wonwinglo

Biplanes are fully rigged both internally and externally,the interior structure of an early aircraft wings are braced with steel rods placed under tension within the structure,brackets are bolted to the main spars and stiffened rib sections,usually either swaged or adjustable turnbuckle type fittings are used,sometimes piano wire is used with a very special tool used to perform the complex end fittings.If the wing was not rigged in this way it would suffer from internal stresses and strains which would gradually weaken the structure,above all movement would set in.
Then we have the external bracing wires or more correctly on vintage types streamlined shaped extruded metal,on the ends are usually fork end pieces which again are adjustable,these are checked to be within safety limits with a simple check,this is to insert a piece of wire into the turnbuckle end,if it touches the threaded portion then it is fine,if it does not then it is considered as out of safety,on top of this locknuts are placed against the turnbuckle to stop any further movement of the rigging.Some early aircraft have stranded wire rigging with a swaged clevis built in,these type of fittings do not always have adjusters and need to be made up exactly as the aircraft is set in the flying or fully rigged position according to the manufacturers handbook.Low wing monocoque aeroplanes can also have rigging as per the Ryan PT-22 etc,such machines are very strong and highly stressed.
These days external rigging is very rarely used except perhaps for some tail bracing if required.
I have just touched the surface of this subject here and perhaps one day go into a little more detail.

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