Navalization and Armament
The twelve Cimarron-class tankers funded by the maritime commission were built in response to the navy's need to have "twenty fast tankers," which could be rapidly mobilized in a national emergency.1 For this reason they had been designed "to conform to the approved characteristics for naval auxiliaries in speed, radius and structural strength" established by the General Board.2 Other features had been added to the design at the request of the navy to facilitate their conversion into naval auxiliaries in case of war. The total cost of these additions, collectively known as "national defense features," was borne by the government. Those actually incorporated during the construction were a paravane skeg (no gear); 40-ton kingposts and winch (for seaplane handling); magazine spaces (not fitted up); davits for refueling destroyers at sea (but no gear); two compartment subdivision; 161/2 knot speed, sustained fully loaded (80 percent power); 12,000 mile endurance at I65 knots; gun foundations (deck stiffening only); increased evaporator capacity; and a distiller for drinking water.3
Although well publicized by the press, these so-called national defense features were, with the important exception of speed, compartmentation, and extended endurance, only marginally helpful in preparing these ships for use by the navy. In the course of time each of the tankers acquired from the maritime commission would be extensively modified and armed in various navy yards. For ships obtained before the Pearl Harbor attack, these changes were usually made in a series of stages beginning at the time each was first taken over by the navy. Because of the urgent need to transport oil to the rapidly expanding naval base at Pearl Harbor, the Cimarron and the Neosho were commissioned as soon as possible, but were not extensively modified prior to service. Only those changes necessary to bring the ships up to navy standards were installed at that time.
Though classified as AOs, neither the Cimarron nor the Neosho could be considered true fleet oilers at this time since they had not
yet been fitted out with the specialized gear needed to perform the many service functions normally associated with oilers assigned to the Train. In addition to transporting fuel oil, navy auxiliaries were expected to carry and dispense diesel oil for submarines, lubricating oil for machinery, gasoline for airplanes, and gasoline for ship's boats.4Unlike commercial tankers, these ships had to be capable of maneuvering with the fleet and would frequently need to operate from remote moorings or anchorages. These activities required all types of additional equipment not carried by commercial vessels, such as ship's boats and oiling at sea gear. Since they would be operating in the war zone, fleet oilers also had to be heavily armed, particularly with regard to antiaircraft defense. This required a much larger crew than would normally be carried by a merchant ship of similar size, as additional personnel were needed to man guns, operate fire-control equipment, and pass ammunition. With a bigger crew came the need to provide all sorts of extra facilities in the way of more berthing spaces, larger galley facilities, extra storerooms, and so on. Lest the reader fail to recognize the problems that larger crew sizes created, it should be pointed out that as a merchant vessel, Cimarron was designed to carry a crew of only 69 officers and seamen; yet by war's end accommodations had been added for 34 officers and 267 enlisted men!5
Platte was the first of the T-3s acquired from the maritime commission to be extensively modified for service as a fleet oiler.6 After commissioning, she spent the early months of 1940 at the Philadelphia Navy Yard undergoing preliminary conversion. Major alterations made to the ship while in the care of the yard included changes and/or additions to (1) mess and berthing facilities; (2) fueling at sea facilities, including gear for heavy ships; (3) towing installation; (4) stowage and handling arrangements for cargo fuel oil, gasoline, diesel oil, and lubricating oil; (5) accommodation ladder; (6) navigation equipment; (7) signaling equipment; (8) searchlights; (9) [naval] radio; (10) life buoys; (11) ground tackle; (12) provision for darkening ship, telephones, man overboard, steering, blinker circuits, etc.; (13) arrangements of offices, storerooms, and service spaces; and (14) boats and boat-handling facilities.7 There is no evidence to indicate that any armament was installed, however, and no magazine spaces or fire-control equipment appears to have been fitted at this time. On the contrary, records found in the files of the Bureau of Construction and Repair indicate that the question of how these tankers were to be armed had yet to be decided.
Armament and Fire Control
As discussed earlier, the General Board played an important role in determining what features should be incorporated in the ships built for the navy. A ship's fighting capabilities and its capacity to absorb
battle damage was always of great concern to the board, which exercised great influence in this area and was frequently responsible for the ultimate decision regarding the size and number of weapons carried, the type of fire control to be employed, and the amount of armor required in a given class or type of vessel.
