161 - Chapter 3 Wood Qualities of Wood Strong & Stiff...

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1 Chapter 3 Wood Qualities of Wood Light Easily worked / shaped Recyclable Biodegradable Renewable Resource Undesirable Characteristics of Wood Not perfectly straight nor precise Contains growth defects Burns easily Decays Susceptible to Insect Damage
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2 Tree Composition Bark Cambium Sapwood Heartwood Pith Tree Growth Springwood (earlywood) Î Faster growth Î Cells larger and less dense Summerwood (latewood) Î Slower growth Î Cells smaller and denser Types of Trees / Woods Oak Pine Poplar Oak Poplar Pine
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3 Construction Uses for Wood Structural Framing Subfloors and Roof Sheathing Finish cabinetry and Trim Lumber Production - Sawing Plain Sawing Î Maximum Yield Î Varying grain pattern Î Common use - Framing lumber Lumber Production - Sawing Quarter Sawing Î Perpendicular to annual rings Î Less yield, but consistent grain pattern Î Improved wearing quality, less distortion
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4 Typical Sawing Method Lumber Drying Drying Methods Î Air Î Kiln Drying Effects Î Shrinkage Î Reduced weight Î Increase of strength and stiffness Î More dimensional stable Differential Shrinkage tangential) during drying can cause distortions
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5 Lumber Surfacing Purpose; Î Smooth Î Dimensional precision Designations; S2S, S4S Surfacing typically performed before or after drying? Rough sawn (not surfaced) S4S Lumber Defects Growth defects Î Î Decay and/or insect damage Manufacturing Defects Î Î Crook, bow, Î Cup, and/or twist
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6 Graded by: Appearance (Finish Lumber) Lumber sold by - Species and Grade Better Grade Î Higher price Scarce or Higher Quality Species Î Higher price Spruce, Fir, or Pine Stud Surfaced Dry No 2 Lumber Kiln Dried (19% moisture)
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161 - Chapter 3 Wood Qualities of Wood Strong & Stiff...

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