Vessel hull construction and method

For fabricating a double-hulled tanker, or a major component of one including at least part of longitudinal midbody, a floating drydock is used which has two independently elevatable-depressible sections. The midbody part is made of individual modules, each of which is fabricated in an upended orientation. The upended modules are successively floated onto a tilting assembly on one drydock section, tilted over and serially added to a growing midbody on the other drydock section. The two drydock sections are pumped out and flooded as the process progresses for shifting the positioning of the growing midbody and modules. Other parts, including a bow and stern are added, to provide a complete vessel.

BACKGROUND OF THE INVENTION 
In the co-pending applications of Cuneo et al., No. 07/532,329, filed Jun. 
5, 1990, Goldbach et al., No. 07/678,802, filed Apr. 1, 1991, and Goldbach 
et al., No. 07/713,990, filed Jun. 12, 1991, there are disclosed apparatus 
and methods for constructing a novel double-hulled product, which as 
panels, modules and midbodies, are useful in the construction of vessels, 
in particular, bulk carriers for crude oil and other products. 
The present invention relates to improvements in the method and products 
disclosed in the above-identified, earlier applications, the contents of 
which are incorporated herein by reference. 
In general, the invention relates to providing a double-hulled vessel 
which, compared with conventional constructions, is made with a reduced 
number of different pieces, a reduced complexity, which can be fabricated 
using a higher degree of automation, which, in many applications is more 
durable and/or needs less maintenance, and need not cost the 20 percent 
additional that a conventional double hull costs compared with a 
conventional single hull. In fact, in some instances, a double hull 
produced in accordance with the invention can successfully compete in 
price with a conventional single hull for the same duty and carrying 
capacity. 
Compared with the apparatus, methods and products disclosed in the 
above-mentioned, earlier patent application of Cuneo et al., the 
above-mentioned earlier applications of Goldbach et al., teaches a 
modified method for constructing and coating the painted subassemblies, 
for assembling the painted subassemblies into modules of the hull,, for 
launching the modules into the water on their sides, for outfitting the 
modules while in the water by installing fabricated piping and auxiliary 
structure through the open end of each module, for retrieving each 
outfitted module from the water while simultaneously turning each module 
into its final upright position and for joining each module to a 
respective adjacent module. 
As a result of a 1970's convention entered into by the major maritime 
shipping nations (the "MARPOL Convention"), bulk petroleum carrier ships 
must have separate tanks for ballast and cargo oil. Ships thereupon 
necessarily became larger in overall size for carrying the same amount of 
cargo. Fewer bulk petroleum carrier ships were built to this requirement 
than had been built to serve the same market within a comparable prior 
period. Also, new and aggressively expanding factors in the bulk cargo 
vessel field sought to capture market share by cutting out what they 
deemed excess weight in the construction of hulls for such vessels. Part 
of the reduction was accomplished by using high tensile strength steel, 
but some was accomplished by reducing the safety margin in the thickness, 
spacing and redundancy of constructional elements conventionally provided 
to accommodate loss of strength due to corrosion occurring during the 
expected life of the vessel. At the same time, carrying only ballast in 
certain tanks of the vessel, due to requirements of the MARPOL Convention, 
caused accelerated corrosion. The need for better coatings was not 
recognized soon enough; therefore, it is now believed that many bulk 
cargo-carrying ships built within the last 15 years will have 
unpredictably short useful lives. 
A conventional double-hull tanker lets ballast be carried between hulls. 
Such a ship does not need to be any larger, overall, than a conventional 
single-hull, segregated-ballast tanker. 
It is believed that in the period from 1990 to 2010, the number of tankers 
requiring replacement or remidbodying, assuming modest expansion of world 
fleet requirements, an average vessel life of 25 years, and an average 
vessel size of 85,000 DWT, is about 180 to 200 tankers per year. 
