Contemporary Acoustic Guitar by Trevor Gore and Gerard Gilet

These two books by Australian physicist Trevor Gore and luthier Gerard Gilet contain the most authoritative and comprehensive information available on how guitars work, and how to build them.

Contemporary Acoustic Guitar Design and Build: Volume 1: Design Contemporary Acoustic Guitar Design and Build: Volume 2: Build
Contemporary Acoustic Guitar Design and Build: Volume 1: Design and Volume 2: Build, by Trevor Gore with Gerard Gilet.

The two volumes together provide a theoretical background and practical foundation for the design and construction of acoustic guitars with more than 800 pages and over 1200 detailed photos and illustrations.

Contemporary Acoustic Guitar Design and Build: Volume 1: Design
Expect heavy physics and maths in volume 1. Trevor Gore is a physicist and he worked with Gerard Gilet for 15 years to produce these two volumes. (Excerpt from Volume 1: Design.)

Contemporary Acoustic Guitar Design and Build: Volume 1: Design
A graph showing the response of a popular brand of classical guitar strings. (Excerpt from Volume 1: Design)

Contemporary Acoustic Guitar Design and Build: Volume 1: Design
Frequency patterns of the soundboard of a guitar (Excerpt from Volume 1: Design)

Contemporary Acoustic Guitar Design and Build: Volume 1: Design
Diagram showing the 'system' of an acoustic guitar (Excerpt from Volume 1: Design)

Contemporary Acoustic Guitar Design and Build: Volume 1: Design
Gerard Gilet, master luthier.

Contemporary Acoustic Guitar Design and Build: Volume 1: Design
Excerpt from Volume 2: Build.

Contemporary Acoustic Guitar Design and Build: Volume 1: Design
Excerpt from Volume 2: Build.

Contemporary Acoustic Guitar Design and Build: Volume 1: Design
Excerpt from Volume 2: Build.

