----------------------------------------------------------------------- Page 34
----------------------------------------------------------------------- Page 35 In the engine room a similar connection for injecting cement was fitted to the battery ventilation valve and a hose coupled up for the job. As this valve was larger than the one in the C.O.C., the cement tank on the "Falcon" was increased in size by lengthening it until it held 7 cubic feet. About 10 cubic feet of the cement mixture was forced through without difficulty, after which the hose was removed and the rig dismantled. The two ventilation valves in the C.O.C. and the engine room were thus sealed off with only a fraction of the work that would have been required by any other method. Air was soon put on the C.O.C., and in a little over an hour it was cleared of water. At this point, the end of May, work was started on the tunnel for the last pair of pontoons, abreast frame 74. There was first used on this tunnel a new nozzle designed and made by Machinist's Mate (Second Class) Waldren, attached to the "Falcon". In this nozzle there were 6 jets, 1 large one ahead and 5 smaller ones radially astern. It was found that the jet arrangement abolished the reaction which previously had made it impossible for the diver to hold a 2.5-inch hose with any special pressure; further, the radial jets enlarged the hole cut by the forward jet and shot the material cut loose astern at considerable speed. The divers found that with this nozzle they could easily hold all the pressure that the "Falcon's" wrecking pump could supply through a 2.5-inch fire hose - 200 pounds - and even at this pressure they called for more, but the "Falcon" was unable to supply it. (See fig. 13.) As a result of this highly efficient nozzle, a sizable tunnel was run on the starboard side, so that on the first day the keel was reached in only five dives. The next day a tunnel was started on the port side to meet the one on the starboard side. The first diver made excellent progress, but while the second diver was down the cylinder head blew off the "Falcon's" wrecking pump, the cast-iron head being too weak to stand the 200-pound pressure. Tunneling had to cease while the "Vestal" made a new head out of 1-inch boiler plate, which was installed late that day. The next day tunneling was resumed, working on the port side. The fourth diver down, Carr, washed his way through into the starboard tunnel and crawled through under the boat to the starboard side, dragging the hose through with him for a reeving line. Two regular reeving lines were quickly passed through, and the same day, in spite of very rough weather in the afternoon, a pair of 2.5-inch chains were dragged through the tunnel and equalized. It was estimated that the new nozzle was at least 10 times as efficient in cutting as the standard nozzle, for in two short working days a longer tunnel had been run through at frame 74 than the one at frame 46 on which six weeks' work was spent in the fall and two weeks' work in the spring before success was achieved. On June 5 the fourth and last pair of pontoons was lowered abreast the conning tower and secured to the chains already rove through the tunnel at frame 74. The same day work was commenced on blowing dry the port-side ballast tanks Nos. 3, 4, and 5, which had been partly blown out the previous November, using the submarine's own air. On this final blow the air was supplied by a diver inserting an air hose from the outside of the boat through the Kingston valves, which had previously been opened. These Kingstons, however, were buried in the clay on the port side and it was necessary to wash this clear first. It was discovered that these tanks had retained practically all the air forced into them months before, as it required only a few minutes blow on each one to dry it completely. To blow No. 2 port ballast tank it was necessary to burn a hole in it near the bottom, and the same process was required for starboard tanks Nos. 2 and 3, as the operating gear for the Kingstons for these tanks could not be reached from the inside. Having burned through No. 2 port ballast tank, an air hose was inserted, but all the air immediately escaped from the top. This trouble had been considered likely from the beginning, as the forward bulkhead of this tank was somewhat damaged in the collision; the use of this tank was abandoned and with it there was also abandoned No. 2 starboard tank, which, while intact, could not be used without giving the ship a permanent list when raised. ----------------------------------------------------------------------- Page 36
Figure 12: Superstructure deck removed by divers
in way of main air induction valve.
(Note strong back on this valve.)
