Popular Woodworking 2003-06 № 134, страница 69
and instructor pilots we have gathered to recreate this historical event - the flights of the first fully controllable airplane. As simple as this glider looks, it takes great skill to fly. An errant wind gust, incorrect control input, a moment of inattention and the plane will dive for the sand. This is just what is about to happen to Santa. He lets the nose get a little too high, the glider slows and loses flying speed. Suddenly the nose drops and the glider begins to fall out of the air sideways. The left wing tip catches first, wrenching the entire structure of the plane. The spars bend and keep bending as the aircraft crunches into the sand. Those of us who built this replica watch horrified as the plane seems to fold in half. We are waiting for the loud cracks that will announce the destruction of the wooden frame. But the loud cracks never come. The glider skids to a stop then suddenly springs back into shape. Both the aircraft and its pilot are unharmed. We have just learned something important about the genius of the Wright brothers. They understood their materials intimately. Properties of Wood Orville and Wilbur Wright were skilled woodworkers. Their mother was the daughter of a carriage Learning to fly all over again, Capt. Jim Alexander (USAF) plows the sand (above).Alexander is one of the Air Force's top instructor pilots and is more at home driving an MC-130 Shadow. Wright historian Louis Chmiel and a volunteer repair the damage to the canard after a hard landing (left). maker and she learned to work wood from her father. She passed this knowledge on to her sons and they made good use of it. Their home, which is preserved at Greenfield Village in Michigan, showcases some of their handiwork - a carpenter gothic porch, an ornate mantle, a hand-carved cherry staircase and several pieces of their furniture. They applied this expertise to their aircraft. Wood, because it was relatively light and reasonably strong, seemed the natural choice for early aircraft builders. But there was more to it than that. Airplanes must withstand tremendous stresses. The wings must lift not only the weight of the airplane, but also that of the flight crew, passengers, luggage and fuel. In a banked turn, these loads go up precipitously due to centrifugal force. When using wood to engineer structures like these, you must consider three important properties: • Compressive strength - how much stress a wood species can stand parallel to its grain. • Bending strength or modulus of rupture - how much load a wood species will take perpendicular to the grain. • Stiffness or modulus of elasticity - how much the wood deflects or flexes perpendicular to the grain before it breaks. The Wright brothers chose to build the frames of their airplanes from ash and spruce: ash for the bent parts and spruce for the straight ones, as a general rule. Although they probably based their decision on traditional woodworking lore rather than scientific data, it was a good choice. If you check the tables of "mechanical properties" in the "Wood Handbook: Wood as an Engineering Material" compiled by the U.S. Department of Agriculture, Forest Service, Forest THE 1902 GLIDER The in-flight photos you see in this story were taken of the 1902 Glider, the precursor to the 1903 Flyer, which we are building now. The Wrights flew thel 902 Glider at Kitty Hawk almost 1,000 times between September and October 1902, with flights up to 622 feet and durations of up to 26 seconds. Stored at Kitty Hawk throughout the winter, they used this glider for practice in 1903 while building the powered airplane. popwood.com 67 |
