- Design and Construction
- Air Systems
- Crew Quarters
- Communication, Radio, and Navigational Systems
Two officers of the Regia Marina’s “Genio Navale” (engineering) generated the most popular submarine designs in use by the Italian Navy’s submarine fleet: Cavallini and Bernardis. The “Cavallini” were produced in seven distinct classes and they all evolved from the “Mameli Class”, built starting in 1925. Two years later came the “Settembrini Class” from which, in 1931, evolved the “Archimede Class”.
The subsequent classes, “Brin” in 1936, and “Liuzzi” in 1937, were further evolutions, while the minelayers “Micca” (1931) and “Foca” (1936), and eventually the transport class “R” (1941) were partial evolutions, or adaptations of the original design. Technical differences between the various classes were in some areas modest, while in other areas far greater.
The evolution of the submarine type Cavallini
Ultimately, they could all be classified as an evolution of the original “Mameli” class due to the adoption of the partial double hull, better known as the “Sattletank” (saddle tank) design, typical of the German U-Boats. The partial external hull extended for about 70% of the total length of resistant hull. All the “Cavallini” were built by the shipyard Tosi of Taranto, and the various boats of the class “R” assigned to other shipyards in the North were never completed. The first class designed by Cavallini in collaboration with the Tosi of Taranto was, as already mentioned, the “Mameli“ class. These boats were known for their strong design, good speed and maneuverability, and especially excellent habitability. These characteristics were maintained throughout the evolution of the d
Design and Construction
Since the creation of the first submarines, and not until the introduction of more revolutionary designs later in WW II and in the post-war period, submarines were made up of three distinct components: inner hull, outer hull, and superstructure.
The Saint Bon under early construction. The circular beams are clearly visible
The inner hull, also known as the pressure hull, was usually built of various cylindrical sections sealed at both ends by semispherical cups from which protruded the torpedo tubes. A second cylindrical area was positioned amidships and was enclosed in the conning tower. The outer hull was the seaworthy external shape of the submarine designed for navigational qualities. Within this outer shell there were compartments utilized for the storage of fluids (ballast or oil), external ballast or compensation tanks, and very little unutilized space.
The two half spherical extremities of the Ammiraglio Caracciolo where are clearly visible the opening for the torpedo tubes
The superstructure was constructed on top, aft and forward of the hulls and giving the submarine a flat deck, a cruiser-like bow and a round stern. This part was usually completely open to the ocean and seawater drained through wide openings above the outer hull, or smaller cutouts placed along the whole profile. The “Settembrini” class, which followed the “Mameli” had the shape of the hull improved, thus improving the navigational qualities of the vessel. Although larger (more displacement, longer and wider hull), the “Settembrini” class was capable of reaching 18 knots versus the 17.2 of the “Mameli”, even though they were sharing the identical power plant.
All the “Cavallini” class submarines were of the saddle tank, or partial double hull design. The “Mameli” class had a perfectly cylindrical pressure hull made of cylindrical beams (reinforcement rings) positioned 500 mm (19.69 in) apart and to which were riveted multiple steel plates positioned in a brick layer fashion (each plate tended to overlap the other half of the adjacent plates). Plates were made of nickel steel with a breaking point of 60 kg/mm2 (853.4 psi), and an enervating point of 42 kg/mm2 (597.4 psi). Plates were 18 mm (0.7087 in) thick around midship and 16 mm (0.6299 in) thick toward the extremity. The forward and aft sections were tapered so that the internal circumference of the supporting beams was larger in the central compartments than the extreme ones. Each plate was secured by a double row of rivets, and an extra plate was installed inside and outside of the riveted area.
The entire pressure hull was divided into five primary compartments plus the control room. Starting aft, the first compartment was the aft torpedo room which also included the electric motors, followed by the diesel engine rooms, the control room, the officer and petty officer quarters and first battery holds, and finally the forward torpedo room and the second battery hold. Above the control room there was a smaller chamber (conning tower). The two periscope sleeves were also considered parts of the pressure hull.
