|Ford GPA 'Seep' (Sea Jeep)
|Body and chassis
||Amphibious military utility vehicle
||front-engine RWD / 4×4
||GAZ 46 (MAV)
||4-cyl. side valves,
134 cu.in (2,199 cc), 60 hp
||3-speed + 2-speed transfer case;
low range engages FWD;
PTO propellor drive
||84 inch / 213 cm
||182 inch / 462 cm
||64 inch / 163 cm
||69 inch / 175 cm;
45 inch reducible
(GWV 1,610 kg)
The Ford GPA (G=Government, P=80" wheelbase, A=Amphibious) 'Seep', was an amphibious version of the WWII Ford GPW Jeep. Unlike the jeep, the seep was not a successful design; it was considered too slow and heavy on land, and lacked sufficient seagoing abilities in open water. The design features of the much larger and more successful DUKW amphibious truck were used on the GPA.
History and development
Interior of a preserved GPA, 2010
After having commissioned Willys, Ford and Bantam to build the first 4,500 jeeps (1500 each) in March 1941, the US Motor Transport Board set up a project under the direction of the National Defense Research Committee (NDRC) to be designated "QMC-4 1/4 Ton Truck Light Amphibian".
Roderick Stephens Jr. of Sparkman & Stephens Inc. yacht designers was asked to design a shape for a 2,700-pound (1,200 kg) amphibious jeep, in the same vein as his design for the DUKW six-wheel-drive amphibious truck. Stephens' hull design looked like a miniature version of that of the DUKW, and just like it, the 'Seep' was going to have a screw propeller, driven by a power take-off, operating in a dedicated tunnel faired into the rear end bodywork, as well as a proper rudder.
The construction of the vehicle was developed in competition by Marmon-Herrington and Ford Motor Company. Marmon-Herrington specialized in all-wheel drive vehicles. The Marmon-Herrington prototype's hull formed an integral unibody structure, created by cutting shapes out of steel sheet and welding those together. The Ford entry, however, used a sturdy chassis and internal frame, to which more or less regular automobile type sheet-steel was welded. This construction made the GPA some 400 pounds (180 kg) lighter than its competitor. The GPA's design was based on the Willys MB and Ford GPW standard Jeeps as much as possible, using many of the same parts. The GPA had an interior similar to that of the MB/GPW jeeps, although the driver's compartment had almost twice as many control levers: 2WD/4WD, hi-range/lo-range, capstan winch (on the bows), propeller deployment and rudder control. After a direct comparison of the two company's prototypes, Ford received a contract for production starting in 1942.
Wartime Ford GPA trials in the Detroit area
In contrast to the DUKW, the GPA did not perform well in the field. At some 1,600 kg (3,520 lbs)[dubious – discuss] the production truck had become much heavier than the original 1,200 kg (2,640 lbs) specified in the design brief, but its volume had not been increased accordingly. As a consequence, a low freeboard in the water meant that the GPA could not handle more than a light chop or carry much cargo. The GPA's intended use of ferrying troops and cargo from ships off-shore, over a beach and continuing inland, was therefore very limited.
On land, the vehicle was too heavy and its body too unwieldy to be popular with the soldiers. GPAs would frequently get stuck in shallow waters, where the regular Willys MB's water fording abilities allowed it to drive straight through (Pohl, 1998). Production was already halted in March 1943 after production of only 12,778 vehicles due to financial quibbles between Ford and the US government, as well as bad reception of the vehicle in theatre. Although some sources (Pohl; Carlin, 1989) state that less than half of that number were ever completed, serial numbers of surviving specimens suggest that the 12,7XX figure is actually correct.
In spite of participating in the Sicily landings of September 1943, most GPAs were routed to the Soviet Union under the Lend-Lease programme. A small number of GPAs were used in action in North Africa and the Pacific.
The USSR developed a derivative of the GPA after the war. The GAZ 46 MAV, which closely resembled the GPA, entered production in 1952. The GAZ 46 was exported to many USSR-allied countries.
GPAs were also sold as surplus and were purchased by farmers, ranchers, adventurers and others. By the 1970s, collectors had discovered them, and started restoring them back to their original specifications. They appear at various military vehicle shows.
Half-Safe and other conversions
After World War II, several adventurers converted surplus GPAs into world-travelling machines.
The most famous one was during the 1950s when Australian Ben Carlin (1912–1981) sailed and drove a modified Seep, that he called "Half-Safe" on a journey around the world.
A young American couple, Helen and Frank Schreider, converted one which they called "La Tortuga" and traveled from Los Angeles to the Southern tip of South America (1954–56). They later converted another one called "Tortuga II" which they used on National Geographic expeditions in India (1959) and Indonesia (1961).
World War II British paratrooper veteran Lionel Force purchased a GPA from Levy's Surplus in Toronto, Ontario, Canada, and called it "The Amphib."  Among many changes, he grafted on a roof from a Dodge station wagon and lengthened the hull at the stern. He used the top halves of the doors, but knowing that he might be tied up alongside a dock, he added a round roof hatch. He planned to travel from Toronto to England via the USA, Mexico, Guatemala, Panama, South Armerica including Brazil, Africa, the Middle East, Greece and up to England. He got as far as Panama but turned back when he learned that the freighter upon which he intended to ship "The Amphib" from Brazil to Africa had been taken out of service.