US3267896A - Ship's hull - Google Patents

Description

L. COSTA SHIP'S HULL Aug. 23, 1966 2 Sheets-Sheet 1 Filed June 9. 1964 L. COSTA SHIP'S HULL Aug. 23, 1966 Filed June 9. 1964 2 Sheets-Sheet 2 United States Patent 3,267,896 SHIPS HULL Leo Costa, Vienna, Austria, assignor to Maierform Holding S.A., Geneva, Switzerland Filed June 9, 1964, Ser- No. 373,670 7 Claims. (Cl. 114-56) This invention relates to a ships hull and, more particularly, to a shape of bulbous bow sometimes called a club foot. The invention is particularly suitable for fast ships of every type having a lower Froude number speed-length ratio of about 0.25 (metric).

It is the chief object of this invention to provide a bulbous nose of the type mentioned, having its largest diameter in the load waterline with a wedge type swelling of the bulb which steadily decreases in the direction of the keel aft, and extends upwardly above the load water line to a distance of at least one fourth the draft or depth of the immersed portion of the hull.

Another object is to provide a hull wherein excessive pitching is obviated by a stem of improved form having a downwardly evenly-decreasing cross section of the bulb of the bow.

Still another object is to avoid and obviate the drawbacks of conventional bulbous bow constructions.

Yet another object is to provide a bulbous ships bow wherein the cross sections of the several waterlines at the stern are preferably in the form of circular or conic section arcs.

Another object is to provide a bulbous bow as aforesaid wherein each waterline extending from the greatest horizontal transverse dimension of the bulb, first passes outwardly of the corresponding waterline of a conventional form of hull, and with increasing distances aft of the bulb gradually approaches, intersects, passes within, and again gradually approaches the aforesaid corresponding waterline of a conventional form of hull. In some cases, however, the respective waterlines of the invention may not actually intersect the aforesaid conventional load waterline but merely approach the same with increasing distances aft from the bulb or stem and merge into the conventional line at a frame such as 18 depicted upon the drawings. The constriction thus formed rearwardly of the stem portion, designated as a pocket, is, of course, greatest in and above the load waterline and becomes less pronounced with waterlines of increasing distance below load waterlines.

Yet another object is to provide a bulbous bow of the type aforesaid which results in appreciable savings in power required for propulsion at any given speed, results in decreased bow waves, decreases pitching by increasing buoyancy at and along vertical transverse sections adjacent the fore part of the bow, and improves the form of the entire wave profile along the sides of the hull.

Other objects and advantages will be apparent to those skilled in the art, after a study of the following detailed description in connection with the accompanying drawing.

In the drawing:

FIG. 1 is a vertical longitudinal view of the profile of the stem and bow portions of a hull embodying the invention and showing the contours at various water lines WLO to WL6, as compared to the corresponding profiles of a conventionally shaped hull;

FIG. 2 is a view showing half-section profiles in vertical transverse planes numbered in correspondence with those identified upon FIG. 1;

FIG. 3 shows to a greatly enlarged scale, the profile in and along the construction waterline, of the bow of a ship embodying the invention, with the corresponding profile of a ship having a bow of conventional or usual 3,267,395 Patented August 23, 1966 form shown in dotted line and the largest to the bulbous stern shown in dot-dash line;

FIGS. 4, 5 and 6 each correspond to FIGS. 1, 2 and 3, respectively, but show a somewhat diiferent shape of stem portion, both in side elevation and in waterline sections.

Referring in detail to FIGS. 1, 2, and 3, S indicates the stem contour and CWL the construction waterline. Waterline planes WLO through WL6 are identified as straight horizontal lines and at each is shown by a solid line, the half-profile of the hull at that line, starting from a point defined by the intersection of each horizontal line with the stemline. Also, starting from each of the aforesaid points as shown, in dotted lines, the corresponding profile of a hull of conventional or prior art form. At each waterline or horizontal plane the dotdash line is a tangent to the conic section or other are defining the bulbous stem, and extending rearwardly and outwardly from the respective terminal points A, B, C, D, E, etc. thereof.

