View source for Engineering:Assault Support Patrol Boat

{|{{Infobox ship begin
| infobox caption = Assault Support Patrol Boat
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|Ship image=File:Assault Patrol Boat (ASPB) in Vietnam c1968.jpg
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|Ship caption=ASPB in South Vietnam c.1968
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{{Infobox ship class overview
|Name=ASPB (Assault Support Patrol Boat)
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|Operators=*{{Navy|US}}
*{{flagicon|South Vietnam}} Republic of Vietnam Navy
*{{flagicon|Khmer Republic}} Khmer National Navy
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|Total ships completed= 86
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{{Infobox ship characteristics
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|Ship type=Riverine [[Engineering:Patrol boat|patrol boat]]
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|Ship length=*{{convert|50|ft|m|abbr=on}}
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|Ship propulsion=2 × 430hp [[Engineering:Detroit Diesel Series 71|General Motors 12V71]] diesel engines
|Ship speed= 14.8 knots
|Ship range={{convert|130|nmi}}
|Ship complement=5
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|Ship armament=*two Mk 48 turrets with either [[Engineering:Colt Mk 12 cannon|20 mm cannon]] or [[Engineering:M2 Browning|.50 cal machine guns]]
*two single [[Engineering:M60 machine gun|M60 machine gun]]s or [[Engineering:M1919 Browning machine gun|Mk 21 machine guns]]
*one Mk 2 Mod 0/1 .50 cal machine gun/81mm mortar
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The '''Assault Support Patrol Boat (ASPB)''' (also known as the '''Alpha Boat'''), was a heavily armed and armored riverine patrol boat developed by the United States Navy for use in the Vietnam War from late 1967.

==History==
[[File:80-G-K-42552.jpg|thumb|right|ASPB on patrol during Operation Coronado IX, November 1967]]
The ASPB was approximately {{convert|50|ft}} long, its hull was constructed of {{convert|7/32|in}} steel, from the gunwale {{convert|2|in}} up it was {{convert|1/8|in}} steel, its superstructure was {{convert|1/4|in}} aluminum which provided protection against 57mm recoilless rifle rounds and armor-piercing bullets up to .50 caliber in size.<ref name=Rottman>{{cite book|last=Rottman|first=Gordon|title=Vietnam Riverine Craft 1962–75|publisher=Osprey Publishing|year=2012|url=https://books.google.com/books?id=d9Cl0apC1gUC&pg=PA11|isbn=9781782000600|page=11}}{{Dead link|date=August 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name=Sherwood>{{cite book|last=Sherwood|first=John|title=War in the Shallows: U.S. Navy and Coastal and Riverine Warfare in Vietnam 1965-8|publisher=Naval History and Heritage Command|year=2015|isbn=9780945274773|url=https://www.history.navy.mil/research/publications/publications-by-subject/war-in-the-shallows.html}}{{PD-notice}}</ref>{{rp|180}} The first 36 boats were ordered from Gunderson Brothers Engineering Corporation of Portland, Oregon on 25 October 1966.<ref>{{cite web|url=https://www.history.navy.mil/content/history/nhhc/our-collections/photography/numerical-list-of-images/nhhc-series/nh-series/NH-95000/NH-95973.html|title=NH 95973 50-foot assault support patrol boat (ASPB)|publisher=Naval History and Heritage Command|date=17 August 1967|accessdate=2 May 2020}}</ref> The initial boats were armed with two Mk 48 turrets with either [[Engineering:Colt Mk 12 cannon|20 mm cannon]] or [[Engineering:M2 Browning|.50 cal machine guns]], two single [[Engineering:M60 machine gun|M60 machine gun]]s or [[Engineering:M1919 Browning machine gun|Mk 21 machine guns]] and one Mk 2 Mod 0/1 .50 cal machine gun/81mm mortar in a well in the aft of the boat, but this well was eliminated in later models.<ref>{{cite web|last=Wells II|first=William R.|title=The United States Coast Guard's Piggyback 81mm Mortar/.50 cal. machine gun|publisher=Vietnam Magazine|date=August 1997|url=http://www.pcf45.com/misfire/81-50.html|access-date=16 January 2012}}</ref><ref>{{cite web|url=http://www.pcf45.com/misfire/mortar.html|title=Notes on Mk 2 Mod 0 and Mod 1 .50 Caliber MG/81mm Mortar|author=Bob Stoner}}</ref> The boat had a complement of five crewmen and could carry up to eight soldiers. The boat was powered by two 430&nbsp;hp [[Engineering:Detroit Diesel Series 71|General Motors 12V71]] diesel engines giving a top speed of 14.8 knots and it expelled its exhaust directly into the water reducing noise and smoke emissions, making it the quietest river patrol craft. The boat carried some 650 gallons of diesel fuel, allowing an operational range of {{convert|130|nmi}} at 10 knots.<ref name=Rottman/><ref name=Sherwood/>{{rp|180–1}}

