bluuebunny/crossref_metadata_2025 huggingface dataset:
Net and Gross Thrust in Waterjet Propulsion
Authors: Eslamdoost Arash , Larsson Lars , Bensow Rickard
Published: January 2021

The measurement of the net thrust of a waterjet unit is a cumbersome task and thus as an alternative, the thrust of the waterjet system is expressed based on the momentum flux change through the waterjet unit, called gross thrust. The relation between net thrust and gross thrust is not fully understood, and in the current paper this relation is investigated by employing numerical simulations of the flow around a planing waterjet propelled hull. The validation of the bare hull and self-propelled hull simulations is carried out through comparison of the computed results with experimental data.
Implementation of Linear Potential-Flow Theory in the 6DOF Coupled Simulation of Ship Collision and Grounding Accidents
Authors: Yu Zhaolong , Shen Yugao , Amdahl Jørgen , Greco Marilena
Published: January 2021

Ship collisions and groundings are highly nonlinear and transient, coupled dynamic processes involving large structural deformations and fluid structure interactions. It has long been difficult to include all effects in one simulation. By taking advantage of the user-defined load subroutine and the user common variable, this article implements a model of hydrodynamic loads based on linear potential-flow theory into the nonlinear finite element code LS-DYNA, facilitating a fully coupled six degrees of freedom (6DOF) dynamic simulation of ship collision and grounding accidents. Potential-flow theory both with and without considering the forward speed effect is implemented for studying the speed influence. With the proposed model, transient effects of the fluid, global ship motions, impact forces, and structural damage can all be predicted with high accuracy. To the authors' knowledge, this is the first time the fully coupled 6DOF collision and grounding simulations are carried out with linear hydrodynamic loads for transient conditions but without simplification of collision forces. The proposed method is applied to calculations of an offshore supply vessel colliding with a rigid plate and with a submersible platform. The results are compared with a decoupled method and discussed with emphasis on the influence of different initial velocities. The proposed method is capable of predicting both the 6DOF ship motions and structural damage simultaneously with good efficiency and accuracy; hence, it will be a very promising tool in the application to ship collision and grounding analysis.
Physics-Based Design by Optimization of Unconventional Supercavitating Hydrofoils
Authors: Vernengo Giuliano , Bonfiglio Luca , Gaggero Stefano , Brizzolara Stefano
Published: January 2021

A computational framework to design a new family of unconventional super cavitating (SC) hydrofoils with optimized hydrodynamic performance is developed. A low-order boundary element method is used to solve for the steady potential flow over the hydrofoil predicting its hydrodynamic characteristics, including the vapor-cavity interface. Shape variations are obtained by an ad hoc parametrization scheme by composite B-spline curves whose control points represent the design variables to the hydrodynamic optimization problem. The accuracy of the Computational Fluid Dynamics (CFD) tools is also preventively validated on the experimental characteristics of a conventional SC hydrofoil. A computational test case is performed to maximize the efficiency of a SC hydrofoil accounting for both shape and angle of attack variations. The new hydrofoil leads to 40% improvement on the lift over drag ratio compared to the initial reference shape. This result is confirmed by high-fidelity unsteady multiphase viscous solver.
Influence of Design Parameter Variations for Propeller-Boss-Cap-Fins on Hub Vortex Reduction
Authors: Seo Jeonghwa , Lee Seung-Jae , Han Bumwoo , Rhee Shin Hyung
Published: January 2021

The present study aimed to identify significant design parameters on the propeller open water efficiency and characteristics of the wake field of a propeller with propeller-boss-cap-fins (PBCFs), with special attention to hub vortex dynamics. A towed underwater stereoscopic particle image velocimetry system was used to measure the near wake fields of a five-bladed propeller and a PBCF model. Through model tests, it was confirmed that the disappearance of a low-pressure area behind a boss cap, i.e., a reduction of the hub vortex, was the dominant contribution to open water efficiency gains from PBCF rather than a decrease in net torque. Global force and wake fields were also measured in response to design parameter variations of PBCF, i.e., fin chord length, fin span height, pitch angle, and phase lag. In the cases of pitch angle and fin chord length variations, PBCF with a light loading configuration had better open water efficiency than the baseline PBCF. However, in the case of a short fin span height for light loading configuration, the hub vortex was not entirely prevented, and the total open water efficiency decreased. Under heavy loading configurations, excessive negative and torque degraded the open water efficiency. Phase lag variations were less effective with respect to the open water efficiency than other design parameter variations.
Numerical Statistical Estimates of Ship Broaching-To
Authors: Spyrou K. J. , Themelis N. , Kontolefas I.
Published: January 2021