Referring more particularly to the enlarged-scale view of FIG. 3, there is shown in solid line, the profile of a hull embodying the invention, with the corresponding profile of a hull of conventional form shown in dotted lines From this figure it is noted that, starting from its intersection with the stem line and extending to point A, the CWL line of the hull embodying the invention, has the form of a portion of an ellipse so that point A lies outwardly of the corresponding point of a hull of conventional design. From a point of tangency at A, the CWL of the invention gradually approaches the convention dotted line form, crosses it, and then fairs outwardly to again approach and eventually to generally coincide with the dotted-line construction. Still referring to FIG. 3, dimension .2; identifies the greatest or maximum horizontally-inward departure of the CWL of the invention from the conventional dotted-line form. As previously explained, the dot-dash line 2. identifies a straight line tangent to the ellipse at point A, so that the dimension f is the offset inwardly of the point of maximum departure of the CWL of the invention from this line of tangency.

FIG. 3 is thus illustrative of the corresponding solid, dotted and dot-dash lines indicated upon FIG. 1 for each of the Waterlines 0 through 6, and the corresponding e and f distances described in the preceding paragraph. Reverting to FIG. 1, the dimension d for example, is the horizontal distance between the two term-i-' nal points A, intersected on the elliptical portion of the stern b-y CWL (WL4). The points on water lines WL3, WL2, WL1, and WL /2 corresponding the point A, FIGS. 1 and 3, are identified respectively at B, C, D and E, and in each case locate or identify the thickest part, or part of greatest diameter of the stem bulb at the corresponding water line. Inspection of FIG. 1 shows that these distances d d etc. progressive increase from the lowermost water line plane, upwardly. A faired line L, FlGS. 1 and 2, passing through the aforesaid points A through E, etc., is generally parallel to stem line S, as is clear from inspection of FIG. 1. From this figure it is also noted that line L extends uniformly and fairly from the uppermost water line almost to merger'with keel line K.

From FIG. 2 it is noted that a projection of line L onto a transverse vertical plane is essentially straight from its intersection with WLl to its intersection with uppermost WL6, and departs only slightly upwardly and outwardly from parallelism with the vertical longitudinal median plane of the hull. This feature is characteristic of all embodiments of the invention.

The largest dimension by which the waterline depart-s inwardly, that is, toward the vertical longitudinal median ice plane of the hull, is identified at e and occurs at the normal or load water line. As clearly shown upon FIG. 1, thus e dimension uniformly decreases at subsequent lower Water lines. Likewise distance f previously explained, is a maximum and other f distances such as f f etc. progressively decrease. A fair curve B, FIG. 1, connecting all points f f etc. is simple, and shows that there is no local swelling in the bow between frames 18 and 19 identified upon the figures. As seen upon FIG. 2, the projection E of line B, onto a transverse vertical plane is also essentially straight over the main portion of its length.

The form of the invention shown upon FIGS. 4, 5 and 6 corresponds generally to that depicted upon FIGS. 1, 2 and 3. Since all lines are identified by referenc characters corresponding to those of FIGS. 1, 2 and 3, and since the significance of the solid, dotted and dot-dash lines are the same as in the form previously described, it is deemed unnecessary to explain FIGS. 4, 5, and 6 in detail.

However, unlike the species of FIGS. 1, 2 and 3, the cross sectional form of the stem in water line planes is parabolic as shown more clearly upon FIG. 6. The particular conic section selected is not critical and may be any section from circular to parabolic or even oval, and in particular cases it may be formed with a rather gentle entrance.

[In all cases the starting point for establishing the dimensions d d etc. is given by the range of Froudes numbers for which the ship of the present invention is to be used. As shown upon FIG. 4, the stem line is extended deadwood-like into the generally triangular space formed between the forward plumb line P, keel li-ne K and stem line S. In this way the superiority of a bow constructed according to the invention can be further enhanced, particularly for Froude numbers between 0.25 and 0.30 and above.

The bulbous bow constructed in accordance with the invention utilizes to better advantage the trim efiect of the hull, in cooperation with the pocket formed as the result of the construction between the stem and frame 19. This coaction decreases the bow wave at any given speed, over that of a like hull of conventional form, essentially with respect to its mass, i.e., more in its breadth than in its height. The improved hull form also has a favorable bearing on the entire wave profile along the side of the hull. That is to say, successive wave crests :becorne lower and the wave troughs flatter, thus decreassing the power required for propulsion. A total saving of from 4 to 6 percent in propelling energy is thus made possible.

The foregoing disclosure relates directly to the embodiments shown and described and numerous modifications or alternations are possible without departing from the spirit and scope of the invention pointed out by the appended claims.

