Considerations Affecting Freeboard


The minimum freeboard that can be assigned to a vessel is that derived from the regulations depending upon the dimensions and characteristics of the vessel. The actual maximum operating draft permitted may coincide with minimum freeboard or it may be set by other federal regulations developed as a result of U. S. law or by international agreements such as the subdivision regulations in the 1973 Oil Pollution Convention, the IMCO Chemical Code or Gas Code.

Within the load line regulations the minimum freeboard may be affected by ship geometry, hull structure or stability. In no case can a freeboard less than the minimum geometric freeboard be assigned even though the scantlings of the vessel are heavier than required for the draft and the stability in excess of that required by an Administration for the intended freeboard.

Freeboard Tables

The tables issued for freeboard are based upon a comparison with a rule vessel having a standard sheer, length-to-depth ratio, block coefficient and reserve buoyancy. Adjustments are made for variations from the standard ship and there are different tables for different types of vessels.

Strength of Hull

The regulations assume that the strength of the vessel is satisfactory for the draft corresponding to the freeboard assigned. Considerations Affecting Freeboard - 2Ships which comply with the highest standards of a classification society recognized by the Administration are regarded as having sufficient strength for the minimum freeboards allowed under the regulations. Ships which do not comply with the highest standards of a classification society are to be assigned such increased freeboards as are determined by the assigning authority. The corresponding draft in such cases is often referred to as a scantling draft

Protection of Crew

It should be noted that while the freeboard assigned is based primarily upon reserve buoyancy, the question of a suitable height of platform for the safe working of the vessel by the crew is automatically dealt with at the same time. Protection for the crew, in the strength of houses, gangways, guard rails, life lines, and the height of working platform itself, is a very important concern of the load line regulations and specific regulations are provided for each.



The original International Convention on Load Lines, 1930, presumed that specific stability approval was not a concern of the regulations. At that time it was assumed that those responsible had seen to it that the "nature and stowage of the cargo, ballast, and so on, are such as to secure sufficient stability for the ship."

The present Convention (ICLL, 1966) has reversed the position of the earlier Convention by including a specific regulation worded such that stability information must be provided the master of every new vessel, "in an approved form to give him guidance as the stability of the vessel under varying conditions of service." This requirement has been interpreted quite firmly by the U. S. Coast Guard to include an inclining test for almost all U. S. commercial ships, a full stability evaluation based on the inclining, and an official stability letter issued by them as a condition necessary to issuance of the official load line certificate. Many other administrations follow a similar procedure.

Passenger Ship Subdivision

A vessel engaging in international voyages and carrying more than twelve passengers is governed by a separate regulation. Considerations Affecting Freeboard - 3Internationally, a load line is assigned and marked depending upon a subdivision and damage stability analysis of the ship under the applicable regulations of the SOLAS, 1974. Under U. S. regulations for certain ships, depending upon size or other limitations, a subdivision and damage stability examination is required if six or more passengers are carried. In no case may this subdivision load line be placed higher on a ship's side than the load line permitted under the load line regulations.

Geometry of Vessel

The minimum freeboard is designed to provide a standard of reserve buoyancy (the volume of the watertight hull above the load waterline) that has been found by experience to be satisfactory in service. This minimum freeboard is based upon the geometry of the vessel. A comparison is made of the block coefficient, the length-to-depth ratio, bow height, and the sheer of the vessel with those of a standard vessel of the same length.

Corrections are made to the basic freeboard, predicated on the length of the vessel, depending upon how these particulars vary from those of the standard vessel. Deductions are made from the freeboard depending upon the length of superstructures and the character of the closures in their end bulkheads. The resulting freeboard gives a height of working platform and a proportion of reserve buoyancy equivalent to that on vessels which have proven satisfactory in service.

Both camber and sheer play a part in clearing water rapidly from the decks, but only sheer corrections to freeboard are made depending upon the differences in sheer from the standard. Since there is no standard for camber in the 1966 Convention, no adjustment need be made.