----------------------------------------------------------------------- Page 37 It was decided at this time not to blow the other starboard side ballast tanks for the time being. The submarine had a list of 11.5 degrees to port, which it was hoped could be eliminated and at the same time the bottom suction could be broken by rolling the ship to starboard. Having dried out three port side ballast tanks, the rolling moment available was somewhat over 600 foot-tons; it was believed that as the vessel was lightened she would roll and thus break the bottom suction, which constituted an unknown but powerful force, considerably greater than the dead weight. No change in the heel of the boat was noticed for several days after the port-side tanks had been dried out. Consideration of the conditions governing the forward and the after groups of oil tanks led to the conclusion that the forward group of tanks could not safely be blown dry while on the bottom. This was due to the fact that no adequate vent for this group of tanks could be provided which would relieve the pressure when the vessel rose, with the result that the light tank tops would bulge upward and perhaps rupture. On the other hand, this group could not be blown dry and then vented down before rising, for the compartment over it, the battery room, was open to the sea and the tank top would collapse if the pressure inside the tank were dropped with the vessel at the bottom. It was therefore decided that the forward group of oil tanks would be left flooded while at the bottom and regarded as reserve buoyancy to be obtained after raising, or to be used in case of emergency if necessary to bring up the bow, and the blowing connections were so set. Conditions in the after group of oil tanks were different, as this group was below the engine room, which was to be blown dry. Here it was possible to equalize the pressures on the tank tops by providing a vent from the fuel-oil tanks to the engine room. After blowing the after group of oil tanks dry, this was done by one of the divers by smashing the glass on the Thomas fuel-oil gauge to the aftermost tank. This allowed the oil tanks to vent to the engine room, but did not permit water to flow from the still flooded engine room into the tanks as long as the air pressure stayed in the oil tanks. Having blown the after group of oil tanks, the fuel-oil manifold in the engine room was set for blowing the forward group, and all was then in readiness for sealing the engine room. The ladder in the engine hatch was removed and the floor plates under this hatch were removed so that the spill pipe from the salvage hatch could reach some 4 feet below the floor plates down to the tank top in the bilges. To handle this hatch, the "Vestal" built a small davit similar in size to the torpedo crane used on submarines; this was sent down and set up on the submarine by the divers to plumb the engine room hatch. The engine room hatch differed from the gun access and conning tower hatches in being larger and in having a trunk 30 inches long from engine room to deck. This placed the strong back for the engine room hatch much farther below the cover than in the cases of the covers fitted over the conning tower and the gun access hatches. Divers Smith and Carr were rehearsed on the installation of the hatch on the "S-50" under conditions approximating those on the "S-51". They then descended to the "S-51" and the hatch assembly was lowered down to the "S-51's" deck where the divers hooked it with a chain fall from the davit and attempted to install it. The attempt failed due to inability to get the strong back centered at the bottom of the deep trunk, a difficulty caused by the heel of the "S-51" to port which resulted in the heavy hatch and its strong back sliding off repeatedly to the low side. After a struggle lasting 3 hours and 20 minutes, the two divers, against their will, were told to cease and come up. On this, the longest dive ever made on the "S-51" job, the divers were given a decompression of nine hours and, while very weak afterwards, showed no signs of the "bends". ----------------------------------------------------------------------- Page 38
Figure 13: Waldren's special balanced hose nozzle.
----------------------------------------------------------------------- Page 39 After a second pair of divers had tried to adjust the hatch and failed, the hatch and strong back assembly was sent back up to the "Falcon", where the rig was redesigned for installation in two parts, the strong back to be installed separately and held in place, centered, by a light auxiliary strong back near the top of the trunk, after which the hatch cover was to be lowered in place. This design was tried on the "S-50", found satisfactory, and the divers rehearsed in its use. (See fig. 7.) Another attempt was then made to install the hatch and strong back on the "S-51", but various mishaps caused failure, and it was only at the end of four days' work on the hatch that Smith and Carr, who started the job, finally succeeded in lining up the hatch and bolting it down. (See fig. 14.) It could be noted from the results on this hatch that the divers were beginning to play out; that their physique and their power of coordination was falling off though their morale was excellent, as it seemed evident to all hands that the end of the job was in sight. The number of divers available had decreased from the 24 men who started the job in April to 15 men by the middle of June. Of these, 3 were able to work only on short dives; practically all of the remainder were in poor condition, and minor cases of the "bends" were becoming frequent. To help as much as possible, all divers were taken to Newport on bad weather days for recreation and a change of scene. The interior of the "S-51" was, on June 13, completely sealed up. Air was put on the motor room, shortly blowing it dry, and then drying out the engine room, as the motor room blew through a nonreturn valve into the engine room. After two hours blowing through the motor room, air began to escape from the discharge valve on the engine room salvage hatch, showing the engine room dry down to the bottom of the spill pipe. A few minor leaks were found around the hatch cover; the securing nut was sledged up tightly and these ceased. Attention was now devoted toward drying out minor tanks forward. Chief Torpedoman Kelley, with the torch, burned holes in the bottom of the forward trimming tanks and the water