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"Edge"
tension lines define the edges and the sides of each module. The
three-way column has three edge lines for each module. In most cases,
edges carry less tension than draw or sling lines.
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"Draw"
tension lines pull the modules toward one another. In the three-way
column, each module is connected to each neighbor by three ascending
draws and three descending draw lines.
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"Sling"
tension lines suspend the modules, performing like the slings used
in rigging work. They connect one module to the next and are generally
in opposition to the draw lines. In a three-way column six slings
are required in order to link two modules.
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Above is a
three-way module. In this simple figure all tension lines can be
called edges: six end-edges and three side-edges. They define, roughly,
a triangular prism. When viewed through the vertical axis the module
has a left-rotation helix. The opposite is true when viewed from
the side: the struts relate to one another in a clockwise or right-rotation
helix.
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Right
helix
Left
helix
Right
helix
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Three
module, three-way column
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