TM 55-607/NAVSEA OP 3221 Rev 2
Figure 6-3. Static forces due to roll motion.
In shiploading, dynamic loads (forces) result mainly from the accelerations and decelerations
of the roll, pitch,
and yaw motions of a ship. The effects of such forces are indicated in figure 6-4. Dynamic forces are analogous to those
experienced in an elevator and are most noticeable when the ship recovers from a roll; that is, changes roll direction.
The change in roll direction obviously occurs at the point of maximum roll angle. As noted previously, the cross-deck
component of the item's weight also exerts its maximum force on the dunnage structure at this point. Therefore, the total
maximum force that is applied to the dunnaging structure is equal to the sum of the static and dynamic forces at the
maximum roll angle. Both static and dynamic loads increase with roll angle; the dynamic forces also increase as the
period (duration) of the roll becomes shorter for a given roll angle. Dynamic loads are more severe for "stiff" ships; that
is, ships that demonstrate snap-roll recovery characteristics.