CONFIDENTIAL |
|||||||||||||||||||||||
September 28, 1941. |
|||||||||||||||||||||||
REPORT ON THE GERMAN SUBMARINE OF THE |
|||||||||||||||||||||||
U-570 CLASS CAPTURED BY THE BRITISH |
|||||||||||||||||||||||
IN AUGUST 1941 |
|||||||||||||||||||||||
|
|||||||||||||||||||||||
|
|||||||||||||||||||||||
- 1 - |
|||||||||||||||||||||||
 |
 |
|
TABLE OF CONTENTS |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
- 2 - |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
PART I |
||
SECTION I - A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HISTORICAL: |
||
It is believed that the submarine was commissioned in May or June, 1941. According to the legend on the general arrangement plan, Enclosure (A), at least twenty-four submarines of this type were built or projected; viz |
||
U-551 to 562 and |
||
U-563 to 574 |
||
A brief story of the capture, beaching, and salvage of the submarine with pertinent comments of eye witnesses and others familiar with these occurrences follows: |
||
Sometime during the afternoon of 26 or 27 August, a British aircraft of the Hudson type picked up on its ASV (anti-surface vessel) radio echo ranging equipment an indication of the presence of a ship on the surface at a distance of approximately fourteen (14) miles. The plane proceeded towards the indicated vessel - assuming that it was an enemy ship. It was the German submarine reported on herein. At the time of sighting by the plane the submarine had dived - or was diving and had reached periscope depth by the time the plane arrived directly over it. The plane dropped a stick of four (4) two hundred and fifty (250) pound depth charges on the spot, set to explode at 50 foot depth. (The Captain of the U-570 claimed that he heard the plane before he saw it, and dived on hearing contact rather than on sight contact). |
||
Shortly after dropping the depth charges, the submarine surfaced and remained in the low buoyancy condition. The plane |
||
- 3 - |
||
|
|
|
circled the submarine and machine-gunned it. Very soon a white flag was raised on the submarine. British Icelandic authorities were notified of the surrender and they immediately despatched surface vessels and a relief aircraft to the scene. |
||
It was approximately twelve hours before the surface vessels arrived on the scene. During the night an aircraft patrol was maintained over the submarine. H.M.S. BURWELL (Ex U.S.S. LAUB) arrived on the scene early in the morning. Four trawlers had arrived on the scene just prior to the arrival of H.M.S. BURWELL. |
||
Upon arrival of H.M.S. BURWELL, that vessel circled the submarine and sized up the situation. The submarine appeared to be very low in the water. The first message received from the submarine was. - "Will you take off our crew?". to which the BURWELL replied, - "Blow main ballast tanks and send your crew below". No reply was received and no action was taken by the German crew to blow main ballast tanks or go below. |
||
Another message was sent, - "Do not attempt to throw any papers or books overboard and do not attempt to scuttle". An answer was received to this message. - "What does scuttle mean?" |
||
Very shortly after the above message was received the following message was received from the submarine, - "Will you take off our crew, we are sinking": to which the commanding officer, H.M.S. BURWELL replied, - "Blow fuel overboard". |
||
Since no action was taken to blow main ballast tanks or to blow fuel and since no member of the crew was observed to go below, the commanding officer of H.M.S. BURWELL opened fire on the submarine with a burst from one fifty caliber machine gun. Members of the |
||
- 4 - |
||
|
|
|
crew of the submarine were wounded and others rushed below decks. Ballast tanks and fuel tanks were then blown. (Air to the fuel tanks was not completely shut off until a boarding party boarded the submarine. Whether this was due to fright or was a deliberate attempt to deplete the air supply is not known). The reason that no attempt to board the submarine had been made up to this time was the bad weather. A very high sea wa running which, however, was moderating. |
||
After blowing tanks the submarine signaled, - "Will you take off my wounded"; to which BURWELL replied, - "Yes". After two unsuccessful attempts by the BURWELL to float a raft to the submarine one of the trawlers succeeded in doing so. The first persons to leave the submarine were its officers and not the wounded. A total of six wounded were later removed from the submarine. |
||
In view of the better maneuvering qualities of the trawlers in the still heavy sea after several attempts to float a line to the submarine by H.M.S. BURWELL, one of the trawlers was directed to take the submarine in tow. |
||
The removal of the entire crew from the submarine was completed about fifteen hours after the arrival of the surface ships on the scene. |
||
