Donald Jacobson, veteran Thingiverse contributor, enjoys building with PVC pipe. He was troubled, however, by the fact that after about a foot in length, the pipe becomes somewhat floppy. He decided to bundle pipes together in order to create a stronger construction. His first effort was a bundle of three but that created some problems with geometry so he moved to using a bundle of four pipes. Trying out the strength of his bundle using zip ties, he found the reinforced PVC group to be satisfactorily strong. He then set about creating a 3D printed connector using TinkerCAD so that he could easily group the pipes and attach them to a perpendicular set. Read and see more at: http://3dprint.com/84284/pvc-pipe-construction-kit/