Captain Roscoe C. Bulmer, Commander, Minesweeping Detachment, Mine Force One, Atlantic Fleet, to Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters
File No. 22-G. Base Eighteen,
26 March 1919.
From: Commander Minesweeping Detachment.
To : Force Commander.
Subject: Experimental Minesweeping – North Sea Barrage.
1. Upon completion of the repairs to the U.S.S. PATUXENT at Newcastle-on-Tyne, that vessel together with the U.S.S. PATAPSCO were fitted out for experimental minesweeping in the North Sea Barrage. Both vessels sailed from Inverness at 1920, March 20th, 1919, with Captain R.C. Bulmer in command of the expedition, and proceeded direct to the western end of Area B, where minesweeping was to begin. Difficulties encountered in putting out the sweep necessitated postponing experiments, and vessels proceeded to Otters Wick, where they remained for the night.
2. The following day, March 22nd, the PATUXENT and PATAPSCO got under way and stood out towards Area B. Commander Benson, R.N., Mine Clearance Officer, Orkneys and Shetlands, came on board to witness the experiments.
3. The first attempt to put out the sweep failed. Ships got too far apart and could not maneuver; also, had slight difficulty in handling Type 7 British Kites, which were used for the first time. On the second attempt the sweep was put out in fifteen minutes. It consisted of 570 fathoms of 13/16” serrated wire, shackled to the kites, which were towed from the ships by 6” Manila hawsers 50 fathoms long. On account of the difficulty in connecting separate insulated wire to the sweep, in order to use the charged sweep (which was preferable), it was necessary to abandon that idea and use simply the electrical protection for the ships by towing the negative pole of the protective circuit about 75 yards astern by means of an insulated cable. Soundings were taken by running a sounding tube down the kite hawser as far as possible. The average depth obtained in this method was 160 feet. The sweep wire probably averaged 30 feet greater in depth.
4. Entered the minefield on 22nd March, 1919, at 1038 and steamed course as shown on the enclosure, leaving the minefield at 1535. In all, fifteen mines were exploded by the sweep wire. Judging from the time which elapsed between the explosion and the moment when the slick appeared upon the surface (from 30 seconds to 1 minute) it is estimated that 12 of the 15 explosions were mines planted at a depth of 240 feet. This is what was to be expected, since the depth of the sweep wire was too great to cut the antennae of any except the lower level mines. Several mines were cut adrift, but much difficulty was encountered in observing them, on account of the choppy sea.
5. One fact of considerable importance was definitely established during this day’s sweeping. There were two separate cases of unquestionable counter-mining. In the first case the mine counter-mined exploded about 100 yards off the starboard bow of the PATAPSCO. The antenna float when released, popped up and passed within 20 feet of that vessel. This explosion followed closely upon a primary explosion detonated by the sweep wire. Twenty minutes later a similar instance occurred when one of the lower level mines detonated by the sweep wire caused two mines at the middle level to counter-mine directly below the PATUXENT. This resulted in considerable shock, throwing out the circuit breakers of the main generator, and breaking of china, lamp globes, etc; also, shook the radio motor generator off its pedestal.
6. At 1537 a heavy snow squall came on with a rising wind, and it was decided to take in the sweep before the weather became worse. Just before this could be done, the Manila kite hawser on the PATUXENT carried away. In attempting to haul it in the kite fouled the bottom and parted the sweep wire.
7. Both ships proceeded to Lerwick in order to inspect the facilities at that place in case it were decided to use it as an advanced base while sweeping in Area A. Captain R. C. Bulmer accompanied by Lieutenant Noel Davis called upon Rear Admiral Clement Greatorex, R.N., C.B., Commanding The Shetland Islands, on March 23rd.
8. Both ships again got under way at 0600 March 24th, standing down towards No. 5 buoy; put out sweep at 1232, with 400 fathoms of sweep wire, half serrated and the other half plain, with 50 fathoms of 6-inch Manila on the kites. Sounding again showed the kites to be at a depth of approximately 160 feet. The weather was unusually fine with a calm sea. Stood to southward, crossing five minefields in Areas A and B. Six mines were exploded and 15 others were cut adrift by the sweep. The majority of those exploded were again from the lower level, judging from the time it took for the slicks to appear. Of the 15 mines cut adrift, about an equal number appeared to be surface mines and those planted at 160 feet. In all cases it was impossible to determine whether the antennae was still attached to the mine, on account of the distance they were away, but in some cases the floats could be distinctly seen along side of the mine case, some of the surface mines still having the two floats attached, showing that at least part of the surface mines with their antennae had weathered the winter gales. There was no counter-mining during this day’s sweeping. The fifth mine which was exploded evidently parted the sweep wire, and the 6th mine appeared as if it struck the PATUXENT’s kite which was noticed to be carried away a few moments later. It was not discovered, however, that the sweep wire had been parted until the sweep was taken in about 2-1/2 hours later.
9. Upon completion of the sweeping the two vessels proceeded to Kirkwall to inspect the local facilities for basing the minesweeping detachment while engaged in the western part of the North Sea Barrage.
10. Three British Floating mines were sunk by gun fire, one on March 22nd, and two on March 24th. Another was seen to explode when washed up on the beach while at anchor at Otters Wick.
11. One U.S. mine was seen afloat while sweeping, but it was impossible to sink it. Of the remaining U.S. mines which were cut adrift, it was not possible to sink them while sweeping was in progress, nor to return after the sweeping had been completed, on account of darkness. It is believed, however, that they are safe, for, had the extender mechanism and hydrostat <not> functioned upon the mine coming to the surface, the antennae would have fired the mine by fouling the steel case. None of those cut adrift fired through this cause.
12. Summing up, a total of 21 American mines and 3 British mines were destroyed. Seventeen more American mines were definitely known to have been cut adrift, and it was probable that on the first day that sweeping was conducted a great many more were cut adrift which could not be observed on account of the weather. The possibility of mines counter-mining while being swept has definitely been established and may result in damage to the sweeping vessels. This risk, however, is considered unavoidable. The expenditure of kite material will probably be considerable. In two days’ sweeping two plunger kites were lost and about 400 fathoms of sweep wire.
13. Plans are in hand for utilizing the PATAPSCO and PATUXENT for carrying out early sweeping operations in Area C in order that the British may have a field clear of American mines in which their sweeping operations may be undertaken.
R. C. Bulmer
Bureau of Ordnance
Rear Admiral Joseph Strauss.