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Aviation History
1924
1924 - 0562.PDF
m ^T ( EfiJG/£E£*. J] SEPTEMBER 11, 1924 MOORING DIRIGIBLES AT SEA An Interesting Experiment with the U.S. Airship " Shenandoah" IN our issue for August 7 last we made brief reference to an experiment which was to be carried out by the U.S. Navy, the object of which was to ascertain whether the U.S. rigid airship Shenandoah could be moored to a moving ship at sea. We have received from the Naval Air Station at Lakehurst, N.J., a brief report on this experiment, which we publish herewith, together with illustrations of the actual test. This experiment of anchoring a rigid airship to a mobile mast was carried out under favourable air conditions during the evening of August 8, when the Shenandoah, acting under instructions from the Bureau of Aeronautics, proceeded from Lakehurst to the " Patoka " lying in Naragansett Bay. The arrangements laid down for carrying out the manoeuvre embraced two schemes, one analogous to the method of mooring to a land mast and the other, which will in all proba bility be adopted as the standard, being a variant of the first, differing only in the method of receiving the ends of the yaw guys. The main lay-out was as follows :— On receipt of Shenandoah's signal " All ready," the ' • Patoka"'—with yaw booms topped into position and yaw lines led through the booms and up to the masthead platform— steamed directly into the wind, with just sufficient head to in attendance as stated. At an altitude of 300 ft. the wind apparently varied from W.S.W. to d.ue W., this causing the airship to drift off the port quarter as soon as she lost way. On a second attempt the Shenandoah was brought into position for dropping her line by going to starboard of " Patoka " about 500 ft. astern and drifting back across her wake. The wire was dropped from about 300 ft. and secured by the speed boat. The end proved somewhat difficult to hold, due to the tendency of Shenandoah to rise and drift, but was secured at a second attempt and taken to the boat holding the " Patoka's " wire and connected. On subsequent occasions it would seem an improvement for "Patoka's" line to be moved towards the Shenandoah's instead of remaining relatively stationary—while the operation could be further simplified by reeling out a minimum of wire from the " Patoka." Immediately on connection the -winch started to heave in, and the difference in wind direction between surface and airship altitude, almost 90 deg., caused the bight in the hauling line to foul the fitting at top of port boom. This was cleared by Shenandoah going astern while winch reversed, * Mooring the "Shenandoah" at Sea : This view shows the air ship being hauled down to the mooring mast mounted on the tank steamer " Patoka." keep steerageway. In her wake followed four power boats— one about 500 ft. astern, holding the end of " Patoka's " main hauling line. Two others—one off each quarter, at a distance of about 600 ft., to stand by in readiness to take up the ends of the Shenandoah's yaw guys if necessary. The duty of the fourth boat was to reclaim the end of the airship's line when dropped and to proceed to first boat and connect the two ends. This method, if adopted, would parallel the moor ing to a land mast. In the manoeuvre, however, this plan was simplified by using pilot blocks to carry the ends of the yaw guys down the main line to the mast head and there to connect to ship's wires. The mast ram was not inclined until after both yaw lines were connected in order to facilitate this operation. It being anticipated that under the conditions prevailing the operation would occupy 30 minutes, the only consideration for the " Patoka " was to allow herself a clear course of a half hour steaming. The portion of Naragansett Bay chosen was between the mainland and Prudence Island, which has a direct north- south channel of over 10 miles in length and about 4 wide, and at the time of the experiment the surface wind was about S.S.W. in direction and 18 knots per hour. On the approach of Shenandoah the " Patoka " proceeded into the wind at about four knots with the power boats and to avoid a repetition the " Patoka's " course was changed to coincide with Shenandoah's. This led the surface ship towards shoal water, but fortunately the mooring was con cluded in time to avoid trouble, when the " Patoka "was again laid on her original course and moved off to her anchorage with the airship towing about 75 deg. over the port quarter. This incident seems to show the necessity for open water during future moorings. When the airship was down to about 200 ft., the line tautened in a series of jerks due to a slipping clutch on the winch. This caused enough slack in the line to enable it to jump the sheave at the foot of the mast and jamb between the sheave and the bearing. It took 15 minutes to free, and showed the wire to be badly stranded. A manila rope pre venter was fitted round the nigger head to take up the strain until sufficient good wire was coiled on drum. The trouble was caused by the type of fitting used, the sheave being too small in diameter and without guard plates. A further disadvantage is the fact that the sheave is fitted with com pression springs which tend to increase rather than dampen out the uneven hauling of the winch line. The running of yaw lines by pilot blocks from the Shenandoah proved quite satisfactory. The booms are too heavy in construction and cumbersome in operation, but proved of great value 562
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