19. Types of ships (part III). Special purpose ships.

Dredgers

Floating docks

Trawler others

Seiner

Hydrographic Icebreakers Rescue ships Floating “houses”

Pilot boats Tugboat Fireboats Training

Lightship Lifeboats Research

Many ships and boats have been designed to do particular jobs to help ships and shipping.

Industrial ships.

Industrial ships designed to draw out raw materials and food resources from sea. Industrial procedures may include extracting oil and mineral salts or catching and processing fish, crustacean (such as lobsters, crabs and shrimps), marine flora and fauna.

Extractive ships - ships used solely for catching (fish, sea mammals and plants). According to the method of catching fish, several types are distinguished among which are: Trawlers - the most widespread type of fishing vessel; The name "trawler" comes from "trawl" - a fishing net which is dragged along the sea floor.

Seiners - Seiners use a peculiar kind of net which hangs vertically in the water and has a rope at its bottom. Once the shoal of fish enters the net, the rope tightens and closes it, just like an upside-down purse. Processing ships - Their main purpose is to receive the catch from extractive ships, process it into usable products and bring it to ports. Mother ships and refrigerator fishing vessels (with conditions to freeze fish) are common representatives of this group. They also supply fishing vessels with everything necessary for their prolonged stay at sea such as fuel, food and medical assistance.

Service ships.

Service ships - vessels which serve the merchant fleets and operate in harbors, inland waters and water areas.

Ships providing navigation through different waters.

Hydrographic ships - Their purpose is to explore seas and oceans, gather data and report to hydrographic bureaus which on their part, compose maps and charts. Hydrographic ships inform seamen on possible weather changes as well. Besides which, they are in charge of all signaling devices and lightships at sea.

Pilot boats - small vessels that carry a pilot to a ship and then bring him back to the port. These pilots steer the ship through rivers and canals from one point to another by showing the safest way to go. They must be seaworthy as pilots go out in all weathers.

Lightships - Lightships look like ordinary ships, but they do not have engines, because they are towed into places which are dangerous for ships to pass through (e.g. shallows, rocks) and anchored there. They not only have a light, but also a foghorn, a radio beacon and meteorological equipment as well. Lightships have begun to decrease in number and are being replaced by navigation buoys.

Auxiliary ships. Icebreakers - They are important to shipping because northern ports and channels freeze up in winter. Ships must use these ports all the year round, therefore it is necessary to keep them open. They maintain navigation in winter by leading other vessels across ice tracks (and breaking ice-floes). Compared to common ships, icebreakers have a strong bow, powerful engines and different construction of the hull whose purpose is to make ice blocks lift up the vessel. The ship climbs up the thick ice and cracks it with its hull weight.

Tugboats tow barges along canals and rivers and guide huge passenger liners and freighters in and out of harbours. Tugs usually have the bridge and funnel well forward to leave a clear space aft for the tow rope which is attached to the towing hook or bits at the after and of the superstructure. They can be divided into four basic types. Some are designed as river tugs to work on rivers. Others are designed as harbour tugs and help ships in and out of ports and harbour. Two other types of tugs, which of growing importance are coastal tugs and oceangoing tugs. These go out to help ships in difficulty at sea. Oceangoing tugs take part in rescue and salvage work. They are equipped with pumps, fire-fighting apparatus, and comfortable accommodations for a large crew. Tugs must be designed to satisfy three important requirements. They must be stable in all conditions. They must also be maneuverable and be powerful enough to move ships of far greater size.

Ships providing safety. Rescue ships - powerful high-speed crafts, able to operate in any conditions and being equipped to save ships which have damage or have suffered an accident aboard and need urgent help. Rescue ships can give help in underwater repairs and provide medical assistance. Fireboats - equipped to fight fire aboard ships and floating platforms (e.g. oil drills) by spraying foam and water from a distance of 60-100 meters.

A very important type of boat is the lifeboat. Lifeboats are of many different types. Lifeboats must be strong, stable and maneuverable and their crew must be well trained.

Ships with special purposes. Research vessels- ships used for exploring waterways, surveying the sea bottom and ocean processes, locating natural resources (petroleum, cobalt, copper, iron, etc.) and observing marine life. These ships have winches and other devices to assist research underwater vehicles and nets. They also have laboratories inside.

Training ships - for training cadets Floating "houses" - hospitals, hotels, exhibitions, workshops, laboratories.

Technical ships.

Technical ships - ships which provide technical service and create the necessary conditions for ship navigation; Here are the various types of technical ships:

Dredges - These are floating vessels used to make sea- or river-floors deeper (for example, this is done when ports and canals are built or simply maintained). Dredges take out sand from the bottom and dump it on barges which bring it away. Dredgers are of three main types: they can be either bucket dredgers, which have a series of buckets which go down to the sea bed and scoop up the sand and mud; they can be suction dredgers, which suck up sand and mud like a very large vacuum cleaner; or they can be grab dredgers, which can operate like cranes.

Floating docks - the largest representatives of technical ships; Floating docks are floating vessels which cannot move on their own and serve as places for construction and repair of ships.

Others - floating cranes, power stations and workshops; cable laying ships; oil collector ships (they surround the oil spills and clear them); drill ships; offshore drilling rig supply vessels.