Grain Angle Variation: A Major Determinant of Twist in Sawn Picea abies (L.) Karst
Warp, mainly twist, of sawn wood causes problems for the construction industry. Twist is caused by annual ring curvature, grain angle and tangential shrinkage. Logs of Norway spruce [Picea abies (L.) Karst.] were selected from 14 areas in central Sweden. Grain angle was measured on the log surface and on the boards. The slope of the grain angle curve from pith to bark was estimated from these measurements. After kiln drying to 12% moisture content using a conventional drying schedule, twist was measured with a wedge. Grain angle on the log surface accounted for a larger part of twist variation than grain angle on the board. It appears that this was because grain angle on the log surface was more strongly correlated with the slope of the grain angle curve from pith to bark. Together, grain angle on the log surface and the described slope accounted for 70% of twist variation.
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Document Type: Research Article
Publication date: 2001-05-01