March 8, 2007 The logging of forests is a very expensive affair, and when there’s a lot of money involved, you can always count on some very special machinery. Two perfect illustrations of this are Plustech/TimberJack/John Deere’s walking tractor prototype (videos here, here and here) and Triton Logging's Sawfish Underwater Harvester. The value of underwater forests in Canada was deemed so large that Triton has developed the Sawfish, a 3-tonne, 3.5-metre-long, yellow submersible with high-resolution cameras so an operator can direct it from the surface. The Sawfish then grasps the base of the tree with its powerful pincers, attaches an inflatable flotation bag to the tree, fills the bag with compressed air and then it cuts the tree with its 1.5-metre chainsaw and the flotation bag carries it to the surface – it can actually handle larger trees than any land-based mechanical harvester due to water buoyancy. As the world’s only deep-water logging machine, it’s a mash-up of remote control, timber-harvesting and submarine technology that can cut down a dozen trees in an hour, at depths of up to 300 metres. The machines are now available to other logging companies at a price around US$750,000 and with no new roads to build and no fires to control, logging underwater suddenly makes economic sense.
The Sawfish not only navigates precisely by a remote pilot, it can operate to any depth. Alternative systems (grapples or divers) are limited to approximately 25 m, even though 80 percent of submerged timber resources are found at greater depths.
While alternative systems use the same mechanism to cut and retrieve trees, the Sawfish achieves significant efficiencies by de-coupling the cutting and surfacing processes, enabling it to perform multiple cuts without returning to the surface.
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