Technical Data

Below are variety of articles, tables, comparisons, charts and so forth, all dealing with various technical considerations that one may wish to think about prior to commencing a build. It is by no means complete. If you know of additional information, feel free to send it this way.

Below is a list of what has been posted; scroll down to read further.

GlossarySelecting Wood for Musical InstrumentsConsiderations for the BuildJanka Hardness ScaleWood ShrinkageFrom Jan Arts Guitars: Why Some Woods Are Best for TopsComparative DataTop Wood RankingToxicity in WoodsSupport Sound PortsFrequency of Woods

Glossary

Annular lines Also called growth rings or grain, the lines in wood that correspond to one year of growth. For tonewood used for musical instrument tops and soundboards, close annular lines are one of the indicators of strength and good musical qualities such as better projection and greater clarity.

Bearclaw Bearclaw, like the curl in curly maple, is a rippling of the longitudinal fibers, which divides the surface of the wood into shimmering patterns, often seen in more expensive Sitka Spruce.

Bee's WingA small-scale, very tight, mottle figure is sometimes referred to as "bee's wing" figure due to the similarity with what the wing of a bee looks like. East Indian Satinwood is extremely well known for having this figure, and it also occurs occasionally in Narra, Mahogany and Eucalyptus. So when is a figure "block mottle" and when is it "bee's wing" ... well, pretty much whenever a particular dealer decides that's what they want to call it.

Bird's EyeA few woods, most notably Maple but also Anigre and a few others, can exist with large numbers of small round "defects" that do indeed resemble the eyes of birds. The density of the eyes ranges from sparse to dense; this is not a good figure to buy sight unseen. A good, truly dense, bird's eye maple board can make a spectacular addition to a project.

Chatoyance Showing a band of bright reflected light, iridescence.

Compression An area where the annular lines change from evenly spaced to significantly farther apart. Compression may occur as a result of a series of warmer than normal winters where the tree has a longer growing season. CurlyContortions in grain direction sometimes reflect light differently as one moves down the grain and this creates an appearance of undulating waves known as curly grain. It is frequently described as looking like a wheat field in a mild wind, and can be so strong an effect that your eyes will swear that a flat piece of wood has a wavy surface. Many species develop this figure, Maple being a very common example. . An extreme form of curly figure is called "fiddleback". The amount of curl in a wood sold as "curly" can range from almost none to truely spectacular.

FiddlebackCurly figure in wood (and fiddleback is just a variation of curly) is caused by contortions in grain direction such that light is reflected differently at different portions of the grain, creating an appearance of undulating waves, also called a "washboard" effect because it looks like an old corrugated-steel washboard. "Fiddleback" figure is a form of curly figure where the curls are very tight and fairly uniform, generally running perpendicular to the grain and across the entire width of a board. The name comes from the fact that such wood became popular to use on the backs of violins (fiddles), and nowadays guitars, because the figure is frequently very lively and attractive and such wood generally has good resonance properties. Logs for fiddleback veneers are quartersawn to produce very straight grain with curls running perpendicular to the grain and uninterrupted from edge to edge of the sheet. Many species develop this figure, but the most common ones are Maple, Makore, Anigre, and "English Sycamore" (which is actually a form of maple). Some of the prettiest versions occur in Claro Walnut, Myrtle, and Moa.

Figure The pattern produced in a wood surface by annual growth rings, rays, knots, and deviations from regular grain. Fiddleback, Curly, Bee's Wing, Bird's Eye are all examples.

Grain Grain is often used in reference to annual growth rings, as in "fine" or "coarse" grain; it is also used to indicate the direction of fibers, as in straight, spiral and curly grain. The direction of the grain, as well as the amount of figuring in the wood, can affect the way it is sanded and sawed. Grain is also described as either being "open" or "closed", referring to the relative size of the pores, that affects the way a wood accepts stain and finish.

Heartwood Heartwood is the older, harder central portion of a tree. It usually contains deposits of various materials that frequently give it a darker color than sapwood. It is denser, less permeable and more durable than the surrounding sapwood.

Medullary Rays Medullary rays extend radially from the core of the tree toward the bark. They vary in height from a few cells in some species, to four or more inches in the oaks; theyre responsible for the flake effect common to the quartersawn lumber in certain species.

Plainsawing Plainsawing is the most common and least expensive method of sawing; most wood flooring is cut this way. Plainsawn lum ber is obtained by making the first saw cut on a tangent to the circumference of the log and remaining cuts parallel to the first. This method is the most economical, because it provides the widest boards and results in the least waste. (Since most of the lumber produced by plainsawing is flat- grained, with some vertical-grained wood included, plainsawn lumber will tend to contain more variation within and among boards than quartersawn lumber, in which nearly all of the wood is vertical-grained. Also, since flat-grained wood is less dimensionally stable than vertical-grained, plainsawn lumber will tend to expand and contract more across the width of the boards than quartersawn lumber.) Other physical differences to consider when choosing plainsawn lumber rather than quarter- sawn: Figure patterns resulting from the annual rings and some other types of figures are usually brought out more conspicuously by plainsawing. Shakes and pitch pockets, when present, extend through fewer boards.

