US3162169A - Ship of reduced structural weight for given cargo weight carrying capacity - Google Patents

Description

J. FERRIS Dec. 22, 1964 s'TRU CARGO WEIGHT 3,162,169 SHIP 0F REDUCED CTURAL WEIGHT FCR GIVEN CARRYING CAPACITY 2 Sheets-Sheet l Filed Jan. 23, 1954 INH ll Il Il II II Il l Dec. 22, 1964 N. J. FERRls 3,162,169

SHIP OF REDUCED STRUCTURAL WEIGHT FOR GIVEN CARGO WEIGHT CARRYING CAPACITY 2 Sheets-Sheet 2 Filed Jan. 23, 1964 Fig. 6

Nohanel James Ferris, Inventor By J Attorneys United States Patent O 3,162,169 SEEE QF REDUCED STRUCl lllAL WEXGHT EUR GIVEN CARG WEIGHT? CARR/liti@ SAPACETY Nathaniel .lames Ferris, Chappadua, NSY., assigner to Theodore E. Ferris de Sons, New Yorlr, NX., a

partnership Filed dan. 23, w64, Ser. No. 339,630 24 Claims. (Cl. lill- 72) This invention relates to improvements in ship design. It relates particularly to improvements in ship design having the effect of providing a ship characterized by a high degree of structural economy. It relates more particularly to such improvements incorporated in a self-propelled ocean going marine vessel intended to carry liquid cargoes, that is, a tanker.

This application is a continuation-in-part of co-pending application Serial No. 204,314 filed in the United States Patent Office on'June 22, 1962.

lt is an object of this invention to provide a ship of reduced structural weight for a given cargo weight carrying capacity, or, conversely, a ship with superior cargo carrying ability per unit weight of ship co-nstructed.

It is another object of this invention to provide a ship in which the cargo storage space within the hull has a substantially consolidated arrangement, the extent of which cargo space, as a proportion of the hull length, significantly exceeds that possible in standard hulls.

It is another object of this invention to provide a ship in which, in comparison with ships of standard design, the space for propulsion machinery within the hull is reduced to the extent of practical elimination.

It is another object of this invention to utilize parameters of hull form beyond the conventional range, doing so with significant net advantages not possible with standard hulls.

It is another object of this invention to provide a ship for liquid cargoes which is particularly advantageously arranged internally with respect to shortness of runs of intank cargo piping and accessibility of cargo tank valves.

It is another object of this invention to lprovide a ship having features which qualify it uniquely for the application of modern marine technology in the concepts of systems engineering, centralized control, and automation.

Taking as a fundamental requirement the achievement of a structurally economical decian, a starting point may be that of a ship of substantially standard or conventional form having `a given draft, displacement, and deadweight when floating at designed weight load condition, that is, at its designed load waterline. F or purposes of clarity, draft is defined as the depth of the ship below the waterline measured to the lowest part of the hull, propellers, or other reference point, usually the lowest part of the hull, that is, the bottom line of the keel. Displacement is defined for present purposes as the full load total displacement at the summer freeboard draft, and may be said to be the sum of the light ship weight plus the full load deadweight for any given hull form and draft. Full load or total deadweight is in turn defined as the full cargo weight plus the weight of the ships fuel, water, stores, passengers, crew, and personal effects of lpassengers and crew.

Within the contemplation of the present invention, a characteristic of a ship of substantially standard or conventional form is the location below the main or frecboard deck, that is, well down within the structural hull', of all of the Ipropulsion machinery except for the propeller or propellers and, possibly, certain propulsion auxiliaries such as forced draft blowers and air heaters.

One significant measure of ship design economy of structure, at least in a. cargo vessel, is the ratio of total deadweight to total displacement. This ratio, which is ice always less than 1.00, tells, in effect, what weight of cargo, fuel, water, stores, etc., can be carried for a given basic or light ship weight, or, conversely, how little weight of ship is required to carry a given weight of cargo, fuel, water, stores, etc. In a cargo ship design having any commercially significant degree of structural economy, the weight of fuel, water, stores, etc., is small compared to the full load cargo weight, ordinarily not in excess of seven percent of it. Accordingly the ratio of total deadweight to total displacement is substantially a measure of the cargo carrying eiiiciency of a ship. The higher the ratio, that is, the closer it comes to 1.00, the greater is the economy of ship structure.

Another significant measure of ship design economy of structure in a cargo vessel is the ratio of net steel weight to weight of cargo carried or capable of being carried. This ratio is not necessarily either greater or less than unity, but as a practical matter it is always less than 1.00. The lower the ratio the greater is the economy of ship structure. i

Unless otherwise defined herein, all terminology relating to ship measurements used in this specification including the claims is to be defined by the following Regulatory Body publications in current effect with the filing of the present application: (l) Load Line Regulations, United States Coast Guard, Treasury Department, Washington, DIC., and (2) Rules for Building & Classifying Steel Vessels, American Bureau of Shipping, New York, N.Y.

The expression ocean-going denotes a vessel qualifying according to the named Regulatory Bodies for foreign and coastwise service, as contrasted to shallow water, inland, or lake service.

The ships length value used with the freeboard tables in publication (l) above is the length between perpendiculars (LBP). This term, used extentively in this specification, is defined in publication (1) above as the length in feet on the summer load waterline from the foreside of the stern to the aft side of the rudder post. Where there is no rudder post, the LBP is measured from the foreside of the stern to the axis of the rudder stock. For vessels with cruiser sterns, the LBP is to be taken as ninety-six (96%) percent of the total length on the designed summer load water line or as the length from the foreside of the stem to the axis of the rudder stock, if that be the greater.

As a first step according to the present invention in achieving a design which is more economical structurally than that of the presupposed ship, especially a liquid cargo ship or tanker, of conventional arrangement and form; i.e., particularly considering the ratio of length of cargo tanks to length between perpendiculars (LGT/LBP) and other parametric ratios to be noted, the length of the ship may be decreased by a relatively small but significant amount, for example, about twelve percent. In the course of this change, given service requirements are desired to remain constant as `follows: hull characteristic of deadweight, and cargo characteristics of density, and, thus, specific volume. Draft lis to remain substantially constant, but since the freeboard requirement is somewhat diminished by the length reduction, the depth of hull may be reduced correspondingly. Now, with the reduced length and with the constants noted, the objective becomes that of altering certain parameters, including beam and block coefiicient, so as to maintain the cargo cubic to accommodate the constant cargo deadweight requirement.

To accomplish this while holding the constants noted, there must be an increase in beam and also an increase in block coefficient, the block coefficient being the ratio of the volume of the underwater body of the ship to the volume of a rectangular prism having the sarne length between perpendiculars and waterline breadth as the ship and a depth equal to the ships draft.

