USCG Exam PracticeSingle-screw maneuvering and prop walk
A single-screw vessel is being maneuvered at low speed in calm water. The coxswain alternates short bursts ahead with the rudder over against short bursts astern. What is the purpose of this technique?
- A. To maintain sternway while using the discharge current to improve rudder response during the astern phase
- ✓ To substitute for the twin-screw twist by combining rudder force, discharge current, and propeller side force in sequenceCorrect
- C. To use asymmetric thrust from the two power strokes to rotate the vessel about its pivot point with minimal advance
- D. To reduce propeller side force by alternating the direction of shaft rotation and equalizing blade thrust
Why B is correct
The compound maneuver on a single-screw vessel substitutes for the twin-screw twist by combining rudder position, short bursts of thrust ahead and astern, and the propeller's own side force in sequence. Ahead with the rudder over, the discharge current moves the stern strongly; astern, side force dominates.