US3164894A

US3164894A - Method of making boat hulls

Info

Publication number: US3164894A
Application number: US13578A
Authority: US
Inventors: Wallace C Johnson; Joseph A Crum
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1960-03-08
Filing date: 1960-03-08
Publication date: 1965-01-12
Anticipated expiration: 1982-01-12

Description

Jan. 12, 1965 w. c. JOHNSON ETAL 3,164,394

METHOD OF MAKING BOAT HULLS Filed March 8, 1960 4 Sheets-Sheet 1 FIC5.4

INVENTORS.

WALLACE C.JOHNSON BY JOSEPH A.CRUM

/ I l l 1965 w. c. JOHNSON ETAL 3,164,894

METHOD OF MAKING BOAT HULLS 4 Sheets-Sheet 2 Filed March 8, 1960 INVENTORS.

WALLACE C.JOHNSON By JOSEPH A. CRUM Jan. 12, 1965 w. c. JOHNSON ETAL 3,164,894

METHOD OF MAKING BOAT HULLS Filed March 8, 1960 4 Sheets-Sheet 3 FIG. IO

52 f 34 2 l i! \l 4 FIG. 1|

INVENTORS.

WALLACE C. JOHNSON BY JOSEP A, cum

Jan. 12, 1965 w. c. JOHNSON ETAL 3,164,894

METHOD OF MAKING BOAT HULLS Filed March 8, 1960 4 Sheets-Sheet 4 WALLACE C.JOHNSON y JOSEPH A. CRUM INVENTORS.

United States Patent Ofifice 3,164,894 Patented Jan. 12, 1965 3,164,894 METHOD OF MAKING BOAT HULLS Wallace C. Johnson, Hamden, Conn, and Joseph A.

Crum, Pacific Palisades, Califi, assignors to Olin Mathieson Chemical Corporation, East Alton, 11]., a

corporation of Virginia Filed Mar. 8, 1960, Ser. No. 13,578 6 Claims. (Cl. 29-412) This invention relates to improvement in boat construction and more particularly to the fabrication of a plurality of seamless boat hulls from a flat metal sheet internally laminated in accordance configuration.

In conventional methods of construction, a metal boat hull is fabricated from a plurality of complementary portions which are suitably fastened together by means such as riveting, welding, and the like. However, such construction entails the assembly of a plurality of portions which require a large amount of hand work and care to first form and then make water tight joints between the portions, and in addition employ excess material in the form of welds and/ or rivets which appreciably increase the weight and cost of the completed structure.

It is accordingly an object of this invention to provide a novel means for constructing boat hulls eliminating disadvantages of the prior art.

It is another object of this invention to provide a novel method for fabricating metalboat hulls by conventional pressure welding techniques. 7

It is still another object of this invention to provide a novel method for fabricating boat hulls from a plurality of component sheets pressure welded by conventional techniques into a single sheet internally laminated in a predetermined configuration.

A further object of this invention is to provide a novel method for fabricating a seamless double-walled boat hull from a single sheet of metal internally laminated in a predetermined configuration.

A still further object of this invention is to provide a novel boat hull which, with the exception of a transom provided at its stern end, is substantially of seamless construction.

It is also an object of this invention to provide a double-walled boat hull integrally reinforced with cross-members or ribs which, with the exception of a transom provided at its stem end, is substantially of seamless construction.

Other objects and advantages will become more apparent from the following description and drawings in which:

FIGURE 1 is a perspective view of an assembly of components in accordance with one embodiment of this invention; a

FIGURE 2 is a perspective view illustrating an assembly of FIGURE 1 in pressure welded and elongated form;-

FIGURE 3 is a plan view showing the blank of FIG- URE 2 in trimmed and expanded or inflated form;

FIGURE 4 is an edge view of the inflated blank of FIGURE 3 illustrating a further step in accordance with the aforesaid embodiment of this invention;

FIGURE 5 is a perspective view of an ultimate boat hull obtained in'accordance with the aforesaid embodiment of this invention;

FIGURE 6 is a plan view of another form of blank employed for obtaining the aforesaid embodiment of this invention;

FIGURE 7 is a perspective view illustrating an assembly of components that may be employed in obtaining another embodiment of this invention;

FIGURES 8 to 11 illustrate various stages in detail for obtaining another embodiment of this invention from the assembly of components illustrated in FIGURE 7;

to a predetermined FIGURE 12 is a perspective view illustrating a doublewalled boat hull obtained in accordance with the last said embodiment of this invention; and

FIGURE 13 is an enlarged partial view in perspectiv illustrating details of construction of the double-walled boat hull illustrated in FIGURE 12.