Superstructures can contribute to reserve buoyancy and offer protection to openings in the hull at the level of the freeboard deck under certain conditions. Deductions are made from the freeboard for these special superstructures depending upon the efficiency of the protection provided for access openings in the end bulkheads.

Detached superstructures are also a consideration because there are differences in the deductions for superstructures depending upon their length and location. While the regulations do not require that a forecastle be fitted, a minimum height of the bow above the summer load water line is specified. In lieu of a forecastle the required bow height can be obtained by increasing the sheer curve of the main deck.

Openings in the Hull and SuperstructureConsiderations Affecting Freeboard - 4

A most important consideration in the assignment of freeboard is the protection of openings in the hull and superstructures, such as hatches, ventilators, air pipes, scuppers, overboard dis¬charges, and the access openings in the end bulkheads of superstructures. Standards are laid down in the regulations for these, and the assigning authority must be satisfied with their efficiency before a minimum freeboard is assigned. The safety of the vessel depends far more upon their satisfactory maintenance than in any small differences in the freeboard assigned.

35 Views 0 Comments Read more

Another piece of classics here. The old yet useful volume on naval architecture written by the former professor of naval architecture and marine engineering of the MIT, standing for the Massachusetts Institute of technology. The intention of the publication was to provide in a connected and maximum possible consistent manner the theoretical essentials of the naval architecture.

The author tried to stick to this approach, making the presentation of the material more direct and simple, particularly for such topics as the ship stability, ship propulsion, local and overall strength, displacement and many others. First of all, the author gave a clear statement of the computing rules and also included an informative instruction on the mechanical and graphical integration. Then, the text moves to the detailed explanation of the ship displacement and everything related to the stability of the ship, since this is considered one of the most important areas.

All fundamental information and commonly used computational methods have been covered in detail. Going through the contents of the book we can definitely say that the author managed to compile all the basics of the naval architecture in a single volume which would be equally useful to the students of naval architecture and to the practicing shipbuilders and ship designers.

72 Viewing 0 Comments Read more

People use different marine structure including both floating and fixed ones, to perform their duties and carry out associated activities on the water. Of course, all of those structures shall be designed and constructed in many shapes and sized varying from the small-sized canoe and up to the huge supertankers and drilling rigs.

Naval architecture is one of the most important engineering disciplines dealing with the ship design technology. In order to build the floating structures mentioned above, ship builders require properly developed design drawings, plans and calculations, and all of these are normally prepared by the naval architecture professionals, i.e. naval architects. That is why proper knowledge of all principles of naval architecture must be possessed as necessary.

Naval architects work on determining of the shape and size of the vessels they design; then, they estimate the stability and propulsive power of the vessel, calculate the strength of the vessel’s structure. After that, the designer proceeds to the materials to be applied, arrangement of the vessel, machinery and equipment, and other matters, all based on the sound knowledge of the naval architecture without which any design would not be possible.

161 View 0 Comments Read more

This set consists of two books on ship’s stability, in fact two editions of the world famous title. The latest fourth edition has been fully revised and updated and that is the reason why we decided to include both books. We are aware of the serious changes in the marine transportation of cargoes and design of ships intended to serve purpose. However, it shall be noted that the rules and regulations that pertain to the transportation of the movable bulk cargo remained more or less constant being working.

There are four main parts in this book. The opening chapter of the volume is dealing with the prerequisites for the calculations of the ship’s stability and trim as well as the hull strength. The first part is dealing with the transverse stability of the ship including inclining test, free surface effect and stability at large angles.

The second part addresses the longitudinal stability of the vessel while the third part covers the longitudinal hull strength. The final part will provide information on the modern application including usage of the shipboard computers calculating stability, practical aspects of ship stability etc. Some additional information is provided within several appendices to the main part.

