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Curtiss Model H-12 flying boat

A number of Curtiss flying boats have been built, but one known as the Model H-12, which was turned out a few months prior to the time the United States declared war, was the largest craft of its kind that had been adopted by the naval forces in the US. This model is the same as that of a number of flying boats built by the same company.

The machine has a span of 75 feet 10 inches on the upper wing, the lower wings measuring but 48 feet. A modified R.A.F. No. G wing curve is employed set at a dihedral angle of 1 degree and with an angle of incidence of 4 degrees. The chord is 7 feet and the gap 7 feet, the total supporting surface being 858.10 square feet. Flat steel tubing is employed for the leading edge of the wings, the upper plane consisting of five sections. The wing beams are of I-section spruce, the compression ribs are of solid pine, and the remaining ribs are of pine, birch, and spruce. Ailerons are used on the upper wings only and measure 15 feet 3 inches long with a maximum width of 4 feet. Each has an area of 46.8 square feet. To prevent side slipping, vertical fins are placed above the outer pair of struts on each of the upper wings. These fins, or keels, have an area of 12 square feet each.

The lower planes are built in four sections, each of the outboard sections measuring 19 feet in length. The central sections consist of extensions projecting 3 feet from either side of the hull and are built rigid enough to walk on. They are covered with rubber matting and are designed to give access to the motors. The inter- plane struts are stream-lined sections of heavy spruce, 4-1/2 by 1-1/2 inches, of the same thickness throughout, though the supporting struts for the motors are tapered from the ends toward the center.

The stabilizing plane, the elevators, and the rudder are carried on an outrigger supported at its outer end by struts rising from the stern of the hull. The horizontal stabilizer measures 16 feet across its trailing edge and has a chord of 6 feet 3 inches, giving it an area of 63.9 square feet. It is of the non-lifting type, being in the neutral position when the machine is horizontal, and is placed at the center of propeller thrust. The elevators have an area of 49.8 square feet, while the tail fin has an area of 34.9 square feet. The rudder is of the unbalanced type, has an area of 31.2 square feet, and has a height above the hull of 8 feet 9 inches.

While the hull has accommodation for five people, two cockpits are fitted and they have dual Deperdussin control, the control bridge being of the usual inverted U type and made of ash. The control wheels are 16 inches in diameter. One ami one-quarter revolutions of the control wheel move the ailerons through an arc of GO degrees, one-half above and one-half below the upper wing line. The rudder has equal range of movement, but through the multiplying gear employed this is reduced to an arc of 45 degrees at the rudder controlling bar.

Two Curtiss eight-cylinder V type water- cooled 100-h.p. motors drive 8-feet 3-inch propellers in opposite directions. Both motors are provided with electric starters, the pinions of which engage an 18-inch gear wheel just back of the propeller hub, though cranks are also fitted for hand starting. The latter protrude through the radiators, which measure 29 by 2'2 by 3$ inches and are mounted 3 inches forward of the motor struts on brackets attached to them. Each radiator weighs 70 pounds and 80 pounds of water are carried.

The hull has an over-all length of 34 feet 3 inches with a maximum beam of 4 feet just at the leading edge of the planes. A 6-inch step is placed 14 feet 1 inch aft of the forward perpendicular, the center line of the forward main beam of the lower plane coming just 20 inches forward of the step. Ash framing and keel with sides of mahogany and cedar and a covering of canvas are used in the construction of the hull. The cockpit is about 7 feet long and is divided into two sections. The forward section contains seats for the two pilots and the instrument board, while the sifter section seats two passengers. About 4 feet farther aft i- another one-man cockpit for the accommodation of a mechanic. The wing floats are 7 feet long, 18 inches wide, and 19 inche- deep and are built up of ash frames internally braced by steel wire and covered with light veneer. Their displacement in fresh water when completely immersed is 800 pounds.

The machine proper weighs 2240.1 pounds while the power plant adds an additional 1316.5 pounds; fuel and oil for a flight of five hours represent a weight of (520 pounds; and the weight of the electrical equipment is but 70 pounds. Complete with seats, instruments, and accessories, the hull weighs 885 pounds. The net weight of the complete machine is 3556 pounds and it is capable of carrying a useful load of 1100 pounds. The loading per square foot of lifting surface is approximately 5.5 pounds.

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