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Sea Speed

Project title:
Model testing to support development of the new fast all-weather Shannon Class lifeboat

The Royal National Lifeboat Institution - RNLI

To select a new Shannon class hull form with significantly improved up-sea capabilities, by undertaking a detailed comparison of the performance characteristics of a range of existing against new hull form alternatives.

• A self-propelled model of the existing RNLI vessel was built, instrumented and tested to provide evidence of the veracity of Seaspeed’s open water test techniques.
• Six fully instrumented self propelled models were then run side by side with the existing design in open water, with statistical and event data collected for comparison and assessment.
• Runs were undertaken over a range of speeds in measured sea-states at head, bow, beam, quartering and stern headings.
• The models were also run in calm open water to define their manoeuvring and dynamic stability characteristics and in a towing tank to study their powering performance and specific event mechanisms, including slamming and spray generation.
• Shallow water operations and beaching trials in rough sea conditions were undertaken to investigate the handling issues involved in vessel recovery.

• Initial open water model testing of an existing RNLI craft design provided stunningly convincing evidence of the seakeeping problems that had been encountered at full scale.
• Event analysis, similar to that used in automotive crash testing, applied to head sea slamming and stern sea broaching, provided a new insight into these phenomena.
• Side by side open water testing of free running self propelled models provided the visual, statistical and event data required for an in-depth technical assessment of the seakeeping performance of these high speed craft.

• The final hull-form developed from these test results provided a quantifiably significant improvement over existing designs, particularly in relation to hull slamming in fast up-sea conditions.
• Subsequent full scale sea trials undertaken by the RNLI verified the power, speed, handling, manoeuvring and seakeeping predictions made from the model test programme.

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