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. Such a condition will cause the aeroplane to lose its directional stability and also to fly one wing down.
I cannot impress this matter of tension upon the reader too strongly. It is of the utmost importance. When this, and also accuracy in securing the various adjustments, has been learned, one is on the way to becoming a good rigger.
6. Wire Loops.—Wire is often bent over at its end in the form of a loop, in order to connect with a turnbuckle or fitting. These loops, even when made as perfectly as possible, have a tendency to elongate, thus spoiling the adjustment of the wires. Great care should be taken to minimize this as much as possible. The rules to be observed are as follows: