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The USCG's (US Coast Guard) current fleet of buoy tenders consists of about 40 cutters of the WLM and WLB classes. The majority of these vessels were built between 1942 and 1944 and have undergone numerous modifications overhauls and renovations in their 50-year service lives. In 1979 the USCG facing increasing costs associated with operating this aging fleet of buoy tenders and increasing pressure to control budget growth by operating fewer ships with fewer men embarked on an ambitious replacement program. This procurement approach resulting from the USCG initiative is discussed and the WLB and WLM designs which were selected for procurements are described. Also discussed are a number of the significant design trade-offs and design drivers and the rational for selection of both the overall ship configuration and specific shipboard systems for the two designs is provided.

Sea state forecasts for the offshore industry are based on spectral sea state parameters. Up till now they gave no information about the risk to encounter extremes. Therefore additional wave parameters have to be identified that point out an increased risk for extreme waves and-or dangerous seas. For several years X-Band radar has been used to image ocean surface waves. Based on standard marine X-Band radar the Wave Monitoring System WaMoS 2 allows the sea state to be monitored by analysing the radar signatures of waves. The long ocean waves modulate the radar backscatter of the wind roughened sea surface (sea clutter). From resulting stripe-like patterns in the radar images WaMoS 2 calculates statistical sea state parameters as significant wave height (Hs) peak wavelength (?p) peak period (Tp) and others. A new analysis software called 'SinSee' was developed to allow the determination of single wave events from X-Band radar images. This evaluated the safety of ships in severe sea states. Subsequently WaMoS II sea surface elevation sequences were analysed to understand the spatial behaviour of single ocean surface waves.

Some research into sea-keeping control in fast ferries is reported. This research is devoted to general heading and sea state conditions. Although scaled ships are the basis for experimental studies it is not possible to keep using them in towing tanks since high speeds require more space for experiments. Consequently open-air experiments are to be undertaken. A new fast autonomous scaled ship has been developed. She is self-propelled and is self-governed by an embedded pc on-board. The ship carries sensors for heading speed and sea-keeping control. Several scaled moving appendages have been added: two transom flaps two lateral fins and a T-foil. The ship uses two scaled waterjets which also control the heading: the ship has no rudder. A distributed monitoring and control system has been designed and implemented for on-board operation. All equipment has to be very light since the real fast ferry that is reproduced at 1:40 scale is made of aluminium.

The maintenance of a ship is essential for safe navigation and thus regular surveys are prescribed according to the rule of classification societies. A hull inspection is generally carried out by professional divers but the efficiency is low in terms of time and cost. In this research a ROV (remotely operated vehicle) called SNU-ROV (Seoul National University-ROV) is developed to replace the conventional inspection method. This system uses the ROV to inspect ships and harbours. (Harbour inspection is emerging as a safety measure against any possible terrorist activity.) In order to increase the efficiency of inspection the ROV must be able to measure the exact position of any damage.

CFCs (chlorofluorocarbons) are a class of synthetic chemicals some of which are used in shipboard air-conditioning and refrigeration systems as well as for some cleaning applications. Halons are also a class of synthetic chemicals some of which are used in shipboard fire-suppression systems. These substances have been found to damage the ozone layer and because of international treaties and US legislation domestic production of both these synthetic chemicals has ceased. However these ODSs (ozone-depleting substances) are used in applications that are considered to be mission-critical. Therefore the Navy has built up a strategic reserve to support the Fleet until all ships are retired or converted to use suitable alternatives. It is estimated that the last requirement for ODSs from the reserve will be in the middle of the 21st century. The history of the Navy's effort to define establish and monitor a reserve designed to support Fleet operations until then is documented.

The aircraft launch systems currently in use on board aircraft carriers rely on steam technology. This presents significant drawbacks. With the trend towards AES (all electric ships) an interesting solution to accelerate an aircraft to the take-off speed from an aircraft carrier would be to use a PM linear machine driven by a PMW Inverter (EMAL System (electromagnetic aircraft launch system)). In order to study and design such a linear electrical launch motor the classical way is to use a Finite Element or Finite Difference 2D or 3D calculation code. This method is therefore very difficult to use in a systematic design process to optimise the main parameters of the machine because the solution is very cumbersome in terms of complexity and calculation time and very sensitive to the mesh quality. In order to be inserted within the systematic design process a new analytical calculation method for PM linear launch machine is presented.

