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USS Portunus (ARC 1) on 22 August 1952.

USS Portunus (ARC 1) on 22 August 1952.
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Class: PORTUNUS (ARC 1, ex LSM)
Design: SCB Project No. 55, conversion of Navy LSM 1 type
Displacement (tons): 700 light, 1,220 full
Dimensions (feet): 204' oa, 197' wl x 35' e, 34' wl x 11' max nav
Armament: 2-20mmS
Accommodations: 9 officers, 60 enlisted
Speed (kts.): 13
Propulsion (HP): 3,600
Machinery: Diesel (direct), 2 screws

Construction:
ARCNameReclasBuilderKeelLaunchComm
1PORTUNUS4 Dec 1950Federal, Newark1 Aug 194411 Sep 19442 Jul 1952

Disposition:
ARCNameTDecommStrikeDisposalFateMA Sale
1PORTUNUS30 Apr 19591 May 19591 Nov 1959Trf--

Class Notes:
On 4 February 1949 CNO recommended including in the FY 1950 shipbuilding and conversion program one cablelaying conversion of an LSM for the SOFAR (SOund Fixing And Ranging) project. Scientists had discovered in 1944 that low frequency sound could travel long distances in a sound channel called the SOFAR channel in the deep ocean, and the Navy soon realized that this phenomenon could be used to increase the range at which submarines could be detected. (The SOFAR project was superseded in the early 1950s by the SOSUS or SOund SUrveillance System program which used similar natural phenomena and involved the deployment of arrays of hydrophones on the ocean bottom connected by underwater cables to processing centers located on shore.) By 21 April 1949 the SOFAR ship had been moved to the FY 1951 program. On 31 May 1950 the Ship Characteristics Board promulgated the first preliminary characteristics for this conversion, Shipbuilding Project No. 55. (For an earlier participant in SOFAR see NASHAWENA, YAG 35.) According to these preliminary characteristics the ship's mission was to support facilities utilizing submarine cable, including SOFAR and harbor defense installations. The ship's primary task was to install, repair, and replace ocean bottom hydrophones and associated cable at depths up to about 600 fathoms, and her secondary task was to install, repair, and replace underwater cables and hydrophones associated with harbor defense equipment and other special underwater devices. Her existing Fairbanks-Morse diesel engines were to be fitted with a modified hydraulic coupling or other device permitting continuous operation at all speeds from 1 knot to maximum sustained speed. The interior (vehicle well) was also to be decked over, the bow welded shut, and the pilot house placed on the centerline. Cable handling machinery and cable tanks would have to be installed. She was to have two 20mm single mounts for mine disposal purposes. On 4 December 1950 the Navy established the new classification ARC for cable repairing or laying ships. At the same time, in view of the selection of LSM 275 for conversion to a cable repairing or laying ship, her designation was changed to ARC 1.

USS ARC 1 was commissioned at Mare Island on 2 Jul 1952 and the name PORTUNUS was approved for her a year later on 13 July 1953. She operated off California ports until departing on 1 June 1953 for the U.S. East Coast. Based at the New York Naval Shipyard, Brooklyn, she laid cable off Cape May, New Jersey, off Bermuda, in the approaches to New York, and off Sandy Hook, New Jersey. From 1955 to 1959 she continued to lay cable, off Key West, off Sandy Hook, off Bermuda, off Wood Island, Maine, off Nantucket Island, in the Narragansett area, and off Little Creek, Virginia. She periodically picked up new cable at Newington, New Hampshire. She was replaced by YAMACRAW (ARC 5) in 1959 and was then transferred to Portugal under MDAP.

Ship Notes:
ARCNameMANotes
1PORTUNUSFY 1951. (ex-LSM 275, comm 6 Oct 1944). Trf. Portugal 1959 as MEDUSA, received with engines in bad condition and inactive after arrival at Lisbon on 15 Dec 1959. Used for diver training in the cable wells and as an accommodation ship at the Alfeite Naval Base. Renamed SAN RAFAEL 27 Dec 1965 and classed as a submarine support ship. Out of service 2 Feb 1972, struck 7 Jan 1976, with only 395 underway hours between 1959 and 1976.

Page Notes:
Compiled: 19 Oct 2021
© Stephen S. Roberts, 2021
Special sources: RG 19, Confidential General Correspondence 1949, Box 127 File C-FS/A1-3; barcoavista.blogspot.com/2010/08/navio-de-apoio-medusa.html; oceanservice.noaa.gov/facts/sofar