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AFT END

ARRANGEMENTBy

Group 1

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OBJECTIVES

Understand the design of the aft endstructure with respect to local loadsand stresses.

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INTRODUCTION

The aft end of the ship refers to thestern of the ship within 0.25 lengthfrom the aft perpendicular. The aft

end includes the main hull andsuperstructure including the poop.

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Stern Construction

Cruiser Stern Transom Stern

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General Aft Arrangement

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Cruiser Stern

This presents a pleasant profile andreduces resistance probably becauseof the increase in waterline length

but at a penalty of a longeroverhang. It is likely to be subject toa greater slamming force than the

transom stern.

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Cruiser Stern

Associated with cruiser stern arecant frames. Cant frames are framesconstructed at an angle to the centre

line of the ship so that the entirearea of the stern plating can bestiffened at regular intervals. Where

the span of the frame is long,horizontal stringers are fitted.

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Transom Stern

This provides foreasierconstruction.Transom stern alsoprovides for agreater deck area.Most merchantships are fitted

with transom sternbecause it is easierto fabricate.

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Transom Stern

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Aft Peak Tank

The aft peak is the after-most part ofthe hull structure. It is normally usedfor the storage of fresh water or

ballast and it provides a degree ofprotection to all spaces forward ofthe aft peak bulkhead.

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APT

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Aft Peak Tank Construction

The following members arenormally found in the aft peak tankconstruction:

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1. Stern Frame

The shell plating at the aft end isterminated by the stern frame. This isusually a casting, but fabrications and

forgings are some times used. The shapeof the stern frame depends on thedesign of the stern, the propeller and therudder arrangement. In single screw

ships, the stern frame has a boss on thecentreline for the tailshaft to pass thru.

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Stern Frame

An adequate aperture is provided forthe propeller to operate in . Thelower part of the stern frame may

provide a support for the rudder postor an overhang section may providegudgeons for the rudder pintles.Twin screw ships have a stern frame

which is only required to support therudder pintles and is thus muchreduced in size.

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2. Solid Floor

It is located at every frame space fora stern with a transverse framingsystem.

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3. Centerline Longitudinal Wash

Bulkhead.

It is normally fitted to reduce thefree surface effects. It is stiffened byvertical stiffeners and girders as

necessary.

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4. Rudder Trunk

It is a section which is found in thestern for the entry of the rudderstock into the steering gear room.

The lower part of rudder trunk isopen to the sea, but usually providedwith an inspection manhole for

viewing. The trunking above this isthen constructed to be watertight,penetrated only by the rudder stock.

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5. Stern Tube

This is housed in the APT. it housesthe propeller shaft and bearings. Thetail shaft within the stern tube is

either oil or water lubricated.

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Stern Tube

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RUDDERS

It is an underwater appendage thesurface of which is used to generatesufficient force to steer the ship

when it is in motion. A single rudderis fitted in ships with single tail shaftor single propeller. Twin rudders are

fitted on ships with twin screw ortwin propeller arrangements.

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Rudders

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Rudders

Construction of a typical rudder formerchant ships:

1. Normally made from standardstreamlined profiles.

2. A typical rudder will be constructed ofplates stiffened by horizontal and verticalwebs.

3. A coupling palm is normally provided at

the top of the rudder for attachment tothe rudder stock.4. Lifting eyes are provided for lifting and

dismantling of the rudder.

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Rudders

5. Drain plugs are provided at the topand bottom for drainage, coatingand testing purposes.

6. A closing plate is fitted on one sideof the rudder. This closing plate isthe last piece of plate to be fitted

after carrying out internal weldingsof the rudder.

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