SHIP

AREA RATIO, A R

Destroyer

100

Cruiser

160

Carrier

125

Cargo

240

Tanker

270

Submarine

125

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.

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