A watertight bulkhead capable of withstanding water pressures up to 40 atmospheres (853.4 psi) separated each compartment. Later evolutions of the “Cavallini” had this bulkhead reinforced. The outer hull was made of 7 mm (0.2756 in) steel, and as already mentioned, the space in between the two hulls was used to stow diesel fuel and ballast water. On each side (in each saddle) there were two water tanks and a diesel fuel tank. The upper deck was surfaced with teak wood slats bolted to the metal frame. The shape of the bow varied from class to class. The “Mameli” had a round bow and a sloped stern. The “Settembrini” had the bow redesigned in more geometrical lines. The same designed was kept on the “Archimede”, but the later classes returned to a round bow, while the “Liuzzi” also had an elongated stern.
The “Mameli” class was powered by two Franco Tosi “S8” eight cylinder diesel engines capable of producing 1,500 HP (1119 Kw). These were four-stroke motors with a primary crankshaft to which were connected the pistons; they could not be reversed (they only rotated one way). The engines were directly connected to a four-stage air compressor which produced air at a pressure of 70 Kg/cm2 m (995.6 psi) and which was also used (in reverse) to start the engines. The “Settembrini” kept the same engine configuration, but the “Archimede and “Brin” were equipped with the new Tosi E6, a six-cylinder, two-stroke reversible 1,700 HP (1268 Kw) diesel engine which, on the “Liuzzi” were replaced by the EG, a similar model with about 10 extra horsepower. The various power plants did not directly effect the surface speed of the boats, but rather their endurance.
The 8-cylinder diesel engine Tosi S8 capable of generating 1,500 HP
The “Settembrini” were faster than the Mameli (18 v. 17.2 knots ) and the “Brin” were faster than the poorly conceived “Archimede” (17.47 v. 17 knots), and finally the “Liuzzi” were technically capable of 17.8 knots. With continuous use and the general aging of the boats, these values became hardly achievable, especially toward the end of their operational livesMine
. On surface navigation, the engines were connected to the primary axels via a clutch joint, while the axels were connected to the propeller shafts by a geared joint. The geared joints could be disconnected from the propeller shaft and connected to the electric motors, thus turning them into dynamos for the production of direct current. While submerged, the clutch joints were fully disengaged. The two diesel engines received their supply of fresh air from an intake place above deck within the conning tower. The intake was protected by a large valve, which, while the boat was submerged, was sealed.
On the “Mameli” the two electric motors (double coaxial armature winding) were produced by C.G.E. and capable of producing up to 550 HP (410.1 Kw) each. All subsequent models were fitted with motors produced by Ansaldo. The motors on the “Mameli” were powered by direct current and could be supplied with 55, 110 or 220 volts. Each motor could be run at full speed (550 HP) for one hour, at 416 HP for three hours and at 66 HP in continuous motion. The Ansaldo installed on the “Settembrini” could also produce 550 HP, but those on the “Archimede” were capable of 700 HP (522 Kw), while the “Brin” were reduced to 650 HP and the Liuzzi to 625 HP. The difference between the various power plant solutions allowed for various endurance at maximum speed; the “Settembrini” performed worst (7 miles at 8 knots), while the “Brin” second series performed best (10 miles at 8.6 knots).
On the “Mameli” and the “Settembrini” there were two 56 cell storage batteries. Each cell was of the type 30 M.A.S. 870-5 produced by the SGIAE of Melzo (near Milan) and weighed 750 kg (1653 lb) The total weight of all cells was 84 tons (92.59 short tons). The batteries could deliver 5,150 amps in one hour, 7,500 amps in three (2,500 amps/hour), and 11,500 amps in twenty hours (575 amps/hour). This configuration was altered on the “Archimede” and these boats were fitted with a total of 128 cells divided into two compartments. The cells were of the type “Tudor Ironclad” and could deliver 4,270 amps in one hour, and 9,350 amps in twenty hours (565.5 amps/hour). The “Brin” were fitted with 132 cells also divided into two compartments. These cells were made by Scaini and could deliver 4,650 amps in one hour, 7,950 amps in five (1,590 amps/hour), 9,050 amps in ten (905 amps/hour), and 9,700 amps in twenty hours (485 amps/hour). The “Liuzzi” received smaller cells weighing 508 Kg (1120 lb) and produced by S.G.I.A.E. Each. There were a total of 232 cells, also divided into two compartments of 116 each, and could deliver 3,200 amps in one hour, 4,750 amps in three (1,583 amps/hour), and 7,300 amps in twenty-five hours (792 amps/hour). This configuration made the “Liuzzi” improve the original underwater range of the “Mameli”, 80 miles at 4 knots, to a respectable 110 miles at the same speed. Each cell was made of multiple positive and negative plates made of lead, each with common terminals, separated by insulators. The plates were immersed in an electrolyte solution made of pure water and pure sulfuric acid with a specific gravity of 1.250 when fully charged. Each cell produced approximately two volts and was permanently wired in series. Each of the two battery groups could be operated independently or in parallel. On the “Mameli” each battery group was divided into two busses, each composed of 28 cells (28 x 2 volts = 56 volts).
