Fly System - The Line Set

The Line Set

The line set is the fundamental machine of a typical fly system.

The function of a typical line set is to fly (raise and lower) a slender beam (typically a steel pipe) known as a batten (or a bar in the UK) by hoisting it with lift lines (typically synthetic rope or steel cable). By hanging scenery, lighting, or other equipment to a batten, they in turn may also be flown. A batten is said to be "flying in" when it is being lowered toward the stage, and "flying out" when it is being raised into the fly space. Battens may be just a few feet in length or may extend from one wing (side) of the stage to the other. A batten is suspended from above by at least two lift lines, but long battens may require six or more lift lines.

In manual rigging, a line set’s lift lines support weights opposite their connections to the batten in order to balance the gravity load of the batten and whatever it carries. The lift lines are reeved through a series of pulleys, known as blocks, that are mounted above the stage to fly loft structure. An operating line (a.k.a. hand line or purchase line) allows riggers on the fly crew to raise and lower the batten.

Automated rigging sometimes uses weights to help balance line set loads in a manner similar to manual counterweight rigging. Otherwise it relies solely on the motor power of an electric hoist to fly a line set.

Together, a series of parallel line sets regularly spaced up and down stage, commonly at 6", 8" or 9" centers, comprise the bulk of most fly systems. Theatrical rigging systems are made up of hemp, counterweight and/or automated line sets able to serve various functions.