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Bluetech Finland

Rethinking Basic Design

On a cold winter’s day in January 2018, a 158 meter RoPax for Molslinjen in Denmark was launched at the Rauma Marine Constructions shipyard in Finland. Bluetech Finland Ltd.’s innovative design team pioneered the use of CADMATIC Hull 3D modelling software for the vessel’s hull basic design to form the backbone for approval drawings. The same model was used as the framework for hull detail and outfitting design. Bluetech delivered the full scopes for structural basic design and structural production design for the vessel.

Bluetech designer, Otto Koivisto, used the RoPax project to conduct a study on the implications of using CADMATIC Hull 3D for basic design. The results of his study and the optimized modelling process he developed, as well as its effect on improving overall design efficiency, are contained in his highly rated master’s thesis. 

Breaking from tradition

The basic design of RoPax type vessels is usually done in 2D, typically with tools like AutoCAD®. 3D modelling, on the other hand, only features later in the design process.

When Bluetech Finland received the order for the basic design of the Molslinjen RoPax in June 2016, the daring design team, nevertheless, decided to break from tradition and introduce 3D modelling at a very early stage of the design project. As Bluetech was commissioned to deliver both the basic and production design, they were encouraged to try something new. They were motivated by their strong belief that they could manage the challenges involved and that the advantages would be felt beyond basic design throughout the entire design process.

“We wanted to benefit from using 3D modelling as early as possible and save time also in the later design phases. The crux was ensuring that the 3D models produced, as well as the tools used in hull production design could be applied in structural basic design too. We were convinced that we could do this, even though we had not done it before,” Otto describes the thinking behind the decision. 

Construction of the Molslinjen RoPax ferry. Picture © Rauma Marine Constructions.

Challenges in updating models

The most challenging aspect of implementing 3D modelling in basic design was the amount of effort required to keep the model up to date. Key to success, in this regard, are methods that help to minimise updating needs.

“When you only have one drawing and create a model based on this drawing, it is simple and fast. As soon as the model needs to be updated frequently, however, it becomes very time consuming. It can also be confusing if some parts of the model are up to date, and others are not. We basically needed to come up with a solution to reduce the amount of information that needed to be updated during the design process. That is why I developed an optimized modelling process that postpones some modelling to the point where it is absolutely necessary. This helps to keep the model as light as possible, for as long as possible,” Otto explains the need for an optimized design process.

The optimized modelling process avoids modelling too early in a project schedule. A large matrix of the entire design process was created to identify what elements were really needed in the process, when they were needed, by whom, and how the information could be created following lean principles such as just-in-time (See Diagram 1 for a summary of the optimized modelling process).

Diagram 1. The hull 3D model life cycle in basic design.

“Once you do the basic designmodelling according to the smart process, you avoid problems associated with having a model that is unnecessarily heavy early on. Then you can more easily reap the benefits that 3D modelling brings to hull design,” Otto adds. 

Advantages of using 3D modelling tools for basic design

According to Otto, there are several advantages of using the same 3D modelling tools for both the hull basic and production design. He considers the findings of his thesis as definitive proof that CADMATIC Hull can deliver these advantages. 

“Modelling visualizes the project progress and increases the quality of the design. You make fewer mistakes in 3D, especially in narrow spaces and high curvature areas. Furthermore, you can utilize the model for structural analysis (FEA). It is possible to export the structural model to different file formats that can be imported into FE-software,” Otto explains. 

CADMATIC 3D steel model of Molslinjen Ropax ferry

“My study provides solid proof that CADMATIC Hull can handle basic design.”

Another big advantage is that information for production planning, such as weight and center of gravity are obtained quite early from the model. This information can be used to plan how the hull will be split into blocks and to develop the construction plan.

“You can also get information for production planning using reference ships, for example, but it is much easier and more accurate to use the model for this purpose. This project provided us with proof that you can use the weight information from the CADMATIC Hull model, provided that the model is correct, and its information content is homogeneous. You just have to estimate certain aspects if they are not complete, but if you follow the optimized modelling process you will know how to do that”, Otto reveals.

The biggest benefit with 3D modelling in hull basic design is that it significantly reduces the work required later in detail design.

“Once you can utilize the same model from basic design to detail design, as we did on this project, you don’t have to model the whole structure again for detail design purposes. You can apply the robust basic design model and just refine it by adding new parts and features up to a detailed level.”

Findings are applicable to other modelling systems too

Otto’s thesis was based on the use of CADMATIC Hull software, but he indicates that the results are equally applicable to other 3D modelling systems, provided they have the same capabilities.

“Several software vendors market their systems as being able to handle basic design and that their models can be used later in the design process. These systems are very different though, and some are better than others. Actual cases of the advertised capabilities are often hard to come by. My study provides solid proof that CADMATIC Hull is suitable for this purpose if the model can be kept as light as possible early on,” says Otto. 

Another interesting aspect of the design project was that the outfitting design was done in AVEVA OUTFITTING™. The CADMATIC Hull models were successfully exported by Bluetech for the completion of outfitting design.

The Molslinjen RoPax ferry was launched at RMC shipyard in Rauma on 5 January 2018. Picture © Rauma Marine Constructions.

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