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Aviation History
1921
1921 - 0714.PDF
••••>.•• The Supermarine '' Seal '' : Front view of the hull and centre-section, showing amphibian gear. - _,- aeroplane that will float. There is all the difference in the 'world between these two types, and if at times one may be apt to compare, perhaps unconsciously, the performance with that of a lighter machine, it should be realised that such comparison is scarcely fair to the builders of the boat, who have had quite different objects in view. Broadly £ peaking, there are two different ways of evolving a flying boat, and even then the final result will be two different types, according to the evolution followed. One is to start with a hull which one knows to be seaworthy, and then to put on to that hull wings and engines to give the best performance possible. The second method is to start with an aeroplane having the lightest possible notation gear, NOVEMBER 3, 1921 and then, as necessity arises, strengthen the structure and improve the seaworthiness of the flotation gear according to requirements. It will easily be seen that the final results of the two methods will still present fundamental differences, so much so that the two types, instead of being rivals, supplement one another, the one type being the more suitable where sea- worthiness and robustness of construction are the main desiderata, the other where performance is the most important feature. As already mentioned, in the Supermarine boats it has- always been strength and seaworthiness which have been first considerations. That is not to say that their per- formance is inferior. For instance, although few figures relating to the " Seal," Mark II, may be published, it is permissible to state that the maximum speed is in the neighbourhood of 93 knots, while the landing speed is as low as 39 knots, a very "good speed range indeed for a flying boat. From the accompanying general arrangement drawings (which, although somewhat sketchy, are approximately to scale) and photographs it will be seen that, as regards general outlines, the main innovation in the " Seal " is that the machine is a tractor. This change was somewhat of an experiment, as it changes the weight distribution very materially. However, the experiment has proved a success, with the result that the Supermarine Works can now provide boats of either type, according to whether the main load is required to be in the front or aft of the main planes, knowing that either type behaves satisfactorily on the sea and in the air. Incidentally this machine is, we believe, the first British flying boat to be designed as a tractor. As regards appearance the change is, we think, an improvement. The pusher always looks somewhat short and tubby, while the new tractor machine conforms more to usual designs and, therefore, looks more pleasing to the eye. Structurally, the " Seal " follows usual Supermarine practice, having a hull of approximately circular section, boat-built of planking over a light skeleton of timbers and stringers, and covered with fabric on the outside. As in previous Supermarine boats, the steps aie separate units, built on to the main hull. They form a double bottom, and are subdivided into numerous watertight compartments, so that in case of the hull striking some object floating in the sea there is no fear of sinking. Also, in case of damage, a step can be repaired or renewed without interfering with the main hull. In the Martlesham machine, it may be remembered, the combined tail skid and water rudder was mounted some distance forward of the stern. In the " Seal " it has been shifted aft to the sternpost, where it is much easier to provide the necessary strength and water tightness than it is with a rudder working in a trunk in the hull. Also the tail loads, which are very considerable, are lessened by placing the skid ait. An easily detachable shoe is fitted to the heel of the rudder, so that, as wear takes place, the shoe can be easily renewed. For reasons already mentioned, it is not permissible to refer in detail to the amphibian gear, beyond what can be gathered from the illustrations. It can be seen that the wheels and their strutting form a structure independent of that of the main hull. Thus, when alighting on the deck of The Supermarine " Seal : The machine coining on to the slipway. The wheels have not yet been lowered. 7*4
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