346 Views 0 Comments Read more

The present volume is making one of the parts of the famous Reed’s series of book. The intention of the author is to provide a comprehensive professional coverage of the theoretical knowledge related to the naval architecture the one particularly required by the marine engineers.

The arrangement of the material contained in the book is very helpful to the reader – the author starts with the very elementary information and then step by step goes deeper. Throughout the content of the publication, the main emphasis is placed onto the essential theoretical principles.

The text is supplemented by the numerous illustrations of a very informative character, and such approach makes understanding much easier. We may assure you that all engineers who work systematically with this book will eventually find the time spent on the learning amply fully and adequately repaid since they will have a good understanding of all principles of the naval architecture and be able to apply their knowledge when handling their day to day operations.

The book definitely deserves attention of all marine engineers since the author concentrates on the maters specifically chosen to suit their needs with no excessive information.

426 Views 0 Comments Read more

Here is one of the most useful volumes of those making the whole Loss Prevention series. The document is dealing with such critically important aspect of ship handling as the stability, applied to the small ships. The book opens with some introduction and the basic information concerning lack of proper understanding of the ship stability criteria together with the possible consequences.

The authors have addressed the key principles that should be observed as necessary - failure to do so would eventually result in the loss of stability. Such principles include but are not limited to the container heights and weights, overloading of the vessel, FSE, standing for the free surface effect, derricks and cranes, pre-load requirements, stability calculations performed by means of the shipboard computers, freeboard reduction etc.

The content of this volume is mainly aimed at the crew members of the dry cargo ships. The main purpose was to provide them with the opportunity to get better understanding of the basics of the ship stability and its determination. Unfortunately, not all crew members of those assigned responsibility for loading operations possess necessary knowledge of the subject. The appendices supplementing the main part of the volume give some additional information.

513 Views 0 Comments Read more

The present naval architecture and ship stability textbook was released to provide naval architects and students with a thorough understanding of the fundamentals of ship stability. The past decades showed the evolvement in the assessment of the ship stability. The volume will enable readers to get themselves duly familiarized with the modern methodologies.

The author gives excellent explanation if the probabilistic damage methodology, detailing the relevant requirements applicable when assessing the newly introduced ship classes and sizes. The volume contains very useful and up-to-date information and this makes it useful to the students of naval architecture and marine engineering. The content is perfectly illustrated and includes numerous chapter studies.

The material of the book has been arranged in fifteen chapters. The first one introduces readers to naval architecture while the next thirteen chapters make the main body of the volume covering all necessary aspects of the modern ship stability. Finally, the closing chapter provides several examples for better understanding of the theoretical part. An absolute must-have for all naval architects and anyone with the professional interest in ship stability.

587 Views 0 Comments Read more

The author of this publication has successfully adopted a practical approach and has presented all recent researches and also different practical applications in the real-life design and operation of the submarines. The list of topics covered within this volume is including the hydrostatics and maneuvering of the submarines, and their resistance and propulsion problems.

The author has conducted a brief review of the fundamental technical concepts in ship hydrodynamics and then proceeded to the demonstration of how exactly subject concepts could be applied to the submarines, covering the use of the physical model experiments. He has also clearly explained all issues commonly associated with the maneuvering of the submarine in the vertical/horizontal planes allowing readers to discover the suggested stability criteria, together with the effectiveness of the rudder and also hydroplane.

The publication also is including a separate section covering the design of the hull appendages including all technical info relating to the sail design and arrangement of the bow planes plus alternative configurations of the stern part of the submarine. Among the other topics that have been addressed in this volume we would mention the hydro-acoustic performance, different resistance components and hull shape effect. The content reflects a great experience of the author in this field of submarine design.

4558 Views 0 Comments Read more
1 2 3 ... 7 8 »
Enter the site
Read Later

    The "Read Later" function allows you to add material to this block with just one click. Just click on the icon and read the articles that interest you at any convenient time.

Top Posts
Rate my site