The frequency and level of sweep in mixed hardwood saw logs in the eastern United States
Hardwood sawmills traditionally saw logs in a manner that either orients sawlines parallel to the log central axis (straight sawing) or the log surface (allowing for taper). Sweep is characterized as uniform curvature along the entire length of a log. For logs with sweep, lumber yield losses from straight and taper sawing increase with increasing levels of sweep. Curve sawing logs with sweep will increase yields by allowing logs with sweep to be sawn along their natural line of curvature. To better understand the potential for the utilization of curve sawing technology in hardwood sawmills of the eastern United States, it was necessary to determine the frequency and degree of sweep that occurs in hardwood sawlogs. In this study, 1,700 random hardwood logs from 17 sawmills located across eight eastern states were measured, analyzed, and classified for level of sweep based on the log scale deduction percentage attributed to sweep. Whereas the majority of eastern hardwood logs are considered straight, our results show that nearly one third of hardwood sawmill inventories have enough curvature to incur sweep scale deductions of 5 percent or more. For these logs, sweep scale deduction percentages increase as small-end diameter decreases and as length increases. Of the primary species sampled in this study, oak logs exhibited the highest average sweep scale deduction—5.9 percent.
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