Performance of radiata pine as moulding raw material

This study was conducted to determine the suitability of radiata pine lumber for use as a raw material for mouldings. Lumber was harvested from two separate forest sites; one site was 27 years old and conservatively managed and the other was a 23-year-old agro-forestry site. Harvest age, maturity, and ring orientation were used to see the impact each had on the distortion of mouldings. Dimension lumber of 40 by 100 mm (1-1/2 by 4 in.) was used as the raw material, and was split, producing two pieces of 100- by 20-mm moulding stock. The moulding was cycled from 12 to 18 percent equilibrium moisture content (EMC) and back to 12 percent in an environmental chamber. The conservatively managed lumber (older) had less initial distortion than the agro-forestry lumber (younger), indicating there may have been fewer growth and drying stresses present in the older tree lumber. The agro-forestry lumber initially had twice the amount of crook, and more than 50 percent greater bow than the older lumber. No statistical differences were found in the initial twist between the two stands. When the mouldings were cycled to 18 percent MC, the older lumber had 75 percent fewer pieces exceeding crook limits, 50 percent fewer pieces exceeding bow limits, and 33 percent fewer pieces exceeding twists limits than the lumber from the agro-forestry trees. When the lumber was returned to 12 percent MC, no differences were found in the distortion change for crook and twist, although younger stock had more bow. For initial distortion measurements flatsawn pieces were less prone to crook than the quartersawn or cross-sawn pieces. Quartersawn pieces were found to have the highest amount of crook. No differences were found when the mouldings were cycled to 18 percent and back to 12 percent MC. Initial bow measurements showed no difference between ring orientations; however, the cross-sawn pieces had less movement than the other two orientations at 18 percent MC. When the mouldings were reduced to 12 percent, the quartersawn pieces were found to have the highest bow. Twist was lowest in the cross-sawn pieces. Flatsawn pieces had the significantly highest change in twist when the EMC conditions were increased to 18 percent MC and returned to 12 percent MC. Juvenile wood was found to have much higher levels of bow and crook than the mature and transition wood. No difference between maturity levels was detected in the amount of distortion change when the EMC was raised to 18 percent, although the juvenile wood did have more crook when the EMC was reduced again to 12 percent MC. In terms of twist, no differences were found at 12 or 18 percent between the three maturity levels, but the mature wood moved significantly less than the other groupings when EMC conditions were returned to 12 percent. When the ability to return to original shape was examined, it was found that the older stock had 17 and 29 percent more pieces, respectively, than the younger stock which resumed to within 10 percent of the original crook and bow measurements. Only 8 percent more of the older stock resumed to its original shape for twist when compared to the younger stock.