A "new" method of incising, adapted from the conventional roller incising method, is currently under development by the Composite Department at Forintek Canada Corp. A pilot study has been performed by the Wood Engineering Department to evaluate the effect of this incising method on the bending strength of lumber. Third point bending tests have been performed on two matched groups of 1 x 4 clear Hem-Fir lumber. One group served as the control group while the other group has been incised. Modulus of Rupture (MOR) and Modulus of E l a s t i c i t y (MOE) of the specimens have been determined by the testing . The experimental results have been fitted to normal, two-parameter Weibull, and three-parameter Weibull distributions .
From these distributions, the fifth percentile MOR and MOE values of the two groups have been determined. Test results indicate that there is approximately 20% reduction in the fifth percentile bending strength of the lumber incised by the new method. Similarly, there is a reduction in the mean bending stiffness (MOE) of approximately 11%. Statistical methods employed in this study indicate that the reduction in the mean MOR due to the "new* method of incising is statistically significant.
There are two parts to this publication. Part I is the user's manual for LUSI, which is a computer program developed to simplify the lumber size control process. Part II introduces some basic concpets of statistical lumber size control. It is recommended that LUSI users familiarize themselves with the concept introduced in Part II to enable them to use LUSI effectively.