Schauberger
[6] In regard to the carrying capacity of wooden pipes, the following passage from a book 'The Australian Wood Pipe Company' (p. 21, publ. circa 1910) provides interesting insights. "It is conceded that smoothly-planed timber has the lowest coefficient of friction of all materials ordinarily employed for conveying water. Many extensive experiments have been made on the flow of water in various kinds of pipe operating under many conditions. Within the last few years, the United States Department of Agriculture has carried on a very extensive series of experiments on the flow of water in Wood-Stave Pipe, and attention is called to their Bulletin No. 376, and in particular to the conclusions therein: Conclusions. 'That the data now existing does not show that the Capacity of Wood-Stave pipe either increases or decreases with age. That wood pipe will convey about 15 per cent more water than a ten-year-old cast iron pipe or a new riveted pipe, and about 25 per cent more than a cast iron pipe 20 years old, or a riveted pipe ten years old.' The conclusion of Government experiments, as given above, definitely prove that the carrying capacity of Wood-Stave Pipe is from 15 percent to 25 per cent greater than metal pipe, with the additional advantage that Wood-Stave Pipe will remain smooth and clean internally throughout its entire life."- Ed. [The Energy Evolution - Harnessing Free Energy from Nature, The Transport of Ore in Double-Spiral-Flow Pipes]