Small ship having outer shell formed by plastic deformation and method of producing same

A small ship made of plurality of prefabricated sections, which are made at a factory by a plastic deformation process, such as stamping or rolling, and of a dimension, size and shape such that an overland transportation by road thereof is possible. The sections are transported to a site located at a coastal zone, and connected to each other thereat to thereby build a ship.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a novel structure of a small ship, in 
particular, to a construction of a small ship able to be built from 
prefabricated units. The term small ship as used in this specification 
refers to ships used mainly for leisure activities or sightseeing, or to 
small fishing boats. 
2. Description of the Related Art 
The construction of small ships is divided roughly into two types, as 
explained hereinbelow. 
In the first type of construction, a shape of the ship is molded from a 
plastic material and allowed to solidify. Then the molded plastic shape is 
laminated with a reinforcing material, such as a glass fiber, whereby the 
shell of the ship is obtained. The shell is then usually strengthened, 
from the inside, by strengthening members such as a keel, cross members, 
and bulkheads. 
In the second type of construction, a skeletal structure such as a keel and 
cross members is first fixed together, and the shell is then fixed to the 
skeletal structure. Plates of, for example, wood, steel or aluminum are 
used as the shell. An example of this type of construction is a ship built 
by a strip-planking method. The first type of construction is widely used, 
since mass production becomes possible once a mold is made. Nevertheless, 
this method has a drawback in that much labor is required for the curing 
of the plastic material to obtain a laminated reinforced material, using, 
for example, glass fibers, and this drawback is accompanied by a 
difficulty in maintaining good working environmental conditions. 
Furthermore, the thus-built ship body will last long after the service 
life of the ship is exhausted, and it is difficult to dispose of the body, 
thus causing a drawback in that it cannot be recycled. 
Furthermore, if the size of the ship body is increased, the making of the 
mold becomes complicated, and thus a reduction of a manufacturing cost 
cannot be obtained unless mass production is possible. 
The second type of construction provides less freedom with regard to the 
shape of the ship which can be built, because the shell is fixed to the 
prefabricated skeletal structure. From the viewpoint of maintenance, an 
aluminum ship is advantageous, but a problem arises in that the building 
costs are high in comparison with those of the FRP ship, when the prior 
construction type is employed. In the case of the aluminum ship, in 
particular, an enormous affect is exerted by a distortion generated when 
welding is done, whereby the number of working units must be increased to 
eliminate the distortion. 
Both of types of construction must be used in coastal zones when the ship, 
even if small, is of a size that makes overland transportation difficult 
(a ship having a length of more than 2.5 meters is very difficult to 
transport overland), and thus the number of shipbuilding sites is limited, 
and sometimes there is insufficient manpower available at the site. 
SUMMARY OF THE INVENTION 
Therefore, an object of the present invention is to provide a construction 
of a ship of which a substantial part thereof can be built at a site other 
than a coastal zone, to thereby reduce the amount of construction work to 
be carried out at the coastal zone, and by which a ship shell having a 
precise and desired shape can be obtained. 
According to a first aspect of the present invention, a small ship is 
provided which comprises a plurality of prefabricated sections having a 
predetermined size and shape suitable for overland transportation, the 
sections being welded together to obtain a shell of the ship, each of the 
sections comprising at least one outer plate member obtained by a plastic 
deformation process. 
This type of construction enables a small ship to be built from 
prefabricated sections which are transportable overland, and thus such a 
ship can be built regardless of regional limitations. 
Furthermore, since the outer plates constructing the outer shell member of 
the ship can be preformed to a desired curved surface by a plastic 
deformation process, such as stamping or rolling, a desired shape of the 
ship can be easily obtained. 
According to the second aspect of the present invention, a method of 
building a small ship is provided, which comprises the steps of: 
producing separate sections of a size suitable for overland transportation; 
transporting the separate sections overland to a location at which the ship 
is to be built, and; 
connecting the transported separate sections to each other to form a shell 
of the small ship. 
This method allows the sections to be produced at an area other than a 
coastal zone, and only a connecting step is required at the coastal zone 
to obtain a ship.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment of the present invention will be now described. FIG. 1-(a) 
and (b) schematically illustrate sections 1 to 12 by which a small ship 18 
is built. The ship 18 is built by a total of eleven ship sections 1 to 11 
and one pilot house section 12. Each of the sections 1 to 12 has a maximum 
width of less than 2.5 meters, so that overland transportation is possible 
without special permission as stipulated in the Japanese Load 
Transportation Vehicle Law, Safety Rules, Article 2. 
