View source for Dorado (SS-248)

{{#seo:|title=USS Dorado (SS-248) information and specifications.|keywords=USS Dorado (SS-248), USS Dorado submarine, Gato class US submarine information, Gato class submarine construction}}
{{#seo:|description=Information on USS Dorado including specifications and construction data.}}

<center>[[File:Dorado header Mk 2.jpg]]</center>

<center>
{| class="wikitable"
|+ 
|-
|[[The USS Dorado Project|Main Page]] || [[Latest News|Latest News & Updates]] || [[Dorado (SS-248)|The Submarine]] || [[Dorado Crew|The Crew]] || [[Dorado Photographs|Photographs]] || [[Dorado Loss Scenario|The Loss Scenario]] || [[Dorado Martin PBM Mariner aircraft|The Aircraft]] || [[Dorado Purple Heart|Case for the Purple Heart]] || [[Dorado Myths|The Myths]] || [[Dorado documents list|Research Documents]] 
|-
|}
</center>

<center>[[File:Subs bottom line 2.jpg]]

__TOC__</center>

==Introduction to the Gato-class submarines==

<div style="text-align: justify;"><span style="color:#00008B">The Gato-class fleet submarines, of which there would eventually be a total of 77 boats, were authorized in Congressional appropriations on June 14, 1940 for Fiscal Year (FY) 1941. This was the so-called Two Year Program. It called for additional 21,000 tons of submarines over and above what the Navy already had. The ink wasn't even dry on this authorization when the fall of France and the deteriorating situation in China prompted Congress to implement the add-on 70 Percent Expansion Act on July 19, 1940. This act authorized an additional 70,000 tons of submarine construction, for a total of 43 more boats, over and above the boats in the Two Year Program. Delighted with the new appropriations, the Navy's [https://en.wikipedia.org/wiki/Bureau_of_Construction_and_Repair '''Bureau of Construction & Repair'''] (C&R) chose to standardize on a single design for mass production. The new submarines, to be named the Gato-class, were slightly modified versions of the FY-39 and 40 submarines, the [[Tambor/Gar Class|'''Tambor/Gar-class''']].

A "fleet submarine" was a large submarine intended to operate directly with the main fleet battle line composed of battleships, aircraft carriers, cruisers, and destroyers. Their role was to range out ahead of the battle line and act as scouts. They were to find the enemy and report on their composition, course, and speed. They were to then conduct attrition attacks designed to weaken the enemy fleet prior to the main gun battle with the U.S. battle line. To accomplish this mission the submarines had to have a long range, high speed, and be heavily armed. The subs also had to be quite large in order to fit all of the necessary equipment to achieve these qualities into the pressure hull.

<div style="text-align: justify;"><span style="color:#000000">

===Early development===

[[File:Bass Argonaut Barracuda March 30 1930.jpg|right|thumb|300px|<small>V-2, V-4, and V-1 alongside the USS Holland (AS-3) in San Diego, March 30, 1930. Photo via PigBoats.COM.</small>]]<div style="text-align: justify;"><span style="color:#00008B">The USN's earliest submarines were of the [https://pigboats.com/index.php?title=Submarine_Classes '''harbor defense, coastal defense, and patrol types'''] and thus were too small, too underpowered, and lacked the necessary range to conduct the fleet submarine role. The Navy's first attempt to build a fleet submarine was the [[T-class|'''T-class''']] of 1916 and 1917. The state of the art in those years lacked the technology needed to provide the powerful engines and refined hull form required to get the high speed and sea-keeping qualities that the boats needed. The T-class was an expensive failure, but the Navy learned was wasn't going to work and rolled those lessons into future construction, which would become the [[V-class|'''V-class submarines''']] of the 1920s and early 30's.

The nine V-class submarines ended up being largely experimental in nature, as the Navy tinkered with several concepts brought out by WW I. The class not only consisted of fleet submarines, but also a specialized mine layer, two commerce raiding cruiser submarines, an open ocean patrol submarine, and two small fleet boats. The boats were either too big, too small, or they were too experimental in nature to be fully successful. All of them were underpowered, as diesel engine technology in the United States badly lacked in comparison with European designs.

