INCREASING VALUE FROM PRUNED LOGS WITH PARTIAL KNOWLEDGE OF INTERNAL DEFECTS*

The hypothesis that lumber value increases when the sawpattern embodies partial knowledge of the internal defect structure was tested. Two methods for estimating the internal structure were evaluated: one used annual ring-counts and the other used the definition of defect core. The former method was applied to pruned Pseudotsuga menziesii (Mirb.) Franco (Douglas fir) logs from the United States and the latter to logs from New Zealand that, although with similar diameters to the United States logs, were substantially younger, pruned much earlier, and had smaller defect cores. Digital models of the logs were constructed. External shape representations were based on direct log measurements. Internal defects were computer-generated for the United States logs, whereas actual branch stub measurements were used for the New Zealand logs. The models were sawn in the AUTOSAW sawing simulator, and the resultant lumber was graded and priced. The sum of lumber prices established a value for each log. That value was compared with lower and upper bounds derived from parallel simulations based on volume-optimising and value-optimising sawpatterns, respectively. The lower bound assumed no a priori knowledge of internal defects while the upper assumed full a priori knowledge. With the annual ring count method there was no significant difference in mean log value when compared to the lower bound; however, potential to increase value, demonstrated by the difference between lower and upper bounds was significant at 3%. With the defect core method a significant increase of 5 % was found and potential to increase value was nearly 11%