Ship "high-run" incidents in irregular following/quartering seas, in particular their correlation with broaching-to behavior, are investigated, aiming to produce statistical evidence about this connection. A simple linear mathematical model of the yaw and sway motions has been combined with a nonlinear surge equation that is often applied in surf-riding investigations, considering multifrequency wave excitation derived from a spectrum. Types of yaw instability are conjectured from the structure of the mathematical model. The concept of instantaneous celerity is used for formally recognizing the occurrence of high-run and a simple method is proposed for its calculation. Problem's rarity (i.e., whether few only or a large number of broaching-to incidents are recorded during long-time simulations) is controlled by using the rudder control gains as "rarity knobs." Expectations of broaching-to, with and without conditioning on high-run incidence, are presented. Histograms of cumulative time of high-run and limiting yaw angle exceedance are produced and the fitting of standard distributions, variants of the normal distribution, are discussed.
Performance Study of Three-Phase Fault-Tolerant Permanent Magnet Motor Drive for Marine Propulsion System Based on Structure Design
Authors: Bai Hongfen , Zhu Jingwei , Quin Jungfeng
Published: January 2021

The fault-tolerant permanent magnet motor (FTPMM) drives are desired in electric ship propulsion systems. The winding inductance, the sinusoidal degree of the back electromotive force (back-EMF) waveform, and the total harmonic distortion (THD) of the cogging torque are the important factors that affect the operating performance of FTPMM drive. A performance optimization of a three-phase FTPMM by varying motor structural parameters is presented in this article. By analyzing mathematical formulas, notch parameters and permanent magnet size are designed optimally to obtain large winding self-inductance, good sinusoidal degree of back-EMF, and low THD of cogging torque. The finite element verification in Ansoft proves selected parameters reasonable. Finally, an experimental prototype motor is specifically built according to determined parameters; and good performances, magnetic isolation, and fault-tolerant capacity can be guaranteed.
An Experimental Investigation of Ride Control Algorithms for High-Speed Catamarans Part 1: Reduction of Ship Motions
Authors: AlaviMerh Javad , Lavroff Jason , Davis Michael R. , Holloway Damien S. , Thomas Giles A.
Published: January 2021

Ride control systems are essential for comfort and operability of high-speed ships, but it remains an open question what is the optimum ride control method. To investigate the motions of a 112-m high-speed catamaran fitted with a ride control system, a 2.5-m model was tested in a towing tank. The model active control system comprised two transom stern tabs and a central T-Foil beneath the bow. Six ideal motion control feedback algorithms were used to activate the model scale ride control system and surfaces in a closed-loop control system: heave control, local motion control, and pitch control, each in a linear and nonlinear version. The responses were compared with the responses with inactive control surfaces and with no control surfaces fitted. The model was tested in head seas at different wave heights and frequencies and the heave and pitch response amplitude operators (RAOs), response phase operators, and acceleration response were measured. It was found that the passive ride control system reduced the peak heave and pitch motions only slightly. The heave and pitch motions were more strongly reduced by their respective control feedback. This was most evident with nonlinear pitch control, which reduced the maximum pitch RAO by around 50% and the vertical acceleration near the bow by about 40% in 60-mm waves (2.69 m at full scale). These reductions were influenced favorably by phase shifts in the model scale system, which effectively contributed both stiffness and damping in the control action.
Multi-fidelity Bayesian Optimization of SWATH Hull Forms
Authors: Bonfiglio Luca , Perdikaris Paris , Brizzolara Stefano
Published: January 2021

This study presents a multi-fidelity framework that enables the construction of surrogate models capable of capturing complex correlations between design variables and quantities of interest. Resistance in calm water is investigated for a SWATH hull in a multidimensional design space using a new method to derive high-quality response surfaces through machine learning techniques based on a low number of high-fidelity computations and a larger number of less-expensive low-fidelity computations. First, a verification and validation study is presented with the goal of comparing and ranking numerical methods against experiments performed on a conventional SWATH geometry. Then, the hull geometry of a new family of unconventional SWATH hull forms with twin counter-canted struts is parametrically defined and sequentially refined using multi-fidelity Bayesian optimization. Ship resistance in calm water is finally predicted using observations from two different fidelity levels. We demonstrate that the multi-fidelity optimization framework is successful in obtaining an optimized design using a small number of high-fidelity computations and a larger number of low-fidelity computations. Simulation and optimization costs are reduced by orders of magnitude, providing accurate certificates of fidelity for the performance of the proposed design.
Hydrodynamic Testing of a High Performance Skiff at Model and Full Scale
Authors: Day A. H. , Cameron P. , Dai S.
Published: January 2021

This study examines the hydrodynamic performance of a high performance skiff hull using three different physical testing techniques which may be used in early stage design for assessment of the upright resistance of sailing vessels. The hull chosen as a benchmark form is a high-speed hard-chine sailing dinghy, typical of modern trends in skiff design, and is broadly similar to some high performance yacht hulls. The 4.55 m hull was tested at full scale in a moderate size towing tank, at 1:2.5 scale in the same tank, and at full-scale by towing on open water. The work presented here builds on the study of Day & Cameron (2017), with the model tests repeated and re-analyzed in the present study and additional results presented.

