Technical Report

Two thinnings of douglas-fir with crawler tractors : time differences

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  • Two intermediate cuttings were made in a Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand on the Wilark forest management research area in northwestern Oregon. Age of trees in the stand varied from 47 to 62 years at the first cutting. Crawler tractors were used in both extractions. In the first cutting, the time required for log production was 6.21 man-hours for a thousand board feet Scribner log rule at the mill site on the area. An additional 1.01 man-hours a thousand board feet was accounted for in delays not associated with productive time. A total of 19,702 feet of road was constructed. Construction time for 100 feet of road ranged from 1.55 man-hours for skid roads to 9.39 man hours for main road. Road construction increased total time for log production by 0.92 man-hour for a thousand board feet in the first cutting. The time required for log production in the second cutting was 3.78 man-hours for a thousand board feet, and delays amounted to 0.43 man-hour a thousand. A separate time study was made to determine the influence of delays present in the actual extractions on the cost of log production. Frequently ignored factors that appeared to affect economic outcome were favorable weather, efficient technique in extraction, and skilled labor.
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