The compressed air system was one of the most important systems on the submarine. It was used to blow the ballast tanks, fire torpedoes, and to start the main engines. Without a functional air system the submarine became inoperable. Docking facilities were usually provided with the necessary high-pressure air supply so that the submarine would not have to produce its own. Air tanks dented to accumulate condensed moisture (water), thus they were regularly drained for maintenance. On the “Mameli” and “Settembrini” the primary air compressor was installed in the control room. It was build by San Giorgio and capable of pressurizing air up to 210 kg.cm2 (2987 psi) and producing 9 liters per minute (0.31 ft3 per minute). The compressor was powered by a 50 HP electric motor. There were also two super compressors, also built by San Giorgio, capable of boosting air pressure from 70 to 225 kg.cm2 (995 to 3200 psi), and producing 9 liters per minute. They were driven by a 10 HP electric motor rotating at 670 r.p.m. This system received air from the two compressors built into the diesel engines and air was stored into three tanks with a total capacity of 4,580 liters (162 ft3).
The “Archimede” had the air supply increased to 8,000 liters (282 ft3) and pressure reduced to 200 kg.cm2. The “Brin” probably maintained the same configuration, while the “Liuzzi” were equipped with a total of 5 tanks for a total capacity of 10,000 liters (353 ft3). Air was used to exhaust the ballast tanks only under emergency conditions; usually these tanks were exhausted utilizing two rotor-compressors of the type Reavel-Cerpelli, capable of producing 30 m3 (1059 ft3) of air per minute at a pressure of about 1.6 to 1.8 atmospheres. Each compressor absorbed 60 HP and rotated at about 1,600 RPM. These compressors could only be used when the submarine had at least the conning tower out of the water so that the hatch could be open to supply external air. The “Archimede” were fitted with four pumps, two capable of 50 t at 150 meters, and two of 30 t also at 150 meters. There were also two low-pressure blowers (less than 2 atmospheres) capable of 30 m3. The blowers shared the same electric motors as the pumps. The boats were also equipped with emergency pumps driven by low-pressure air or manpower.
Air Filtering System
The “Archimede”, and probably the previous classes, were equipped with an air regeneration system for the removal of CO2 (Carbon Monoxide). There were also a dozen 48-liter oxygen tanks loaded up to 150 Kg/cm2, and which were used to oxygenate the depleted air while submerged. The submarine was equipped with external hookups so that, in case of malfunction, a support ship could blow the ballast tank and also provide breathable air.
On the “Mameli” the officer’s area was arranged with four foldable bunks, which would turn into two sofas, much like on Italian train cars. The petty officers’ quarters had a similar arrangement, while the crew was divided between the two torpedo rooms. On the “Liuzzi” there were 18 foldable bunks in each torpedo room.
There were two galleys, one powered by electricity and located in the forward torpedo room, and one burning diesel oil and located within the conning tower. On the “Liuzzi” the internal galley was relocated starboard in the electric motors room.
There were three heads inside the submarine, and two inside the conning tower. Naturally, the galley and latrines inside the conning tower could only be used while on the surface.
The submarine had a total reserve of about 13.2 t of fresh water. On the “Brin” the water supply was increased to 14.86 t divided over 4 tanks. In the Liuzzi the water supply was increased to 15 t and an electric water purification system was also installed.
Oddly enough, on the “Archimede” the refrigerator for the production of ice and the preservation of fresh foodstuff was located in the aft torpedo room, and was made by Frigidaire. On the “Brin” the refrigerator was of domestic manufacturing, of the type Bazzi utilizing methylchlorid (CH3Cl). The “Liuzzi” utilized a system produced by the firm Canepa, and also utilizing methylchlorid.