The effect on light ship Weight dueto these dimensional changers involving a reduction in length-to-depth ratio and an increase in beam-to-draft ratio, overwhelmingly the effect on Weight of hull structure or steel Weight,

will be a decrease due directly to the shorteningsof the,l

quirement varies as the square Vof the length and ap-v proximately as the beam and block coeificient to thefirst traditional propulsion machinery space within the ships power, then altogether, the eiects tending to decrease theY .l

Weight of hull structure due tothe shortening will be greater than those tending to increase it due to the Widening and making vmore full, with the net effect being a substantial decrease in steel weight.

The total elfect of the first step geometric changies,'lfV

however, Vand to some` extent an undesirable one, is to provide a lship having not only the original or required cargo deadweight carrying yability .at a reduced steel Weight, but also some additional although practically unuseable ability of this kind. Furthermore, when loaded simply with the required Weight of cargo, the ship willV float at a reduced draft. The beam-to-draft' ratio will thus be increased through both an increase in. beam loaded standard ship. Thus, althoughrthe decrease in and a decrease in draft to a value unacceptably high acf cording to Regulatory Body standards. How this situation comes about is explained in the following two paragraphs.

The initial shortening of the rship is effected essentially entirely in the cargo tank space because'the fore and aft dimensional requirement of the below-deck machinery space is a substantially inflexible one. On the other hand, when beam is increased to restore the required cargo tank capacity this increase is eifected lnot only in Way of the"`ships Yhull cargo tank spaceA itself, but also in way of its propulsion machinery space. YThus with an increase in beam or breadth without a decrease in length the machinery space Within the hull increases. in

volume. yThe addedV machinery space volume is not needed for machinery since no particular change in the ships propulsion power requirements is-contemplated. On the other-hand, this added volume is not practicably useable'for cargo since such usevwould involvefthe installation of rather narrow cargo tanks outboard of they propulsion machinery, an inconvenient arrangement.

The added volume of the machinery space does', however,'contribute to the ships buoyancy, and,`in the present circumstance, contributes unnecessarily because the /bu'oyf yancy associated withV theV cargo tank space has remained essentially unchanged in viewof the maintenance of conl stant volume of this space'. Accordinglywhen the Vship is loaded with the required, predetermined deadweightof cargo Vit Will float at a shallower draft than the original hull is left void of machinery and so becomes available to carry cargo, `that is, to contribute actually to the ships deadweight carrying ability. At this point the dead- Weight capacity of the vessel is'higher than the original value for the standard ship which is desired to be maintained; the draft with the ship loaded to the original deadweight is less than the original full load draft of the standard ship which is desired to be held aty leasty substantially constant, andthe ratio of beam to draft remains unacceptably high. No particular Vchange in Weight of ships structure takes place in the course of the second step. i

To make full use of the former propulsion machinery space for cargo purposes without abandoning or only partially using any previously used cargo spaces, and still maintain an essentially constantV original deadweight capacity, there rnust be a decrease in beam for effecting a reduction. of total volumewithin the hull. This decrease, considered as a third `step toward improving economy of ,structural design, will cause'a further reduction of'steel Weightand so of displacement. Purthermore,the decrease in beam v Will cause an increase in draft of the ship floating iny fully loaded condition, vrestoring this draft to a value at least close lto thatV obtaining Afor the original fully beam effected lin this third and last step will not offset 'fully the increase in beam effected as part of the rst step, it will, both by itself and through ins effect on draft,

.cause the beam-toldraft ratio of the lighter or improved ship to decrease to a value which while higher than that .Y obtaining for the standard'ship is nevertheless quite acceptable according toRegulatory Body requirements.

Block -coecientmay be altered slightly in the course of the third step from itsV value obtaining vat theV ends of the -rst and second steps, possibly being slightly increased therefrom.` lf this increase should. in fact take place it will have. an etfect'of increasing steel Weight and ship displacement. .In total resulhowever, the Veffect .tending yto decrease the Weight. of hullstructure due to thenarrowing in the third step will be appreciably greater Vthan any effect tending to increase .it due to a making more full, With the net third step effect on steel Weight beingy a decrease'. Since steel Weight or light ship Weight lis decreasedv as. a result .ofthe third step change in l .Weight-to-displac'ement ratio and the steel-to-cargo ratio.

, soy

fully loaded standard ship on account ofthe added ma chinery space buoyancy which is available` taken together lWith the reduced steel weight." The ranomaly arises, therefore, of a fully loaded ship which hasradditional cargo Weight carrying capacity, that is, a* ship ywhich cany floatY safelyV and desirably at an increased draft, but

the additional cargo of initially specified ,density to furnish.

this weight cannotrbe brought aboard.V A K Asa second step toward improving economy of .structural design accordingfto the present invention, and asv a step ,toward alleviating disadvantages. created by theV v firststep, they propulsion machinery yis removed from insidethe'shigand atleast part o f'it is installed VVat the'y main `'deck level or higher vWhilerpart ,oftitis' installedA- i.

V outside the hull below thewaterline. K rauyzrati;the`V crease; inV beam.'

The net increase in beam're'sulting from the three-step change indesign just vdescribed Will have an effect toward increasing the'rnetacentric height of the ship. This height is a measurev of transverse or anti-capsizing stability. While metacentric .height must have a positive value, an indelinitely great value of this height is not desirable. This kis because the greater themetacentric height the stiffer Willrbe .a given ship in rolling, that is, the shorter Willr'be the Vrolling period. Aship' characterized by a short rolling period or a snap roll is an uncomfortable one for personnel and one which isy subjected to at least some undue stresses by=high accelerations. Oil tankers in the lightcondition arefprime examples of ships ytending nificant part ofrr'rtlxeV machinery Weightfhovveve'r, there will be :anaccornpanying raising of theships'centerl ,ofv

'gravity and correspondingjreduction in metacentric height vto counter the rincrease in .the height caused by the invvill thus Vnot abe kimpairled.,v

Thecharacteristics of the ship in rolling` It is to be noted from the foregoing that the characteristics of the design of this invention permit the employment of relatively large advantageous beams without the penalties such a procedure would inict upon standard hulls.

ployed in the ship of this invention and still maintain satisfactory llow of Water to the propellers, a dicult accomplishment for the standard hull with large beam and block (Note: Page 902 of Reference B following).

