Analysis of shear damage to southern pine lumber

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Virginia Polytechnic Institute and State University


This study was conducted as a second part in the shear damage research project at Virginia Tech. The objectives were to verify the results obtained by Gallagher (1984) in the first study under normal mill operations as well as develop a method to compare and evaluate the extent of shear damage in relation to other defects present in southern pine lumber. This was accomplished through two sawmill studies and two kiln cart surveys performed in different geographic locations.

Visible indicators such as stump-pull that are used to determine shear damage extent are often misleading. Stump-pull, used as a scaling deduction for shear damage, does not fully determine the extent of shear damage present. Shatter is often present in greater amounts over the cross section of the butt of the log. The recommendation of six inches of butt trim that was determined to minimize value losses in the first study is supported by the results obtained in this research. A trim of six inches removed 94 to 99 percent of shear damage in this study.

Defects other than shear damage were present on dried and surfaced lumber. Drying checks and splits along with shake were often observed on the lumber ends. These defects often extend further up on the lumber ends, past the seven inch simulated trim. Shake was determined to be the limiting defect. Shatter, in the absence of shake, was determined to be limiting.

Kiln cart surveys conducted at mills that utilize a large percentage of sheared logs can be an inexpensive and effective tool to enable mill personnel to determine the extent of shear damage in relation to other defects present on lumber ends based on green trim already taken.