G: Shiphandling Flashcards
How long is 1 shackle?
27.5m
How Many Shackles of free-hanging cable + weight of anchor is a windlass designed to retrieve?
3 shackles + anchor.
How much cable to use when anchoring?
Depends on: Type of holding ground (good or bad). Strength of wind and current. Length of stay at anchorage. Swinging Room Available (ie busy anchorages)
4 times depth of water for good holding ground and good conditions.
6 times for poor holding ground.
lay out extra cable for poor conditions and longer stays.
What is Squat how do you reduce it?
Shallow water effect.
Reduction in effective water depth and UKC - Draught increases and a COT
Can expect it when depth is <1.5xDraft.
Caused by Bernoulli Principle. Restricted space for water to flow under the hull, water flows at higher velocity, pressure decreases, vessel sinks bodily.
Squat Increases in proportion to the squat of the ships speed
Velocity
Block coefficient
Depth of water
Drastic reduction in speed is only way to minimise adverse affects
Fine block coefficient likely to squat by head – large block coefficient, squat by stern.
What are the requirements for a ships manoeuvring characteristics?
IMO CIRCULAR 137: Standards for ships manoeuvrability
Advance = 4.5 Ship lengths
Tactical Diameter = 5 Ship Lengths
Crash Stop = 15 Ship Lengths (20 for very large ships)
Procedure for Anchoring
Identify Suitable Anchorage Position and Scope Anchor Plan Approach to Anchorage Procedures for Bridge Team and Deck Team Prepare to Let Go Anchor Let Go Anchor Secure Anchor Watchkeeping at Anchor Dragging Anchor
Indications a Vessel is dragging anchor?
At Long Stay, cable vibrating; or going from long stay, back to short stay and back to long stay where it is dragging.
Bow cant stand into the wind.
Ships side agains the wind has not changed.
Anchor Alarm GPS
Beam Bearings
Vessel has moved outside the charted swing circle.