The commanding officer of H.M.S. BURWELL had not planned nor did he desire to remove any of the crew other than the wounded from the submarine until he had forced them to place the ship in as stable and sea-worthy a condition as possible. The enthusiastic, but somewhat untimely, interference of the trawlers resulted in loss of control of the situation by the commanding officer of H.M.S. BURWELL. |
||
- 5 - |
||
|
|
|
This interference by the trawlers very nearly resulted in the loss of the submarine and did undoubtedly result in the necessity for early beaching of the submarine. |
||
While the German crew was being removed from the submarine members of the trawler crew had succeeded in making the tow line fast and had also done some rather superficial and unintelligent inspection below decks. This first boarding party found the after control room door closed. They opened the door carefully and found considerable water in the engine room. This boarding party closed the after control room door and reported the engine room to be flooding, and also reported chlorine gas in the after battery compartment. Both of these statements were in error. There was never any evidence of chlorine gas in the submarine, in spite of the fact that approximately forty (40) jars were cracked as a result of the depth charging, and the water in the engine room was the result of a deliberate removal of a strainer bonnet during the early period of the surrender, but which had been replaced when the German crew realized that there were no surface ships present to rescue them. |
||
Also, during the period of removal of the German crew, a Norwegian aircraft flew over the submarine and dropped two small bombs nearby. The bombs did no damage nor did they cause any casualties. This plane was warned off by the commanding officer of H.M.S. BURWELL, but only after considerable discussion as to who was going to be allowed to sink the submarine. |
||
The initial intelligent but rather hurried examination of the submarine conducted by officers and men of submarine experience revealed the following conditions with regards to damage and stability: |
||
- 6 - |
||
|
|
|
1. All lights were out. |
||
2. The engine room was flooded to the floor plates. |
||
3. Numerous water gauge glasses were broken with small streams of water entering the ship. |
||
4. Many instrument faces had been deliberately smashed by the crew. The faces of all depth gauges except the one on the forward torpedo room were smashed, and the numerals were scraped off the dials of the smashed gauges. |
||
5. The ship was slightly down by the bow and listed slightly to port. |
||
6. About forty (40) battery jars were cracked. (The number actually cracked was not definitely determined until several days later). |
||
7. All compartments had been deliberately cluttered up with all sorts of debris including clothes, food, spare parts, etc. |
||
8. Some vents were not completely closed. |
||
9. Air banks were almost completely empty and air was still escaping to the fuel tanks. |
||
Sometime during the period of the removal of the German crew and initial examination of the ship, (exact time unknown) British intelligence officers from Iceland arrived; and thinking that the ship would undoubtedly sink very soon, they started a very hurried and rather unorganized examination of the ship and also began to remove all books, papers, plans, etc. During this period certain officers and men with submarine experience from the several ships that were present were engaged in activities to make the ship stable and sea-worthy. |
||
- 7 - |
||
|
|
|
The commanding officer of H.M.S. BURWELL decided that the proper and immediate procedure was to tow the submarine towards the nearest beach as quickly as possible so that the ship could be beached if necessary. This was done. |
||
During the period of towing, which was about twenty-four hours, the tow line parted. Another trawler took up the tow, but this time the submarine was towed stern first. During the period of towing it was noted that the draft of the submarine was gradually increasing and the decision was made to beach the ship as soon as possible. It had been planned to beach the ship bows on and to hold her in that position with appropriately located anchors. However, upon reaching the selected beach, the ship beached herself prematurely broadside to. |
||
After beaching and after arrival of a nucleus crew consisting of an experienced submarine commanding officer and several experienced enlisted men, a more detailed and careful examination was made: whereupon it was decided that the damage that had been done to the submarine was relatively minor, and that the ship should be refloated as soon as possible in order to avoid any further damage from the seas. |
||
Salvage personnel and equipment were immediately despatched from Iceland and within a day or so the ship was floated off and towed into Hvalfjordur, Iceland, and secured alongside H.M.S. HECLA, where action was immediately started to place the ship in an operating condition. |
