River Gunboats
Page 60
The monitors added the boat-shaped bow first introduced on the French monitors, plus the forward turret armed with a 40mm gun as supplied to the South Vietnamese Navy prior to American involvement. Later variants were armed with a powerful 105mm howitzer in a turret taken from the LVTH6 troop transport. Then came the ‘Zippo’ conversions, carrying two flamethrowers.
The LCM-6 as rebuilt into a Programme 4 monitor. Armed with four turrets and an 81mm mortar in the central well. Note the boat-shaped bow, the side extensions to the hull, and the minesweeping winch on the stern. (US Navy drawing)
Ten of the Programme 4 monitors carried a Mark 52 turret with 40mm Bofors and .50 cal Browning. A .30 cal Browning MG is on a pintle mount in the foreground. Note the brackets holding the bar armour screens away from the armour side plating of the hull, with the intervening space being filled with Styrofoam.
The 81mm Mk 2 Mod 0 mortar carried in the central well of the Programme 4 monitors. (Photo courtesy of John M. Carrico)
A view of the bar armour intended to provide protection against hollow-charge rocket warheads. In action, the crews had the habit of filling the intervening space between the upper bar panels and the superstructure with empty petrol cans, ration tins, ammunition boxes etc., which could reduce the effectiveness of the armour protection. (Photo courtesy of John M Carrico)
Eight of the Programme 5 monitors were armed with an M49 105mm howitzer with 151 rounds and co-axial .30 cal Browning MG with 2,000 rounds, mounted in a T172 turret taken from the LVTH6 amphibious troop carrier. Normally the turret would be enclosed in a cage of bar armour. Here the bar panels have not yet been fitted, allowing a better view of the turret. (Photo courtesy of John M. Carrico)
Six of the Programme 5 monitors, known as ‘Zippos’ after the cigarette lighter, were armed with two M10-8 flamethrowers in single M8 turrets located on either side of the bow. The M10-8 had a maximum range of 220 yards (200m) and an effective range of 160 yards (150m). Note the co-axial .30 cal Browning. (Photo courtesy of John M Carrico)
The ATC converted to a ‘Douche’ and renamed Irma la Douche after the 1963 film Irma la Douce starring Shirley Maclaine and Jack Lemmon. (Photo courtesy of John M Carrico)
All conversions from the LCM-6 were protected by armoured hull sides, outside of which were attached slabs of Styrofoam, finished off on the exterior by welded sheets of bar armour. The idea was to dissipate the jet from a hollow-charge warhead by having it first strike the bars. The foam and internal armour plate would then complete the work of preventing the jet of metal and warhead fragments from penetrating inside the hull or superstructure.
The American-built LCM-6 (Landing Craft Mechanised) used as the base for the various armoured riverine craft was a Second World War design derived from and 6ft longer than the LCM-3.
Launched:
Second World War by various manufacturers, converted from 1966.
Dimensions:
Displ: 64 tons full load; L: 18.59m/61ft (Programme 4), L: 18.44m/60ft 6in (Programme 5); B: 5.33m/17ft 6in; D: 1m/3ft 6in.
Crew:
11.
Power/Speed:
Twin screws; 2 × Detroit 64HK9 diesel engines, total 440bhp/8.5 knots (max), 6 knots (sustained).
Guns/Armour:
Programme 4: 1 × 40mm Bofors; 1 × 20mm cannon; 2 × .50 cal Browning HMG; 4 × 7.62mm MG; 1 × 81mm mortar; 2 × Mk 18 grenade launchers; 3 × M-79 grenade launchers/Plate and bar armour, total 10 tons. Programme 5: 2 × 20mm cannon; 2 × .50 cal Browning HMG; 1 × 7.62mm MG; 3 × M-79 grenade launchers; 1 × M49 105mm howitzer or 2 × M10-8 flamethrowers + 2 × Mk 19 grenade launchers.
Fate:
Survivors passed to South Vietnam.
ASPB (Assault Support Patrol Boat)
The first type of ASPB of Programme 4 had a well deck at the stern containing a Mount 52 combined 81mm mortar and .50 cal Browning. Due to a design error, the ASPB had been given inadequate freeboard and metacentric height, and could be easily swamped by the wake from other boats or even from its own wake if stopping rapidly or making sharp turns (when it had a tendency to lean outward). Two solutions were adopted, firstly the attachment of styrene foam sponsons to the stern, and secondly the deletion of the rear deck well.
Armament consisted of two Mk 48 turrets, each capable of mounting either a 20mm cannon or two .50 cal Brownings. The suppressed Mount 52 mortar and MG in the plated-over well deck was replaced by two .30 cal Brownings on shielded pintle mounts on the rear deck.