The experience with the T and V-classes had taught the Navy what worked and what didn't when it came to building a fleet submarine, and by 1933 they had moved beyond the experimental stage and began solid progress towards what would become the Gato-class. The ten [[Porpoise Class|'''Porpoise-class''']] boats of 1933-1937 and the 16 [[Salmon/Sargo Class|'''Salmon/Sargo-class''']] boats of 1936-1939 were largely successful and proved to be solid steps up the developmental ladder. The 12 [[Tambor/Gar Class|'''Tambor/Gar-class''']] submarines of 1939-1941 were the ultimate ''peacetime'' refinement of the fleet submarine concept. Large, fast, and powerful these boats were highly regarded by the Submarine Service and their crews. When the FY-41 appropriation programs were being discussed, it was decided to "freeze" the design at that point for mass production. These boats became the famed Gato-class.

<div style="text-align: justify;"><span style="color:#000000">

===The Gato-class===

[[File:Growler port quarter 19-N-28443.jpg|left|thumb|300px|<small>Growler (SS-215), an early unit of the Gato-class, off Groton on February 21, 1942. Photo 19-N-28443 via NHHC.]]</small> <div style="text-align: justify;"><span style="color:#00008B">The Gatos were, as expected, very similar to the preceding Tambor/Gars. The Gatos were lengthened by five feet in order to accommodate a watertight bulkhead that divided the Tambor/Gar's one large engine room into two smaller ones. The C&R designers also realized that they had been overly conservative with the rating for the previous boat's maximum submerged safe operating depth (test depth) and with a stroke of a pen rated the Gato class with a test depth of 300 feet (91.5 m), a 50 foot increase over the Tambor/Gars. There were other refinements as well, like making both of the periscope eyepieces usable in the conning tower (a separate watertight compartment above the central control room) instead of the control room, essentially "lengthening" one of the periscopes.

The boats were engined with four now fully refined Fairbanks-Morse or General Motors Winton diesel engines in a "diesel-electric" (DE) arrangement, where the engines drove only electrical generators, with the electricity produced being sent to electric motors on each propeller shaft, or to recharge the batteries used for submerged propulsion. The FM and GM engines were hardy, rugged, reliable, and well liked by the crews and provided excellent service. Unfortunately, eight submarines of the class were equipped with Hooven, Owens, & Rentschler (HOR) 99DA diesel engines, which for several reasons were complete failures. Those subs were eventually re-engined with GM Winton units during wartime overhauls.

In early 1942 the Gatos and other USN submarines began to be equipped with a remarkable device: radar. The first sets were designated SD and were used to detect incoming aircraft while the submarine was surfaced. This gave the crew an advanced warning of danger in the area and gave the commanding officer information vital to keeping his boat safe. The second type was designated SJ and was used to detect surface targets day or night and in any weather condtions. The SJ radar was accurate enough to precisely track targets even when they couldn't be seen visually. The tactical advantage that this gave USN submarines can not be overstated; indeed it was a prime factor in the eventual overwhelming success of the submarine campaign against Japan.

<div style="text-align: justify;"><span style="color:#000000">

[[File:Mk III TDC.jpg|right|thumb|300px|<small>The Mk III TDC. PK on the left, AS on the right.</small>]]<div style="text-align: justify;"><span style="color:#00008B">The Gatos (like many of their predecessors) were equipped with an advanced version of the Torpedo Data Computer (TDC), an analog computer that was used to accurately aim torpedoes. The Mark III TDC consisted of two components: the Position Keeper (PK) and the Angle Solver (AS). Using automatic inputs for the submarine’s own course and speed, the operators input the target’s length, estimated speed, and angle on the bow based on periscope observations or radar tracking. The PK then solved the equations for motion integrated over time, and provided a continuous estimate of the target’s position. The AS took that input from the PK, combined it with the tactical properties of the torpedo, and solved for the needed torpedo gyro angle. It then transmitted this information to the weapons in the tube, setting the gyrocompass and running depth of the weapons automatically so that they would turn to a course to intercept the target once they left the tube and run at the depth necessary to hit the target. This was a significant tactical advantage, and the TDC became the envy of the world's navies. 

