Seamanship Flashcards
The latest weather report whilst on passage indicates heavy weather. Describe preparations and precautions for safety of vessel, crew & passengers. (12)
Brief all departments
Brief all passengers
Obtain up to date weather forecasts
Close watertight doors
Engage manual steering in ample time
Remove free surface effects if possible
Anchors secured
Fit storm covers and deadlights
Take down awnings
Empty pool/jacuzzi
Improve GM of vessel if appropriate
Secure all movable objects
Check LSA gear
State when/how synchronous rolling may occur?
Caused by the ships rolling period becoming synchronous with the wave period.
Explain the dangers of synchronous rolling
Successive waves tend to increase the angle of roll of the vessel
The ship will develop negative stability
The vessel may heel beyond the angle from which she cannot return and may capsize
The ship may become difficult to manoeuvre
State courses of action to alleviate synchronous roll
Immediate Alteration of Course, Speed or GM
Describe the dangers when running before following sea
Dangers
Breaking waves over a vessel
Swamping causing flooding
Danger to expose crew on deck
Steering difficult due to poor water flow over rudder
Danger of falling of course
Danger to Crew from violent motion and lose objects
Describe the precautions to be taken when running before following sea
Adjust speed to maintain steerage
Insure engine ready at all times for manoeuvering
If possible, stay offshore
Ensure all watertight doors and openings are closed
All expose crew on deck to wear correct safety equipment
All safety equipment ready for immediate use
Experience helmsman on the wheel
All gear to be stowed securely on deck and below
A MY is on a passage, encountering 2.5 m swell on the port quarter, coupled with a secondary pattern of 2 m significant wave height on the port beam. Describe the effects and dangers this may pose to the yacht and the crew on board.
The yacht
2.5m Long period of swell on port quarter
Corkscrewing difficult to steer.
Possibility of broaching.
Autopilot unable to cope with steering
2 m swell possible risk of synchronous rolling.
Structural damage
Personal on board
Seasickness.
Tripping or falling
Difficulty moving around
Dehydration.
Fatigue, lack of sleep.
In the case of a disabled vessel, define and explain the differences between a lee-shore, or offshore situation.
Lee Shore
A shore lying on the leeward side of a ship, and onto which the ship could be blown.
Many vessels get blown on the shore because they become disabled (loss of power), resulting in subsequent grounding or insufficient power, preventing them from ‘beating out’ to seeward
Off shore
To seaward from the shore, moving away from the shore towards open water.
Vessel would carry out a deeper water (less opportunity to anchor) and possibility of worse sea/weather conditions .
A vessel has become disabled off the coast with an onshore wind. Staton actions to be taken on board for safety of the vessel and crew.
Safety of the vessel
Slow the drift of the vessel by causing a drag,anchor or sea anchor
Vessel would normally lie beam on to the wind, bring the bow or stern into the sea
Roll could become synchronous bring bow in to sea the
Raise watertight integrity
May Day, alert authorities
Call for assistance tug or tow
Safety of crew.
Ensure access to emergency equipment is prepared.
Danger of MOB, place upper decks off-limits
Appropriate PPE
Restrict movement inboard to prevent injury to Crew
Increase alert level of Crew, don lifejackets
Cover dangerous objects
A motor yacht is to take a disabled MY in tow, list 4 methods to pass the tow line (approaches)
Arc approach- approach in arc from seaward ,keep to windward of disabled vessel, when abeam pass towline
45 degree approach- calm conditions
Parallel approach - calm conditions, approach from the stern, keep safe distance
Crossing the stern- approach towards stern, line is passed on windward quarter, transfering line to bow may be dangerous
Passing line via,
-Messenger line
-Heaving line
-Line throwing device
-Float line
Shallow water effect, what is it called?
Squat
Explain why squat occurs
Squat is caused when water that should normally flow under the hull encounters resistance due to the close proximity of the hull to the seabed.
This causes water to move faster, creating a low pressure area with lowered water level surface. (Bernouli principle)
The effect is greater at high speeds. The swallower the water and larger the vessel the greater the effect.
State observations that may indicate squat
Vessel to dip towards bow or stern
Difficulty steering
Reduction in ground speed
Increased vibration aft
Increase in draft
Sketch diagram to show pressure fields around the hull of a vessel underway
Draw
List 6 criteria the mariner should consider in the selection of an anchorage position
Depth of water
Length and draft of vessel
Amount of chain
Type of holding
Proximity of dangers
Proximity of adjacent ships
Protection from surrounding land
Tidal range
