Geometry and Hydrostatics
The LARC V (lighter amphibious resup-ply cargo) is a vehicle capable of being operated on both land and water. The amphibious lighter has an overall length of 35 feet, a maximum width over the fenders of 10 feet, and a maximum height to the top of the cab of 10.17 feet. The total net weight, dry, is 19,000 pounds, while the total gross weight is approximately 30,000 pounds. The cargo deck, which is capable of transporting a maximum payload of 10,000 pounds, is 16 feet long, 9.75 feet wide, and 2.42 feet deep. There is a loaded clearance of 2 feet between the hull and the ground. An overhead clearance of 10.33 feet is required for the transportation of the LARC V.
The vehicle is constructed with an aluminum frame supporting an aluminum hull, deck, and cab. The lighter is mounted on four rigidly supported wheels and the structure is designed to support the total craft weight on diagonally opposite pairs of wheels over the range of vertical accelerations that may be encountered. An aluminum canopy can be installed to cover the cab in case of inclement weather. The flush deck has a high center of gravity which facilitates the self-bailing feature.
The vessel requires a crew of two persons for its operation. The cargo deck is fitted with ten cargo tiedown hooks and four load centering devices. There are two headlights located at the front of the vehicle and one stern light. To provide access to the engine, the vehicle has two engine hatches, two muffler guards, four engine hatch handles, and one lifting frame. Two manual bilge pumps are incorporated for use if the three hydraulic bilge pumps fail. A marker buoy locates the light if it should sink in less than 100 feet of water. Four 18 x 25 tires with a 12-ply rating are used to support the vehicle. Pressures of 9 and 18 psig are recommended for the front tires for soft and hard terrain, respectively, while 14 and 22 psig are recommended for the rear tires on soft and hard terrain, respectively. Four dry-charged, 12-volt, 100-ampere-hour batteries are used. The two fuel tanks have a capacity of 72 gallons each.
The engine is an industrial gasoline engine of270 gross horsepower at 3,200 rpm of which 30 horsepower is consumed in the auxiliary equipment leaving 240 horsepower for propulsion. For water propulsion, a 30-inch-diameter, 30-inch pitch propeller is used which is located in a housing at the rear of the craft with a road clearance of 1.33 feet. The lighter is capable of traveling at a maximum speed of 30 mph on land and 10 mph in the water. The high range operating radius with no load on land is 250 miles and is 40 miles in water. For a full load, this operating radius is decreased to 200 miles on land but remains 40 miles in the water. Speed loss due to wave action is to be expected and is different only in degree between the amphibian and a vessel of similar dimensions. For the LARC V, speed losses compared to still-water speed at 225 propeller horsepower are 2 percent for 1.2-length wave, 16 percent for the 2-length wave, and 7 percent for the 4-length wave. The critical wave length for the LARC V is 200 feet.
The power steering system on the amphibious lighter will permit relatively easy steering. Basically, the steering on land is accomplished by full hydraulic power and in water by the rudder. The type of terrain (sand, mud, or hard roads) will affect land steering as with any automotive vehicle. Under ideal conditions such as hard smooth surfaces, the outside turning radius is 35.6 feet while the inside radius is 26.5 feet. The turning radius will increase as the terrain becomes softer. The lighter is capable of being steered if the hydraulic power should be lost but much more steering effort will be required; in water the steering wheel will turn the front wheels and the rudder at all times. Broaching in seas is possible. The operator must shift to wheel drive in following seas. The amphibious lighter is capable of going up extremely steep grades as high as 60 percent. The vehicles have an angle of approach of 31 degrees and an angle of departure of 28 degrees.
The aluminum amphibious lighter is used to carry cargo from an offshore supply ship to a beach for advanced base supply with a total cargo capacity of 10,000 pounds. It also serves as a dive boat or power supply for underwater work. It also can be used for moving personnel and equipment across both land and water from a base to a construction site.
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