||
During the period that the submarine was on the beach further damage was done, to the extent that the bow planes were rendered inoperative and the twin vertical rudders sprung out of alignment, resulting in difficult operation of same. No other damage was done as a result of the beaching in so far as could be determined. |
||
- 8 - |
||
|
|
|
Slow leaking of M.B.T. No. 3 was found to be due to a crack in the plating of this tank just below the saddle tank. The engineer officer of the tender HELCA stated that this crack was about 3 inches long and not at a weld. Leakage was stopped by installing an external patch plate over the crack. The patch plate was secured by studs shot into the tank plating by an underwater stud gun. It is not known whether this crack was due to the depth charge attack or not. |
||
When the ship was boarded the bases of lighting system fuze holders were found to be broken, and the fuses had dropped from the clips. |
||
One reason why this submarine was captured was the very fortunate condition which resulted in the protracted retention of the crew aboard the submarine. Actually the untimely interference of the trawler in removing the officers from the submarine, thus causing the commanding officer of H.M.S. BURWELL to lose control over the situation, very nearly resulted in the actual loss of the submarine. |
||
It appears that the surrender of the submarine was due entirely to the panicky and frightened condition of the personnel. This was due to their inexperience and lack of knowledge of the details of their ship - because the ship was not severely damaged and might have been able to escape during the night while guarded only by planes, if the lighting situation had been corrected as the main engines were fully and completely operative - in fact, the ship was quite capable of being operated submerged. |
||
The submarine has been operated on the surface by its British crew and was fully prepared to sail for the British Isles on 25 September, 1941. Due to the inoperative condition of the bow planes |
||
- 9 - |
||
|
|
|
and the poor condition of the battery it was not planned to operate the ship submerged. All preparations had been made on 25 September for moving the submarine to the British Isles. The exact sailing date is not known to the observers. |
||
- 10 - |
||
|
|
|
SECTION I - B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CIRCUMSTANCES OF INSPECTION: |
||
The observers sailed from Greenloch, Scotland, on 18 September, 1941, in H.M.S. BULLDOG, under orders to proceed to Iceland for the specific purpose of inspecting the captured German submarine; and , after completion of the inspection, to report to SOPA, U.S.N., for transportation to a port in the United States or Canada; and, finally to report to the Chief of Naval Operations, Washington, D.C. |
||
The observers arrived in Iceland at 2115, on 22 September, 1941, reported to SOPA, Admiral Munroe, U.S.N., in U.S.S. NEW MEXICO, at 0800, 23 September, 1941. After reporting to SOPA, the observers proceeded to H.M.S. HECLA and reported to the commanding officer of that ship under whose care and supervision the captured U-boat had been placed. The U-boat was alongside H.M.S. HECLA at the time. The commanding officer, H.M.S. HELCA, directed Lieutenant Colvin, R.N., acting commanding officer of the captured U-boat, to see that all facilities were made available to the inspecting officers. |
||
The photographs, Enclosure (C) and the photographic reproductions, Enclosure (A) and (B) were obtained with the invaluable assistance of Ensign R. O. Anderson, Jr., U.S.N., U.S.S. NEW MEXICO. |
||
- 11 - |
||
|
|
|
PART II |
||
TECHNICAL: |
||
SECTION II - A . . . . . . . . . . . . . . . . . . . . . . NOTES ON SOURCES OF INFORMATION: |
||
It is understood that, when the U-570 was captured, a complete set of ship's plans were aboard; and, that they were removed from the ship by British intelligence officers and sent to the Admiralty prior to the time of the inspection reported herein. Reproductions of these plans will therefore undoubtedly be forwarded to the Navy Department by the Naval Attaché, London. |
||
A general arrangement plan of the ship and a booklet of diagrams of systems were available on board. These were photographed. Although the photographs are too small for convenient use, a bound set of prints of the original negatives is forwarded herewith for record and reference purposes. The negatives are in the hands of the writers (28 September, 1941) and enlargements will be obtained through the facilities of the David Tay;or Model Basin upon their arrival in Washington. |
||