PomellePomelle is a type of wood figure that resembles a puddle surface during a light rain: a dense pattern of small rings enveloping one another. Some say this has a "suede" or "furry" look. It's usually found in extremely large trees of African species like sapele, bubinga and makore. Some domestic species with a sparser, larger figure are referred to as "blistered". The term is not used totally reliably and you may encounter some confusion among the terms "blistered", "pomelle", and "quilted" from different vendors

Quartersawn A method of cutting sections of wood perpendicular to the growth rings of a piece of lumber. Another term for quarter sawn is quartered. Quarter-sawn wood may exhibit greater figure and has less pores to absorb moisture, which makes it more dimensionally stable. It also is a less efficient use of wood, more wastage. Much quarter- sawn wood is obtained by culling the vertical-grained wood that naturally results from plainsawing. For reasons other than cost, most people prefer quartersawn wood, although some people favor the greater variety in figuring produced in plainsawing. Other physical factors to keep in mind when choosing quartersawn lumber over plainsawn: It twists and cups less. It surface-checks and splits less during seasoning and in use. Raised grain produced by separation in the annual growth rings does not appear as pronounced. It wears more evenly. Figuring due to pronounced rays, interlocked and wavy grain are brought out more conspicuously. Sapwood appears only at the edges, and is limited to the width of the sapwood in the log.

QuiltedQuilted figure somewhat resembles a larger and exaggerated version of pommele or blister figure but has bulges that are elongated and closely crowded. Quilted grain looks three-dimensional when seen at its billowy best. Most commonly found in maple, it also occurs in mahogany, moabi, myrtle, and sapele, and less often in other species.

Riftsawn Riftsawing is similar to quartersawing, with many of the same advantages and limitations. It accentuates the vertical grain and minimizes the flake effect common in quartersawn oak. The angle of the cut is changed slightly so that fewer saw cuts are parallel to the medullary rays, which are responsible for the flake effect. Riftsawing creates more waste than quartersawing, making it generally more expensive.

Runout Wood that is split with a wedge divides along the weakest part of the wood. When wood is cut by a blade, the wood fibers are torn along the path of the blade. Runout usually occurs in wood cut by a saw blade. Wood that is split with a wedge will be stronger than that cut by a saw blade and is preferable for tonewood. The reason is that in split wood, the wood fibers run all the way through the piece. In wood cut by a saw blade, the wood fibers are cut short by the blade and do not run all the way through the piece of wood. Runout can be detected when planing a piece of wood. Planing against the grain will pull the blade into the wood causing gouges. Visual inspection of the edge of a piece can also show runout where the grain of the wood is not parallel to the edge.

SapwoodSapwood is the softer, younger outer portion of a tree that lies between the cambium (formative layer just under the bark) and the heartwood. It is more permeable, less durable, and usually lighter in color than the heartwood.

Spalted Wood which has, as a result of fungal decay, blackish irregular lines which produce a decorative design. The wood may or may not be functionaliy affected by this.

Tap Tone The sound ones gets when tapping on a board, a quick and easy measurement related to the woods inherent musicality.

Tonewood Wood with the qualities and attributes required for use in musical instruments.

Velocity of Sound The speed at which a material transmits energy. The higher the velocity of sound, the more lively the instrument.