SUMMARY OF THE INVENTION 
An improved curved-plate, double-hull tanker construction is provided, 
having reduced or eliminated transverse reinforcing structure in its 
midbody, except for bulkheads. The hull, though double, can compare in 
weight to conventional single hulls, despite being entirely made of mild 
steel plate. It is made of significantly fewer pieces, with a reduction in 
welding footage. More of the steel is used in the form of plate, rather 
than more expensive shapes. Improved productivity is possible, resulting 
from standardization of parts, less scrap, greater use of jigs and 
fixtures, automated welding, blast-cleaning and painting, so that not so 
much staging is needed, the work environment can be safer, and the product 
can be produced at a lower unit labor cost. Preferably, cathodic epoxy 
painting is used for durability and reduction in problems due to blast 
cleaning, solvent evaporation and generation of refuse. Extending the 
double-hull structure from the bottom and sides of the hull to the main 
deck can provide space for fuel oil to be located safely away from the 
skin of the ship, rather than in possibly vulnerable deep tanks at the 
stern. The constructional technique is believed to be applicable to vessel 
hulls in the 70,000 DWT to 300,000 DWT range. The vessel hull midbody 
module subassemblies may be assembled into modules, hull midbodies and 
vessels using the method and apparatus disclosed in the applications of 
Cuneo et al., No. 07/532,329, filed Jun. 5, 1990, Goldbach et al., No. 
07/678,802, filed Apr. 1, 1991, and Goldbach et al., No. 07/713,990, filed 
Jun. 12, 1991. However, the prior methods for turning the modules from an 
upended to an upright condition, for assembling the modules to one another 
and for connecting major components to provide a tanker are improved by 
use of a set of two floating drydock sections, one of which has a tiltable 
platform-bearing trunnion assembly. 
The principles of the invention will be further discussed with reference to 
the drawings wherein preferred embodiments are shown. The specifics 
illustrated in the drawings are intended to exemplify, rather than limit, 
aspects of the invention as defined in the claims.

DETAILED DESCRIPTION 
Referring first to FIG. 1, a facility for transforming steel sheets into 
subassemblies for modules for double-hulled longitudinal midbodies of bulk 
cargo carriers is shown at 10. 
Raw steel plate, typically 0.5 to 1.25 inch thick and approximately 8 feet 
wide and 50 feet long, procured from a steel mill, is received by rail car 
12 (FIGS. 1 and 2), lifted off by an electromagnet-type grasping 
device-equipped crane 14 and placed either in storage 16, on one of two 
conveyor lines 18 feeding flat panel fabrication, on a rail car with an 
installed conveyor called a collocator car (not shown), or on a conveyor 
line 20 feeding curved panel fabrication. 
Raw steel plate destined for stiffened flat panels is conveyed on the lines 
18 to an automatic burning machine 22 (FIGS. 1, 3 and 4) where it is cut 
to final configuration, including any lightening holes (not shown, but see 
the Cuneo et al. application) to provide flat steel plates 24. 
Raw steel plate destined for curved panels is conveyed on the line 20 to 
the plate forming machine 26 (FIGS. 1 and 4-6), preferred details of which 
are shown in FIGS. 5-7, to produce curved steel plates. 
The plate forming machine 26 puts a constant radius curve in a succession 
of steel plates each approximately 8 feet wide and 50 feet long by holding 
one longitudinal edge of a raw steel plate in a holder 28 and bending the 
plate along its transverse axis over an upwardly convex stationary die 30 
using a series of hydraulically operated screw jacks 32 attached to a 
series of downwardly concave forming presses 34. The screw jacks 32 of the 
preferably forming presses 34, hinged at 36 to the stationary base at an 
edge of the stationary die 30 are operated simultaneously by a common 
shaft 38 driven by a hydraulic power plant 40 through a reduction gear 42. 
The fixed side of the plate is held by a series of cams 28 built into the 
forming presses. The stationary die 30 is fabricated of steel in an "egg 
crate" type weldment, so that upper edges of its elements cooperate to 
define the die. Retractable plate conveying devices 44, 46 are built into 
the plate bending machine. The devices 44, 46, respectively, have 
v-grooved and convex rimmed rollers 48, 50 at their plate edge and plate 
underscale engaging upper ends. 
The resulting curved but still not sized steel plates are then conveyed on 
the line 20 to a flame planer 52 (FIGS. 1 and 4), similar to automatic 
burning machine 22 for flat stiffened panels, where they are cut into 
precise final configuration to provide curved steel plates 54. 
