Drying and conditioning treatments to control warp in coconut trunk lumber [Philippines].
1985
Laxamana M.G.
Results indicated that more coco lumber suitable for housing and furniture components were obtained from the butt than the middle and top portions of the trunks. Collapse was predominant in core-containing board at the top portion of the trunk. Surface checks tended to develop more on the bark-side of the board sawn from the butt. Boards from the butt and middle sections were prone to twist. These defects were appreciably reduced by air-drying. During the dry season, air-drying time for 50-mm thick green coco hard and coco soft boards from the three sections of the trunk to an average moisture content (MC) of 18% ranged from 11-14 and 13-14 weeks, respectively. Drying time during the wet season from green condition to 19-20% MC was 14-16 weeks for cocohard and about 16-17 weeks for cocosoft boards. Cocohard was dried from green to 9-10 percent MC in 289-367 hours at 43 C dry bulb temperature (dbt) and 40.4 C wet bulb temperature, and 332-346 hours for cocosoft at the same drying condition and final MC. At an initial dbt of 49 and wbt of 46 C, the drying time of 3.3 long cocohard from 52 to 12% and cocosoft 135 to 11% was 193 hours. Two hundred seventy four hours were required for drying cocohard from 68 to 11% MC, using an initial dbt of 43 C and 178 hours for cocosoft from 216 to 16% MC, using an initial (dbt) 49 and 2 C wet bulb depression. Forced-air drying (FAD) of 50 mm boards accelerated the reduction of the initial green MC in about 24-37% in 277 hours. The subsequent kiln drying was likewise appreciably reduced to 61-100 hours at a final MC of 1-15%. The application of a 4-hour reconditioning treatment in a steaming chamber did not fully remove collapse in some cocosoft.
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