Twist Assessment and Reduction in Southern Pine 2 by 4'S‪.‬

Abstract As part of an ongoing research program aimed at warp reduction in Stud-grade lumber, 96 southern yellow pine 2 by 4s were high temperature kiln-dried. Following drying, torsional properties of 15 highly twisted boards were evaluated. Twisted boards were torqued until their ends were parallel, that is, free of twist. Inherent torsional stress and rigidity are reported. Correlation between torsional properties, i.e., stress and strain, and other predictors such as density and twist angle are also reported. After torsional measurements were taken, the 96 boards were repackaged, top weight restrained, and steam conditioned at approximately 215[degrees] F dry-bulb and 208[degrees] F wet-bulb temperature (EMC of approximately 12%) for approximately 6 hours. Weight restraint was a minimum of 100 lb./ft.[.sup.2] Differences in twist between completion of drying and completion of conditioning are reported. Results of the analysis presented herein may be used in studying the fundamental nature of twist in yellow pine, in optimizing remedial procedures, and in maximizing grade recovery.