Ship Surface Design Technology. Preparation of Initial Data

The process of designing or fairing a ship's surface begins with the preparation of initial data. Naturally, the initial data can vary significantly and depend on what we intend to do with the surface—whether we are designing a hull from scratch or fairing an existing surface.

The initial data can be divided into two types:

Wireframe model.

Wireframe Model: A model containing two-dimensional or three-dimensional lines that preliminarily define the hull's shape. Such lines may include views from the general arrangement drawing—profile view, deck plans, transverse sections, etc. Sometimes, initial approximations may use scanned drawings in raster formats or even data from a lofting book. Ultimately, these can also be converted into lines and used as a wireframe model. The same applies to 3D scanning data of an existing hull. Obviously, working directly with scan points is quite challenging, but if they are converted into hull sections, they can also serve as a wireframe model. Based on experience in reconstructing surfaces from various initial data, the most convenient for work is a wireframe model based on lines. Raster data from scanned drawings contains distortions and scanning errors that still need to be compensated for. Therefore, the best solution is to prepare lines in advance based on a raster underlay. This allows for compensating for scanning errors and eliminating unreliable results before the surface reconstruction process begins. For this, almost any drafting software with the ability to import scanned data can be used. The process of reconstructing such a surface can be approached in two possible ways:

-Place the lines corresponding to the surface sections in their respective principal planes. Waterlines are placed on the base plane, buttocks in the centerline plane, and corresponding frames in the planes of the forward and aft perpendiculars. In this case, when reconstructing the surface, the same arrangement of sections as in the prototype must be used. This method is more labor-intensive and requires certain skills.

-Place each surface section line in its own plane. This results in a 3D wireframe model, for which automatic approximation algorithms can be used during surface reconstruction.

Surface Model

Surface Model: A model containing not only lines but also surface patches. Such a model can be used both for the initial stages of design and for the final fairing of the hull. The advantages of this model lie in the ability to obtain any point on the surface and any of its sections. In this case, automatic approximation algorithms can be used if available in the software, significantly simplifying the task. Such a model can also serve as a close prototype for a new project. However, it is important to understand that this model is only a prototype and not a definitive guide. The subdivision of a ship's surface into patches heavily depends on the software used. Copying existing patches and editing them is not always the best approach. Typically, the surface patches of a prototype model lack topological connections with each other, and when editing a shared boundary between two patches, gaps must be manually checked and corrected.

The preparation of initial data is a crucial part of ship surface modeling and can significantly influence the final outcome of the modeling process.