Later type ASPB without the rear well and Mount 52. (Photo courtesy of John M Carrico)
Designed for maximum firepower coupled with a high level of protection, the ASPB became known as the ‘destroyer’ of the riverine force.
The armour protection consisted of a ¼in (6.35mm) aluminium trigger plate positioned 22in from the 5⁄8in main armour plate (double that distance from the coxwain’s position). It was discovered that the internal hardened armour was too brittle, and additional fragment suppression protection had to be added to the interior.
The ASPB’s maximum speed of 16 knots was useful, but in fact most operations were restricted to the much lower speed of the monitor or command boat.
A total of thirty-six Programme 4 and 50 Programme 5 boats were ordered; of the latter, fourteen were delivered direct to South Vietnam.
Launched:
First in May 1967, by Gunderson Brothers Engineering Corporation, Portland, Oregon.
Dimensions:
Displ: 34.3 tons; L: 15.28m/50ft 1½in; B: 4.64m/15ft 2½in; D: 1.3m/4ft 3in.
Crew:
5 + assault team of 6–8.
Power/Speed:
Twin screws; 2 × GM 12V71 diesel engines, total 430bhp/16 knots.
Guns/Armour:
2 turrets, either Mk 48-0 turret with 1 × 20mm cannon + 40mm grenade launcher or Mk 48-1/2 Turret with 2 × .50 cal Browning HMG or 2 × 7.62mm MG + 40mm grenade launcher/16mm face-hardened armour plate with fragment suppression backing; + 6.35mm aluminium trigger plate spaced away from armour.
Fate:
Survivors passed to S. Vietnam.
Sikorsky Prototype ASPB
In the search for higher speed, but more importantly heavier firepower to outrange the Viet Cong’s recoilless rifles and RPGs, Sikorsky proposed an ASPB prototype which was ordered in June 1968. To give sufficient speed, the aluminium boat was propelled by three gas turbines driving waterjets, which gave exceptional manoeuvring capabilities. For the first time, an ASPB was to be fitted with stand-off bar armour as on the monitors, but spaced well away from the basic superstructure armour. Armament was a large turret mounting a 105mm howitzer and two 20mm cannon, plus a Mk 48 turret forward, as fitted to the production ASPBs.
The Sikorsky prototype performed and was well received, and was delivered to the US Navy in 1969. It was never deployed in combat in Vietnam, but was used to train Special Forces up until 1980.
Launched:
Late 1969 by Sikorsky Aircraft.
Dimensions:
Displ: 33.3 tons; L: 15.1m/49ft 8in; B: 6m/19ft 8in; D: 1.04m/3ft 5in.
Crew:
5?
Power/Speed:
Triple waterjets; 3 × United Aircraft (Canada) ST-6570 565shp gas turbines/Up to 50 knots (per manufacturer).
Guns/Armour:
Central turret: 1 × 105mm M102 howitzer + 2 × 20mm cannon; Bow turret: Mk 48-1/2 turret with 2 × .50 cal Browning HMG or 2 × 7.62mm MG + 40mm grenade launcher/Face-hardened armour plate with fragment suppression backing + stand-off bar armour.
Fate:
Stricken 25 August 1980.
PBR (Patrol Boat River)
The PBR was the most numerous of the combat boats in Vietnam, and perhaps the best known due to movie portrayals. The RPC (see SOUTH VIETNAM) having been deemed a failure, a search was begun for a small, manoeuvrable river patrol boat. After testing a prototype produced by Willis Slane of Hatteras Yacht Co. in early 1965, a contract for the first 120 boats was awarded to United Boatbuilders of Belling
ham, Washington. They produced a military version of their standard 31ft Uniflite, using waterjets. The glassfibre hull offered many advantages: it was rot-free, it was strong enough to allow beaching, it resisted mine shock damage, and RPG hits often did not trigger the warhead.
The Sikorsky ASPB Mark II at speed. Note the howitzer main turret and the bar armour. (Photo Igor I. Sikorsky Historical Archives, Inc © 2017)
The first boats were armed with a twin .50 cal turret forward and a single .50 cal aft. Plus an M60 MG and a 60mm mortar amidships. Vertical armour plate was fitted. To avoid RPG war-heads hitting the radome and sending fragments into the conning position, a ballistic net similar to that used on command boats was later fitted.
The early promise of high speed was illusory: the first Jacuzzi water jets wore out rapidly, and their water inlets became easily clogged with weeds. In 1968, an examination of a series of PBR Mark Is revealed a top speed of 19.5 knots for the best and a low of 14.6 knots for the worst. In addition, the fibreglass hulls tended to absorb water.
