A beam-column analysis of a skyline-logging tail spar was formulated and an example analysis made of a second-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) spar (15.-in. dbh) rigged at 40 ft. The analysis takes into account the taper of the spar tree, the flexibility of the base of the spar, and the eccentric restraining load at the top provided by guylines. Allowable skyline tension on the tail spar is shown to vary with skyline angle and guyline pretension. An optimum guyline pretension that produces the greatest capacity in the spar tree was found to be within a range attainable by hand tightening. The variation of allowable skyline tension with rigging height and spar diameter also is shown. For. Sci. 33(4):971-983.
Logging Systems Specialists, Umatilla National Forest, Pendleton, OR 97801
Publication date: December 1, 1987
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Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.