Selecting Wood for Musical Instruments 1) Tonewood Attributes * Free of structural defects * Very strong and stable; glues, bends, & finishes satisfactorally * Lightweight (if possible) * Carries sound well and in a pleasing manner. 2) Selection Guidelines * No knots, worm holes, fungus, rot, cracks, or pitch pockets * Quarter sawn, straight grain, minimal runout * Stiff, both along and across the grain * Properly dried or seasoned * Has a ringing sound (tone) when tapped 3) Evaluation Methods * Visual Inspection * Physical measurements * Sound response Evaluating Tonewoods No one evaluation method is sufficient to choose the best tonewood specimen, especially not a scientific one. Of the three categories of tonewood selection techniques, two depend on experience and personal preferences. Measurement methods will help to narrow the selection to those pieces which meet the physical structural requirements for a musical instrument. The following methods are important for all the woods which make an instrument, however the most important part is the top. Let's talk about #3. Visual Inspection The common grading scale for tonewoods is A, AA, AAA, and AAAA or master grade. This grading scale is used by most retail sellers of tonewoods and is very subjective. There is no industry standard for these grades. Although many of the visual attributes of a piece of tonewood are indicators of structural strength and good tap tone. Grade A is clear of knots, swirls, and holes and has fairly straight grain. It may have uneven color, streaks, and wide apart/uneven grain lines, also called compression. It will probably not be perfectly quarter sawn... Grade AA is somewhere between A and AAA grade. That's real specific, isn't it? Grade AAA has even overall color, even and close grain lines, perfectly quarter sawn along the whole width of the board, with minimal runout. Grain lines will probably be closer than 12 lines per inch. Cross-grain figure, also called silking or bearclaw will be present. Grade AAAA or Master Grade has no color variation and very pronounced cross-grain figuring in addition to being perfectly quartered with minimal runout and close and even grain lines. Physical Measurements Stiffness, both along the grain and across the grain, is the main indicator that a builder uses to determine the dimensions of the soundboard and other parts of a musical instrument. Traditionally, this has been an art taught by master to apprentice. A luthier had to learn the "feel" of the wood and plane and scrape the wood to the correct thickness and to make the bracing to the correct size for the finished instrument. There are now more precise ways than "feel" to measure the strength of tonewood. Precise measurement of tonewood strength can be helpful in deciding the correct thickness and the correct amount of bracing - but not without the knowledge of experienced instrument makers. A general range of thickness of guitar tops is between 0.130" - 0.095". The stiffer a board, the thinner it can be and still be structurally adequate. The same thing applies to bracing. The stiffer the brace wood, the smaller the braces can be and still provide the needed structural support. A general range of brace size is not more than 5/16" wide and not more than 3/4" tall. The thinner soundboard and smaller bracing allows less mass. Less mass in a soundboard translates to a more responsive and louder instrument. It also increases the risk of damage or self-destruction. Note: Measurement can be defined as quantifying something using a standard. Whatever standard is used, it needs to be used consistently throughout the process. The stiffness of a wood beam is measured by how far the beam deflects when a certain amount of pressure is applied to it, or how much pressure must be applied to make the beam deflect a certain distance. A formula has been derived that measures the stiffness. E = P*l^3/4w*t^3*d P = the amount of pressure applied l = the length between supports w = the width of the wood sample t = the thickness of the wood sample d = the distance the sample deflected when pressure was applied

MOE (Modulus of Elasticity) Values of some Tonewoods Species MOE(x10^6 in/lb^2) Weight(lb/ft^3) Top thickness? Redwood 1.34 28 Western Red Cedar 1.11 23 .130" Yellow Cedar 1.42 31 Englemann Spruce 1.3 23 White Spruce 1.43 28 Red Spruce 1.61 28 110" Sitka Spruce 1.57 28 Indian Rosewood 1.78 53 African Mahogany 1.31 32 Ebony 1.43 45 Honduras Mahogany 1.42 30 Brazilean rosewood 1.88 47 Bigleaf Maple 1.45 34 Black Walnut 1.68 38 NOTES: Top Thickness" is a possible safe minimum value. Both red and white spruce are sometimes called Adirondack, but note the difference in MOE. Sound Response This evaluation method is the most subjective and variable. Some luthiers will tune a top to some note like F sharp, others will just listen for a musical sound on the top after it had been joined. Still others will sprinkle glitter or sawdust onto a braced top and vibrate it with a transducer or speaker, see the patterns this makes, and then make adjustments. There is some value to sound response evaluation as a possible last step validation of the other two methods, or as a way to select tonewood for a certain final sound. There are other things that affect tonality in a finished instrument more than tap tone: things like the volume of the body, the size and shape of the sound hole(s), the scale length, location of the bridge,and the size and composition of the strings to name a few. Even the species of wood selected for a top probably has more of an effect on the final sound of an instrument than tap tone. In the end, tap tone methods are at least as variable as musical styles or individual personalities. Regardless, they are fun.

Considerations for the BuildStyle Dreadnaught, Jumbo, Concert, OM, OOO, Parlour.....Cutaway none, Venetian, Florentine.....~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Top Wood type of spruce, cedar or redwood....Top wood finish glossy nitro, lacquer, poly, varnish, French polish...binding at top edges wood, black, white... rosette inlaid with wood, herringbone, spalted wood,; abalone or pearl...pickguard clear, black, tortoise shell~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Body Wood that's why you are looking here - any upcharge?Body wood figure see pictures from luthierBody wood finish glossy nitro, lacquer, poly, varnish, French polishback center stripe none, contrasting wood, same as bindings....body binding wood, black, whitepurfling dittostrap buttons yes, nolining & side braces up to the luthier? back braces up to the luthier?brace under bridge up to the luthier?brace pattern, style up to the luthier?~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Neck Wood mahogany, or ? Single piece, multi-piece neck. Type of finish. Any upcharge? Neck structure D, V, assymetrical...Neck finish ultra smooth, glossy,Headstock vintage style, slotted, luthier's design...Headstock overlay same as back and sides...black, other wood.... inlay on head custom, luthier logoback overlay on headstock often absent trussrod cover hidden, accessed through headstockheadstock binding abalone, black/white, body binding, nonetuners Schaller, Gotoh, Grover.....volute sometimes absentheel bottom cover binding wood, body wood, none...heel shape jazz style, flat, sharp,/ curved....~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ scale many availablenut width many availableNut and saddle ivory, fossiliized bone, man-made....bridge dittofretboard ebony, rosewood......fretboard binding sometimes absent, black, same wood as body bindiing.... fingerboard radiused? yes (usually)fret type profile, metal choseninlay on fretboard none, dots, diamonds, clouds, custom, fancyneck width # frets clear of body 12-14action depends upon your playing style, usually low as low as feasible~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Case soft, Canadian, custom.... Included with the sale or extra?Electronics none, pickup kind, location of controls Warranty for whose life?Price total, installments made when?Delivery included with the sale? Date?Special Requests double top, 12 string, baritone, fan frets, sound port, Manzer wedge....