Permission was obtained from the British captain of the submarine to take photographs of the ship. Prints are forwarded herewith as Enclosure (C). The photographs were taken by a U.S. Navy photographer. At the request of the Captain of the submarine the negatives were left with the captain of H.M.S. HECLA for transmittal to the Admiralty. It was considered important to obtain a set of photographs prior to departure of the ship for the United Kingdom in view of the hazards of the passage. The Department may be expect to receive complete detailed information on all features of the submarine subsequent to the detailed examination by Admiralty and U.S. specialists to which all installation therein will undoubtedly be subjected upon arrival of the submarine in the United Kingdom. |
||
- 12 - |
||
|
|
|
SECTION II - B . . . . . . . . . . . . . . . . . . . . . . HULL AND FITTINGS: |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
CONTENTS |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
- 13 - |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|
SECTION II - B - 1. . . . . . . . . . . . . . . . . . . . . . GENERAL DESCRIPTION: |
||
(a) GENERAL PARTICULARS: |
||
TYPE: Saddle tank construction. |
||
LENGTH OVERALL: 220 feet (plus or minus 1/2 foot). |
||
DISPLACEMENT: Roughly calculated to be about ______ tons (See calculation p. hereof) in surface condition diving trim (M.B.T.'s and fuel ballast tanks empty). |
||
MAXIMUM DIAMETER OF INNER HULL: About 184-3/8" inches. (Note: This dimension is not exact. It was scaled on a 1:50 scale drawing). No clear space was available for actual measurement of maximum diameter. Maximum diameter obtains only for the length of the control room. A vertical diameter was, however, measured at the forward end of the engine room and checked within one inch of the diameter at this same location as scaled from the 1:50 drawing. |
||
TEST DEPTH: Not known. A depth gauge in the forward torpedo room; which, unlike the one in the control room, had not been smashed by the surrendering German crew, is graduated from zero to 200 meters - 656 feet. (See Section II-B-2 for thickness of inner hull plating and frame spacing). |
||
MAXIMUM SPEED (Surface) - - - - - - - - - - 17.8 knots |
||
MAXIMUM SPEED (Submerged) - - - - - - - - 8 knots |
||
TOTAL FUEL OIL CAPACITY: |
||
Internal fuel oil tanks No's 1 & 2 - - - - 18,680 U.S. Gals. |
||
F.B.T.'s No's 2 & 4 - - - - - - - - - - - 12,990 U.S. Gals. |
||
______ |
||
| TOTAL - - - - - 31,670 U.S. Gals. | ||
- 14 - |
||
|
|
|
September 28, 1941 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
U-570 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Summary of Calculation of Displacement |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Note: Approximation only. Work based on small scale photo of plan. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
- 14a - |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
ARMAMENT: |
|||||||||||||||||||||||
4 in No. 21" internal bow tubes. |
|||||||||||||||||||||||
1 in No. 21" internal stern tube. |
|||||||||||||||||||||||
1 in No. 88 m.m. L.A. gun. |
|||||||||||||||||||||||
1 in No. 20 m.m. A.A. gun. |
|||||||||||||||||||||||
TORPEDOES: |
|||||||||||||||||||||||
5 in No. in tubes. |
|||||||||||||||||||||||
6 in No. in F.T.R. |
|||||||||||||||||||||||
1 in No. in A.T.R. |
|||||||||||||||||||||||
2 in No. in outboard stowage tanks. |
|||||||||||||||||||||||
Total - - - - - - - - - 14 torpedoes. |
|||||||||||||||||||||||
(Note: Two (2) of the six (6) spare torpedoes in F.T.R. were apparently "carried in excess"). |
|||||||||||||||||||||||
ACCOMODATIONS: |
|||||||||||||||||||||||
One commanding officer's bunk. |
|||||||||||||||||||||||
Three wardroom bunks. |
|||||||||||||||||||||||
Four warrant officer's or C.P.O. bunks. |
|||||||||||||||||||||||
| Eight petty officer's bunks. | |||||||||||||||||||||||
| Twelve crews bunks in F.T.R. | |||||||||||||||||||||||
| British Officers stated that the total crew of the submarine when taken off (including both officers and men) was "about 50". The writers believe "about 40" to be more nearly correct. This figure can be and should be checked through the Naval Attaché, London. | |||||||||||||||||||||||
| (b) TABLE OF TANK CAPACITIES: | |||||||||||||||||||||||
|
|||||||||||||||||||||||
- 15 - |
|||||||||||||||||||||||
|
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(c) MATERIALS AND WORKMANSHIP: |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
In general the ship is beautifully built. Workmanship and finish throughout the ship appears equal to the best U.S. submarine practice. There is no outstanding evidence of use of substitute materials. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
- 16 - |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|
SECTION II - B - 2. . . . . . . . . . . . . . . . . . . . . . STRUCTURE: |
||
(See general arrangement plan Enclosure (A) and photographs Enclosure (C)) |
||