The first ASPBs arrived at Vung Tau, South Vietnam on 20 September 1967 and were offloaded on 22 September. The ASPBs were to act as escorts and provide protection for the slower Armored Troop Carriers (ATCs) of the Mobile Riverine Force during the troop transport phase of riverine assaults. Due to their steel construction and armor, the boats would also perform minesweeping in advance of river assault squadrons and serve as a blocking and interception force in the waterways around the area of operation.<ref name=September1967>{{cite web|url=https://www.history.navy.mil/research/archives/digitized-collections/commander-naval-forces-vietnam/monthly-summaries-1967.html|title=US Naval Forces Vietnam Monthly Historical Supplement September 1967|publisher=Department of the Navy|date=2 January 1968|accessdate=2 May 2020}}{{PD-notice}}</ref>{{rp|56}} The ASPBs first saw action on 28 September 1967 during Operation Coronado V when they were used as minesweepers for an assault on An Dinh village, the "birthplace" of the Viet Cong.<ref name=September1967/>{{rp|54–5}}

On 21 December 1967, ASPB 111-4 hit a 75-pound mine {{convert|2|mi}} northwest of Đồng Tâm Base Camp. Although the mine detonated right against the ASPB, the charge failed to puncture the hull, and the ASPB was able to return to base on its own power with only moderate damage.<ref name=Sherwood/>{{rp|182}}

These boats were followed by another fifty craft ordered on 24 January 1968, however within months of their deployment, the boats began revealing some shortcomings. Between February and March 1968 four ASPBs sank due to noncombat reasons. In one event, on 2 March two passing ASPBs swamped ASPB 91–1, causing the boat to sink in less than a minute and drowning a sailor who became trapped in a berthing compartment. A Navy investigation of all four sinkings concluded that the primary faults were the lack of seaworthiness caused by inadequate compartmentalization and marginal buoyancy, coupled with excessive weight and a low freeboard. As a quick fix, Naval Forces Vietnam tried to improve the ASPB's seaworthiness by removing engine-compartment
armor to reduce top weight. The armor also never lived up to its promise. Engineers had difficulty developing a hard, lightweight armor that was not brittle. On the first generation boats, a 75mm recoilless rifle round aimed at the cockpit could break off an entire piece of armor and propel it through the cockpit. By late 1969 most ASPBs were being used only for minesweeping and base security duties.<ref name=Sherwood/>{{rp|181}}

===Mark II prototypes===
[[File:NH 95977.jpg|thumb|right|Stewart Seacraft ASPB Mark II prototype trials, 1969]]
Stewart Seacraft built an ASPB Mark II prototype at Berwick, Louisiana.<ref>{{cite web|url= https://www.history.navy.mil/content/history/nhhc/our-collections/photography/numerical-list-of-images/nhhc-series/nh-series/NH-95000/NH-95845.html|title=NH 95845 Assault support patrol boat (ASPB), Mark II.|publisher=Naval History and Heritage Command|accessdate=2 May 2020}}</ref> The Stewart Mark II had three gun turrets and a mortar well in the extreme bow  and bar armor around midships superstructure.<ref>{{cite web|url=https://www.history.navy.mil/content/history/nhhc/our-collections/photography/numerical-list-of-images/nhhc-series/nh-series/NH-95000/NH-95981.html |title=NH 95981 Assault support patrol boat (ASPB), Mark II|publisher=Naval History and Heritage Command|accessdate=2 May 2020}}</ref> 
[[File:Assault support patrol boat (ASPB), Mark II.jpg|thumb|right|Sikorsky Aircraft ASPB Mark II prototype, c. 1969]]
Sikorsky Aircraft also built a Mark II prototype mounting a 105mm gun and two 20mm cannons in a central turret.<ref>{{cite web|url=https://www.history.navy.mil/content/history/nhhc/our-collections/photography/numerical-list-of-images/nhhc-series/nh-series/NH-95000/NH-95842.html|title=NH 95842 Assault support patrol boat (ASPB), Mark II.|publisher=Naval History and Heritage Command|accessdate=2 May 2020}}</ref> The prototype was delivered to the Navy at the end of 1969. It was powered by three Pratt & Whitney PT-6 engines connected to three [[Engineering:Pump-jet|water-jet pumps]] giving a maximum speed of {{convert|50|mph}}. The prototype was never adopted into service but remained in use with special forces until 1980.<ref>{{cite web|url=https://www.sikorskyarchives.com/Gunboat.php|title=Gunboat|publisher=Sikorsky Archives|accessdate=2 May 2020}}</ref>

==Operators==
*{{flag|United States}} &ndash; U.S. Navy
*{{flag|South Vietnam}} &ndash; Republic of Vietnam Navy
*{{flag|Khmer Republic}} &ndash; Khmer National Navy

==See also==
* List of patrol vessels of the United States Navy

==References==
{{reflist}}

[[Category:Military boats]]
[[Category:Patrol boat classes]]

{{Sourceattribution|Assault Support Patrol Boat}}