2004 Council on Forest Engineering (COFE) Conference Proceedings: “Machines and People, The Interface” Hot Springs, April 27-30, 2004 1 Productivity and Cost Evaluation for Non-guyline Yarders in Northern Idaho Simon Largo Graduate Research Assistant Han-Sup Han Assistant Professor of Forest Engineering Leonard Johnson Professor of Forest Engineering Department of Forest Products University of Idaho INTRODUCTION Harvesting areas often include a riparian zone that requires protection from logging activities (Lawson 2002). Felling and wood extraction activities in these zones can be prohibitive due to strict environmental requirements and higher logging costs. Greater difficulties occur on small parcels of steep slopes (> 35%) along streams and lakes, where ground-based wood extraction may not be applied. In such environmentally sensitive areas, it is hard to justify use of large or expensive cable or helicopter logging equipment to harvest timber. Therefore, there are not only environmental requirements (Idaho’s Forest Practices Act), but also economic objectives to be achieved in these sensitive areas from commercial thinning operations. A new approach for skyline operations that is suited to harvesting timber on steep slopes and environmentally sensitive zones is the use of non-guyline yarders with a gravity skyline system. Non-guyline yarders have been developed by adding a winch and a tower to conventional logging equipment (feller-bunchers and excavators). Without guylines to rig, the machine can be moved more quickly between landing positions along the hauling roads, or within stands. The elimination of guylines on the rear of the main spar, also allows forest traffic to pass without disruption of the yarding operation. The objectives of the study were to: 1) determine yarding production rates and costs for two non-guyline yarders, and 2) evaluate their operational capabilities and limitations in commercial thinning operations in Northern Idaho. STUDY METHODS Non-guyline yarding equipment Two modified yarders without guylines were recently introduced in northern Idaho by independent logging contractors for use in commercial thinning: the TIMBCO T-425 yarder (a feller/buncher-based machine), and the CAT 315-L yarder (an excavator- based machine). Both were re-built as yarders with the addition of a two-drum winch (Allied Winch W400™ model) and a small tower for use as a gravity skyline system without guylines. (Table 1). A live skyline with a gravity carriage return (Christy™) and with lateral yarding capacity was used for both TIMBCO and CAT yarders to transport logs and tree- lengths uphill to the landings respectively (Fry 1983). Both yarders allowed for