Janka Hardness Scale The Janka hardness test is a measurement of the force necessary to embed a .444-inch steel ball to half its diameter into a vertically sawn piece of wood. It is an industry standard for gauging the ability of various species to tolerate denting and normal wear, as well as being a good indication of the effort required to either nail or saw the particular wood. The higher the number, the harder the wood. Woods used as tone woods are in bold. There are a couple of woods for which I found more than one figure.

Wood Variety Sorted by HardnessIpe (Lapacho) 3680African Blackwood 3500Macassar Ebony 3220Brazilian Rosewood 3000Bloodwood 2900Osage-Orange 2500Jatoba 2350 Screwbean Mesquite 2335Persimmon 2300Santos Mahogany 2200Dogwood 2150Ohia 2090Purple Heart 2090Bubinga 1980 (2000+?)Jarrah 1910, 2082Hop Hornbeam 1860Purpleheart 1860Pecan 1820Shagbark Hickory 1820Hornbeam 1780Morado 1780Ziracote 1750Apple 1730Paduak 1725Rengas 1720Almond 1700Black Locust 1700Ovankol 1650Wenge 1630Honey Locust 1580Zebrawood 1575Witch Hazel 1530Canarywood 1520Sapele 1500Orientalwood 1480Bastogne Walnut 1460Madrone 1460Rosewood 1450Sugar Maple 1450Hard Maple 1450Cuban Mahogany 1430Tanoak 1400Tamarind 1400Cypress 1375White Oak 1360African Mahogany 1350, 830White Ash 1320Beech 1300Angelique 1290Myrtlewood 1270Yellow Birch 1260Red Oak 1260Vanautu Blackwood 1200Larch 1200Bastogne Walnut 1000-1500English Walnut 1200King Billy Pine 1200?Green Ash 1200PaulowniaTeak (true) 1155Pacific Yew 1150Cocobolo 1136Koa 1110Cascara 1040Southern Magnolia 1020Am. Black Walnut 1010Claro Walnut 950-1000Black Cherry 950Imbuya 950Sourwood 940Eastern Red Cedar 900Hackberry 880Longleaf Pine 875Rock Elm 860Slippery Elm 860Bigleaf Maple 850Black Ash 850Tropical Am Mahogany 845Lacewood 840African Mahogany 830American Elm 830Western Larch 830Red Lauan 825Honduran Mahogany 830Sycamore 770Port Orford Cedar 720Silver Maple 700White Lauan 690Douglas Fir 685Sassafras 630Tamarack 590Northern Catalpa 550American Chestnut 540Yellow Poplar 540Bald Cypress 510Butternut 490Redwood 480Black Willow 420Basswood 410Yellow Buckeye 350Aspen 350

Sorted by Wood Hardness (not all above are sorted)African Mahogany 1350Almond 1700American Black Walnut 1010American Chestnut 540American Elm 830Angelique 1290Apple 1730Aspen 350Bald Cypress 510Basswood 410Bastogne Walnut 1460Beech 1300Bigleaf Maple 850Black Ash 850Black Cherry 950Black Locust 1700Black Willow 420Bloodwood 2900Brazilian Rosewood 3000Bubinga 1980Butternut 490Canarywood 1520Cascara 1040Claro Walnut 950Cuban Mahogany 1430Cypress 1375Dogwood 2150Douglas Fir 685Eastern Red Cedar 900English Walnut 1200Green Ash 1200Hackberry 880Honey Locust 1580Hop Hornbeam 1860Hornbeam 1780Imbuya 950Ipoe (Lapacho) 3640, 3680Jarrah 1910, 2082Jatoba 2350Koa 1110Lacewood 840Larch 1200Longleaf Pine 875Macassar Ebony 3220 (?)Madrone 1460Mesquite 2345Morado 1780Myrtlewood 1270Northern Catalpa 550Ohia 2090Orientalwood 1480Osage-Orange 2500Ovankol 1650Pacific Yew 1150Paduak 1725Pecan 1820Persimmon 2300Port Orford Cedar 720Purpleheart 1860, 2090Red Lauan 825Redwood 480Rock Elm 860Rosewood 1450Santos Mahogany 2200Sapele 1500Sassafras 630Screwbean Mesquite 2335Shagbark Hickory 1820Silver Maple 700Slippery Elm 860Sourwood 940Southern Magnolia 1020Sugar Maple 1450Sycamore 770Tamarack 590Tamarind 1400Tanoak 1400Tropical Am. Mahogany 845Wenge 1630Western Larch 830White Ash 1320White Lauan 690Witch Hazel 1530Yellow Birch 1260Yellow Buckeye 350Yellow Poplar 540Zebrawood 1575

Partly taken from Wood Handbook: Wood as an Engineering Material (Agriculture Handbook 72, Forest Products Laboratory, Forest Service, US Department of Agriculture; revised 1987).

