I ran across a tip for making turnbuckles in 1/32 scale, for Wingnut Wings kits. I haven't tried it, but I'll pass it on for what it's worth.
The components are a couple of pieces of wire and a Q-tip. The Q-tip has to be the kind with the hollow plastic stick. (I found them at Wal-Mart.)
Heat the Q-tip stick over a candle and stretch it, as though you were stretching sprue. When it cools, it will (according to the author of the original tip) still be hollow; you can control the diameter by changing the speed of yanking it.
Cut the tube to the length you need. Bend the wire to form the eyes that go on each end. (On that large a scale you may want to solder the eyes.) Cut off the eyes, superglue them into the tube, and you've got your turnbuckle.
Turnbuckles come in lots of shapes and sizes. You may need the type with a small hole for a Tommy bar in the middle, or the kind that's open on both sides, like the Grandt Line ones. You should be able to drill and/or file the barrel to the necessary shape.
Like I said, I haven't tried it. But it sounds like it ought to work.
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