Volume 1: Design: Table of Contents
Introduction
1. Principles of Vibration and Acoustics for Guitar Designers ... 1-1
1.1. Sound and How We Hear... 1-2
1.1.1. What is sound? ... 1-2
1.1.2. The ear ... 1-6
1.1.2.1. The anatomy of the ear... 1-6
1.1.2.2. Roughness ... 1-9
1.1.2.3. Masking ... 1-12
1.1.3. Consequences for guitar designers of how we hear... 1-15
1.1.4. Section summary ... 1-16
1.2. Simple harmonic motion ... 1-18
1.2.1. Mathematical definition of simple harmonic motion ... 1-18
1.2.2. Geometrical model of simple harmonic motion... 1-18
1.2.3. The period of simple harmonic motion ... 1-19
1.2.4. An example of simple harmonic motion ... 1-19
1.2.5. The energy embodied in simple harmonic motion... 1-22
1.3. Introduction to the mechanics of beams ... 1-25
1.3.1. Stiffness of simple beams ... 1-25
1.3.2. The mass of a simple beam... 1-26
1.3.3. Vibrating systems ... 1-26
1.4. Resonance and vibration sensitivity ... 1-28
1.4.1. Simple resonators... 1-28
1.4.2. The Helmholtz resonator... 1-30
1.4.3. Damped simple resonators... 1-32
1.4.4. Driven, damped simple resonators – strings driving soundboards ... 1-33
1.4.5. The detailed behaviour of a simple driven resonator ... 1-39
1.4.6. The Q-Factor... 1-42
1.4.7. Mechanical Impedance ... 1-44
1.4.8. Impedance (mis)matching ...1-45
1.4.9. Impedance, admittance and the high performance guitar ... 1-46
1.4.10. Beats ... 1-48
1.5. Vibrations in strings and the forces they exert... 1-50
1.5.1. Types of waves in strings – frame of reference ... 1-50
1.5.2. Transverse waves in strings ... 1-51
1.5.3. Wave partials and harmonicity ... 1-52
1.5.4. Waves in “ideal” strings... 1-53
1.5.5. Forces on the terminations of an ideal string ... 1-54
1.5.6. Real strings ... 1-58
1.5.7. Plucking at places other than the centre ... 1-60
1.5.8. Forces exerted by a string on a soundboard ... 1-63
1.5.9. Strings with bending stiffness... 1-66
1.5.10. Section summary ... 1-71
1.6. Introduction to vibrations of bars and plates – strings driving soundboards ... 1-72
1.6.1. Vibrations of bars ... 1-72
1.6.2. Vibrations of plates with free edges... 1-73
1.6.3. Vibrations of flat plates fixed around their edges... 1-74
1.6.4. Guitar vibration modes excited by the string forces ... 1-76
1.6.5. Vibrations of curved plates (spherical shells) ... 1-78
1.7. Sound radiation from a guitar ... 1-81
1.7.1. How sound is radiated by a guitar ... 1-81
1.7.2. Monopole sound radiation and specific mobility ... 1-89
1.7.3. Monopole mobility and the frequency response curve ... 1-91
1.7.4. The anatomy of a plucked note... 1-92
1.7.5. Sound radiation from the guitar cavity at middle frequencies... 1-93
1.7.6. Sound radiation and directivity ... 1-95
1.7.7. Chapter Summary ...1-100
2. Analytical Guitar Models and their Use ... 2-2
2.1. Coupled resonators and simple low frequency guitar models ... 2-2
2.2. Coupled resonators... 2-3
2.2.1. Two mass coupled resonator ... 2-4
2.3. 2-DOF model of a guitar’s low frequency response ... 2-8
2.3.1. Low frequency response of a guitar with a stiff back ... 2-8
2.3.2. Two mass coupled resonator model for guitars ... 2-10
2.3.3. Using the 2-DOF model to determine fh ... 2-13
2.3.4. Direct determination of the Helmholtz frequency... 2-14
