Quantifying tension and deflection in pre-tensioned speedlines carrying a load

Arborists use speedlines to move debris; efficiently between the tree from which the debris is generated and the landing. To maintain vertical clearance over obstacles, speedlines are pretensioned, but there are no rigorous empirical data to quantify the tension in a pretensioned speedline when it carries a load. Neither has its deflection under load been quantified. We measured the mid-span deflection and tension at both anchors of a speedline under three added loads and three pretensions. Tension at both anchors increased with pretension and added loads up-line tension consistently exceeded down-line tension; and even for the greatest pretension and least added weight, mid-span deflection was substantial. Despite the increased tension in the speedline, bending stress at the anchors was comparatively low. Our results were largely consistent with analyses of logging skylines, despite the differences between components of each system.