I claim:

1. A bow of a ships hull comprising a stem provided with a swelling, the horizontal cross-sections of said swelling having the shape of a section of a cone, the diameters of said cone sections decreasing in size from the load. waterline to the keel, said swelling extending above said load waterline into the dead work of the ships hull to a height corresponding at least to one fourth of the draught.

2. A ships h-ull as claimed in claim 1 comprising pockets formed behind the swelling by curves merging the swelling into the waterlines.

3. A ships hull as claimed in claim 2 wherein said pocket-forming waterlines first intersect, and then merge into, the normal base waterlines.

4. In a ships hull having a vertical longitudinal median plane of symmetry, a bow having a stem swelling in each of a plurality of horizontal vertically-spaced planes normal to said median plane, the cross-section of the swelling in said planes being in the outline form of substantially a half of a section of a cone having its apex on the stem line of said bow and its terminals at two points symmetrically disposed with respect to and upon opposite sides of said median plane rearwardly of said stem line, the respective tangents of said conic section at each said point diverging rearwardly and outwardly in respective ones of said horizontal planes, symmetrically with respect to and upon opposite sides of said median plane, the side profiles of said bow in each said horizontal plane coinciding with said tangents at said points, then curving inwardly and rearwardly, then outwardly and rearwardly, in fair curves, each with respect to its said tangent, said horizontal planes extending from substantially the keel line of said hull to a distance at least one-fourth of the draft above the load water line thereof.

5. In a ships hull having a vertical longitudinal median plane of symmetry, a bow having a stem swelling in cross section in each of a plurality of parallel horizontal waterline planes normal to said median plane, each said cross section being in outline substantially one-half of a section of a cone with its apex on the stem line of said how and its terminals at the point symmetrically disposed with respect to and upon opposite sides of said median plane rearwardly of said stem line, the respective tangent lines to said conic section at each said point diverging rearwardly and outwardly each in its respective waterline plane, symmetrically with respect to, and upon opposite sides of said median plane, the side profiles of said bow in each said waterline plane connecting with the corresponding tangent line at a respective one of said points, then curving inwardly and rearwardly, then outwardly and rearwardly in fair curves, each with respect to its said tangent line, said planes extending from substantially the keel line of the hull to a vertical distance above the load waterline at least one-fourth of the draft of said hull, the distance of separation of said points in each respective waterline plane decreasing uniformly in sequential planes from the construction waterline plane to therebelow, a fair curve connecting all said points on one side of said median plane being essentially parallel to the stem line of said bow, the projection of said line upon a transverse vertical plane normal to said median plane being essentially a straight line diverging upwardly and out- Wardly at a small acute angle from said median plane, the maximum separation point of the profile line of the bow, inwardly from the corresponding tangent line being in said construction line plane and decreasing uniformly in sequential planes there-below, all said points of maximum separation on the corresponding side of said median plane conjointly defining a second fair curve, the projections of said second fair curve onto said median plane and onto a transverse vertical plane normal thereto, being essentially straight lines diverging from said respective planes upwardly and forwardly and upwardly and outwardly both at small acute angles with Vertical.

6. The hull of claim 5, said cone section being elliptical.

7. The hull of claim 5, said cone section being parabolic.

References Cited by the Examiner UNITED STATES PATENTS 3,090,338 5/ 1966' Costanzi 114-56 3,180,299 4/ 1965 lnlli 1l4--56 FOREIGN PATENTS 449,417 6/ 193 6 Great Britain. 109,257 12/ 1943- Sweden.

MILTON BUCHLER, Primary Examiner. T. M. BLIX, Assistant Examiner.

Claims (1)

1. A BOW OF SHIP''S HULL COMPRISING A STEM PROVIDED WITH A SWELLING, THE HORIZONTAL CORSS-SECTIONS OF SAID SWELLING HAVING THE SHAPE OF A SECTION OF A CONE, THE DIAMETERS OF SAID CONE SECTIONS DECREASING IN SIZE FROM THE LOAD, WATERLINE TO THE KEEL, SAID SWELLING EXTENDING ABOVE SAID LOAD WATERLINE INTO THE DEAD WORK OF THE SHIP''S HULL TO A HEIGHT CORRESPONDING AT LEAST TO ONE FOURTH OF THE DRAUGHT.

Images