Wood Shrinkage

Wood shrinks most in the direction of the annual growth rings (tangentially), about one-half as much as across the rings (radially), and only slightly along the grain (longitudinally). The combined effects of radial and tangential shrinkage can distort the shape of wood pieces because of the difference in shrinkage and the curvature of the growth rings. Weight, shrinkage, strength and other properties depend on the moisture content of wood. In trees, moisture content may be as much as 200 percent of the weight of wood substance. After harvesting and milling, the wood will be dried to the proper moisture content for its end use. Wood is dimensionally stable when the moisture content is above the fiber saturation point (usually about 30 percent moisture content). Below that, wood changes dimension when it gains or loses moisture.

Different woods exhibit different moisture stability factors, but they generally shrink and swell the most in the direction of the annual growth rings (tangentially), about half as much across the rings (radially) and only slightly along the grain (longitudinally). This means that plainsawn flooring will tend to shrink and swell more in width than quartersawn flooring, and that most flooring will not shrink or swell much in length.

The numbers below reflect the dimensional change coefficient for the various species, measured as tangential shrinkage or swelling within normal moisture content limits of 6-14 percent. Tangential change values will normally reflect changes in plainsawn wood. Quartersawn wood will usually be more dimensionally stable than plainsawn.

The dimensional change coefficient can be used to calculate expected shrinkage or swelling. Simply multiply the change in moisture content by the change coefficient, then multiply by the width of the board. Example: A mesquite board (change coefficient = .00129) 5 inches wide experiences a moisture content change from 6 to 9 percent a change of 3 percentage points. In actual practice, however, change may be diminished as the boards proximity to each other tends to restrain movement.

Calculation: 3 x .00129 = .00387 x 5 = .019 inches.

.00411 Hickory.00396 Jarrah.00369 Red Oak.00365 White Oak.00353 Maple.00338 Yellow Birch.00300 Jatoba.00274 Ash.00274 Walnut.00267 Douglas Fir.00248 Cherry.00238 Santos mahogany.00212 Purpleheart.00201 Wenge.00162 Cypress.00124 Mesquite

From Jan Arts Guitars: Why Some Woods Are Best for Tops http://janartsguitars.com/joomla/

The table below shows calculated properties of resonating plates which have different wood properties but similar resonance frequencies. The calculations are based on the equation for the resonance frequency of an oscillating plate.

For two plates 1 and 2 assuming equal resonance frequency f and length dimension: h2 = ((Ex1 d2)/(Ex2 d1))0.5 h1 where h= thickness of plate, d=density, E = Modulus of Elasticity

The columns h2/h and w2/w compare thicknesses and mass of plates relative to a sitka spruce plate which has the same resonance frequency. Last column shows ratio between speed of sound (c) and density. The higher this value the more responsive the wood as top.

The table explains why the spruces and Western Red Cedar are good choices for the top and Indian rosewood, kauri and rimu are not so good for a top. The weight of a rimu or kauri top would be double the weight of a spruce top of the same resonance frequency. This would result in lower volume of sound and less response for higher frequencies. Reducing the thickness and adapting the bracing may be a solution. Western Red Cedar looks good for building instruments producing a big sound. The table doesn't say anything about bracing or damping properties. Individual properties of samples show big variations. Cedar is associated with a warm tone. This could be related to a quicker dissipation (more damping) of higher frequencies or a weaker fundamental associated with a relative low density (nice little research topic). Graphite is included in the table because it can be useful in combination with lighter materials like balsa wood. Balsa by itself is probably not strong enough to take the tension and the low mass is likely to result in a low sustain as well. Sitka and Port Orford Cedar (is actually not a cedar but cypress) are tougher than Engelmann Spruce and Western Red Cedar. This property may make it possible to make a thinner top, which results in a lower resonance frequency. A resonance frequency can be increased if desired by using stiffer bracing and/or increasing the dome shape of the top. Species Mod. of Elasticity Density d E/d h2/h w2w c/d E (// grain) *1010 kg/m3 (N/m2)Sitka Spruce 1.1 379 29 1.0 1.0 1.4 .99 360 28Western Red Cedar 1.09 320 34.1 .92 .72 18 .77 320 24 1.09 .92 15 .82 368 22 1.14 1.11 12.7Englemann Spruce .89 350 25 1.07 .99 14Port Orford Cedar 1.34 470 29 1.0 1.24 11 .9 430 21 1.17 1.32 1.2 484 25 1.08 1.37 10.3Bunya 1.3 460 28 1.02 1.23 1105 (?)Brazilian Mahogany 1.33 537 24.8 1.08 1.5 9.3Big Leaf Maple .76 440 17 1.31 1.52 9.4Sapele 1.03 550 19 1.23 1.78 7.9Australian Blackwood 1.3 640 20.0 1.2 2.0 7Red Beech 1.16 650 17.8 1.27 2.5 6.4Kauri .91 560 16 1.34 1.98 7.1Rimu .96 595 16 1.34 2.10 6.7Koa 1.05 670 15.8 1.36 2.4 5.9Indian Rosewood 1.01 797 12.6 1.51 3.1 4.4 And, for fun and gamesGraphite 6.89 1800 38 4.1 2.48 3.4Balsa .34 160 21 1.18 .5 29