Each collocator car 56, comprises a rail car with a roller conveyor on its 
deck, receives a respective fabricated flat steel plate approximately 8 
feet wide and 50 feet long from the automatic burning machine 22 and 
locates the steel plate in a precise position on the car. 
The flat steel plates 24 are transported by respective collocator cars 56 
on rails 58 which continue the flat panel lines 18 (FIG. 4) where 
kickplate stiffeners 60 are installed at precise intervals (typically of 
approximately 32 inches) in a three-stage stiffener installation mechanism 
62 (FIGS. 1 and 4). In order to facilitate this, each collocator car 56, 
on which a respective flat steel plate 24 is resting, advances by indexing 
forwards at the same precise intervals using an appropriate gear 
mechanism. 
The first stage, 64 (FIGS. 1, 4 and 8-10), of this stiffener installation 
mechanism utilizes a grinding machine 66 to remove an approximate 2-inch 
wide path of mill scale in the way of where each stiffener 60 will be 
installed. The grinding machine 66 comprises a fixed gantry 68 containing 
one or more power-rotated grinding wheels 70 mounted on a carriage 72 
running transverse to the line of travel of the collocator cars 56, which 
remove a path of mill scale approximately 2 inches wide in successive 
precise increments of approximately thirty-two inches as each collocator 
car 56 is indexed from position to position beneath it. The grinding wheel 
carriage 72 is electrically driven through a belt or chain mechanism 74 
across the gantry. A pneumatic cylinder 76 holds the grinding wheel 70 to 
the plate with proper force. 
The second stage, 78, of the stiffener installation mechanism, receives 
stiffeners from a kickplate stiffener collator 80, precisely fits and 
holds each stiffener 60 in its turn to a respective location, which has 
previously been cleaned of mill scale at 64, and tack welds each 
stiffener, using a tack welder 82, to the flat plate 24. The second stage 
78 includes a fixed gantry 84, located a precise distance of approximately 
thirty-two inches after the grinder gantry 68, running transverse to the 
lines of travel of the collocator cars and having for each line a guide 86 
into which a succession of identical kickplate steel flat-bar stiffeners 
60 is inserted one by one as the collocator cars are indexed from position 
to position beneath the fixed gantry 84. The fixed gantry 84 is equipped 
with a mechanical, hydraulic or pneumatic mechanism to lower guides and 
compress each successive stiffener 60 onto the respective flat plate 24, 
to enable the stiffener 60 to be tack-welded to the plate using 
gantry-mounted tack welders 82, and then to raise the guides to permit the 
collocator cars 56 to index to the next position. 
Each kickplate stiffener collator/inserter 80 is a device onto which a 
bundle of approximately eighteen identical kickplate stiffeners each 
approximately seven feet long, six inches deep and one-half inch thick is 
loaded as each fifty-foot long flat plate is processed. Individual 
kickplates 60 are oriented transverse to the line of flow of the 
respective collocator car and stacked side by side in the direction of the 
line of flow of the respective collocator car. The lead kickplate 60 is 
positioned alongside the opening to the respective guide of the kickplate 
positioning gantry 84 and inserted into the guide by use of a mechanical, 
electrical, pneumatic or hydraulic plunger as the respective collocator 
car 56 and flat plate 24 are indexed into position. Each remaining stack 
of kickplates 60 is indexed in the same direction as the line of travel of 
the respective collocator car. Each time each collocator car 56 is indexed 
thirty-two inches forward, the respective remaining stack of kickplates is 
indexed one-half inch using mechanical electrical, hydraulic or pneumatic 
plungers calibrated mechanically or electronically to the movement of the 
respective collocator car. Thus, as each flat plate 24 is indexed into the 
kickplate installation position, a kickplate 60 is always available to be 
inserted. 
Each collocator 80 is structured and functions similar to a transverse 
feeder on the head end of a magazine of a photographic slide projector. 
