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USS Portunus (ARC 1) on 22 August 1952.
Click on this photograph for links to larger images of this class.

Class: PORTUNUS (ARC 1)
Design: Navy LSM 1
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 31 May 1950 the Ship Characteristics Board promulgated the first preliminary characteristics for an LSM conversion for the SOFAR (Sound Fixing and Ranging) project, 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. Her 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 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 then transferred to Portugal under MDAP.

Ship Notes:
ARCNameMANotes
1PORTUNUSFY 1951. (ex-LSM 275, compl. 5 Oct 1944). Trf. Portugal 1959 as MEDUSA, became the submarine support ship SAN RAFAEL 1969, disposed of 1976.

Page Notes:
Compiled: 19 Oct 2021
© Stephen S. Roberts, 2021