FIG. 2 is a schematic diagram of a process for obtaining a ship according 
to the present invention. 
In this drawing, reference numeral 2 denotes a factory for producing the 
prefabricated sections. In this factory 2, an aluminum plate 6' taken from 
a roll 6 is stamped by a process 8 to produce outer plates which form a 
shape of each of the sections. During this process, a production technique 
and automated technique employed for the production of automobiles can be 
used. Instead of the stamping process, a rolling or other plastic 
processing technique by which the plate members can be subjected to a 
plastic deformation to obtain a desired shape, may be employed. Typically, 
each of the sections 10 is composed of a plurality of plates obtained by 
the plastic deformation process. These plates are welded together to form 
a desired shape of the section. 
In this case, since each of the sections has a maximum width of 2.5 meters, 
i.e., is within the range permitted by said safety rules, it is possible 
to obtain a shape of each of the sections along a desired curved surface, 
which increase the freedom of the design of the shape, compared with an 
aluminum boat based on the conventional construction method. 
Furthermore, according to this type of construction, preferably the 
sections are made in such a manner that they form the bulkheads dividing 
the ship, i.e., the sections are closed at all side walls thereof made of 
aluminum plate, making it easy to maintain a desired precision of the 
shape of the sections. It is, of course, possible to provide openings 10a 
at the side walls (bulkheads) of each of the sections, wherever necessary. 
When necessary, a skeletal strengthening structure 20 is fixed inside each 
of the sections. The welding of the outer plates, the welding of the outer 
panels to the skeletal strengthening structures, or the welding between 
the skeletal strengthening structures, may be automated to a great extent 
by employing, for example, a laser welding method. 
Note, the end portions of the outer plates of each of the sections are 
provided with a flange having a particular shape, to facilitate a 
connection of one plate to an adjacent plate of the sections. This will be 
described later in relation to FIGS. 3 and 4. This construction is 
particularly advantageous when building an aluminum boat, but can be 
adopted when building a steel ship. 
The thus prefabricated sections are transported overland by trucks 4 to a 
shipbuilding site located at the coast. 
At the ship building site, the strength required for a ship and the 
strength obtained when the sections are connected to each other are 
compared, and when it is determined that a required strength cannot be 
obtained, longitudinal members, such as a keel 12, are used for 
strengthening the structure. The sections as transported are connected to 
the keel 12 and to each other. This is accomplished by using a laser 
welding machine 14. 
The use of the laser welding machine 14 ensures that the welding 
deformation is relatively suppressed to a very small value. Furthermore, 
little welding traces appear, and thus the usual process for correcting 
welding traces is made easier. According to this construction, the welding 
points are located substantially on one plane, and thus the laser welding 
can be employed over a wide range and can be easily automated. Even if a 
conventional welding technique is used, the location of the welding spots 
substantially in one plane allows an easier automation thereof. 
After the major portion of the body of the ship is thus constructed, the 
interior work, for example, decoration, is carried out to finally obtain a 
small ship 18. Note, the interior decoration work can be partly done at 
the factory 2. 
A method of connecting the sections will be described in detail. 
FIG. 3 shows a method of connecting the sections 10-4 and 10-5. 
Each of sections blocks 10-4 and 10-5 in this embodiment is formed by two 
aluminum plates 24 and 26, which are connected to each other by a 
strengthening structure 22 having a closed shape. This structure 22 25 
comprises a longitudinally extending, inwardly recessed flange portion 22c 
on one end of the plate 24. This flange portion 22c is connected to the 
end face of the second plate 26 at welding points 22a and 22b, such that a 
space 22d is formed. The flange portion 22c of the skeletal strengthening 
structure 22 i preferably formed at the same time as the plates 24 and 24 
are stamped or rolled at the factory 2. This welding at the points 22a and 
22b can be done at the factory 2 when the section is made. Note, this 
skeletal strengthening structure 22 can provide a desired strength even if 
it has a partly open construction. In addition to this skeletal 
strengthening structure, a further reinforcing can be provided when 
necessary by using a skeletal reinforcing structure 20a extending fore and 
aft of the ship, or by a skeletal reinforcing structure 20b extending 
across the beam of the ship. Note, the structure 20a and 20b are 
preconnected to the inner surface of the sections at the factory 2. 
The method of connecting the sections to each other is now explained. 
