Title:
METHOD FOR FORMING A SHIP HULL SECTION
United States Patent 3797099
Abstract:
A method and structure for forming a portion of a ship hull using prefabricated hull sections. Plates having parallel stiffeners are moved relative to apertured cross-stiffeners which are then welded thereto to form a panel. Two such panels are welded together in back-to-back relation.
US Patent References:
Spot welded sheet material
Watter - December 1942 - 2304976
Joining methods
Watter - October 1961 - 3005086
Sandwich construction incorporating discrete metal core elements and method of fabrication thereof
Jones et al. - January 1963 - 3071216
Detachable tween deck construction
Blomberg et al. - November 1963 - 3109402
METHOD OF JOINING TOGETHER CORRUGATED-CORE PANELS
Molin et al. - October 1970 - 3534463
Spot welded sheet material
Watter - December 1942 - 2304976
Joining methods
Watter - October 1961 - 3005086
Sandwich construction incorporating discrete metal core elements and method of fabrication thereof
Jones et al. - January 1963 - 3071216
Detachable tween deck construction
Blomberg et al. - November 1963 - 3109402
METHOD OF JOINING TOGETHER CORRUGATED-CORE PANELS
Molin et al. - October 1970 - 3534463
Application Number:
05/215365
Publication Date:
03/19/1974
Filing Date:
01/04/1972
View Patent Images:
Export Citation:
Assignee:
General Dynamics Corporation (St. Louis, MO)
Primary Class:
Other Classes:
228/189, 114/77R, 114/74A, 114/74T
International Classes:
B23K9/00; B63B9/06; B63B9/00; B23K31/00
Field of Search:
29/471.1,471.3,472.1,475,482,483 114/72,73,74A,74T,77,78
US Patent References:
Primary Examiner:
Lazarus, Richard B.
Attorney, Agent or Firm:
Fitch, Even, Tabin & Luedeka
Claims:
What is claimed is
1. A method of forming a section of a ship hull comprising
2. A method in accordance with claim 1 wherein a plurality of metal bars are affixed to the stiffening webs in spaced relation along the length of each web, which bars project past the other longitudinal edge of the web in a direction transverse thereto and are effective to guide the webs of different panels into edge-to-edge aligned abutting relation when two panels are moved into back-to-back relation to each other.
3. A method in accordance with claim 2 wherein the projecting bars are disposed on both surfaces of the webs and have angled projecting ends which contact and guide the other longitudinal edge of the stiffening webs of the other panel.
4. A method of forming a section of a ship hull comprising
5. A method of forming a section of a ship hull comprising
6. A method in accordance with claim 5 wherein a plurality of metal bars are affixed to the cross-stiffening webs in spaced relation along the length of each web, which bars project past the other longitudinal edge of the web in a direction transverse thereto and are effective to guide the webs of different panels into edge-to-edge aligned abutting relation when two panels are moved into back-to-back relation to each other.
7. A method in accordance with claim 6 wherein the projecting bars are disposed on both surfaces of the webs and have angled projecting ends which contact and guide the other longitudinal edge of the cross-stiffening webs of the other panel.
1. A method of forming a section of a ship hull comprising
2. A method in accordance with claim 1 wherein a plurality of metal bars are affixed to the stiffening webs in spaced relation along the length of each web, which bars project past the other longitudinal edge of the web in a direction transverse thereto and are effective to guide the webs of different panels into edge-to-edge aligned abutting relation when two panels are moved into back-to-back relation to each other.
3. A method in accordance with claim 2 wherein the projecting bars are disposed on both surfaces of the webs and have angled projecting ends which contact and guide the other longitudinal edge of the stiffening webs of the other panel.
4. A method of forming a section of a ship hull comprising
5. A method of forming a section of a ship hull comprising
6. A method in accordance with claim 5 wherein a plurality of metal bars are affixed to the cross-stiffening webs in spaced relation along the length of each web, which bars project past the other longitudinal edge of the web in a direction transverse thereto and are effective to guide the webs of different panels into edge-to-edge aligned abutting relation when two panels are moved into back-to-back relation to each other.
7. A method in accordance with claim 6 wherein the projecting bars are disposed on both surfaces of the webs and have angled projecting ends which contact and guide the other longitudinal edge of the cross-stiffening webs of the other panel.
Description:
The present invention relates to the building of ship hulls and, more particularly, to the building of ship hulls from prefabricated sections.