2.3.5. Use of the 2-DOF model in the workshop ... 2-15
2.3.6. Using the 2-DOF model for guitars with live backs... 2-17
2.3.7. Some unusual features of guitar shaped cavities... 2-17
2.3.8. “Live back” guitar low frequency response ... 2-18
2.3.9. Coupled top plate and back plate guitar model ... 2-19
2.3.10. Target values for the main top and main air resonances ... 2-24
2.3.11. Investigative modelling – working in the frequency domain ... 2-25
2.3.12. Empirical adjustment of plate frequencies ... 2-26
2.3.12.1. Top response to small perturbations in mass... 2-27
2.3.12.2. Guitar response to side mass ... 2-28
2.4. Simulation of a guitar’s frequency response ... 2-31
2.4.1. A 4-DOF model of low frequency guitar function ... 2-32
2.4.1.1. 4-DOF model sensitivity analysis ... 2-38
2.4.1.2. 4-DOF model and “live” backs ... 2-40
2.4.2. The behaviour of superimposed simple sound sources ... 2-42
2.4.3. Combining the 4-DOF model with superimposed simple sources... 2-46
2.5. Coupling of strings to soundboards ... 2-50
2.6. Chapter Summary ... 2-51
3. The Design Objective - The Perfect Guitar ... 3-2
3.1. Playability ... 3-2
3.1.1. Plucking hand feel ... 3-3
3.1.2. Fretting hand feel ... 3-4
3.1.2.1. Scale length ... 3-4
3.1.2.2. Tuneability ... 3-5
3.1.2.3. Action... 3-6
3.1.2.4. String height at the nut... 3-9
3.1.2.5. Relief... 3-9
3.1.2.6. Fretboard curvature... 3-11
3.1.2.7. Neck profile/nut width... 3-12
3.1.2.8. Frets ... 3-13
3.1.2.9. Neck finish ... 3-14
3.1.2.10. Neck to body joint position; cutaways ... 3-14
3.1.2.11. Number of frets ... 3-15
3.2. Musicality... 3-15
3.2.1. Consonance and dissonance... 3-15
3.2.1.1. Experimental demonstration of consonance and dissonance ... 3-16
3.2.1.2. The consonance of intervals... 3-17
3.2.1.3. A brief history of scales ... 3-19
3.2.1.4. The tuning gap (between what you
tune to and what you’d like to hear).. 3-21
3.2.1.5. The tuning error (between what you tune to and what your guitar plays). 3-22
3.2.1.6. Achieving pitch accuracy ... 3-23
3.2.1.7. Dealing with inharmonicity ... 3-23
3.2.2. The acoustic response characteristics of a guitar... 3-23
3.2.2.1. A perfect frequency response? ... 3-24
3.2.2.2. Guitar performance factors: “Volume and tone”... 3-29
3.2.2.3. Nomenclature ... 3-29
3.2.2.4. Tonal qualities of a Dreadnought guitar used for flat picking... 3-33
3.2.2.5. Tonal qualities of a steel string guitar for finger style playing ... 3-35
3.2.2.6. Tonal qualities of a classical guitar... 3-36
3.2.2.7. Tonal qualities of a flamenco guitar (flamenco blanca)... 3-38
4. Component Design ... 4-2
4.1. Wood as an organic material... 4-2
4.1.1. The composition of wood ... 4-3
4.1.2. The annual cycle ... 4-5
4.1.3. Dealing with moisture ... 4-5
4.1.4. Dealing with runout ... 4-9
4.1.5. Storing wood ...4-11
4.2. Guitar woods ...4-12
4.2.1. Top woods ...4-13
4.2.2. Back and side woods...4-14
4.2.3. Neck woods ...4-15
4.2.4. Brace woods ...4-15
4.2.5. Fretboard woods...4-16
4.2.6. Bridge woods ...4-17
4.2.7. Woods for other components...4-17
4.3. Wood properties that matter...4-18
4.3.1. The sound radiation coefficient ...4-18
4.3.2. The damping factor...4-20
4.3.3. Measuring wood properties ...4-21
4.3.3.1. Measurement of Q ...4-21