(a) The submarine is of the saddle tank type. The inner hull is cylindrical throughout the length of the control room and tapers toward the ends of the ship from the ends of the control room. The whole structure is welded construction with the exception of the superstructure side plating which is riveted, and portable plates in the top of the inner hull. Inner hull frames are internal and the webs of the bulb tee frames are connected to the I.H, plating by continuous welds on both sides of the webs of the frames. |
||
(b) SCANTINGS: |
||
Inner hull maximum diameter - about 184 - 3/8 inches. |
||
Frame spacing 23 - 1/2 inches. |
||
Thickness of I.H. plating at max. diameter - probably 7/8 of an inch. (The thickness was gauged at 7/8" at the A.T.R. loading hatch. A thickness of 3/4" was gauged at the F.T.R. loading hatch. A drill test in the control room started by the British had been abandoned before perforation, and a drill test by the observers was discouraged as the ship was standing by to sail on short notice. There were no exposed I.H. plate edges in the control room). |
||
Quality of I.H. plating: Not known. The chief engineer of H.M.S. HECLA stated that the plate was difficult to drill and he judged it to be a very high strength weldable steel. Drilling had been disposed of. |
||
Pressure hull frames are 7 - 3/4" deep bulb tees. The fore and aft dimension of the bulb is 2 - 3/8". |
||
- 17 - |
||
|
|
|
Main Divisional Bulkheads: The control room bulkheads are the only main divisional bulkheads in the ship which are built to withstand great pressure. They are dished bulkheads of 3/4" plate. They are peripherally tee welded where they meet the I.H. plating to a circumferential strap welded to the I.H. plating. Circular dished plate doors are fitted in the two C.R. bulkheads. The door locking arrangement is an interrupted flange ring mounted on the circular door frame. With the door on its seat, the locking ring may be rotated by a lever operated pinion which engages a rack on the locking ring. Rotation of the ring moves parts of the ring over peripheral lugs on the door and forces the door on to its seat. The diameter of the clear opening through the door is 31 - 3/4". |
||
Other main divisional bulkheads are made of about 15# plate, and 21 - 5/8" X 57" doors secured by six hand dogs, are provided in these bulkheads. |
||
End bulkheads are steel castings. |
||
- 18 - |
||
|
|
|
SECTION II - B - 3. . . . . . . . . . . . . . . . . . . . . . HULL FITTINGS: |
||
Galvanized floor plates are fitted in C.R., E.R. and A.T. & M.R. |
||
Net cutters, shown on the enclosed plans, are not fitted in the ship captured. |
||
Housing bitts and deck cleats are hollow welded construction. |
||
Windlass and capstan are operated by an air motor installed in the bilge between the two lower torpedo tubes in F.T.R. Wood decking is fitted on the superstructure. |
||
External torpedo stowage tanks are apparently made of a copper nickel alloy. |
||
Plans indicate a boat stowed on its side on the port side forward, but no boat was aboard the submarine when inspected. |
||
In each battery tank a trolley supported platform is provided which can be moved manually from end to end of the tank by a man lying thereon; and from which inspection of cells and battery watering may be accomplished. |
||
One anchor is carried. |
||
Pressure hull hatches are single action had wheel locking type with three lugs. |
||
- 19 - |
||
|
|
|
SECTION II - B - 4. . . . . . . . . . . . . . . . . . . . . . FLOODING AND VENTING: |
||
(a) There are three M.B.T.'s fuel-ballast tanks, a stern buoyancy tank and a bow buoyancy tank. (See Section II-B-1 for tank capacities). In this report tanks are numbered from aft forward. The middle main ballast tank is apparently constructed as a safety tank. |
||
(b) FLOOD VALVES are fitted in M.B.T. No. 3 in fuel-ballast tanks. (see Plan No. 28). M.B.T. No. 3 is directly below the C.R. flat and within the strength hull. M.B. Tanks No's 1 and 5 are open to the sea through flood openings in their bottoms. Flood valves are manually operated by tee wrenches or cranks used on the ends of operating gear shafting extending into working spaces of the pressure hull. (Areas of flood valve are shown on Plan No. 28). |
||
(c) VENT VALVES of M.B.T.'s and Fuel-Ballast Tanks are manually operated from the control room. The vents of bow and stern buoyancy tanks are operated manually by hand wheels in the forward and after torpedo rooms respectively. Vent pipes from Fuel-Ballast Tanks No. 2 and No. 4 starboard lead to a common master vent valve abreast and on the conning tower. Vent pipes from Fuel-Ballast Tanks No. 2 and No. 4 port lead to a similar master vent valve on the port side. Vent ducts from M.B.T. No. 3 starboard and port lead from openings in the I.H. into and through the regulating tanks which are adjacent to M.B.T. No. 3. Emergency vent valves are fitted on the lower ends of these ducts at the I.H. These emergency vent valves are operated manually from the control room by tee wrenches. The master vent valves of Fuel-Ballast Tanks No's 2 and 4 and the vent valves of M.B.T. No. 3 are quick opening lever operated valves. Hand operated |