round torpedoes tank and blew them both dry. On a later dive an air hose was inserted through existing openings in the bottom of No. 2 bow buoyancy tank and it was blown dry. An attempt to blow No. 1 bow buoyancy failed when a bad leak showed up in the deck forming the top of this tank. On account of the small size of the tank, the work required to seal the leak did not appear warranted. An effort was made to get to No. A main ballast tank, under the torpedo room, with the torch and burn a hole in it near the keel, but the tank was buried in the clay, and it was found that the diver could not get low enough without digging a tunnel under it. The same condition was found as regards No. 1 fuel-oil tank, which was also under the torpedo room. As neither tank was very large and the need for the buoyancy did not appear great, no attempt was made to tunnel under; further, the condition of the divers now made it necessary to eliminate everything but essential work on the bottom. On June 11, 1926, all pontoons having been lowered and secured, a start was made on leveling off the pontoons above the submarine with slight positive buoyancy, preparatory to lashing them. On account of the long tow, 150 miles, to New York, it was necessary to keep the pontoons clear of the hull of the "S-51" or they would batter themselves and the "S-51", especially in the early stages of the tow through the open sea. The lengths of the cradle chains were so adjusted as to leave a clearance of several feet between the pontoons and the "S-51's" deck; at the same time they were short enough so that the maximum draft afloat would be about 32 feet, which would clear all channels and allow the submarine to enter dry dock without the necessity of shortening up the slings. (Pls. 5 and 6.) It was essential that the pontoons should be level before lifting commenced, otherwise attainable buoyancy would be lost. It was further necessary that the pontoons be lashed against slipping aft when the stern was lifted, and these lashing could be put on only after the pontoons were in position above the submarine. ----------------------------------------------------------------------- Page 40 Sufficient knowledge of the cranky nature of the pontoons as provided had already accumulated to make it evident that difficulty would be encountered. To equalize conditions the pontoons abreast the conning tower, which were selected as the first pair to be leveled off, were vented down at both ends until they were known to be completely filled with water. All four ends were then blown together in an attempt to maintain an equality of buoyancy, but owing to variations in hose friction the pontoons rose one end at a time, their lack of longitudinal stability being just as marked here as when first attempts were being made to lower them. Unfortunately the end of a pontoon which rose first would drag all the slack chain through under the boat from its mate pontoon on the other side. The result was a pair of cockbilled pontoons, one of which was very much too high above the submarine, and the other, inclined in the opposite manner. had one end held to the ground. A number of attempts were made to rectify this condition during the remainder of the day, but the pontoons merely seesawed the cockbilling, from one end to the other as buoyancy changes were tried, and it was found impossible to get the pontoons level and both at the same height. To overcome this difficulty an inversion of the lowering process was tried next day. The pontoons abreast the conning tower were flooded again and sunk to the bottom. Here divers descended and fastened a 1-inch wire cable, marked off in fathoms, to the lifting pad at each end of the starboard pontoon only using a pelican hook to shackle up the wires. These wires were led to the surface where they passed through the bitts, one to the forward winch and one to the after capstan. A moderate strain was put on the wires. Both ends of the starboard pontoon were then blown together for one minute. When blowing ceased both winches took a pull, but the weight to be lifted was still too great. Blowing was resumed for periods of one minute at a time, alternating with attempts to lift. When the negative weight had been reduced so that it came within the safe capacity of the gear, about a 5-ton pull on each wire, the pontoon was slowly lifted from the bottom, still with negative weight, and hoisted up until the marks on the wires showed that it was at its proper height above the submarine. In this process the pontoon lightened up somewhat as the internal expansion of air under decreasing pressure forced out some of the contained water; on the other hand, the pontoon had added to it the weight of the chain cables, which it lifted off the bottom as it rose. The gain and the loss approximately balanced and no pontoon lightened enough to become positively buoyant and float up higher than the point to which it was hoisted. (See pl. 4.) Having reached a proper height, the starboard pontoon was left suspended from the wires and blowing was started on both ends of the port pontoon. The gauges were carefully watched during this process, blowing being frequently stopped to check the pressures in the pontoon. As soon as one end showed by a drop of pressure that it was rising, blowing on that end ceased, but the air was kept on the other end until it also floated up. The motion of each end of the port pontoon was limited, as it was bound to stop when it took up all the slack in the chain leading to the other side. This resulted in the port pontoon finally floating level at a height which placed it abreast of the suspended starboard pontoon. Having reached this position, both ends of the suspended pontoon were gradually blown until the pontoon showed positive buoyancy, as indicated by lack of strain when the suspension wires were slightly slacked off. Both pontoons were then blown together for about two minutes, giving each of them a positive buoyancy of about 6 to 8 tons, when a diver was sent down and cast loose the wires to the suspended pontoon, leaving both pontoons floating properly in position. The leveling method just described was followed on all other pontoons. It was quick and reliable, the only drawback being the danger of breaking the suspension gear due to the rolling and pitching of the "Falcon". Owing to its large size and total immersion, the pontoon suspended did not follow the rolling motion of the "Falcon" from which it was hung; in