US2974624A - Ship - Google Patents

Description

E. V. LEWIS SHIP 3 Sheets-Sheet 1 Filed March 11, 1959 i 0- I /KH 3 GE 7 o N w m o HHHHH I I I MH IHH I 1H nu N m m E. V. LEWIS March 14, 1961 SHIP 3 Sheets-Sheet 2 Filed March 11, 1959 INVENTOR ATT'oRNEn E. V. LEWIS aha: 43

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-m 0743 43 2 mm N M743 non: QN IS SHIP Edward V. Lewis, Hohokus, N.J., assignor, by mesne assignments, to the United States of America'as represented by the Secretary of the .Navy.

Filed Mar. 11, 1959,'Ser. No. 798,195 Claims. (Cl. 114-'56) This invention generally relates to surface ships for high speed operation, and more particularly relates tosimprovements in hulls for surface ships in order to obtain greater seaworthiness at high speeds in rough waters.

A surface ship undergoes various undesirable motions, such as roll, pitch, and heave, when traveling in seaways. When these motions are excessive, they produce destructive forces which have an adverse effect on the structure of the ships hull, on the structural parts and arrangements Within the hull, and on the functioning'of machinery, instruments and other equipment of the ship. In the case of a fully loaded cargo ship, excessive motions may cause shipping of water in head seas to the detriment of the ships cargo. Furthermore, accelerations inherent in such motions are believed to be primarily responsible for seasickness and frequently for shipboard accidents. Other undesirable effects are caused by motions of a ship; and it is not unusual for a ship to reduce its speed in order to limit such effects. 7. r

The nature and extent of the motions of'asurface ship depend in part upon the waves that the ship encounters. Thewwaves will be of different lengths, heights and steepness, and include waves having lengths ofthesame-order of magnitude as thelength of the ship. Under certain conditions of ships speed, a synchronism? arises which magnifies some of the motions of .a ship and increases the harmful effects thereof. This ,synchronism arises when the natural pitching period of a ship harmonizes with its period of encounter with waves. ,The speed of .aship, when this synchronism arises, is calledthe critical speed of the ship. When the speed of the ship is below this critical speed, it is recognized as operating in asubcritical range, and when above in asupercriticai range. Operating the ship in either range reduces the deleterious effects of the magnified motions of 'sy'nchronism. I I

An object of the invention is to provide a displacementtype surface ship capable of operating safely and with small amplitudes of vertical motions at ,high speeds in both calm and rough sea's, the ship being capable ofoperating at supercritical speeds in rough seas when such operation. is preferred.

It is a further object of the present invention to provide lines for the hull of a ship that result in .a's'hip having reduced amplitudes of motion, safe operating speeds, .especiallyin rough seas, and-other advantages.

In'ge'neral, it is an objectof the invention to provide a surface ship of high speed having a long natural pitching period.

Other objects and many of the attendant advantages of this invention will'be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with theaccompanying drawings in Whi'ch' like reference im- 2,974,624 Patented Mar. 14, 196i ICE meralsdesignate like parts throughout the figures thereof and wherein:

Figs. 1A and 13, joined along the broken lines, is a longitudinal elevational outline view of a ship having a hull in accordance with the invention;

Figs. 2A and2B, joined along the broken line, 'is a diagram showing, in accordance with standard practice, a half-plan view of thelongitu'dinal water lines of the hull at different water line planar levels;

Fig. 3 is a diagram showing, in accordance with standard practice, a body plan of the transervsehull lines or cross-sections at various stations, the lines on the right of the center line being forward or forebody lines at different stations, and the lines on the left of the center line being the aft or afterbody lines at different stations.

