Arborist MRT systems
The simplest arborist MRT systems use a prusik hitch ( commonly called an English prusik by arborists in Australia and New Zealand ) for friction management . Until comparatively recently this was the default option that would be used by almost every tree climber .
Over the last few decades , with better knowledge sharing and a wider range of companies making specialist equipment for tree climbing , arborists have been ‘ tweaking ’ their systems to gain improvements in efficiency and reduce the ergonomic impact of traditional climbing methods .
One such tweak is shown in system B above . The system replaces the prusik with a Distel hitch and adds a prusik-tending pulley . By attaching the splice to the top of the pulley with a second karabiner the system retains a better orientation and is easier to tend .
For rescue purposes , the climber can be lowered in much the same manner as with a normal prusik , by lightly depressing the top of the hitch with the fingers .
Some climbers use devices which are custom designed for MRT tree climbing . The range of such devices , and the speed of development , prevent a comprehensive description of each one .
For rescue purposes , it is important to note that not all of these devices are intuitive , and some can be opened to a degree which permits very rapid descent . The device pictured is called a SpiderJack and requires a separate action to tend the friction in the system : depressing the lower lever opens the device and will essentially drop the casualty until the lever is released .
Always ensure that a suitable , taut belay has been installed before attempting to lower the casualty on their own system . This is particularly true where the casualty ’ s friction device is unfamiliar .
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