addition it was restrained against such motion, after its mate pontoon had been floated up, by the tension in ------------------------------------------------------------------------------- 1 See Appendix D. ----------------------------------------------------------------------- Page 41 the chain cables attached to both pontoons. On three different occasions the motion of the "Falcon" under these circumstances parted a pelican hook to the suspended pontoon allowing it to drop and requiring the leveling job to be done over again. Consequently, leveling could be attempted only in moderately good weather; better weather in fact than was required for lowering pontoons. On June 13, 1926 a second pair of pontoons, being the pontoons abreast the battery room, was leveled off in the same manner. About five days had now gone by since the port side ballast tanks had been dried out and the "S-51" showed no signs of rolling to starboard, although the engine room and the motor room were now blown dry. On the other hand, the C.O.C., which had previously been dried out, had had its blowing hose carried away while the pontoons in its vicinity were being leveled off, allowing the air to escape and the C.O.C. to refill. To expedite matters as regards rolling the ship and breaking the suction, the two pairs of pontoons already leveled off, being No. 2 pair and the No. 3 pair, over the battery room and the C.O.C., respectively, were now blown completely dry. Nothing happened. The following day, June 14, a new blowing connection was attached to the C.O.C., and measurements were taken for the lashings for the pontoons already afloat. Following this, an attempt was made to line up the stern pair of pontoons, in the course of which the port pontoon of the pair was given slight buoyancy. With matters in this state Carr started down to install clamps for lashing the pontoon chains together. While he was still descending, a series of large air bubbles broke the surface for practically the entire length of the submarine, the disturbance lasting about half a minute. It was evident that something unusual had happened on the bottom. Carr reached the submarine a few seconds later and, after some minutes spent in orienting himself, finally announced that the submarine had rolled and was then inclined about 20 degrees to starboard. This report was received on the "Falcon" with considerable rejoicing, as it was the first positive evidence received of any movement on the part of the "S-51" since her sinking. There could be no doubt now that the suction effect was in a large measure already broken by the roll; the last lingering doubts as to the possibility of being able to lift the ship were finally removed, as the suction had been the one factor which could not be definitely figured on and which had to be outmaneuvered rather than overcome by direct buoyancy, of which sufficient could not possibly ever be brought to bear. It was also discovered on further inspection that the stern of the "S-51" had lifted about 5 feet, showing that the buoyancy already attained astern was nearly sufficient to start the stern upward without help from the stern pair of pontoons. This checked with the buoyancy calculations which had previously been revised to take account of the fact that a large portion of the tiller-room buoyancy, all of the motor-room buoyancy, most of the engine-room buoyancy, and a large fraction of the buoyancy of the after group of oil tanks had been attained. The buoyancy tables had been changed as shown below, on the basis of what was then definitely known to be available: ------------------------------------------------------------------------------- | | Percent of | Net Compartment | Total | buoyancy | buoyancy | buoyancy | attainable | available --------------------------------------------+----------+------------+---------- Tiller room ................................| 15 | 80 | 12 Motor room .................................| 137 | 100 | 137 Engine room ................................| 110 | 87 | 96 Port ballast tanks, 3, 4, 5 ................| 62 | 81 | 50 Starboard ballast tanks, 3, 4, 5 ...........| 62 | 81 | 50 C.O.C. .....................................| 90 | 67 | 60 After-group oil tanks ......................| 33 | 100 | 33 Forward trim tank ..........................| 10 | 100 | 10 Water round torpedo tank ...................| 6 | 100 | 6 No. 2 bow buoyancy tank ....................| 11 | 100 | 11 |----------+------------+---------- Total ................................|..........|............| 465 ------------------------------------------------------------------------------- ----------------------------------------------------------------------- Page 42 To prevent the possibility of damaging the stern pair of pontoons, the stub mainmast, which came in their vicinity, was burned away with the torch. Several attempts to level off the stern pair of pontoons failed, due to breaking of pelican hooks on the suspension wires. While the leveling operation was under way, the starboard ballast tanks Nos. 3, 4, and 5, which had never previously been touched, were blown dry by Michels, using an air hose inserted in the hole burned in No. 3 tank and in the open Kingston valves of the other two tanks. Wickwire, who shortly afterwards went down to inspect the location of the starboard after pontoon, which was somewhat close under the counter with the submarine leaning on it, was standing on the bottom just outboard of the pontoon when the pontoon first rolled gently and then started to float up while the submarine rolled from 20 degrees starboard to 10 degrees port before his astonished eyes. Wickwire reported the first part of this performance over his telephone as it occurred; then as it appeared that both submarine and pontoon were on their way up and he was in a dangerous position, he started to run along the bottom to get well clear. Unfortunately his air hose led across the pontoon chains and fouled there; the pontoon was now so high that Wickwire on the bottom could not see it, but finding himself fouled (which was also discovered on the top side) he climbed his air hose to the under side of the pontoon, cleared it of the chain and then slipped down and climbed aboard the stern of the submarine. This prompt action in clearing himself proved exceedingly fortunate, for immediately afterward the pontoon sank again to the bottom, coiling down and resting on the chain where but a short period before his air hose had