How do you keep rigging wires tight on a 1/4 scale WW1 biplane?

Elastic works but it has a look you won't like on a warbird. I used the round beading elastic on a Pfalz a few years back and the tension stayed fine through cold and heat, but the stuff goes fuzzy and picks up a sheen after a season, and up close it reads as toy cord, not wire. If the wires are mostly for show at that size, you can do better without any turnbuckles at all.

What ended up on mine is stranded stainless fishing leader, the nylon-coated stuff in the 30 to 50 lb range. It doesn't creep the way mono-core braid does, wich is why your fishing line went slack in the garage. Mono stretches permanently under its own tension, especally with temprature swings. Leader doesn't do that. The trick for tensioning without turnbuckles is the old twist method. Pass the wire through a small eyelet at each end, pull it finger tight, then grab the middle with needle-nose pliers and twist it like a bread bag tie untill it sings a bit when you flick it. Snip the loop short and hit it with thin CA. Done right it stays taut for years and the tiny twist acutally looks like a jury-strut turnbuckle from a foot away.

For anchoring at the wingtips, don't rely on surface glue. Drill a 1/16 hole down into the tip rib, glue in a short piece of brass tube, and run the wire through that. Better yet, if you're still open to it, put a scrap plywood or hardwood block under the tip rib skin before you sheet, or shove one in now through the rib bay and epoxy it. A crimped sleeve or a loop back through the tube with CA keeps it from pulling out even if the plane gets bumped on the ground. Paint the leader with a flat grey or black sharpie and it disappears nicely against the fabric. Way cheaper than a dozen turnbuckles too.

That twist trick saved me on a Dr.I a couple years back, same deal with the leader from the tackle shop. One thing I learned the hard way though: put the twists in close to one end, not in the middle. Mine sat dead center and the pliers kinked the coating, which started a rust spot right where you could see it. Also, twist it, check it the next day, then twist again if it relaxed at all before you CA it. The first tension settles a little overnight and you don't want to be re-doing it after the glue is in.

I've used dead guitar strings on a couple of shelf queens and they stay taut for years. The lighter gauges are thin enough to pass for rigging at that size, and they come shiny, which reads as wire rather than cord. You can usually score a set free from any player you know once they're too dead for music.

One thing to watch though, steel picks up rust from finger oils if you handle it a lot. Wipe it down and hit it with a light mist of matte clear before you call it done.

Also, what'd you use for those spoked wheels? Been wanting to try that look on my own build.

I'd push back on the sharpie part of that first reply. The whole reason to run steel leader over cord is that glint it picks up when the sun hits it, and a flat black marker kills exactly that. Mine are bare and everyone at the field asks how I got the rigging so scale. If it reads too bright against the fabric, thinned dark dope on the covering around the anchor points does more for blending than dulling the wire itself. Also curious how that twist holds up when the wing gets flexed in transport, since the loop is locked at one length.

Update: went with the dead guitar string idea and it solved everthing. Grabbed a couple of light gauges off a buddy, and the shine relly does read as wire instead of cord. Ended up putting the twists near one end like the Dr.I guy said, and it made tensioning so much easier. Six months on the shelf and still drum tight.