TM 5-1940-321-13&P
a. Grab Lines. The grab lines are made of black 14 mm polyester rope and are approximately
5/8- inch in diameter. The primary purpose of the grab lines is to provide safety for the passengers inside
and swimmers outside of the craft. They are woven to hang loosely in a draped configuration, which
provides sufficient slack to serve as an easily grasped handhold. The grommets, made of stainless steel,
secure the grab lines to the lacing cuff and provide sufficient base strength to distribute the pulling force.
A lower grab line is woven through the lower D-rings for three purposes: to serve as a line for securing
equipment, as an additional grab and safety line should personnel become trapped under the craft during
capsizing, and as an aide for righting the craft from a capsized position.
b. Lacing Cuff. In addition to providing attachment points for the grab lines, the lacing cuff
functions to enhance structural rigidity and craft shape. A non-stretch webbing reinforcement is contained
inside the lacing cuff. During construction, it is stretched to a specified amount of tension, then glued to
the top of the buoyancy tubes. After the flue becomes firmly bonded, the tension is released, fiving the
craft a "bow up" shape. This shape allows the bow to life more rapidly to oncoming waves, which reduces
the possibility of swamping. Additionally, this shape results in a drier craft since it reduces the amount of
the spray and water entering the craft.
c. Equipment Tie-down Rings. The equipment tie-die rings (D-rings) are of two sizes. The
rings are bonded into a base patch that distributes the loads resulting from their use. The tie-down rings
are bonded with reinforcing patches to the upper and lower parts of the main buoyancy tubes at
convenient locations throughout the interior of the craft. The tie-down rings are used to safely secure
mission equipment and cargo in locations that will provide correct weight distribution and craft trim. D53
and d300 rings are bar tacked using aeronantical/parachute type of assembly method by stitching.
d. Intercommunicating Valves. (Figure 3-3). Each craft has four intercommunicating valves
located on the main buoyancy tubes. They are used for controlling inflation and deflation of the five
internal air chambers and for releasing excessive pressure. When used correctly, crewmembers can
easily and quickly control and equalize the air distribution and pressure in the tubes. Intercommunicating
valves are so named because of their purpose, which is to allow air to flow into all five air chambers
through a single valve and then to isolate the five chambers from each other so that if one chamber is
punctured, the other four chambers remain pressurized. Isolation is achieved by pointing the arrow
shaped indicator on the I/C valve flywheel downward or at the 6 o clock position.
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