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Unformatted text preview: Test 3 study guide Chapter 3 Advantages of wood: • Strong and stiff like concrete • Light in weight vs. concrete • Easily shaped and easy to work on • Fastens together quickly and economical • Recyclable and sustainable material • Biodegradable • Renewable resource Disadvantages: • Not perfectly straight or precise b/c natural material • Size and shape are affected by moisture (twist or bend) • Contains growth defects • Can split and warp • Burns easily and requires fire protection • Decays with contact of water • Susceptible to insect damage Components of lumber: • Bark (dead layer) • Cambium (thin, alive, and replenishing mechanism for bark) • Sapwood (all nutrients of the tree are located here) • Heartwood (gives strength to tree) • Pith (innermost circle; weak and soft) Trees Cells and growth • Primarily hollow circular cells; axis running parallel to tree (grain direction); Tough cellulose bound by lignin (impacts the properties of wood ie strength and appearance) • Early Wood : Springwood Cells if the tree is exposed to more water; faster growth; cells are larger and less dense • Latewood : Summerwood slower growth; cells smaller and denser • HW (hardwood) : Oak; poplar • SW (softwood) : Pine Uses: • Structural Framing- softwood mainly • Subfloors and sheathing- wood panels • Siding- Structural and exposed- usually some use of softwood • Finish- cabinetry and trim- usually hardwood to get desired texture Lumber Production: • Sawing 1.Plain Sawing: use framing lumber usually because don’t care about appearance …care about strength; maximum yield (want to get as many pieces as possible); varying grain pattern 2.Quarter Sawing: design oriented (splits circle into quarters); perpendicular to annual rings; less yield, but consistent grain pattern; behaves better (less distortion) and improved quality (of wearing); used for flooring or exposed uses 3. Typical Sawing Method: most typical, don’t care about pattern Lumber Drying: • Methods: Air or Kiln • Effects of Drying: o Shrinkage (caused by water draining by wood) Differential shrinkage- depending on where and what ring you are cutting wood will twist and deform; distortions that occur during drying o Reduced weight (caused by lack of water) o Increased strength and stiffness o More stable in cutting and stable in dimension Lumber Surfacing: • Purpose: depends on if wood is exposed or not; smooth; dimensional precision • Designation: S2S (2 sides sanded) S4S (4 sides sanded; done after drying Lumber Defects: • Growth Defects: Knots and holes- reduce structural strength; Decay and/or insect damage •...
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This note was uploaded on 11/14/2010 for the course CM 2121 taught by Professor Spring during the Spring '08 term at LSU.
- Spring '08