A conventional method of building the hull of a ship is to employ a way at least as large as the hull being constructed and to build the entire hull as a unit by first forming a suitable framework on the way and then welding plates of steel to the framework. With this method, essentially all of the skilled labor required is performed on site using equipment which can be easily transported to and from the way and moved from one location to another within the way. This method thus does not lend itself well to the use of specialized highly efficient equipment, particularly welding and other fabricating equipment which, by virtue of its size and nature, is not readily transportable.
A departure from this historical method of building hulls is shown in U.S. Pat. No. 3,447,503. In accordance with the teachings of that patent, one section of th length of the hull is constructed in the way. A number of modules, each constituting a longitudinal segment of the hull, are then successively built in the way and, as each is completed, it is attached to one end of the partially completed hull. The hull is incrementally advanced from the way into the water as each module is added until the hull has been completed.
In accordance with the present invention, sections of the bottom wall and side walls of the hull are prefabricated in an area remote from the way and transported to the way in a form suitable for immediate incorporation into the hull. The form of the wall sections is such as to permit the most efficient fabrication techniques and equipment with a minimum waste of material.
Accordingly, it is the primary object of the present invention to provide an improved method for forming a ship hull.
It is a further object of this invention to provide a method for forming a prefabricated hull section suitable for use in an improved method for forming a ship hull.
These and other objects of the invention are more particularly set forth in the following detailed description and in the accompanying drawings, of which:
FIG. 1 is a perspective view of a ship erection site showing a ship hull being built in accordance with various features of the present invention;
FIG. 2 is a perspective view of a steel plate showing by means of an outline thereon one method of cutting the plate to form a pair of structural elements employed in one embodiment of the present invention;
FIGS. 3 and 4 are fragmentary perspective views of two of the steps of manufacture used in forming a prefabricated hull section to be used in building a ship hull as shown in FIG. 1; and
FIG. 5 is a fragmentary perspective view of a prefabricated hull section formed in accordance with the method shown in FIGS. 2 and 3.
The present invention has application in the building of ship hulls of various design. However, it will hereinafter be described by way of example and not limitation as it might be employed in the construction of a wide flat bottomed ship hull which is adapted to contain and support large metal spheres (not shown) for transporting liquified natural gas.
It may be assumed that the completed hull includes a bow, a stern, and a midbody. It is contemplated that the construction area includes three elongated wet basins arranged side by side, i.e., a center basin flanked on either side by an outer basin, and that at least one way, remote from the wet basins, also be provided. The bow is assembled in one of the outer wet basins while the stern is being assembled in the other outer basin; the midbody is assembled on the way. When the stern is completed, it is floated into the center basin and the midbody is then launched and also floated into the center basin to be joined to the stern. Large sections of the bow are then lifted from the outer basin and placed in the center basin for attachment to the midbody.
While various features of the invention can be employed in the assembly of the stern and bow, or portions thereof, the invention finds particular application in the erection of the midbody and will thus be described in connection with that portion of the hull.
Referring to FIG. 1, there is shown a way having disposed therein a partially completed midbody 11 which includes an inner bottom 13, bilge sections 15, lower wing walls 17, and upper wing walls 19. The midbody may also include various transverse bulkheads. Such bulkheads are not shown in the drawings.
It is contemplated that the bilge sections 15 be built as a unit remote from the way and transported to the way for installation. In accordance with the present invention, the innerbottom 13 and the lower wing walls 17 are formed as individual sections at a remote fabrication area, with each section comprising a pair of mating panels 21. In the case of the innerbottom sections, upper and lower panels 21 are transported to the way and joined to each other, as well as to previously formed innerbottom sections, in the way. Prefabricated bilge sections 15 are then transported to the way and attached to the innerbottom sections, as well as to adjacent bilge sections previously installed. In the case of the wing walls, each lower wing wall section is formed as a pair of inner and outer mating panels 21 which are transported individually to an area adjacent the way where they are joined to each other and then attached to an upper wing wall section previously fabricated. The combined upper and lower wing wall sections are then transferred to the way and attached to the bilge sections as well as to adjacent wing wall sections previously installed.
The following discussion will be directed to the fabrication of the panels 21 which may, for example, form one-half of an innerbottom section or one-half of a lower wing wall section. The joinder of such panels to form a section will also be described.