Significantly, like all submarines built since the Salmon/Sargo-class, the Gato-class boats were built to an all-welded construction method, as opposed to the more traditional riveted method. Welding made for strong and resilient pressure hulls that could take a lot of punishment and still survive.

The Gatos also had air-conditioning, a complete refrigeration plant for storage of food, stills for making plenty of fresh water, clothes washing machines, and enough bunks so that every crew member could have one of their own. Food was of uniformly very high quality, the best in the fleet, prepared in compact galleys that turned out the food in prodigious quantities. These were luxuries virtually unheard of in foreign navies, but they were absolute necessities if the crew were expected to conduct 60-90 day patrols in the warm waters of the Pacific Ocean.

These qualities made the Gato-class an ideal member of the nearly 232 submarines that the USN commissioned during the war. Along with the previous classes, and the follow-on Balao and Tench-classes, the Gatos had a significant and disproportionate effect on the outcome of the Pacific war, shooting the bottom out of the Japanese Merchant Marine and crippling operations of the Imperial Japanese Navy.

It is important to note that the Gato-class submarines were built to two very similar, but slightly divergent designs. The boats built at the Navy Yards used a detailed design prepared by Portsmouth. Boats built at EB and Manitowoc used the Portsmouth design as a base, with EB making numerous, but relatively minor, changes that facilitated production to their unique methods. Manitowoc was designated as a follow-on yard to EB and used the EB plans and part numbering scheme. One of the major differences was that the government boats used the Fairbanks-Morse engines while the EB design used the GM Wintons. There were slight internal and external differences as well, and these will be explained below.  

<div style="text-align: justify;"><span style="color:#000000">

===Wartime modifications===

[[File:Jack Mod 3.jpg|left|thumb|300px|<small>Jack (SS-259) displaying a typical Mod 3 fairwater configuration. Note that the 20mm mounts on Jack are later Mk 10 models. Dorado had earlier Mk 5 mounts</small>]]<div style="text-align: justify;"><span style="color:#00008B">The commencement of hostilities in December, 1941 came as a rude shock to the Submarine Service. It was quickly realized that our submarines, even though very well designed and built, had been optimized for peacetime cruising and not the vicious war that they found themselves in. Certain features included in the original design no longer made sense in the urgency of war, and in some cases they proved to be liabilities. Immediately an effort was commenced to remove "frivolous equipment" and put the boats into fighting trim. This was done in a series of modifications, or "Mods" that are described in detail [https://pigboats.com/images/3/3b/A_VISUAL_GUIDE_TO_THE_FLEET_SUBMARINES_PART_4_GATO_CLASS_2024.pdf '''in this article''']. We consider this to be an essential read.

Dorado, as completed, was configured as a Gato-class Mod 3, with the forward and after ends of the conning tower fairwater cut away, the periscope shears unplated, the port side anchor removed, an SJ radar installed forward of the shears, an SD radar installed aft of the shears, and 20 mm Mk 5 gun mounts installed on the forward and aft fairwater gun decks. The bridge remained at its original height. The 4"/50 caliber Mk 12 gun was mounted forward of the fairwater. Compare the photo of Jack at left with the photo of Growler above and the extent of the modifications becomes apparent. It was in this configuration that she departed Submarine Base New London on October 6, 1943, bound for the Panama Canal.

<div style="text-align: justify;"><span style="color:#000000">

==Class Construction==

<div style="text-align: justify;"><span style="color:#00008B">The sheer numbers of submarines that the Navy ordered nearly overwhelmed the existing production sources. As the war situation loomed large in the consciousness of the Navy in 1940 and 1941, the service expanded its sources for submarine construction. Up until then, there were three shipyards capable of handling the specialized and intricate process of submarine construction; two were government owned Navy Yards, and the third was the civilian [https://en.wikipedia.org/wiki/General_Dynamics_Electric_Boat '''Electric Boat Company'''] of Groton, CT. The [https://pigboats.com/index.php?title=Simon_Lake_non-Navy_Submarines '''Lake Torpedo Boat Company'''] of Bridgeport, CT had also built submarines for the USN, built due to several factors had gone out of business in 1924 and they never built any of the fleet submarines.

