Dredging means when the vessel moves under the influence of the tidal stream but she is on anchorage, and her anchor is in short lay and it is dragging in the sea bed, instead of being embalmed in sea bed
Her speed dragging the anchor is controlled i.e. its speed should not increased by the speed of stream sand having headway of the water. Her rudder is used for steering the ship and strong tidal stream is necessary for this kind of operations. This type of operation is used when there is no tugs available.
Role of an Anchor in a Ship
Basically anchor is a metal device attached to ship or vessel by a metal chain or by a cable .When anchor is let go it strikes the sea bottom. the stock being longer and heavier than arms assumes a horizontal position and as soon as the anchor being stressed thus lower arms and flunk be embalmed. The stock provides anchor a great stability. It prevent it from rotating under heavy stress or load.
There are different types of anchor but most commonly used anchor is Stock less anchor-it has no stock and it is secured in hawse pipe of the ship it is easy to secure and easy to let go the entire head moves about 45 ˚ from the axis.
Anchor plays an very important role in ship nowadays it is used in maneuvering the ship, it is used in turning the ship ins some conditions. It is also used for berthing and it is basically used as break as ship.
Procedure of Anchoring
- Using VHF contact engine room to on power on deck
- Then carry equipment such as spike, hammer, crowbar, oilcan, google, oilcan, google, portable VHF set, torch if anchoring is in night .
- Remove house pipe cover let go the lashing in chain locker
- Ensure that the breaks are on and the windlass is out of gear
- Turn the windlass over slowly and oil the movable parts of windlass before use
- Open drain cock to drain water and close after drainage
- Put one anchor in gear .(see that gears are clear to engage first )
- Unfasten the lashings and devils claw
- Remove the cement and the cover or other fillings from spurting pipe
- Remove compressor
- Make sure that the anchor load is on the break and the gear must be in all clear
- Take out gear
- Depending on the weather and captains instruction prepare the other anchor using same guidelines
- Inform the Officer on watch(OOW) using VHF on bridge that the anchor is ready to lower clear hawse pipe
- Place anchor in gear
- After getting the order from Officer on watch(OOW), take off break and drop the instructed shackles
- Screw the break tightly home and take out the gear
- Turn anchor light drop anchor ball. Creak weather it dragging inform bridge
Anchors work in deep water
- Face the wind or current when approaching the anchoring area
- Reduce the ships speed up to or less than speed of windlass walk –back capacity which is generally 0.3 knots of ships speed
- The anchor should walked back all to the sea bed
- As the vessel moves astern the cable will grow
- Ships’ heading on final approaching should be faced into the wind and current which can provide a good advantage to control good ships heading when anchor just folding and also for minimizing of swinging rate to windward or current ward
- Ships speed during walk back must be controlled as zero with speed over the ground by gps and or Doppler sonar or less than the speed of windlass walk back speed
- Check the depth of water the type of sea bed and the weather condition affect deep water anchoring.
Do ship anchor in rough weather ?
The answer is yes and no. It is a decision that is determined by the size ,weight and type of the vessel , the severity and type of the storm event, where the storm is experienced( e.g. shallow/ deep water, proximity to other vessels, permanent structure, land/reef, wind/current direction in relation to the aforementioned points ) and the quality, suitability and amount of anchoring equipment, including deployment and retrieval systems the boat has. Its just the beginning but every one of the above comes into play before an anchor should be deployed . This is where the most important element of making the decision to drop the hook or leave it stowed comes in, Seamanship . A boats skipper will make the order after taking all of the above imputes on board and probably a few more I have not considered. The physical probability of successfully deploying an effective anchor to the prevailing conditions must be considered. An inadequate and/or badly set up anchoring will almost certainly result in a serious if not catastrophic FU. This means those charged with deployment and retrieval need the highly specialized knowledge called… Seamanship.
Alternatively the decision can be made to sail the storm out. Ideally this requires clear water, minimal obstructions and well clear of land mass, reef and shoal/shallow water this is usually referred to as sea room. There has never in the history of absolutely bloody everything nautical that a sailor loves more, when the stuff is flying of the fan than a big dollop of sea room. Due to often significant water depth ,conventional anchoring becomes irrelevant. Instead maneuvers such as running before the storm, heaving too, laying abeam, stemming the storm( using power or a sea anchor of some type) or maintaining coarse, usually at reduced speed . As with every other scenario discussed here the choice will be made using skill, knowledge, fitness and physical /mental dexterity also known as…well you know. There have been millions of words and illustrations generated over millennia on the safety of a vessel at sea, knowing when to drop and when to not and how to do one or tether taking up a good chunk of these works.