General arrangement drawing of the Sikorsky ASPB Mk II prototype. (Drawing Igor I. Sikorsky Historical Archives, Inc © 2017)
Interesting shot of PBR Mk I No 110 of RivDiv 531, with vertical armour plates fitted for the M60 gunner behind the wheelhouse. (Photo by Cecil H. Martin on Website https://archive.hnsa.org/ships/pbrmkii-e.htm)
The glassfibre hull of the PBR offered many advantages.
With its popularity assured, the total requirement for both Marks of PBR was raised to 250 boats. The problems were remedied in the Mark II, with a revised hull form, slightly reduced profile, improved Jacuzzi waterjets, and more powerful engines. 27.5 knots could now be achieved fully loaded
The following specifications are for the PBR Mk II. Details for the Mk I are similar, with lower-powered engines and a maximum speed of 22 knots.
Launched:
From 1965 by United Boatbuilders, later renamed Uniflite, of Bellingham.
Dimensions:
Displ: 6.8 tons light, 8.1 tons full load; L: 9.75m/32ft; B: 3.56m/11ft 8in; D: 0.76m/2ft 6in.
Crew:
4–5.
Power/Speed:
Twin waterjets; 2 × GM 6V53N diesel engines, total 216bhp/25+ knots.
Guns/Armour:
1 × twin .50 cal Browning HMG forward; (on some boats, 1 × 20mm cannon replaced one of the .50 cal); 1 × .50 cal Browning HMG or Mk 18 grenade launcher aft; 2 × 7.62mm M60 MG/Bulletproof vertical plates on early models.
HSSC (Heavy SEAL Support Craft)
Two LCM-6 landing craft were modified into Heavy SEAL Support Craft (HSSC): the bow ramp was cut down and armoured, a splinter armour deck was built over the rear two-thirds of the well, which was stressed to accept a medivac helicopter, armour was added to the sides and conning tower, and an extremely heavy armament was fitted. The aim was to be able to go in and extract a SEAL unit even under heavy fire. The engine room was soundproofed, and the exhaust led underwater. In spite of its impressive specifications, the HSSC was disliked by SEAL units, firstly because of its bulk and lack of stealth, but primarily because of its painful lack of speed.
A third prototype was begun but never completed for the US Navy. It was presumably completed as part of the ten-vessel HSSC order for South Vietnam.
Launched:
2 × Second World War LCM-6 modified 1967.
Dimensions:
Displ: 75 tons; L: 17m/56ft; B: 5.33m/17ft 6in; D: 1.07m/3ft 6in.
Crew:
8.
Power/Speed:
Twin screws; 2 × GM 6-71 diesel engines, total 348bhp/8.5 knots.
Guns/Armour:
HSSC # 1 (Nha Be): 1 × 106mm Model M-40Ai recoilless rifle; 1 × 81mm mortar Mk 2 Mod 0; 5 × .50 cal Browning HMG; 1 × 7.62mm Minigun; 1 × M60 7.62mm MG. HSSC # 2 (Nam Can): 1 × 106mm Model M-40Ai recoilless rifle; 1 × 81mm mortar + .50 cal Mk 2 Mod 1; 5 × .50 cal Browning HMG; 1 × 7.62mm Minigun; 4 × M60 7.62mm MG/Bow door armoured; Splinter armour deck; hull sides and conning tower armoured.
Fate:
1971: One lost in combat, second sank under tow.
MSSC (Medium SEAL Support Craft)
Ten glassfibre MSSCs were ordered from Atlantic Research in December 1968, and they entered service the following year. With an inverted-V hull design, they were fast, well-protected and popular.
Launched:
1969 by Atlantic Research.
Dimensions:
Displ: 17 tons; L: 11.05m/36ft 3in; B: 3.58m/11ft 9in; D: 1.01m/3ft 4in.
Crew:
5 + 13 SEALs.
Power/Speed:
Twin Mercruiser stern drives; 2 × 325bhp Chevrolet 427 petrol engines/30 knots.
Guns/Armour:
3 × .50 cal Browning HMG or2 × .50 cal Brownings + 1 × 7.62mm Minigun; 1 × 60mm Mortar Mk 4 Mod 0; 4 × 7.62mm M60 MG.
The MSSC showing the boarding net which usually replaced the fragile front steps. (Photo from Website http://brownwaternavy.com/vietnam/photos2/MSSCLong_Phu.jpg)
LSSC (Light SEAL Support Craft)
The initial order for sixteen was fulfilled by Grafton. The large radome cover was a hazard, as it made an excellent target, and a hit by an RPG would send splinters down into the cockpit. Grafton also built twenty-two of a slightly longer version, with outboard motors, as the larger of the two types of STAB (SEAL Team Assault Boat).
