The Airplane - Jay Spenser [39]
To see why this is the case, imagine that you pass through the door of an unfinished house and find yourself standing on a long, narrow section of wooden flooring. This floor is structurally similar to Henson’s wing panel because its fore-and-aft joists serve the same function as the wing spars while its transverse floorboards act structurally like wing ribs.
Wooden floors built this way are safe to walk on because their joists are supported at both ends. Imagine for a moment, though, that this particular section of flooring—a narrow swath encompassing two joists—is supported at only one end. The joists come out of the wall below you and extend forward, and the floorboards run from left to right.
As you walk out from the wall, you find that this freestanding span supports your weight all the way out to the tip. As your weight reaches the unsupported end, you find it scarcely bends beneath you like a diving board. The reason is that bound joists and floorboards form a beam structure that resists fore-and-aft or spanwise flexing.
Unfortunately, though, you also discover that the farther you go from the wall, the more this freestanding section of floor twists and tilts to one side or another under your body weight. Only by holding to the center and balancing carefully can you keep this lateral flexing from sliding you off to the side. The reason is the poor resistance to chordwise flexing of thin, cantilevered panels, be they wings or flooring.
Here in a nutshell was the thorny problem confronting Henson and the other early wing designers: while bird-like wings could be made that wouldn’t flex or snap off, they could not be made resistant to twisting. Henson’s design solution was to use external bracing wires strung along vertical posts mounted on the aircraft’s wings and fuselage. These bracing wires ran all the way out to the tips of the Steam Carriage’s wings to keep them rigid. Still more wires reinforced the tail.
Henson’s engineering was a little squirrelly, but basically he was on the right track. Of course, none of this—not beams, spars, or trusses—was new, as one glance at a sailing ship will confirm. Henson merely appropriated existing pieces of maritime technology in his effort to sail the heavens.
Aviation would put this idea of external bracing wires to good use, as the Antoinette, Blériot XI, and other pre–World War I monoplanes show. But the world’s first successful airplanes would be biplanes, not monoplanes, and the reason takes us Down Under.
Lawrence Hargrave first saw Australia as a boy of fifteen. The second son of an immigrant British family, he was an adventurous youth who spurned conventional studies. Instead he pursued a marine engineering apprenticeship that let him join maritime expeditions of discovery.
His new world was a panoply of tropical heat, groaning timbers, and billowing sails. Porpoises breached the pristine seas in quicksilver arcs. Violent squalls descended with little warning. Waves crashed loudly over coral reefs, their foam visible even by moonlight.
All of it fascinated Hargrave, whose interest in the natural world recalls that of Charles Darwin aboard the HMS Beagle earlier that century. In addition to circumnavigating Australia, Hargrave visited New Guinea several times, exploring its coastal waters and headlands. It was a hard and dangerous life.
On one voyage, a storm set the ship adrift by tearing off its rudder. To the relief of all, Hargrave improvised a tiller out of a capstan. Then a worse storm ripped the luckless ship asunder, claiming many lives. Hargrave survived by clambering desperately up a mast as the ship slipped beneath the waves. A lifeboat risking all in the heaving seas plucked him to safety.
In 1876, this young man joined