Sea cruises are seen as the epitome of an abundance of time and relaxation. It’s a completely different ball game when it comes to running repairs on and overhauling an ocean liner in dry dock. Downtime for these giants is extremely expensive. Any work required must therefore be carried out quickly, and usually all at the same time. However, the dry dock does offer a unique opportunity to inspect the ship’s hull in detail and measure it accurately.
The QUEEN ELIZABETH is one of the most arresting luxury liners in the world. She seam- lessly blends modern ship design with classic elements from the golden age of ocean crossings. Her measurements are impressive too: 294 metres long, 32 metres wide and a magnificent 55 metres high. 12 passenger decks provide space for more than 2,000 passengers.
Following her launch in October 2010, in spring 2014 it was time for a general overhaul at the Blohm + Voss dry dock in Hamburg. The comprehensive cleaning and modernization programme had to be completed within the space of just two weeks. In addition, accurate measurements of the ship’s hull were scheduled to be taken during this time. Data obtained during this process was used to calculate the optimisation of the hull. The goal was to develop new flow flaps and stabilisers and so to improve energy efficiency. In order to keep to the strict schedule and deliver the required accuracy, the contractor in question, SCAN3D Dienstleistungsgesellschaft, recorded the hull using a FARO Laser Scanner Focus3D X 130.
”What was so challenging about this scan was the time pressure and the limited room for manoeuvre in the dry dock”, said Lars Sörensen, Managing Partner at SCAN3D. Sörensen and his team had to integrate into the shipyard’s 24-hour working day at Dock Elbe 11 whilst causing as little disruption as possible. “When we take measurements in shipyards, we mainly have to work nights and at the weekend”, said Sörensen.
With the FARO Focus3D he was able to record the ship’s entire hull in two eight-hour scan processes comprising around 100 individual scans – both from underneath and at various height levels, given that the draught of this luxury liner alone measures 8 metres. “The Focus3D X 130 is ideally suited for working in confined spaces, such as those beneath the keel. It did not take much effort or time to set up, and we did not get in the way of other work taking place around us“. The laser scanner’s high measuring accuracy is incredibly important for the next steps in the process. With a standard deviation of 2.5mm on a ship 300 metres long and range noise in fractions of a millimetre, the laser scanner delivers a highly accurate map of the hull. This level of accuracy is vitally important given that it is not unusual to discover deviations of several decimetres from the planned hull design once the ship has been built. SCAN3D used LupoScan to process the captured data and subsequently produced a reliable surface model of the ship’s hull. Experts at an engineering firm in Finland were able to take this digital model and use it with CFD to analyse flow behavior around the hull. Flow flaps, stabilisers and a new bulbous bow were then designed to help boost the energy efficiency of the ship’s propulsion.
“Our approach had one particular advantage: the data obtained was transformed directly into the ship’s coordinate system. This method produces significant time and cost benefits for future installations”, Lars Sörensen explained. “And the Focus3D enabled us to record basic geometric data quickly and reliably”.