In 1929 the General Board approved a standard main battery for auxiliaries, recommending that repair, ammunition, and fuel ships carry four 5-inch antiaircraft guns.8 This recommendation formed the basis for the battery specified in the characteristics for oilers first formulated in the latter part of 1933. The General Board took no further action on this subject until 1937, when it conducted a study of the armament features for auxiliaries included in the building program for fiscal year 1938. As a result of this study, the General Board recommended
that the 5-inch, 38-caliber double purpose battery, fitted with the standard remote control, and a high powered searchlight, fitted for high angle searching, should be the standard equipment for large auxiliaries of the immediate future.9
The General Board's decision to provide this type of armament was dictated by the need to provide adequate antiaircraft defenses at the advance bases to be established under War Plan Orange and to protect the convoys supplying these bases. At the start of war, the navy expected that the only effective antiaircraft batteries available in any convoy would be those carried by naval ships manned by regular crews. Although oilers, transports, and store ships were not expected to remain at the advance bases for any length of time, they would be subject to air attack while under way--thus the need for dual-purpose guns with remote control direction. A secondary battery of 1.1-inch AA guns was originally considered when the characteristics for oilers was first proposed, but these were proving to be very expensive to develop and their installation would be limited to combatants only.10Instead of mounting the 1.1-inch gun, it was decided to mount eight .50-caliber machine guns as originally specified when the characteristics for oilers were first proposed.11
The General Board was well aware of the funding difficulties anticipated for the auxiliary building program and advised that savings could be made by "deferring the installation of the remote control features of the battery and the high powered searchlights until such time as funds become available."12 The General Board did state, however, that provision should be made for the future installation of these items.13 If further economies were necessary, the General Board suggested the temporary installation of "five-inch guns already on hand, and such fire control equipment as can be afforded," until funds were available to purchase new equipment.
In early January 1940, the General Board was asked to review the battery and fire-control equipment intended for installation on the Cimarron, Neosho, and Platte as part of their final conversion. The three oilers were among ten new auxiliaries recently ordered by the navy: Cimarron (AO-22), Neosho (AO-23), Platte (AO-24), Dixie (AD-14), Prairie (AD-15), Vulcan (AR-5), Fulton (AS-11), Terror (CM-5), Curtiss (AV-4), and Albemarle (AV-5). The Bureau of Construction and Repair expected all to be armed with 5-inch, 38-caliber, dual-purpose guns and planned to install the Mark 37 fire-control system then entering service with the fleet. In 1940, this combination of weaponry was the most advanced antiaircraft system in the world and was far superior to that of any other navy.
The Mark 37 system was an extremely sophisticated electromechanical fire-control system that automatically computed the necessary corrections needed to keep the guns and searchlights accurately trained on a fast-moving target while the ship was in motion, simultaneously providing the proper fuze settings to the projectile about to be fired. A complete installation consisted of the Mark 37 director mounted on the pilot house, a Mark 6 stable element to establish a horizontal plane of reference, and a Mark 1 computer, which trained the guns and searchlights electrohydraulically via remote control. The stable element and the computer were mounted in a plotting room below decks for protection and stability (fig. 9).
The bureau had already ordered the necessary remote control switchboards and fire-control gyro compasses for all ten auxiliaries and had begun wiring all except Dixie and Curtiss, which were being built on a "limited funds basis."14 The amount of money that could be spent on the latter vessels was limited by law and did not include the $353,000 price of the Mark 37 fire-control system nor the additional $34, 250 for installation. Note that the installed cost of a Mark 37 director was 12 percent of Cimarron's purchase price!
Admiral Richardson, U.S. Fleet commander in chief, felt that it would be better to transfer the funds needed for the Mark 37s to the Dixie and the Curtiss. Richardson included his concerns on the subject in his comments on the final conversion of the fleet oilers Cimarron, Neosho, and Platte, which were solicited from the fleet commander in accordance with the design policy then in effect. His comments on the proposed ordnance installation for fleet oilers included the following:
It is noted that the fire control equipment proposed is of the latest design and appears out of proportion to the type. There is no objection to its installation, but in view of the fact that many combatant ships have installations inferior to that proposed for the Cimarron it is considered that they should be given preference.
