‘Kicking in open doors’ is a Dutch proverb for doing the obvious. As stern and side doors become ever larger and stay open for longer periods, it was obvious to Feadship that a new approach was required to their design and construction.
It is a familiar sensation for everyone involved in large yacht operations – as you open a large shell or transom door close to the waterline, waves start to slam against the underside. This generates unwanted noise and vibrations that can sometimes be noticed all over the yacht. What’s more, water geysers occur from the gap between the platform and the hull, and incidental waves may flood the beach terrace or the internal space behind it.
Normally it is the captain who decides when it is prudent to open the doors or to keep them closed, and most yacht designers and builders pay little attention to the matter during the design and construction phase. However, doors continue to grow in size and there is an increasing focus by owners and guests on spending time outdoors. This means that, in contrast to traditional tender garage doors, the large hull doors are being opened up for a significant amount of time. This prompted Feadship to embark on an in-depth study of the issue by means of in-house CFD calculations and model testing in cooperation with MARIN, one of the world’s leading institutes for hydrodynamic research and maritime technology.
A better understanding
Extensive model tests were performed on side and stern doors, with varying wave headings and significant wave heights, the first time research of this kind has ever been performed. After an in-depth analysis by Feadship De Voogt experts and the scientists from MARIN, the test results have given us a much better understanding of the situation with open doors. In future design deliberations we are now able to decide on issues such as the best location for given purposes, which wave heights are acceptable and how designs can be optimised to enhance behaviour in waves. This all fits seamlessly within the custom yacht building philosophy for which Feadship is renowned.
Safety-related issues regarding open doors are often addressed in discussions with Flag and Class representatives. What is exactly the risk of an open door? How much water might enter over a certain sill height? For this purpose the in-house CFD tool was used to show the effect of the waves from a passing ship on an anchored yacht in still waters. Again, knowledge was gained and tools developed that have made the Feadship team even more prepared for ideas or questions from designers, owners, captains and regulatory bodies.