In 1919 the Navy designated the [https://en.wikipedia.org/wiki/Portsmouth_Naval_Shipyard '''Portsmouth Navy Yard'''] in Kittery, Maine as the lead design center for submarines. The Navy had changed the submarine acquisition paradigm with this move, as all previous submarines had been designed and built by civilian firms, with the Navy having little say in the detailed design process. Portsmouth also had four (later expanded to ten) building slips and facilities where the boats could be constructed and launched. To supplement Portsmouth, the [https://en.wikipedia.org/wiki/Mare_Island_Naval_Shipyard '''Mare Island Navy Yard'''] in Vallejo, CA (north of San Francisco) also built submarines, and prior to the start of Gato-class construction Mare Island had built six high quality submarines.

The Electric Boat Company (EB) had been a major player in submarine construction up to 1941. Indeed, they had built the Navy's first submarine, the [[Holland|'''USS Holland''']] in 1898 and had been very successful in designing and building submarines for the USN and some foreign navies up through 1925, acquiring a near monopoly. [https://pigboats.com/images/b/b9/The_Devil_in_the_Details_TSR_version.pdf '''For several reasons'''] EB had a falling out with the Navy in 1925, and for six years between the [[S-class|'''S-class''']] and the last of the V-class in 1931 EB did not build a single submarine for the USN. However, with fences mended, in 1931 EB was brought back into the submarine construction fold to build [[171|'''Cuttlefish (SS-171)''']] and were entirely successful. EB actually built half of the Porpoise, Salmon/Sargo, and Tambor/Gar submarines and by the start of the construction of the Gato-class in the fall of 1940 the yard had five building slips along the Thames River in Groton. By the spring of 1941 that had been expanded to 12.

However, even this expanded capacity across two government and one civilian yard was not going to be enough. In September of 1940 the Navy contracted with the [https://en.wikipedia.org/wiki/Manitowoc_Shipbuilding_Company '''Manitowoc Shipbuilding Company'''] in Wisconsin to build additional Gatos. Manitowoc eventually built 14 Gato-class boats to plans supplied by EB. The boats were launched sideways into the Manitowoc River, completed, and then run through their initial sea trials (including their first dives) in Lake Michigan. Once completed the boats were floated on a barge down the Illinois River to the Mississippi River, then put back into the water at New Orleans, where they were delivered to the Navy. Manitowoc had a fine reputation in the Submarine Service, with their boats being well built and rugged, despite their unconventional origin.

<div style="text-align: justify;"><span style="color:#000000">

===The Victory Yard===

[[File:Victory Yard EB Marked Up (2).jpg|left|thumb|300px|<small>View of the Victory Yard in Groton, CT showing construction progress on Dorado, late 1942.</small>]] <div style="text-align: justify;"><span style="color:#00008B">In the fall of 1941, the Navy noted with alarm that submarine construction capacity still did not meet demand, even with additional slipways at Portsmouth, Mare Island, Electric Boat, and Manitowoc. In the amended FY-41 appropriations, the Navy secured funds to purchase a disused shipyard downstream on the Thames River south of the main EB yard. The yard, formerly owned by the Groton Iron Works, had five slipways that had been used to build steel-hulled freighters in 1919 and 1920. Additional funds provided for renovations of the facility and additional land purchases on the southern edge of the existing yard. Once the purchase was completed on February 5, 1942 the Navy Department promptly turned over the facility to EB which immediately set to getting it up and running as an adjunct construction yard. Five more slipways were built. From that point until the end of the war the facility was operated in full by EB as an extension of the main yard upstream. It was called the "Victory Yard" by Electric Boat.