The third stage 90 of the stiffener installation mechanism final-welds each 
stiffener 60 in its turn. Alternately, the second and third stages may be 
combined, with tack welding being eliminated. In the preferred 
construction, the third stage comprises a fixed gantry 92 containing for 
each line a carriage-mounted double fillet, flux-core welding machine 94 
or substitute located a precise distance of approximately thirty-two 
inches after the kickplate installation gantry 78 and oriented transverse 
to the line of flow of the collocator car. The double fillet welding heads 
of the welding machine 96 are each equipped with a known seam tracker and 
appropriate positioning slides to compensate for slightly out-of-flatness 
of the respective plate 24 or minor misalignment of the kickplate 
stiffeners 60. The welding machines 96 perform finish welding of 
individual kickplate stiffeners 60 as the flat plates 24 with fitted 
kickplates 60 are indexed beneath it on the collocator cars 56, thereby 
providing stiffened flat panels 98. 
Fabricated curved panels 54 and stiffened flat panels 98 are then conveyed 
to a transporter car 100, which travels laterally on tracks 102, and then 
are lifted by hoists 104 from their horizontal positions to a vertical 
orientation and places it on a chain drive conveyor 106, so that each 
rests on one of its long edges. The chain drive conveyor 106 transports 
panels, through guides 108, into and out of a steel-shot abrasive cabinet 
110 (FIGS. 1 and 11) for removal of mill scale, weld slag, weld splatter 
and other foreign matter. 
In the shot-blast cabinet 110, recyclable steel abrasive shot or grit (not 
shown) is propelled automatically against all surfaces of curved and 
stiffened flat steel panels 54, 98 being transported through the cabinet 
by the chain drive conveyor 106 through guides 108 leading into and out of 
the cabinet. This removes all mill scale, weld slag, weld splatter and 
other foreign matter from the panels 54, 98. 
Fabricated flat panels requiring rework are conveyed by the transporter car 
100 to repair stations 112 (FIGS. 1 and 4) and, upon completion of 
repairs, are transferred to the abrasive cabinet 110, for surface 
preparation as described above. 
After being shot blasted, curved panels and stiffened flat panels are 
lifted off the exit conveyor guides 108 (FIGS. 1 and 11) of the abrasive 
cabinet 110 using plate clamps 114 hung from the twin monorails 116 
running transversely, and are immersed in a rinse tank 118 containing 
deionized water. 
The plate clamps on the twin monorails 116 transport the shot-blasted 
panels 54, 98 laterally through the five or more positions of the coating 
process of which the rinse tank 118 is the first. 
The rinse tank 118 contains deionized water and is large enough to 
accommodate one or more of the panels 54, 98 in a vertical position on one 
of its respective long edges during its rinse, after abrasive cleaning in 
the shot blast cabinet 110. A wash and pretreatment process is conducted 
in the rinse tank 118, plus sufficient tanks 120 for two or more 
subsequent chemical wash and pretreatment stages. 
After chemical wash and pretreatment, the next position of the coating line 
is a cathodic coating tank 122 containing a paint and water solution and 
large enough to accommodate one or more of the panels for receiving an 
initial coating, still in a vertical position. The tanks are provided with 
fenders (not shown) to protect the coating. 
The first coating tank preferably contains epoxy paint in water solution, 
and in it, each panel is cathodically coated, the coating process 
commercially available from PPG Coatings called Power Cron 640 conductive 
epoxy primer being presently preferred. 
The next position is a curing position 124 with infrared or other surface 
heaters (not shown) large enough to accommodate one or more of the panels 
after its initial coating in a vertical position, with fenders (not shown) 
to protect the coating. 
At this curing position 124, the first coating on the curved and flat 
panels is cured in the infrared-heating cabinet at approximately 
350.degree. F. 
The next position is a second cathodic coating tank 126 similar to the one 
at the second position. 
After curing at the first curing position 124, the curved and flat panels 
are immersed in the second coating tank 126 for a second cathodic coat of 
preferably the same type of epoxy paint, thereafter are removed to a 
second infrared heating cabinet 128 at a fifth position, for curing, and 
then stored vertically on their long sides in a storage rack 130 for 
inspection, with suitable fendering being provided to protect the coating. 
The coated panels are then inspected. Inspection criteria include handling 
damage to the coating, adhesion of the coating to the steel panel, 
thickness of the coating (normally 2.9 to 3.5 thousandths of an inch 
(nils.), and curing (hardening). 
Curved and stiffened flat panels with unacceptable coatings are conveyed 
back to the transporter car 100 for reprocessing through the entire 
surface preparation and coating processes. 
