Jetrader - January/February 2009 - 20

Metal & The Airplane By Bill Bath aviation history J The Junkers J 1 anuary 31, 1858: Isambard Kingdom Brunel’s great ship was ready for launching sideways at Millwall, London, and thousands of spectators lined the river banks. There is no doubt many expected it to sink, as the 690 ft (211 m) ship had a displacement of 32,000 tons with a double hull of three-quarter-inch (19 mm) wrought iron plates. After all, wood ﬂoated but iron clearly did not. Ahead of its time with a 24ft (7.3 m) screw propeller and 56ft (17 m) paddle wheels, it could in theory accommodate 4,000 passengers. Six masts with sails were the standby in the event that the ﬁve engines should fail. It did not sink, but although it was ahead, technically, of any ship aﬂoat, it was a commercial failure and ended its active life laying the ﬁrst transatlantic telegraph cable between Ireland and Newfoundland in 1865. It also laid the Suez connecting cable from Aden to Bombay in 1869-‘70. December 11, 1915: a small group of spectators huddled in a cold wind outside of a tin hanger in Dessau, Germany, staring at a strange looking airplane— the Junkers J 1, nicknamed the iron bird. No doubt some did not expect it to get airborne; after all, it weighed 2,200 lbs (998 kg), and unlike the wood-and-fabric biplanes parked around the ﬁeld, the top wing was missing with no wire bracing to hold the remaining wing in place. It not only got airborne but was 31 mph (50 km/ hr) faster than the Albatros LDD biplane. Furthermore, its wing loading compared favorably with that of the best airplane of its day—the Rumpler R.C.1. Plus, the J 1 had superior aerodynamics in both its lift-drag ratio and drag polars. Yes, it was actually fabricated from iron sheet—just .004 to .02 inches thick, (0.1 to 0.5 mm). These very thin sheets were stiffened by corrugated iron welded to the inside face, which created a rigid structure without external bracing and a smooth low drag form. The next stage of development by Junkers was to substitute an aluminum alloy for the iron sheet; the alloy was what came to be known as duralumin, which is an alloy of aluminum, copper (4.4%) and a small amount of magnesium (1.5%) and magnanese (0.6%), developed in 1909 by Alfred Wilm, a German metallurgist at Dürener Metallwerke Aktien Gesellschaft (successor to the German War Munitions Factory). He had found accidentally in 1903 during a search for a way to strengthen aluminum that after quenching a heated alloy of aluminum and copper on a Friday afternoon, there was only a minor change in an increase of hardness. When 20 The ofﬁcial publication of the International Society of Transport Aircraft Trading

Jetrader - January/February 2009

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