Drop test in calm water


Full-scale trials Newly built freefall lifeboats should comply with the DNV-OS-E406 standard, which requires full-scale prototype testing to document the lifeboat performance, in terms of forward speed and occupant safety amongst other things.


MARIN has assisted lifeboat manufacturers in performing full-scale drop tests in calm water and waves. Tests in calm water were conducted to show that the thrust capacity of the lifeboat is sufficient to maintain mean direction and sufficient speed. The goal of the tests in waves was to show that the lifeboat can get away in severe waves from different directions and to show correlation with Dropsim. Due to safety and practical matters related to harsh weather trials, tests were mainly done in waves with a significant wave height of up to 6 m. Dropsim was subsequently used to calculate forward speed performance in all other sea states. The main areas of interest during the full- scale drop tests were the accelerations at critical locations and the deflections of the hull and the canopy. MARIN applied its on board measurement system during tests, with which Norsafe’s GES52 was dropped from the world record height of 66.8 m.


Another goal of the drop tests was to collect data for validation of analytical work and model- scale testing. The figure below shows a comparison between the trajectory of the lifeboat during a drop in calm water measured as part of full-scale and model- scale tests. As can be seen, the two trajec- tories correlate very well.


Ongoing work The work described in Report has led to the development of a transparent and consistent method to quantify


the operability limits of lifeboats. MARIN would like to think it has made a significant contribution to safer evacuation procedures with freefall lifeboats. The methodology is currently applied to existing and new lifeboat types. Newly built freefall lifeboats - accor- ding to the DNV-OS-E406 standard - should be tested at full-scale prior to delivery. MARIN has played a role in supporting these trials with measurements of accelera- tions, deformations and the trajectory of the lifeboat.


Comparison between the trajectory of the drop in calm water on full and model scale


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