The model testing period of designing a marine vessel plays a critical role right from the very basic design stages.
Ship model testing by SEATRANSPORT began in 1986 with bulbous bow developments on catamarans. Various bulb shapes and sizes were tested including pear, circular and elliptical. Hulls without bulbs were also tested.
The most effective bulb improved calm water speed by an impressive 1.5 knots and significantly reduced the motions and accelerations during a sea-state could better maintain head speed in comparison to conventional catamarans and mono-hull vessels.
In 1997, STS won an international tender for P&O in India for a 15-metre passenger ferry. The ferry design required low accelerations at the LCG (the main aspect of sea-sickness, yet frequency dependent) without the use of external appendages for ride control. An efficient hull was required and so tests were undertaken on a 1:3 scale model that proved beneficial.
Additional tests conducted were on varying LCB-LCF separations and locations with a 1:10 scale semi-SWATH model located at the Australian Maritime College’s towing tank. These tests quantified both the accelerations and motions as well as the frequency of the heave and pitch RAOs. The results found by STS correlated well with similar research papers.
Bulb modifications were made and the testing process was repeated, which resulted in a 23% pitch-motion reduction. Vertical accelerations at the LCG were reduced by 15% and considerably more at the vessel’s wheelhouse. Calm-water resistance was recorded post-modifications revealing that very low resistance was maintained.
STS CEO, Mr. Ross Ballantyne, concluded that development and research work should be constant for leading-edge innovations of the Australian marine industry to be sustained into the future.
