Target Plate Thickness for 0/Parlor Guitars

[OiAcoustics]

Hi all

I measured 9 top plates today and calculated targeted thicknesses for 343 mm wide 0 guitars. Adirondack, Engelmann, Lutz and Sitka. I look a random 10% stiffness reduction considering the top width. The consistency was remarkable considering the variety:

Natural Tops targeted 1.76 to 1.89 mm thick, 110 to 121 grams. This is thinner and lighter I've been making X braced (of course), and will be on my first SS falcate guitars with 140# tension (per D'Addario's #s).

Seems quite thin to me - my gut was to NOT take the stiffness reduction, but surprisingly it didn't affect the calc.

The torrified tops thinner, as expected, 1.64 to 1.74 mm, and super light 94-102 grams. Seems they are so light I can afford to stay with the same thickness as the others?

Any of you with experience with small body falcate guitars like these?

[kiwigeo]

I've just strung up a falcate braced parlour guitar Ive been working on for 2 years now. From memory the bracing dimensions were pretty much as per The Books. The guitar sounds loud and has more balls than any of my larger bodied builds.

[johnparchem]

The smallest I have gone is falcate braces on a 00 body. In terms of the calculated thickness, I suspect there is a minimum thickness required for falcate or x braced guitar for the structural requirements. I retopped (a dropped) lattice braced guitar with a top around 1 mm. The lattice distributed the bracing such that the top plate itself did not have to distribute load. I do not like to go much thinner than 2 mm on a classical and a bit more on a steel string to keep the braces from telegraphing thought the top. I do not have any real data though

[Trevor Gore]

I measured 9 top plates today and calculated targeted thicknesses for 343 mm wide 0 guitars. Adirondack, Engelmann, Lutz and Sitka. I look a random 10% stiffness reduction considering the top width.

If you're using the formulae in the books for the elastic constants, measuring them correctly and applying them correctly in the thickness formula, there is no need to make any "random 10% stiffness reduction considering the top width" as the guitar body dimensions are taken into account when calculating thickness.

My small body classical is about Martin 0 size and whether computing thickness for classical or steel string guitars as per the book, they all come out thicker than your numbers. Probably best to check your calculations and measurement methods.

[OiAcoustics]

HI Trevor

I suspected as much. I found it curious that a "reduction", per the Book where you noted we're "free" to use a lower stiffness value and hence thinner top, didn't result in a reduced thickness, which do seem to be thinner than I expected - which I though might be about 10% thinner than for an OM. The formula replicates your results when plugging in the numbers from your chart in the Book. Dimensions and weight are obvious enough, all that's really left is the frequency #s... which of course I'm new at. But they came out quite consistently... and the torrified tops thinner and lighter, which also made sense. Can you give me a general range sense of the range of your small body Sitka thicknesses, not to build by, but with double checking to see if I can get in the right range? Certainly somewhat thinner than an OM, but not this much!

[OiAcoustics]

I've just strung up a falcate braced parlour guitar Ive been working on for 2 years now. From memory the bracing dimensions were pretty much as per The Books. The guitar sounds loud and has more balls than any of my larger bodied builds.

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I imagine you're pretty pleased with that outcome! I haven't mucked much with the bracing, other than my soundholes are moved into the upper bout regions so I have more unbroken plate to work with... it's just the plate thicknesses I thought too thin. About ready to delve into rebracing an X topped 0 that had bad wolf notes following some bad advice per another one of my threads, now following Trevor's. I hope for the same result.

[OiAcoustics]

I measured 9 top plates today and calculated targeted thicknesses for 343 mm wide 0 guitars. Adirondack, Engelmann, Lutz and Sitka. I look a random (I should have said INITIAL) 10% stiffness reduction considering the top width.

If you're using the formulae in the books for the elastic constants, measuring them correctly and applying them correctly in the thickness formula, there is no need to make any "random 10% stiffness reduction considering the top width" as the guitar body dimensions are taken into account when calculating thickness.

My small body classical is about Martin 0 size and whether computing thickness for classical or steel string guitars as per the book, they all come out thicker than your numbers. Probably best to check your calculations and measurement methods.

OK I think I've found it... my body is an unusual shape - the neck intersection is at a 30 degree angle so that there's no hard cutaway corner, but a smooth curve instead. The neck fits in a slot and is adjustable for pitch. So I used the centerline dimension for the plate as an average length; once I added in 20mm for the full plate length to be consistent with yours, and used 75 for stiffness, the #s fell into place:

Torrified tops 2 - 2.1 mm 112 to 122 grams if I keep them that thin. This seems to verify their reputation, and should rock.
Natural tops 2.06 - 2.29mm 124 to 145 grams depending on species.

Except one Sitka top which is obviously quite dense - about 40% more than the others, but didn't tone out to save on thickness and hence is well over a good targeted weight for a 6 string small body. I'll recheck that but maybe it'll be OK for a 4 string tenor guitar which is quite highly strung...?

thanks for your thoughts, glad my gut told me to post the question, as these new targets seem much more realistic at 13% thinner than an OM top. Your methods are awesome - I'm so glad I bought The Book and The Video as they turn out to be a bargain vs. trial and (much) error by "feel".

[OiAcoustics]

I found it curious that a "reduction", per the Book where you noted we're "free" to use a lower stiffness value and hence thinner top, didn't result in a reduced thickness,

Obviously that statement is incorrect... I don't know why it didn't come out correctly the first time, but at least it did upon review.