The influence of rudder size and rudder angular on maneuvering performance of a typical large tanker (the 250.000 DWT type) was examined by digital computer motion simulations of turning and Z-maneuvers under open, deep water conditions, The mathematical model is based on hydrodynamic data obtained from captive model tests carried o“t in the rotating-arm facility. Ship response in turning and particularly in Z-maneuvers is improved by increasing the rudder angular velocity. The improvement is more significant at lower rudder angular rates and higher ship speeds. At rates greater than the present standard of 2.3 degrees per second, the improvement due to increased rate is less noticeable than at rates lower than standard. At ship speeds less than 16 knots the improvement is proportionately reduced until at modest maneuvering speeds such as 4 to 8 knots it becomes relatively insignificant. Increasing the rudder size from its design value has relatively little effect on turning performance but somewhat improves Z- maneuver response. In particular, the lateral overshoot of the ship trajectory is reduced with an increase in rudder size. The effect of the rudder rate shown in this study is for a typical 250,000 DWT tanker at the fully loaded condition and is largely affected by ship size and speed.
This Report provides information and guidance to designers and shipbuilders on the proper design precautions necessary in a machinery plant to prevent damage to the boiler and superheater during light-off. In addition, guidelines for operation and maintenance are provided, in order that the ship operator may continue to expect safe plant start-up throughout the life of his ship.
The Society of Naval Architects and Marine Engineers (SNAME), by the size and diversity of its membership, is in the unique position to coordinate research planning for the maritime industry. This report summarizes the activities of the Advance Planning Committee since its inception and recommends new directions for the Society.
Although the importance of proper alignment of the propulsion shafting has been a well-publicized recent year, discussions among M-16 Panel members involved in all phases of shipbuilding and repair indicated that there still appeared to be some lack of knowledge surrounding the subject within the industry. In general, it was felt by the panel members that most designers of new ships were aware of the various alignment criteria for shafting systems and were designing new ships with shafting systems that met the criteria. However, it was noted that often in repair work, particularly in older ships the shafting systems were poorly designed and usually no data exists on the desired alignment. In addition, frequently the personnel performing the work are not aware of the importance of proper alignment.
For example, if no other information is available, a repair facility may realign a shaft system with all bearing on a straight line, whereas the original alignment called for some bearing to be offset to improve the load distribution and contact in the bearings or perhaps provide proper alignment with a reduction gear. In such a case, the straight-line alignment could result in wiped bearings, excessive gear wear, or perhaps a vibration problem.
The panel decided to conduct an alignment survey of American Shipyards. The questionnaire covers (1) the criteria used in evaluating shipboard alignment, (2)acceptable tolerances on alignment, and (3)methods used for measuring alignment.
The intent of this report is to make the results available to the industry in an effort that can be reasonably expected of a shipyard by a shipowner when an alignment check in necessary in a ship.
This report examines shipboard lifesaving systems, analyses present practices as far as performance is concerned, and makes recommendations for future lifesaving systems. Primary recommendations are that personal exposure protection should be increased and that better retraining in the use of lifesaving equipment is required.
With the energy element of vessel operating costs outstripping both the escalation rates and absolute values of nearly all other primary ship-connected expenses, little more needs to be said to underscore the importance of a comprehensive review of the maritime energy research problem. The urgency of energy conservation research has been diminished somewhat by current fluctuations in crude oil prices and availability, but long term trends continue to support the need, SNAME's T&R program has addressed a number of ways in which energy expenditure might be reduced. These include basic hull and propeller design, machinery component and cycle design, hull coatings, ship operations, the use of primary fuels, and alternative fuels and non-current sources of energy.
This report presents the Society's current assessment of ongoing and potentially useful programs. Although the emphasis is placed on programs expected to yield results applicable within a five-year period at most, a number of longer-term projects also are noted. The short term projects are recommended for review by appropriate panels of the T&R organization's Technical Committees and Panels in formulating their technical and research programs over the next several years. The longer-term projects are recommended both to the Technical Committees and Panels for the out years, and to the Advance Planning Committee for monitoring, as to continued need and ultimate action by the Technical Committees.
Over the last 25 years, the dramatic change from conventional to containerized cargo transport has resulted in major changes to terminal facilities, transport vehicles, container handling equipment, and required personnel skills. New sophisticated container ports represent major investments and require highly paid personnel. In spite of this, the terminal is the most efficient, and safe mode of transfer between water and land. Innovations in transport vehicles also provide increasingly safer and more efficient movement of cargo. However, the new cargo handling methods are not without problems. Personnel injury, damage, and loss of cargo and equipment are experienced during the transportation process as a result of human error, accidents, poor judgment, inadequate equipment, insufficient packaging, lack of training, and safety procedures, and pilferage. These problems all have a significant effect on the economics of the total transport system. The costs must be borne by the shipper and ultimately, the consumer.
A new theory and computer program to predict the resistance of a sailing yacht with keel and winglets ace presented. While established ship-motion and added-resistance theories have been shown to give reasonable results for conventional ships, they do not satisfactorily predict the rough water behavior of a yacht sailing to windward. This is partially due to an inability to accurately account for the effects of the keel and other lifting appendages, including winglets as found on most modern International Twelve-Meter Class Yachts. Theories for evaluating both steady and unsteady lift, and the associated thrust and drag, due to body motions and waves must be included in order to obtain useful results. These theories have been incorporated into existing motion and added resistance prediction programs and can be used to determine the behavior in waves of a yacht sailing to windward at a specified angle of heel and yaw. Computer results for yachts with and without winglets are presented and compared with experimental results, which include the recent model experiments conducted by Gerritsma in Delft.
Single-skin glass-reinforced plastic (GRP) was the first craft in the early 1940s. Sandwich construction - a pair separated by and bonded to a thicker, lightweight core - is used in small marine Of thin, strong skins relatively new in the marine industry. Sandwich construction in general was introduced at about the same time as GRP in other industrial areas, namely aircraft, and structural engineering. Today, fiber-reinforced plastic (FRP) single-skin construction is employed in almost 80 percent of marine small craft design. Sandwich construction with balsa or foam cores is a much smaller percentage but is used almost exclusively in the construction of larger power vessels both private and commercial. The largest cored sandwich vessels built to date in North America are LOA 130 feet in length and are built of FRP skins and foam-cored construction.
The Society of Naval Architects and Marine Engineers has requested Tracer Hydronautics to perform a Trials - Model Test Correlation study for a 769 Foot Containership, Marad designation C8-S-85d. This report presents the findings of that study, performed under SNAME Purchase Order Number 0823. Tracer Hydronautics gratefully acknowledges the cooperation of Bethlehem Steel Corporation in providing trial data and trial calculation worksheets for this analysis.