More specifically, and with reference to FIGS. 1, 3 and 4, each panel 21 is formed of a plurality of elongated steel plates 23 reinforced by elongated metal stiffeners 25 which are spaced laterally from one another and which extend longitudinally of the plates but terminate in spaced relation to the ends thereof. The edge of the plate 23 that is parallel to the elongated stiffeners is referred to as the longitudinal edge of the plate. In the illustrated embodiment, each plate 23 is reinforced by three such stiffeners, each of which is of L-shaped cross section and includes a web 27 and a flange 29. In a preferred embodiment, the stiffeners are formed by first cutting flanges 29 from plate stock identical in size to that of the plates 23. The flanges are then welded on edge to additional plates also identical in size to the plates 23 with a spacing between the flanges closely approximating the desired depth of the webs 27. The plate to which the flanges are attached is then cut adjacent each flange to form the webs 27 and provided the desired stiffeners, each having an L-shaped cross-sectional configuration. The stiffeners 25 are then trimmed at their ends, and three such stiffeners are attached to one surface of a plate 23 by welding the edges of the webs 27 opposite the flanges 29 to the plates 23 along the edges of the webs with the webs generally normal to the plate surface and with the flanges generally parallel to the plate surface. By virtue of this method, the plates 23, as well as the stiffeners 25, are all formed of the same stock, thereby minimizing the types and sizes of material which must be inventoried.
In one embodiment, five such stiffened plates are then arranged in an abutting side-by-side relationship and joined along their abutting longitudinal edges by welding along such edges adjacent the surface of the plates to which the stiffeners 25 are attached as well as adjacent the opposite surface. Thus, after welding the plates together adjacent one surface, the assembly of joined plates is turned for welding on the opposite side. In one preferred embodiment, each of the plates 23 measures approximately 71/2 feet in width and 42 feet in length. In forming a lower wing wall section 17 in which five stiffened plates 23 are joined, the resulting wing wall section has a longitudinal dimension of approximately 42 feet and a vertical dimension of approximately 37 feet.
Each assembly of stiffened plates 25 is cross stiffened by three webs 31 which are spaced along the length of the panel assembly and which extend transversely of the plates 23 and stiffeners 25. In a preferred embodiment, a pair of webs 31 is cut from a single plate 33 (FIG. 2) having a size identical to that of the plates 23. This is accomplished by cutting the plate 33 longitudinally, not along a straight line parallel to the longitudinal side edges of the plate, but along an irregular path shown in FIG. 2. The cut edge of the web is thus provided with slots 35 separated by plate portions 37 (FIG. 3), while the opposite edges 38 of the web is straight. When two of the webs are disposed with the edges of their plate portions 37 in abutting relation, as shown in FIG. 5, the slots 35 combine to form lightener openings 39. By virtue of the manner in which the webs are formed from the plate 33, a single plate measuring 71/2 feet in width will provide a pair of webs 31 which, when in abutting relation as shown in FIG. 5, have a combined width of approximately 8 feet.
The webs 31 are intended to be welded along their straight edge 38 to the plates 23 and stiffeners 25. Accordingly, each web is cut out along its straight edge to provide apertures 41 through which the plate stiffeners may pass and within which the plate stiffeners may be accommodated. These apertures are configured so as to closely approximate the configuration of the plate stiffeners.
Prior to their attachment to the stiffened panel assemblies, the webs are themselves stiffened by means of bars 43 which are welded to each of the opposite sides of the web transversely of the straight edge of the web. In the illustrated embodiment, a web stiffener or bar 43 is disposed midway to each plate portion 37 intermediate the slots 35, with the bars of adjacent plate portions being located on opposite sides of the web. Each bar extends from the inner edge of the aperture 41 and projects approximately six inches past the edge of its plate portion 37. The projecting end of each bar is canted or inclined, as at 45, to provide a camming surface, the function of which will be apparent shortly.
The stiffened webs are assembled on the stiffened plate assemblies to form the panels 21 by supporting the plate assemblies in a stationary horizontal position and by sliding the webs horizontally longitudinally of the plates 23, as shown in FIG. 3. Alternatively, the webs may be supported in a stationary horizontal position, as by means of a scaffold or platform, and the stiffened plate assemblies moved vertically relative to the webs, as by lowering them with a crane. In either case, during such relative movement, the plate stiffeners occupy the apertures 41. When the webs have been properly positioned, they are welded to the plates and stiffeners. In previous constructions in which L-shaped stiffeners were used, the webs were moved into position in a direction normal to the plates. Thus, the webs were provided with slots having the width of the flanges of the stiffeners and having the depth of the webs of te stiffeners. After the web was in place, the slot was partially filled by small plates or collars which were welded to the webs and stiffeners and which spanned the gap between the webs and stiffeners. In accordance with the present method in which the apertures 41 of the web have a configuration which closely approximates that of the stiffeners, the need for such collars is eliminated, resulting in considerable savings in time and labor.
