In order to secure the same tension of all wires, the aeroplane,
when being rigged, should be supported by packing
underneath the lower surfaces as well as by packing underneath
the fuselage or nacelle. In this way the anti-lift wires
are relieved of the weight, and there is no stress upon any
of the wires.
As a general rule the wires of an aeroplane are tensioned
too much. The tension should be sufficient to keep the
framework rigid. Anything more than that lowers the factor
of safety, throws various parts of the framework into undue
compression, pulls the fittings into the wood, and will, in
the end, distort the whole framework of the aeroplane.
Only experience will teach the rigger what tension to
employ. Much may be done by learning the construction
of the various types of aeroplanes, the work the various
parts do, and in cultivating a touch for tensioning wires by
constantly handling them.
5. Wires with no Opposition Wires.--In some few cases
wires will be found which have no opposition wires pulling
in the opposite direction. For instance, an auxiliary lift
wire may run from the bottom of a strut to a spar in the top
plane at a point between struts. In such a case great care
should be taken not to tighten the wire beyond barely taking
up the slack.
Such a wire must be a little slack, or, as illustrated above,
it will distort the framework. That, in the example given,
will spoil the camber (curvature) of the surface, and result
in changing both the lift and the drift at that part of the surface.
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