been fouled. Wickwire checked the new position of the pontoon, noted the angle of heel of the submarine, and came up. To prevent any premature rise of the stern, about 60 tons of water was flooded back into the third pair of pontoons, abreast the conning tower. An inspection made shortly after showed that the stern, which had been up about 5 feet or more, had settled back nearly to its original position and that the submarine was heeled only about 5 degrees to port. It was evident that with both starboard and port ballast tanks blown, buoyancy was now symmetrical and so far as the bottom conditions permitted the ship was floating upright. Lashing of the pontoons as they were leveled off was installed, partly to hold them against change of position from inequality of buoyancy in the blowing operations but mainly to prevent them from slipping aft when the stern had lifted and before the bow came up. It was essential to prevent such change of the pontoons at the bow during this stage, as slipping aft would reduce their lifting moment; it was further essential that by no possibility should the pontoon chains be permitted to slip out from under the hull while the ship was at an angle with the stern up. To attain this, pontoon sling locations were chosen, talking advantage of such natural stops as the ship's structure presented. The stern pair of pontoons had the after chain passed inboard of the shafts and just forward of the skeg; this wholly prevented these pontoons from slipping aft. The bow pair of pontoons had its forward chain caught in the anchor well under the keel and the after chain rove through the bow plane guards so that movement either astern or ahead was impossible. The third pair of pontoons and the second pair of pontoons, however, were naturally restrained from sliding aft only by the fact that the hull widened out aft in their location, though this widening was not marked in the case of the third pair, abreast the conning tower. The possibility of the pontoons slipping forward in the raising operations was considered and taken care of to some extent, though it was regarded as remote if the raising plan was carried through of bringing up the boat stern first. To prevent motion aft on the part of the second and third pairs of pontoons, a special steel clamp was secured by the divers on each pontoon chain below the pontoon and just above the point where the chain cleared the hull. As shown on Plate 6, a 1-inch wire lashing with an eye in each end was then run generally athwartship just above the deck of the submarine, the ----------------------------------------------------------------------- Page 43 wire eyes being secured at each end to the chain clamps. The entire rig was designed for a breaking strain of about 30 tons on each wire. In this way each wire tightly cradled the submarine in a continuous loop of chain and wire when the angle of the boat caused the wires to take up. Further, the wires for the third pair of pontoons led across the deck just forward of the gun access trunk, which thus acted as an effective stopper against slipping aft. As an additional safeguard on this pair, another wire was led around the gun mount somewhat forward of the pontoon. To keep the second pair of pontoons from sliding forward, a wire lashing was run from the chains aft around the gun mount, in addition to the athwartship pair of wire lashings. It was further evident that under full buoyancy the bilge keels in way of the chains for the second and third pair of pontoons would buckle up and thus form a niche for these chains which would tend to prevent slipping. Calculations showed that at a 30 degree angle, the force tending to make the pontoons slip was equal to half the lift of the pontoons - a very considerable force - but there was provided by the lashings, by the bilge keels, and by friction of chains against the hull an antislipping force which afforded a fair margin against slipping aft. It may be stated that this proved correct, as the pontoons on the final raising retained their designated positions without evidence of slipping. Having secured the lashing clamps around the chains, the divers took measurements of the lengths of lashings needed, using a small manila line stretched between the clamps. With these lines as a guide, the "Falcon" cut the 1-inch wire and spliced in the eyes. It was shortly seen that splicing caused too much delay; eyes were thereafter made with clips, using four wire clips for each eye. This proved a quick method and turned out satisfactorily; no clipped eye ever gave way. Handling the 1-inch wire lashings on the insecure footings over the side of the submarine caused the divers trouble, but they were all installed as desired. It was during the installation of the lashing wires on the second pair of pontoons that trouble commenced which led indirectly to the rising of the bow a short while later. The second pair of pontoons having been leveled off with moderate positive buoyancy and properly adjusted, the measurements for the lashings were taken. When the lashings were sent down for installation, it was found that they could not be installed, as the forward end of the starboard pontoon had sunk until it rested on the bow pontoon just ahead of it which it overlapped, the bow pontoon itself being on the bottom, not yet having been floated up. Had this bow pontoon not been there, the No. 2 starboard pontoon would have sunk to the ground, probably standing on its end. This trouble was obviously due to air leakage from the pontoon, which reduced the buoyancy in the forward end until it sank. The same leakage, to a varying extent, was discovered on every pontoon on the job except the No. 3 pair. The leaks were of two kinds - one due to springing of rivets or seams from the banging received by the pontoons either on the tow from Newport to the wreck or while alongside the "Falcon" plunging up and down in the sea during the lowering process; the second type of leak was in the vicinity of the hawse pipes, where some of the calking around the castings, which was probably tight under no load, opened somewhat when a load was applied via the chains and started leaks. The results were serious. Considerable trouble had already been expended in leveling off the pontoons and it was necessary that they be kept leveled off. The pontoon which had sunk was leveled again. After that all pontoons afloat were inspected and they were thereafter given a brief daily blow to compensate for such leakage as was evident. In addition, after blowing the No. 2 pair down completely for the purpose of helping to roll the submarine, its flood valves were temporarily closed, so that the admission of water would be minimized even though air leaked out. 45129-27--4 ----------------------------------------------------------------------- Page 44 On June 20 the bow pair of pontoons was leveled off, the process being complicated by the breaking of one pelican hook on a surge, and the untoggling of the other one, which resulted in standing one of the pontoons on end for a while. Both pontoons were finally fairly well leveled off above the submarine, but as leaks showed on both of them, the flood valves were temporarily closed to minimize leakage. On June 21 the stern pair of pontoons were leveled off above the submarine. The divers measured off for lashings, but while they were being installed the port pontoon of the pair suddenly shifted position under the eyes of the divers, the stern going up about 10 feet and the bow dropping considerably. Fortunately neither of the divers was injured. The forward end of this pontoon was given more air to compensate for leakage and an attempt made to close the flood valves, but one failed to close at all and another was doubtful. It had been expected to tow the "S-51", when raised, with her own towing pennant, which was normally secured in place to a towing rig forward with the pennant stopped along the deck edge. A diver's examination of the boat showed the pennant missing. (It was later found on the dock at New London.) It therefore became necessary to supply another towing pennant, and for this purpose a bridle made of 1.5-inch chain cable was rove under the keel, through the bow plane guards, port and starboard, and then shackled together in front of the bow, with 150 feet of 1.5-inch wire leading forward for the tow line. As a line for towing astern, should it be necessary, or for steering the boat in any case, another 1.5-inch chain bridle was passed around the stern inboard of the propeller shafts, shackled together under the hull, and a 1.375-inch wire, 150 feet long, led aft from the top of the bridle for the stern line. Both the bow and stern lines were laid out on the bottom and buoyed to the surface for picking up when the "S-51" rose. The submarine being known now to be light, the engine room was flooded to prevent a premature rise. The final lashings were put on the bow and stern pairs of pontoons, which work was finished late at night on June 21, and everything was in readiness for raising the submarine on June 22. The buoyancy conditions when work ceased on June 21, were as follows: Buoyancy (tons) No. 1 pair pontoons (bow pair) just buoyant ............................. 20 No. 2 pair pontoons (over battery room) completely dry .................. 160 No. 3 pair pontoons (abreast C.O.C.) partly blown ....................... 100 No. 4 pair pontoons (stern pair) just buoyant ........................... 10 No. 2 bow buoyancy tank, dry ............................................ 11 For'd. trim tank, dry ................................................... 10 Water round torpedo tank, dry ........................................... 6 Port ballast tanks 3, 4, 5, dry ......................................... 50 Starboard ballast tanks 3, 4, 5, dry .................................... 50 C.O.C., flooded ......................................................... 5 Engine room, flooded .................................................... 0 Motor room, dry above shaft lines ....................................... 110 Tiller room, partly dry ................................................. 12 After group oil tanks, dry .............................................. 33 ------ Total ............................................................... 577 The moment against rising by the bow, based on the above tabulation, was 11,643 foot-tons. The moment against rising by the stern was 15,117 foot-tons. For complete buoyancy, to float the ship as a whole, there was still required about 243 tons. The only factors in the above table which were uncertain were the buoyancies in the first, third, and fourth pairs of pontoons. The first and fourth pairs of pontoons were supposed to ----------------------------------------------------------------------- Page 45 have just enough buoyancy to float themselves with a moderate margin; they were all leaking and had their valves closed to minimize this leakage. The third pair of pontoons, the only pair which showed no leaks, had once been completely dried and had since had 60 tons of water flooded back in them (estimated). The "S-51" was practically upright, with a slight port list (less than 5 degrees), but with her stern a foot or two higher and her bow the same amount lower than when first sunk. Diving work ceased at 10.30 p.m. on the night of June 21, 1926, everything being ready, but it was then too late to undertake the work of raising, in addition to which both divers and deck force were completely worn out, both from long-continued exertion and from the special strains of the last three days drive to level off pontoons and complete the work. There is no doubt, however, that with conditions as they were on June 22, had the weather been satisfactory, that the "S-51" would quickly have been raised stern first as planned, shortly after blowing commenced on the stern pontoons and the reflooded engine room. Considering the buoyancy then known to be available forward, the bow would have followed with the addition of no great amount of air forward. The 22d of June dawned in a storm, which grew worse as the morning advanced. Diving was out of the question and raising the ship in such weather was not to be thought of. Had it not been for the known leaking condition of the pontoons, the delay caused by the storm would have been welcomed as giving the worn-out salvage crew a chance to recuperate before proceeding with the work and strain involved in raising. But with the experience of four different pontoons sinking after being leveled off, and with the leakage from a number of pontoons then visible at the surface, the enforced delay was an added aggravation. There was nothing to do, however, but to attempt to hold the situation as it was. With that in view, the "Falcon", headed south into the storm and opposite to the heading of the "S-51", succeeded in mooring over the wreck after considerable difficulty for the purpose of