||
- 20 - |
||
|
|
|
emergency vent valves are provided in Fuel-Ballast Tanks No's 2 and 4 port and starboard. The vents of M.B.T's No's 1 and 5 are operated by hand wheels in the C.R. |
|||||||||||||||||||||||||||||||||||||||||
Separate vent pipes lead from the after ends of F.B.T.'s No. 2 Stbd & Port over the inner hull to vents on the middle line. Emergency vent valves are installed in these vent pipes. The vent valves at the top of the inner hull are controlled by a single hand wheel in the control room. (See Plan no. 16). |
|||||||||||||||||||||||||||||||||||||||||
Certain accessible vent valves were measured to obtain data for calculating the ratios of tank volumes to vent valve areas. These data are: |
|||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||
(Note: This vent is an outward opening hinged type vent. All others are inward opening. It was closed and the clear opening could not be measured. The overall diameter of the valve was 22" (diameter of clear opening probably about 17").). |
|||||||||||||||||||||||||||||||||||||||||
(d) BLOWING: Main ballast tanks and fuel ballast tanks may be blown from the tank blowing manifold in control room. Supply to this blowing manifold from the high pressure flask manifold is manually |
|||||||||||||||||||||||||||||||||||||||||
- 21 - |
|||||||||||||||||||||||||||||||||||||||||
|
|
|
controlled by hand wheel (See Photograph No. 20). |
||
No low pressure blowers are installed. Arrangements are provided for low pressure blowing by engine exhaust gases. A pipe connection to the exhaust system outside of the hull leads forward to a manifold outside of the hull in way of the control room; and exhaust gases may be admitted to ballast tanks by operation of individual external valves from within the control room. (See note under Photograph No. 20). Admission of exhaust gases to this low pressure blowing system is controlled by a valve in the exhaust system outside the inner hull which is operated by a hand wheel in the engine room. |
||
- 22 - |
||
|
|
|
SECTION II - B - 5. . . . . . . . . . . . . . . . . . TORPEDO TUBES AND TORPEDO STOWAGE: |
||
(a) TUBES: |
||
Four (4) - 21" internal tubes forward. |
||
One (1) - 21" internal tube aft. |
||
STOWAGE OF TORPEDOES: |
||
Six (6) in forward torpedo room. |
||
One (1) in after torpedo room. |
||
One (1) in external tank forward. |
||
One (1) in external tank aft. |
||
(b) Torpedo tubes (21") are bronze. Torpedo tube shutters are fitted in the bow. Bow caps are mechanically interlocked with the breech door locking ring operating gear. |
||
(c) Bubbleless firing is provided for by admission of impulse air behind a skirted piston which bears against the tail of the torpedo. (See Photograph No. 13). The length of travel of the piston was not determined. The edge of the skirt of the piston registers with a narrow rubber gasket on the inside face of the breech door. This is possibly a bumper for receiving the piston upon its return to the breech end of the tube due to external water pressure when the tube is vented after firing. |
||
The small hand wheel at the center of each breech door is so fitted that by turning it, its stem moves axially. The stem extends through the door and registers with an adjustable screw plug on the cross piece at the skirt end of the piston. It is believed that this arrangement is a means for slightly advancing the piston in the tube prior to firing to break the seal between the edge of the skirt of the piston and the piston buffer on the tube-side face of the breech door, in order to permit impulse air to pass to the rear of the skirt. |
||
- 23 - |
||
|
|
|
Arrangements are provided for setting gyro angles on loaded torpedoes. These arrangements are discussed under "Part II - D - ARMAMENT". |
||
The original design apparently contemplated the stowage of only four reload torpedoes in the forward torpedo room. The two found in the upper row were apparently "carried in excess". They were covered over with a temporary board deck. |
||
Strongbacks used for handling torpedoes are shown in the photograph of the forward torpedo room. These strongbacks can be moved across the ship on transverse overhead rails by chain drive. Falls supporting torpedoes can be moved along the strongbacks by operation of pinions on the fall blocks which engage with longitudinal racks on the upper outboard edges of the strongbacks. A multiplicity of holes in the web of the strongbacks, all carefully identified by legends, are provided; apparently as location points for the several manipulations of the strongbacks in handling torpedoes. |
||
The deck storage tanks are provided with trunions at one end and are held in place by drop bolts which engage lugs on the sides of th |