COMPARATIVE ANALYSIS OF THE HULL RESISTANCE AND PROPULSIVE POWER OF CATAMARAN AND A CONVENTIONAL VESSEL

1.1 Introduction

Catamaran as a surface vessel was not significantly improved from the mid of the last century. Conventional single-hull surface vessels were satisfying more or less sufficiently all sailing requirements. After complex theoretical and practical researches it was established that in relation to the conventional passenger vessels, catamarans offer many advantages related to the space, surface and stability in maritime exploitation. Nowadays, twin hull passenger vessels are common choice of many ship operators pushing out conventional monohulls of the same purpose. The reasons are more than obvious; passenger catamarans completely satisfy requirements regarding space and stability as well as other functional needs of the users. In the sense of catamaran quality evaluation, the most important operation conditions are maximal speed and sea keeping requirements accomplishing safety at sea requirements. However, in the case of rough sea where high angles of heel occur, catamarans have short rolling periods.

As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Research hypothesis and questions, Limitations of the Study and Definition of technical terms.

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1.2 Background of Study

The concept of multi-hull is known to the mankind since ages of sailing. But it took quite a long time to have a scientific look over the pros and cons of catamaran hull design. Speed is the main parameter which resulted in the evolution of multi-hull from the conventional monohulls as the mechanical propulsion came into big picture. In case of monohulls the high speed is achieved by a finer hull which exhibits minimum drag characteristics. A slender hull with high L/B ratio would serve the purpose. This initiated the need of second hull as a supporting structure which led the innovation of catamaran hulls without a compromise between speed and stability of the vessel.

As the twin hulls are finer and exhibits stability efficiency as well as desired speed more than the conventional mono hull design, the researchers have always been interested in the optimized design of the hull to get the desired hydrodynamic performance. When good performance is the output needed from a hull design one should have a great insight in the reduction of resistance characteristics of the hull. Since the catamaran has twin hulls which represents more wetted surface area would also experience more drag characteristics. Also the resistance experienced at slow speeds is much greater when compared to any other conventional mono hulls.

Though the maritime industry is setting a broad exposure in ship designing through advanced technologies and varying simulation software, the research seems to be never ending in producing finer and optimized design of the vessels. When most of the vessels in the maritime industry are dominated by the conventional mono hull design with distinguishing shapes for desired commercial purposes there is always space available for multihull vessels when stability and hydrodynamic performance are considered as the main criteria for rapid express dent of the high-speed ship market in the past decade, multi-hulls are considered as the best option to be used in naval and recreational purposes where performance of the vessel could have a profound effect. Hydrodynamic performance is an important aspect to be taken into consideration as it has direct impact on the operational costs. So, at an early stage a designer need to be aware of finding the best possible method which determines or sets a compromise between vessel shape and operational costs to get the desired performance. Though theoretical approach of hull resistance is complex in nature, it seems economically feasible when compared to model test evaluation.

This justifies the effort involved in studying many different theoretical methods in order to evaluate hull resistance properly (Moraes et al., 2004). The size and shape of the demi hull have an impact on resistance as well as on interference of the vessel. One of the most important considerations for a naval architect is the powering requirement for a ship. Once the hull form has been decided upon, it is necessary to determine the amount of engine power that will enable the ship to meet its operational requirements. Knowing the power required to propel a ship enables the naval architect to select a propulsion plant, determine the amount of fuel storage required, and refine the ships center of gravity estimate. Throughout history, naval architects have endeavored to increase the speed of ships. Increased speed would enable a warship to close with its opponent, or conversely, to escape from an attack. Increased speed enables merchant vessels to reach port sooner and maximize profit for its owner. Until the early 1800’s, wind was the force used to propel ships through the water and ships could only go as fast as the wind would propel them.

Additionally, because ships were constructed of wood, the structural limitations of wooden hull configurations drove hull designs to primarily meet the structural needs while hydrodynamics was only a secondary concern. With the advent of steam propulsion in the early 1800’s, naval architects realized that ship speeds were no longer constrained by the wind and research began into the power required to propel a hull through the water using this new propulsion medium. Testing of full-scale ships and models determined that the power required to propel a ship through the water was directly related to the amount of resistance a hull experiences when moving through the water. The development of iron hull construction produced radical changes in hull strength and hull design. Gone were the blunt bows and full hull forms of early sailing vessels. Capitalizing on the added strength of iron hulls, naval architects could design ships with finer bows and as a result, ship speeds increased.

Therefore, in Nigeria where the research was carried out, the activities that was conducted is to carry out a Comparative Analysis of the Hull Resistance, Propulsive Power of Catamaran and a Conventional Vessel.

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1.3 Statement of Problems

Investigation revealed that most conventional fishing vessel is monohull. Monohull vessel offers some advantages such as reduced resistance hence less power requirement. However, such vessels also have their setbacks such as reduced Tonnage. Hence for core fishing areas, catamaran vessel could be considering advantages due to the added tonnage due to the advantage of double hulls. Catamaran has her own challenge of increased resistance and hence added power requirement. This research work seeks to investigate and compare the resistance and power requirements of both monohull and Catamarans such as to help inform the decision of ship owners.

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1.4 Aim and Objectives of Study

The aim of the study is to carry out a Comparative Analysis of the Hull Resistance, Propulsive Power of Catamaran and a Conventional Vessel. In achieving this aim, the following specific objectives were laid out as follows:

1. To determine the relationship between Hull Resistance, Propulsive Power of Catamaran and a Conventional Vessel;
2. To examine the Resistance and Power of the conventional vessel;
3. To find out the corresponding parameters of a catamaran;
4. To compare technical and technological advantages and disadvantages of the both type of surface vessels; and
5. To present specific procedures of transformation process from conventional catamaran surface vessel.

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1.5 Research Questions

The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:

• What are the Resistance and Power of the conventional vessel?
• What are the corresponding parameters of a catamaran?
• What are the procedures of transformation process from conventional catamaran surface vessel?
• What are technical and technological advantages and disadvantages of the both type of surface vessels?
• What are the relationship between Hull Resistance, Propulsive Power of Catamaran and a Conventional Vessel?

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1.6 Research Hypothesis

In order to pursue the objective of this study, the following generalized statements have been designed to guide and aids in obtaining the result for the experiment to be conducted. For this work, the null hypothesis will be represented with H0 while the alternative hypothesis will be represented with hypothesis H1.

Hypothesis One

• H0: There is no significant relationship between Hull Resistance, Propulsive Power of Catamaran and a Conventional Vessel
• H1: There is a significant relationship between Hull Resistance, Propulsive Power of Catamaran and a Conventional Vessel

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1.7 Significance of Study

This study will serve as total for informed decision making as regards choice of vessel to be built or procured based by prospective ship-owners. It will also serve as a reference material and a reliable guide for further research to students who may be interested in this area or related areas of research.

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1.8 Scope of Study

The scope of the research is focused on the Comparative Analysis of the Hull Resistance and Propulsive Power of Catamaran and a Conventional Vessel.

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1.9 Limitations of the Study

During the course of this study, many things militated against its completion, some of which are:

1. Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
2. Research material: availability of research material is a major setback to the scope of the study.
3. Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
4. Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).