B.S.F. or B.Sc.F. Bachelor of Science in Forestry Wood Science and Timber Technology 2 — Questions and Answers
Question 1: Pressure treatment of lumber with preservatives such as copper azole or ACQ is done primarily to:
- Increase wood strength for heavy structural loads
- Protect wood from decay fungi and insect damage in exterior or ground-contact applications (Correct answer)
- Reduce wood weight for transportation
- Improve the appearance of low-grade lumber
Correct answer: Protect wood from decay fungi and insect damage in exterior or ground-contact applications
Pressure treatment forces preservative chemicals deep into the wood to prevent fungal decay and insect attack, extending service life in wet or ground-contact conditions.
Question 2: Which defect causes the most significant reduction in structural lumber strength according to US grading rules?
- Slight discoloration (stain)
- Large knots crossing the grain at critical locations (Correct answer)
- Surface checks on wide faces
- Minor pitch pockets in the heartwood
Correct answer: Large knots crossing the grain at critical locations
Knots interrupt the continuity of wood fibers and create stress concentrations, dramatically reducing tensile and bending strength, especially when located in high-stress zones.
Question 3: Plywood is manufactured using what key process?
- Sawing logs into thin sheets parallel to the grain
- Rotary peeling of logs into veneers that are glued at alternating grain angles (Correct answer)
- Pressing wood chips with adhesive into flat panels
- Slicing cants with band saws at an angle to produce figured veneer
Correct answer: Rotary peeling of logs into veneers that are glued at alternating grain angles
Plywood is made by rotary-cutting logs into veneer sheets and bonding alternating layers with their grain perpendicular, creating a dimensionally stable, strong panel.
Question 4: The term 'modulus of rupture' (MOR) in wood testing measures:
- Wood's resistance to splitting along the grain
- The maximum bending stress a wood specimen can withstand before failure (Correct answer)
- The stiffness of wood under axial compression
- The hardness of wood surfaces
Correct answer: The maximum bending stress a wood specimen can withstand before failure
MOR is the calculated maximum fiber stress at failure in a static bending test, representing the ultimate bending strength of wood.
Question 5: Oriented Strand Board (OSB) differs from plywood in that it:
- Uses solid sawn planks rather than veneers or strands
- Is manufactured from oriented wood strands bonded with resin rather than peeled veneer (Correct answer)
- Requires no adhesive due to natural wood resins
- Is made exclusively from hardwood species
Correct answer: Is manufactured from oriented wood strands bonded with resin rather than peeled veneer
OSB uses small wood strands oriented in specific directions and bonded with resins, allowing the use of small-diameter or lower-value timber species.
Question 6: In the US wood products industry, 'kiln drying' lumber is done primarily to:
- Kill insects and pathogens and reduce moisture content for dimensional stability and strength (Correct answer)
- Increase wood density for high-value markets
- Add preservative chemicals under heat and pressure
- Straighten warped boards before grading
Correct answer: Kill insects and pathogens and reduce moisture content for dimensional stability and strength
Kiln drying removes excess moisture from green lumber, preventing warping and shrinkage in service, increasing strength, and sterilizing the wood.
B.S.F. or B.Sc.F. Bachelor of Science in Forestry Wood Science and Timber Technology 2
Pressure treatment of lumber with preservatives such as copper azole or ACQ is done primarily to: