Testing The New Uprights - Wednesday, February 4, 1903
The History: Octave Chanute has been on a cruise to Egypt and Europe with his two daughters. Before departing he wrote Wilbur that he would enjoy receiving a letter from him while he traveled. Wilbur obliges and writes Chanute to keep him current on the progress of the Wrights' work on their new machine.
The brothers have conducted some new experiments, varying the shape of a 2-foot (length) by 7/8 inch (width) by 1 1/2 inch (depth) stick. They had shaved these posts into different shapes. Through these experiment they hope to determine the shape of the uprights for their new machine (the Wright Flyer). The shape they seek should produce the least amount of air resistance (drag). Their new machine will be twice as heavy as their glider. By reducing the drag on their new machine they will need less power (less thrust) and a smaller engine. In general a smaller engine will weigh less as well.
Wilbur confesses that their results were not exactly what they expected. Wilbur reported, "... rounding off the rear corners increased the resistance nearly 5 percent [5%]; while rounding the front corners reduced it to less than one half. Rounding both front and rear brought it down to about one third [1/3]. A surface ... rounded in front and tapering toward the rear gave a resistance of nearly one half [1/2].
Wilbur shares with Chanute that they are in the middle of a terrible winter blizzard and telegraph communication is down in Chicago. "We envy you the sunny skies of Italy", acknowledges Wilbur. He also tells Chanute he has contacted Mr. Warder from the Western Society of Engineers and conveyed that the Wrights will have a paper ready for the Society in June.
Why did the Wrights think shaving the rectangular sides of the sticks into curves would reduce the drag? Recall, their wind tunnel tests of 1901 in which they tested airfoils (wing shapes). The shapes with less drag (air resistance) were curved.
Quotation from the book The Papers of Wilbur and Orville Wright, Volume 1 by M. McFarland.