The first three boats laid down at the Victory Yard were the Dace (SS-247), Dorado (SS-248), and Flasher (SS-249) on ways 2, 3, and 4 in July, August, and September of 1942.<br><br><br>

<div style="text-align: justify;"><span style="color:#000000">

==USS Dorado (SS-248)==

===Specifications===

<center>
{| class="wikitable"
|+ 
|-
! Length (Ft-In) !! Beam (Ft-In) !! Surf. Displ. (Tons) !! Subm. Displ. (Tons) !! Surf. Prop. !! Surf. Shaft HP !! Aux. Power !! Subm. Prop. !! Battery/#Cells !! Subm. Shaft HP !! Surf. Speed (Kts) !! Subm. Speed (Kts) !! Surf. Range (NM@Kts) !! Subm. Endurance@Kts 
|-style="background-color:#FFFFF0"
| style="text-align:center;"| 311-9 || style="text-align:center;"|27-3 || style="text-align:center;"|2060 || style="text-align:center;"|2424 || 4x GM 16-248 (DE) || style="text-align:center;"|5400 || 1x GM 8-268A (DE) || 4x General Electric motors || 2x Exide VLA47B / 126 ea || style="text-align:center;"|2740 || style="text-align:center;"|20.25 || style="text-align:center;"|8.75 || style="text-align:center;"|11000@10 || style="text-align:center;"|48 hrs@2 
|-
|}
<center>
{| class="wikitable"
|+ 
|-
! Fuel Cap. (U.S. Gal) !! Patrol Endurance (days) !! Test Depth (Ft) !! Torp Tubes (B/S) !! Tube Dia. (In) !! Torp Load !! Deck Gun !! Secondary Guns !! Crew (O/E)
|-style="background-color:#FFFFF0"
| style="text-align:center;"| 116000 || style="text-align:center;"|75-85 || style="text-align:center;"|300 || style="text-align:center;"|6/4 || style="text-align:center;"|21 || style="text-align:center;"|[https://pigboats.com/index.php?title=Torpedoes '''24 Mk 14'''] || [https://pigboats.com/index.php?title=Submarine_Guns#Deck_Guns '''1x 4"/50 Mk 12'''] || [https://pigboats.com/index.php?title=Submarine_Guns#Automatic_Cannons '''2x 20mm Mk 5'''] '''&''' [https://pigboats.com/index.php?title=Submarine_Guns#Machine_Guns '''2x .50 cal M2'''] || style="text-align:center;"|7/70
|-
|}
</center></div>

<div style="text-align: justify;"><span style="color:#000000">

===Early Construction Phase===

<div style="text-align: justify;"><span style="color:#00008B">The keel of the submarine that would become the Dorado was laid on slipway #3 at the Victory Yard on August 27, 1942. The keel was quickly joined by hull sections that had been prefabricated in other areas of the yard. Prefabrication was an important part of shipbuilding during the war, and was a prime reason that the U.S. was able to out-build all other nations by an order of magnitude. Hundreds of workers toiled on the boat every day, 24 hours a day, seven days a week. EB made extensive use of women at the yard, and they made important contributions in every technical field.

Work on Dorado proceeded apace and nine months after her keel was laid she slid down building slip #3 and entered the water for the first time on May 23, 1943. At this point she was only about 70% complete, and much work remained before she could go to sea. She was caught by tugs in the middle of the Thames River and moved quickly to the fitting out pier at the Victory Yard, where the remainder of the work would be performed.

A portion of her crew had already arrived, including her commanding officer LCDR Earle Caffrey Schneider. Now that she was launched and at the fitting out pier, more of her crew would filter in nearly every day. Some were experienced and already qualified, and some were fresh from Submarine School just a few miles upriver. The crew worked side by side with the EB workers, learning about their boat as they went, and came to appreciate the hard work and dedication of the men and women who were building their boat.

By July she was essentially complete and was ready to go to sea for the first time.

