NAVYPEDIA

Ships

No	Name	Yard No	Builder	Laid down	Launched	Comm	Fate
MSO519	Ability		Peterson Builders, Sturgeon Bay	3.1956	29.12.1956	8.1958	stricken 2.1971
MSO520	Alacrity		Peterson Builders, Sturgeon Bay	3.1956	8.6.1957	10.1958	auxiliary 6.1973
MSO521	Assurance		Peterson Builders, Sturgeon Bay	1.1957	31.8.1957	11.1958	auxiliary 3.1973

Technical data

Displacement standard, t	792
Displacement full, t	934
Length, m	55.5 wl 57.9 oa
Breadth, m	10.7
Draught, m	3.00
No of shafts	2
Machinery	2 General Motors diesels
Power, h. p.	2700
Max speed, kts	14.5
Fuel, t	diesel oil
Endurance, nm(kts)	2400(12)
Armament	1 x 1 - 40/60 Mk 3, 2 x 1 - 12.7/90, A Mk 2, A Mk 4, A Mk 6 acoustic, M Mk 5, M Mk 6, M Mk 7 magnetic and Oropesa No.1 wire minesweeping gear
Electronic equipment	SPS-53 radar, UQS-1 sonar
Complement	83

Project history

Although minesweeper design continued after 1945, and although the prototype new ocean sweeper was authorised under the FY50 programme, construction on a large scale did not begin until the Korean War, with ten units under the FY51 first supplemental budget, eighteen under the second, and fifteen under die third, another five being planned under the FY52 programme. The new sweeper was somewhat smaller than the 180ft Second World War type, and it was built of plywood for minimum magnetic signature. Two XMAP pressure sweeping caissons could be towed. Given problems in diesel engine procurement under what were then expected to be mobilisation conditions, designs were prepared for either a new Packard light-weight engine or for an existing GM commercial type. Reportedly the rapid development of the Packard (which was also used in the new coastal sweepers) and its aircraft-type design led to many mechanical problems, which were not corrected for as much as eight years after us introduction. Given its unfortunate reputation, the Packard never saw large-scale commercial service, and the Navy suffered again as production ended and spares were largely unavailable. Of ninety-three ships to the SCB-45A or Agile class design, fifty-eight were retained by the US Navy, the others being transferred.

The Acme (MSO508) and Ability (MSO519) classes were improved and slightly enlarged Agiles built under the FY54 and 55 programme, the latter designed as mine division flagships. Ultimately both series were fitted as flagships.

All of the new ocean sweepers were built of wood with bronze and stainless (non-magnetic) steel fittings, with automatic degaussing, to compensate for course changes, as well as electrical insulators in internal piping, lifelines, and stays. All also had a new mine-locating sonar, UQS-1, later replaced by SQQ-14, a variable-depth unit on a rigid retractable rod.

Modernizations

None.

Naval service

No significant events.