They say it was the 18th-century English essayist Horace Walpole who coined the word "serendipity", to denote the faculty of making lucky and unexpected finds by accident. I experienced the phenomenon in action a night or two ago: I discovered what happened to Herr Anton Flettner.
Flettner has featured in "Weather Eye" before. He was, you may recall, a talented engineer who, early in the 1920s, proposed to harness the well-known "Magnus effect" in fluid dynamics to provide the necessary power for sailing-ships.
The "Magnus effect" is what happens when a horizontal flow of air meets a solid cylinder mounted so that it rotates about a central vertical axis. The air, first of all, divides to try to pass on either side of the obstruction.
However, those particles of the fluid tending to pass the cylinder on the side whose surface is moving into the wind find their progress frictionally retarded, while the air expecting to pass on the side moving with the wind is assisted in its passage. Because of this asymmetry, the moving air quickly develops a preference to pass the cylinder on the "assisted" flank, and with more air on one side than the other, a pressure difference develops.
The pressure difference results in a force acting on the cylinder in a direction at right angles to the wind, and if such a device is mounted on a ship, it acts like a sail.
Flettner put his notions into practice. In 1926, he bought the schooner Bruckau, installed two 50 ft electrically-powered revolving towers, and found that his idea worked delightfully. After a few trial runs he headed for the US, and in May that year the "rotor-ship", now renamed Baden-Baden, entered the harbour of New York to nationwide acclaim.
But the idea never quite caught on, and few, if any, other rotor-ships were built. Baden- Baden itself was sold, its cylinders removed, and it ended its life converted into a humble tramp to ply the Caribbean. I never knew, however, what happened to Herr Anton Flettner.
But now, with serendipity, I do. From 1926 to 1945 he was president of the Anton Flettner Aircraft Corporation in Berlin. There he designed and built one of the very first helicopters, the Flettner FL-282 Kolibri, or "Humming Bird", of which several dozen were built and used by the German forces during the war.
After the second World War, Flettner emigrated to the US where he continued to work in the development of helicopter design, in due course establishing his own company again: a second Flettner Aircraft Corporation. He died in New York, aged 76, on November 29th, 1961.