Maximizing the Standing Skyline Log Load Using a Variable Length Tagline

John Sessions,Jeff Wimer,Kevin Lyons

doi:10.3390/f12070927

Abstract

The standing skyline continues to be a common cable logging configuration. In payload analysis it is usually assumed that the tagline (line connecting the logs to the carriage) length is held constant while yarding a turn up the skyline corridor. We show this assumption severely limits the skyline load-carrying capacity for skylines operating with partial suspension. We suggest that smart carriage technology could markedly increase the log load capacity through the use of a variable length tagline, and thus logging productivity. A methodology for estimating the log load capacity for a standing skyline with variable tagline length is presented. We illustrate that increases of 30–40 percent in log load are possible with a variable length tagline.

Highlights

The standing skyline continues to be a common cable-logging configuration and when yarding uphill it employs a skyline and mainline, and does not require a haulback (Figure 1).When using a standing skyline, the unstretched length of the skyline is not changed while yarding a turn
This paper will examine in a full cable system analysis, the effect of reducing the log angle on the payload that can be moved by a standing skyline while varying the tagline length. In this manuscript we introduce an algorithm for establishing the lower bound on the maximum log load that can be brought to the landing with a variable length tagline from each terrain point within yarding limits
Our objective is to minimize the number of log loads to yard the skyline corridor. We assume this is met by maximizing the log load that can be brought from each terrain point to the landing, and by extension, maximizing the sum of the maximum log loads over all the terrain points within yarding limits on the skyline corridor without exceeding the maximum allowable tension in the skyline or mainline at any point

Summary

Introduction

The standing skyline continues to be a common cable-logging configuration and when yarding uphill it employs a skyline and mainline, and does not require a haulback (Figure 1).When using a standing skyline, the unstretched length of the skyline is not changed while yarding a turn. The harvest planning problem is to develop a plan that safely maximizes the system productivity Often this is achieved by minimizing the number of log loads needed to yard the skyline corridor. Minimizing the number of log loads requires carrying the maximum permissible log load each trip which implies maximizing the load that can be brought to roadside from each terrain point either fully suspended or partially suspended depending upon the design requirements. Mathematical formulations and algorithms for determining the maximum log load that can be carried for a standing skyline system under full and partial suspension for uphill and downhill yarding for single spans have been presented by [1,2] and others, with particular emphasis on load path analysis as the carriage moves along the skyline with a log load. There has been some interest in the doublehitch system to take advantage of a reduced load clearance by hooking logs on both ends to fully suspend the log [7]

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Conclusion