With the webs 31 welded in place, the panel 21 is complete except for blast cleaning and painting, which is normally done at the fabrication site. If the panel is to form part of an innerbottom section, it is transported directly to the way and combined in the way with a second panel. If it is to form part of a lower wing wall 17, it is tranported to a location adjacent the way and combined with a like panel and with an upper wing wall section before being attached to a bilge section 15 in the way.
The mating of two of the panels 21 to form a double walled hull section is shown in FIGS. 4 and 5. In these figures, the panels 21 are shown upright but, in practice, one of the panels will normally be supported horizontally and the remaining panel will be lowered into place from above.
The ultimate position of the mated panels is shown in FIG. 5 where it will be seen that the cut edges of the webs 31 of opposite panels abut, with the slots 35 aligned to form lightener openings 39. The panels are guided into such position with the aid of the web stiffeners 43 which project past the cut edges of the webs and which include the canted edges 45. As the upper panel is lowered into the mating position, the canted edges 45 serve to cam it into the desired position. Since the web stiffeners are provided on each side of each web, each web is ultimately captured between the web stiffeners of the opposite panel and precise positioning of the webs relative to each other is assured. The panels 21 are therefore self-aligning in the longitudinal direction and the need for special aligning is eliminated. The mated panels are then welded together along the abutting edges of the plate portions 37 and along the web stiffeners. The weld which extends longitudinally of the webs is therefore interrupted by the lightener openings 39 and is not continuous, minimizing any tendency for the webs to warp.
The present invention thus permits the use of highly efficient prefabricated panels which can be easily joined to form double walled hull sections, particularly sections employed in erecting the midbody of the hull. The panels lend themselves to the use of specialized fabricating equipment which cannot be conveniently employed in a shipbuilding way, and their use eliminates a great deal of fabricating and labor in the way itself.
While the invention has been shown and described with respect to one specific embodiment thereof, it should be apparent that various modifications are possible without departing from the scope of the invention.
Various features of the invention are set forth in the following claims.
A conventional method of building the hull of a ship is to employ a way at least as large as the hull being constructed and to build the entire hull as a unit by first forming a suitable framework on the way and then welding plates of steel to the framework. With this method, essentially all of the skilled labor required is performed on site using equipment which can be easily transported to and from the way and moved from one location to another within the way. This method thus does not lend itself well to the use of specialized highly efficient equipment, particularly welding and other fabricating equipment which, by virtue of its size and nature, is not readily transportable.
A departure from this historical method of building hulls is shown in U.S. Pat. No. 3,447,503. In accordance with the teachings of that patent, one section of th length of the hull is constructed in the way. A number of modules, each constituting a longitudinal segment of the hull, are then successively built in the way and, as each is completed, it is attached to one end of the partially completed hull. The hull is incrementally advanced from the way into the water as each module is added until the hull has been completed.
In accordance with the present invention, sections of the bottom wall and side walls of the hull are prefabricated in an area remote from the way and transported to the way in a form suitable for immediate incorporation into the hull. The form of the wall sections is such as to permit the most efficient fabrication techniques and equipment with a minimum waste of material.
Accordingly, it is the primary object of the present invention to provide an improved method for forming a ship hull.
It is a further object of this invention to provide a method for forming a prefabricated hull section suitable for use in an improved method for forming a ship hull.
These and other objects of the invention are more particularly set forth in the following detailed description and in the accompanying drawings, of which:
FIG. 1 is a perspective view of a ship erection site showing a ship hull being built in accordance with various features of the present invention;
FIG. 2 is a perspective view of a steel plate showing by means of an outline thereon one method of cutting the plate to form a pair of structural elements employed in one embodiment of the present invention;
FIGS. 3 and 4 are fragmentary perspective views of two of the steps of manufacture used in forming a prefabricated hull section to be used in building a ship hull as shown in FIG. 1; and
FIG. 5 is a fragmentary perspective view of a prefabricated hull section formed in accordance with the method shown in FIGS. 2 and 3.
The present invention has application in the building of ship hulls of various design. However, it will hereinafter be described by way of example and not limitation as it might be employed in the construction of a wide flat bottomed ship hull which is adapted to contain and support large metal spheres (not shown) for transporting liquified natural gas.