Referring to the drawings, a pair of superposed metal sheets 1 and 2, such as ASM aluminum alloy 1100, have interposed between them an elongated oval pattern 3 of stop-weld extending to a lateral edge of the sheets by means of a band 4 of stop-weld material communicating with pattern 3. More particularly, the welding surfaces of the superposed sheets 1 and 2 are first given a preliminary cleaning and Wire brushing or etching followed by coating on one surface of a sheet such as 5, of sheet 2,

the oval-shaped pattern 3 of stop-weld material, such as graphite in water glass. Sheet 1 is then superimposed on sheet 2 over the stop-weld material of pattern 3 and band 4, and the sheets then secured, as by spot-welding or tack-welding at the corners to prevent relative movement between the sheets during subsequent heating and pressure welding operations.

The oval-shaped pattern of stop-weld material 3, as applied, is foreshortened, and each quadrant of the elongated oval pattern defines a foreshortened configuration of the desired elevational profile in a boat hull. The term elongated oval for purposes of this application embraces not only true foreshortened oval patterns, but also oval patterns which are bi-laterally divided and interconnected by rectangular portions having parallel edges or sides extending across the boat hull from both ends of the divided oval. The degree to which the oval pattern is foreshortened will necessarily be dependent upon the degree of elongation or reduction desired or required for subsequent pressure Welding sheets 1 and 2 together and reducing the welded structure to desired finish gauge. As will be also understood, the thickness of the sheets 1 and 2 will also be dependent not only on the total amount of reduction desired or required but also on the types of metal employed and on the initial dimension of the superposed assembly of sheets to be elongated during the operation of welding and reduction to gauge.

The degree to which pattern 3 is foreshortened and:

the thickness of sheets 1 and 2 will be further dependent on the desired lengths and widths of the individual boat hulls obtained by this invention. For example, in order to obtain the conventional thicknesses of aluminum boat walls, which in riveted boats are of the order of 0.050 inch, from a 1 inch thick pack formed from two superposed sheets each /2 inch in thickness, about inches wide and 36 inches long. about a 60% reduction between mill rolls to effect pressure-welding of the sheets and then further reduced in a number of cold passes to an ultimate thickness of 0.100 inch and a length of 360 inches. This ultimate 0.100 inch thick pack will have the portions of the component sheets opposite the stop-weld material of 0.050 inch thickness. These portions of the component sheets opposite and encasing the stop-weld material form the bottom and also the sides of the boat hull. Thus, as can be seen, thicker sheets may also be employed if greater lengths are desired in a final combined gauge of 0.100 inch and in-each instance the degree to which the oval pattern 3 of stop-weld material will be fore-shortened will be governed by the total amount of elongation or reduction of the two component sheets between which the hull pattern is interposed. Subsequent to securing the component sheets 1 and 2 together against relative movement,

invention may be pressure-welded are set forth in the The pack may be then given well known process disclosed in the patent to Grenell, US. No. 2,690,002, granted on September 28, 1954.

In accordance with the conventional practice, the secured assembly of component sheets 1 and 2 is heated in a suitable furnace to pressure-welding temperatures of about 1000 F. and rolled at the elevated temperature between a pair of wide mill rolls to effect a total reduction of about 65% wherein all of the adjacent areas 6, of the component sheets, not separated by the stop-weld material, are pressure-welded to each other resulting in a complete erasure of the interfaces between the sheets by interdispersion of the grains between adjacent surfaces. The resultant seamless juncture is usually characterized by tensile strength equal to that of other seamless regions of the structure, and the non-fluid, solid-phase, pressureweld cannot be detected from the base metal. The direction of rolling will generally be only in the direction in which the elongated oval pattern 3 of FIGURE 1 is foreshortened. However, where the dimension transverse to the direction of foreshortening is desired to be increased so as to make the hull wider, the superposed sheets may also be first cross rolled in the transverse direction. As will be understood, the amount of reduction required to effect pressure-welding will vary with the particular metal of the component sheets and the physical properties thereof Generally, a reduction of the order of about 35% will accomplish pressure-welding of adjacent surfaces not separated by stop-weld material, however, it will be understood that lower or higher percent reduction may be suflicient or required with different metals and/or different temperatures to which the metal is heated prior to pressure-welding.

