USES OF PONTOON ASSEMBLIES

A barge is any of several pontoon string assemblies connected together to form a complete unit used for transporting cargo, including vehicles and personnel, and used primarily in their transfer from landing craft to amphibious vehicles or for lighterage duties in ship-to-shore movement of cargo. Barges, designed for lighterage operations, either self-propelled or towed, can be built in various sizes and, with modifications as required, can be used as a diving platform for salvage operations, as a tugboat, as a gate vessel, for fuel storage, or for mounting cranes.

The intended use of the barge determines the length of the strings, the number of strings needed, and the pontoon configuration of each string. Seven standard-size barges in the P-series equipment include

Figure 10-26.-Portable scaffolding used in assembly of structures on a pier.

the following: 3x7, 3x12, 4x7, 4x12, 5x12, 6x18, and 10x30 barges. The conventional pontoon barge, in sizes up to and including the 6x18 barge, is designed to carry its rated load with 1' of freeboard or a load concentrated at the center point that is heavy enough to bring the deck awash.

The 3x7 pontoon barge is a general-purpose structure that can be used as necessary in lighterage and ferrying operations. Cargo transport can be accomplished by tow, or the barge can be self-propelled by mounting a propulsion unit on the end without fenders. A 3x7 barge with a propulsion unit is shown in figure 10-27.

The 3x12 pontoon ramp barge is ordinarily used for transporting cargo and equipment and has proved suitable for general use in amphibious operation. The sloping bow end with ramps attached permits beaching the barge under its own power. And also it helps to unload tractors and equipment that will be used to assist in forming a causeway pier. Four 3x12 barges can be side-loaded on an LST for side-carry to the assault area, or the barges can be loaded in the well deck of an LSD or deck-loaded on an LST.

The 4x7 pontoon barge is similar in all respects to the 3x7 barge, except it is one string wider. Although this is a general-purpose barge used principally for lighterage operations, it is suitable for any transportation task within its capacity.

The 4x12 pontoon barge is a general-purpose structure that can be used in lighterage operations either by towing or as a self-propelled structure by the addition of propulsion.

The 5x12 pontoon barge is one string wider than the 4x12 barge but similar in all other respects. It is particularly suitable for mounting a crawler crane with a lifting capacity ranging from 20 tons at a 12' radius to 7 tons at 55'. This barge can also be used as a general-purpose structure and can be used in lighterage operations as a self-propelled structure by the addition of propulsion units.

The 6x18 pontoon barge is the second largest barge in the P-series pontoon system. Installation of propulsion units permits its use in lighterage operations for transporting loads (cargo, vehicles, and personnel) up to 250 tons. By the addition of accessories and equipment, the barge can be converted into a 1,500-barrel fuel storage barge (fig. 10-28). Also, by installing heavy-duty hinges, the barge can be converted into a wharf or used for outfitting and repair of smaller structures when placed on its deck.

The 10x30 pontoon barge is the largest barge in the pontoon system. It was developed primarily for mounting a 100-ton derrick (See fig. 10-29.) The barge, however, is adaptable to other uses. With propulsion units attached, it can serve as a lighterage barge in transporting over 800 tons of cargo at one time from ship to shore or dock. The barge can also be

Figure 10-27.-A 3x7 pontoon barge with a propulsion unit.

Figure 10-28.-A 1500 barrel , 6x18 fuel storage barge.

used as a pier or wharf or, by installing heavy hinges, could be connected to any existing pontoon wharf to enlarge or extend that structure.

Essentially, tugs are barges equipped with outboard propulsion units and the accessories required for the operations to be performed. The P-series equipment tugs are widely adaptable and can be used for towing, causeway tending, placing and retrieving

Figure 10-29.-100-ton derrick mounted on a 10 x 30 barge.

anchors, salvage operations, assisting in the installation and recovery of fuel systems, and other services.

The 3x14 warping tug shown in figure 10-30 is equipped with two outboard propulsion units. The after end of the center string incorporates an anchor housing to accommodate the 2,500-pound mooring anchor and also holds the anchor wire away from the propulsion screws. An A-frame, mounted on the bow of the tug, stands approximately 13' above the deck of the barge. A double-drum winch is mounted near the center of the barge. A line from the after drum is fairlead to the deck and back to the anchor astern, while the line from the forward drum is run over a sheave in the top of the A-frame and is used for lifting over the bow or pulling from the bow of the warping tug. The winch is mounted on a welded steel cross-braced frame. Standard equipment for the tug also includes M147 double bitts and navigation lights. The warping tug is approximately 90' long and 21' wide, has a stem draft of 48", a bow draft of 18", and a speed of 6 1/2 knots. The 3x14 warping tug replaces the 3x12 tug throughout the pontoon system. The only difference in these two is that the 3x14 tug is longer by two P1 pontoons and incorporates new style winches with lines feeding off horizontally laid drums.

A PONTOON CAUSEWAY consists of an inshore section, an offshore section, and as many intermediate sections as necessary to make up the desired length. Lengths up to 1 mile are considered possible. Each section is a 3x15 structure designed to support a load of 105 tons with a freeboard of 12".

Each string of the offshore (fig. 10-31) and inshore sections (fig. 10-32) is made up of 12 P1 pontoons with a P3 sloped deck pontoon and a P4 ramp-end pontoon at one end At the other end is an end-to-end connection pontoona-a P5F (female) end connection pontoon on the offshore section and a P5M (male) end connection pontoon on the inshore section. Strings of the intermediate sections (fig. 10-33) are made up of 13 P1 pontoons with a P5F at one end and a P5M at the other.

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