giving the leaking pontoons a brief blow, estimated at 2 tons of buoyancy per pontoon. It was intended immediately after this to unmoor and run inside the breakwater at Point Judith for shelter from the southwest storm. The "Falcon" first picked up the hoses to the stern pontoons and blew through them for one minute. The hoses for the after pair of pontoons were then buoyed off and put overboard, after which the group of hoses for the No. 3 pair of pontoons was brought aboard and given a half minute blow. These hoses were also then buoyed off. Nothing was done to the No. 2 pair of pontoons, as they had been previously blown completely dry and had had their flood valves closed for several days. On a trial the night before they showed as having made but little water and it was felt that they could be safely left another day. Some delay ensued before the set of hoses to the bow pair of pontoons (No. 1 pair) could be brought aboard. The hoses of this set were swept under the "Falcon"'s stern and caught in one of the propeller blades. It was necessary to clear these hoses, as the bow pontoons would sink if the hoses parted. As no divers could be put overboard in the storm, the work was attempted from a surfboat. Clearing the hoses was to some extent aided by the storm, as in the trough of the sea the fouled propeller blade could be reached with a boat hook. Working in this manner, the hoses were gradually dragged clear, though on one occasion, the salvage officer who was handling the boat hook barely escaped being crushed when a wave caught the surfboat under the counter of the "Falcon" and dashed it against the ship. The hoses, having been freed, were taken aboard and were being hooked to the manifold, preparatory to turning on the air. About 40 minutes had elapsed since the No. 3 pair of pontoons had been disconnected and its hoses put overboard. The salvage officer had just stepped aboard from the surfboat to direct the blowing, when a huge mass of bubbles started to break the surface under the "Falcon's" port quarter. At first glance, it was thought that after all the ----------------------------------------------------------------------- Page 46 hose had carried away from the bow pontoons, but the volume of air was excessive for such an accident. It was immediately sensed that either the bow pontoons had torn loose and were coming up, or the submarine itself was rising. In either case the "Falcon" was in a precarious position and speed was essential. The mooring lines to the stern were on the winches and the winch men at the throttles, preparatory to unmooring. The port quarter line was cast off and the starboard quarter line heaved in full speed to haul the "Falcon's" stern to starboard. The stern was barely clear of the bubbles when in a cloud of spray the bow pontoons burst through the surface, followed quickly by the second pair, with the bow of the submarine visible between them. The "Falcon" sounded her whistle as an emergency signal to the other vessels present, and let go her port bow lines to keep clear in case the stern of the "S-51" came up. The sea promptly carried the "Falcon" to leeward, but her commanding officer quickly worked her back in position about 40 feet from the "S-51's" port side. The handling of the "Falcon" in this emergency was magnificent; it unquestionably saved her stern from serious injury and probably saved the ship herself from becoming a total loss. Meanwhile the four pontoons at the surface were plunging heavily against each other as the seas swept over them and action was required. A hasty estimate of the situation resulted in the decision that the best course of action was to raise the stern and attempt as speedily as possible to get to a lee to the northward of Block Island about 15 miles away, the storm being from the southward. The danger faced was that the pontoons might be so badly battered against each other as to cause the ship to sink again on the way; it was also possible that the dynamic strains might part the cradle chains with the same result. Still, on a northerly course, the sea would be astern and the pontoons might ride more freely; finally as such a course led to more shallow water about 8 miles away and passed over no deeper spots, it was at least hoped that if the ship sank in the course of the tow that it would occur in water of a lesser depth than that in which she then lay. Accordingly all the reserve blowing hose being held on the "Vestal" was sent for and coupled up to the buoyed ends of the hoses afloat at the surface and leading down to the pontoons and the compartments on the submarine. Air was turned on each compartment as soon as it was coupled up; the "Falcon's" compressors were all called into action, but were unable to keep up much excess pressure under the large demand. To help out, the "S-50" was worked into position close aboard the "Falcon" by her commanding officer and an air line run between the ships, but the "S-50's" anchors failed to hold against the storm, she was unable to maintain her station, and the "Falcon's" air plant was compelled to carry the whole load. To furnish enough air in this manner required over two hours, but there was no help for it. To make the situation worse, it was realized that hardly one-half of the expected buoyancy of the C.O.C. and not over one-third of the expected buoyancy of the engine room now could be obtained. This followed from the fact that these two compartments which had once been dry had been reflooded - the C.O.C. accidentally and the engine room purposely, with the object of preventing a premature rise. It so happened that the spill pipes in the C.O.C. and engine room hatches and the discharge line from the motor room all were located in the forward ends of their respective compartments. With the ship up by the stern, this would permit discharging water until the compartments were wholly dry (which was one of the reasons the plan called for raising the "S-51" stern first); but with the bow up, as was the case actually, the ends of the spill pipes became exposed for the escape of air long before the compartments became dry and no more buoyancy could be realized from them. This resulted in a loss of attainable buoyancy in these three main compartments of about 130 tons. However, practically all of the buoyancy of the stern pair of pontoons was reserve ----------------------------------------------------------------------- Page 47
Figure 14: Engine room salvage hatch in position.