By reference to the resultant structure of FIGURE 2, it can be seen that portions of the sheets are pressurewelded together at 6, whereas adjacent surfaces separated by the stop-weld material result in an internally unjoined portion or lamination 7 between portions of the sheet opposite and adjacent the stop-weld material comprising the laminae opposite this lamination or unjoined area. After the pressure-welding operation, the pressure-welded assembly may then be further rolled with or in the absence of annealing to final gauge.

As will be noted during the elongation of the superposed sheets imparted during the pressure-welding operation the blunt nose radius or portions 8 of the foreshortened oval pattern 3 are caused to elongate to the more pointed configuration 9 in FIGURE 2. As will be readily understood, the pointed configuration of the oval pattern in FIGURE 2 each quadrant thereof will correspond to the elevational profile of the stempost of the boat hull obtained in accordance with this invention and this necessary degree of foreshortening required to obtain this pointed configuration will determine the blunt nose configuration 8 of the elongated pattern 3 in FIG- URE 1.

After the pressure-welding operation the welded portions of the component sheets are then trimmed to leave a marginal portion 16 having a width to insure against cutting into the unwelded portions. Preferably, the welded portion of the component sheets will be trimmed so as to leave a marginal portion having a configuration required for the stempost 14 and keel 15 desired on the boat hull. In situations where a deep-keel is not required, the trimmed marginal portion remaining in component sheets may be folded over fiat against the sides or bottom of the boat hull.

These trimmed portions are shown in FIGURE 3 in divided form, for convenience, as trimmed portions 10, 11, 12 and 13. After the trimming operation, the inlet 17 of the unwelded portion 18 corresponding to the band 4 of stop-weld material is suitably opened by an opening tool and a tubular connection or nozzle 19 inserted in a conventional manner into the resultant orifice and the resultant structure is then expanded into the form or configuration 20 illustrated in FIGURE 3. For example,

with 1100 ASM aluminum alloy having its resultant laminae each 0.050 inch thick, water pressure of the order of 200 pounds per square inch may be employed to cause the laminae to be separated and distended away from each other. Upon inflation with either air or water the internal flat void is bulged to the elongated section illustrated in FIGURE 3 both ends of which are pointed to the desired radius of a boat bow. When fully inflated the central portion of the inflated configuration is almost or substantially round while both ends are less round and more pointed. As will be understood, although a trimming operation has been described prior to the inflation of the unjoined metal sheet of FIGURE 2, a final trimming operation may also be preformed subsequent to inflation. Also where the marginal portion of the trimmed sheet is considered too thin to form the keel of the boat although it is twice the Wall thickness, the trimming operation may leave the marginal portion of sufficient width so that it may be folded over on itself to provide the additional necessary requirements of thickness and weight for the keel.

After inflation, the water employed may be emptied out by pumping, draining and the like, and the inflated structure then transversely divided along lines 25 and 26 as by power sawing into quadrants of the elongated oval pattern to provide a plurality of hull bodies 21 corresponding to each quadrant of the elongated oval pattern. This will provide four hull bodies formed to the rough contour of a boat hull, with the stern end open, and a stempost 14 and keel 15 extending along the center of each hull. This rough contoured configuration of the boat hull may be finished by placing the rough hull in a shaped jig with the keel inserted in a central slot appropriately provided in the jig. A weighted forming die, or other shaping means is then lowered into the hull so as to spread and shape the sides and bottom out to the final shape 22. A stern sheet or transom 23 is then secured by welding or riveting or a combination of the two, and the like, in place at 24 across the open stern end so as to complete the water tight boat hull.

An alternate method of forming the transom may be accomplished by slitting some of each side of the laminae at the stern end and bending the bottom at the stern end up to become the transom, with the marginal welded portion thereon left on so as to stifllen the transom. This alternate method leaves only the edges along the sides to be welded to this alternate transom.

Although the inflated structure of FIGURE 3 was divided into quadrants, it will be understood that the inflated structure may be transversely and bilaterally divided along a horizontal line to form two canoe structures and then one of the canoe structures may be further transversely subdivided in two portions to form conventional square end boat hulls to provide one canoe structure and two boat structures. After final shaping of the hulls various accessories may be provided and/or attached to the hull such as a gunwale about the top of the hull, and/or various reinforcing and seating means depending upon individual preferences and requirements.

