Ship Manoeuvering Principles and Pilotage Flashcards
The speed at which you can safely go astern on the engines is generally?
5 kts on a fully laden ship
What rules of thumb should you use to judge speed?
1 knot = approx. 100 FT per minute or 30 Meters per minute (0.017 NM per minute when using a VRM)
When going astern and the ships head does not swing in the direction you expect due to the transverse thrust, this could be caused by the follow?
Wind effects or tidal stream effects.
How can you create maximum transverse thrust effect?
By using Full ahead or Full astern, to create confused water around the propeller
How can one minimize transverse thrust effect?
Build engine speed slowly by stages, so as to build up water through the propeller, so that it can gain maximum grip of the water
How much rudder is generally used to counter the transverse thrust effects?
Generally pretty negligible, only will need 1 or 2 degrees to counter its effect.
If there is not enough room to turn a ship round in one single maneuver, then the ship will have to be turned__________.
Short Round
Which direction should a right handed propeller ship be turned to when turning short round?
Starboard
Which direction should a left handed propeller ship be turned to when turning short round?
Port
Where will the center of turn be positioned when the ship is on an even keel
approximately midships
Where will the center of turn be positioned when the ship is down by the stern?
move further aft
Where will the center of turn be positioned when the ship is down by the head?
Move further forward
Do thrusters if fitted affect the center of turn?
NO
Do the rudder and propeller effect the center of turn?
Only if there is a change in ships speed
Will weight on a mooring line or anchor chain, alter the position of the center of turn?
Yes
Do tugs pushing and pulling alter the position of the center of turn?
Yes
When the portion of the weight of the ships inertia and the power of the tug approaches being equal, then the ships center of turn will__________________
virtually be at the point where the tugs force is positioned
Define “drifting moment, and movement element”
Consisting of the moment between the point of balance of the wind force, and the point of balance of the under water resistance, which is mainly determined by the ships trim; combined with the leeward movement of the ship
Define “wind force moment”
Between the point of balance of the wind force, and the ships center of turn, which varies according to the ships speed through the water
Define “drifting movement”
the movement of the whole ship to leeward
Define “ wind force point”
Is the point where the force of wind blowing on the ships side, including the superstructure and any deck cargo, is balanced or centered and will be somewhere on the ships surface. The wind force point will change or move if the relative direction of the wind changes, due to a change of the ships speed and or an alteration of course.
Define “ wind resistance point”
of a ship, resisting the drifting movement due to the wind, is the point on the leeward side of the underwater section of the ship, at which all resistance moments balance. Only if the relative direction of the wind changes, so will the wind resistance point, resisting the force of the wind change.
Define “ drifting moment lever”
the distance between the wind force point and the wind resistance point, measured at right angles to the direction of the wind.