1.1.5 Assessing arborist rigging systems
Arborists use many different rigging systems to lower branches and timber during tree dismantling operations . Some of these techniques are very similar to rigging and lowering methods used by rescue crews . It is beyond the scope of this manual to discuss all common arborist rigging techniques in detail .
The rope is set through a heavy-duty rigging block , usually attached to the highest point in the tree ’ s structure that will still bear the intended loads .
On the ground , a crew member lowers the piece by allowing slack into a friction management device such as a Portawrap or rigging bollard . Smaller pieces may be lowered by hand .
When the branches have been removed , the climber may fell out the head of the tree and sections of timber if space permits . If there is no space to drop anything , the climber will conduct negative rigging as shown in the inset box . High peak forces can be generated using this method , and the climber will probably be least prepared for self-rescue if anything goes wrong .
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