As has been shown; even larger beams (first step) would The overwhelming number of cargo ships built accordbe required for a conventional hull. This plus the proing to traditional design, whether they be dry cargo ships pulsion machinery weight all at the traditional lower of all kinds on the one hand or liquid cargo ships of all location would preclude attaining acceptable metacentric kinds on the other hand, have deadweight-to-displace-v heights. Thus, the basic design employs a parameter ment ratios of less than 080:1. As an example in the beyond the normal boundary `and does so without penalty, 10 case of liquid cargo ships, that is, tankers, reference may but indeed with cumulative advantages. be had to the article (Reference A) Some Aspects of Along with the raising of at least some of the pro- Large Tanker Design by W. O. Nichols, M. L. Rubin, pulsion machinery, it is also within the contemplation of and R. V. Danielson. This article was presented as a the present invention that certain tanks normally located paper at the Annual Meeting of the Society of Naval below a ships main deck will be raised to the main deck Architects and Marine Engineers held on November level or higher. These tanks include those for fuel oil 17-18, 1960, at New York, N. Y., and occupies pages and fresh water, and when filled with the liquids which 743-835 of volume 68 of the Transactions of the Society they are intended to contain represent a considerable of Naval Architects and Marine Engineers (1960). On weight. This weight carried topside will, like that of the pages 804-806 this article presents as an appendix the propulsion machinery, tend to reduce the metacentric 20 essential characteristics of a group of nine modern tankers height and so keep the ship from being unduly stiif in in commercial service ranging from 25,400 to 106,600 rolling. total deadweight tons at design summer free board draft, Raising of at least part of the propulsion machinery and certain data either taken directly or calculated from and the accommodations for some liquids to the main this appendix are given in the following Table I:

Table I ship .AIB'oDEiFGHJ Dwt. (wasn- 25,100 27,000 29,250 29,350 33,150 40,100 07,450 71,300 100,000 32,740 35,100 30,450 37,350 4s, 010 59,150 30, 730 91,510 137,200 0. 775 0. 709 0. 775 0. 770 0. 771 0. 779 0. 778 0. 779 0. 777 13.0 13.1 13.5 14.0 13.9 14.1 13.7 13.7 13.3 2.33 2.52 2.54 2.55 2.04 2.70 2.38 2.61 2.09 ob 0. 75s 0.753 0. 755 0.772 0.772 0. 755 0.799 0. 757 0.794 LcT/LBP 0.009 0. 009 0 522 0 034 0.019 0. 024 0.072 0 059 0. 054

deck level or higher affords to this part of this machinery ln the foregoing tabulation, Dwt. designates total deadand these liquids or their accommodations a fair degree weight in tons; A designates total displacement in tons; of freedom of fore and aft location. By shifting this LBP designates length between perpendieulars; D desigmachinery and these liquids either forward or aft, the nates molded depth from the upper or freeboard deck to longitudinal location of the center of gravity of the ship the keel; B designates molded breadth or beam; H desigmay be shifted also in the corresponding direction. For nates molded draft from the waterline corresponding to a stable ship to be in equilibrium when lioating in still summer freeboard to the keel; Cb designates block co'ei- Water, its center of buoyancy must be on a vertical line cient, and LCT designates the overall length of cargo with its center of gravity. Location of the center of tanks. All length values are, of course, employed with buoyancy is dependent upon the shape of the ships underconsistent units for ratio purposes `as are all weight values. water body which is in turn controlled to at least some Table l extends over a wide range of deadweight values, extent by the shape of the ships Waterplane area, that is, and it is to be observed particularly that no one of the the shape of the area through the ship at the waterline. nine ships making up the tabulated group has a ratio of Shape or configuration of the waterplane area affects the total deadweight to total displacement (DWL/A) greater characteristics of the ship in longitudinal stability or pitchthan 0.779. The smallest value of length-to-depth natio ing. These chanacteristics are also designated generally (LBP/D) is 13.0; the largest value of beam-to-draft ratio as sea kindliness. Certain waterplane shapes are more (B/H) is 2.70; the largest value of block coehicient (Cb) conducive to sea kindliness than others. With a conis 0.799, and the largest value of the ratio of the length of siderable amount of topside machinery and liquid Weight the cargo tanks to the length between perpendiculars shiftable longitudinally in a ship constructed according (LGT/LBP) is 0.672. to the present invention to keep the centers of gravity and The overwhelming number of cargo ships built accordbuoyancy properly aligned, the lwaterplane area and uning to traditional designs, Whether they be dry cargo derwater body of the ship may be shaped to at least some ships of all kinds on the one hand or liquid cargo ships of extent `for the purpose of achieving 1a high degree of sea 60 all kinds on the other hand have ratios of net steel weight kindliness, and hull ethciency in respect of resistance to design cargo weight of greater than 0.200z1. As an characteristics and powering requirements. example in the case of liquid cargo ships, that is, tankers,

In the design, construction, and operation of oil tankers reference may be had to the article (Reference B) Modit has traditionally been a problem to dispose the center ern High Speed Tankers by L. C. Long, J. L. Stevens, I r., of buoyancy sufficiently far forward to avoid excessive and l. T. Tompkins, lr. This article was presented as a trim by the head. This is because of the very full stern paper at the April, 1960, meeting of the Hampton Roads which must be provided on a tanker having its propulsion Section of the Society of Naval Architects and Marine machinery in the customary aft location. In a ship con- Engineers, and occupies pages 887-958 of volume 68 of structed according to the present invention it is possible to the Transactions of the Society of Naval Architects and provide a somewhat less full stern, despite the increase in 70 Marine Engineers (1960). On pages 888 and 889 this beam and block coefficient, and so let the center or" buoyarticle presents in tabular form the essential characteristics ancy have 1a desirable shift forward with .e center of of a group of six modern tankers in commercial service gravity being movable with it through the movement of (none the same as those previously noted from the topside machinery and liquids. Furthermore, these pa- Nichols article) ranging from 19,183 to 66,532 total deadrameters of large beam and block coeiicient may be emweight tons at design summer freeboard draft, and ceralegres tain data eithertaken directly or calculatedrfrom this tabulation #are given in the following Table Il:

Table Il Ship A B C l D I E F DWll. (tous) 19, 183 3B, 911 37, 689 4l 173 60, 615 GG, 532 A (ODS) 25, 510 49, G60 50, 176 52, 302 77, 029 82, 678 Net Steel Weight (110115) 4, 486 8, 379 9, ,574V 8, 759 13, 241 12, S96 Cargo Oil Weight Y Y (tous) 18, 098 37, S96 36, 634 38, 769 56, 257 A62, 174 Net Steel/Cargo.. 0. 248 v0. 221 0. 256 0. 226 0. 235 0. 207 LOT/LBP 0. 565 0. 635 O. 584 0. 631 0. 689 O. 638

Although not as wide as that of Table I, the range of deadweight values over which Table II extends is still a fairlywide one, and one which falls almost entirely within the range of Table I. Hence the tankers represented y.in and by the'two tables fare'in large measure; comparable from table to table. VIt is to be observed particularly that no one of the'six ships making up the tabulated group of Table II has 'a'ratio of net Vsteel weight to ycargo weight less than0.207 'or a ratio of length of cargo tanksl to length between perpendiculars greater than' 0.639.

