Reverse engineering techniques for trawler hull 3D modelling and energy efficiency evaluation

A large number of fishing vessels is not so efficient due to outdated technologies. Nevertheless, European Commission restrictions prevent new constructions, chiefly relating the major opportunities for reducing fuel consumption to retrofitting existing vessels. Improving the fishing vessel’s efficiency at acceptable levels calls for technical interventions, these last are hard to be planned without basic information regarding the hull and the machineries installed on-board. In fact, in most of case construction plan, propeller drawings and engine performance maps are often not available to the designer. These lack do not allow for hydrodynamic and propulsion optimisations. In this context, a reverse engineering procedure is needed to first measure and then to reconstruct the shape, dimension and semantic information of the ship hull, rudder and propeller. The photogrammetric technique is employed for obtaining dense and accurate 3D models of free form vessel surfaces from digital images in accurate, flexible and economical way. At the same time, a manual measurement campaign is developed and carried out to scale and validate the photogrammetric model somewhere dealing with critical issues such as poor light/visibility and obstructed space around the object. Both imaged-based and direct measurement methodologies for 3D reverse ship hull modelling are proposed and critically compared to evaluate and choose the most appropriate and cost-effective re-engineering method for the studied shipbuilding ashore application. Eventually, the data coming from the photogrammetric model has been used to characterise the vessel. This is the first working step to study a possible technical action to increase the vessel energy efficiency.