The “Mameli” had a crew of 5 officers and 44 enlisted. The “Settembrini” had 6 officers and 50 enlisted, later reduced to 49 on the “Archimede”. The “Brin” had 7 officers and 47 enlisted, later increased to 50 on the “Liuzzi”.
Between the torpedo rooms and the internal compartments, the engineers had placed two Gerolami-Arata lifts. These devices consisted of a sealed chamber which would float to the surface by buoyancy and could then be retrieved by a tether connected to the bottom of it and secured to a winch. Each time the chamber was released it could take one crew member to the surface without incurring any of the dangers caused by exposing the human body to the high water pressure of the depths. Due to the presence of this device, the bulkhead between the torpedo rooms and the inner compartments was equipped with two hatches.
The “Archimede” was equipped with a gyrocompass of the type Sperry installed in the forward torpedo room which had three repeaters installed in various compartments (and also in the wheelhouse). There was also a magnetic compass installed in a water-proof casing on deck with a repeating station in the control room.
The gyrocompass received its directive from a high speed spinning gyroscope driven by electric motors. Its directive action is based on the mechanical laws governing the dynamics of rotating bodies. When any object is spinning rapidly it tends to keep its axis pointed in the same direction. The gyrocompass consists of a spinning gyroscope, made north-seeking by placing a weight below the axis, which is mounted in gimbals so that the movements of the submarine do not effect its position. A dial mechanically connected to the gyrocompass has the points of the mariner’s compass marked on it and indicates the submarine’s true course.
On the “Mameli” the radio equipment consisted of a 3 kW short-wave radio set (utilizing tubes), a 3 kW converter made by Marelli, a received model R.M. 1926 for short waves (300 and 1,200 meters), and second short-waves received (30 and 90 meters). On the “Archimede” the radio had only 1.5 kW. The antenna consisted of a stay and cables running forward and , aft almost the full length of the boat. The radio room was installed in the officer quarters, near the hatch leading to the control room. The “Archimede” were equipped with a radio localizer apparatus mounted on the conning tower and controlled from the radio room.
There was a hydrophone system connected to two transmitters mounted on the saddles and capable of emitting 150 watts. There were four receivers, mostly placed aft. On later classes (Brin), the number of receivers was substantially increased (16). On the “Mameli” the hydrophone station was placed in the aft torpedo room. On the “Archimede” Tosi installed a “Langevin-Florrison” echo sounder.
General announcing system
All “Cavallini” were equipped with an announcing system. Each compartment could communicate with a central station located in the control room via a speaker microphone system.
The “Cavallini” were equipped with a klaxon operated from the control room. Upon sounding the alarm, all hatches would be secured and the engineers would commence the diving procedures securing the diesel engines’ intake and exhaust valves.
Telephone call system
The “Cavallini” were equipped with two buoys situated on deck and attached to a retrieval system. If necessary, the buoys could be released and floated to the surface, giving surface units a telephone connection to the submarine.
There were two periscopes produced by the firm San Giorgio. The forward one, used to attack, was 8.5 meters long, while the aft one, used for exploration, was 11.5 meters long. The attack periscope was used in the small chambers placed above the control room, while the exploration one was used below, in the control room. Typical of Italian submarines, the periscope sleeves extended considerably from the conning tower and were enclosed in a light metal structure quite visible from a distance. In 1941, the remaining “Liuzzi” had the light structure removed and the sleeves reduced in size. Similar changes were made to the “Brin”, the remaining “Settembrini”, and the “Mameli”
When the “Cavallini” were on the surface, they operated like any other boat demonstrating good seaworthiness. Maintaining the various ballast tanks full of air provided buoyancy.
The rudder (semi-compensated) was controlled electrically from the control room, or manually for the aft torpedo room. Also, there was a wheel in the conning tower in an enclosed wheelhouse. On the “Mameli” the rudder had a total surface of 4.85 m2.
As standard on most submarines, the “Cappellini” were equipped with two sets of diving planes. The forward planes were collapsible (folded upward) for surface navigation and were placed above the waterline; their total surface was 4.96 m2 (on the “Mameli”). The aft planes were fixed and placed below the waterline in line with the two propellers and their surface was 5.14 m2 (on the “Mameli”). The forward planes were used to control depth, while the aft ones were used to control the angle of the boat. The planes were controlled electrically from the control room, but could also be manually operated from the torpedo rooms.
