Ship Design Theory

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Ship design
Ship design

The process of making a ship’s design is an iterative process, which must go through each of the stages that must be met in order to get a good and optimal ship design. This design is depicted on the spiral design. Spiral design divides the entire process into 4 stages, namely concept design, preliminary deisgn, contract design, and detail design.

The Spiral Design
The Spiral Design

1. Concept Design

Concept design or ship design concept is an advanced stage after the Owner requirenent. The ship design concept is the task or mission of the designer to define an object to meet the mission requirements and comply with existing obstacles or problems. Concepts can be made using a formula of approaches, curves or experience to make initial estimates aimed at obtaining estimates of construction costs, ship machining costs and the cost of equipment and ship equipment. The results of this design concept stage are generally in the form of drawings or sketches, either in part or in full.

2. Preliminary Design

The second stage in the design process is preliminary design. Preliminary design is a further technical effort that will give more detail to the design concept. In conjunction with a spiral diagram, this preliminary design is the second iteration or can be said to be the second path on the spiral diagram. The details include features that have a significant impact on the ship, including the initial approach to costs that will be needed. Examples of additional details are the calculation of the ship’s elongation strength, the development of a ship’s midship section, a more accurate calculation of the weight and center of the ship, its density, stability, and so on.

3. Contract Design

The contract design stage is the next stage after preliminary design, which is the stage of developing ship design in a more detailed form that allows ship builders to understand the ship to be built and accurately estimate all shipbuilding costs. The main purpose of the design contract is the creation of documents that describe the ship to be made. Furthermore, these documents will be the basis in the contract or development agreement between the ship owner and the shipyard. The components of the contract drawing and contract specification include:

  • Arrangement Drawing.
  • Structural Drawing.
  • Structural Details.
  • Propulsion Arrangement.
  • Machinery Selection.
  • Propeller Selection.
  • Generator Selection.
  • Electrical Selection.

The above components are also called key plan drawing. The key plan drawing must present in detail the features of the ship in accordance with the request of the ship owner or shipowner.

4. Detail Design

Detail design is the final stage of the ship design process. At this stage the results of the previous stages are developed into a more detailed work picture overall. This stage includes all the plans and calculations needed for the ship’s construction and operational processes. The biggest part of this work is the production of working drawings needed for the production process.

5. Ship Design Methods

In general, the methods used for the design process of a ship include the following :

5.1. Parent Design Approach

Parent design approach is one of the methods in designing a ship by way of comparison or comparison, that is by taking a ship that is used as a reference comparative ship that has the same characteristics as the ship to be designed. In this case, the designer already has the same vessel reference to be designed, and is proven to have good performance. The advantage in the parent design approach is that it can design the ship faster, because there is already a vessel reference so the designer only needs to modify it, and the ship’s performance has also been proven to be good.

5.2. Trend Curve Approach

Trend Curve Approach or usually called the statistical method uses a regression system of several comparative vessels to determine the main size of the ship. In this method, the size of several comparative vessels after being sampled is then compared where each variable is linked and drawn a formula that applies to the ship to be designed.

5.3. Iterative Design Approach

Iterative design is a ship design methodology based on the cycle process of prototyping, testing, and analyzing. Changes and improvements will be made based on the results of the latest iteration testing of a design. This process aims to improve the quality and functionality of an existing design. The ship design process has the most iterative nature described by the design spiral which reflects the design methodology and strategy. Usually this method is used only for certain people (already experienced using knowledge).

5.4. Parametric Design Approach

Parametric design approach is a method used in designing ships with parameters, for example (L, B, T, Cb, LCB, etc.) as the main size of the ship which is the regression result of several comparative vessels, then the total resistance is calculated, designing a propeller propeller, the approximate calculation of the main motor power, calculation of the number of ABK, calculation of center of gravity, trim, and others.

5.5. Optimation Design Approach

This optimization method is used to determine the optimum size of the main ship and the motor power requirements. In this case, the optimum design is sought by finding a design that will minimize economic costs (economic costs to a minimum). The parameters of this optimization are the laws of physics, loading capacity, stability, freeboard, trim, and the price of the ship itself.

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