- 2079 Bhadra · 2 marks
Defects of timber by natural forces
Short answer
Natural forces like wind, frost and sun cause defects: shakes (heart, star, cup) from temperature extremes, wind cracks, upsets (crushed fibres), rind galls from branch wounds, burls, twisted fibres, and also callus, water stain and lightning damage.
Explain in brief about the defects in timber due to natural forces.
Defects caused by natural forces (wind, frost, sun, lightning or abnormal growth) in the standing tree are:
- Knots: bases of branches enclosed within the wood; they cut across the grain and reduce strength.
- Shakes: heart, star, cup and radial shakes, which are cracks along the fibres due to frost, sun heat, wind or over-maturity.
- Wind cracks and upsets: crushed or broken fibres from strong winds or rough felling.
- Rind galls: swellings where a branch was lost and the bark folded over.
- Burls and twisted fibres: abnormal growths or spiral grain due to constant wind in one direction.
- Callus, water stain and lightning damage.
✓ Answer checked by Claude Opus 5.5 (high effort)
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