Production rates and costs for cable, balloon, and helicopter yarding systems in old-growth Douglas-fir Public Deposited
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This report describes initial results of a yarding time study for the Pansy Basin Study, a cooperative research project designed to test the performance of skylines, balloons, and helicopters operating under various conditions of timber and terrain, and over a range of silvicultural and landscape design prescriptions. Observations during the first field season were limited to a single harvesting prescription (clearcutting) and to conventional cutting patterns. Six yarding systems were studied: highlead, North Bend skyline, Grabinski running skyline, shotgun skyline ("flyer"), balloon, inverted skyline, and helicopter. Results of this study suggest that productive yarding time is a function of yarding distance, volume per turn, number of logs per turn, and conditions at the hooking site. For the helicopter and balloon, productive time also is influenced by chord slope and tagline length. Delays and downtime are important segments of total yarding time for all systems and are unpredictable for the most part. Thus, future analysis of delays may lead to significant improvements in yarding production rates. The report includes a procedure for estimating direct yarding costs from time-study data gathered on a sampling basis. Direct yarding cost is often the largest single item on an appraisal or logging cost analysis, and usually the most difficult to estimate. Sufficient detail is included in the explanation of the procedure to permit its use by field personnel in harvest unit planning and appraisal.
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