A ship in'accordance with the invention is built with a hull along the lines of Figs. 1-3. Figs. 1A and 1B, the top line A represents the main deck and the bottom line B represents the base line of the hull, and may be considered indicative of its keel. The ship has a bow C and thestern D. In Figs. 2A and 2B the line E represents the and comparatively higher vertical longitudinal center plane of the hull, it being understood that the hull is symmetrical on both sides of this plane. For identificationpurposes, the length of the ship is divided into spaced transverse stations. Generally the practice is to divide the ship into twenty stations, each station representing a plane that is perpendicular to the longitudinal axis of the hull. The stations shown in Figs. 2A and 2B are the even stations ()(zero) through 20, but with the addition of a central station '11. The stations are equally spaced except that stations 10 and 1 1 and stations 11 and 12 have somewhat smaller spaces therebetween, the two spaces, however, being equal.

Similarly, as shown in Fig. 3, the vertical extent of the hull is divided by spaced horizontal water line planes shown as lines (WLP) 2, 4, 6, 8, 12, 13, 14, 16. 17, 18, 20, 22 and 24 which are relatively spaced from the base line in the ratios indicated in the associated parentheses.

The figures are drawn substantially to scale, but not necessarily to thesame scale. In Figs. 1A and 1B, the ver tical scale is double the horizontal (fore and aft) scale. In Figs. 2A and 2B, the vertical scale is three times the horizontal scale. This has been done in order better to show the configuration of the water line projections which, if drawn to the same scale throughout, would re.- quire the lines to be more closely spaced than shown in the figure. In .Fig. 3, the horizontal and vertical scales are the same.

The transverse station planes and the water line planes intersect the hull in curved lines which are indicated in Figs. 2A, 2B and 3 in accordance with standard practice,

each line being identified with the plane in which it lies. In Figs. 2A and 2B these curved lines are the lines including the designation WL; and in Fig. 3 they are the lines including the designation T.

An inspection of Figs. 2A, 2B, and 3 shows that the hull forms along slender ship with very fine water lines that is adapted for destroyer type vessels. The ship shown has a length to beam ratio of 10.5.

'It is difiicult to describe the shape of the hull in a few words. As indicated in Figs. 2A and 23, between the transverse central stations 16 and 12, which may be called them'idship of the hull, the hull is of fairly uniform width, except at the bilge and below the water line. The distance between stations 10 and 12 represents 13.3 percent of the length of the ship. The distance forward of station to the zero station represents 48.2 percent of the length of the ship. I

Forwardly of station 10, the water lines converge longitudinally fairly smoothly to the bow stem, but with the upper and the lowermost lines somewhat more rapidly than the central longitudinal lines WL4 through WL13. Rearwardly or aft of station 12, the bottom rises relatively rapidly to a knuckle near water line plane WLPlll. The upper abaft water lines converge longitudinally and more rapidly than the forward water lines.

Transversely, the upper midship portion between stations 10 and 12 has fairly straight walls with slight tumble home near the top. Fore and aft of midship portion, the hull has significant tumble home. This is apparent from Figs. 2 and 3. The water line plane WLP13 forms the water line of the ship under normal operation. This line is only slightly above the vertical center water line plane of the hull which is exactly midway between the deck and base line; and the tumble home above WLP13 is appreciable both fore and aft of the midship portion. This is apparent in Fig. 3 from the large inward curving of lines T2, T4, T6 and T8 of the morebody, and lines T14, T16, T18 and T20 of the afterbody. The inward curvature of these lines starts from below WLP13, the normal water line plane, and extends almost to the deck, WLP24.

As is apparent from Figs. 2A, 2B and 3, the hull is shaped somewhat like a submarine, except for the uppermost part which is bounded by the main deck at the water line plane WLP24. The reason for this is to permit the ship to ride lower in the water when it encounters rough seas. Water line plane WLP17, called the submerging Water line plane for convenience, represents the water line for the ship operating in such seas. This last line is about three-fourths of the height of the hull above the base line. When riding thus, the ship resembles a surfaced submarine but is considerably longer and more slender.

In order to lower the ship to the submerging water line plane, thereby increasing the displacement, the ship is provided with peak water ballast tanks fore andaft, and with flooding and pumping equipment to fill and empty the tanks. Preferably the heavier moving parts of this equipment are in the midsection of the ship. The tanks and equipment, per se, form no part of the invention, since any suitable apparatus may be used. Accordingly, they have been schematically indicated in Figs. 1A and 1B as comprising tanks 50 and 52, and pumping equipment 54.