A completely new approach to standard design for ships is presented. The use of a powerful computer program has produced a method which it is claimed reduces construction time. Standard tug designs are an essential part of the towing industry but producing a range of designs can involve high initial costs. Many smaller yards are unable to take advantage. Steel-Kit has developed a new approach which combines a 75 per cent reduction in delivery times without large investments. The computer-based construction allows the advanced construction techniques used by large shipyards to be used by smaller yards. The secret of the Steel-Kit system is the way the design is analysed and optimised for the construction process. Estimating for hull construction is more precise and the steel cutting process is more efficient.

A condition survey carried out to study the extent and distribution of corrosion in the water ballast tanks (WBT) of 22 in-service ships is reported with particular reference to the effects of ship age (4-20year) corrosion protection system used (hard coating with tar-epoxy paint with and without back-up sacrificial anode) service conditions (extent of immersion and temperature) and maintenance schedule on effective life. A program of laboratory studies using coated test pieces in simulated WBT conditions was also carried out to clarify factors (including paint composition thickness and integrity) affecting the deterioration of coating with age. The findings are used to propose an effective corrosion protection system for the expected life of WBTs and other hull structures. An appendix explains the definitions for ratings of hull condition.

A two-phased integrated methodology to predict the route/mission-dependent rational structural dynamic loads for high-speed multihulls was developed. The specific program of work described in this paper represents the first phase of the two-phased effort to develop a ship motion and dynamic load calculation methodology that would be suitable for use by Designers Classification Societies and the U.S. Navy. The method developed would be suitable for advanced hullforms. In Phase I an overall working model of a frequency-domain ship motion and loads model was developed incorporating a route-based mission profile module to provide a description of the ships' overall lifetime loads. This paper summarizes the contributions to the state-of-the-art on rational structural design methodology accomplished during Phase I of the project.

The ship hulls of modern large oil carriers and container carriers have become more flexible with scantling optimisation and an increase in ship length. However as the demand for power has increased with the ship size shaft diameters have become larger and stiffer. Consequently the alignment of the propulsion shafting system has become more sensitive to hull girder deflections resulting in difficulties in analysing the alignment and carrying out the alignment procedure. Accordingly the frequency of shafting alignment-related bearing damages has increased significantly in recent years. Hull girder deflections are the most significant disturbance that affects the bearing offset after vessel construction. Inability to account for hull deflections may result in poor alignment design with serious consequences on the bearing life.

SASSACUS is a 45-metre FBM TRICAT fast ferry built in Connecticut. SASSACUS set a precedent by being the first US vessel built entirely to the IMO's new International Code of Safety for HSC (high-speed craft). The background and philosophy of the HSC Code are discussed as well as how the classification society DNV and the regulatory agency US Coast Guard have affected the outcome. Specific difficulties experienced in the construction and trials of SASSACUS are mentioned. The impact of this project on future ships constructed to this code is summarised.

A large number of design parameters are known to affect damage stability of ro-ro passenger ships. Amongst these and of great importance are the number and location of transverse bulkheads the location of longitudinal bulkheads below the main deck the length of lower hold the location of main deck and double bottom the existence of central or side casings above main deck etc. The aim here is to estimate the influence of these parameters on the attained subdivision index A of the vessel. To accomplish this a representative group of ro-ro and ro-pax vessels is selected and starting from the original designs the parameters mentioned above are systematically varied and damage stability calculations are carried out for the new models. The results obtained on the attained subdivision index A are presented and critically reviewed and suggestions for improved design are derived.

A program is presented which examines promising technologies for application to construction of sealift ships. One of the goals of this program is to enhance the competitiveness of US shipbuilding by investigating a new method of hull construction that would be easier and cheaper to build and pre-outfit. The concept consists of a long-spanned unidirectionally stiffened structural system where the main structural elements are arranged longitudinally. This double technology is referred to as ADH (advanced double hull). In the second year of the study a new design criterion was applied. This criterion was based upon the results of structural testing and analysis to determine the ultimate strength of cellular structure. A full ship finite element model was developed to help validate the structural criteria.

Increasing size and speed and rising fuel prices require that a container ship's hydrodynamics need to be at the highest level of sophistication. The integration of geometric modelling and flow simulation offers new opportunities to improve design processes and the quality of the resulting ships. The paper presents considerations of economic aspects design methods and results from a comprehensive optimization project for a medium-size container carrier. A novel hull design element was established that improves transport efficiency without imparing operational qualities. The element reduces resistance and increases payload and is based on an innovative layout of the sectional area curve (InSAC). the novel volume distribution influences a ship's free wave pattern advantageously reducing the energy loss in the free waves generated by the steadily advancing vessel. Benefits are shared by shipyards operators and owners alike resulting from the options of installing smaller engines unloading the propulsion plant utilizing added displacement or further pushing design speed.

