Changing forest conditions and evolving management practices are impacting the raw material available to sawmills in western North America. The sawtimber harvested today is often small in diameter, includes sweep, and contains a large proportion of juvenile wood. The purpose of this study was to assess warp, modulus of elasticity (MOE), and grade of curve-sawn (sawn following the curve of the log) structural lumber produced from small-diameter Douglas-fir logs. There were 120 small-diameter interior Douglas-fir logs that were grouped into three sweep categories. All logs were curve sawn, and the resulting 2 by 6-inch, 16-foot lumber was dried in a commercial dry kiln, planed, and measured for bow, crook, twist, MOE, and grade. Most of the lumber sawn from all three log groups was of high quality with small knots and little warp. A majority of this lumber graded Select Structural or No. I in the Western Wood Products Association (WWPA) structural joists and planks category (6). Although warp was recorded in every piece of study lumber, only one piece (moderate-sweep log group) had sufficient warp to be degraded from Select Structural or No. 1 to No. 2. Analyses of measurements taken shortly after drying and after 73 days of storage showed that mean bow was significantly greatest and that mean twist was significantly (marginally) least in lumber sawn from the high-sweep log group. Analyses also showed that MOE and the proportion of Select Structural lumber were significantly greatest in lumber sawn from the high-sweep log group. These findings indicate that high-quality structural lumber can be produced by curve sawing small-diameter Douglas-fir logs. These findings also challenge traditional thought that straight logs are superior to logs with sweep for the production of structural lumber.
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