Archimedes Law

Question 3.
Archimedes set out the fundamental principle that has for a long time guided the construction and study of ships. The Archimedes Law declares that a mass submersed in a fluid dislocates liquid equivalent to the load of the mass (Mégel, Jacques and Janis Kliava 739). The only time a ship is at normal upright structure and stable is in dry anchorage; once a ship sets into the waters, several factors act upon the ship that if unstable the ship may capsize. Stability is the capability of a ship to return to its upright condition no matter the number of external and internal factors that continually affect the stability of a ship afloat (Francescutto 34). Equilibrium is a state that a ship can be; for a ship to be declared at steadiness, a ships mass acting centrally towards the center of gravity (Cog) must be equivalent to the thrust force directed at the epicenter of buoyancy. A ship reoccupies the state of equilibrium when external forces are removed or applied as long as the Cog maintains the same point of application below the metacentric length of a ship (Tupper 73). When a ship’s body mass tilts from the center of gravity, the buoyancy center shifts from point B to B1. Upon slight dislocation of the center of buoyancy, the righting lever resumes the ship to the position of equilibrium.

A vessel is deemed seafaring if it can resume the state of stability effortlessly when in good condition and after destruction. International maritime organization stipulates the standards that a ship must meet to be seaworthy.

A ship deteriorates over time due to wear and tear but even then the engineers must ensure that the minimum stability standards get maintained. The IMO has given the following minimum standards for cargo ships (Brian and Ruben 27). First, the original metacentric length must never get lower than 150 centimeters. Secondly, GZ which is the righting center should be at a minimum 200 centimeters and have a heel angle of more than or equal to 30 degrees (Reed 795). The maximum righting lever occurs at more than 30 heel degrees and should never go below 25 heel degrees as outlined by IMO in the Safety at Sea convention. The GZ area curve should play within 30 heel degrees and 40 heel degrees for radians 55 centimeters and 90 centimeters respectively (Chopra 3). Damaged ship stability varies from ship to ship, but the vessel margin line should stay above water even after the damage.

Question 4

Effective power is the power available at the production side of a ship’s engine (Chopra 3). The effective power of a ship is found at the crankshaft flange of the ship’s engine. The crankshaft connects with the flywheel and the other part of the shaft. Propellers are tasked with the production of propulsion energy thus any effect on the propeller affects the propulsion efficiency in the same ratio (Tupper 57). There are two kinds of propellers, the fixed pitch propeller (FP- Propeller) and controllable pitch propeller (CP-Propeller) (Diesel 15). FP propellers are fixed; hence their pitch cannot be changed hence when the ship navigates in rough weather conditions the propeller performance will curve as much as the propulsion efficiency of the ship. Ships that do not need superb maneuverability are fixed with FP-Propeller. CP propellers have a larger hub as compared to FP propellers since the hub has mechanisms that allow changing the pitch of the propeller. The efficiency of CP-Propeller is relatively small when compared to FP-Propeller due to the large hub. CP-Propellers are used for Ro-Ro ships, shuttle tankers, ferries and other similar ships that require higher maneuverability.

Some of the factors that affect the efficiency of propulsion are wake fraction coefficient and thrust deduction ratio (Bertram 58). Propulsive efficiency is equal to the ratio between towing power and the necessary power delivered to the propeller. Hence, propulsive energy is equal to the product of the hull efficiency. The highest possible propulsive efficiency is obtained by the largest possible diameter for a given ship (Molland, Stephen and Dominic 69).

Efficiency is also affected by Revolution per Minute (RPM) that describes the number of rotations or turns that a propeller makes within one minute. In reality, a high RPM recording does not reflect the efficiency of a propeller. In the case of high-speed vessels, a higher diameter denotes a high drag. For devices traveling at 35 knots speed and under, reduction of the RPM will allow the propeller to function efficiently in addition to increasing the diameter of the propeller. A large diameter achieves a higher torque, contributing to the efficiency of the ship.

Effective power determines the level of efficiency to be experience at the propeller thus the propulsion efficiency. The wrong choice of the propeller dimensions for a ship will reduce the ultimate effective power of a ship (Bertram and Schneekluth 54). Chief among design steps of a sea vessel is the building of the ideal propeller for a ship. Propeller choice goes a long way in optimizing in the power requirements of a ship.