<div style="text-align: justify;"><span style="color:#000000"> 

===Sea Trials===

<div style="text-align: justify;"><span style="color:#00008B">The first step is what is called "builder's trials". With only a portion of her crew onboard, the submarine makes her way down the Thames River and out into the Atlantic under the watchful guidance of Electric Boat personnel. The boat has not yet been accepted by the Navy, and it is the responsibility of the builder to make the initial tests, overseen by the crew and Navy personnel from the Supervisor of Shipbuilding's office in Groton. The intent is to test all systems to ensure that they work to specifications. Electric Boat personnel conduct the tests and take careful measurements of the boat's performance. Even the torpedo tubes are tested, with the boat firing non-operational torpedo "shapes". This ensured that all of the handling equipment, tube hydraulics, and pneumatic firing systems worked to specs.

During these builder's trials the submarine will make her first dive. It is not uncommon that the boat will encounter problems with buoyancy at this time, finding it hard to submerge or stay submerged as the EB personnel tinker with the ballast systems and the overall compensation calculations. There is one anecdotal report stating the boat actually grounded during an early submerged run due to a buoyancy problem. The initial dives are made in water much less than her test depth, so that if a problem occurs she will bottom before she reaches a critical depth. All of this is routine and correctable by the EB personnel and the ship's crew. There was another anecdotal report of a fire onboard during the builder's trials, but again this is actually to be expected as systems are given a full workout for the first time. The fire was likely electrical in nature and was quickly extinguished. Any serious damage would have delayed her commissioning, and there is no evidence of that occurring.

[[File:Seadragon at speed 19-N-20950.jpg|right|thumb|300px|<small><span style="color:#000000">Seadragon (SS-194) on a speed trial in Cape Cod Bay in 1939. High speed runs are an integral and required part of the builder's trials. Dorado completed hers successfully. Photo 19-N-20950 courtesy of NHHC.</small></span>]]Another aspect of the builder's trials is a speed run. This is to ensure that the engines and propulsion systems are working properly and that the submarine can make the contracted speeds, both surfaced and submerged. A measured mile course had been laid out in Block Island Sound, two buoys precisely laid in exact spots. The submarine would run a parallel course alongside the buoys at various speeds and her performance evaluated and logged. This was a very important criteria for the Navy's acceptance of the submarine.

At the end of the trials the Navy's Supervisor of Shipbuilding in Groton reviewed all the performance charts and reports written by Navy observers and EB personnel. He ensured that all discrepancies that turned up in the trials had been corrected by Electric Boat and the boat had met the required performance metrics. He signed off on the building contract, signifying that the U.S. Navy accepted the boat from the builder. On August 28, 1943 USS Dorado (SS-248) was officially commissioned into the U.S. Navy in a ceremony at Submarine Base New London, Groton, CT.

During the month of September LCDR Schneider and his crew took the boat out into the Atlantic as often as was possible, training themselves and conducting further tests on the systems. If any issues turned up, they could take the boat back to the EB facilities for further work. The last step was for the crew to pass a rigid series of evaluations by their squadron leadership, ensuring that they were trained sufficiently to take the submarine to war. This training and certification phase was completed by the first week of October, and during that week the boat was alongside at the base in Groton, taking on torpedoes, ammunition, fuel, and provisions. The last members of her crew reported aboard. LCDR Schneider received his operational orders and they specified that they get underway on October 6th and transit south through the Atlantic and the Caribbean to Submarine Base Coco Solo on the eastern side of the Panama Canal. This would be the first leg of her journey to the war zone in the Pacific.  

<center>[[File:RWB Starbar ver 3.jpg|300px]]</center>

<center>[[File:Subs bottom line 2.jpg]]
Page created by:<br>
<span style="color:#000089"><small>Thaddeus Weaver & David Johnston<br>
©2025 - Thaddeus Weaver & PigBoats.COM<br>
West Warwick, RI, Norfolk, VA<br>
[mailto:ussdoradoproject@gmail.com '''ussdoradoproject@gmail.com''']</small>
</span>
[[File:Subs bottom line 2.jpg]]</center>