In this paper, an advanced method for the development of an empirical model to predict time-dependent corrosion wastage is proposed. It is well recognised that the statistical scatter of corrosion wastage at any exposure time is generally very wide, and the reliability of a corrosion model thus relies on how accurately such scatter is measured. In the proposed method, the statistical scatter of corrosion wastage at any exposure time is analysed in a refined manner and formulated using the Weibull function. Both the shape and scale parameters of the Weibull function are determined as a function of time through the curve fitting of a corrosion measurement database. An application of the proposed method’s use in the development of an empirical model for the seawater ballast tank structures of aged ships is presented. Its ability to generate an empirical corrosion model is confirmed, thus making it possible to predict time-dependent corrosion wastage more accurately.

AES 97 - First International Symposium and Exhibition on 'Civil or Military All Electric Ship' Paris France 13-14 March 1997. The all-electric ship incorporates a single power network supplied by a primary energy source made up of generators distributed within the ship. This primary source produces electricity and is distributed to all of the ship's electric applications. The following topics are discussed in the symposium sessions: electric propulsion motors, naval architecture, electrical equipment, technology and systems and anaerobic propulsion. The symposium aimed to assess current world-wide studies, projects and developments relating to electric ships. Separate supplement contains presentation slides for 4 papers: Permanent magnet propulsion motor technology and ship design, Propeller with combined disc motor for hydrojet propulsion, Savings in installed power, fuel consumption and emissions with electric propulsion and a New type of permanent field machines for diesel electric propulsion systems.

Recent years have seen a growing global demand for small ships of ever-increasing speed and capacity. This demand for high-speed vessels especially car-passenger ferries and small surface combatants has led to a search for unconventional hull forms with superior high-speed performance and capacity. The catamaran and SWATH are examples of vessels that are commonly used in these roles. Another unconventional hull form which might be considered for use in these applications is the trimaran. The trimaran offers the potential for relatively low powering requirements at high speeds large deck areas and more conventional machinery arrangements than twin-hull vessels. An investigation of the effects of side-hull position symmetry displacement and angle of attack on the resistance characteristics of powered trimarans is presented. The objective of this research is to produce a useful design tool to quantify the resistance characteristics of these trimaran configurations. This tool will allow naval architects to balance hydrodynamic performance with other design considerations in the conceptual designs of powered trimaran vessels.

Tunnel thrusters comprise a propeller mounted inside a tunnel which is attached to vessels such as ferries container ships passenger vessels etc. In the past theoretical analysis of hydrodynamic performance of tunnel thrusters has been extremely difficult. In designing propeller blades of tunnel thrusters for hydrodynamics and strength it is necessary to accurately estimate hydrodynamic forces on the blades as external forces. In order to overcome these problems a new analysis method has been developed using CFD (computational fluid dynamics) based on RANS (Reynolds averaged Navier-Stokes') equations. An outline of this analysis method is described and computed results are verified by comparing them with measured data. Force-acting points on a blade during one revolution are also discussed. This method is shown to be a very useful and reasonable design tool for the propeller blades. Results are presented and discussed and conclusions are drawn.

Symp held in Plymouth 26 - 28 October 1982 Papers are The stability of non linear multivariable systems - review of frequency domain methods Control systems design for uncertain dynamical systems A time domain interaction for multivariable plant Robust computer aided control systems design for non linear plants Computer aided design modelling and simulation of control schemes On the recursive identification of multivariable state space models Steering stabilisation and computer control Automatic pilotage of large ships in confined waters a multivariable approach A multivariable controller for depth control of a submersible vehicle The identification of ship dynamics in roll and yaw using a free running autopilot controlled model Adaptive multivariable control of a naval propulsion plant Implementation a multivariable self tunable P1-Type controller in a distributed microcomputer system Error predicting in parameter estimation for the load frequency control of multi area power systems Multivariable identification and control of electric plants Multivariable systems in nuclear plants Multivariable systems in nuclear power plant Development of a multivariable controller for an industrial compressor An analysis of a non linear multivariable once through boiler control system

The rising cost of energy has led to investigations into how electric power generation on board ships can be provided by a simple system burning cheap heavy fuel. This means amongst other things a power supply from heavy fuel generating sets running on unblended bunker fuels . The cost of power generation from bunker fuel auxiliary diesels is discussed and compared with the traditional ship having 2 types of fuel on board i.e. bunker and diesel fuel. Details are given of the design and investment operating and maintenance costs. Fuel treatment common supply systems for main and auxiliary engines and problems of black-out of electric power supply are discussed. Particular attention should be paid by operators to lub oil treatment for auxiliary engines running on bunker fuel. A report is given on the operating experience to date of MaK engines using low-grade fuels.