It may be assumed that the completed hull includes a bow, a stern, and a midbody. It is contemplated that the construction area includes three elongated wet basins arranged side by side, i.e., a center basin flanked on either side by an outer basin, and that at least one way, remote from the wet basins, also be provided. The bow is assembled in one of the outer wet basins while the stern is being assembled in the other outer basin; the midbody is assembled on the way. When the stern is completed, it is floated into the center basin and the midbody is then launched and also floated into the center basin to be joined to the stern. Large sections of the bow are then lifted from the outer basin and placed in the center basin for attachment to the midbody.
While various features of the invention can be employed in the assembly of the stern and bow, or portions thereof, the invention finds particular application in the erection of the midbody and will thus be described in connection with that portion of the hull.
Referring to FIG. 1, there is shown a way having disposed therein a partially completed midbody 11 which includes an inner bottom 13, bilge sections 15, lower wing walls 17, and upper wing walls 19. The midbody may also include various transverse bulkheads. Such bulkheads are not shown in the drawings.
It is contemplated that the bilge sections 15 be built as a unit remote from the way and transported to the way for installation. In accordance with the present invention, the innerbottom 13 and the lower wing walls 17 are formed as individual sections at a remote fabrication area, with each section comprising a pair of mating panels 21. In the case of the innerbottom sections, upper and lower panels 21 are transported to the way and joined to each other, as well as to previously formed innerbottom sections, in the way. Prefabricated bilge sections 15 are then transported to the way and attached to the innerbottom sections, as well as to adjacent bilge sections previously installed. In the case of the wing walls, each lower wing wall section is formed as a pair of inner and outer mating panels 21 which are transported individually to an area adjacent the way where they are joined to each other and then attached to an upper wing wall section previously fabricated. The combined upper and lower wing wall sections are then transferred to the way and attached to the bilge sections as well as to adjacent wing wall sections previously installed.
The following discussion will be directed to the fabrication of the panels 21 which may, for example, form one-half of an innerbottom section or one-half of a lower wing wall section. The joinder of such panels to form a section will also be described.
More specifically, and with reference to FIGS. 1, 3 and 4, each panel 21 is formed of a plurality of elongated steel plates 23 reinforced by elongated metal stiffeners 25 which are spaced laterally from one another and which extend longitudinally of the plates but terminate in spaced relation to the ends thereof. The edge of the plate 23 that is parallel to the elongated stiffeners is referred to as the longitudinal edge of the plate. In the illustrated embodiment, each plate 23 is reinforced by three such stiffeners, each of which is of L-shaped cross section and includes a web 27 and a flange 29. In a preferred embodiment, the stiffeners are formed by first cutting flanges 29 from plate stock identical in size to that of the plates 23. The flanges are then welded on edge to additional plates also identical in size to the plates 23 with a spacing between the flanges closely approximating the desired depth of the webs 27. The plate to which the flanges are attached is then cut adjacent each flange to form the webs 27 and provided the desired stiffeners, each having an L-shaped cross-sectional configuration. The stiffeners 25 are then trimmed at their ends, and three such stiffeners are attached to one surface of a plate 23 by welding the edges of the webs 27 opposite the flanges 29 to the plates 23 along the edges of the webs with the webs generally normal to the plate surface and with the flanges generally parallel to the plate surface. By virtue of this method, the plates 23, as well as the stiffeners 25, are all formed of the same stock, thereby minimizing the types and sizes of material which must be inventoried.
In one embodiment, five such stiffened plates are then arranged in an abutting side-by-side relationship and joined along their abutting longitudinal edges by welding along such edges adjacent the surface of the plates to which the stiffeners 25 are attached as well as adjacent the opposite surface. Thus, after welding the plates together adjacent one surface, the assembly of joined plates is turned for welding on the opposite side. In one preferred embodiment, each of the plates 23 measures approximately 71/2 feet in width and 42 feet in length. In forming a lower wing wall section 17 in which five stiffened plates 23 are joined, the resulting wing wall section has a longitudinal dimension of approximately 42 feet and a vertical dimension of approximately 37 feet.