The challenges of full-scale open-water testing are discussed and several potential improvements in practice are identified for future work. Results show that the open water testing broadly matches well with model-scale tank testing, with the mean discrepancy in the measured resistance between the two around 4% over the speed range tested after correction for the presence of the rudder. Agreement is initially less good for the full-scale hull in the tank for higher speeds, both for resistance and trim. ITTC guidelines suggest that blockage may be an issue for the full-scale boat in this size of tank; comparison of the results suggests that blockage, and/or finite depth effects for the full-scale hull in the tank present a substantial problem at the higher speeds. A correction approach for the wave resistance of the full scale results using a calculation based on a linear thin ship theory is effective in this case, and results show that the full scale and model scale tests agree satisfactorily for the majority of the speed range after this correction.

In addition to upright resistance in calm water, results are presented for the impact of small waves, the addition of the rudder, and variations in displacement and trim on resistance for a skiff hull. Finally, the results are compared with predictions from the well-known Delft series regression equations, Savitsky's methods, and a thin ship calculation. The thin ship approach gives good agreement for the case in which the hull is trimmed bow-down and the transom is not immersed, while the Savitsky pre-planing approach gives good agreement for the level trim case. The Delft series and Savitsky planing hull approaches do not give good agreement with physical measurements.
Sidecase (Boom) Dredging in Venequela and Suitable Projects in the U.S.A. and Canada
Authors: Van De Wiel E.
Published: January 2021

To alleviate the situation a T2 tanker was converted into a sidecast dredge for the purpose of dredging o channel in one of the tributaries of the Orinoco River. The converted tanker Sealane was completely successful in increasing the outlet of the Orinoco to the point where 83 percent greater tonnage per voyage could be carried in vessels up to 60,000 dwt. The Sealane was employed successfully in lengthening and deepening the entrance channel to Lake Maracaibo, Venezuela. This performance led to the construction of the sidecast dredge Zulia which has been in operation since February 1960. An account of the operation of these vessels and the potential of sidecast dredging in the United States, Canada, and in many problem areas throughout the world is given in the paper.
Tow-Cable Snap Loads
Authors: Schneider Lewis , Burton L. Grady , Mahan Thomas
Published: January 2021

When towing submerged bodies such as sonar vehicles or oceanographic instrument packages, the tow cable may be subjected to severe loadings because of large-amplitude ship motions. These motions first cause the cable to become slack and subsequently subject it to impact stresses at the instant of tension recovery. A typical body, cable, and oscillating tow-point assemblage is idealized as a single-degree-of-freedom system and the dynamical equations of motion are solved over a broad range of forcing amplitudes and periods and system compliance. The effects of such parameters as body density and cable compliance in attenuating the dynamic stresses are discussed.
Metallic Seals for Deep Submergence Underwater Vehicles
Authors: Bialkowski L. S. , Stachiw J. D.
Published: January 2021

Underwater vehicles require static and dynamic seals of axial or radial types to seal joints against high, external, hydrostatic pressures. Metallic knife-edge seals can do many of the sealing functions with superior performance in terms of pressure capability, low dynamic friction, controlled unit loading, low breakout force, self cleaning, and reusability. This paper discusses both the theoretical and practical design considerations of such seals and describes and evaluates experimental data generated to date by B. F. Goodrich.
Weight, Cost and Design Characteristics of Tankers and Dry-Cargo Ships
Authors: Johnson Roger P. , Rumble Henry P.
Published: January 2021

This paper presents a simple method of obtaining a first-order estimate of the displacement and cost of tankers and dry-cargo ships, as a function of payload, speed, and range. The two characteristics of primary interest to system analysts, displacement and cost, are summarized as a function of payload and speed by a single graph each for tanker ships and two types of dry-cargo ships. The components of weight and cost are developed from a series of design charts and simple equations. More detailed characteristics of the ship, including length, block coefficient, shaft horsepower, weight of steel, outfit, and machinery, also are presented as well as the primary elements of material and labor costs associated with the last three items. The Appendixes present supporting data and an example of use of the method.
Mechanization in the Maritime Administration Cargo-Ship Replacement Program
Authors: Tangerini Caesar , Dillon E. Scott , Fixman Carl M.
Published: January 2021

The first generation of mechanization features built into five groups of cargo ships now under construction in the Maritime Administration's replacement program are compared. Commentary is given on the differences in the independent approaches taken together with a brief discussion of additional features appearing in designs for Fiscal Year 1965 ships. Included also is an indication of the Administration's research and development program looking to a future second generation of mechanization for even greater operating-cost savings.
Managing Ship Maintenance
Authors: Apple Robert E. , Farrar Donald E.
Published: January 2021

