Bow and Stern.docx

8/14/2019 Bow and Stern.docx

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Bow and Ster n

Pounding and the additional provisions to withstand such pounding:

Heavy pitching assisted by heaving as the whole vessel is lifted in a seaway may subject the

forepart to severe blows from the sea. The greatest effect is experienced in the light ship

condition. To compensate for this the bottom is strengthened from 0.5L to between 0.25L and

0.3L from forward depending on the block coefficient, unless the ballast draught forward is over

0.04L.

Bottom framed Longitudinally

Longitudinals are to be spaced 1000mm apart between 0.2L and 0.3L from forward and 700mm

apart between 0.2L from forward and the collision bulkhead. Plate floors are to be fitted alternate

frames, side girders not more than 2.1m apart.


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Bottom framed Transversely

Frame spacing abaft 0.2L from forward is not to exceed 1000mm and between 0.2L and the

collision bulkhead 700mm. Forward of the collision bulkhead 610mm. Plate floors are to be

fitted at every frame. Intercostal side girders are to be not more than 2.2m apart with half height

side girders not more than 1.1m apart, the girders extending as far as is practicable.

Panting

This is a stress, which occurs at the ends of a vessel due to variations in water pressure on the

shell plating as the vessel pitches in a seaway. The effect is accentuated at the bow when making

headway.


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Panting arrangements are to extend 0.15L from forward and abaft the after peak bulkhead.

Tiers of beams spaced not more than 2000mm apart vertically are to be fitted at alternate frames

in the fore peak or below the lower deck above the water line if the forepeak is small.

Alternatively perforated flats may be fitted in lieu of panting beams 2.5m apart vertically.


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Tiers of beams are to be supported at the centreline by a partial wash bulkhead or pillars. Beams

are to be bracketed to frames and the frames to which no beams are attached are to be bracketed

to the stringer. Stringer plates attached to the shell are to be fitted at each tier of beams.

Abaft the collision bulkhead intercostals side stringers having the same depth as the frames are to be fitted in line with those forward of the collision bulkhead and are to extend aft for 0.15L from

the fore end. Stringers may be omitted if the shell plating is of increased thickness.

Abaft the after peak bulkhead the structure is to be efficiently stiffened by deep floors and tiers

of beams in association with stringers spaced 2500mm apart vertically.


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Stern Frame

Stern frames may be cast/ forged or fabricated from steel plate. In the case of cast or forged steel

frames they may be in one piece or in two or more sections riveted or welded together (thermit

welding).

Where a riveted connection is used the two sections of the bar are scarphed together and the class

rules for the scarph are 3D and the depth as one and one third D, where D is the depth of the bar

used in the construction of the frame.


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A scarph fitted in a rudder post should not be above the highest gudgeon.

Cast steel and fabricated stern frames are to be strengthened at intervals by transverse webs. All

stern frames are to be efficiently attached to the adjoining structure and the lower part of the

stern frame is to be extended forward to provide an efficient connection to the flat plate keel.

With larger stern frames there is a tendency for the whole stern or propeller post and adjacent

sections to be fabricated.

Documents

Bow and Stern.docx