Fig. 9. Schematic diagram of the Mark 37 fire-control system. The Mark 37 was specifically designed to meet the anticipated threat of air attack. It could automatically compute the corrections needed to keep guns and searchlights accurately trained on a fast-moving target while simultaneously providing fuze settings. (U.S. Navy)
He proposed that the fire-control equipment be diverted to the Dixie, and the two other tenders (Curtiss and Fulton) then being built. Admiral Richardson questioned whether the crew of a tanker had the ability to maintain such a highly technical installation.15
Adm. Harold E. Stark, then CNO, forwarded Richardson's comments to Secretary of the Navy Charles Edison who asked the General Board to study the recommendations.16 Before holding a hearing, Adm. J. W. Greensdale, chairman of the General Board, asked the chiefs of the Bureaus of Ordnance, Engineering, and Construction and Repair their opinions "as to the relative merits of the standard remote control."17 The responses received by Admiral Greensdale are of interest because they show what the various bureaus were thinking and illustrate how decisions were reached within the navy's hierarchy.
The Bureau of Ordnance recommended against installing remote fire-control equipment on oilers, supply ships, or submarine tenders, unless the latter were assigned personnel to support the latest remote control. Its recommendation was based on the belief that naval personnel capable of operating and maintaining the "complicated fire control equipment involved" would not be assigned to auxiliaries.18 A fire-control system using sophisticated directors required considerable upkeep by trained personnel and were considered "practically worthless" unless they were kept in proper adjustment. The opinion expressed by the Bureau of Ordnance was strictly technical in nature failing completely to take into account the desired effectiveness of fire. While not the province of the Bureau of Engineering, I. H. Chad-wick took it upon himself to provide a more thorough analysis. Writing to Admiral Greensdale directly, he stressed the proficiency needed by gun crews to achieve effective fire and the extensive training required to attain this proficiency. Although the standard remote control system required careful upkeep to be effective, the proposed alternate, the follow-the-pointer system, required a carefully trained gun's crew. In general, he wrote:
The fewer the automatic features, the greater the proficiency required of gun crews. The number of officers and men required in the control parties for any system [of fire control] does not vary materially. Further, it is considered probable that tankers and supply ships will have more occasion to utilize their battery in a seaway than will tenders or repair ships. It is fairly well established that standard automatic control is the most accurate system available when firing with considerable motion on the ship. It therefore appears mandatory that a great deal of time be devoted to training gun crews on auxiliaries not fitted with remote control of guns if their fire is to be effective. The question of availability of qualified fire control men must be balanced against the man-hours required for training gun crews. With remote control now standard
on all combatant ships recently constructed, and the increasing familiarity of personnel with the system, the upkeep on auxiliaries should not involve insurmountable difficulties.
In view of the opposition that tankers and supply ships are likely to encounter (high-speed surface ships, airplanes, and submarines), and in consideration of the fact that their battery must be suitable for use at sea, it is obvious that any system of fire control which does not permit immediate and rapid fire with a high degree of accuracy is worthless.19
The General Board's solution addressed the issues raised by Admiral Richardson without compromising on its original recommendation. On the one hand, the General Board reiterated its approval for a main battery of four 5-inch, 38-caliber, dual-purpose guns with standard remote control and explicitly stated that no distinction should be made between the large tenders and tankers currently under construction or conversion. In regard to the particular problem presented in the case of the tender Dixie and the other large auxiliaries to which the "limitation of funds" applied, the General Board recommended that the fire-control equipment be reallocated as proposed by Admiral Richardson, with the provision that the priorities governing the timely acquisition of the fire-control equipment "be regulated by the completion dates of vessels under construction and other considerations involved."20 The General Board's recommendation was endorsed by the chief of naval operations on 13 February 1940 and approved by the secretary of the navy on the twenty-first of the month.21
Main Battery Installation
The Cimarron was the first of the navy's T3-S2-A1 tankers to be fully converted and armed as originally specified by the General Board.22 She was extensively modified during her six-month stay at the Philadelphia Navy Yard following her arrival on 22 September 1940.23 She was equipped with a main battery of four 5-inch, 38-caliber, dual-purpose guns, the most advanced antiaircraft weapon developed to that date. These were centerline mounted: two were located forward on the forecastle and two were placed on the after deck house. All mounts were provided with hydraulic control so that they could be remotely controlled from a central director. The forward guns were enclosed in gun houses to protect them from spray while those aft were left open to save weight. To permit both of the forward guns to be trained and fired directly over the bow, the number two gun was mounted atop a raised gun shelter that had been installed on the main deck just aft of the bulkhead forecastle. The mounts aft were installed on top of the after deck house: number three mount forward of the engine casing skylight and the number four mount directly aft of the stack. All guns were installed on roller-path (base ring) type mounts with ammunition handling rooms directly below the guns. The use
of a roller path (as opposed to a pedestal mount) eliminated the need to have ready service ammunition boxes near the guns (a dangerous practice that the navy preferred to avoid if possible) and allowed the use of a power-operated ammunition hoist that automatically set the projectile fuze as it was lifted from the handling room to the gun compartment. This was an extremely important feature for a weapon intended primarily for use in antiaircraft defense, since it eliminated the added error inherent in manual fuze setting (fig. 10).
