[Bicycle Bob]

Official "flying wires" are flat, and not even coiled for shipping. There is a problem with flutter if they get too streamlined, though. Helicopter blades carry heavy ballast in the leading edge to keep them stable. One of the Kremer prizes was won by a flight with a pair of the thin piano wires left off, running from mid-wing forward.
What always astounds me, however, are all the round-section rollover bars on race cars. They are often extra-tall and wide, yet poorly braced, and with no attempt at streamlining. A foam fairing of the shape shown above would not be hard to do, and even a simple cardboard tail taped on would more than halve the drag. Even terrible paint would help, like the dimples on a golf ball. There are often other round bits hanging out in the breeze, too. Both the Goldenrod and Challenger used the same truck axle which left a large stub sticking out of the hub. The stubs could have been streamlined with a fairing on a bearing, like those non-rotating bling-bling wheel covers.