# Using Digital Twin in a Shipbuilding Project
## 4 Using Digital Twin in the Shipbuilding Process
### Digital Twin Application  
To analyse the results of the Digital Twin implementation in the shipbuilding process, this research, through the data collection method, compares the data of two new build projects [28], selected from the production program of the observed shipyard--a passenger and a cruise ship. The basic ships' parameters are shown in Table 1.  
The new builds are intended to transport passengers with cabin accommodation and are very similar in terms of outfitting complexity. They were realised under the same production and spatial conditions and with the same infrastructural possibilities (horizontal and vertical transport). Therefore, they have the approximately same dimensions and maximum possible weights of assembled sections, i.e., blocks. Furthermore, it is assumed that there were no differences in workers' skills in the realisation of the subject projects, with an emphasis on the level of expertise when implementing assembly activities. The basic difference in the realisation of the two projects mentioned above is that for the design  
Figure 6: Digital Twin ship prototype. Figure 7: Digital Twin development phases. and construction of the cruise ship, a 3D model was used, but using the Digital Twin form and content, respectively. Figure 8 shows the duration of the passenger vessel, i.e., cruise vessel shipbuilding phases in relation to the main events, while Table 2 shows the duration of the outfitting stages with an expressed ratio. Table 3 shows the number of working hours spent for outfitting professions, the total number of working hours spent on welding, as well as the number of production working hours spent in total during the shipbuilding production process. During the realisation of both observed projects, work equipment and machinery of the same models and characteristics were used (specifically--welding machines) as well as the same type of temporary energy equipment (ventilation and lighting in the ship's spaces). The Metal Inert Gas (MIG) procedure was used for the large majority of welding activities in the projects; therefore, to simplify the analysis of results, we assume that all spent welding hours (Table 3) relate to this procedure. Likewise, and based on empirical and statistical data of the shipyard observed, and for this research, it is adopted that the effective daily work of welding electric arc, i.e., the welding machine, is 2 h. The average electric power of the standard welding machine operating by the M \begin{table}
\begin{tabular}{c c c} \hline \hline
**Items** & **Passenger Vessel** & **Cruise Vessel** \\ \hline Length overall, Loa (m) & 168 & 128 \\ Breadth, B (m) & 30 & 21.5 \\ Draught, T (m) & 6.7 & 5 \\ Gross Tonnage, GT & 41,700 & 13,760 \\ Compensated Gross Tonnage, CGT & 38,135 & 29,050 \\ Deadweight, dwt (t) & 11,300 & 1644 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Principal dimensions. Figure 8: Shipbuilding duration in relation to the main events. Furthermore, according to the data collected by the observed shipyard, under the assumption that four outfitting workers work (welding activities included) in the space of nearly 120 m\({}^{3}\), it is necessary to have one exhaust fan operating to ventilate that ship's space while the outfitting works are performed in the assembled block before lifting it onto the slipway. In contrast, while the outfit assembly works are carried out on board after launching, one exhaust and one supply fan are needed to ventilate the same outfitting space. The average electric power of the supply fan models used is 11 kW and 7.5 kW for exhaust fans. The required air exchange per worker in a flow of 3400 m\({}^{3}\)/h is prescribed. Furthermore, each worker needs one mobile lighting fixture to illuminate the observed unit volume of the block space during the on-block outfitting before lifting it onto the slipway, while an average of four light bulbs of general lighting are used when outfitting the ship after launching to illuminate that same area.