yachting Yachting focus:


Onboard comfort and Dynamic Positioning


MARIN carries out a significant number of projects in the motor (or sailing) yacht sector. Here Report outlines a favourite subject of interest - comfort – as well as a relatively new area for motor yachts, Dynamic Positioning.


I


n the offshore industry the use of Dynamic Positioning (DP) is fully inte- grated and MARIN has played a large


role in the development of numerical and model testing techniques for these DP systems. Nowadays, the yachting industry is increasingly seeing the benefits of DP and MARIN is keen to help in this new development.


The operational scenarios for yachts where DP is important are different to those of other vessels. In yachting DP is important for position and track keeping, in heading assistance, (e.g. when anchored to avoid fish-tailing), and for manoeuvring under “joystick control”. This allows the yacht to make specified surge, sway or yaw mo- ments with a single “joystick” command. Heading assistance when anchored and manoeuvring under joystick control is usually the most relevant as yachts are often operating in confined bays or har- bours, where manoeuvring and anchoring accuracy is very important.


The operational scenario will influence what kind of onboard installation (e.g. thruster and rudder arrangement) is needed. It is paramount to decide this early on in the design process.


Quantifying performance The hydro- dynamic performance of a DP system can be quantified in many ways: - The maximum average environmental loads in which the position or heading can be kept (defined as wind speed, cur- rent and waves). We consider wind being the most relevant for yachts.


- The speed or rotation rate that can be achieved when in joystick control mode.


- The maximum position or heading deviations occurring in a specific environmental condition.


- Comfort onboard while using the DP system.


For yachts, the maximum environmental loads that need to be withstood are not necessarily very demanding. However, the


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Typical DP capability plot – max. sustained wind speed [m/s] versus heading [deg]


30 10 20


yacht should be able to use DP in complete comfort and with great accuracy to operate in confined areas. There are several ways to study DP including numerical static capabil- ity analysis, numerical dynamic analysis and by physical scale model tests.


In most cases, static numerical capability calculations can already be used to deter- mine performance and to suggest possible design improvements. But as the require- ments increase, more sophisticated tools are needed. Contact: Rogier Eggers, r.eggers@marin.nl


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