Page 248 - Ship Construction.DJ Eyres 6Ed

Ch21-H8070.fm Page 237 Wednesday, October 18, 2006 6:59 AM
Aft End Structure 237
adopted in lieu of cant frames, by horizontal stringers extending to the first
transverse frame.
Cant frames are not required where the transom stern is adopted, as the
flat stern plating may be stiffened with vertical stiffeners (Figure 21.2).
Deep floors and a centre line girder are provided at the lower region of the
transom stern construction.
Panting arrangements at the aft end are dealt with in Chapter 17.
shape complicated. ้เพื่อการศึกษาเท่านั้น---

งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
Stern Frame
It has already been indicated that the form of the stern frame is influenced
by the stern profile and rudder type. To prevent serious vibration at the
after end there must be adequate clearances between the propeller and
stern frame, and this will to a large extent dictate its overall size.
The stern frame of a ship may be cast, forged, or fabricated from steel
plate and sections. On larger ships it is generally either cast or fabricated,
the casting being undertaken by a specialist works outside the shipyard.
To ease the casting problem with larger stern frames and also the trans-
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port problem it may be cast in more than one piece and then welded
together when erected in the shipyard. Fabricated stern frames are often
produced by the shipyard itself, plates and bars being welded together to
produce a form similar to that obtained by casting (see Figure 21.3).
Forged stern frames are also produced by a specialist manufacturer and
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may also be made in more than one piece where the size is excessive or

Sternpost sections are of a streamline form, in order to prevent eddies
being formed behind the posts, which can lead to an increase in the hull
resistance. Welded joints in cast steel sections will need careful preparation
and preheat. Both the cast and fabricated sections are supported by hori-
zontal webs.
Two forms of stern frame are shown in Figure 21.3, one being a casting
and the other fabricated, so that the similarity of the finished sections is
indicated. Of particular interest is the connection of the stern frame to
the hull structure for, if this is not substantial, the revolving propeller
supported by the stern frame may set up serious vibrations. The rudder
post is carried up into the main hull and connected to the transom floor
which has an increased plate thickness. Also the propeller post may be
extended into the hull and connected to a deep floor, the lower sole piece
being carried forward and connected to the keel plate. Side shell plates
are directly welded to the stern frame (Figure 21.3), a ‘rabbet’, i.e. a
recess, sometimes being provided to allow the shell plate to fit flush with
the sternpost section.