It will be observed in Figs. 2A and 2B that the ship has a narrow main deck indicated by water line WL24, and that the submerging water line area encompassed by the WL17 is also narrow but not as narrow as the deck.

2e ship has a low freeboard above the water line plane In calm weather, the ship floats at the normal water line shown. Under storm conditions, the ballast tanks are filled until the ship settles so as to be at the higher submerging water line. The result is an increase in the natural pitching period of the ship arising from the increased mass, radius of gyration, and decreased waterplane area. The location of the ballast at the peaks of the hull also lengthens the natural pitching period.

The increased pitching period of the ship induces the ship to plunge through waves rather than riding over them. The ship can then operate at supercritical speeds with acceptable seaworthiness. A lengthened and fine ship of a type described with lengthened pitching period permits operation in storm seas at speeds as much as fifty percent higher than ships of customary design such as the aforesaid destroyer.

The high speed operation in rough seas and the low freeboard subject the ship to boarding seas. Consequently, the ship must be structurally strong, with the main deck heavily built. The size of 4 deck, represented by numeral 56 in Figs. 1A and 1B, is kept to a minimum, with adejuate strength to withstand the boarding water.

Because of the rounded sides of the ship, it is prone to rolling motion. For reduction of this motion, antirolling fins may be provided on the hull.

The improved characteritics of a ship in accordance with the invention is apparent from the following data given in unit ratios unless otherwise indicated.

Semi-submerged Ship at deep draft Destroyer (WLP17 Length of LWL 5.720 5.720 Breadth 0.608 0.540 Draft 0.208 0.250 Displacement, pound units 24.5 27.7 Freeboard at bow, F 0.280 0.100 Freeboard ratio, F/L (Length) 0.049 0.017 Longitudinal radius of gyration 0.24L 0.26L Natural pitching period, T,,, sec 0.60 0.92 r,,/ vi 0.25 0.38

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim:

1. A surface ship adapted for high speed operation in rough seas while traveling in a semi-submerged condition, comprising a hull having a normal operation water line substantially midway of the height thereof, said hull having a midship portion with substantially straight sides above said water line, the portion of said hull forward of said midship portion having a deck having a lesser area than the area of a plane through said water line, the portion of said hull forward of said midship portion being longer than the portion of said hull aft of said midship portion, said forward and said aft portions having tumble home lines, the forward portion comprising about 48.2 percent of the ships length, and the midship portion about 13.3 percent of the ships length, said forward portion converging to the bow stern, and said rearward portion converging to a knuckle line at the stern, the bottom, exterior of said hull being outwardly curved from said water line to its' keel, said ship having peak ballast tanks adapted when filled to place the water line a distance about threefourths of the height of the hull above its base line, a plane through the last said waterline being of lesser area than the area of the plane through the first said water line, but of greater area than said deck.

2. A surface ship adapted for high speed operation in face thereof over at least a portion of the area thereof.

4. A surface ship adapted for high speed operation in rough seas while traveling in a semi-submerged condition, as set forth in claim 1 wherein, the exterior surface of said hull both forward and aft of the midship portion, and above said second waterline, is inwardly curved.

5. A surface ship adapted for high speed operation in rough seas while traveling in a semi-submerged condition, as set forth in claim 1 wherein, the exterior surface of the forward portion of the hull located between the first andsecond waterlines is composed at least in part, of an area that is outwardly curved at the exterior surface, and

the structure above the 15 a portion that is inwardly curved at said exterior surface,

and is inwardly curved above said second waterline; and References Cited in the file of this patent the portion of said hull aft of said miship portion and 10- UNITED STATES PATENTS cated between said first and second waterlines has substan- 293 793 sebiuot Feb. 19 1884 tially the entire exterior surface thereof outwardly curved, 768269 Aug 1904 and said exterior surface of said aft portion of the hull 5 2185:431 Burgess f Jam 1940 located above said second waterline inwardly curved. 7 2,253,245 Norton et a1 Aug 19, 1941

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