Moisture-related distortion of timber boards of radiata pine: Comparison with Norway spruce

Artikel i vetenskaplig tidskrift, 2005

Based on material data obtained by several researchers at Forest Research in New Zealand, with respect to variations in the main material properties from pith to bark, the distortion model developed earlier for Norway spruce has been further modified for radiata pine. Numerical simulations were performed for both pine and spruce to investigate how different sawn pattern options affect the shape stability of individual boards. Results for spruce presented earlier have shown clearly that warping of the timber products is strongly influenced by the annual ring patterns within the individual boards. Comparisons between the two species were performed to study how the radial variations in the basic properties such as shrinkage parameters, stiffness parameters, and spiral grain have influence on the warping. Generally, the intrinsic patterns of variation in wood properties within stems were similar, and both species show a tendency to distort with changing moisture environment. There are strong indications that intelligent re-combination of material in glued products may overcome many of the inherent problems in using biological material with predictable variation in material properties.