# Using Digital Twin in a Shipbuilding Project
## 6 Conclusions  
Current trends in the maritime market define sustainability as a major factor in competitiveness, with demands on energy-efficient and environmentally friendly vessels manufactured in the same environment. Today's shipbuilding industry is focused on the growing presence of research, development and innovation activities in its business for the purposes of technical and technological improvements in the production process, aiming to achieve cost reductions and energy savings, and having available the digital technologies of Industry 4.0 as appropriate tools above all. This research presents the importance of 3D modelling in a virtual environment by comparing the process of building and outfitting a passenger vessel and a cruise vessel in the observed shipyard. The research analysis is focused on a change in the number of working hours engaged for the outfitting activities and a change in the electric energy consumption during the shipbuilding process. Designing and building a ship in parallel through its 3D model in the Digital Twin form allowed ship outfitting in the earlier stages of construction up to a level of approximately 70%, which improved the productivity in the project realisation process by approximately 20%. Furthermore, 20% savings in electrical energy consumption were achieved only in relation to the scope of this research, thus reducing CO\({}_{2}\) emissions by 1140 t over two years. Additionally to that, as the result of advanced outfitting improvement, the injury frequency rate decreased by about 43% and the injury severity rate reduced by five times. Even though quantitative analysis of the savings considering the vessel's insurance, fire and safety protection as well as financing costs were not included in this research, their significance are presumed; therefore, further study of this subject is recommended. Although the proportion of errors in assembly activities was significantly reduced, from 50% to as much as 90%, depending on the outfitting profession, further improvements are possible by applying Augmented Reality (AR), in which direction further research is proposed to be performed. Furthermore, based on the realised savings in the number of outfitting working hours, it is assumed that the duration of the project realisation process is shortened; following that, this research should be expanded in order to define the method of process duration determination while considering the expected extension of the preparatory (design) phase. Additionally, this paper does not consider the impact of the need for earlier outfit procurement regarding the usual construction intervals between the main events (milestones) and the associated contractual payment schedule; therefore, the authors propose further analysis to adjust cash flow to meet outfitting dynamics. This study targets in particular shipbuilding systems with cruise vessel, naval and/or mega-yacht new build programs because in the majority of shipyards within the subject market niche, outfitting activities are performed in the later stages of the building process, mainly on board on the berth/slipway or even after launching. One of the reasons for the division of such outfitting activities is either because of the complexity of piping and electrical systems, as well as the commissioning program at the quay (navy vessels), the large number of modifications in outfitting (mega-yachs) or the high ratio of subcontracted works on a turnkey basis (cruise vessels). Moreover, due to the afore mentioned payment schedule that is contractually commonly applied, i.e., 5 times 20%, whereby the instalment distribution is in relation to the main events, shipyards are aiming to reach the steel cutting milestone, as well as the keel laying and launching events, as early as possible, with an increase in savings (man-hours, energy, etc.) that could be achieved by implementing advanced outfitting in the earlier stages of ship construction, particularly during the sections and blocks's erection.