The “Archimede” were equipped with a primary anchor of the type Hall of 650 Kg and a smaller anchor type Admiralty of about 150 kg. There were two winches, one forward and one aft.
All “Cavallini” excluding the “Mameli” were fitted with four torpedo tubes aft and four forward. The “Mameli” had only two tubes aft. All tubes were loaded before leaving port and two extra torpedoes were stowed in each compartment giving the “Mameli” a total of 10 torpedoes, while all other boats had 12. Torpedoes were loaded through a special hatch and the operation was very laborious. Once at sea, torpedoes could be removed from the tubes for limited maintenance (fuel topping).
Range, speed and direction of the weapons could be configured while they were inserted in the tubes. The tubes, produced by Tosi, could take a variety of 21’ (533 mm) torpedoes produced both by Whitehead and “Silurificio Italiano”. Similar to the Royal navy, the Regia Marina did not experience the kind of massive torpedo failure which plagued the U.S. Navy and the Kriegsmarine. Italian weapons were reliable, but left a visible trail thus making them easy to spot.
Each boat was equipped with a small armory containing rifles and side arms.
The first two “Cavallini” classes were fitted with a 4” (102) mm deck gun caliber 35 produced by O.T.O. (Model 1931, 35 and 38). These guns had a maximum range of 14,500 meters, but the practical range, due to the simplicity of the optical range-finder, was much lower. Later classes were fitted with the newer 100 mm caliber 43, while the “Liuzzi” received a caliber 47. The “Cavallini” carried 22 kg Ap shells or smaller 13.8 kg. conventional shells. The “Mameli” had a reserve of 150 shells, increased to 200 on the “Settembrini”, 230 on the newer classes and further increased to 290 on the “Liuzzi”. The muzzle velocity, originally at around 730 m/s, was later increased to 840 m/s. A well-trained gunnery team could fire eight shells per minute. Shells were loaded from the stowage area below onto the main compartment and from there pushed up to the deck through a tube. Since there are no specifications for a mechanical or hydraulic hoisting system, it is assumed that the shells were pushed by hand. The gunners also had access to a ready storage area built into the conning tower and secured by a watertight hatch.
The Brin’s deck gun in is awkward position on top of the conning tower.
(Photo courtesy Erminio Bagnasco and Achille Rastelli)
The “Mameli” and the “Settembrini” had a single gun mounted forward of the conning tower. The “Archimede” had a second gun installed aft of the conning tower. The “Brin” were the most unusual; seeking to provide the gunners with a better platform protected from the elements and with a greater range of excursion, the designers fitted the gun on top of the conning tower. This very unusual installation, resembling some British classes, gave the “Brin” their unusual silhouette. Eventually, it was soon discovered that the arrangement was not satisfactory and never repeated. The “Liuzzi” returned to the field-tested single gun mounted aft.
All “Cavallini” were equipped with the famous Breda Model 1931 13.2 mm anti-aircraft machine gun. These guns were mounted on a single support on the “Mameli” and “Archimede” and on double mounts on all other classes. The guns were installed on a retractable mount which would recede into a water-tight tube protected by a small hatch. Upon emerging, the gunners had to simply release the hatch, lift the guns out of the enclosure, install clip and fire. Each clip contained 30 rounds and the gun could fire up to 400 rounds per minute at a range of 2,000 meters. The “Mameli” and “Settembrini” had a reserve of 6,000 rounds, reduced on the “Archimede” to 3,000 but later restored on the later classes, with the exception of the “Liuzzi” which had a reserve of 12,000 rounds. As with all Italian submarines, toward the end of the conflict it was discovered that the 13.2 mm guns were insufficient in downing large American bombers protected by a thick armor.
On the MICCA, the total capacity of the mine holds was 40 weapons. The mines, 20 aft and 20 forward, were lodge in pairs of two on rails. The mines were loaded from hatches located forward and aft of the deck guns. Each hutch would open on the deck below from which another hatch led to the holds.
The mine holds of the Foca
Each hold had its own separate ejection mechanism, basically a simple hatch opening downward and allowing the mines to exit the hull by gravity. The low speed of a submerged submarine and the ability of the crew to accurately measure bearing and speed would allow for the precise delivery of the weapons in the form of mine fields.