Before the advent of the proximity fuze, the use of gun fire to bring down an attacking aircraft before it came within close range was an exceedingly difficult task. The navy tried to solve this problem by developing the 5"/38 in combination with the Mark 37 director. The former was designed for high rates of fire and could be easily loaded even when the barrel was elevated at high angles. This was accomplished by incorporating a power rammer into the breech mechanism and developing a brass-cased powder cartridge separate from the projectile so that both would be light enough to be easily handled by the gun crew. This permitted extremely high rates of fire for the manually loaded 5"/38 gun. Though rated at fifteen rounds per minute for sustained fire, rates as high as twenty-two rounds per minute were achieved for short periods of time. A high rate of fire was so important that virtually every ship mounting the 5"/38 carried a practice loading machine so gun crews could perfect the timing and teamwork needed for fast loading of ammunition. Cimarron carried hers on the portside after deck house next to the engine room skylight (fig. 11).24
The Mark 37 fire-control system was also installed during the ship's protracted stay at the Philadelphia Navy Yard. It consisted of two main elements: a topside director and analog computer below decks, which calculated fire-control solutions that were automatically transmitted to the individual gun mounts and fuze setters. The system could be operated in three modes: (1) Fully automatic--all functions remotely controlled; (2) Semiautomatic--train, elevation, and fuze settings transmitted to the mount and "matched" to pointers by the gun crew; and (3) Local control--for manual control in the event of power loss or battle damage.
The director was mounted on a 9-foot diameter steel cylinder atop the pilot house and was connected to the computer by a series of cables that ran through an armored tube positioned just aft of the main deck. The armored tube terminated in a plotting room situated within the island structure on the main deck. Fire-control circuits, remote control switchboards, a battle announcing system, and an underwater log were also included as part of the fire-control system.25 The entire installation--guns, mounts, director, and fire-control computer--was the latest and most up-to-date of its type then available.
Fig. 10. A 5-inch, 38-caliber enclosed gun mount and handling room. The latter eliminated the need for ready service ammunition--always a potential hazard--and facilitated the rapid handling of ammunition necessary for high rates of fire. (U.S. Navy)
Fig. 11. A 5-inch, 38-caliber open mount. The power-operated rammer was an innovative feature that permitted the weapon to achieve high rates of fire even when elevated at extreme angles. (U.S. Navy)
Secondary Battery and Searchlights
A secondary battery of eight .50-caliber machine guns was also mounted at this time. The guns were placed in pairs on both sides of the pilot house and on top of the after deck house. Those on the after deck house were mounted in echelon to provide a better volume of fire against attack from astern or either quarter.26 All machine gun mounts were surrounded by vertical shields of armored steel.27 Two 36-inch searchlights equipped for high-angle searching were also included as part of the armament. These were mounted on elevated platforms atop the after deck house and fitted for remote control from the Mark 37 director.
Armor and Ammunition
Ammunition for the main battery was stored in two magazines located below the waterline: one forward just below the chain locker in the forecastle and the other in the stern section just aft of the boiler and machinery spaces. These were fitted to store and dispense a wartime allocation of 1,200 5-inch antiaircraft projectiles, 200 5-inch illuminating rounds, and 1,400 cases of powder.28 Three dredger-type hoists were installed to facilitate handling of the main ammunition: one in each of the magazines servicing the number one and number four mounts respectively, and a third from the main deck to the forecastle servicing mount number two. Ammunition for the remaining mount
Fig. 12. The Mark 37 director. Mounted atop the pilot house on a steel cylinder 9 feet in diameter, the director operated with a staff of seven. (U.S. Navy)
(number three) appears to have been passed along the starboard passageway on the superstructure deck in the after deck house. Blast shields had to be installed on the after end of the gun platform to provide protection for the ammunition party working around the top of the ammunition hoist on the superstructure deck and on the starboard side of the number three gun platform to protect the ammunition party passing ammunition into the upper handling room of mount number three.29
Ammunition for the secondary battery was stored in a single small-arms magazine near the bow of the ship just above the 5-inch magazine. To insure an adequate supply of ammunition to the .50-caliber machine guns, ready service boxes capable of containing five Mark III ammunition boxes were installed in the vicinity of each machine gun group.30
As a ship's armor was also considered part of its armament, it was usually specified by the Bureau of Ordnance (especially in capital ships) and its costs were included along with the other items in a ship's armament such as guns, ammunition, directors, and so on. Splinter protection was the only form of armor installed on the Cimarron and the other vessels of her class. This consisted of various thicknesses (measured in pounds per square foot) of special treatment steel (STS) installed in the following general locations: direct wiring tube
from director to deck over plotting room; plotting room sides; navigating wheel house sides and top; bulwarks around working circle of guns; handling room sides, bottom, and top plating; and vertical shields and platforms for .50-caliber machine guns and 36-inch searchlights.31
Two other items classified as ordnance were the paravane gear (carried for mine sweeping) and the degaussing equipment. Details for the latter had yet to be developed and it was, therefore, not likely that it would have been installed on the Cimarron at the time she first underwent conversion in early 1941.
