Curve sawing spruce sawlogs containing sweep can reduce drying distortion when compared with conventional sawing.

Summary Research presented in this paper compares the drying degrade and bending stiffness of sawn timber produced from Sitka spruce (Picea sitchensis (Bong.) Carr) sawlogs containing natural curvature, which were subjected to either curve or conventional straight sawing. A total of 132 square-edged battens measuring 4.8 m × 97 mm × 47 mm were produced from 44 Sitka spruce sawlogs which contained sweep. After either curve or straight sawing, all battens were measured for wet bow and spring (crook), prior to being kiln dried and then remeasured for dry bow, spring, twist and three-point bending stiffness. Significant differences existed in drying degrade between the two sawing methods. Wet and dry bow were significantly lower in the straight sawn battens but the reduction after drying was much greater for curve sawing compared with straight sawing. Wet and dry spring and dry twist were all significantly lower in the curve sawn battens. There was no significant difference between the two sets of battens when measuring three-point bending stiffness. These results provide evidence that shape distortion can be reduced in square-edged sawn timber that has been cut from spruce sawlogs containing sweep if logs are processed using curve rather than conventional straight sawing.