PONTOON ATTACHMENTS

Pontoon attachments, used in the basic assembly of pontoon structures, include assembly angles, bolts, nuts, keepers, assembly plates, and closures.

Structural steel ASSEMBLY ANGLES in varying lengths are used to connect the P-series pontoons into stings. Each is suitable for assembling a definite number of pontoons and designated as E-series angles. The angles are positioned to each of the four edges of a row of pontoons. Various types of assembly angles

Figure 10-6.-All E516 assembly angle.

are available. Figure 10-6 shows an ES 16 assembly angle. Figure 10-7 shows assembly angles E 16L and E 26L.

Angles are supplied in several lengths, so strings can be made up with a minimum number of welded joints, and they are designed so these welds fall midway along the edges of each pontoon, rather than between pontoons where stress is greatest. Each angle has one or two cross-sectional sizes, 6" x 6" x 1/2" thick or 8" x 8" x 1/2" thick. Angles with 8" legs are used to replace 6 x6 's at the center of strings 18 to 24 pontoons long, and strings of 30 pontoons have 8" angles throughout to resist the extra stress that their weight imposes. Regardless of dimensions, however, each P-series angle falls into one of two types: basic or end-condition angles. Basic angles are those angles used throughout the body of a structure. Their application is not restricted to top, bottom, left, or right

Figure 10-7.-Assembly angles E 16L and E 26L.

angles of the strings. On the other hand, end-condition angles connect P2, P3, or P4 pontoons to the ends of strings, and each is designed for a specific orientation-top or bottom and right or left. Basic angles can be shortened or lengthened to make up modified configurations, and end-condition angles can be cut and formed from basic angles to meet abnormal operating requirements.

The A6B ASSEMBLY BOLT is a 1 1/2" diameter x 3 3/8" long, hexagonal head, steel bolt (fig. 10-8). Three radial grooves on the head, spaced 120 degrees apart, are the code for grade 5 steel rated at a tensile strength of 105,000 psi. In addition to its use in securing assembly angles to pontoons ate each comer, the A6B bolt is also used to connect strings into structures, to secure deck fittings and accessories, and to pin hinges on dry dock stabilizer towers.

The forged FNI FLANGED NUT (fig. 10-9) is designed to fit into a pontoon pocket with sufficient clearance to allow positioning on the A6B assembly bolt. The flange of the nut is large enough to prevent the nut from turning in the pocket when the bolt is tightened; it is formed near the midline of the nut to clear welds in the pocket and allow positive se sting of the nut boss when the A6B bult. is tight.

Figure 10-9.-All FNl flanged nut.

The KPI KEEPER PLATE (fig. 10-10) is made from a plate 3 3/4" long, 2 1/8" wide, and 3/16" thick. The plate is cut out to fit over four of the hexagonal flats on the A6B bolt head. After final tightening of a bolt in a pontoon structure, the keeper plate is positioned around the bolt head and skip-welded to the underlying assembly plate or angle. This prevents the bolt from working loose during operations. To reduce maintenance problems, you should use the keeper plate on the bottom of pontoon structures where daily inspection is impractical. Keeper plates should not be welded to the bolt head.

Steel PLATES of various shapes are used in the assembly of pontoon structures mostly to reinforce those areas that are subjected to maximum stress and shear. A number of different types of assembly plates are shown in figure 10-11. Each of the plates shown is designed for a specific application, as indicated below.

API CONNECTING PLATE: The AP1 is a steel plate with four drilled holes for A6B assembly bolts. It reinforces the A6B bolts that hold pontoon strings to each other in completed structures that use either 6" or 8" angles.

AP3 LAUNCHING ANGLE PLATE: When pontoon structures are to be side-loaded on an LST, an accessory known as an LA1 launching angle is attached. The AP3 is a steel plate that is used to attach the LA1 to the structure. The AP3 has four drilled holes for A6B bolts, and a curved plate is attached to form a semicylindrical pad. The pad serves as a fender to protect the hull of the LST on which the pontoon structure is side-loaded.

Figure 10-10.-A KPl keeper plate being installed on an A611 bolt.

Figure 10-11.-Assembly plates.

NOTE: As of this printing LSTs are being decommissioned and it is undecided what platform will transport causeways. The information on LSTs is given because the Reserve Fleet will retain two and the next platform used could require the same hardware for loading and launching.

AP4A TIE PLATE: The AP4A is a steel plate with two drilled holes for A6B bolts. It is used for connecting pontoon strings to each other at their bow and stem ends. If necessary, an acceptable substitute for the AP4A can be obtained by cutting an API connecting plate in half across the narrower dimension; two plates are produced, both of which can be used.

LA2 LAUNCHING ANGLE END PLATE: The LA1 launching angle used when side-loading a pontoon structure on an LST is attached to the structure at the bow and stem ends with a two-hole assembly plate, just as pontoon strings are connecteed within the structure by the two-holed AP4A at the bow and stem. The two drilled holes in the LA2 are for A6B bolts. Two half-ovals are welded perpendicularly to the upper face of the plate, on either side of the bolt holes. These half+oval lugs serve as fenders to protect the hull of the LST in the same way as the pad on the AP3.

AP5 END PLATE: The AP5 is a steel plate that is welded across the gap between pontoons at the bow and stem of adjacent strings. It is used only in certain special cases where structures require extra reinforcement; for example, where end connectors are used or where the structure will be side-launched. An

Figure 10-12.-Typical fender installations.

acceptable substitute for the AP5 can be field-fabricated, if necessary, from an API. To do so, remove the holes from the API by cutting 3" inside the two edges measuring 18 1/4", and halve the resulting 18 1/4" x 5" plate to produce two 9 1/8" x 5" plates; both can be used as end plates.

AP6 CHAFING PLATE: The AP6 is a steel plate. 10" square, with two opposite edges beveled. Welded to the sides of causeway sections, the AP6 protects the causeway from damage due to sliding contact. It is frequently used between side-lapped causeway sections. Because the AP6 is a nonstock item, it should be fabricated in the field when it is required. Dimensions are not critical; halves of an API or an AP7 plate will serve as chafing plates when properly beveled.

AP7 GUSSET PLATE: The AP7 is a steel plate cut in the form of a 9" high trapezoid. The parallel edges are 18" and 12" long, and the 18" edge has a 1/4" bevel. The AP7 reinforces the end-condition angles used at the fore and aft ends of larger structures. The 18" edge is positioned against a tip or bottom assembly angle so the plate bridges the gap between the pontoons to which the angle is bolted. The 18" edge is welded to the angle, and the two vertical edges are welded to the adjacent pontoons. API connecting plates can also be used for reinforcing, welded to end-condition angles in the same way as the AP7.

AP8 RAMP-END BENT PLATE: The AP8 is fabricated from steel plate. An 11" x 20 1/4" rectangle is bent to form two legs, one 8 5/8" and the other 11 5/8" long; each leg has two drilled holes for A6B bolts. The AP8 is used for connecting pontoon strings at the point where each string has a P3 sloped-deck ramp pontoon connected to a P1 pontoon.

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