally Posted by Troubador

Fair enough. If you had a custom guitar made, what kind of bracing would you choose as the best bracing for structural support combined with desirable tonal quality?

Choose the bracing in conjunction with the luthier based on how you want the guitar to sound. The luthier will ensure the structural integrity as best they can. And an individual luthier can address this better than a factory due to the extra time and attention they can give to each individual top/bracing combo.

[Troubador]

Of the four Martin guitars I have mentioned -- older and reimagined D-28, older and reimagined HD-28 -- which one, generally speaking, would have more structural support based on bracing patterns?

[drtedtan]

It doesn’t work that way. Guitars are braced to sound a certain way while also supporting the top against string pull.

If we are talking generalities, a better quality guitar will be built lighter in order to achieve better tone and responsiveness. They will generally cost more, in part due to the expectation of some warranty repairs.

Likewise, lower quality guitars are generally overbuilt in order to avoid warranty repairs. This is part of why they cost less (only a part, but a part nonetheless).

So if structural support is your primary concern, look to entry- and mid-level guitars. They’ll likely be more robustly built (but at the expense of tone and responsiveness).

[Troubador]

Originally Posted by drtedtan

It doesn’t work that way. Guitars are braced to sound a certain way while also supporting the top against string pull.

If we are talking generalities, a better quality guitar will be built lighter in order to achieve better tone and responsiveness. They will generally cost more, in part due to the expectation of some warranty repairs.

Likewise, lower quality guitars are generally overbuilt in order to avoid warranty repairs. This is part of why they cost less (only a part, but a part nonetheless).

So if structural support is your primary concern, look to entry- and mid-level guitars. They’ll likely be more robustly built (but at the expense of tone and responsiveness).

So, I can expect my Recording King RO 328 to offer better structural support than my Martin HD-28?