I once made a bong out of a 3 1/2 foot, 2.5in Inside Diameter acrylic tubing. I used a butane torch to bend it backwards and make a place for the bowl to sit. It was really nice but broke the base on it, and i'm lazy and haven't fixed it yet. Plus as anyone knows, it's only good for a party bong.
I still have a small straight acrylic bong, not the best but it gets me stoned.