Figure 8-3. Application of a box patch.
shows a metal box patch held in place by shoring; and
the hook bolts are used to apply a patch. The long
view C shows a metal box patch welded in place over a
shanks are threaded and are provided with nuts and
hole that has jagged edges.
washers. Wood (or sometimes steel) strongbacks are
used with hook bolts.
A hinged patch is designed for use over relatively
small holes. This patch has no vertical support to hold
To use a hook bolt, insert the head end of the bolt
it in place. Figure 8-4 shows a hinged plate patch
through the hole in the hull. Rotate or adjust the bolt
before, during, and after installation.
until it cannot be pulled back through the hole. Slide a
pad or gasket that is backed by a plank or strongback
over the bolt. Secure the patch by tightening the nut.
Generally, these bolts are used in pairs. Hook bolts
STEEL PLATE WHICH
CAN BE FOLDED TO GO
can be used with a variety of patches and in various
THROUGH A HOLE.
USE WITH A PILLOW OR
RECOMMEND SIZE UP TO
The folding T-shaped hook bolt (figs. 8-6 and 8-7)
has a hinge where the shank joins the crosspiece. This
bolt can be folded and inserted through a small hole.
When the bolt is pulled back, the crosspiece catches
on the hull plating. By using this bolt, a crewmember
standing inside the ship can put a patch on either the
inside or the outside of the ship. By using a retaining
line on the bolt, a strongback and a pillow can be
threaded over the line and the entire patch folded and
placed through the hole. When the line is hauled in,
Figure 8-4. Application of a hinged plate patch.
the patch fits against the ship. The patch can be
re-adjusted to give a tighter fit. It is also possible to
A hook bolt is a long bolt that is usually fabricated
push the pillow and plate over the shank inside the
from round steel stock. Hook bolts come in a variety
ship to make an inside patch. Nuts and washers are
of diameters and shapes. The head is shaped so that
provided to hold and tighten a patch; often large wing
the bolt can be hooked to the plating through which
nuts are used. Figure 8-6 shows one way in which a
the head has been inserted. Figure 8-5 shows
folding T-shaped hook bolt can be used to secure a
T-shaped, L-shaped, and J-shaped hook bolts and how