The establishment of efficient ship maintenance on a component by component basis is complicated by the large number of installed components on a ship, and by the absence of data at the required level of detail. A method of statistical cost analysis that considers the ship as a single unit, and that uses generally available data, is shown to be useful for predicting repair requirements, and for establishing scheduled repair periodicity. The applicability of the procedure for commercial ships is discussed. Intensity of inspections is also discussed, with suggestions for reducing inspections to the reliability threshold that corresponds to maximum profitability.
Marinization of the General Electric LM1500 Gas Turbine
Authors: Stoeckly E. E.
Published: January 2021

After presenting some of the attractive features and characteristics of the aircraft gas turbine for selected marine-propulsion applications, this paper looks at those features of such engines that need improvement in order that they may become true marine power plants. Both cold and hot-corrosion problems are created by the marine atmosphere and the change from aircraft-type fuels to higher-sulfur-content marine fuels. Phases of a development program to produce the required features in the General Electric LM-1500 gas-turbine power plant are discussed.
Fatigue Testing of Large-Scale Models of Submarine Structural Details
Authors: Dunham Frank W.
Published: January 2021

The conversion of a 30-ft-dia test tank to a facility for subjecting large-scale models of submarine structural details to cyclic loading is described. By means of automatically controlled valves, models were subjected to a pressure variation simulating a submarine diving to its test depth and returning to the surface. The cyclic rate was slightly less than one per minute. The system was so designed that the test tank itself was not subjected to the pressure variations. Details of a series of models designed to simulate particular structural details of interest in recent submarine construction are described. Results of the tests to date are summarized, and several observations relative to the initiation and propagation of fatigue cracks in submarine structural details are presented.
The Implementation of SOLAS—1960
Authors: Price Robert I.
Published: January 2021

The 1960 Safety of Life at Sea Convention (SOLAS-1960) became effective on May 26, 1965. This paper, presented to the Metropolitan Section of SNAME in February 1965, discusses the effect the Convention has had and will have on the Coast Guard regulations which govern the construction and operation of U. S. flag vessels. Attention is also drawn to studies relative to the many recommendations of SOLAS-1 960 which are continuing through the Intergovernmental Maritime Consultative Organization (IMCO), and the extent of U. S. participation in such studies.
Sea Experience With Pratt and Whitney Aircraft FT12 Gas Turbine in LCM-8
Authors: Nolte G. H.
Published: January 2021

The design features of the FT12 gas turbine are described. The development back-ground of the gas turbine is reviewed along with service-experience background which, with appropriate marinizing treatments, prompted evaluating the gas turbine in a seaborne environment. The program conducted in an LCM-8 landing craft, its highlights and results are discussed.
Economic Analysis of Tank Coatings for Tankers in Clean Service
Authors: Purlee E. Lee , Leyland Walter A. , McPherson W. E.
Published: January 2021

An economic analysis has been made of a hypothetical 30,000-dwt tanker operated in continuous, clean service. Under the premise that the ship will continue to operate throughout her remaining book-life in predominantly clean service, two alternatives are considered. Alternative I: Conventional corrosion policy is continued. Annual shipyard repair, including steel renewals and maintenance are performed to the extent required. Alternative II: The required steel renewals are made at the end of the fifth year of service and all tanks are coated with a zinc silicate coating. Annual shipyard repairs and maintenance are subsequently performed to the extent required. In general, the methods consisted of (a) generating steel-renewal requirements by appropriate simulations for the 20 years' book-life of the vessel, and (b) conducting economic analyses of alternatives I and II for comparison. The results of this study indicate that coating the tanks in accordance with alternative II represents a net saving of $998,301 by the end of the vessel's book-life. The payout time on the coating investment was found to be 6.6 years with an average, annual return on the coating investment of 21.9 percent.
Analysis of NSMB Wake Surveys on Victory Ship Models
Authors: Cheng Henry M. , Hadler Jacques B.
Published: January 2021

In this paper the wake survey data of a family of models of the Victory ships measured and reported by the Netherlands Ship Model Basin are further analyzed. The scale effect upon the circumferential mean wake velocity and the harmonic contents of the circumferential velocity distributions are examined. It was found that for the relative amplitude of the various harmonics of the circumferential velocity distributions, the scale effect does not seem to be important. However, the effect of scale on the absolute amplitude of various harmonics could not be established. Extrapolated curves of the circumferential mean and the volumetric mean velocities for the ship are presented. Also reported are the effects of roughness, the comparative studies regarding the symmetry and repeatability of measurements, and the effect of rudder.
The Design of Hull Forms for Supertankers and Bulk Carriers
Authors: Laskey N. V. , Campbell G. T. R.
Published: January 2021

