Sea Transport Solutions on Design Techniques

ship design techniques

 

Sea Transport Solutions’ CEO, Ross Ballantyne, gave a technical presentation on Queensland’s Gold Coast last year describing some of the ship design techniques used when producing optimum vessel type, size, speed and operation method for commercial transport.

In his presentation, Mr. Ballantyne stated that the technique is focused on the revenue deadweight of the vessel. Revenue deadweight is the deadweight that vessel operators are being paid to carry, such as cars, trucks and passengers – excluding items such as fuel, water and ballast. Firstly, a review is undertaken of the proposed capabilities of the vessel, including speed, range, operational costs, capital costs and sea-state limitations etc. These capabilities are then deconstructed into revenue units and compared to the lightship weight of the vessel. Comparisons are then made with the vessel’s currently operating within the operating market, including both new and second-hand, which are then plotted on a graph to determine the most suitable vessel for the intended operation.

 

This technique is used across for all STS client who is interested in any form of marine operation and ultimately solves the question “whose vessel is better?” with supporting figures that focus on the optimum solution for the intended operation.

 

When STS is asked to find a better solution than what is existing, the technique used focused on finding the faults of the current vessel and how the operation as whole can be simplified.

The example used in Mr. Ballantyne’s presentation was the conventional landing craft, which is often found to have the following faults:

  • Poor head-sea capability due to the bluff bow
  • Poor stability due to low freeboard and low profile of GZ curve
  • Poor visibility due to the forward bow ramp
  • Poor beaching and de-beaching ability due to forefoot suction on the sea bed as well as inefficient propellers while in reverse
  • Operator discomfort and fatigue due to the vibration and noise caused by the machinery room located directly under wheelhouse
  • Ballast is required due to the box-shaped hull and propellers that must be immersed. This results in additional machinery that will need to be maintained.

In comparison, a stern landing craft designed by STS offers:

  • Improved sea capabilities and speed due to a finer bow and hull shape
  • A shallow V hull with two side pods, shafts that are off-centre and beaching-protection aft skeg arrangement that improves that improves de-beaching and propeller efficiency
  • Good forward vision thanks to the high forward superstructure that also helps protect cargo from seaspray
  • The superstructure is far from the engine room, reducing vibration and noise for the operator
  • A V-shaped hull that eliminates the need for ballast and therefore less machinery power and reduced reduced maintenance
  • Cheaper capital and lower operational costs

Ship Model Testing

ferry design

Ship model testing by Sea Transport Solutions 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 sea-state so it can better maintain 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 LCD (the main aspect of sea-sickness, yet frequency dependant) 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.

 

Mr. 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.

For more information on Sea Transport Solutions’ bankable feasibility studies and vessel design services, contact us today.