65ft Patrol Boat Mark III "Sea Spectre" (25mm Bushmaster Prototype) - Vision of the Future

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65ft Patrol Boat Mark 3 “Sea Spectre” with prototype 25mm Bushmaster mount

TL;DR:
Coastal vessel, asymmetrical patrol boat, this one has a funny (bad [actually I hear it’s decent]) 25mm Bushmaster.

Overview:
After the end of the Vietnam War, naval requirements for small craft changed drastically, and a new generation of patrol boats were developed by the Norfolk Division of the Naval Ship Engineering Center. The 65ft Patrol Boat Mark III was a successor to the Vietnam-era Swift boats and the unsuccessful CPIC patrol boat prototype. It was an asymmetrical vessel, with the bridge on the starboard side, while the port side had a superfiring platform that allowed for the installation of an autocannon, recoilless rifle, mortar, or twin torpedo tube. Additionally the hull was designed to have a small radar cross-section, though installing weaponry would render that feature useless. The ships had 3 engines, which made the interior space quite cramped, but allowed it greater survivability during engagements. The first Mark IIIs were ordered during Fiscal Year 1973, with 8 built at the Peterson Builders in Wisconsin, and were operated by the Navy SEALs. Additionally 18 more were ordered in FY 75 and 77. None of them had names, being known only by their hull number (65PBYYX, ie 65PB751). The ships in service were rarely fitted with the heavy weaponry it was designed for, making many design choices meant to accommodate them rather pointless. Though a few new small craft weapons were tested on the Mark IIIs, the 40mm Bofors in a new Mod.7 mounting which could be operated by a single person, which was widely adopted, the Norwegian Penguin anti ship missile, which was rejected for being too heavy, and a navalized 25mm Bushmaster, which in 1985 was adopted as a new standard small craft gun, though in the hand-operated and unstabilized Mk.88 mounting rather than the prototype stabilized mounting. The 25mm Bushmaster was tested on one of Special Boat Unit 12’s PB Mark IIIs. All the Mark IIIs would be discarded by 2000.

Specifications:

Armament:
1x1 25mm M242 Bushmaster in low-profile stabilized mount
1x1 20mm Mk.16
2x1 12.7mm M2

Displacement:
41.3 tons full

Length: 19.8m

Beam: 5.5m

Draft: 1.8m

Propulsion: 3 GM 8V-71TI diesel engines, 1800 hp, driving 3 shafts

Speed: 26 knots (48.2 km/h)

Range: 450nmi (at 26 knots)

Crew: 5

Systems:
LN66 navigation radar

Images:

image
What seems to be the prototype Mark III, with a pintle mount above the bridge


A group of Mark IIIs showing the variety of weapon options

A preserved Mark III
Drawings:
image
image
Damn that is pretty cramped

Sources:
Friedman, N. (1987). Post-Vietnam Small Combatants. In U.S. Small Combatants: Including PT-Boats, Subchasers, and the Brown-Water Navy: An Illustrated Design History (pp. 390–411). Naval Institute Press.
Gardiner, R., Chumbley, S., & Budzbon, P. (1995). USA. In Conway’s All the World’s Fighting Ships 1947-1995 (pp. 626). Naval Institute Press.
https://www.warboats.org/mk3.htm
https://www.warboats.org/SBU12.htm
https://navysealmuseum.pastperfectonline.com/photo/85F652DC-0C96-42DE-B869-271883460114

5 Likes

+1

cool vehicle bro +1

Could have it in multiple configurations, which is nice. +1