This paper deals with the results of model resistance, propulsion and seakeeping tests conducted on a form which has a block coefficient to 0.835 and a large bulb at the fore-foot, intended for use in tankers and bulk carriers. If details, also, the results of similar tests conducted on a special design of hull form for a Great Lakes vessel, the object of which is to determine whether or not satisfactory performance can be achieved at sea, as, today, vessels built for service on the Great Lakes are no longer landlocked owing to the completion of the St. Lawrence Seaway.
Theoretical Determination of Natural Modes of Deck Vibrations
Authors: Short Robert D.
Published: January 2021

Six methods for calculating the natural frequency and mode shapes of cross-stiffened plating were examined particularly for their application to plating with a large number of small closely spaced stiffeners in one direction supported by a few deep girders in the other. The best method was able to predict at least 1 6 frequencies (all that were measured) of a model with a maximum error of less than 15 percent when proper boundary conditions were used. The maximum error in nodal-line locations for the best method was 5.2 percent of the span
Design Considerations for Barges Transporting Hazardous Commodities
Authors: Steinman G. C. , Carman T. E.
Published: January 2021

The purpose of this paper is to present some design techniques and regulatory requirements for the construction of barges transporting hazardous cargoes. A paper on chemical barges would hardly be complete without a brief review of the early history of water transportation on the inland rivers. The barge and towboat concept in river transportation started as early as 1832, when keelboat barges were navigated by lashing them to steamboats. However, it was not until the seventies that fleets of barges became a common sight. The growing use of crude oil, which was found in locations convenient to river transportation, had a vital part in this development.
New Ferryboats for Staten Island-Manhattan Service
Authors: Karppi F. O.
Published: January 2021

Ferry service between Manhattan and Staten Island began centuries ago and now is one of the largest anywhere, in the number of passengers carried. When the City of New York's Department of Marine and Aviation decided to have three new ferryboats built, the firm of Kindlund and Drake was retained as design agent. This paper describes some of the requirements of the service and how the design and construction was affected by them. The boats were built by Levingston Shipbuilding Company, of Orange, Tex.
Construction of an Axial-Flow Pumpjet Propulsion Unit
Authors: Harvie James
Published: January 2021

This paper describes the construction of a pumpjet propulsion unit to reduce propeller noise on the Glover (AGDE-1). Although hydrodynamic design details are classified, structural design is described, and metallurgy, cutting, forming and welding of the bronze alloy used in the pumpjet are discussed, and the problems encountered are reviewed.
The Prediction of Notch and Crack Effects
Authors: Kuhn Paul
Published: January 2021

Historically, engineering structures have been designed for static strength, that is, for the one-time application of a large load. However, service loads, as a rule, are repeated loads, and a rather small load can break a structure if it is repeated very often; this phenomenon is known as the fatigue problem. Fatigue was for a while a serious problem in the design of automobiles. But automobile engines, for instance, are built by hundreds of thousands to one design. Service experience thus furnishes highly reliable information as to which parts are underdesigned, and the design methods can be improved by adding experience factors. In aircraft design, this avenue of approach can be used only to a very limited extent, largely because any failure in the air is likely to be catastrophic. Thus, strong efforts must be made to provide reliable methods of design by research rather than by developing factors derived from service experience. This paper briefly discusses two separate but related phases of aircraft fatigue research: The effect of notches under fatigue loading, and the effect of cracks under static loading. Quantitative understanding of notches under fatigue loading enables the designer to minimize the appearance of cracks. Quantitative understanding of cracks under static loading enables the designer to produce a structure which is safe when cracks do occur.
The Practical Application of Economics to Merchant Ship Design
Authors: Benford Harry
Published: January 2021

Naval architects and marine engineers should apply practical economics to decision-making in ship design. A commercial ship is not an engineering success unless it is also a potentially profitable investment. Profitability is related to technical characteristics, and these relationships should be understood by the designer. The paper gives a brief outline of several economic methods applicable to ship design, pointing out that the choice of criterion depends on such circumstances as whether revenues are predictable or not. It continues with suggested methods for estimating weights and building costs for ships. The problems of predicting annual transport capacity and operating costs are discussed in detail. There follow several comments on the practical application of all the foregoing ideas to decision-making in ship design. Sample studies are appended. Numerical values given in the paper are only intended to indicate trends. There is no intent to present an estimating handbook; the emphasis is entirely on principles and methods of application.
SEALAB II: A Departure From Normalcy
Authors: MacKinnon Malcolm
Published: January 2021

An important portion of the Navy's Deep Submergence Systems Program is Man-in-the-Sea. The major effort to date in this regard was the SEALAB II experiment conducted at 205 ft oft La Jolla, California in August-October 1 965. This paper describes the role of San Francisco Bay Naval Shipyard, Hunters Point, in the design, construction, and outfitting of the SEALAB II habitat. Included are the remarkable results attained in explosively forming the ellipsoidal dished heads required to complete the basic habitat cylinder. The difficulties in selecting equipment to operate in seven atmospheres of helium are also covered.
Ship Procurement—Isn’t There a Better Way?
Authors: Zeien Charles
Published: January 2021

