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Aviation History
1925
1925 - 0045.PDF
JANUARY 22, 1925 the pilot and passengers to be located at the centre of gravity, thus improving and simplifying the balance of the machine. In this connection, also, the tail surfaces get more pronounced downwash, a feature considered to be desirable in the case of flying-boats. For the present a six-cylinder Anzani type 6A3 engine is fitted, as there are not yet any engines of this type made in America, but provision has been made in the design of the engine installation for the fitting of any radial engine of about the same weight and horse-power. In general construction and design—apart from the arrangement of the power plant and the pronounced stagger— the model EO follows Aeromarine practice. The wings are built up of spruce I-section spars, with spruce trussed ribs and spruce drag struts. All the fittings, of which there are comparatively few, are of steel. Owing to the large stagger the drag bracing in the top plane is double as far as the strut fitting. The lower plane has a single spruce and plywood box spar, which is attached to a steel tube passing through the hull and interconnecting the port and starboard panels. The attachments at this tube and at the outer V-struts are designed so as to resist any torque that may be produced in the wing panel at high speeds or during a dive. Provision is also made in the strut attachments for adjusting the angle of incidence of the lower plane, either for varying the fore-and- aft balance of the machine or for balancing the propeller torque. Aeromarine No. 2B wing section is employed for the top plane, and Aeromarine No. 6 for the bottom. Long and narrow ailerons are fitted to the top plane, and the control is so designed that pulleys are entirely eliminated, and all cables rnn in straight lines without any guides or fairleads. The control stick is connected by push-and-pull rod with the countershaft located at the rear of the seat, while the lever on the countershaft is connected by cables with the control horns on the elevators. The stick itself is mounted on a torque tube running fore and aft in the hull, and carrying the lever for operating the ailerons. The latter are provided with extension torque tubes, at the inner ends of which, alongside the engine nacelle, are crank levers, which in turn are con- nected by streamline push-and-pull rods to the torque tube in the hull. All the joints of this control ' gear are readily accessible, as is also the countershaft in the hull, which is protected' by a hinged cover from interference with the passengers. Wing-tip floats, made of 17s aluminium alloy and weighing 7J lbs. each, are fitted to the lower plane. In designing the hull the main considerations were good seaworthiness and take off, and easy landing. Its lines are based in general on those of the Aeromarine model AMC hull (described in FLIGHT for Nov. 22, 1923), except that certain modifications and improvements gained from experience with the AMC hull have been incorporated. The most important of these is the pronounced V-bottom—the angle with the horizontal on each side of the keel being 18° at the step and 28" halfway from the step to the bow ; from the step to the stern the angle is uniformly 18\ The rear portion of the hull has a slight upward sweep in order to bring the tail surfaces clear of the water and also to shorten the tail bracing. The large reserve of buoyancy provided and the upward sweep of the rear bottom give a rather short waterline, resulting in exceptional manoeuvrability. It has been found that the minimum turning radius in taxying is about its own span (38 ft.), and that in turning, instead of burying its outer wing-tip float in the water—as often occurs with flying boats— it banks itself towards the centre of the turn owing to the reaction effect on the sharp V-bottom. In construction the hull is built up of 17s aluminium alloy sheets and stamped shapes. The framework consists of a series of frames and fore-and-aft stiffeners spaced to give the correct support to the sheet-metal covering, which is riveted to the framework. All the stiffeners and frames in the cockpit are of equal U-shape section, while the frames in the enclosed compartments are of Z section. The hull is divided into four watertight compartments, excluding the cockpit, and aluminium alloy tubes passing through these compart- ments carry the control cables without affecting their water- tightness. The seats are built in the hull permanently, and provide excellent comfort for pilot and two passengers. The pilot's seat is slightly forward of the passengers' seats. The view from the seats downwards and all round is excellent, although the top plane, naturally, somewhat restricts the view directly upwards. In order to facilitate handling the boat on shore a watertight tube is provided across the hull just forward of the step to receive an axle and wheels, which may be seen in situ in the accompanying illustrations. As previously stated, the complete power plant is assembled as one unit in a streamline nacelle. iThe latter is built up of sheet 17s alloy, and carries the fitting for the attachments of the nacelle support struts, for lifting the machine, and for the attachment of the upper wings. A combined petrol and oil tank is located between two bulkheads in this nacelle, one of which is situated at each of the wing spar attachments. The oil section of this tank is placed immediately behind the front bulkhead, and serves to isolate the engine from the petrol supply. The petrol tank is divided into two parts, a service and an emergency section, and has a capacity of 25 gals., or sufficient for more than four hours' flying at full throttle. The engine itself is bolted to the front bulkhead of the nacelle, which is of ^V-in. thick 17s alloy. The magneto, oil pump, and tachometer drive project inside the nacelle, where they are well protected from the elements. Short petrol piping under the nacelle connect the carburettor and petrol tank, while the cocks under the tank can be reached from the pilot's seat during flight. The tachometer, mounted on the side of the nacelle, and the oil gauge are both in full view of the pilot. The following is a specification of the Aeromarine Model EO:— Span (top) .. 38 ft. Span (bottom) 34 ft. Chord (top) 5 ft. Chord (bottom) ft. O.A. length ;. 25 ft. 2 ins. Angle of incidence .. .. .. .. 3 • 5°-5° Dihedral (bottom) 3-5° Aera of main planes . . . . .. .. 266 sq. ft. Area of tail plane .. .. .. .. 20-5 sq.ft. Area of elevators . . .. . . .. 12-1 sq. ft. Area of rudder .. .. .. .. 10 sq. ft. Area of fin .. .. .. .. .. 5-5 sq.ft. Stagger (leading edges) .. .. .. 3 ft. 5 ins. Weight (emptv) • . . 1,040 lbs. Useful load ". - .. 710 lbs. Weight loaded 1,750 lbs. Weight per h.p 23-3 lbs. Weight per sq. ft 6-58 lbs. THE CAMBRIDGE UNIVERSITY AERONAUTICAL SOCIETY THE following is a list of lectures to be given before the Cambridge University Aeronautical Society during the Lent Term. The lectures take place at 8.30 p.m. in Lecture Room " D," Free School Lane, Cambridge :— January 21.—Professor B. Melvill Jones, M.A., A.F.R.Ae.S., A.F.C. : " Flying within Clouds." January 28.—Professor L. Bairstow, F.R.S., C.B.E. : " The Aerofoil : a Search for a Theory." February 4.—Wing-Commander Sholto Douglas, M.C., D.F.C., p.s.a. : " Air Fighting." February 11— W. S. Farren, Esq., M.A. : " The Process of Aeroplane Design." February 18.—Air Chief-Marshal Sir H. M. Trenchard, Bart., G.C.B.. D.S.O. : (Subject to be announced later). February 25.—H. Ricardo, Esq., M.A. : (Subject to be announced later). March 4.—Alan Chorlton, Esq. (Managing Director of Messrs. Beardmore, Ltd.) : " The Ail-Steel Aircraft." March 11.—G. Bradshaw, Esq. : " The Failure of the Petrol Engine as a prime mover." Presidential Address. Election of Officers. (Date to be announced later.) Visit to the Airship R 33. (Date to be announced later.) An exhibition of trick flying will take place. (Date to be announced later.) If time permits four cine- matograph films will be shown. A 4 45
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