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Does anyone know how big the +/- ranges around the values for wood properties in the wood database are in general? 10%, 20%, 40%? I imagine it varies with species, but I'm wondering how much the mechanical and physical properties of different species actually overlap in the real world. For example Sitka and Engelmann appear to have some substantial differences in the numbers below but if the +/- on the numbers is large, then there could be many top sets of these species that would be indistinguishable in terms of these properties. On the other hand, Sitka and Red appear to be quite similar, but if the +/- is large, there would be individual top sets of each that would be distinctly different, which I expect is the case.


Sitka Spruce White Spruce Red Spruce Engelmann Spruce
Avg dry weight 27 lb/ft3 27 lb/ft3 27 lb/ft3 24 lb/ft3
Spec gravity 0.42 0.43 0.43 0.39
Janka hardness 510 480 490 390
Modulus of rupture 10,150 8,640 9,580 9,010
Elastic modulus 1,600,000 1,315,000 1,560,000 1,369,000

These numbers are from the Wood Database web site (http://www.wood-database.com/about/) and I believe are taken from the USDA Wood Handbook.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Argh. I can't figure out how to preserve the table format for the numbers. I think you all can figure it out though.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

In the wood I have measured ( thousands of sets) I have found a very wide variation in material properties. So much so that I do not view top wood material properties by species but as individual examples that can be on either extreme of the "average" properties that are commonly listed in wood engineering literature

There is a lot of variation and overlap between species. The key to spruces (as far as it fits our purposes IMO) is density... weight tracks longitudinal stiffness in a pretty linear fashion so that a heavy Englemann and a light Red spruce can be very similar on a finished guitar.

In other words you will find that a 100g spruce top is likely very close in long grain stiffness to any other 100g spruce top, regardless of species.

Yes, lots of variation and overlap within and between species. Long grain Young's modulus within a species can vary by a factor of two, for example. Measured properties are also dependent on the quality of the cut. How well a piece is quartered will significantly alter its measured cross grain stiffness. The better guitar design and build books have tables of material properties for the commonly used guitar woods along with their standard deviation and include how to measure these properties and what to do about it. Obviously, building to dimensional targets is a recipe for substantial variation in acoustical performance.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

While this is statistically true, there are exceptions to this for sure.

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Jim Watts
http://jameswattsguitars.com

I have never found Englemann and red spruce to have any similar qualities tonewise. Never get the headroom with Englemann that you get with red spruce. In addition, I find red spruce (no matter what the individual tops numbers) builds a fundamental sounding instrument, while Englemann builds a complex sounding instrument.
I really don't find much use for such information as it just clouds your mind with an overload of numbers.
Must be pretty important for those that build by numbers though...

From what I've seen, the "lower" grades of Engelmann spruce tend to be heavier (stiffer) and look more like red spruce than the creamy white (lighter and softer) "higher" grades of Engelmann. Some of the ugly Engelmann I've used seemed like it had plenty of headroom.YMMV

Yea, I've got 40-60 of those A grade Englemann tops, stiff, but they still don't make it compared to my red and sound like mushy German spruce, complex but not half the power of real German. Most have the compression grain, but just don't have the power. I use them for popsicle braces and doublers around the soundhole between UTB and LTB or X and UTB. Been my experience that only red sounds like red.