Curved and stiffened flat panels with acceptable coatings are lifted by a 
crane 131 (FIGS. 1 and 12), still in a vertical position on their 
respective end edges and placed either in buffer storage 132 or directly 
in the subassembly fixture 136 (as shown in FIG. 15). 
In the buffer storage 132 or fixture 136, the bottom edges of the curved 
and flat panels being stored or loaded into the fixture are aligned by 
landing them in guides 138. 
The guides 138 provided at the bottom of the fixture 136 are used for 
precisely positioning the bottom edges of the curved and stiffened flat 
panels as they are lowered by crane into the fixture 136, without using 
temporary attachments. 
In the fixture 136, buckling of the stiffened flat panels is prevented by 
manually activating mechanisms 140 (FIGS. 17 and 18). 
Each device 140, a plunger 142, which manually telescopes into and locks at 
144 in a fixture leg tube 146, holds a flat stiffened panel in position, 
to keep the panels from buckling without using temporary attachments. 
The top edges of the curved and flat panels are aligned by manually 
activating devices 148 (FIG. 19). 
The devices 148, hinged to one fixture leg at 150, notched at 152 to 
receive a plate edge and clamped to another fixture leg at 154 precisely 
position the tops of the curved and flat, stiffened panels, without using 
temporary attachments. 
Local random unfairnesses throughout the height of curved and flat panels 
disposed in the fixture 136 are removed by activating mechanisms 156 
(FIGS. 20 and 21). 
The devices 156 apply external pressure at intermediate positions on either 
face of respective curved or flat plate panels to bring unfair edge 
portions of those plates into precise welding position, without using 
temporary attachments. Devices 156 are hydraulically operated and are 
portable, and can be moved around the fixture 136 and secured to legs or 
leg braces, as needed, and hydraulically activated to forcefully engage 
and thus fair the panels as required. 
The hydraulically operated devices 158 (FIG. 22) are operated to apply 
external pressure at intermediate positions along edges of the curved 
plate panels to positively position the edges against the continuous 
copper backing bars (to be described). Devices 158 are hydraulically 
operated and are fixed to legs of the fixture 136. 
After all of the curved and flat panels have been brought into proper 
alignment in a given cell 160 of the fixture 136, mechanisms 162 (FIGS. 
16, 23 and 24, only respective ones of which are shown), located in each 
of the four interior corners of each cell 160, are activated to position 
the continuous copper backing bars 164, 166, 168, which are variously of 
the cross-sectional configurations shown in FIGS. (23, 24, 27) 26 and 28. 
The devices 158 position the curved steel plate 54 of each near 
intersection 170 between adjacent edges of curved and stiffened flat 
panels 54, 98. The backing bars 164, 166, 168 are positioned pneumatically 
in the valley formed by edge margins of two respective panels, by 
inflating a flexible hose 172, thus forcing the backing bar 164, 166, 168 
with positive force into damming relationship with the two panels near the 
intersection. When the electrogas welding (of FIG. 25) is completed, air 
pressure is released from each hose 172 and a spring mechanism 174 returns 
the backing bars 164, 166, 168 to their original retracted positions. 
After the curved and flat panels 54, 98 are brought into alignment and the 
interior copper backing bars 164, 166, 168 are in extended, damming 
position, weld joints, joining three or two panels simultaneously, with 
transverse cross-sections shown in FIGS. 26, 27 or 28, are welded, using a 
vertical electrogas welding machine (FIG. 25). As welding machine 176 
vertically rises, it is followed by a vacuum-blast nozzle, or needle gun 
(not shown), which removes exterior welding slag, welding splatter, burned 
paint, and foreign matter. The cleaned surface is then primed and finish 
painted by the weld machine operator, e.g., using a paint spray applicator 
(not shown) as the operator lowers the welding machine 176. 
After electrogas vertical welding is complete and exterior of the welds 
have been prime painted, the panel and backing bar alignment devices 140, 
148, 156, 158 and 162 are released. 
The painted subassembly 182 of panels and welds is then lifted from the 
fixture by a revolving crane 184 (FIGS. 1, 29, 30 and 40) and placed in a 
subassembly touch-up blast and paint facility 186 (FIGS. 1, 30 and 31). 