A healthy shipbuilding industry requires restoration of "normal" economics to the business of furnishing cargo ships to the American Merchant Marine. Ground rules must strengthen the buyer-seller relationship, encourage maximum selling and proposal efforts, inspire shipyard inventiveness and research and development, allow individual yard standardization of plans, and give value to a builder's reputation for fair dealing, superior design, and good quality. Reduced dependence on direct government subsidy is essential to a healthy industry and should be sought through shipyard participation in financing, performance-type specifications, and an improved favorable tax structure.
The RCN’s Application of Method Study to Ship Design
Authors: Farrell K. P. , Judge R. , Engh I. B.
Published: January 2021

This paper presents a summary of the philosophy of Work Study and illustrates how the Royal Canadian Navy has applied these techniques to the design of naval vessels. Procedures and methods are outlined and several examples of the application to ship design are presented.
Advanced-Design Motor-Ship Machinery Plant—20,000 SHP
Authors: Butler E. A. , Kaufman R. , Pedersen T. V.
Published: January 2021

The merits of U.S. Flag motorships in conjunction with a new American design, high-powered diesel engine suitable for use on ocean-going merchant vessels is investigated. A 20,000-shp advanced-design motorship propulsion system as applied to a dry cargo ship design is developed. Particular attention is directed to the essential characteristics so necessary in the economical and reliable performance of the system. Optional equipment and machinery arrangements have been analyzed carefully for their compatibility to assure efficient operation and maximum convenience to crew members, both at sea and in port. The economics of the motorship are thoroughly investigated and reported in sufficient detail for critical comparison with the economics of other propulsion systems. It is demonstrated that the diesel engine of today is not merely another source of adequate power. The new medium-speed engine provides a residual-fuel diesel propulsion plant that shows distinct advantages in initial investment and operating costs. In addition to its overall economy, the diesel plant provides a propulsion system with a high degree of reliability and safety.
Model Studies for an Oceanographic Ship Derived From an Offshore Supply Vessel
Authors: Paulling J. R. , Silverman Maxwell
Published: January 2021

During the last few years, a number of operators of oceanographic research ships have considered the Gulf Coast offshore-oil-well supply vessel type for possible conversion to a research vessel. Such a ship of 155–165 ft length offers a number of attractive features; chiefly, reduced operating costs, and space for mounting portable or interchangeable equipment. The vessel's principal disadvantages reputedly are limited stability and a lack of seakindliness. An investigation of such vessels has recently been conducted by the Scripps Institution of Oceanography and the Department of Naval Architecture of the University of California. Model experiments were conducted to determine the resistance and powering characteristics, the motions in head seas, and rolling in beam seas. The transverse stability was computed for calm water and following seas. Four different hull forms were considered in these studiesa typical 155-ft-long single-chine supply boat;a round-bilge version of the same;a single-chine design developed to overcome several of the suspected deficiencies of Form 1 while still retaining the principal proportions; andan affine variation of Form 1 produced by multiplying transverse dimensions by 0.75 and increasing vertical dimensions by the same amount.

It is concluded that the most serious deficiency of the vessel type is the tendency to slam in a head sea. This may limit the maximum speed in head seas. The small saving in resistance exhibited by both the narrower and round-bilge versions is insufficient to justify choosing either of these on this basis alone. In addition, both of these forms roll more severely than the two wide, single-chine forms. Finally, the increased freeboard of the third form results in an ample margin of stability. It is felt, therefore, that Form 3 provides a suitable basis for developing a research ship design.
Application of Numerical Control to Shipyard Production
Authors: Brayton W. C.
Published: January 2021

The purpose of this paper is to present some of the problems encountered in the process of evolution from traditional shipyard production methods to a production system involving automation by means of numerical control of cutting and layout operations.
Stern Trawler Designs
Authors: Kristinsson G. E. , Doust D. J.
Published: January 2021

This paper describes generally the various design phases required in the development of stern trawlers, and covers in particular development of the first of a new series of stern trawlers suitable for operations off the Canadian Eastern Atlantic. It is based on an extensive study, initiated by the Department of Fisheries of Canada, and on a comprehensive series of resistance, propulsion, and seakeeping tests carried out on three different models by the National Research Council of Canada. The paper also deals with the techno-economic factors necessary to be considered by the owner before he makes the decision to build.
The Prediction of Long-Term Distributions of Wave-Induced Bending Moment from Model Tests
Authors: Compton Roger H.
Published: January 2021

A procedure is described for predicting the long-term distribution of wave-induced bending moments for a ship operating in a statistically defined ocean-wave environment, using results from model tests and realistic sea spectra. To illustrate the procedure a hypothetical tanker is subjected to a known wave environment, completely defined by a large population of sea spectra, and the long-term distribution of wave bending moment is predicted from a relatively small random sampling of sea spectra, using the proposed procedure. The predicted distribution is shown to compare favorably with the actual distribution of bending moment. Suggestions are made regarding the applicability of this procedure to the prediction of service wave bending moment distributions for actual ships in the design stage.
United States Army Shallow-Draft Boat Program
Authors: Sargent John F.
Published: January 2021