4.3.3.2. Measurement of logarithmic decrement ...4-23
4.3.3.3. Potential difficulties ...4-26
4.3.3.4. Long grain damping vs. cross grain damping...4-28
4.3.3.5. Tap testing for “Q” ...4-29
4.3.4. Conditioning wood ...4-29
4.3.5. Section summary ...4-30
4.4. Design of braces and bracing systems...4-31
4.4.1. Bending stiffness ...4-31
4.4.2. Brace design criteria ...4-32
4.4.3. Calculating the second moment of area of a brace ...4-35
4.4.4. Measurement of Young’s modulus E for brace material ...4-38
4.4.5. Determination of soundboard flexural rigidity ...4-40
4.4.6. Carbon fibre reinforced braces...4-45
4.4.6.1. Designing Composite Braces ...4-46
4.4.6.2. Balancing brace stiffness to panel stiffness ...4-48
4.4.7. Stress limits for braces...4-48
4.4.8. Top bracing layout - guidelines ...4-52
4.4.9. Back bracing ...4-52
4.4.10. Section summary ...4-53
4.5. Design of plates ...4-55
4.5.1. Waves in plates ...4-55
4.5.2. The tap tone method of establishing wood properties ...4-57
4.5.3. Establishing the target plate thickness...4-60
4.5.4. Sensitivity to long and cross grain stiffness variations...4-64
4.5.5. Panel design decisions...4-64
4.5.6. Chapter summary...4-65
4.6. Body shapes and the design of other components...4-66
4.6.1. Bridge design...4-66
4.6.1.1. The bridge as a distributor of string loading ...4-66
4.6.1.2. Positioning the bridge on X-braced guitars ...4-66
4.6.1.3. Bridge mass and stiffness...4-68
4.6.1.4. Steel string bridge planform ...4-69
4.6.1.5. The bridge plate...4-71
4.6.1.6. Classical guitar bridges ...4-71
4.6.2. Linings ...4-73
4.6.3. End blocks ...4-73
4.6.4. Cutaways ...4-73
4.6.5. Neck joint...4-74
4.6.6. Fretboard - fret spacing...4-77
4.6.7. Neck cross sectional shape ...4-77
4.6.8. Truss rods ...4-80
4.6.9. The nut ...4-81
4.6.10. Headstock...4-82
4.6.11. Body shape...4-84
4.6.11.1. Size and shape ...4-84
4.6.11.2. Body shape proportions ...4-87
4.6.11.3. Designing body shapes ...4-88
4.6.12. Section summary ...4-90
4.7. Intonation...4-91
4.7.1. A first source of intonation error ...4-91
4.7.2. A second source of intonation error ...4-93
4.7.2.1. Fixing intonation errors due to body resonances ...4-93
4.7.2.2. Resonance shifting ...4-93
4.7.2.3. Empirical nut and saddle intonation ...4-95
4.7.2.4. A simple intonation fix ...4-98
4.7.3. Intonation for a high performance guitar ...4-99
4.7.3.1. Measuring a string’s longitudinal stiffness ...4-99
4.7.3.2. Calculating the change in path length as the string is fretted...4-103
4.7.3.3. The effect of string bending stiffness on intonation error...4-111
4.7.4. Compensation without most of the mathematics ...4-112
4.7.5. Section summary ...4-113
5. Layout Procedure... 5-2
5.1. Drafting the layout of a steel string guitar ... 5-2
5.2. Drafting the layout of a classical guitar... 5-5
5.3. Section summary ... 5-6
AI 1. Technical note on collecting spectrographic data... AI 1
AI 2. Using Chladni’s technique to visualise vibration modes ... AI 3
AII 1. Deflection of the soundboard under oscillating longitudinal string forces ... AII 1
AII 2. 4 Degree of Freedom model of low frequency guitar function ... AII 5
AII 3. Fretboard Curvature ... AII 11
AIII 1. Frequency look-up table ... AIII 1
AIV 1.Bending waves on plates ... AIV 1

