Väätäinen, K., Ala– Fossi, A., Nuutinen, Y. and Röser, D. 2006. The Effect of Single Grip Harvester’s Log Bunching on Forwarder Efficiency. Baltic Forestry, 12 (1): 64-69

In the CTL–harvesting method stems are bucked and cut into several timber assortments at the harvesting site by a single grip harvester. During cutting, the harvester operator can directly affect the efficiency of forwarding. Harvester and forwarder have different productivities and variations in stem size have a larger effect on the harvester than on the forwarder. In this study one professional forwarder operator loaded logs, which were cut and bunched by six different harvester operators in the same thinning stand. The piles were measured and estimated according to size, location and accessibility etc. The loading stage of forwarding was measured using a manual time study. The study revealed that the method of bunching timber assortments during cutting varied a lot among different harvester operators. The largest differences among the harvester operator’s bunching results caused about 30 % difference in loading time of piles per cubic metre. The studied calculation models from the literature revealed that 40 % time savings per cubic metre in loading phase results in 20 % time savings for the whole forwarding cycle, when the forwarding distance is 300 metres. Harvesting should be understood as a processing chain in which the first step (cutting) affects the latter step (forwarding). By optimising the size of the pile the harvester operator can improve the productivity of the harvester–forwarder chain. Furthermore, the harvester operators’ planning of the thinning track network in the stand can have a significant effect on the forwarding productivity, particularly in challenging terrains.

Key words: Forwarder, CTL harvesting, bunching, log pile, loading timber, productivity