The increased emphasis on counterinsurgency-type operations forced the Army to consider means to improve logistics in swamps and inundated areas. The intent of this consideration was to complement aerial movement of men and supplies. Although this type of ground operation has a long history in military annals, prevailing circumstances have created an unprecedented demand for improved mobility in that environment. The unit of load arbitrarily established was a ton of supplies or a squad of troops, depending on the mission. The end item expected to carry that load had to be simple, cheap, and easily reproduced. Conventional boat designs tested in heavy watergrowths proved totally inadequate; consequently, a major part of the effort was directed to obtaining a propulsion system which was capable of swamp negotiation as well as good open-water performance. In the propulsion study, waterjets, sine disks, paddle wheels, rule propellers, and the airscrew were tested and evaluated. The use of a unique propulsion system was further complicated by boundary requirements of minimal navigational draft, of envelope size compatible with surface and aerial delivery, and of a weight allowing manhandling for limited distances overland. Selection was finally narrowed to the water-jet and the airscrew-propelled boat. Development of these two craft is currently in the final phase of tests and evaluations for field use.
Analysis of Assumed Mooring Arrangement for Maritime Class Ship
Authors: Horton John L. , Yagle Raymond A.
Published: January 2021

An assumed but routine mooring arrangement for a standard Great Lakes ship--in this case a Maritime Class vessel--is analyzed to ascertain what wind conditions would be sufficient to establish the sequence necessary to cause parting of one line, followed by parting of second and third lines and, finally, by full failure of the mooring arrangement. Wind-tunnel tests on a model of the ship are reviewed, and application of the minimum potential energy principle used in the analysis is illustrated.
A Note on Floodable Length and Subdivision of Oil Drilling Rigs
Authors: Kim Hun Chol
Published: January 2021

The floodable length and subdivision of a floating drilling rig is discussed. The use of three expanded concepts is advocated: the margin plane, the margin angle, and the free-board margin. A method of finding the floodable length curve under these multiple limiting conditions is presented with an example calculation of a hypothetical drilling rig.
Some Remarks on Model Tests With Floating Platforms in Waves
Authors: Wahab R. , van Sluijs M. F.
Published: January 2021

This paper reviews briefly the results and problems associated with model tests in waves on moored, floating drilling platforms. It considers the analysis of the observed phenomena which is based on experience gained from several tests on these structures carried out at the Netherlands Ship Model Basin. Most parameters which affect the motions of the platform are interrelated and not independent of one another. Consequently, the effect of any given parameter is hard to distinguish and thus limits the number of design trends and behavior predictions which could be formulated. Three important tends were noted, however, and can be summarized as follows:The important platform motions with respect to drilling ease are most favorable with a deep-draft platform;the behavior in waves is relatively independent of platform displacement;the optimal section shape of the horizontal underwater structures with respect to the platform motions depends upon the expected wave periods to be encountered.

The results presented are based upon a limited number of tests and must be applied only with caution. Model tests still are the only reliable method of predicting the behavior of a proposed drilling platform.
Shipboard Noise and Vibration from a Habitability Viewpoint
Authors: Hagen Adrian , Hammer Norman O.
Published: January 2021

This paper discusses the problems of noise and vibration due to propeller, propulsion machinery, and associated auxiliaries on commercial merchant ships, and their effects on shipboard habitability. Human sensitivity to noise and vibration is reviewed and some discussion concerning the relative positions of design agent, shipbuilder, and shipowner is presented. Results of shipboard noise and vibration surveys conducted by the Maritime Administration are presented together with proposed acceptable limits of noise and vibration.
Marine Steam Turbines
Authors: Brownlie K.
Published: January 2021

The reasons are examined for the present increase in the number of marine propulsion turbines being ordered. The design of a range of turbines is discussed, with particular reference to single-cylinder turbines, control gear, and reduction gearing. It is shown that parallel developments are taking place in the design of marine turbine-generator sets, which, due to increases in running speeds, have increased in efficiency and decreased in size and cost.
Development of ABS Rules for Construction of Offshore Drilling Rigs
Authors: Bannerman David B.
Published: January 2021

The need for criteria for the construction of offshore mobile drilling units was felt rather early in their development. The applicability of classification procedures to fill this need was recognized, by which the knowledge and experience within the industry could be codified into classification rules and administered for the benefit of the industry. The special mission of the units made it necessary to include some requirements not associated with classification of conventional vessels, such as stability and anticipated wave heights. The new rules are subject to revision as experience and new developments may indicate.
Effect of Tunnel Entrance Configuration on Thruster Performance
Authors: Ridley Donald E.
Published: January 2021

