concerned structural strength, motions or powering. At that time we were talking about 8-9 metre propellers, much higher power and consequently more cavitation, compared to what the maritime community was used to.” In that period CRS performed mostly experimental work at full scale, but also at model scale.

Then followed a period of about a decade during which specific phenomena were addressed that were also important for other types of ships - strength issues, manoeuvring, cavitation etc. That work was mainly conducted at model scale.

Stability is one such phenomenon and CRS has had several working groups looking at this issue over the years. Jan comments: “I think stability has always been a little neglected historically. In the 1990s stability issues were highlighted as the shape and size of ships changed. We had rolling and heeling problems on high-speed container- ships sailing in following seas. These ships, which were 300 m + long, and could be sailing with a full stack of TEU and yet for the stability calculations, we were using the same formula that was used in the 1800s!”

Computer codes CRS has also studied this issue for various navies, as frigates have similar problems. “What is the ultimate stability, the moment just before capsizing? We clearly can’t do this by model tests or at full scale,” Do says. The big boost in solving these issues came with the development of computer codes and these were applied in the various CRS projects, he adds.

Being typically modest, they don’t like to boast of CRS’ achievements. But Do does say, stability is perhaps one area where it is possible to see where CRS has made a difference. Projects have led to improved design procedures and the classification societies have then used the findings to improve stability rules. “This is especially important in the early design stage. CRS members can perhaps estimate the power requirements better and play with the ship dimensions, and this is all before the design

6 report

Model test with a segmented ferry using a flexible backbone, ELAST project (1990)

is offered to the customer. The members integrate the results in their daily business and that is the beauty of CRS.”

Between 1985-2010 there was much interest in design methods for various ship types. “The CRS working groups were examining design methods for ships like fast monohulls, catamarans, trimarans and SWATH ships.” From around the mid- nineties we moved on towards applying more computer simulations and developing software tools, thereby replacing much of the experimental work at model scale, he says. At the same time, the interest in experiments at full scale has increased, as this is important to validate predictions made by computational tools, adds Do.

Industry revolutions Additionally, CRS also addresses ‘ad hoc’ problems such as what happens in a crash stop situation with fixed pitch high skew propellers. Soon after the oil spill of the Exxon Valdez in Alaska, CRS performed a working group which investigated various alternative designs of oil tankers, aiming at preventing an oil spill after collission or grounding.”

The MARIN team says that CRS has an important role in bringing the ‘outer industry revolutions’ into daily practice.

Jan explains: “There is always the drive from outside, for instance if you consider the game-changing computer developments. In the future we maybe ask, ‘Can we get a ship out of a 3D printer? Is this viable?’ ” And although of course, this is not likely, he says computer developments have made a huge difference. “Consider CFD, this was a massive leap forward. Previously we would have to consider dividing vessels into 20 sections, and make calculations for each of these, but now I believe computers can calculate 1 million panels! Perhaps we even get to the situation when we can calculate motions of individual molecules. But then we have an abundance of data, too much. But at CRS we always have to make ourselves familiar with new ideas.”

CFD Do agrees: “At CRS we have always been somewhat dependent on computer hardware, which was in its infancy in the early days. Then in the 1990s software became more powerful, which made

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