Page 130 - Ship Construction.DJ Eyres 6Ed

Ch12-H8070.fm Page 119 Wednesday, October 18, 2006 6:55 AM
Ship Drawing Office, Loftwork and CAD/CAM 119
where strakes ‘run out’ as the girth decreases forward and aft. This draw-
ing was often subsequently retained by the shipowner to identify plates
damaged in service. However a word of caution is necessary at this point
because since prefabrication became the accepted practice any shell
expansion drawing produced will generally have a numbering system
related to the erection of fabrication units rather than individual plates.
However single plates were often marked in sequence to aid ordering and
what was known as a ‘scrieve board’. ึกษาเท่านั้น---
production identification.

งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
Loftwork Following Drawing Office

The mould loft in a shipyard was traditionally a large covered wooden floor
area suitable for laying off ship details at full size.
When the loftsmen received the scale lines plan, and offsets from the
drawing office, the lines would be laid off full size and faired. This would
mean using a great length of floor even though a contracted sheer and plan
were normally drawn, and aft and forward body lines were laid over one
--- ใช้เพื่อการศ
another. Body sections were laid out full size as they were faired to form
ึ
The scrieve board was used for preparing ‘set bars’ (curvature to match plate)
and bevels (maintain web of frame perpendicular to ships centre line) for
bending frames and for making templates and mouldings for plates which
required cutting and shaping.
Shell plates were developed full size on the loft floor and wooden templates
made so that these plates could be marked and cut to the right shape before
fitting to the framing on the berth.

10/1 SCALE LOFTING In the late 1950’s the 10/1 lofting system was
introduced and was eventually widely adopted. This reduced the mould
loft to a virtual drawing office and assisted in the introduction of produc-
tion engineering methods. Lines could be faired on a 10/1 scale and a 10/1
scale scrieve board created. Many yards operated a flame profiling
machine (see Chapter 13) which used 10/1 template drawings to control
the cutting operation. In preparing these template drawings the devel-
oped or regular shape of the plates was drawn in pencil on to special
white paper or plywood sheet painted white, and then the outline was
traced in ink on to a special transparent material. The material used was
critical, having to remain constant in size under different temperature
and humidity conditions and having a surface which would take ink
without ‘furring’. Many of the outlines of plates to be cut by the profiler
could be traced directly from the scrieve board, for example floors and
transverses.