Should cruise ships have a double hull ?

Considerations on the Costa Concordia accident

The recent accident involving the cruise ship Costa Concordia on the Italian coast of the Giglio Island is producing the usual questions that arise after any disaster affecting human lives. It is the question of whether the safety of the facility in question is sufficient, be it either a ship, aircraft, train, skyscraper etc. Clearly there is not a complete safety in any order of life, but it is also clear that any current safety level can be improved and the issue is deciding when and where the laws and regulations governing safety are to be changed to get better expectations.

History teaches us that mankind is learning the hard way. When we suffer a great accident is when we consider that perhaps safety provisions are not adequate and should be analyzed in detail and realism to decide whether they should be improved.

Ship lightweight Calculation

(In cargo ships preliminary design)

Introduction

The calculation of the ship lightweight and her center of gravity is one of the basic tasks to be performed in the ship initial design stage, where it is advisable to be able to perform quick, approximate calculations, allowing to quickly analyze many alternative dimensionings. In this blog I present a form to enter the main dimensions of a cargo ship from which the program computes, approximately, the ship lightweight and center of gravity height broken down in Steel, Equipment and Machinery. Results are limited to ships up to 320 m. length between perpendiculars and aspect ratios should be normal.

A  model of the frigate "Blas de Lezo"

by Juan Carlos Gorostiza

 In a former post on my blog "Oteando desde Getxo" (Scanning from Getxo), I presented some ship models manufactured by my friend Juan Carlos Gorostiza, which bind to the charm inherent to any ship model, the simplicity of the construction methods used by Juan Carlos, what makes doubly attractive the contemplation of his models with the awareness of his techniques. But note that simple methods do not mean this is an easy job, much less. In my opinion it is doubly worthy achieving so good results when the methods are so affordable.

Ship's hull form coefficients

(At preliminary merchant ship design)

Introduction

HELLO!

Herein I present a form to get basic hull form coefficients of merchant ships, following the formulae and concepts explained in Refs. 1 and 2, in order to serve as a guidance in the preliminary stage of a ship's design.

The main goal of this form is to get reasonable values of block (CB), midship section (CM) and loadline (CW) coefficients to be used in the different modules presented in the program Arqnaval, enclosed to the book Ref.2, and the program Getxonaval, being under construcion, to be used on-line via any browser, both intended to offer approximate and quick calculation methods in the preliminary stage of a ship design.

Some additional coefficients are also calculated and displayed in the enclosed form, of a lesser interest but that can also be of some utility.

Stability Calculation

(At preliminary stage of cargo ships design)

Introduction

Calculation of the stability is one of the basic and primary tasks that are to be done at the initial ship design stage, where it is not absolutely necessary to be quite exact, but where a quick calculation is very advisable, even if being approximate, allowing to analyze many alternative dimensionings in a short time. In this blog post I enclose a form where main cargo ship dimensions are to be input by the user and from them the program makes an approximate calculation and stability results are displayed for transverse metacentric height GM and righting levers GZ at several heeling angles.

Freeboard calculation

(At the ship design stage)

Introduction

Calculation of the freeboard is one of the basic and primaries that are to be done at the initial ship design stage, where it is not absolutely necesary to be quite exact. An approximate and quick calculation is therefore very suitable. After a brief concepts reminder I enclose a form where main ship dimensions are to be input by the user and freeboard results are displayed.