As can be seen, by means of this invention a substantially seamless boat hull construction is provided, irrespective of the dimensions thereof, extending from the full size boats to toy boats, greatly reducing the number of seams subject to separation through which water may leak. Not only can a plurality of boat hull structures be obtained from a single pattern of stop-weld material, but the plurality can be further increased by providing a multiplicity of

patterns

27, 28 and 29 interposed between an assembly of component sheets 30, which after pressurewelding and elongation may be severed along line 31 and 32 with each individual portion treated as above described. As will be understood, whereas a multiplicity of patterns is employed, and the welding is to be accomplished between rolling mills, the direction of rolling, either transverse and/or longitudinal, will necessarily be dictated by the ultimate dimensions of the desired hull structure in turn dictating the configurations of thet foreshortened stop-weld patterns applied; and, although a multiplicity of patterns in FIGURE 6 are shown interconnected and distinct from each other, they may for convenience, although not shown, be interconnected together by any appropriate means as by a narrow band of stop-weld in the pattern to act as a header.

FIGURE 7 illustrates an assembly of components having stop-weld material applied in a predetermined pattern between the components for fabricating another boat hull embodiment of this invention having a double walled structure. This assembly of components comprises a pair of inner component sheets 33 and 34 superposed upon one another and having interposed between them an ovalshaped pattern 35 of stop-weld material as in the embodiment described in relationship to FIGURE 1. However, in this embodiment one or more outer sheets 36 are superposed opposite and adjacent each external face of the pair of inner sheets 33 and 34. In addition, one or more insert sheets are suitably adapted, as by slitting, shearing and the like, to provide a plurality of insert strips laterally across the inner and outer sheets and transverse the major axis 37 of the oval elongated pattern 35 and longitudinally aligned in the direction of the major axis 37. In the instant example of FIGURE 7, two

insert sheets

38 and 39 are provided between each adjacent pair of inner sheets 34 and outer sheet 36 to form complementary portions for the desired integral ribbing between the double walled boat hull. Each of these

insert sheets

38 and 39 are divided into the same number of insert strips 40 and 41, respectively, and disposed between the inner and outer sheets as described above. Although the insert sheets are shown to be completely divided into insert strips, these insert sheets may also be adapted to provide the desired strips by partially slitting theinsert sheets laterally from one side to a point short of the other side, or the insert sheet may be laterally slit in the inner portions thereof within a pattern that disposes the slit opposite to and co-extensive with the elongated oval pattern 35.

The insert sheets arel th en coated with bands of stopweld material extending in the direction of the major dimension of the insert strips. These bands of stop-weld material are applied so that selective portions of the stirps will weld either to one another or-to the inner or the outer sheet. In the embodiments illustrated,-strips ill-and 41 are coated on their surfacesadjacent the outer'sheet 36 and the inner sheetj34, respectively, with bands 42 of stopweld material adjacent the edge'of major dimension to leave a band 43 on thesurface devoid of stop-weld mate rial so as to permit this portion of

strips

40 and 41 to pressure-weld to the outer sheet 36 and the inner sheet 34 respectively. The adjacent surfaces between insert strips 40 and 41 are separated from each other bya band 44 of stop-weld material applied to one of these adjacent surfaces between uncoatedmarginal portions 45 adjacent the edge of the strips having the major dimension. However, as will be understood, these bands 42 of stop-weld material'rnay alternatively be applied to either or both surfaces of inner sheet 34 and outer sheet 36. Irrespective of the surfaces applied these bands of stop-weld material are applied in a manner so that their composite form secondary

elongated patterns

46 and 47 on

insert sheets

38 and 39, respectively, which patterns are disposed Within the peripheral edges of the insert sheets as to be opposite to and co-extensive with the elongated oval pattern 35 interposed between inner sheets 33 and 34.

Preferably, as will be observed in FIGURE 9, the bands of stop-weld material between one pair of adjacent surfaces are in overlapping'relationship with the bands of the next successive pair of adjacent surfaces. For example in FIGURE 9, bands 42 between the insert strip and the adjacent surface of either the inner sheet or outer sheet overlaps the band 44 disposed between the adjacent surfaces of the insert strips. The portion of the strip disposed in the overlapping portions of the bands remains unwelded and is permitted to unfold and separate when the outer sheet is placed in relationship to the inner sheet. Although not always required, stop-weld material is preferably also applied on the edge surfaces of the strips adjacent a succeeding strip to insure against possible welding of the edges of the strips together upon pressurewelding.