(Note three air connections.)
----------------------------------------------------------------------- Page 48 for contingencies and towing and was not normally required for lifting; it therefore appeared that the stern could be brought up, but with only a slight margin. On the surface, when the stern leveled off, all the residual water could then be blown out of the after compartments and the ship would float with the reserve buoyancy called for in the plan. About one hour after blowing commenced, a steady stream of bubbles showed over the middle of the ship. It was evident that in the C.O.C. the air had reached the bottom of the spill pipe and no more buoyancy would be obtained there. It was soon determined that the No. 3 pair of pontoons was also dry, leaving only the motor and engine rooms and the No. 4 pair of pontoons on which blowing continued. About noon, a sizable bubble which appeared over the stern, and then increased, for a moment made it seem that the stern was rising, but that hope was dissipated at once when the starboard after pontoon broke through the surface alone, to be followed in about five seconds by the port after pontoon, when both pontoons drifted to leeward (fig. 15), meanwhile fouling the remaining hoses to the "S-51". These were cleared, allowing both pontoons to float to the northward, where they were picked up and towed to Point Judith. It was observed that the 2.5-inch chains had parted under the submarine; the broken ends of these chains could still be seen dangling in the hawse pipes of the pontoons. Deprived of the No. 4 pair of pontoons, it was mathematically certain that the stern would not rise, but as a forlorn hope, the air was kept on the motor room and the engine room until, shortly after, a discharge of air at the surface over them showed that the limit had been reached in their buoyancy. The stern did not rise. The situation of the "S-51" was now desperate. By no possibility could her stern be floated. In the three hours that had gone by since the bow rose, the four pontoons had been violently pounding each other. The wood sheathing on the forward pair was coming off in large patches and floating away. The pontoons no longer held their fore and aft alignment but had been driven by the sea into a huddled group at the stern where the No. 2 starboard pontoon was riding on top of the pontoon just forward of it, and the two pontoons on the port side were lying at a considerable angle to the "S-51". As the pontoons swayed and plunged, their chains, especially where they passed under the keel, were subjected to severe punishment and to terrific shocks. It did not seem possible that they could stand such strain; it was certain that they would not hold out until the storm moderated and the lost pontoons could be replaced under the stern. (See fig. 16.) A canvass of possibilities was made. Towing was suggested; one towline was already round the bow; more could possibly be attached. This proposal was ruled out, as the boat had a negative weight of considerably over 100 tons and it was questionable whether under smooth conditions such a weight could be dragged over the bottom with the propellers digging in as anchors; worse still all the buoyancy of the "S-51", to gain which so many desperate chances had been taken by the divers, was in the stern compartments. A 15-mile tow with the stern on the ground would irretrievably ruin the water-tightness of this half of the ship and make her final raising perhaps impossible. The suggestion to tow was promptly overruled. This left as the only course of action the sinking of the bow, which was bound to take place soon in one way or another. There was reason to believe that if left to themselves the chains would soon break. (This was afterwards confirmed by the condition of the chains when brought up for inspection.) When the chains broke, the heavy bow would have a free fall to the bottom with resulting damage that would complicate an already bad situation. On the other hand, if the pontoons were allowed to flood and sink gradually, the chances were good that the bow would go down slowly and the "S-51" would as a ship be no worse off when she settled on the bottom than before she rose.
Figure 15: Stern pontoons which broke free from submarine,
June 22, 1926.
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