b. Figure 8-23 shows the subsequent stowage of the next adjoining row of unit loads. To ensure tight stowage, it is
essential that the unit load be positioned to bear both on the strip sheathing and tightly against the initial unit load. The
only dunnage required for the bottom tiers at this point is the strip sheathing, which is spaced the widths of the unit loads
and reinforced where required. Subsequently, each succeeding row can then be stowed athwartships tightly against the
preceding row. Based on the assumption that the stowage extends to the opposite side of the hold, the dunnaging at the
sweatboards should be identical to that just described. It is important to note that since tight stowage extends from the
sides of the ship toward the center, no more than one central void should occur per row. The overstowed unit loads
comprising the elevated tiers are subject to the same conditions as the lower, but lateral displacement from the unit loads
in the lower tier is caused by the vertical angle of the hull. Obviously, as the vertical hull angle approaches the
perpendicular, as it does in certain holds, the displacement of the unit loads between tiers will be reduced. When this
displacement reaches zero, the cargo is essentially block stowed, with only small, randomly spaced voids occurring
within the stow. These are shored with either full-block structures or void tables.
c. Pairs of 1-by 6-inch boards are placed between tiers along the entire row. A 2 by 4-inch cleat is fastened to the
strip sheathing at a level even with the top of the unit load to provide a solid bearing surface for the tier stripping, and this
is the foundation for the unit loads comprising the next tier. The tier stripping is nailed to the cleats. Tier stripping ill
certain cases need not extend the full length of the row. For example, if the unit loads are rectangular and present a
uniform bearing surface to adjacent loads, then tier stripping is needed only to span from the aforementioned cleats
across the top of the end load. In holds where the hull angle is more nearly perpendicular, tier stripping is not required.
d. Figure 8-24 illustrates the tight stowage that can be obtained by using the one-point technique of unit-load
positioning at the sweatboards. The bulkheads constructed across the fore and aft ends of the stowage prevent cargo
movement in these directions. While it may appear that lateral forces could cause movement of unit loads at the strip
sheathing, closer examination reveals that this is not the case. Any forces athwartships are blocked at the bearing points
of the loads at the sweatboards. The bearing points essentially are reduced to pivot points, which restrict load movement
to a rotational rather than a straight-line movement. Rotational movement is blocked by the adjoining loads and the
bulkheads. Therefore, the effectiveness of this stowage is dependent upon the following:
(1)
Dunnaging at the ship's sweatboards.
(2)
Dunnaging at the fore and aft ends of the stowage.
(3)
Stowing the cargo so that bearing surfaces between unit loads are maximum.
(4)
Effective shoring of all voids between unit loads to prevent athwartship movement.
8-25