'After the application of the stop-weld material, the various components are secured together against relative movement, heated to pressure-welding temperatures and pressure-welded, as between .mill'rolls, in all the adjacent areas not separated by the stop-weld material. The adjacent surfaces between inner sheets 33 and 34 are welded together in their uncoated areas in the same manner as the embodiment of FIGURE 1. The manner in which the components between the opposed surfaces of the sheet 34 and outer sheet 36 weld together may be seen by reference to FIGURE 10. In this figure, it can be observed that portions of each insert are pressure-welded to each other at 48, to the inner sheet 34 at 49, and to the outer sheet 36 at 50 to result in laminations or spaced unwelded-areas between the insert strips, lamination 52 between the adjacent surface of inner sheet 34 and the component insert strip adjacent thereto, and in laminations 53 between the adjacent surfaces formed by outer sheet 36 and its adja cent component strip.

Thus, the pressure-welding between adjacent insert strips 4t) and 41 occurs along portions of their adjacent surfaces adjacent their edges, and to either the inner or the outer sheets at points or in bands intermediate the edges of the insert strips. This manner of welding forms a plait or a plaited section extending, for example, from the point of welding to'the inner sheet 34 through the point 48 of which the insert strips are welded together and to the point in which one. insert strip is welded to the outer sheet 36. This plait upon spacing of the outer sheet from the inner sheet, unfolds to provide the crossjoined portion or the lamination between the inner sheets corresponding to the elongated oval pattern 35 of stopweld material is expanded first by inflation with fluid pressure (of water or air) to the general configuration of the plurality of boat hulls corresponding to each'quadrant of the oval pattern. Subsequent thereto, the outer wall 36 is then separated and spaced from the inner wall 34 by inflation with fluid pressure injected between, these two sheets. During such separation the plaited portions be-" tween the inner and outer sheets unfold ing cross-members 55. V

This structure with the'unjoined portion between inner sheets 33 and 34 distended and the outer sheets spaced from the inner sheet 34 forms another aspect of this invention by providing an integrally reinforced member that can be suitably employed as av container or cylinder for storage of various fluid media as a storage tank, or for transportation as a tank for railroads and various other vehicles. Such a tank construction is not only double walled, but is seamlessly reinforced with cross-members that are part of each wall with junctures having a tensile strength substantially equal or equal to that of any other seamless region of the structure.

For application in boat construction, the completely inflated unit, between the inner sheets and the outer sheets, is then transversely divided by any conventional cutting process into quadrants of the elongated oval patinto correspondtern 35 whereby each quadrant provides a'double walled boat hull 56 open at the stern end 57. As with the preceding embodiment, the welded structure obtained from the various components of FIGURE 7 may be suitably trimmed either before or after separation and inflation of the various unjoined portions. Also as with the preceding embodiment, this double walled boat hull may be finished by shaping and by providing at its open stern end a suitable transom secured across the open end, and also with suitable gun-wales across the top of the sides of the hull, plus any convenient and suitable seating means. Also, other desired accessories may be added depending on individual preference and requirements for the application to which the boat is to be put.

Although the inven-tion has been described with reference to specific embodiments, materials and details, various modifications and changes, within the scope of this invention, will be apparent to one skilled in the art, and are contemplated to be embraced within the invention.

What is claimed is:

1. The method of fabricating a boat hull comprising the combination of steps of interposing an elongated oval shaped pattern of stop-weld material between superposed sheets of metal wherein each quadrant of said oval defines in the same direction a foreshortened configuration of the elevational profile of said boat hull, pressure welding said sheets together in the areas not separated by said material while simultaneously elongating said sheets and said pattern thereinbetween in the direction in which said pattern is foreshortened, injecting fluid pressure in the unwelded portion between said sheets defined by said material to inflate and outwardly deform said sheets, and transversely dividing said inflated and deformed sheets into quadrants of said elongated oval pattern.

2. The method of claim 1 including arcuately trimming the welded portions of said sheets along a line spaced from the unwelded portion between said sheets to provide a marginal welded portion of said sheet adjacent said unwelded portion therein.

3. The method of claim 2 wherein said trimming provides a sufiicient marginal welded portion of said sheet to form the keel and stempost of said boat hull and the step of securing a transom across the cross-sectional configuration at the stern of said divided and formed sheets.