The main purpose of the touch-up blast and paint facility 186 is to repair 
interior cell coating damage caused by subassembly welding along interior 
edges of joints formed at 170 which form the intersection of curved panels 
98 and stiffened flat panels 54. The facility 186 includes a supporting 
structure 188 for the subassembly, with a built-in plenum for intake air 
to each interior cell 160 of the subassembly including means 190 for 
dehumidifying intake air and heating it, using steam coils or some other 
non-explosive means, and, in addition, a means of access 192 to the bottom 
of each cell 160 to service vacuum-blast and paint equipment 194. 
The facility 186 further includes a touch-up blast and paint elevator 
platform mechanism 196 having a cover 198 which extends over a single 
interior cell 160 at a time and is adequate for weather protection of that 
cell. 
The cover 198 is provided with an elevator platform 194 having four 
vacuum-blast nozzles 200 and four paint-spraying nozzles 202, one of each 
for each interior corner of a respective cell. The platform is suspended 
from the bottom of the cover at all four corners by a wire rope and pulley 
arrangement 196 which permits synchronous raising of each corner of the 
platform at speeds appropriate for both automatic vacuum blasting and 
automatic spray painting of corners of each individual subassembly cell 
where welding along the edges of the panels has damaged the coating. 
An explosion-proof exhaust fan 204 is mounted in the cover 198, with 
replaceable filters that are capable of entrapping the paint overspray 
which will be created by spray painting repaired areas of coating along 
vertical edges at intersection of curved and stiffened flat panels damaged 
by welding. 
The vacuum-blast machine 194 is mounted on the platform and has four 
nozzles 200 which are oriented toward the four interior corners of the 
subassembly cell to accomplish recyclable abrasive blasting of areas along 
panel edges where the coating has been damaged, in order to remove burned 
paint, weld slag, weld splatter and other foreign material as the platform 
is raised in an appropriate speed. 
Similarly, four appropriate spray painting nozzles 202 with appropriate 
supporting air and paint hoses are attached to the platform 206 and 
oriented toward the interior corners of the respective subassembly cell 
160 to enable spray painting of areas vacuum blasted above as the platform 
is raised at an appropriate speed. 
The spray paint used for spray painting of cell corners can be urethane 
type of any other type that is compatible with the cathodic epoxy coating 
utilized on the curved and flat panels. 
After coating is completed, the cover 198, complete with elevator platform 
194, vacuum blast nozzles 200 and paint spraying nozzles, is moved 
successively to blast- and paint-damaged areas of all cells. As elevator 
platform 194 is removed from a cell, the infrared heating tower 208 
depicted in FIG. 32 is lowered into the cell just vacated by the elevator 
platform, as depicted in FIG. 33, and energized for a period sufficient to 
cure the urethane paint just applied (approximately 30 to 90 minutes). 
This process is repeated successively until the urethane paint in all of 
the subassembly cells is cured. 
The subassembly 182, after this cleaning, painting and curing, is lifted 
from the touch-up blast and paint facility 186 using the revolving crane 
184 and relocated over the transverse bulkhead-erecting devices 210 and 
transverse bulkheads 212 shown in FIGS. 34 and 35. The transverse 
bulkheads 212 are raised by a spreader bar 214 with attached 
electromagnets 216 attached to the revolving crane 184. As the 
electromagnets 216 raise the transverse bulkheads 212, the erecting 
devices 210, also influenced by the electromagnets 216, follow, until the 
transverse bulkheads 212 are properly positioned in the subassembly cells 
182 (preferably approximately 12 inches from their bottoms). At this 
point, the transverse bulkhead-erecting devices 210 latch, as shown in 
FIG. 35, and hold the transverse bulkheads in the proper position. These 
cell transverse bulkhead units are then welded robotically, as depicted in 
FIG. 36, using robotic welder 218 or are welded manually. 
The subassembly 182, after installation and welding of cell transverse 
bulkhead units, is lifted from the subassembly transverse bulkhead 
installation facility 220 using a revolving crane 184 and is placed in the 
module assembly fixture and launching dock 222 shown in FIG. 40. 