The paper is concerned with the effect of tunnel entrance configuration on thrust produced and hull resistance augmentation. A means of determining equivalent fairing radius is presented, and model test data from two sources are correlated with a limited number of full-scale tests. A method of determining whether resistance will be increased by the addition of a thruster tunnel is postulated. This method is checked against one set of model test data with two thruster tunnels, one forward and one aft, from which a drag coefficient for faired entrance sections is derived.
Fundamentals of Solid-State AC Variable-Speed Drives
Authors: Schoen Donald L.
Published: January 2021

Solid-state ac variable-frequency drives offer a new generation of high-performance, maintenance-free drive systems. The desire to use the rugged ac motor as a high-performance, variable-speed device goes back many years; however, its practical implementation had to wait three-quarters of a century for development of the silicon controlled rectifier. This paper opens with a brief review of the history of variable-speed dc and ac drive systems. Then the fundamentals of solid-state ac variable-speed drives are presented with emphasis on future technical and economic trends. The ac system is evaluated as an economic solution to providing basic functional drive requirements. The characteristics are compared with traditional high-performance dc systems. Finally, an attempt is made to describe the solid-state ac variable-speed drive of the future.
Delos: An Application of Oil Field Marine Technology to Space Programs
Authors: McClure Alan C.
Published: January 2021

Similarities are noted between the requirements of floating vessels for oil well drilling and for offshore tracking stations. A vessel is described which combines the steady on-station characteristics of the drilling platform with the mobility and other qualities required of the tracking station. The tracking platform is shown to be a superior vessel for this purpose in comparison with other types of vessels.
Submarine Main Ballast Tanks--Theory and Methods for Refined Structural Design
Authors: Pohler C. H. , Bernent A. A. , Wilson D. S. , Skinner W. A.
Published: January 2021

In a surfacing or emergency recovery maneuver, the safety of a submarine is dependent upon the structural integrity of its main ballast tanks. In addition to absorbing the cyclic effects of routine blowing over the life of the ship, in a casualty condition these tanks must sustain high and sudden air-blow pressures without rupturing. However, because of the weight criticality, the structure of these tanks must be efficiently designed. Included is a discussion of the nature and history underlying the evolution of submarine ballast tanks, with reference to the Submarine Safety Program stemming from the loss of USS Thresher. Theory and methods are developed for predicting the pressures applied to a ballast tank, and for the behavior of the tank structure under these pressures. Considered are variables of ballast tank and blow system configuration, initial transient loading, and quasl-static pressures. Equations are developed to relate these variables and to determine the level of stress in any part of the tank structure, with theoretical development appended. General applications of these equations to analysis of a ballast tank are presented, with simplified curves and tables appended, and applicability to strutted sandwich shells other than ballast tanks indicated. Finally a complementary test program, established to confirm these equations and including large-scale structural models and instrumented structural recovery trials, is briefly described.
Experience Concerning 1200-psi Naval Steam Generators
Authors: Kaune J. E. , Fritz W. A.
Published: January 2021

At a meeting held in the Naval Ship Engineering Center, Philadelphia Division, in January and February 1967, the following were found to be the principal reasons for the 1200-psi-boiler problems:Introduction of a new type of boiler without a sufficient training program;lack of a sufficient supply parts backup;lack of adequate manuals and documentation;lack of sufficient auxiliary equipment to assist in boiler operation and maintenance, and lack of optimum design features.

This paper describes the aforementioned problems and what has been and is being done to improve conditions. An extensive program is now underway to vastly improve overall boiler reliability and decrease maintenance requirements.
Contrarotating Propeller Propulsion— A State-of-the-Art Report
Authors: Hadler J. B.
Published: January 2021

This report presents a synthesis of existing knowledge, albeit limited, on CRP as applicable to merchant ship propulsion. It presents propulsive performance data for two types of ships, tankers and containerships, based on model tests, and discusses briefly the stopping, cavitation, and propeller-induced vibration problems of CRP. From the analysis it appears that the greatest potential for employment of such a propulsive device, offering significant reductions in installed shp, is on high-powered, fine-formed ships for which the only current alternative is a twin-screw installation.
CASDOS—A System for the Computer-Aided Structural Detailing of Ships: Present Status
Authors: Romberg B. W. , Roth C. E.
Published: January 2021

The Naval Ship Engineering Center is sponsoring the development of a computer system whose output will be information necessary to fabricate and assemble the structural components of naval surface ships. This output will be in the form of graphics, printed output and numerical control tapes. The system, given the acronym CASDOS for Computer Aided Structural Detailing of Ships, is now at a point where implementation trials can begin. This discussion describes the present state of development, illustrating the principle inputs, outputs, and program structure. The description is centered around use of the system rather than program design and file structure, and should be of interest to individuals involved in ship production.