Shallow-Water Attack Boat (SWAB) - A "Distinguished Failure"

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Shallow-Water Attack Boat (SWAB)


Coastal vessel, tiny boat armed with some heavy weaponry: 14 recoilless rifles or 2 rocket pods.

A product of the (eccentric) Aviation Ordnance Department John Boyle who was “fascinated by small boats”. In 1963 Boyle started development of a low-cost attack boat with a high speed and powerful armament, which could be launched from landing ships to assault Soviet missile boats coming from port. In 1964, he presented his design to the Naval Ordnance Test Station at China Lake, and was given funding. The boat, called the Shallow-Water Attack Boat, or SWAB, was based on the hull of a Bertram 31ft sporting boat, and incorporated radar-absorbent material which gave it a tiny radar cross section, one of the first ships to be designed with this sort of material. Initially it was armed with 2 FFAR rocket pods, though testing showed that rocket dispersion was too great, and they were replaced with 2 recoilless rifle racks which had 7 57mm RRs each. Additionally there was a rear-mounted 20mm autocannon. The boat would be completed in 1965, and during early testing was found to have good seakeeping and high speed and manoeuvrability. The ship was then fitted with weaponry, and sent to the Boat Support Unit 1 for evaluation, however the weapon systems weighed down the ship enough that with a full crew and battle load it was unable to plane and only reached 22 knots. BSU-1 suggested fitting more powerful gas turbine or diesel engines to increase speed, and rearranging the armament to increase bridge visibility. Ultimately, the Navy wasn’t interested in the vessel, as its main priority for coastal craft was riverine ships for the Vietnam War, and the SWAB’s mission of attacking coastal missile boats was seen as rather suicidal as any small gunboat could easily dispatch it. The SWAB would then be disposed sometime after. Rather interestingly Egypt had a similar idea, where they fitted Bertram 31s with 4 122mm rocket launchers.


1x1 20mm M139

2x19 2.75" AERO-7 FFAR Rocket pod
2x1 Stabilized gun package

  • 1x7 57mm M18A1 Recoilless rifles
  • 1x1 12.7mm M2 (1000 rpg)

~8-10 tons standard?

Length: 9.3m

Beam: 3.4m

Draft: ~0.94m

Propulsion: 2 Chrysler petrol engines, 650 hp, driving 2 outdrives

Speed: 22-33 knots (41-61 km/h)

Range: unknown

Crew: 3-4

Raytheon 1900 navigation radar


Screenshot (326)
One of the similar Egyptian Bertram 31s

Cradle diagram of a Bertram 31ft

Friedman, N. (1987). Motor Gunboats and PTFs. In U.S. Small Combatants: Including PT-Boats, Subchasers, and the Brown-Water Navy: An Illustrated Design History (pp. 273, 276). Naval Institute Press.
Lawson, C. (2017). Fueling the Fire. In The Station Comes of Age: Satellites, Submarines, and Special Operations in the Final Years of the Naval Ordnance Test Station, 1959-1967 (pp. 275-278). NAWCWD.
Moore, J. (1976). Egypt. In Jane’s fighting ships 1975-76 (pp. 104). Janes. this Bertram Brochure


Looks super fun! +1

(Side note - you accidentally wrote 13.7mm instead of 12.7mm for the M2 machine gun. Might wanna fix that!)

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