Published on January 28, 2008
Slide1: ADAPTED FROM: Lesson 11a: Naval Shiphandling Slide2: Lesson 11a: Naval Shiphandling AGENDA: Describe the effects of momentum and inertia. Discuss “controllable” shiphandling forces. Discuss “uncontrollable” forces. Discuss “semi-controllable” forces.. Describe the pressure/suction effect on ship’s maneuverability during alongside operations and operating in shallow water. Applicable reading: WOG 89-114. Slide3: There may be more than a dozen forces acting about the vessel’s axis at a given moment, and the resultant may not be as anticipated but due partially to a force which has escaped discovery. This is not ‘mysticism’ as much as lack of the research which takes the art of shiphandling into the finite world of applied science. P.F. WILLERTON, BASIC SHIPHANDLING Shiphandling Theory MOMENTUM & INERTIA: MOMENTUM & INERTIA MOMENTUM: “Generally, we consider momentum as the motion of a ship at the time we no longer want it, especially when we have taken action to obtain the opposite effect. ... Momentum is the quality of motion measured by the product of mass & velocity.” INERTIA: Inertia is the quality of motion that causes a ship to resist a change in motion. “A force exerted on a ship will result in motion after inertia has been overcome.” Hooyer - Behavior and Handling of Ships Slide5: # of Screws # of Rudders Length/Beam Pivot Point Turn Diagrams Acceleration/ Deceleration Advance/ Transfer Navigational Draft PIVOT POINT: PIVOT POINT HEAD WAY, STEADY COURSE & SPEED AHEAD BELL FROM DIW... LONG STEERING LEVER FROM PROPS/RUDDERS ASTERN BELL FROM DIW... NO EFFECTIVE STEERING LEVER UNTIL SOME STERN WAY PIVOT POINT: PIVOT POINT PIER PIER PIER DIW - BOTH TUGS EQUAL LEVERAGE SLOW HEAD WAY- AFT TUG HAS MORE LEVERAGE SLOW STERN WAY - FWD TUG HAS MORE LEVERAGE SHIPHANDLING PRINCIPLES CONTROL vs. FAITH: SHIPHANDLING PRINCIPLES CONTROL vs. FAITH CONTROL: Precise and constant ability to adjust to changing circumstances. FAITH: Yielding control to natural forces Slide10: Three Basic Categories Of Forces Controllable Forces Semi-controllable Forces Uncontrollable Forces SHIPHANDLING FORCES CONTROLLABLE: SHIPHANDLING FORCES CONTROLLABLE ENGINES/PROPELLER(s) RUDDER BOW THRUSTER / APUs TUGS ANCHORS LINES PROPELLER FORCES STERN WALKS THE SAME DIRECTION PROPELLER TURNS: PROPELLER FORCES STERN WALKS THE SAME DIRECTION PROPELLER TURNS LONGITUDINAL THRUST TRANSVERSE THRUST (SIDE FORCE OR PADDLEWHEEL FORCE) COUPLE (TWIST) SINGLE PROPELLER STERN WALK: Visualize the lower blades walking along the bottom. Side Force SINGLE PROPELLER STERN WALK CONTROLLABLE PITCH PROPELLERS: CONTROLLABLE PITCH PROPELLERS STERN WALKS TO STBD FFG DD/CG/MCM DD/CG DEVELOP STERN WAY @ 0% PITCH AND WHEN TWISTING DDG 51 RUDDER EFFECTIVENESS: RUDDER EFFECTIVENESS RUDDER PLACEMENT COORDINATING RUDDER & ENGINES IMPLICATIONS OF ALL STOP PUMP TO THE RUDDER (KICK AHEAD) DDG-51 RUDDER PLACEMENT: DDG-51 RUDDER PLACEMENT BOW THRUSTERS / APUs: BOW THRUSTERS / APUs 270 090 BOW THRUSTER APU TWO UNITS EACH 360 DEG INDEPENDENT ON - OFF ONLY FFG LST/LHA/ARS/MCM Slide18: Tugboats Assist maneuvering by pushing or pulling. TO BE DISCUSSED NEXT LECTURE SHIPHANDLING FORCESSEMI-CONTROLLABLE: SHIPHANDLING FORCES SEMI-CONTROLLABLE SHALLOW WATER EFFECTS SQUAT BANK SUCTION / CUSHION INCREASED TACTICAL DIAMETER PASSING SHIP EFFECTS MEETING OVERTAKING/UNREPS Slide20: 2.5 X DRAFT SLOW DOWN TO REDUCE EFFECTS SHALLOW WATER EFFECTS SQUAT Slide21: SHALLOW WATER EFFECTS BANK SUCTION/CUSHION Slide22: PASSING SHIP EFFECTS MEETING/OVERTAKING SHIPHANDLING FORCES UNCONTROLLABLE: SHIPHANDLING FORCES UNCONTROLLABLE WIND CURRENT Slide24: Balance of Forces Wind (30 KTS) Current (3 KTS) Propeller (15 KTS) Mooring to a Pier: Mooring to a Pier 1. No set on or off the pier. a. Approach at 10 to 20 degrees, bare steerageway. b. Stop engines and drift closer. c. Put rudder over away from the pier. d. Back down as needed to stop forward motion. Mooring to a Pier: Mooring to a Pier 2. Being set on the pier. a. Bring the ship to a stop parallel to the pier, half a beam’s width away. b. Let current or wind push the ship in. c. Use engines to control position along the pier. Wind / Current Mooring to a Pier: Mooring to a Pier 3. Being set off the pier. a. Approach at faster speed. b. Put over lines as soon as possible, put rudder over away from pier to bring in the stern. c. Stop headway by backing outboard engine.