Each assembly of stiffened plates 25 is cross stiffened by three webs 31 which are spaced along the length of the panel assembly and which extend transversely of the plates 23 and stiffeners 25. In a preferred embodiment, a pair of webs 31 is cut from a single plate 33 (FIG. 2) having a size identical to that of the plates 23. This is accomplished by cutting the plate 33 longitudinally, not along a straight line parallel to the longitudinal side edges of the plate, but along an irregular path shown in FIG. 2. The cut edge of the web is thus provided with slots 35 separated by plate portions 37 (FIG. 3), while the opposite edges 38 of the web is straight. When two of the webs are disposed with the edges of their plate portions 37 in abutting relation, as shown in FIG. 5, the slots 35 combine to form lightener openings 39. By virtue of the manner in which the webs are formed from the plate 33, a single plate measuring 71/2 feet in width will provide a pair of webs 31 which, when in abutting relation as shown in FIG. 5, have a combined width of approximately 8 feet.
The webs 31 are intended to be welded along their straight edge 38 to the plates 23 and stiffeners 25. Accordingly, each web is cut out along its straight edge to provide apertures 41 through which the plate stiffeners may pass and within which the plate stiffeners may be accommodated. These apertures are configured so as to closely approximate the configuration of the plate stiffeners.
Prior to their attachment to the stiffened panel assemblies, the webs are themselves stiffened by means of bars 43 which are welded to each of the opposite sides of the web transversely of the straight edge of the web. In the illustrated embodiment, a web stiffener or bar 43 is disposed midway to each plate portion 37 intermediate the slots 35, with the bars of adjacent plate portions being located on opposite sides of the web. Each bar extends from the inner edge of the aperture 41 and projects approximately six inches past the edge of its plate portion 37. The projecting end of each bar is canted or inclined, as at 45, to provide a camming surface, the function of which will be apparent shortly.
The stiffened webs are assembled on the stiffened plate assemblies to form the panels 21 by supporting the plate assemblies in a stationary horizontal position and by sliding the webs horizontally longitudinally of the plates 23, as shown in FIG. 3. Alternatively, the webs may be supported in a stationary horizontal position, as by means of a scaffold or platform, and the stiffened plate assemblies moved vertically relative to the webs, as by lowering them with a crane. In either case, during such relative movement, the plate stiffeners occupy the apertures 41. When the webs have been properly positioned, they are welded to the plates and stiffeners. In previous constructions in which L-shaped stiffeners were used, the webs were moved into position in a direction normal to the plates. Thus, the webs were provided with slots having the width of the flanges of the stiffeners and having the depth of the webs of te stiffeners. After the web was in place, the slot was partially filled by small plates or collars which were welded to the webs and stiffeners and which spanned the gap between the webs and stiffeners. In accordance with the present method in which the apertures 41 of the web have a configuration which closely approximates that of the stiffeners, the need for such collars is eliminated, resulting in considerable savings in time and labor.
With the webs 31 welded in place, the panel 21 is complete except for blast cleaning and painting, which is normally done at the fabrication site. If the panel is to form part of an innerbottom section, it is transported directly to the way and combined in the way with a second panel. If it is to form part of a lower wing wall 17, it is tranported to a location adjacent the way and combined with a like panel and with an upper wing wall section before being attached to a bilge section 15 in the way.
The mating of two of the panels 21 to form a double walled hull section is shown in FIGS. 4 and 5. In these figures, the panels 21 are shown upright but, in practice, one of the panels will normally be supported horizontally and the remaining panel will be lowered into place from above.
The ultimate position of the mated panels is shown in FIG. 5 where it will be seen that the cut edges of the webs 31 of opposite panels abut, with the slots 35 aligned to form lightener openings 39. The panels are guided into such position with the aid of the web stiffeners 43 which project past the cut edges of the webs and which include the canted edges 45. As the upper panel is lowered into the mating position, the canted edges 45 serve to cam it into the desired position. Since the web stiffeners are provided on each side of each web, each web is ultimately captured between the web stiffeners of the opposite panel and precise positioning of the webs relative to each other is assured. The panels 21 are therefore self-aligning in the longitudinal direction and the need for special aligning is eliminated. The mated panels are then welded together along the abutting edges of the plate portions 37 and along the web stiffeners. The weld which extends longitudinally of the webs is therefore interrupted by the lightener openings 39 and is not continuous, minimizing any tendency for the webs to warp.
The present invention thus permits the use of highly efficient prefabricated panels which can be easily joined to form double walled hull sections, particularly sections employed in erecting the midbody of the hull. The panels lend themselves to the use of specialized fabricating equipment which cannot be conveniently employed in a shipbuilding way, and their use eliminates a great deal of fabricating and labor in the way itself.
While the invention has been shown and described with respect to one specific embodiment thereof, it should be apparent that various modifications are possible without departing from the scope of the invention.
Various features of the invention are set forth in the following claims.