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Aviation History
1920
1920 - 1275.PDF
DECEMBER 16, 1920 this purpose, is operated by the impact of a weight slidingdown the drogue wire, and can be described as follows : The bridles for the drogue are held by four hooks pivotedon the body of the slip, and jrijich in the normal position are guarded, as shown in theaMbre, to prevent the bridles when dropped from about 75 ft., though the slip is severalfeet under water. The extension of the drogue wire passes through thebottom of the drogue, which is secured to it at this point, so that when the bridles are slipped the drogue turns inside AtftALL STCPPlU WlftCID TtMM l> oume T*HCM sroffUL TAKU V? C-1TW TO H«R)«4 PQI«rr or AJRSHIP «ntL from becoming unhooked when the drogue is dropped.These hooks are held nn position by extensions or arms with hooked tongues fitting over the rim of a cup slidingon the central guide. The cup is held up by a strong spring, and has a projecting top which is struck when the weight FIG. VI. Fig. VI.—Arrangementof improved S.O.B. Slip. 1, Drogue in positionfor use ; 2, Drogue," slipped " ; 3, vertical section ; 4, Horizontal section through A-A. is released and slides down the wire. When the weight hitsthis projection the cup is forced down against the spring. out, enabling it to be drawn out of the water. This fittingwas found necessary owing to the fact that the large drogues used hold from 4 to 5 tons of water, and would either haveto be cut adrift or lifted bodily out of the water, which is inadvisable owing to the alteration of trim and waste ofballast necessitated. The pull in the drogue wire is transmitted to the ship by means ofa ball-stopper wedged on to the wire, which takes up against a block secured to the mooringpoint with a wire strop seen in Fig. 7. As soon as the pilot decides to ride to a drogue,the required length of wire is reeled off the drum and the ball-stopper wedged securely ata distance from the drogue corresponding to the height at which it is desired to ride,allowing a margin for the sag in the wire. The wire is paid out in a loop from the bows,keeping the drogue still in the ship, until the stopper comes up against the block attachedto the mooring point. The drogue is dropped when the ship isabout 100 to 150 ft. above the water and carrying as little way as possible. As theship drifts with the wind the drogue, by being towed through the water, fills, thus keepingthe bows of the ship into the wind. The drogue, of course, does not hold theship stationary over the water, but retards its drift to such an extent that even in strongwinds the drogue wire can be picked up by surface craft and made fast for towing.Experiments were carried out by " R.o. " and " R.23 " over the Wash with drogues in1918, and it was found that it was only advisable to ride to a drogue in cases of emer-gency, until some satisfactory arrangement was made to enable the ballast bags to befilled fast enough to counteract the lightness caused by superheating. The airships in bothcases were successfully taken in tow by a motor-boat, and the drogue wire secured toa buoy, thus showing that in the case of a broken-down airship at sea it is not a difficultmatter to salve her. This brings up the question of long-distanceairship towing by surface craft. In July, 1919, " N.S.7 " was towed fromNewcastle to Southend by H.M.S. Furious, steaming at 17 knots, and although the tow-rope parted once owing to a faulty splice, a line was lowered ' and the rope hauled up and made fast again. In winds thus releasing the arms, which immediately fly outwards, of over 30 m.p.h. the airship kited when H.M.S. Furiousdue to the strain on the hooks, and the bridles are slipped. It has been found that an 8-oz. weight will spill the drogue was not under weigh, but it was possible to counteractthis by running one engine slowly. 1377
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