Vol 2: Build Table of Contents
1.Introduction... 1-2
2.A Brief Review of Assembly Systems .... 2-2
2.1.Free Assembly Methods ... 2-3
2.2.Constrained Assembly Methods ... 2-4
3.Our Approach to Building ... 3-2
3.1.Our Building System... 3-2
3.1.1.The Outside Mould... 3-5
3.1.2.The Use of Dishes and Go-Bar Decks.... 3-6
3.1.3.The Bolt-On Neck ... 3-7
4. Workshop, Tools, Equipment and Jigs... 4-2
4.1. The Workshop and Humidity Control ... 4-2
4.2. Stationary Machinery... 4-4
4.3. Hand Power Tools ... 4-5
4.4. Hand Edge Tools... 4-5
4.4.1. Standard Bench Planes ... 4-7
4.4.2. Block Planes ... 4-9
4.4.3. Finger Planes ... 4-10
4.4.4. High Angle Planes ... 4-10
4.4.5. Shaves... 4-10
4.4.6. Scrapers ... 4-11
4.4.7. Chisels ... 4-11
4.4.8. Saws ... 4-13
4.4.9. Rasps and Files ... 4-13
4.5. Sharpening Tools and Process... 4-13
4.6. Measuring Instruments and Marking Tools ... 4-16
4.7. Clamps... 4-16
4.7.1. Spring Clamps ... 4-16
4.7.2. F - Clamps... 4-16
4.7.3. G – Clamps... 4-16
4.7.4. Instrument Maker’s Clamps.... 4-17
4.7.5. Trigger Action Clamps ... 4-17
4.7.6. Parallel Screw Clamps ... 4-17
4.8. Special Tooling, Fixtures And Jigs ... 4-17
4.8.1. Body Shape Template ... 4-17
4.8.2. Body Mould ... 4-19
4.8.3. Go-Bar Deck ... 4-25
4.8.4. Dished Work Boards... 4-26
4.8.5. Side Bending Equipment... 4-29
4.8.6. Binding Ledge Routing Machine ... 4-35
4.8.7. Panel Joining Fixture ... 4-40
4.8.8. Bench Accessories... 4-40
4.8.8.1. Bench Hooks ... 4-40
4.8.8.2. Shooting Board ... 4-40
4.8.8.3. Panel Planing Board ... 4-43
4.8.8.4. Thickness Gauge ... 4-43
4.8.8.5. Neck Carving Horse ... 4-43
4.8.9. Routing Aids ... 4-43
4.8.9.1. A Custom Fence for Routing Bridges... 4-45
4.8.9.2. A Trammelling Router
Base for Circle Cutting ... 4-45
4.8.9.3. A Simple Router Table.... 4-45
4.8.9.4. Rectangular Work Board... 4-45
4.8.9.5. Bridge Routing Jig ... 4-47
4.8.9.6. Body Mortise Routing Fixture ... 4-47
4.8.9.7. Brace Bottom Curve Routing Fixture... 4-49
4.8.10. Neck Bolt Drilling Jig ...4-49
4.8.11. Neck Tapering Fixture ... 4-49
4.8.12. Classical Headstock Barrel Boring Jig ... 4-49
4.8.13. Fretboard Caul ... 4-50
4.8.14. String Spacing Tool for Nut Layouts... 4-51
4.9. A Note on General Gluing Practice ... 4-52
5.The Neck... 5-2
5.1.Building the Neck Blank ... 5-4
5.2.Cutting the Neck Tenon ... 5-9
5.2.1.Marking Out ... 5-9
5.2.2.Making the Cuts ... 5-11
6.Thicknessing and Joining the Panels ... 6-2
6.1.Squaring and Surfacing the Panels ... 6-2
6.2.Tap Testing the Panels... 6-7
6.3.Joining the Panels ... 6-8
6.3.1.Shooting the Edges ... 6-8
6.3.2.Joining the Panels ... 6-10
6.4.Rosette Making... 6-11
6.4.1.A Traditional Rosette for a Steel String Guitar ... 6-11
6.4.1.1. Making the Rosette Former .... 6-11
6.4.1.2. Squaring the Ends of the Shell Segments... 6-11
6.4.1.3. Assembling the Shell Ring ... 6-13
6.4.1.4. Inlaying the Rosette into the Sound Board ... 6-15
6.4.1.5. Levelling the Rosette ... 6-20
6.4.2.A Contemporary Rosette for Steel String or Classical Guitar... 6-20
6.4.2.1. Producing a Burl Slice .... 6-20
6.4.2.2. Routing the Rosette Blank ... 6-23
6.4.2.3. Inlaying the Rosette into the Sound Board ... 6-23
6.5.Final Thicknessing... 6-27
6.6.Sound Hole Reinforcement Patch.... 6-29
6.6.1.Assembling and Shaping the Patch Blank .... 6-29
6.6.2.Gluing Down the Sound Hole Patch .... 6-29
6.7.Cutting Out the Sound Hole... 6-31
6.7.1.Tapering the Inside Edge of the Sound Hole ... 6-31
6.8.Thicknessing the Sides ... 6-33
7.Making Braces... 7-2
7.1.Preparing Back Braces and Conventional X-Braces for Tops ... 7-2
7.1.1.Machining the Curve on the Base of the Brace ... 7-4
7.1.1.1. Router Method ... 7-4
7.1.1.2. Hand Tool Method ... 7-6
7.2.Making Lattice Bracing... 7-6
7.3.Making Falcate Braces ... 7-9
7.3.1.Preparing the Laminates... 7-9
7.3.2.Bending the Laminates... 7-10
7.3.3.Trimming the Braces to Size ... 7-12
7.3.4.Tertiary Braces and Sound Hole Bracing ... 12
7.3.5.Upper Face Brace ... 12
7.3.6.The Bridge Plate... 12
8.Bending the Sides... 8-2
8.1.Using a Bending Iron... 8-4
8.2.Using a Side Bending Machine ... 8-6
8.3.Bending a Venetian Cutaway ... 8-8
8.4.Fitting the Sides to the Mould ... 8-12
8.4.1.For a Non-Cutaway Guitar ... 8-12
8.4.2.For a Cutaway Guitar ... 8-12

Get the book from Gilet Guitars