4. The method of claim 3 including further shaping said divided and formed sheets into the ultimate configuration of said boat hull.

5. The method of fabricating a boat hull comprising the combination of steps of superposing a pair of coextensive inner sheets upon each other, superposing an outer sheet adjacent each outer face of said inner sheets, interposing at least one elongated oval shaped pattern of stopweld material between said inner sheets wherein each quadrant of said oval pattern defines in the same direction a foreshortened configuration of the elevational profile of said boat hull, interposing at least one insert sheet between an inner sheet and the outer sheet adjacent thereto, said insert sheet being adapted to provide a plurality of insert strips laterally across said sheets transverse the major axis of said oval pattern and longitudinally aligned in the direction of said major axis, interposing parallel bands of stop-weld material transverse said major axis between all adjacent surfaces between said inner sheet and said outer sheet adjacent thereto, said band being opposite to and coextensive with said oval pattern wherein each of said bands between one pair of adjacent surfaces is in overlapping relationship with the bands of the next successive pair of adjacent surfaces, pressure welding said sheets together in the areas not separated by said material while simultaneously elongating said sheets and said oval pattern thereinbetween in the direction in which said oval pattern is foreshortened, injecting fiuid pressure in the unwelded portions between said inner sheets to inflate and outwardly deform'said sheets, injecting fluid pressure between the unjoined portions remained between the adjacent the adjacent surfaces disposed between said inner sheets and the outer sheets adjacent thereto to separate and space said outer sheet from its adjacent inner sheet with the unwelded portions of said inner strips extending between said outer sheet and its adjacent inner sheet, transversely dividing said deformed sheets into quadrants of said elongated oval pattern, and trimming the welded portions of said sheets externally and on a line spaced from the periphery of said elongated oval pattern.

6. The method of claim 5 wherein said trimming provides a sufficient marginal welded portion of said sheet to form the keel and stempost of said boat hull and the step of securing a transom across the cross-sectional configuration at the stem of said divided and formed sheets.

References Cited by the Examiner UNITED STATES PATENTS 177,153 5/76 Pitman 96 433,085 7/90 Keys 114-79 1,335,072 3/20 Nichols 96 1,492,981 5/24 Hill 114-79 1,855,161 4/32 Wyman 154-45 2,212,481 8/40 Sendzimir 29-455 2,398,131 4/46 Bourne 96 2,498,275 2/50 Johnson. 2,515,162 7/50 Hall 9-6 2,585,344 2/52 Plaziak 9-6 2,634,436 4/53 Paziak 96 2,662,273 12/53 Long 29-157.3 2,816,298 12/57 Foster 154-459 2,882,588 4/59 Rieppel 29-157.3 2,926,003 2760 Pulsifer 29-157.3 2,944,328 7/60 Adams 29157.3 3,046,647 7/62 Carstens 29-421 FOREIGN PATENTS 205,695 1/57 Australia.

212,814 2/58 Australia.

341,204 1/31 Great Britain.

WHITMORE A. WILTZ, Primary Examiner.

MILTON BUCHLER, NEDWIN BERGER, JOHN F.

CAMPBELL, Examiners.

Claims

1. THE METHOD OF FABRICATING A BOAT HULL COMPRISING THE COMBINATION OF STEPS OF INTERPOSING AN ELONGATED OVAL SHAPED PATTERN OF STOP-WELD MATERIAL BETWEEN SUPERPOSED SHEETS OF METAL WHEREIN EACH QUADRANT OF SAID OVAL DEFINES IN THE SAME DIRECTION OF FORESHORTENED CONFIGURATION OF THE ELEVATIONAL PROFILE OF SAID BOAT HULL, PRESSURE WELDING SAID SHEETS TOGETHER IN THE AREAS NOT SEPARATED BY SAID MATERIAL WHILE SIMULTANEOUSLY ELONGATING SAID SHEETS AND SAID PATTERN THEREINBETWEEN IN THE DIRECTION IN WHICH SAID PATTERN IS FORESHORTENED, INJECTING FLUID PRESSURE IN THE UNWELDED PORTION BETWEEN SAID SHEETS DRFINED BY SAID MATERIAL TO INFLATE AND OUTWARDLY DEFORM SAID SHEETS, AND TRANSVERSELY DIVIDING SAID INFLATED AND DEFORMED SHEETS INTO QUADRANTS OF SAID ELONGATED OVAL PATTERN.