Manuevering Characteristics and Interaction Flashcards
What factors are associated with interaction?
Speed, depth of water, proximity of obstructions, the hull form and the maneuvering aids operational to the vessel
What are ship performance factors?
Corrosion, hull growth, hull damage, engine maintenance.
How can interaction be observed?
As squat, a bank cushion affect, or an unexpected movement between two vessels in close proximity.
What information should be found in the ship’s “pilot card” or “maneuvering booklet”?
Ship’s general particulars, main maneuvering equipment characteristics, hull particulars, maneuvering characteristics in deep and shallow water, main engine operating characteristics, wind forces and drift effects.
What info should be included in the “ship general particulars” section of the Pilot Card?
Vessel name, year of build, distinctive identifications numbers, GT, deadweight, load line displacement, the principle dimensions; LOA, molded breath and depth, load line draft, FWA, air draft.
What info should be included in the “Maneuvering Equipment and Equipment Characteristics” section of the Pilot Card?
M/E type and # of units, combined power output; the # and type of propellers and propeller diameter, pitch and direction of rotation; the type and # of rudders and location.
What info should be included in the “Shallow Water Maneuvering Characteristics” section of the Pilot Card?
Curves should be drawn showing maximum squat values with different speeds and blockage factors with the ship at various drafts.
What info should be included in the “Deep Water Maneuvering Characteristics” section of the Pilot Card?
Graphs from turning circle test showing advance and transfer; times and speeds at 90 deg., 180 deg., 270 deg., 360 deg.; acceleration and speed characteristics, and stopping capabilities and distances from various speeds and conditions.
What happens to the pivot point when making a turn?
The resultant turning motion on the vessel sees the pivot point following the arc of the turn.
What happens to the pivot point when at anchor?
The pivot point goes to the bow-effectively the hawse pipe.
What causes speed loss during hard over round turns? How much speed loss is typical?
The rudder angle imposed causes considerable drag along with hydrodynamic forces. 30-40% loss in speed is typical.
How will a list on a vessel affect a hard over round turn?
The completion time of the round turn will be extended. Also, turning towards the list will generate a larger turning circle than turning away from the list.
Does the type of rudder influence the turning circle?
Yes, a flap-type rudder compared to a traditional semi-balanced rudder will generate a tighter turning circle.
How does the shape and design of the rudder affect the size of the turning circle?
Rudders with a large surface area will reduce the size of the turning circle along with having a small clearance between the rudder and the hull.
Does cargo distribution affect handling characteristics?
Yes-cargo placed around the mid-ships section sections of the vessel vs. cargo placed a the extremities of the vessel will improve handling and responsiveness to the helm.
What are some effects of rudder angle on turning circles?
Employing a large rudder angle will lead to tighter turning circles but will lead to greater loss of speed.
In most cases what area of the vessel describes the perimeter of the turning circle?
The pivot point.
What are some negative aspects of propeller cavitation?
Propeller cavitation creates a vortex at the blade tips leading to speed loss. This action can lead to pitting of the propeller will lead to further inefficiencies of the propeller and further loss of speed.
What are common types of propellers?
Right-hand fixed pitch, CPP, contra-rotating, multi-blade, twin, triple, and quadruple propeller sets, pod propulsion units, kort nozzle systems, and Azi-pod systems.
What are some advantages of controllable pitch propellers?
If a blade is damaged they can be replaced one blade at a time; the constant rotating shaft allows for shaft generator; immediate response to amount and direction of power from the wheelhouse.
What is real slip?
Occurs as the result of physical conditions between the propeller and the water in which it is immersed. It should only be positive.
What is apparent slip?
Concerned with facts of real slip and additionally the effects of wind or current–can be positive or negative.
How do you determine engine speed?
Pitch in feet times RPM times 60 divided by 6076 feet.
How do you determine slip?
% slip = Engine speed minus ship’s speed divided by engine speed. Will be positive if engine speed is greater the ship’s speed.