Comparative Data: Some woods Used for Stringed InstrumentsCommon Name Specific Gravity Tangential Shrinkage Radial Shrinkage Radial/ Tangential African Blackwood 1.22 Alaska Yellow Cedar .44 6.0 2.8 2.1Koa .60 6.2 5.5 1.1 Black Walnut .55 7.8 5.5 1.4Myrtle or California Laurel .55 Bigleaf Maple .48 Sitka Spruce .40 7.5 4.3 1.7Honduras Mahogany .40 5.1 3.7 1.4Indian Rosewood .76 Engelmann Spruce .34 7.1 3.8 1.9Eastern Spruce .40 7.8 3.8 2.1Western Red cedar .33 5.0 2.4 2.1Redwood .40 4.4 2.6 1.7

Top Wood Ranking from Tim McKnight www.mcknightguitars.comBelow you can find a chart with a "ranking" of most common wood species for tops, arranged from the most flexible to the stiffest species.

Common Name Botanical Name Ave. Weight Deflection weak -> stiffCedar thuja plicata 185.0 grams .096"Douglas Fir pseudotsuga menziesii 215.5 grams .090"Redwood sequoia sempervirens 200.0 grams .090"Engelmann Spruce picea engelmannii 195.0 grams .089"Caucasian Spruce picea orientalis 214.0 grams .088"New Sitka Spruce picea sitchensis 215.0 grams .081"Lutz Spruce (Sitka /White hybrid) picea X lutzi Little 219.5 grams .070"1959 Sitka Spruce picea sitchensis 226.5 grams .064"Red (Adk) Spruce picea rubens 238.5 grams .063"European Spruce picea abiens 233.5 grams .062"

Support Sound Ports

A "sound port" is a hole in the guitar's upper bout that allows the performer to hear it better but seemingly does nothing to hinder the sound the audience hears. I have seen them on quite a few custom guitars but not on any manufactured ones; that'll come. It sounds radical, but isn't. I did a test once with a guitar that had one. We'd cover up the sound port with a piece of paper and I'd play, then we'd open it and I'd play the same things, the same way. Each person listening said they could tell no difference. But there was a large difference to me, MUCH louder and clearer to my ears. I was really impressed and had come into the experiment with a definite bias, fully expecting to hate the concept.

Wanting to see if it was just me or if this was real, I did some research on the internet and found this:

" When you play a standard acoustic guitar, you never hear the true sound that the guitar is producing. Why? Because what you hear is reflected sound. Have you asked someone to play a guitar for you, so you can hear it? Maybe you have played a guitar in a corner, or close to a wall, so you can hear it more clearly. Do you find yourself leaning over the side of the guitar, or angling the guitar upward, so your ear is more in line with the sound hole? Now, with the benefit of a Sound Port, you can hear the true sound your guitar is producing. The sound port directs a portion of the guitars true sound to the player. The results are truly amazing! It is like having your very own personal sound monitor built into your guitar.

Blindfold tests prove that there is absolutely no loss of energy with a sound port. In fact, the results are quite the opposite. There is a discernable gain in sound hole projection, as well as a 360 degree sound gain around the player...9/23/2006 - Some preliminary testing -I was reading a thread on the internet recently and someone quoted me that 'sound ports increased frontal projection'. However, the poster mentioned that they could not believe my statement because I had no scientific data to back up my statement. Well, they were correct because I did not have any data to offer scientific proof other than the gray matter residing on top of my shoulders. This piqued my interest and motivated me to set out to run some controlled experiments to prove or disprove my gut instincts.

I borrowed a Metrosonics db307 Noise Dosimeter from a local lab and set out to run a few DOE's. I enlisted the help of a local musician to consistently strum open strings (without a pick) as I measured the decibel levels at different locations around two guitars, at different distances. The room we used is our 'Studio Loft' located above our work shop. The room is 16 feet wide x 26 feet long with 7 foot ceilings. The room has hardwood floors, textured drywall on the ceiling and walls. A center rug, numerous bass traps and acoustic panels are strategically placed around the room and in all corners to control reflective noise.