The ship of this invention is characterized by a ratio of total deadweight to total displacement notless thanV 0.80: 1, yespecially such a ratio in the range from 0.81 :1. to 0.86zl, which represents a high range of this ratio never before attained in self-propelled cargo-carrying vessels for ocean service. It is also characterized by a ratio of net steel weightto cargo weight not in excess of 0.19021,

' switching from conventional materials such as mild steel to highlyy alloyed and high strength steels and using reduced scantlings for this reason onlyor switching to nonferrous materials such as structural aluminum. While such switches, or substitutions might be possible in some cases, the resulting/overall construction costs would exceed those for standard procedure, a-nd a great deal of the especiallyjsuch va ratio in the range from 0.140:1 to

0.180: 1. The combination of ship design features'which permits reduced light ship weight, increased cargo storage capacity, ecient cargo and ship handling, safety, and stability in the ship of this invention may be described generally as follows: a ratio of length between perpendic- Vulars to molded depth (LBP/D) not greater than 13.30: l,

a ratio of molded beam to` molded draft at summer freep i board (B/H) not less than 2.80, ablock coeicient (Cb) Y calculated using length between perpendiculars as the length value not less than 0.80, and la ratio of length of below-deck cargo space, especiallycargo tank space, to length between perpendiculars (LCI/LBP) not less than The preferred embodiment ofV this invention is a ship characterized by the numeiicalfparameters'just Vgiven'and comprising a hull having a main or freeboard deck', a

.prime mover positioned above theV `freeboard deck, and at least one propulsion unit situated below the water line at .A the stern of the ship secured to the exterior surface of the hull. Internally there area pair of fairly closely spaced longitudinal bulkheads runningl substantially the full length y and depth of the vessel, and ydefining between them a centerline 'cofferdam or chamber which may be used to accommodate cargo tank valves, in the case of a tank ship and some auxiliary machinery. g

The hull should have -a hydrodynamicallyefticient stern, such as a scowstern or a destroyer stern. The prime mover, located or on .abovethe freeboarddeck,

possessess means for providing a source'of power to ypropel the ship.. The propulsion unit comprises, generally, a propulsion motor adapted to be energized by the economy achievable'by the present invention would be lost. i

The nature and substance of this invention as Well as its objects and advantages will be more clearly perceived and fully understood by referring to the following description and claims taken in connectionwith the accompanying drawings in which:

FIG. 1 represents an outboard prole'view'of a tanker ,embodying kthe design features of the presentinvention,

some yexternal structure being broken away for purposes or" showing internal'l machinery arrangements, andcertain internal deck and bulkhead Vstructure being shown in dashed outline; Y Y

' FIG. 24 represents a sectional plan View of the tanker of FIG. l just below the freeboard deck taken along line 'v2-2 inv FIG. llooking in the direction of the arrows;

FIG. 3 represents a .transverseA sectional elevation view of the tanker of FIG. l at the midship section taken along line 3-3 of FIG. l looking in the direction of the arrows;

l are located inthe stern superstructure.

Referring now tothe drawings in detail,fy especially FIGSql, 2 and 3 thereof,'a tanker 10 embodying the design features of this invention includes a hull 11 having a bow portion 11a and a stern portion 11b. `The freeboard deck 12 of the tanker is represented by a dashed line in FIG. 1, and certain'upper and lower longitudinal interior passageway decksy or platforms shownin dashed line are designated 13a and 13b. These decks or plat- Yforms areof only very narrow width between longitudinal bulkheads as may be seen most clearly in FIG..3.

A prime movervunit or machinery 4section 14-is disposed Y on or above the freeboardy deck,fpreerably at or near the stern portion 11b of the vessel. Machinery section 14 .serves as the power source for two propulsion units or pods laand 15b located equallyvzportand starboard well belowthe water line 16 at the stern portion 11b of the hull 11. Each propulsion unit is secured to the exteriorrsurface of the hull and, taking unit 15b asr an expower providing means ofthe prime moverunit and means actuated by the propulsion 'motor for propelling the ship. These propelling means are preferably, al-

though notV necessarily, ,coaxially mounted, co-rotating or contra-rotating propellersv oriented to provide conventionally directed thrust (forwardly along the longitudinal laXisof the hull) to drive the ship.; Y

Standardlshipbuilding materials are contemplatedV to be Specitically,fit` is notcontemplated v y l' 23a to improve' maneuverability of thevessel, and also a Y Cllployed lh'fQughOut 111 COHSfuClHg hejhlp '0f the 'stern thruster yineach of-the'propulsion podst'thruster present invention. Y f

that any improvement will be electedfinV deadweight-toample, comprises a pair oivcoaxially-mounted, contrakrotating or c'o-rotating/'propellers 17 and`18 driven by a vmotor device 11139;` The power to drive motor device 19 itself is brought to propulsion unit 15b by appropriate power transmission means 20. Similar means, of course, extend* to'uriit15a.`V Motor device 19 in propulsion unit 15b may be onefthat 'is-'energizedby'steam, compressed gas, 'or hydraulic huid, Vas Well' as rby electricity.'

The stern portionv 11b of the'lhull is designed with a hat bottom 21 extending upwardly from Vthe keel 22 of the:` ship'10,suclflf designfusuailybeing designated as a scow type'stern. Propulsion'units laand y15b are preferably secured tohull 11 on'the -flat bottomportion V`of the sternl and ,orientedfto provide thrust along the Vfore-Qanl-iaft orjflongitudinal axisoi the ship;V Hull 11 may also be provided with a bow nodule or bowthruster asbin pedrsb beingshown; Y

TankerV 10 includes Aa superstructure*section24, that'is, a section at andabove the level of thermain orfreeboard tank spaces 25 for carrying fresh water.

yfor example, for cleaning the cargo tanks.

fi deck 12, which comprises various bridges and boat decks. Additionally, and in particular, it comprises structural The whole section 24 may be located more or less amidships or as desired to suit design conditions. The forward perpendicular (EP.) and the aft perpendicular (AP.) are indicated in FIG. l at locations consistent with Regulatory Body determinations given earlier in this specification. The distance between these perpendiculars is the vessels lengt-h between perpendiculars (LBP).

Tanker is also provided with a very important internal design feature most clearly apparent in FlGS. 2 and 3. This is the provision of longitudinal bulkheads 25 .and 27 extending all the way from the forward peak bulkhead 28 to the stern of the ship. The two longitudinal bulkheads are essentially equally offset port and starboard from the longitudinal centerline of the ship, and extend the full depth of the ship from the main strength deck 12 to the keel 22. Their lateral or transverse spacing is not more than about ten percent of the beam of 4tanker 10 at its midship section. Otherwise the tanker is of `typical longitudinally framed construction employing heavy transverse webs such as 29a with large open regions as shown in FIG. 3, although not in FIG. 2, between Atransverse bulkheads 2% of which at least every other one is liquid tight.

ln a ship having the pr-ime mover unit above the freeiboard deck and separated from the propulsion units a and 15b located at stern 1lb, the dou-ble bulkhead construction provides a space 3) for the` routing of feeder .caibles 26 or other power transmission means down from machinery section 14, as well as space for cargo handling machinery, not shown. Specifically in the case of a liquid cargo ship such as tanker lil, the space between bulkheads 26 and 27 can serve as a cargo pump room. Throughout the ship, therefore, substantially all auxiliary machinery, power cables, cargo valves, cargo piping and the like can be concentrated in the space or longitudinal colferdam 30 between lbulkheads Z6 and 27, thereby removing these items from regions otherwise used for cargo storage, and in particular making valves more accessible and piping runs shorter than in the conventional tanker design. With increased concentration of auxiliary equipment, the amenabili-ty of this equipment to reliable and economical centralized control and/ or automation is enhanced. Likewise there will be great convenience in having the upper and lower internal longitudinal platforms 13a and 13b. Continuous internal access through the vessel may be provided by liquid-tight doors in the transverse bulkheads at the platform levels.

