Originally Posted by
9402sierra
Don't be so quick to shout CYA on this one. Biplanes of that era carry all of the positive g loads on the wings through the flying wires to the aircraft structure. The landing wires carry all of the negative g loads as well as the loads encountered during landing into the aircraft structure. Most aircraft of the barnstorming era have redundant flying and landing wires so that if a wire breaks in flight, the second wire will prevent the wings on that side from moving unless the second, redundant, wire is stressed beyond its limit. More modern designs starting in the late thirties pretension the flying and landing wires so that normal loading conditions relieve the loads on one set while not appreciably increasing the loads on the other. On my Travel Air, there is no pretension, so the load on the flying or landing wire set is directly proportional to the g loading on the airplane. After having reviewed the stress analysis originally submitted for Travel Air certification I can tell you there isn't a huge margin of safety in the flying and landing wires and I suspect it isn't much different for other aircraft of that era.
Nicks concentrate the load at the point of the nick. As an absolute minimum, nicks should be smoothed out to a distance on both sides of the nick of at least ten times the initial nick depth with no scratches visible under 10x magnification in any of the area smoothed. The minimum thickness of the wire at the point of maximum smoothing depth should never be less than 90% of the original dimension of the wire. If the wire has to be thinned more than that to remove the nick, the wire should be scrapped.
Corrosion is worse in that it involves more uncertainty. Depending upon its source and the resulting corrosion products it can change the molecular structure of the wire leading to the development of fault lines in the material eventually leading to cracks. A cracked wire will soon be a broken wire and a broken wire will spoil your entire day.
Carefully strip the wires of paint and inspect their entire length. If they are free of nicks and corrosion measure the wires along their length to assure that they aren't necked down as a result of excess tension or past smoothing of nicks. If they are corrosion free and constant diameter, refinish them, replace all the end fittings with new hardware and reuse them. It's a lot of work, so replacement may be your best option.
Enjoy your project.
A Travel Air Nut.