Sailed4seas的部落格

WE CAN DERIVE SOME BASIC CONCEPT FROM THE FACTS ABOVE.

THE RUDDER AREA IS A CONSTANT. SO, WE HAVE FOUR VARIANTS REGARDING THE TURNING MOMENTUM: RUDDER ANGLE, VESSEL SPEED, ENGINE SPEED AND RUDDER DISTANCE TO PP.

FOR EXAMPLE: ONE VESSEL MAY PROCEED IN DEAD SLOW AHEAD (5 Kts). BUT, THE PROPELLER MAY MAKE A FULL SPEED (12 Kts). THE WATER SPEED WORKING ON RUDDER PLATE IS SOMEWHERE NEARING 12 Kts. IF WE CHANGE THE ENGINE ORDER TO HALF AHEAD(10 Kts), THE WATER SPEED WORKING ON THE RUDDER IS NEARING 10 Kts. IF WE STOP THE ENGINE( 0 Kts), THE WATER SPEED WORKING ON THE RUDDER PLATE IS NEARING 5 Kts, DUE TO THE VESSEL SPEED. THE SQUARE OF 12 IS 144 AND THE SQUARE OF 5 IS 25. ONE VESSEL HAS 5 KTS SPEED WITH ENGINE IN FULL AHEAD(12 Kts) CAN HAS ALMOST 5 TIMES OF RUDDER FORCE THAN OTHER VESSEL HAS 5 KTS SPEED WITH STOPPED ENGINE(0 Kts). FOR MORE RUDDER EFFECT, WE NEED HIGHER ENGINE SPEED.

• THE INTIAL VESSEL SPEED CAN HAVE DECISIVE INFLUENCE ON THE CONSEQUENCE OF TURNING. THE INITIAL SPEED CAN DECIDE TWO FACTORS IN THE TURNING. THE FIRST IS THE AVAILABLE TIME INTERVAL FROM WOP(WHEEL OVER POSITION) TO THE TURNING POINT. THE LONGER TIME INTERVAL CAN GIVE THE NAVIGATOR MORE TIME TO OBSERVE THE VESSEL’S REPONSE TO THE MANEUVERING WHICH CAN RELEASE THE STRESS LEVEL TO AVOID ANY NEGLIANCE. THE SECOND IS HOW MANY ENGINE SPEED RESERVED FOR THE MANEUVERING THEREAFTER.
• THE VESSEL CAN MAKE MORE EASY TURNING WITH SLOWER VESSEL SPEED (Vs) WITH SAME RUDDER ANGLE. FOR THE PP IS MOVING MORE FAR AWAY FROM THE RUDDER WHEN VESSEL GOING SLOWER WHICH MAKE THE DISTANCE TO THE PP LONGER. THE LONGER PP DISTANCE CAN ALSO REDUCE THE TURNING DIAMETER IN THE SHIP’S TRACK. HOWEVER, THE DIFFERNCE BETWEEN FULL SPEED AND DEAD SLOW SPEED IS ONLY 1/8 SHIP’S LENGTH.
• THE TIME INTERVAL WE USED FOR TURNING IS CLOSED RELATED TO THE WHEEL OVER POSITION(THE SHIP POSITION BEFORE THE TURNING POINT WHICH WE PUT THE RUDDER TO THE REQUIRED AUDDER ANGLE) IN OUR VOYAGE PLANNING. IF THE WOP IS WELL BEFORE THE TURNING POINT, THE NEEDED TURNING MOMENTUM IS RELATIVE SMALLER WITH LONGER TIME AVAILABLE FOR TURNING.. IF THE WOP IS TOO CLOSE TO THE TURNING POINT, THE NEEDED TURNING MOMENTUM SHOULD BE MORE THAN THE ONE WE USED IN AN EARLIER WOP TO SPEED UP THE TURN.
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IN THE SHIP HANDLING, THE WOP WE PLANNED USUALLY IS A FIXED DISTANCE. THUS, THE INITIAL VESSEL APPROACHING SPEED WILL DETERMINE THE AVAILABLE TIME INTERVAL FOR TURNING.

• CONTROLLING THE VESSEL FINAL SPEED IS ALSO AN IMPORTANT CONCERN OF SHIP HANDLING. WHEN CONDUCTING A TURN IN THE WATERWAY OR HARBOUR AREA, IF WE BARELY MAKING THE TURN AND HAVE PLACED THE VESSEL IN THE CORRECT POSITION WITH ALL THE AVAILABLE MEANS WE HAVE INCLUDING THE MAXIMUM ENGINE SPEED AND FULL RUDDER, THE TURNIING MAY STILL BE A DIASASTER DUE TO EXCESSIVE VESSEL SPEED AFTER TURNING.. THIS MAY SPOIL THE APPROACHING SPEED TO A BERTH OR LEAVE TOO SHORT TIME INTERVAL TO DEAL WITH NEXT TURN.
• THE ENGINE SPEED RESERVED MEANS THE RESERVED ENGINE REVOLUTION FOR INCREASING OR REDUCING THE TURNING MOMENTUM. THIS USUALLY IS THE LAST RESOLVE IN OUR MANEUVERING. FOR INCREASING THE ENGINE SPEED WILL CAUSE THE UNWANTED EXCESSIVE SPEED WHICH MAY HAVE VERY COMPLICATED INTERACTION WITH THE HARBOUR INFRASTRUCTURES, LIKE BANK SUCTION, BANK CUSION, INBALANCE PRESSURE FIELD DUE TO WATERWAY BOTTOM…. 
• IT IS PREFERRED TO USE THE RUDDER ANGLE FIRST TO INCREASE THE TURNING MOMENTUM THAN INCREASE THE ENGINE REVOLUTION IN HARBOUR AREA. THE RUDDER ANGLE IS EASILY RECTIFIED AT ANY MOMENT. THE ENGINE SPEED WILL LINGER WITH THE VESSEL SPEED. THE ENGINE SPEED CAN BE ADJUSTED WHININ SECONDS, BUT THE VESSEL SPEED WILL LAST MINUTES MORE. WHAT WE NEEDED IN SHIPHADLING IS HIGH ENGINE SPEED TO GIVE THE MAXIMUM TURNING MOMENTUM AND LOW VESSEL SPEED TO HAVE LONGER DISTANCE FROM RUDDER TO PP.
• TO HAVE THESE TWO EFFECT AT THE SAME TIME, WE WOULD USE THE MANEUVERING CALL KICK-AHEAD WHICH CONSIST OF FULL RUDDER ANGLE AND ENGINE SPEED IN A VERY SHORT INTERVAL. THE CORRECT SEETING FOR KICK AHEAD SHOULD PUT THE FULL RUDDER IN THE NECESSARY DIRECTION FIRST THEN KICK THE ENGINE. THE FULL RUDDER CAN GIVE THE MOST OF EFFECTIVE RUDDER AREA WHICH CAN ALSO SERVE AS PART OF BRAKE TO THE ENGINE EXPELLED CURRENT. THE FULL RUDDER ALSO HELP REDUCE THE VESSEL SPEED,  .  
• THE SLOW INITIAL AND FINAL SPEED IS A GOOD INDICATION OF THE SUCCESSFUL MANEUVERING.