The LSSC was a small, lightweight, shallow-draught craft for insertion of SEAL teams.
An LSCC coming alongside, showing its small size and what appears to be five machine guns, a .50 cal up front, a pair of 7.62mm M60s at the rear of the cockpit and two single M60s mounted on either side.
Launched:
1968 by Grafton Boatworks.
Dimensions:
Displ: 5 tons; L: 7.3m/24ft; B: 2.9m/9ft 6in; D: 0.46m/1ft 6in.
Crew:
3 + 6 SEALs.
Power/Speed:
Two Jacuzzi waterjets; 2 × Ford 427 petrol engines total 350bhp/30+ knots.
Guns/Armour:
Various, up to 5 MG, including 0.50 cal Browning, 7.62mm Minigun, 7.62mm M60, 5.53mm Stoner MG; plus Mk 19 grenade launcher/Complete boat armoured to resist .30 cal rounds at 100 yards (91m) and over.
MODERN RIVER GUNBOATS
Mk III Sea Specter photographed in 1983. Note the offset cabin and heavy armament. The folded-up platform at the stern is for frogmen. (Photo by Giorgio Arra)
PB Mark III.
PB Mk III Sea Specter
Derived from commercial craft used as support vessels for offshore drilling platforms in the Gulf of Mexico, the PB Mk III was designed as a multi-mission inshore craft to replace the Vietnam-era LSSC, MSSC and HSSC types. They have a longitudinally-framed aluminium hull. Depending on the mission, various weapon fits were available. As with the British ‘Fairmile B’ MLs of the Second World War, the PB Mk III came pre-fitted with bolt-down positions on the deck for the range of armament. Several were used by SEAL teams.
Launched:
1975 to 1986 by Marinette Marine, Wisconsin, and Peterson Builders, Sturgeon Bay, Wisconsin.
Dimensions:
Displ: 36.8 tons; L: 19.8m/64ft 10¾in; B: 2.44m/8ft 0¾in; D: 1.68m/5ft 6in.
Crew:
5.
Power/Speed:
Triple screws; 3 × Detroit 8V71T 650bhp diesel engines/26 knots.
Guns/Armour:
Various can be fitted, including: 40mm Bofors; 81mm and 60mm mortars; 40mm Mk 19 grenade launchers; 20mm cannon; .50 cal Browning HMG; 7.62mm Minigun; 7.62mm M60 MG; Missiles.
Fate:
In service.
Cyclone class vessels in formation, seen here prior to the latest modifications. (Photo US Navy)
[[Illustration 88 Photo:]] The latest Mk 38 Mod 2 25mm Bushmaster cannon. (Photo US Navy)
Cyclone Class PB
The fourteen vessels of the Cyclone class coastal patrol boats include in their mission portfolio the support of US Navy SEAL teams in shallow-water environments, thus justifying the
ir inclusion here. The class have gone through recent weapons-fit modifications, and the rear deck has been altered, the crane being replaced by a 9ft (2.7m) hull extension and stern notch, providing a launch/recovery ramp for SEAL craft.
Launched:
1994 to 2000 by Bollinger Shipyards.
Dimensions:
Displ: 341 tons (Tornado 387 tons); L: 51.825m/170ft (Tornado 55m/180ft 5in; B: 7.6m/24ft 11in; D: 2.3m/7ft 7in.
Crew:
39 including 9 SEALs.
Power/Speed:
Four screws; 4 × Paxman 3,350bhp diesel engines/35 knots.
Guns/Armour:
2 × 25mm Mk 38 Mod 2 Bushmaster chain gun; Various armament fits, including: 40mm Mk 19 grenade launchers; Twin 0.50 cal Browning HMG; 7.62mm M240 MG; Stinger surface-to-air missiles; Griffon surface-to-surface missiles. Tornado has stealth capability from revised shape.
Fate:
In service.
Riverine Command Boat (RCB) (CB90)
Developed from the Swedish CB90 designed by Dockstavarvet to carry a half platoon of infantry, the RCB has entered service with US forces. As its designation implies, it is intended for ‘tactical mobility and fire support in opposed riverine and littoral environments’. Its waterjets are partially ducted and can move like the diving planes of a submarine, thus endowing the CB90 design with excellent manoeuvrability. Fully air portable, it can be fitted with a range of armaments to suit the particular operational requirement. For a plan drawing, see SWEDEN.