Commander Charles R. Train, United States Naval Attaché in Rome, to Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters
15 July 1918.
From : Naval Attache, Rome.
To : Force Commander.
SUBJECT : Inspection of the Italian Net Barrage Straits of
On 12 July the Naval Attache spent the entire day on the Barrage between Otranto and the Island of Fano, watching the laying of a complete section of the net, and submits the following report. He wants to further add that from all accounts he is the first officer of the Alliez Navies, other than those personally working on the net, to have thoroughly inspected the work.
I. The net Barrahe is to run between a point ten miles off shore from Otranto to Fano Island, a distance of about 35 miles. The I0 miles off shore from Otranto, are protected by a heavy mine Barrage.
2. The Base for this work is Otranto, the work being under the charge of Captain Piazza, of the Italian Navy, who is ably assisted by Capitaine de Corvette A. De Quillacq, of the French Navy, the latter being the inventor of the mines to be used for the explosive features of the net. The working vessels consist of one very old Italian steamer of about 500 tons, and one French steamer slightly larger. The former lays buoys, and the latter nets. The Italian steamer has no facilities whatever for the work, except those which have been improvised. She has only one steam winch, and the heavy buoys and anchors are hoisted out of the hold by a chain fall, and the derrick for hoisting and holding over the side, the buoys and anchors, is operated by hand. In this regard one of our lighthouse tenders would save hours of work, and many hands. It is not believed possible, however, that more efficient results could be obtained with the facilities available, than are secured by Captain Piazza, whose energy and ability are of the highest.
3. Protecting the force at work are several British motor chasers, and Italian seaplanes.
4. GENERAL SCHEME: The nets arrive in I00 yard lengths and are then assembled by threes into the net proper, 300 yards long; each end of this net is supported by a buoy, and with the assembling and laying of eight such nets, with the nine buoys, a section is formed, of 2400 yards: 35 sections are figured on for the complete Barrage, but owing to the large factor of safety it is believed that 31 will suffice.
NETS. The nets are of steel wire about 5m/m in circumference, formed into square mesh 3/5 meters on a side[.] The net hooks on to a stronger and heavier steel wire, about 4 c/m in circumference, called the Jack Stay wieght 64 kg. per I00 meters. This jack Stay runs from buoy to buoy while the weight of the net is partially taken up with a balance weight of 50 kgs. (II0 lbs.) hanging down below the surface, and hands to a depth of 50 meters. The dip, orsag, at the center of a 300 yard net, has never been found to be greater than I-I/2 feet.
BUOYS. At depths up to 400 meters, one buoy of the large size was found sufficient (a buoyancy of 750 kg.) but after 600 meters was reached a smaller buoy with a 250 kg. buoyancy additional was found necessary. These buoys are spherical, the three parts in which the plates are originally cut are welded by oxygenl there are no rivets except for the eye bolts at either end. The large buoys are I.20 meters in diameter, while the smaller ones are 0/83 meters in diameter.
ANCHORS. Anchors are of cement, in two sizes : the upper one 900 kgs. And the lower one 600 kgs. These are placed I0 meters apart to give the proper depth to the buoy below the surface, as the buoy is attached at the point of the anchor wire marked when the first anchor touches bottom.
ANCHOR CABLE: This cable is of steel, about 2 inches in circumference.
EXPLOSIVES : The DeQuillaeq mine as used contained 35 kgs. Of milonite. In each net proper there are 6 mines, that is, in each 300 yd. net between two buoys. These mines are cylindrical, about 2-1/2 feet high, and 15” in diameter, and are hooked on to the Jack Stay. In the top of the mine is coiled a small wire cable, about I00 yards long. Upon the submarine entering the net, she becomes enveloped, the net breaking away from the Jack Stay, and also the mines: the end of the lanyard remains attached, however, and as the minesweeps in alongside the submarine with the net, it explodes at the end of the line. Experiments have indicated that the mine always explodes within 5 meters of the hull of the submarine.
c LAYING THE BARRAGE: Buoys are laid first; and the work is a simple one, except for the fact that the steamer used has no facilities. Huge drums on the stern carry sufficient cable for many buoys. The anchors are hoisted out of the forehold, and the heavy one hung over the side (just over the bow) and held until the anchor cable is made fast, then lowered and the small anchor made fast, ten meters above. The cable passes forward from the drums along the starboard side, over 3 breaks, and finally over the strain device. This is only an apparatus roughly made from the recoil springs and cylinders of a 6 inch gun. The cylinders are placed vertically abreast; the wire cable passes under a wheel pulley from aft, up over another wheel pulley whose axle is supported on the upper ends of the springs, then down on the forward side under another wheel pulley, and forward to the anchors. The pressure on the cable fluctuates as the anchors are lowered, and is taken up on the springs. When bottom is reached, the springs relax and take a normal position. The point on the anchor line is then marked, and from that point the distance is measured for securing the buoys. After again releading the brakes, the second anchor, ten meters above the first, takes bottom, and the buoy is pulled that distance below the surface.
