AFT END AFT END ARRANGEMENTARRANGEMENT

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Group 1Group 1

OBJECTIVESOBJECTIVES

Understand the design of the aft end Understand the design of the aft end structure with respect to local loads structure with respect to local loads and stresses.and stresses.

INTRODUCTIONINTRODUCTION

The aft end of the ship refers to the The aft end of the ship refers to the stern of the ship within 0.25 length stern of the ship within 0.25 length from the aft perpendicular. The aft from the aft perpendicular. The aft end includes the main hull and end includes the main hull and superstructure including the poop. superstructure including the poop.

Stern Construction

Cruiser Stern Transom Stern

General Aft ArrangementGeneral Aft Arrangement

Cruiser SternCruiser Stern

This presents a pleasant profile and This presents a pleasant profile and reduces resistance probably because reduces resistance probably because of the increase in waterline length of the increase in waterline length but at a penalty of a longer but at a penalty of a longer overhang. It is likely to be subject to overhang. It is likely to be subject to a greater slamming force than the a greater slamming force than the transom stern.transom stern.

Cruiser SternCruiser Stern

Associated with cruiser stern are Associated with cruiser stern are cant frames. Cant frames are frames cant frames. Cant frames are frames constructed at an angle to the centre constructed at an angle to the centre line of the ship so that the entire line of the ship so that the entire area of the stern plating can be area of the stern plating can be stiffened at regular intervals. Where stiffened at regular intervals. Where the span of the frame is long, the span of the frame is long, horizontal stringers are fitted.horizontal stringers are fitted.

Transom SternTransom Stern

This provides for This provides for easier easier construction. construction. Transom stern also Transom stern also provides for a provides for a greater deck area. greater deck area. Most merchant Most merchant ships are fitted ships are fitted with transom stern with transom stern because it is easier because it is easier to fabricate.to fabricate.

Transom SternTransom Stern

Aft Peak TankAft Peak Tank

The aft peak is the after-most part of The aft peak is the after-most part of the hull structure. It is normally used the hull structure. It is normally used for the storage of fresh water or for the storage of fresh water or ballast and it provides a degree of ballast and it provides a degree of protection to all spaces forward of protection to all spaces forward of the aft peak bulkhead.the aft peak bulkhead.

APTAPT

Aft Peak Tank ConstructionAft Peak Tank Construction

The following members are The following members are normally found in the aft peak tank normally found in the aft peak tank construction:construction:

1.1. Stern FrameStern Frame

The shell plating at the aft end is The shell plating at the aft end is terminated by the stern frame. This is terminated by the stern frame. This is usually a casting, but fabrications and usually a casting, but fabrications and forgings are some times used. The shape forgings are some times used. The shape of the stern frame depends on the design of the stern frame depends on the design of the stern, the propeller and the rudder of the stern, the propeller and the rudder arrangement. In single screw ships, the arrangement. In single screw ships, the stern frame has a boss on the centreline stern frame has a boss on the centreline for the tailshaft to pass thru.for the tailshaft to pass thru.

Stern FrameStern Frame

An adequate aperture is provided for An adequate aperture is provided for the propeller to operate in . The the propeller to operate in . The lower part of the stern frame may lower part of the stern frame may provide a support for the rudder post provide a support for the rudder post or an overhang section may provide or an overhang section may provide gudgeons for the rudder pintles. Twin gudgeons for the rudder pintles. Twin screw ships have a stern frame which screw ships have a stern frame which is only required to support the rudder is only required to support the rudder pintles and is thus much reduced in pintles and is thus much reduced in size.size.

2. Solid Floor2. Solid Floor

It is located at every frame space for It is located at every frame space for a stern with a transverse framing a stern with a transverse framing system.system.

3. Centerline Longitudinal Wash 3. Centerline Longitudinal Wash Bulkhead.Bulkhead.

It is normally fitted to reduce the free It is normally fitted to reduce the free surface effects. It is stiffened by surface effects. It is stiffened by vertical stiffeners and girders as vertical stiffeners and girders as necessary. necessary.

4. Rudder Trunk4. Rudder Trunk

It is a section which is found in the It is a section which is found in the stern for the entry of the rudder stern for the entry of the rudder stock into the steering gear room. stock into the steering gear room. The lower part of rudder trunk is The lower part of rudder trunk is open to the sea, but usually provided open to the sea, but usually provided with an inspection manhole for with an inspection manhole for viewing. The trunking above this is viewing. The trunking above this is then constructed to be watertight, then constructed to be watertight, penetrated only by the rudder stock. penetrated only by the rudder stock.

5. Stern Tube5. Stern Tube

This is housed in the APT. it houses This is housed in the APT. it houses the propeller shaft and bearings. The the propeller shaft and bearings. The tail shaft within the stern tube is tail shaft within the stern tube is either oil or water lubricated. either oil or water lubricated.

Stern TubeStern Tube

RUDDERSRUDDERS

It is an underwater appendage the It is an underwater appendage the surface of which is used to generate surface of which is used to generate sufficient force to steer the ship sufficient force to steer the ship when it is in motion. A single rudder when it is in motion. A single rudder is fitted in ships with single tail shaft is fitted in ships with single tail shaft or single propeller. Twin rudders are or single propeller. Twin rudders are fitted on ships with twin screw or fitted on ships with twin screw or twin propeller arrangements. twin propeller arrangements.

RuddersRudders

RuddersRudders Construction of a typical rudder for Construction of a typical rudder for

merchant ships:merchant ships:1.1. Normally made from standard Normally made from standard

streamlined profiles.streamlined profiles.2.2. A typical rudder will be constructed of A typical rudder will be constructed of

plates stiffened by horizontal and vertical plates stiffened by horizontal and vertical webs.webs.

3.3. A coupling palm is normally provided at A coupling palm is normally provided at the top of the rudder for attachment to the top of the rudder for attachment to the rudder stock.the rudder stock.

4.4. Lifting eyes are provided for lifting and Lifting eyes are provided for lifting and dismantling of the rudder.dismantling of the rudder.

RuddersRudders

5. Drain plugs are provided at the top 5. Drain plugs are provided at the top and bottom for drainage, coating and bottom for drainage, coating and testing purposes.and testing purposes.

6. A closing plate is fitted on one side 6. A closing plate is fitted on one side of the rudder. This closing plate is of the rudder. This closing plate is the last piece of plate to be fitted the last piece of plate to be fitted after carrying out internal weldings after carrying out internal weldings of the rudder.of the rudder.