Evolution of Oiler Armament during World War II
Installation of the main battery called for by the General Board was a complex, expensive, time-consuming process. Before any of the navy yards could even begin to install any ordnance they needed to make the structural changes required to accommodate gun mounts, handling rooms, magazines, and the fire-control equipment. Such changes were made only to the Cimarron, Platte, and Salamonie, the latter while she was still under construction (see chapter 13). These three ships were the only fleet oilers to carry the four 5-inch, 38-caliber, dual-purpose battery originally scheduled. When the Neosho entered the
After "final" conversion, Cimarron departs from the Philadelphia Navy Yard on 29 April 1941 enroute to Baton Rouge, La., to pick up a load of black oil destined for Pearl Harbor. The ship was equipped with one of the first Mark 37 directors and four 5-inch, 38-caliber, dual-purpose guns--an unusual combination for an oiler. (Courtesy A. D. Baker III)
The third and last of the Cimarron-class to receive 5-inch guns and a Mark 37 director was Salamonie (AO-26). Taken on 4 July 1944 as the ship got under way from Portsmouth, the photograph shows her fitted with a Mark 4 fire-control radar mounted atop the Mark 37 director. Also shown are SC (on the topmast) and SA search radars. (Courtesy A. D. Baker III)
Puget Sound Navy Yard in mid-1941 for her final conversion, the enormous expansion in naval construction had created a severe shortage of these weapons and she was armed with three 3-inch, 23-caliber and one 5-inch gun on her stern.32 Sometime after Pearl Harbor these were exchanged for the new 3"/50s and a 5"/38.33 Because of difficulty in obtaining 5-inch, 38-caliber guns and Mark 37 directors, the Antiaircraft Defense General Board recommended the adoption of four 3"/50 guns with a simple director and the follow-the-pointer system as the standard antiaircraft battery for these ships.34 This recommendation must have been adopted since the standard armament of all future oilers commissioned prior to mid-1943 included four 3-inch guns and one 5-inch gun.
In 1942 the Bureau of Ordnance began to manufacture the Oerlikon 20 mm gun as a replacement for the obsolete .50-caliber machine gun, which was nearly useless. Although the 20 mm began to be installed in large numbers, the Cimarron did not receive any new weapons until she entered Mare Island Navy Yard in October 1942, when the four .50-caliber machine guns on her pilot house were replaced with 20 mm guns. Two more 20 mm guns were added in single mounts in
Cimarron under refit at Mare Island Navy Yard in November 1942. Major changes included modification to the fueling gear (cargo deck, raised winch platforms, etc.); replacement of the original .50-caliber machine guns with 20mms; addition of a Mark 4 fire-control radar (mounted atop the gun director); and addition of an SC search radar atop the mainmast. (National Archives)
gun raised gun tubs (port and starboard) installed on the main deck. A pair of 1.1-inch machine cannons, each controlled by a Mark 51 director, were also installed on the after deck house, replacing the .50-caliber machine guns originally intended for that location. This arrangement, or some variation thereof, became the standard oiler armament until 1944 when the Bofors twin 40 mm gun began to replace the 1.1-inch cannon on a one for one basis. By December of that year, still more AA guns were being fitted to the latest oilers of the Ashtabula class so that the total armament aboard these ships consisted of one 5"/38 dual-purpose gun, four 3750 AA guns, four 40mm AA guns, and eight 20mm AA guns.
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