The buoys are laid two every hour in the present depth of about 750 meters. Distances are taken from signals placed above the preceding buoy, with a marked line, checked up with a small range finder. Direction is taken by a compass. At present on clear days both ends of the Barrage, Otranto to the West and Fano Island to the East, are visible, which greatly facilitates the work.
The net is laid from the French steamer, Laid out free for running along the starboard gangway, and put overboard, over the stern, in the neighborhood of the two terminal buoys.
First a cork float is sent over; then the net is passed over, but before leaving the ship, at every vertical of the mesh (that is every 3.5 meters) a bunch of 8 or 9 balls, encased in a small mesh net, are attached at the Jack Stay, and at the proper intervals, the mines. When the entire net is over, the ends are hauled out to the buoys by tugs, and made fast by divers. Under good weather conditions, they can lay 5000 yards of net a day – a record has been made of 14 buoys and 11 nets, with two ships, on one day. In four days, in early July 12,000 meters were completed.
PRESENT SITUATION :
At present ten miles of mine barrage are in place off Otranto, and the last buoy is 24 miles from Otranto and the last net 19 miles. In other words, assuming the I0 miles of mines as part of the Barrage, and the total distance 45 miles, 19 miles are complete, with 5 more miles of buoys in place. Material for 5 complete miles is ready so the laying can continue. Material for 4 more is in Taranto, being assembled, which will shortly, at the present rate of work, bring the Barrage within 17 miles from Fano. The remaining material is coming from England, and every belief is held that it will arrive in time to complete the work before the winter. Buoys and anchors are ready, but wire is the need. From this it will be seen that lack of materials alone is the cause of the non-completion of the work. Bad weather has only slightly delayed the work. May , contrary to expectations was a very bad month. Thus June, and the few days of July, are the only working days that the Italians have had at their disposal since the start of the Barrage. The first year was lost, on account of experiments, and agreements over the English surface Barrage and the Italian invisible barrage. Experiments quickly showed the complete impracticability of the English system, as nothing was thoroughly and successfully tested out, by laying a duplicate Barrage in the Gulf of Taranto, during the months of February and march, the two worst months of the year in these waters. Terrific S. & S.E. blows were experienced, but after two months not a dislocation of buoys, net nor anchors was found – to the smallest degree – and no buoys experienced the slightest leak.
CONCLUSION & RECOMMENDATIONS:
After a complete day on the Barrage, watching indetail the work, the Naval Attache cannot too highly praise the results accomplished by Captain Piazza, and he has complete confidence in the success of the enterprise, with the one exception that the net is not of sufficient depth. Captain Piazza also, is of this opinion, but believes that a second barrage should be laid, with an increased depth of at least 75 meters. He has demonstrated the case with which it can be laid if material is an hand; also the short time required- that is, in good weather, two sections a day; which would complete the net Barrage in 18 working days.
The Naval Attache personally believes that the net will catch submarines even at the depth of 50 meters: but recommends in this regard, that the mine Barrage now laid off Cape St. Marie de Leuca be increased by the addition of American mines to such a distance off shore as will prevent submarines from obtaining a fix at that Cape? This will prevent them from accurately locating the net in relation to themselves, and from escaping with only a short run at a 200 ft. depth.
It is also recommended that –
(a) If another Barrage is laid as already contemplated, to the northward, the U.S. make some effort to supply a part of the material.
(b) That the U.S.N. offer the services of one of its best Screw Buoy Tenders of the Lighthouse Service; and
(c) That as a support of the net, the U.S.N. establish a mine base at a convenient point for the laying of the deep water American mines. In this regard it may be added that if a 500 fathom mine be developed, it could be placed off Fano and save a short distance of net; and if not developed, the present deep water mine would assist and shorten the new contemplated net Barrage between Otranto and Aspriruga.
/s/ C. TRAIN.