3 October 2005
Table 4-7. AR for Major Vessel Groups
AREA RATIO, A R
Note that in these and all other engineering calculations discussed in this
UFC, the user must be careful to keep units consistent.
EXAMPLE: Find the longitudinal current force with a bow-on current of θc=180 degrees
with a current speed of 1.544 m/sec (3 knots) on a destroyer in salt water with the
characteristics shown in Table 4-8.
SOLUTION: Table 4-9 shows the predicted current forces. Note that these forces are
negative, since the bow-on current is in a negative "X" direction. For this destroyer, the
force on the propeller is approximately two-thirds of the total longitudinal current force.
For commercial ships, with relatively smaller propellers, form and friction drag produce a
larger percentage of the current force.