Recovery from simulated sawn logs with sweep.

Abstract

A sawing simulator, AUTOSAW, was used to examine the effect of increasing sweep on lumber recovery. Sample material consisted of 51 logs from 22 western hemlock (Tsuga heterophylla (Raf.) Sarg. ) trees in western Oregon, United States. All knots on the 4.9-m logs were measured, mapped, and converted into 3-dimensional digital formats. The digital logs were then increasingly bent, in 25.4-mm (1-inch) increments, with the bend occurring at the mid-point for one set of logs and at quarterway from the log small-end for another, and sawn into primarily structural grade dimension lumber. On average, conversion decreased at a rate of 10% for each 100-mm increase in sweep, equivalent to a decrease of 5-7% for each 0.1 unit increase in sweep-to-diameter (s/d) ratio. Conversion losses were represented by an exponential decay function. There was no significant difference in conversions between the two sets of logs; however, the rate of loss of Select Structural and 1 Common lumber was greater for logs bent at the mid-point when sweep was within 51 to 152 mm (2 to 6 inches).

Citation

Monserud, Robert A.; Parry, Dean L.; Todoroki, Christine L. 2004. Recovery from simulated sawn logs with sweep. New Zealand Journal of Forestry Science. 34(2): 190-205