A necessary aspect of certain forestry industries, cable logging uses a yarder and numerous cables, chains, and grapplers, in a number of configurations, to remove logs from areas that are too steep for or otherwise inaccessible to loaders and trucks. Two of the more common cable logging methods include high lead logging and skyline logging. Both techniques use cables, suspended over a worksite, on which pieces of equipment travel, retrieve logs, and travel back to a desired location. Once logs arrive at an accessible location, loaders stack the felled trees onto trucks for transport.
The yarder, which is the main piece of equipment used in cable logging, can be mounted on a sled, a trailer, or a very large, motorized, tracked vehicle. Cable logging yarders have a tall mast, or spar, and numerous cables run the length of the spar to the top, where they are threaded through a circular mount and extended outward. On a tracked vehicle, these cables are usually held on drums or large mechanical spools. A swing yarder, also known as a grapple yarder, generally has an extendable, rotating arm with pulleys on the end, through which the cables run.
Most of the cables extending from the top of the spar stabilize the yarder. Loggers attach the ends of the cables to large stumps located around the periphery of the yarder. The cables used for the logging lines may extend from one yarder to another, across a valley, or from a yarder to a tree down the side of a mountain. Mechanical, motorized, or self-propelling carriages run the length of the logging cables and have a device that fastens to or around the logs.
High lead cable logging usually involves a type of carriage with vertical, hooked chains that extend downward. The carriage travels down the cable until it arrives at the desired position. Once the carriage is in position, the loggers wrap the dangling chains around logs, fastening each chain with a hook. The carriage rises and carries or drags the logs to another location along the cable.
Skyline logging involves a similar principle but generally involves much higher cables. The carriage descends, workers attach the logs to the device, and the line suspends the logs high in the air. The carriage then travels along the cable to the desired location. Swing yarders usually have mechanical grappling hooks in place of carriages that traverse the logging cable, lift individual logs, and carry them from one area to another.