The location of machinery section i4 and structural fresh water tanks 25 at and above the freeboard deck and propulsion units 15a and 15b outside of the hull frees the interior of the hull of the cubic requirements of this equipment and structure. Tank sections 3io through 3th (port) and tank sections 32a through 32h (starboard) f which provide the cargo and, if necessary, some ballast carrying capability of ship 10 extend throughout the very substantially greater part of the length of the hull ll. By use of non-tight transverse bulkheads, combinations for filling and discharge purposes may be made of tank spaces 31a and Slb, 3c and 31d, 31e and lf, lg and Slh, 32a and 32b, 32e and 32d, 32e and 321, and 32g and 32h. The total length of the below-deck tank space, that is, the tank space length extending from the forward bulkhead of space 31a (or 32a) to the aft bulkhead of space Blk (or 32h), is designated LCT in FIG. 2.

.Directly aft of the cargo spaces within the hull are fuel oil tanks 33 and 34 and salt water ballast tanks 353' and 3d, and still farther aft are ballast tanks 37 and 33. Located Lbetween these ball-ast tanks on the outside and longitudinal bulkheads Z6 and 27 on the inside are washdown tanks 39 and 40. These tanks may be adapted to contain washing materials, fresh water and detergent-water mixture, Aft of the l0 washdown tanks but still between ballast tanks 37 and 3d is steering engine space 41.

At the forward bulkhead of the steering engine space the longitudinal bulkheads 26 and 27 go out of contact with the underside of freeboard deck 12, and decrease in height from their normal upper edges `by an amount equal to the height of the steering engine space. Below this space these bulkheads continue all the way to the stern of the ship, and the rotating rudder stock passes down between them. The deck of steering engine space 41 is at the same level as upper platform 13a between the longitudinal bulkheads. Directly forward of the cargo tank spaces are forward salt water ballast tank 42 and chain lockers 43 and 44.

The hull 11 of the tanker 10 shown in the drawings possesses several features, briefly noted above, which, together with reduced structural weight and, conversely, increased dead-weight for a given displacement, provide a vessel with exceptional stability and elciency. The hull itself is of relatively reduced length and relatively increased beam compared with the hulls of cargo ships of conventional design. Generally, it may be stated that the hull of a ship having the design features of the present invention has a ratio of length between perpendiculars to molded depth (LBP/D) not greater than l3.30:1, especially such a ratio in the range from 11.5011 to 13.00:1; a ratio of molded beam to molded draft at' summer freeboard (B/H) not less than 280:1, especially such a ratio in the range from 290:1 to 3.10:1; a block coeflcient (Cb) calculated using length 'between perpendiculars as the length value not less than 0.80, especially such a coefficient in the range from 0.81 to 0.85, and, particularly in the case of a tank ship, a ratio of length of belowdeck cargo space to length between perpendiculars (LGT/LBP) not less than 070:1, especially such a ratio in the range from 070:1 to 0.82: 1. This design will reduce the frictional resistance as the vessel moves through the water on account of reduced wetted hull surface area, and will increase the transverse stability of the ship to render safely practicable the above-deck location of at least part of the propulsion machinery and some substantial liquid weights.

A flat horizontal fbottom representing a lateral extension of keel 22 obtains over the greater part of the length of the hull l1. At the location 45 (an imaginary line athwartships), the flat horizontal bottom surface slopes upwardly and rearwardly in a continuous flat although not horizontal surface characteristic of a scow-type stern. The upward slope continues to a position above a rudder i6 where a transom 47 constitutes the extreme stern surface of the vessel l0. Forward of position 45 and aft of position i8 the sides 49 vand 50 are substantially flat and parallel and are disposed approximately vertically. Aft of position 4S the sides i9 and 50 converge as shown in FlG. 2. Such convergence minimizes inward induction of the water llow toward the stern and therefore also minimizes cavitation, since inwardly flowing water under these conditions entrains great quantities of air. The location of propulsion units 15a and 15b under the flat, upwardly sloping surface 21 of stern portion 11b is optimal since the region in which the co-axial propellers of each propulsion unit are to operate according to this design is one in which the water is substantially free of entrained air.

Beyond improving the efficiency of the propulsion system, the scow-type construction oers the additional advantage of making a greater portion of cubic within the hull available to cargo. Thus, the substantially rectangular cross section of the hull is maintained throughout its length, and only aft of position 45 is the depth of the hull varied. Furthermore, with the scow-type construction, the sloping bottom 21 of the stern provides a plane surface under which the propulsion units can be conveniently mounted. The angle of the sloping bottom 21 with respect to the horizontal keel or bottom 22 can be amidships location of the vessel, or it may also be located In some dey adjacent or within the superstructure 24. signs, it may be desirable to position the superstructure 24 appreciablytoward the bow with the machinery section 14 located amidships.

construction of the machinery section 14 and the super-y In any event, as a result of the unit structure 24, the designer is free yto position these assemblies along the longitudinal axis ot the hull in order tol position the longitudinal center of gravity atthe optimumr position for a given hull construction and its attendant 'longitudinal center of buoyancy location. Thus, the hull can be designed to provide the optimum requirements for i resistance to sea motion and for stability; and then, subsequently, the package or unit of themachinery section 14 `and superstructure 24 can be positioned along the hull in order to obtain a compatible location of the longitudinal center of gravity thereby providing the proper trim.-

Proper positioning of the machinery section 14 and superstructure 24 y(with its living quarters, operational'V stathereby eifecting the least Istress. and strainon the ship Vconsidered as a girder. *i r .y

In constructing a new ship or in vmodifying an existing kone, the structures including the prime mover unit or `machinery section 14, and the pod propulsion units 15a and 15b, can be fabricated separately from the hull of the ship. Similarly-the superstructure 24 can be constructed with the prime mover unit independently ofthe hull. ,Regardless of whether the hull` is to bel adapted for the-carrying ofcontainers,-vehicles, bulk dry cargo,

liquid cargo, V'or mixed bulk and dry cargo, the package including the machinery `section 1li,v and superstructure 24 can be installed upon the hull 11 to provide the proper trim function. The package arrangement, including the pods, has the further advantageof enabling a degree of a package of a given design .may be used with a variety of hull types. v g i The machinerysection 11i contains an appropriate prime mover, such as a gas turbine engine 51, which may inco-axially mounted propellers 17 and 18. Electrical power i from `the prime mover unit is delivered to the motors by tions,` etc.) also allowsfor posturing the load on the ship Y Yin order to obtain the optimum bending moment, and

standardization to.` be provided in` ship construction since clude an air compressor dito Voperatepauxiliary equipment. A turbine output jshaft' 53 drives electric genera-i 'tors 5ft and 55, the current from which is carried to the propulsion units 15a and V15b by feederv cables `after passage through a power Control unit 56.A

