Mechanism of Crook Development in Lumber During Drying
Keywords:
Drying, warp, crook, bow, oak, drying stresses, longitudinal shrinkageAbstract
Crook can cause yield and grade loss in lumber. In this study the mechanism of crook was studied so that a better understanding might lead to methods for minimizing its development. Crook was observed to begin at an average moisture content of about 50%, and then to increase linearly as moisture content decreases. Differential longitudinal shrinkage on opposite edges of boards is shown to be the cause of crook. A model was developed to predict crook from differential longitudinal shrinkage, and experimental results agree with model predictions. The model was extended so that estimates can be made of the restraining force necessary to prevent crook.References
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