FIG. 40 depicts the general arrangement of a preferred assembly area 
including subassembly fixtures 136 for both curved and straight 
subassemblies, touch-up blast and paint facility 186, subassembly 
transverse bulkhead installation facilities 220, module assembly fixture 
and launching dock 222 and revolving crane 184 with a radius sufficient to 
service all of these areas. 
Referring to FIGS. 41-48, a module is created from the several 
subassemblies by placing a double longitudinal vertical wall 224 in the 
module assembly fixture and launching dock 222 with the revolving crane 
184. Transverse bulkhead subassemblies 226 are then introduced into the 
module assembly fixture and launching dock 222 by barge 228, and placed in 
position alongside the double longitudinal vertical wall 224 by the 
revolving crane 184. 
The remaining subassemblies making up a module having a double bottom 230, 
double side walls 232 and double deck 234, are then placed around the 
double longitudinal vertical wall 224 and transverse bulkheads 226 (FIGS. 
37-39, 41 and 42) with the revolving crane 184. 
The curved subassemblies 236 are positioned very accurately in the module 
assembly fixture and launching dock 222 (FIGS. 43-48). This is 
accomplished by the curved subassembly alignment fixture 238 comprising a 
base 240, radial alignment stops 242, transverse alignment stop 244 and 
ram indices 246. The hydraulically operated ram indices 246 lock the 
curved subassemblies 236 against the stops 242, 244. The remaining 
subassemblies are then aligned to the curved subassemblies 236. 
Integral with the curved subassembly alignment fixtures 283 are four 
rotating kingposts 248, each with a fixed index 250 which is used for 
positively aligning the tops of the subassemblies 236. Each fixed index 
250, when rotated around kingpost 248 to a position shown in FIG. 48, 
serves as a positive stop against the upper part of the respective 
subassembly 236. Comealongs, with cables or other simple devices, can be 
used to position the subassembly 236 against the fixed index 250. Later, 
the fixed index 250 can be rotated away from the subassembly 236 around 
the kingpost 248 so that the completed module can be removed from the 
module assembly fixture and launching dock. 
The curved subassembly alignment fixtures 238 with rotating kingposts 248 
are portable so that different module sizes can be assembled in the module 
assembly fixture and launching dock 222. 
When alignment is complete, the subassemblies are joined together to form a 
module (FIGS. 49-51). An electrogas welding apparatus frame 252 is placed 
inside the subassembly cell at the place that the joints are to be made. 
Two electrogas welding units 254, one for each joint, are attached to the 
electrogas welding apparatus frame 252 by a vertical track 256. Each 
electrogas welding unit 254 operates independently on its own vertical 
track 256 attached to the electrogas welding apparatus frame 252. To keep 
the edges of this joint fair and true, a series of joint fairway clamps 
258 are attached to the subassembly curved plates 98 at the joints. The 
operator removes the joint fairing clamps 258 as the electrogas welding 
unit 254 progresses up the joint. 
After completion of welding, a module 260, ready for launching, has been 
assembled (FIG. 52). The module 260 is launched by opening valves in the 
launching dock gate 262 and, thus, allowing seawater to flood the module 
assembly fixture and launching dock 222 until the module 260 floats, using 
the transverse bulkheads 226 as a bottom. The launching dock gate 262 is 
then opened. 
The module 260 can then be removed from the module assembly fixture and 
launching dock 222 by means of tugboats 264 or other suitable means (FIG. 
53). Alternately, the module 260 will be constructed at ground level, 
translated to a launching sled upon final welding of longitudinal 
structure and launched by lowering a launching sled down inclined ways 
until the module floats off. 
Referring to FIG. 54, various internal piping and structural outfitting 
assemblies (foundations, ladders, etc.) are loaded into the open end of 
the module 260 floating in water on its bulkhead 226 alongside a shipyard 
pier 266 using a pier crane 268 and temporarily secured until the module 
260 can be subsequently turned to its upright position. 
Referring to FIGS. 55 through 62, the module 260 is translated from its 
position floating in water on its bulkhead 226, to its upright position 
high and dry on the outboard section 270 of a two-section floating drydock 
272. This is accomplished by installing a module-turning trunion 274 on 
the floating drydock outboard section 270 and sinking the floating drydock 
outboard section 270 by pumping river water into its ballast tanks 
sufficiently to permit the floating module 260 to be floated to a location 
over the module-turning trunion 274 (FIGS. 57 and 58). 