Auxiliaryrmachiuery associated with ship propulsion and control (as distinguished fromrcargo handling) such as pumps, standby power Asu"p,pliesetc., may also be installedin the machinery sectionli. v `With Vthis arrange-V ment, the Vspaces and platformsl Within the hull are essentialiy entirely `free of propulsionmachinery'and propulsiony auxiliaries. The only such equipment passing through or located within the hull and itsplatforms is that of Vfeeder cables to the propulsion V,units-15a andv 15b.' ofcourse,v the hull does contain the steering engine and related equipment associated-with ship control. Fuel forgthegas turbine engine 51 is ystored in tanks 33 and 34 vadjacent the machinery section leso'that fuel piping runs from these.k tanks to this-engine are quite short. WVThe superstructure section 24 Vcontains a plurality of decks 24a,124b,24c, etc., upon which are located stateroornsfandV the operations rooms and compartments used Vfor navigation and control of the vessel. i

The propulsion uniti175277,:takrmV asexemplary, includes a housing 57 inwhich are mounted Vone-or more propul-I` sionmotors'. 19 connected byV av drive; shaft 58' to -areduction v"gear 59.1 Co-axial propeller Vshafts eti extend from,VV fthe reduction "gear 't-hrougha shatbearing to V*the two 0 and starboard tank portions.

. l rSummer Ireeboard;

vmeans of-feeder cables 20. Where the propulsion motor or motors can operate vat propeller shaft speed, the reduction gear 59 may be eliminated and direct drive employed. With the package or unit arrangement, the propulsion unit 15b is secured to the stern surface 21 of the hull 11, and may be replaced by another unit Without irnmobilizing the vessel for an extended time. Each propulsion unit may be streamlined by providing it with a substantially circular or elliptical cross section and with fairings between the major body portion of the housing ''and surface 21 in order to permit the proper flow of waterv to the propellers, and thus 'gain a propulsive ei-V it Vis, clear that additional space in the interior of the hull is available for cargostowage.y y Y Y Referring next to FIGS. 4, 5, kand 6, a tanker constructed according to the present invention' hasy a hull 111 having a main Vor freeboard deck 112, and on which there is mounted amidships or forward superstructure section 124- and an `aft superstructure section including `a machinery section 114. H'Within the midships superstructure section on a-tank deck, there are structural fuel oil tanks 133m through 1331 (port) and 134a through 1341 (starboard). Within the aft-superstructure section there are structural freshwater tanks a, 125b, `and 125C. These tanks Vmay beappropriately divided individually into port Otherwise tanker 110 is similar in all essential respects to tanker 10 shown in FIGS. 1,2, andk 3` so far as having incorporated within its design the various-features and advantages particularly characv teristic of and deriving from the present invention.

vspeciiic measurements for standard tanker FIof Table Il, this tanker having a totaldeadweight carrying capacity ofA 66,532 tons. The seconddata column sets forth the corresponding parametric values and specic measure- -rnents for a tanker designed according to this invention to have the same-total deadweight of 66,532 tons as the standard ship taken as apreference, with a hull that is n shorter by about twelve percent (LBP reduced from 770 Vft.-l0 in. to 675ft.,'0 in).

, tanker,l of course, ,essentially .none of the propulsion In the case of the inventive machinery is located within rthe structural hull.

Table `IIl f Standard lnveutive Ship 4 Tanker Tanker,

,A (Ship F, VComparable Table II) Dwt.

LBP (ft.in.) 70-1 e B, molded (ft-in 7104-g D,'rnolded (fn-iu 60-0 55-0 H, molded (ft.in).1 44-7 114-4 Cb 0. 806 2 0. 835 492-0 505-0 2, 631, 500 2, 631, 500 2. 33 3. 00 12V S5 l2. 27 0. 638 0. 750 12, 896 8, 950 16, 146 12, C00 62'174 62, 174 05, 532 66, 532 82, 678 78, 532 0. 805 0. 845 0. 207 0. 144

2 Calculated using DB1 as length dimension.V f

Considering particularlythe: last three'V rows ofidata,` f rtjwillibe seen tirstrof allthat theinventive orprototype ftanker. ha

total displacementwhichris aboutiive perycent less; than that-of the standard ship .(A-lred'uced, from 82,678 tonsfto'7r8,53p2,tons). @This reductin'indisplace- Y ment is due to a reduction in light ship weight, predominantly in steel weight (net steel weight reduced from 12,896 tons to 8,950 tons), since total deadweight has been held constant. There has been about a five percent increase and hence improvement in the ratio of total deadweight to total displacement calculated on the basis of the original value of this ratio. (Dwi/A increased from 10.805 to 0.845). Furthermore, there has been about a thirty percent decrease and hence improvement in :the ratio of net steel weight to cargo oil weight (Net Steel/Cargo decreased from 0.207 to 0.144). With respect to the selected standard ship of Table lll, therefore, the inventive or prototype ship is indeed a ship of reduced structural weight for given cargo weight carrying capacity, just according to the title of this invention. Conversely, with respect to standard tankers of approximately equivalent length and steel hull weight such as hulls C and D of Reference B, the inventive for prototype ship has a startling superiority in cargo carrying ability.

Protection by Letters Patent of the present invention in all its aspects as the same are set forth in the appended claims is sought to the broadest extent that the prior art allows.

What is claimed is:

1. A self-propelled ocean-going surface cargo ship having a ratio of total deadweig'ht to total displacement of at least 080:1 and comprising a hull which is characterized by (1) a ratio of length between perpendiculars to molded depth not greater than 13.30:1 :and (2) a ratio of molded beam to molded draft at summer freeboard not less than 280:1, essentially all of the pro-pulsion ma chinery of said ship being located outside of said hull and including a prime mover unit which is substantially xedly attached to said hull and derives buoyant support therefrom.

2. A self-propelled ocean-going surface cargo ship according to claim 1 which has a ratio of net steel weight 'to full load cargo weight not greater than 0.190r1.

3. A self-propelled ocean-going surface cargo ship according to claim `1 which has a ratio of net steel weight to -full load cargo weight vin the range from 0.140:1 to 0.180:1.

4. A self-propelled ocean-going surface cargo ship having a ratio of total deadweight to total displacement of at least 080:1 and comprising a hull which is characterized by (-1) a ratio of length between perpendiculars to molded depth not greater than 13.30:1, (2) a ratio of molded beam to molded draft at summer freeboard not less than 2.80: 1, and (3) a block coefficient not less than 0.80, essentially all of the propulsion machinery of said ship being located outside of said hull and including a prime mover unit which is substantially xedly attached to said hull and derives buoyant support therefrom.

5. A self-propelled ocean-going surface cargo ship according to claim 4 having a ratio of total deadweight to total displacement in the range from 081:1 to 0.86: 1.

