Effects of Grain Angle on Wood Properties and Uses
Northcott (1965) made the point that if wood were isotropic, spiral grain would have no influence on its properties. It is because wood has different properties in the longitudinal, radial, and tangential directions relative to the orientation of its cellular components that any change in cellular orientation affects its usefulness. Except for the most extreme forms of spiral grain — with grain angles in excess of 30°, for example — the effects of spirality appear to relate solely to changes in the axes of anisotropy. Thus the magnitude of the changes which result from a given level of spirality depends on the degree of anisotropy normal for the species. In this connection it may be noted that the anisotropy of coniferous wood is much more pronounced than that of broad-leaved woods (Kollmann and Côté 1968) and therefore properties of softwoods should change more than those of hardwoods in response to spiral grain. However, the effects of anisotropy may differ quite markedly even between coniferous woods. For example, Banks (1969) noted that Araucaria columnaris twists on drying less than Pinus patula with the same spiral angle.
KeywordsPermeability Anisotropy Shipping Shrinkage Wharf
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