First, a skeletal strengthening structure 23 is located between adjacent 
sections in the longitudinal direction of the ship. As shown in FIG. 4, 
the skeletal strengthening structure 23 is arranged between the sections 
10-3 and 10-5. A flange portion 23c is provided on the block 10-3, at one 
end thereof in the longitudinal direction, during the stamping-out of this 
section 10-3. This flange portion 23c is connected to the outer panel of 
the adjacent block 10-5 at welding points 23a and 23b, whereby a closed 
strengthening structure is obtained. Note, instead of the closed skeletal 
structure 23, the sections 10-5 and 10-7 in the longitudinal direction of 
the ship are connected to each other by transverse bulkheads 30 and 31. 
Namely, a rear side bulkhead 30 of the section body 10-5 is connected to a 
front side bulkhead of the section body 10-7. In this case, since these 
bodies are welded together, except where openings 10-a are formed, a 
strong connection of the front and rear sections is obtained. 
Next, a connection of right and left side sections will be described. In 
this embodiment, a keel 12 is laid from fore to aft of the ship, and each 
of the blocks is welded so that a closed cross-section skeletal structure 
is formed with respect to the keel 12. As shown in FIG. 3, the blocks 10-4 
and 10-5 are provided with a flange 28c which is connected to the keel 12 
at welding points 28a and 28b, so that spaces 28d are formed, whereby a 
closed strengthening structure is obtained. Note, the flanges 28c are 
formed when the section is made at the factory 28. 
Although the embodiment as illustrated uses the keel 12, this keel 12 is 
not required when the ship is very small. In this case, in place of the 
keel, a skeletal structure which corresponds to the structure 22 is formed 
between the right side and left side sections. 
Where longitudinal bulkheads 32 are also arranged between the left side and 
right side sections, these bulkheads 32 are welded to each other at 
suitable points, and thus a much more rigid connection between the right 
side and left side sections is obtained. In this embodiment, the 
longitudinal bulkheads 32 are arranged between the blocks 10-4 and 10-5. 
In addition to the construction as shown in FIGS. 3 and 4, the skeletal 
structure having a closed cross-section and located between the outer 
panels or at the boundaries of the sections can have the construction as 
shown in FIG. 5. 
In the construction as shown in FIG. 5-(A), a flange a is formed on one of 
the outer panels and a flange b is formed on the other outer panel, and 
these flanges a and b are welded along the portion d. Thereafter, a third 
member c is applied thereto and welded along the portions e, whereby a 
skeletal strengthening structure having a closed cross-section is formed 
between the outer panels. 
In the construction as shown in FIG. 5-(B), a third member c is arranged 
inside of the ship. This construction allows only one welded portion to 
appear on the outer surface of the ship body, which facilitates the 
correction of welding traces. 
The construction shown in FIG. 5-(C) provides a skeletal strengthening 
structure having a closed cross-section without the use of a third member, 
and as a result, welding distortions can be greatly reduced. Openings f 
can be formed when necessary, to lower the weight. 
FIG. 5-(D) shows a structure having a rectangular closed cross-sectional 
shape and FIG. 5-(E) shows a structure having a semi-circular closed 
cross-sectional shape. 
These cross-sectional shapes, and the size thereof, can be suitably 
selected in accordance with the required use. 
The constructions shown in the embodiments explained above are particularly 
suitable for an aluminum boat or steel ship. In particular, when the 
present construction is applied to an aluminum boat, a lowering of the 
shipbuilding costs can be obtained such that it is the same as or cheaper 
than the cost of producing an FRP ship by the conventional method. 
Therefore, it is expected that the aluminum boat will become popular and 
replace the FRP boat, since it is easier to maintain and is easily 
recycled. 
The use of the construction according to the present invention allows the 
many steps required for building a ship to be carried out without regional 
limitations, thereby obtaining an advantage of the use of a mass 
production system. Further, since each of production units has a maximum 
width of at most 2.5 meters, the production system, production techniques, 
and automation techniques used for automobiles can be applied, thereby 
obtaining a greater rationalization of the ship production system. 
Furthermore, the outer shell of the ship preformed to a desired shape by a 
plastic deformation process allows the shape of the ship to be designed as 
desired, and therefore, a short term and low cost production of ship 
bodies having a high performance and an aesthetically pleasing appearance 
is realized. 
Although the present invention is described with reference to the attached 
drawings, many modification and changes can be made by those skilled in 
this art without departing from the scope and spirit of the invention.