The following should also be prefaced by first saying this was not a lab quality double blind test nor were fixtures used to eliminate the human element from the tests. I only had a few hours available to borrow the meter so I did the best that I could with what little time I had. We used two guitars for this experiment: a Honduras Mahogany / Adi with an oval shaped sound port, on the upper bout side, which shall henceforth be referred to as guitar A, and a Cuban Mahogany / Cedar with a Luckenbooth sound port which shall be referred to as guitar B....

Guitar A was first measured with the sound port closed with a sponge (RV - I wonder how good an idea the sponge was. It seems it would absorg=b sound rather than refleclt it the way hard body wood would do.) and the instrument's microphone was placed 6" in front of the sound hole. Brad strummed the guitar in 4/4 time until we had a relatively steady display on the Dosimeter and then I snapped a picture to capture the data. Three pictures were taken to record three separate measurements at each position and then the measurements were compared on the digital pictures for accuracy. After we reviewed the pictures we found that the measurements had a total range of no more than .2 db for all the tests that we ran. This position measured 84.6 db. I removed the sponge from the oval sound port and measured the volume again and we recorded 84.8 db. A small increase of .2 db.

Next the mic was moved 6" above the sound port and we measured the sound level the player normally hears with NO sound port and it measured 71.1 db. We then uncovered the port and measured an amazing 89.5 db emitted form the port. That is a 4.9 db gain at the port over and above the sound hole volume output.Next we measured guitar B, first at the sound hole with the port closed and we recorded 88.6 db. The port was then uncovered and we measured a gain of 1.1 db or 89.7. We then measured the sound at the port with the port closed to replicate what a player would hear without a port and measured 74.3 db. The port was then uncovered and we measured an astounding 98.6 db or a whopping 10 db gain over the volume of the sound hole output!

This was shocking since this guitar had the *** port and I thought the volume was actually less than an oval or pic shape port. Hmmm, I was surprised by the data on that one.

Next I had Brad set in the middle of our studio sound room and continue his 4/4 strumming on guitar B while the port was left open. I measured the sound volume level at four different points, six feet away from him. The first measurement was taken directly in front of the sound hole and it measured 72 db. I walked towards the neck and measured 68 db. Next I stood directly behind him and measured 70 db. The last measurement was recorded at the tail end of the guitar and this measurement was 74 db, ... louder than the frontal measurement. This was a bit puzzling so I had him cover the port and the db level dropped to 69 db. We concluded that this was the area that produced the most stereo effect of the sound hole combined with the sound port because this was the direction the port was facing towards.

Since we proved that there was a quantifiable and measurable gain in frontal projection on both guitars with the sound port open I wanted to find out what effect there was at longer distances. We measured 10 feet from the sound hole and measured 82.1 and 83.5 with the port closed and then open. Next we measured the volume at 20 feet and recorded 68.3 and 69.9 db with the port closed and then opened.

So there you have it folks, for what it its worth ??? I am not a scientist and I am sure someone will challenge my results but this is the best that this ole' boy can do. Now, back to makin' sawdust."

I talked with JJ Donahue, who also believes guitars are louder with sound ports. His theory: the open port allows air to flow through. Like speaking into a bottle, the sound gets muffled. But in a guitar, the sound is coming from within and projecting outwards. Is it the same? I am not sure of that, but do feel confidant that with a sound port you find it easier to hear yourself play, and the audience will not notice a difference.

Toxicity in WoodsThese, among others, were listed as having first appeared in American Woodturner , June 1990. Very likely there are other that should be on this list, Butternut for instance, which is supposed to be far worse than its cousin Walnut. Note the legend at the bottom. Wood Reaction Site Potency Source Incidence Bald Cypress S R + D R Birch S R ++ W,D C Black Locust I,N E,S +++ LB C Blackwood S E,S ++ W,D C Boxwood S E,S ++ W,D C Cocobolo I,S E,S,R +++ W,D C Ebony I,S E,S ++ W,D C Elm I E,S + D R Goncalo Alves S E,S ++ W,D R Mahogany S,P S,R + D U Maple (Spalted) S,P R +++ D C Myrtle S R ++ LB,D C Oak S E,S ++ LB,D R C ? D U Olivewood I,S E,S,R +++ W,D C Padauk S E,S,R + W,D R Pau Ferro S E,S + W,D R Purpleheart N ++ W,D C Redwood S,P E,S,R ++ D R C ? D U Rosewoods I,S E,S,R ++++ W,D U Satinwood I E,S,R +++ W,D C Sassafras S R + D C DT N + D,W,LB R C ? D U Snakewood I R ++ W,D R Spruce S R + W,D R Walnut, Black S E,S ++ W,D C Wenge S E,S,R + W,D C West. Red Cedar S R +++ D,LB C Yew I E,S ++ D C DT N,C ++++ W,D C Zebrawood S E,S ++ W,D

REACTION: SITE: SOURCE: INCIDENCE: I - irritant S - skin D - dust R - rare S - sensitizer E - eyes LB - leaves,bark C - common C - nasopharyngeal R - respiratory W - wood U - uncommon cancer P - pheumonitis, C - cardiac alveolitis (hypersensitivity pneumonia) DT - direct toxin N - nausea, malaise

Bending of Alternative Woods (from "Forgotten Woods")

Bending Tests Shaping and Bending

Working with our woods for the flat surfaces of soundboards and backboards is a rather straight-forward task, but not all woods can be shaped and bent with equal ease and results when preparing instrument rims (ribs), especially where acute bends for cutaways and similar tight curves are concerned.