Question 7

In marine travel, the safety of the ship is essential and paramount. In fact, this is the reason that ships should only be allowed to take off if their security is ascertained (Kopacz, Morgas and Urbanski 121). Certain factors ought to be evaluated, for example, the identification of potential hazards at sea. In this assessment phase, shipping safety analysis is conducted, to reveal the risk that Mariners may encounter at sea. The nature and the extent of hazards are determined by factors such as ship size, functions of the ship, category of the ship, external influences, explosion, and other risks that could befall a ship at sea (Wang 83). Evaluation of databases to know previous accidents and their nature helps a mariner anticipate what to do if faced with similar circumstances. The Titanic and Achille catastrophes among others shaped the care framework used by ship in the contemporary world thus; some study of history of the happenings at sea helps understand safety measures to take at sea (Nikcevic 33). In ensuring safety at sea, a safety assessment must be conducted; safety assessment is a continuous process that can also be conducted at sea (Mentes, et al.4).
In 1993, the IMO developed a five-step risk-based approach that would be used for several years since then to conduct formal safety assessment (FSA) (Veritas 3). FSA begins with hazard identification; any potential risk that may be encountered is brought to book to eliminate chances of getting ambushed at sea. No danger is deemed insignificant to be considered at the hazard identification stage. After hazard identification, the frequency, and probability of a risk coming to pass is calculated (Breinholt, et al. 754). Calculation of the frequency and probability must be done as no preparation for danger is enough to rule out the possibility of the inevitable happening of such calamity (Lois, et al. 96). Acceptance of the possibility of happening of a disaster necessitates advancement to the next step of the FSA which is consequence estimation (Veritas 4). A risk in FSA is the product of the probability and impact of a hazard. The third phase of FSA involves identification of risk control options. All steps that can be exploited to avert a disaster are explored at the third level of FSA (Veritas 4). Fourth, the risk control options identified are evaluated together with the potential cost that comes with the implementation of such options (Breinholt, et al. 756). Lastly, a decision is arrived at on the best risk control option that has more benefits as compared to the resources that are channeled to such option. FSA is a structured method with the sole aim of enhancing maritime safety.

Question 10

In the earlier days of naval architecture, the computer was less used than it is used today. The sophistication of the computer in its capabilities has seen significant work of naval architecture left for the computer to handle. Of importance to naval architects is the development of Computer Aided Design (CAD) and Computer Aided Manufacturing applications that are broadly deployed in ship development today (Shah, Jami and Martti 45). Use of computers allows for digital storage of design information. The possibilities that stored digital designs pose are many to the naval architect.
Handling of sensitive information manually is expensive and error-prone (Mistree, et al. 567). Computers come to the aid of data handlers like storage of design prints and other information. Use of computers in naval architecture ensures that there is a continuous flow of consistent data that could have been miscommunicated under a manual data transmission setup. Once basic geometry definition of a ship is stored, the structural engineer has versatile means of for obtaining graphic representations of the structural configuration in use at a given time.

CAD software shortens the production process since the structural engineer will have to retrieve basic geometry that exists (Hockney, Roger and Chris 44). Other computer programs assist in the assembly by lifting, the burden of calculating weight, the center of gravity and forces, from the engineer. Away from ship building, the internet as can be accessed from computers has a lot of resourceful in information such are current regulation on maritime on the IMO website. Ship architecture should at all times abide by the IMO regulations on ship building.

Computers have been used in detecting errors in time, and this enhances safety in ship operations. It is essential to realize that safety in marine travel is a priority for the companies. Marine engineers are determined to construct ships that satisfy the set safety standards (Ray, Gokarn, and Sha 220). Computers have been useful in providing such important detail, leading to the overall safety of ships. Marine engineers appreciate that computers can easily be used for detecting a problem, which is subsequently corrected within a reasonable time. Use of technology helps in identifying areas facing challenges at the right time, and this contributed to a reduction of mishaps as errors are rectified in time.

However, although the application of computer technology in ship design has made a significant contribution to ship designing, innovation, and advancement, innovation in shipbuilding has dwindled (Corser 30). Ship design and building is a process that deserves and demands creativity. The tendency of over-relying on computers does not ignite the creative mind of the ship designers. Over-reliance on computers leaves ship building in a loop as people tend to think whatever the computer comes up with is always right; the future of shipbuilding is at stake if naval architects keep relying on computers for everything (Kuo et al. 250).

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