6. A self-propelled ocean-going surface cargo ship according to claim 4 in which the hull is characterized by a ratio of length between perpendiculars to molded depth in the range from 11.50:1 to 13.00: 1. k7. A self-propelled :ocean-going surface cargo ship according to claim 4 in which the hull is characterized by a ratio of molded beam to molded draft at summer y freeboard in the range from 2.9011 to 3.1021.

k a ratio of length of below-deck cargo tank space to length between perpendiculars not less than 0.7011, and essentially all of the propulsion machinery of said ship being located outside of said hull vand Vincluding a prime mover unit which is substantially fixedly attached to said hull and derives buoyant support therefrom.

10. A self-propelled ocean-going surface tank ship for the carriage of liquid cargoes according to claim 9 in which the huil is characterized by `a ratio of length of below-deck cargo tank space to length between perpendiculars in the range from 0.70:1 to 0.82: 1.

11. A selfpropelled ocean-going surface tank ship for the carriage of liquid cargoes, said ship having a ratio of net steel weight to full 'load cargo weight not greater than 0.19011 and comprising a hull which is characterized by a ratio of length of below-deck cargo tank space to length between perpendiculars not less than 0.70: 1, and essentially all of the Ipropulsion machinery of said ship being located outside of said hull and including a prime mover unit which is substantially xedly attached to said hull and derives buoyant support therefrom.

12. A self-propelled ocean-going surface tank ship for the carriage of liquid cargoes according to claim 11 in which the hull is characterized by a ratio of length of below-deck cargo tank space to length between perpendiculars in the range from 0.70: 1 to 0.82: 1.

13. A self-propelled ocean-going surface cargo ship having a ratio of total deadweight to total displacement of at least 0.8011 and comprising (1) a 'hull having a freeboard deck and characterized by (i) a ratio of length between perpendiculars to molded depth not greater than 13.3011, (ii) a ratio of molded beam to molded draft at summer freeboard not less than 280:1, and a vblock coefficient not less than 0.80; (2) a prime mover unit positioned at a level at least as high as that of the freeboard deck, said prime mover unit having means for providing a source of energy to propel the ship, and (3) at least one propulsion unit located below the water 'line at the stern of the ship and secured to the exterior surface of said hull, said propulsion unit comprising (i) a propulsion -motor adapted to be energized by said energy providing means and (ii) propulsion means actuated by said propulsion motor for propelling the ship.

14. A self-propelled ocean-going surface cargo ship according to claim 13 further comprising structural fuel oil tanks for said prime mover located at a level at least as high as that of the freeboard deck.

15. A self-propelled ocean-going surface cargo ship according to claim 13 further comprising structural fresh water tanks located at a level at least as high as that of the freeb'oard deck.

16. A self-propelled ocean-going surface cargo ship having a ratio of total deadweight to total displacement of atleast 080:1 and comprising (1) a hull having a freeboard deck and a scow-type stern, (2) a prime. mover unit kpositioned at a level at least as high as that of the freeboard deck, said prime mover unit having means for providing a source of energy to propel the ship, and (3) at least one propulsion unit located below the water line at the stern of the ship and secured to the exterior surface of said hull, said propulsion unit comprising (i) a propulsion motor adapted to be energized by said energy providing means, (ii) at least one pair of coaxially mounted propellers, and (iii) means for transmitting power from sa-id propulsion motor to said propellers.

17. A self-propelled ocean-going surface cargo ship having a ratio of total deadweight to total displacement of at least 080:1 and comprising (l) a hull having a freeboard deck and a scow-type stern and characterized by (i) a ratio of length between perpendiculars to molded depth not greater than 13.30: 1, (ii) a ratio of molded beam to molded draft at surnrner freeboard not less than 280:1, and (iii) a block coefficient not less than 0.80; (2) aprime mover unit positioned at a level at least as high as that 'of the freeboard deck, said prime mover unit having means for providing a source of energy to propel the ship, and (3) at least one propulsion unit located below the water line at the stern `of the ship and secured to the exterior surface of said hull, said propulsion unit comprising (i) a housing, (ii) a propulsion motor within said housing adapted to be energized by said -energy providing means,

(iii) at least one pair of coaxially-mounted contr'a-,rotat` ing propellers exterior to said housing and orientedV toA provide thrust along the longitudinal axis' of said ship,y

having a ratio `of total deadweight to total displacement v of at least 0.8011 and comprising l(1) a hull having a freeboard deck and characterizedV by (i) la ratio of length between perpendiculars to molded depth not greater than 13.3021, (zi) ak ratio of molded beam t'o molded draft at summer freeboard not less than 2.80: 1, and (iii) a block coeflicient not less .than 0.80; (2) a prime mover unit positioned at a level at least as high as that of the freeboard deck near the stern of the ship, said prime mover unit having means for providing a source of energy to propel the ship, and (3) at least one propulsion unitplocated below the water line at the stern of the ship and secured to the exterior surface of said hull notflower than a horizontal plane passing through the keel thereof, said propul-A sion unit comprising a housing, (z'i).a propulsion' tno-- torwithin said housing adapted to beenerg'ized by said ener-gy providing means, (z'z') at least oneV pair of co-rotating propellers oriented to provide thrust along the longitudinal axis of the ship, and (iv) means for transmitting power from said propulsion motor. to v'said :co-rotating propellers. v

19. A self-propelled ocean-goingV surface cargo ship having a ratio of total deadweight to total displacement tudinal ,centerline plane ythrough said hull, :and defining an open lspace between them having a width of not more than about ten percentof the beamof the ship at its midship section, (3) aplurality of tank spaces defined outboard of said bulkheads between Vthese bulkheads and the hull, these tank spacesbeing adapted to receive liquid cargo and the ratio of the length of the hull through which said tank spaces extend to the length between perpendicula-rs thereofcbeingy not less than 0.70: l, (4) la pnirne moverunit positioned atV a level atleast as high as that of the freel board deck, said prime mover'unit having means for providing a source of energy to propel the ship, (5) at least g one propulsion unit located below the Ywater Vline at the stern of the ship and secured tothe exterior surface of said hullsaid propulsion unit comprising (i) a propulsion motor :adapted to be energized by saidv energy providing means and (ii) propulsion means actu-ated by said pro- Vpulsion'motor for propelling said ship, and (6) means extending lthrough the space between said bulkheads for transmitting. power from said prime mover unit to said propulsion unit. v f

