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Aviation History
1914
1914 - 0213.PDF
FEBRUARY 28, 1914. for a distance of about 6 ins. each side of the boat, the pilot has a very good view in a downward as well as all other directions. From the passenger's seat an even better view is obtained. The controls are of the Wright type, consisting of two levers, one of which controls the warp and rudder simultaneously, whilst the other operates the elevator. The general dimensions are :— 30 ft. 6 ins. Gap 7 ft. 41 ft. 4| ins. Weight 2,050 lbs. 33 ft. 4§ ins. Speed 75 m.p.h. S ft. 6 ins. Area 373 sq. ft. The Benolst Flying Boat. The Benoist flying boat represents an entirely different practice in flying boat design from that employed in the Curtiss and Burgess types. The respect in which the difference is mostly manifest is one of weight disposition, for whilst the two types mentioned above have the engine placed up be- [/ycHTj Length ... Span, upper plane Span, lower plane Chord tween the main planes in order to raise the centre of gravity, the Benoist has the engine situated well down in the hull of the boat. The Benoist flying boat. This, of course, gives this machine a comparatively low centre of gravity, and while this may, or may not, be a disadvantage in flight, it certainly renders the craft very stable on the water, and in modern machines, such as the Morane-Saulnier " Parasol," we have seen that a low e.g. is not prohibitive for good flying qualities. The boat itself, which has a length of 23 ft., is built up of double spruce planking over a skeleton of spruce longitudinals and ribs. In the nose of the boat the bottom is swept upwards in order to assist the boat in getting into its skimming position in the shortest possible time. A single step, 5 ins. high, occurs at a distance of 9 ft. 8 ins. from the nose of the boat, and from the step to the stern the hull slopes upwards as well as tapering to a vertical knife's edge carrying the rudder. The deck is swept downwards very abruptly from the occupants' seats to a point behind the rear plane struts, in order to provide sufficient clearance for the propeller. In front of the seats is a cowl, formed by a structure of spruce stringers covered with canvas, the purpose of which is to protect the occupants from wind and water spray. The method of mounting the engine is very interesting, as it serves at the same time to very materially strengthen the boat. Two strong spruce beams running parallel to each other practically the whole length of the boat serve as a support for the engine, and are spaced a distance apart sufficient to take the crank case arm bolts. The length of these beams is 17 ft., and in front of the step and under the engine they have a depth of 16 ins., and a thickness of two ins. From the step backwards they taper gradually to con form to the shape of the hull, and have been carefully proportioned for the various loads. Wherever possible, they have been lightened by hollowing them out. The engine drives through a chain trans mission a single propeller situated behind the rear plane struts. The sprockets on the engine-shaft and propeller-shaft are of the same size, so that the gearing is 1 to I. A tubular steel chain guard is fitted, and incorporated with it is a tubular radius rod which takes the pull of the chain, and provides easy adjustment of its length. This radius rod floats on ball-bearings at both ends. The tubular steel propeller-shaft is mounted between the main planes some 18 ins. below the trailing edge of the upper plane. Both ends of this shaft are carried on large combined radial and thrust bearings, which in turn are mounted on cast bronze retainers strongly supported to the central members of the cellule. Spruce struts tunning diagon ally down to the leading edge of the lower plane, where that member joins the longerons of the boat, take the thrust reaction and preserve the rigidity of the rear bearing mounting. The propeller-shaft extension is fitted with a transverse pin, so that the engine can be started by the insertion of a starting handle. This operation is easily performed from either of the occupants' seats. The main planes, which are rectangular, as seen in plan, are both of equal span, and are built up in sections to facilitate transport. To the trailing edges of the outer sections of both planes are hinged ailerons of 8 ft. length, and a width ot 1 ft. 8 ins. Mounted some distance above the deck of the boat is a fixed stabilising plane, to the trailing edges of which are hinged the two elevator flaps. The rudder is hinged to a post forming an extension of the stern post of the boat. A small portion of the rudder projects below the bottom of the boat, and serves as a water rudder when the machine is taxying on the water. The control levers are situated in front of the left hand seat (the seats are arranged side by side), and consist of a universally mounted lever operating the ailerons and the elevator. Another lever actuates the rudder by a to-and-fro movement. The fuel tanks are placed in the hull on one side of the engine, and have a capacity for at least four hours' flight. All control cables are in duplicate, and are carried inside the hull, from which they emerge through a brass ferrule in the crown of the after deck. The general dimensions of the Benoist flying boat are :— Span Chord Gap Length ... 35 ft- ... 5 «• ... 6 ft. ... 26 ft. Length of hull Weight, empty Speed, fully loaded 23 ft. 1,190 lbs 64 m.p.h (To be concluded next week.) ® ® ® © "PROPELLERS"—THE DISCUSSION. IN opening the discussion on Mr. Bramwell's paper at the recent meeting of the Aeronautical Society, Mr. North commented upon the fact that Chauviere had said that the quality of the wood and other factors caused a variation of as much as 3 per cent, in the propeller efficiency. Mr. Holdberg retailed some of his experiences with model pro pellers, and remarked that although in static tests with two propellers, the acting face of one being inclined forward, while that of the other leaned towards the rear, he had found considerable differ ences in their performances, yet in actual flight on model aeroplanes their efficiencies were practically equal. He said that he had obtained some very excellent results with propellers made simply by steaming the trailing edge. Mr. Low congratulated the author upon his remark that the only essential in using the equations given in his paper was that the units employed must be consistent among themselves. He thought that it would be a great advantage if the results of the investigations recorded in the Report of the Advisory Committee for Aeronautics were detailed in some consistent system of units. Mr. Bramwell had drawn attention to some values of the variation in pitch for zero thrust taken from the Koutchino Laboratory Bulletin, which showed a variation of 2-5 per cent, between the successive readings given ; he would like to say that this variation seemed to increase with speed and indicated that the pitch for zero thrust was an in creasing function of the angular velocity of the propeller. Dr. Glazebrook said that he thought Mr. Bramwell had given a very excellent paper. One of the reasons why the N. P. L. had undertaken experimental research on propellers was that there was not a great deal of money available for that purpose amongst private manufac turers, and he commented upon the excellent results which had been obtained with propellers of even the crudest design. He observed that the units employed in the Report of the Advisory Committee were those which he had been informed would be of the greatest value to the industry, but he would very much like to see a con sistent system adopted. Dr. A. P. Thurston, after pointing out the differences in the mode of progression between an aerofoil and a propeller blade, asked the author whether any experiments had been made as to the improvement that might be obtained by the use of baffle plates, such as had been already employed in marine work. The author, in his reply, said it was sometimes disheartening to find such remarkable efficiencies given by some propellers, and was not at all surprised that propellers made in the manner mentioned by Mr. Holdberg had done so well. He stated in reply to Dr. Thurston that so far they had not undertaken any such work, but had endeavoured to keep the propeller as free as possible from the effects produced by baffling or disturbing surfaces. 213 C 2
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