Warp Reduction in Kiln-Drying Hardwood Dimension

The occurrence of crook, twist, and cup in lumber can cause major yield losses, discourage utilization of warp-prone lumber from small-diameter trees, and prevent use of more efficient processing methods. A restraining device was designed that consists of hydraulic cylinders and steel cables that encircle a load of lumber at three places. A pump allows maintenance of constant force with the cylinders during load shrinkage and also allows selection of different experimental restraining forces. Three kiln loads, approximately 425 board feet each, of 5/4 mixed oak and hickory (3- and 6-in. widths) were dried at no restraint (control) and with 1,500 and 2,700 pounds restraint imposed by the cylinders. Cup and bow were not reduced. Twist was reduced by 25 to 50 percent and crook was reduced by up to 35 percent. Further refinements in the restraint system would allow application of larger restraints and thus greater crook and twist reductions.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member