Every once in a while, someone will mention building a bridge or some other thing using railroad rail for strength. Rail is far more flexible than most people think, Many people are only familiar with short lengths, but long pieces are different. 
Watch this video from about 6:15 to 7:50. It is a telephoto view that exaggerates the flexibility, but is still surprising.
Bruce
Watch this video from about 6:15 to 7:50. It is a telephoto view that exaggerates the flexibility, but is still surprising.
Bruce