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Aviation History
1927
1927 - 0817.PDF
OCTOBER 20, 1927 riveted and bolted duralumin—no welding being employed It is remarkably light and lends itself readily to the fabrication of most of the members on a production basis. The spars consist of two main members of T-section one above the other—the lower one being inverted with the stem of the T upwards. These T-members are a special Sikorsky development, having small " bulbs " at the ends of the flanges (the head of the T) placed on the inside (toward the stem) By having these small " bulbs " tangent to the ends of the T-head on the side towards the stem a small flange results on that side increasing the moment of inertia about the vertical axis yet still leaving the top and bottom surfaces of the spar flanges flat and unobstructed for riveting or reinforcing plates. The stems of the upper and lower T-section members are joined by diagonal members riveted in place by a single rivet at each end, making the spar into a Warren truss. All rivets are duralumin, and chrome nickel bolts are used on the major assemblies. Drag bracing of the conventional type is employed, con- sisting of tie rods and compression ribs bolted to the spars, and of the same type of construction as the spars except that the flanges are perforated to reduce the weight. The ribs a production job—consist of cap strips and diagonal bracing members of duralumin channels riveted together to form a its tests, maintained an altitude of 1,500 ft., with a load of 2,500 lbs., on only one engine and was entirely under control. In the cabin type, the hull is 26 ft. long, 4 ft. 3 in. wide and 5 ft. 2 in. high. It has a 12° Vee bottom with a step slightly to the rear of the mid-point. As previously stated, it is built up of a hardwood frame to which are screwed varnished duralumin struts. Duralumin wood-screws are used, and at the chine and wherever the covering is reinforced, duralu- min rivets are employed. Steel tubular members across the hull are bolted in place and gusset plates are of duralumin, protected from corrosion by a special primer; the wood structure is finished with a coat of varnish. The frames comprising the internal hull structure are of both solid wood and built-up wood sections, reinforced with sheet duralumin, depending upon the stress at that point. The hull is divided into numerous water-tight compartments by struts of duralumin, which are so arranged that by remov- ing a few bolts one can easily crawl inside the hull to inspect or repair the structure. An opening is provided at the bow of the hull through which the pilot can drop anchor or effect a mooring when the boat is afloat. The cockpit, with side by side dual control, is in the front part of the cabin, just forward and below the leading edge of the top plane where excellent visibility in all directions vi \! Mix* \!/ \i) i SIKORSKY S36.B AMPHIBIAN 2 WRIGHT "WHIRLWIND* ENGINES SPAN 62' & 72 LENGTH 34' WING AREA 585 & 668S<JFT THE SIKORSKY S.36.B FLYING-BOAT : General Arrangement Drawings to scale. conventional type rib truss. The flanges of the channels of the diagonals are flattened at the ends to facilitate riveting. Where the diagonal bracing meets the cap strips, a simple duralumin fitting—interchangeable at all points—is used ; two rivets hold this fitting to the cap strip, while a third rivet is used to fasten diagonal braces to each fitting. All parts in the wing structure that do not come in direct contact with fabric covering are finished with a coat of varnish, while those coming in contact with fabric are protected by a primer. The outrigger carrying the tail is built up like a fuselage, of four longerons and cross bracing, of duralumin and of usual Sikorsky construction. It is attached at the mid point of the upper wing where two diagonal struts support it from the sides of the hull, while two struts also extend from the stern of the hull to a point about two-thirds from its forward end. Both elevators and ailerons are of the mitred type, operated by cables carried up from the cockpit to the wing and passing through the latter (to the ailerons) or along the bottom of the outrigger to the tail. The rudders are of the Sikorsky com- pensating type, that is they are cambered so that with one engine stopped the camber of each rudder—one in the slip- stream and one out of it—tends to counteract the off-set thrust of the running engine, thus giving complete control of the machine. It may be mentioned here that this arrangement has proved very satisfactory in practice, and the S. 36, during is obtained. Behind the cockpit are two seats, each com- fortably accommodating three passengers ; and behind these is a compartment for luggage. The cabin is equipped with an efficient ventilation system and is electrically lighted. In the open type, wind shields are provided for each cockpit. In the service type the petrol tanks are located in the top plane centre section, while on the long-distance types there are additional tanks behind each engine and in the nose of the hull. The principal characteristics of the Sikorsky S. 36 are :— Span (top) .. ,, (bottom) Overall lengthHeight on wheels . . Wing area Wreight empty Useful loadWTeight laden Loading per sq. ft. „ h.p. ..Speed range Cruising speedClimb (ground level) Ceiling Service Type. .. 62 ft. 0 ins. . . 18 ft. 1 in. . . 34 ft. 0 ins.. . 12 ft. 0 ins. . . 585 sq. ft. . . 3,950 lbs. . . 2,050 lbs.. . 6,000 lbs. .. 10-25 lbs. .. 13 lbs.. . 49-120 m.p.h. . . 100 m.p.h.. . 600 ft./min. . . 15,000 ft. Long-Distance. 72 ft. 0 ins. 24 ft. 0 ins. 34 ft. 0 ins.12 ft. 0 ins. 668 sq. ft. 4,400 lbs. 3,000 lbs.7,400 lbs. 11-1 lbs. 16-1 lbs.52-118 m.p.h 100 m.p.h.400 ft./min. 14,000 ft. 739
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