Page 126 - Ship Construction.DJ Eyres 6Ed

Ch12-H8070.fm Page 115 Wednesday, October 18, 2006 6:55 AM

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Ship Drawing Office, Loftwork and CAD/CAM

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งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
This chapter describes the original functions of the ship drawing office and
subsequent full or 10/1 scale lofting of the hull and its structural compo-
nents and the current use by shipyards of computer aided design (CAD) for
these purposes. The subsequent introduction and extensive use of com-
puter aided manufacturing (CAM) in shipbuilding is also covered.

Ship Drawing Office
The ship drawing office was traditionally responsible for producing detailed
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working structural, general arrangement and outfit drawings for a new ship.
It was also common practice for the drawing office to contain a material
ordering department that would lift the necessary requirements from the
drawings and progress them.
Structural drawings prepared by the drawing office would be in accordance
with Lloyd’s or other classification society rules and subject to their approval;
also owner’s additional requirements and standard shipyard practices
would be incorporated in the drawings. General arrangements of all the
accommodation and cargo spaces and stores would also be prepared, incor-
porating statutory requirements as well as any shipowner’s requirements
and standards. Outfit plans including piping arrangements, ventilation and
air conditioning (which may be done by an outside contractor), rigging
arrangements, furniture plans, etc. were also prepared. Two plans of particular
significance were the ships ‘lines plan’ and ‘shell expansion’.

LINES PLAN A preliminary version of this was, in effect, prepared at the
time of the conceptual design to give the required capacity, displacement
and propulsive characteristics. It was subsequently refined during the
preliminary design stage and following any tank testing or other method of
assessing the hulls propulsive and seakeeping characteristics. The lines plan
is a drawing, to a suitable scale, of the moulded lines of the vessel in plan,
profile, and section. Transverse sections of the vessel at equally spaced sta-
tions between the after and forward perpendiculars are drawn to form what
is known as the body plan. Usually ten equally spaced sections are selected