In mid-July this year, DTA along with the Naval Engineering Authority (NEA) conducted a trial aboard HMNZS Canterbury to assess her seakeeping characteristics in higher seas such as those typically experienced in Tasman Sea crossings.

The NEA is a unit of the NZDF that oversees naval engineering within the Royal New Zealand Navy. It is made up of civilian and uniformed engineers and naval architects. DTA works closely with them on projects relating to engineering in the Royal NZ Navy.

The trial was used to gather data for input into the seakeeping model, which will give ship operators a better understanding of a ship’s seagoing and handling characteristics in higher sea states. This will in turn inform operational guidelines that better reflect a ship’s true performance in rough seas.

To do the trial, a specialist motion reference unit was installed in the ship to precisely measure the ship’s roll, pitch and heave characteristics. A DTA researcher on the project said they carefully considered the trial location. They selected the Bass Strait off the coast of Tasmania because it had the most suitable sea conditions in order to collect a representative data set.

Alongside in Sydney
Sea conditions in the Bass Strait

The biggest challenge was identifying a suitable trial window that had the right sea conditions for a long enough continuous period to conduct the trial. Accurate weather forecasts were vital to plan for the activity which involved up to 12-hour transit times from the staging area to the trial area. While most parameters of the experiment could be tightly controlled, weather was the most significant variable that could not.

The trial was successfully completed; all the trial serials were completed without interruption and data was accurately recorded by the sensors. As well as ship motion data, the researchers collected wave buoy information to generate and validate a high-fidelity seakeeping model of the ship. Sea state 5 was observed, that is, the ship experienced 2.5 to 4 metre significant wave heights.

Entering Sydney Harbour

The motion data collected from the ship will also support DTA research in international collaborations.

Weather was the most significant variable that could not be controlled.

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