The double-bottom tanks of the module are then filled with approximately 
one-thousand tons of salt water to make the product of the weight and 
moment arm of the bottom of the module (to the left of the trunion in FIG. 
59) greater than the product of the weight and moment arm of the top of 
the module (to the right of the trunion in FIG. 59). 
Referring to FIGS. 59 through 62, the river water in the ballast tanks of 
the outboard section of the floating drydock 270 is pumped out 
progressively, causing the floating drydock section with its module 260 
load to rise out of the water concurrently, causing the module 260 to 
progressively turn on the axis of the module-turning trunion 274 as the 
water buoyancy supporting the module 260 is progressively eliminated. With 
all water buoyancy supporting the module 260 eliminated as the drydock 
section rises completely out of the water, the module 260 turns into its 
full upright position (FIG. 62). 
Referring to FIGS. 63 and 64, the module is then pulled from its inboard 
position on the outboard floating drydock section 270 to the outboard 
position on the inboard floating drydock section 276, utilizing a winch 
for pulling the module 260, and rollers on tracks for supporting the 
weight of the module 260. 
Referring to FIG. 65, a second module 278 is turned to an upright position 
using the same procedure as that utilized for turning the first module to 
an upright position. The second module 278, resting on the inboard end of 
the outboard section of the floating drydock 272, is joined by welding to 
the first module 260 resting on the outboard end of the inboard section of 
the floating drydock. 
Referring to FIG. 66, combined first and second modules are pulled 
approximately 50 feet using the same procedure as used in pulling the 
first module alone. Repeating the procedures depicted in FIGS. 65 and 66, 
another six modules are joined by welding to the first two modules (FIGS. 
66 through 71) joining a total of eight modules (and, thereby, forming 
one-half of a double-hull tanker midbody), and launched off both sections 
of the floating drydock as depicted in FIG. 72. A second half of a 
double-hull tanker midbody is manufactured and launched using the same 
procedure. 
Referring to FIG. 73, a tanker bow/stern vessel 280 (i.e., a vessel which 
is minus a midbody, but otherwise complete and functional including all 
machinery and accommodations) is acquired from a traditional shipyard and 
drydocked such that its stern 282 is completely on the inboard section of 
the two-section floating drydock 276, its bow 284 is completely on the 
outboard section of the two-section floating drydock 270 and the joint 
286, joining the bow 284 and stern 282, is precisely over the joint, 
joining the two sections of the floating drydock 272. 
Referring to FIGS. 74 through 80, the joint 286 between the bow 284 and 
stern 282 is cut using oxygen-acetylene burning torches. Then, the bow 284 
is undocked by submerging the outboard section of the floating drydock 270 
and one-half of the double-hull tanker midbody 288 is drydocked in place 
of the tanker bow 284 and joined to the tanker stern 282 by welding, 
thereby forming a double-hull tanker afterbody 290. This tanker afterbody 
290 is then launched into the river by submerging both sections of the 
floating drydock. 
Referring to FIGS. 81 through 84, the tanker bow 284 and the other half of 
the double-hull tanker midbody 292 are drydocked using both floating 
drydock sections 272 and joined by welding, forming a double-hull tanker 
forebody 294. This tanker forebody 294 is then launched into the river by 
submerging both sections of the floating drydock 272. 
Referring to FIGS. 85 through 88, the tanker forebody 294 is drydocked on 
one section of the floating drydock 270 and the tanker afterbody 290 on 
the other section of the floating drydock 276. The tanker forebody 294 is 
then pulled together with the tanker afterbody 290 and joined together by 
welding, thereby forming a complete double-hull tanker 296. This complete 
double-hull tanker is then launched by submerging both sections of the 
floating drydock 272. 
It should now be apparent that the vessel hull construction and method as 
described hereinabove, possesses each of the attributes set forth in the 
specification under the heading "Summary of the Invention" hereinbefore. 
Because it can be modified to some extent without departing from the 
principles thereof as they have been outlined and explained in this 
specification, the present invention should be understood as encompassing 
all such modifications as are within the spirit and scope of the following 
claims.