22. A 'self-propelled; surface cargo ship of reduced y 1 structural weight for given cargo weight carrying capacity, l said ship comprising (l) a hull havingA a freeboard deck,

of `at least 0.8021 andcomprising (l) a hullhaving a free- Y board deck and characterized by -a ratio yof length between perpendiculars to molded depth notr greater than 13.3021, (ii) a yratio of molded beam to molded draft at summer freeboard not less than 2.80: 1, and (iii) a block coeflicientl not less than 0.80; (2);a pair of bulkheads within said hull extending longitudinally for substantially. the full length of the hull and vertically for substantially the full depth of the hull, said bulkheadsbeing fairly closely spaced and defining an open space between them, v(3) 4a plurality of tank spaces defined outboard of said bulkheads betweenv these bulkheads and the hull, these tank spaces being' (2) at least one pair o'fzbulkheads within said hull extending longitudinally for substantially the entireV length of the hull VandV vertically for substantially the entire depth of the hull, said bulkheadsbei-ng fairly closely ,spaced in 'respect ofl the overall `beamjoflthe hull and defining an fopen space between them and cargo spaces on both sides of thepair of them, (3v) a prime mover vunit'positioned at a levelat least'as high asl that of the freeboard deck, said prime mover unit having means for providing a source of energy to propel the ship, (4) at least one propulsion unit extending from the exterior of said hull below the water line but not lower` than the'keel line thereof, saidpropuladapted to receive liquid cargo, (4) a prime mover unit v i positioned at a level atleast as high as that of the freeboard deck, said `prime mover unit having means yfor providing a source of energy to propel the ship, (5) at,V least one propulsion unit located below the water line' at j the sternr of ship and secured to the exterior surface of said hull, said propulsion unit being adapted to be energized'by said energy providing meansand (6) means for` transmitting power from Vsaid prime mover unitfto saidv propulsion unit. i Y 20. A self-propelledocean-going surface tank ship Vfor n the carriage of liquidcargoes, said ship comprising (1)- yaVV hull having a freeboard deck and characterized by,V a'ratio sion unit comprising (i) at least one propulsion motor adapted to be. energized by saidv energy providing means and (ii) propulsion meansf actuated by said propulsion 4.0

mot-or for propelling the ship, and (5) power transmitting ymeans extending from said energy providing meansto said propulsion unit. i V23. AHsel-propelled' surface cargo .ship vof reduced `vstructural weight for given cargo weight'carrying capacity,

said ship comprising (l) a hull having a vtreeboard deck, (2)3.'y pair of -bulkheads within said hull` extending longiztudinally for substantially the entire lengthof Vthe hull i and vertically for substantially/'the entire depth'y of the hull,

saidfgbulkheads vbeing fairly closely spaced in `respect of the overall beam of the hull on either side o'a vertical longitudinalcenterlineplane through thefhull and defining anopen space between them, (3) a plurality of .bulki heads extendingtr-ansversely within said hull and` dening a'pluralityiof longitudinally'garrayed cargospaces outkof length? of below-deck cargo tank space toflength be- Y tween perpendiculars not Vlessthan 0.70:'1, (2) aprirne mover unit positionedV at a 'level at least as high yas that ofV the freeboard` deck, said. prime mover .unite having .board yofthe longitudinallyl extending bulkheads between these bulkheads and the` hull, ythese cargo spaces being adapted to receiveV liquid'k bulk cargo and in the aggregate on either side of `said pairi'ofbulkheadsoccupying the means for providing la source of energy to propel the ship,

yand (3) at least'one propulsion unit located; below the ywater line at the sternoftne ship and secured'to the exconsiderably greater part of the lengthof the vhull aswell as individuallyvextending substantially the full depth thereon (4)2 vaprirne mover unit positioned at a level at V'le-ast, ashighasrthatof. the "freeboard deck, said prime mover Vunit having means `for providing a'source 'of energy terior surface of said hull, said propulsion unit comprising (i) `a propulsion motor adapted' to begenergizedl by.y said energy providing'means and (ii) propulsion'means,v actuated by said propulsionfmotor for propelling said .v Y

' f Y adaptedite-bie energized byfsaidenergy providing Ymeans [and ,('ii)" propulsion means actuated by Vsaid piopulsion lmotor forpfropelling the ship, and (6) powertrans'mitting meansv extendingffrornsaid energy providin'glmeans to 'said propulsion uniti" -V Y 'y 21. A self-propelled ocean-going surfacetankshipffor the carriage of liquid cargoes, said shipV comprisingv (l) a hull havingY a freeboa-rd deck, (2) a pair of bulkheads j lwithin said 4hull extending longitudinally for substantially' thefull Ylength ofthe hull and #vertically for substantially the'full depthiofthe hull, s'aid'bulkheards" being 'substanf Y tially equally andy oppositely offset trema vertical'longi Vfto propelgthegship,(5)" at least onek propulsion Vunit ex- VVtendingV from.theexter ior of saidhull belowl the water "'linef but notIlowe'r than'the keel line? thereof,v said propulsionunit comprising (i)-lat least one propulsion'motor pacity, saidV ship Vcomprising (i )fa hullhaving (Die freeg 17 board deck and (ii) a stern portion of substantially rectangular vertical cross section at its forward end and having a substantially at bottom surface extending yrearwardly in an upwardly inclined direction from the lower edge of said forward e-nd and further having substantially vertical and rearwardly converging side surfaces, (2) la prime mover unit positioned at `a level at least as high as that of said freeboard deck, said prime mover unit having means for providing .a source of energy to propel the ship, (3) at least one propulsion unit extending rearwardly from the upwardly inclined bottom surface of the stern portion of said hull below the water line but not lower than the keel line thereof, said propulsion unit comprising (i) at least one propulsion motor `adapted to be energized 18 by said energy providing means and (ii) propulsion means actuated by said propulsion motor for propelling the ship, and (4) power transmitting means extending from said energy providing means to said propulsion unit.

References Cited in the le of this patent UNITED STATES PATENTS 2,283,291 Selden a- May 19, 1942 2,727,485 Combs Dec. 20, H955 3,063,394 Rebikoff Nov. 13, 1962 3,085,533 Goryl Apr. 16, 1963 FOREIGN PATENTS 906,518 France May 22, 1945 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noa 3V 1627 169 December 22 1964 Nathaniel James Ferris It is hereby certified that error appears in the above number-ed patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6V line 22 for Tree boafd" read freeboard Ng column lOW line I8V for "olead-welght"` read M deadweight --5 column l2,l Table IIL, third column,7 line 4 thereof,7 for WIT-4"' read 40-4 eg column l5 line 33V after bym insert (i) mg line 49 after "of', first oocumenoe insert the --g Column 18 line 11 for 'Gonyl"l read Goryl et al.

Signed and sealed this 27th day of April 1965 (SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attestng Officer Commissioner of Patents

Claims (1)

1. A SELF-PROPELLED OCEAN-GOING SURFACE CARGO SHIP HAVING A RATIO OF TOTAL DEADWEIGHT TO TOTAL DISPLACEMENT OF AT LEAST 0.80: 1 AND COMPRISING A HULL WHICH IS CHARACTERIZED BY (1) A RATIO OF LENGTH BETWEEN PERPENDICULARS TO MOLDED DEPTH NOT GREATER THAN 13.30:1 AND (2) A RATIO OF MOLDED BEAM TO MOLDED DRAFT AT SUMMER FREEBOARD NOT LESS THAN 2.80:1, ESSENTIALLY ALL OF THE PROPULSION MACHINERY OF SAID SHIP BEING LOCATED OUTSIDE OF SAID HULL AND INCLUDING A PRIME MOVER UNIT WHICH IS SUBSTANTIALLY FIXEDLY ATTACHED TO SAID HULL AND DERIVES BOUYANT SUPPORT THEREFROM.

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