To analyze the bending and shaping attributes of our woods, we enlisted the aid of Roger Siminoff, author of "The Luthier's Handbook" and luthierie consultant in Atascadero, California, who performed tests using several techniques. Complex bends were performed in a fixture that shaped the wood into a tight "S" curve. Each section of the "S" was formed around a 2" diameter post. While the radius of these bends is more extreme than those used for guitars, we wanted to provide you with information about shaping and bending our woods under the most extreme conditions.

For our tests, we considered how difficult it was to bend the wood, how much the wood sheared (checked), and how easily it cracked (if at all). The smoothness of the bend was an important consideration in our tests. This sample piece bent beautifully and easily with smooth bends and curves.The Tests - what was evaluated:

Ease of bending: Each wood was graded on a scale of A-F based on how easily it bent from a standpoint of how much effort was applied to force the wood into a bend. (This is not to be confused with how satisfactory the bend was.) If the wood bent easily with very little effort or force, it was graded as "A". If the wood was very resistant to bending, it was graded as "F". The relative bending force speaks to the density, elasticity, resistance to bending, and overall strength of the wood.

Propensity to shear or check: Each wood was graded on a scale of A-F based on its propensity to shear or check. Aluminum bands were used on both sides of the wood to help form the wood into the bend. The aluminum bands were prepared to be 1/8" narrower than the wood to test how the exposed edge of the wood would react to being bent without support. If the wood had good structural integrity, and no edge tearing (shearing) occurred, it would be graded as "A". If the wood had poor structural integrity, and edge tearing was excessive, it would be graded as "F".

Propensity to crack: Each wood was graded on scale of A-F based on its propensity to crack across grain. If the wood bent with smooth, clean, flowing bends it was graded as an "A". If the wood presented small steps or erratic bends, it was graded as an "F". Wood that cracked immediately was graded as an "X". (Notes: 1-This does not suggest that the wood cannot be bent in curves with a larger radius or that it cannot be coaxed with more heat or a greater concentration of heat. 2- Woods rated "X" for cracking might best be used for flatted areas such as soundboards and backboards and not for ribs. Please contact us if you would like to purchase a small sample to test with your own bending methods.)

Curvature (smoothness) of bend: The shape and evenness of the curvature is very important. Each wood was graded on a scale of A-F based on how satisfactory the bend was. Bends that were very smooth, clean, and well shaped were graded as an "A". Bends that were erratic and not well shaped were graded as an "F".

Grain bias (preparation): Typically, woods bend more easily when the grain is flat (parallel to the wide side of the piece). Grain that is quartered or that runs across the piece imposes greater difficulty in bending. Most dense hardwoods can be bent well in both directions because the density and stiffness of the wood is more similar both across and through the annular rings. Our tests did not take grain direction into consideration and the pieces were prepared primarily in the vertical grain, quarter-sawn method.

Bending method: The wood was wetted for 5 minutes before being bent and we used steam as the heating and wetting agent. Steam at 216 was applied directly to the wood during the bending process from a hose, with an aggressive blast of steam coming from the steam chamber at 40psi. Steam was applied globally for 10 seconds and then directed at the bending location as the fixture was forming the wood into a bend. Table of Results

Common Name Species Name Ease Shear Crack Curvature Higuerilla Micandra spruceana A+ A A A Cachimbo Cariniana domesticata A+ A A A Manchinga Brosimun alicastrum A+ B A A Achihua Huberodendom swietenoides D D C C Ishpingo Amburana cearensis A+ A+ A+ A+ Pumaquiro Aspidosperma macrocarpon C C A B Requia Guarea guidonea A A A A Pashaco Amarillo Schizalobium sp X Tornillo Cedralinga catenaeformis A+ A A A Isigo Couratari sp. C C A A Copaiba Copaifera officinallis A A A A Pashaco Negro Schizolobium parahybum C B D D Mango Manguifera indica A+ A A A+ Catahua Hura crepitans C A- A A- Peruvian Walnut Juglans neotropica A+ A A A Shihuahuaco Dipteryx micranta C A A A Quillabordon Aspidosperma subincamum F A A A Estoraque Myroxylon balsamun A+ B B A Caprirona Callycophylum spruceanum D C A A- Moena Amarillo Aniba amazonica D A A B Panguana Brosimun utile X Tigrillo Amburana cearensis A A A A Hymiwood species unknown A+ A+ A A+ A perfect bend on Higuerilla.

Frequency of Woods

Relative Stability of Selected Woods