Sea trial is the first opportunity the Riviera team has to ensure that all systems on board a new yacht are performing as projected. It is a highly focused and detailed inspection and is conducted on every new Riviera before she is handed over to her owner.
The process is even more intense on board the first of a new model, especially on the new 78 Motor Yacht.
We stepped on board with a team of 10 technicians and engineers at Runaway Bay Marina on Queensland’s Gold Coast. The yacht was without her interior furnishings, allowing the team access to every part of the yacht.
The 78 Motor Yacht touches the water at Riviera’s Gold Coast facility, in preparation for her sea trial.
Riviera’s Design and Engineering Director Dan Henderson explains that, on this trial, she was carrying a full load of fuel and water. Two bladders filled with water and weighing 500 kilograms were secured on the foredeck to simulate the weight of a tender secured over the deck’s lounge space. A davit capable of lifting a 500kg tender and outboard motor was fitted to this yacht’s foredeck.
With a team of 12 people on board, she was also carrying considerably more people that an owner might normally expect on a cruise.
The Riviera sea-trial team passes through the Gold Coast Seaway in short, choppy seas with the vibration testing under way.
Once every person on the team was safely aboard, the detailed monitoring began. Technicians and engineers from the MAN diesel engine company studied laptop computer screens, scanning data from the engines as the yacht motored at a steady 10 knots out onto the enclosed Broadwater. They watched engine coolant temperature, oil pressure, exhaust back pressure, turbo boost pressure and a wide range of other data as they called upon the captain to increase engine revs in carefully controlled increments – 600 revs per minute, 1200, 1600. At each call, the captain carefully edged the throttle controls forward and watched the engine revs climb until they reached exactly the required point. Every piece of data was immediately fed to technicians at MAN headquarters in Germany for comparison with stored data from many other trials.
Studying the yacht's attitude was achieved through a visual check by the team as they leaned over the flybridge deck to observe the wake.
At the same time, a team from Twin Disc was monitoring the engine gearbox performance through laptop computers. One technician sat close to the captain, studying laptop data and comparing it with information being displayed at the top of the four 24-inch screens spread across the helm dash.
Once they were satisfied, the yacht’s vital speed tests were carried out. The captain steadied the yacht, turned and straightened her bow. He pushed the throttle control all the way forward and the team watched the large screens. She began to accelerate slowly, gaining momentum: 25, 28, 30, 31, 32.8. With one run complete, the captain turned the yacht again so she was facing in the direction from which we had come. Throttle down again. All eyes on the digital read-out: 25, 28 and so on. Then 33, 34 and 34.2. An average of 33.5 and Mr Henderson smiled. Part of the purpose of this test was to ensure the propellers are the correct size: 40×49. Perfect.
Then the Twin Disc technician asked he captain to perform a ‘crash test’. No, not running aground. The entire team was warned to brace. He took the yacht to full speed and then suddenly pulled the throttles back to neutral. The yacht stopped quickly and the Twin Disc technician checked his watch. Counting seconds. At 12 seconds, everyone relaxed and we discovered that the Quickshift system prevents a captain from putting the yacht into reverse from speed. The system is designed to release the throttle after 12 and allow reverse by which time the yacht is stationary and the engines are at idle.
Then came the true sea trial. The Riviera safety officer again took the team through a checklist to ensure we all knew the offshore drills including where life jackets are stowed and how to fit them.
We headed through the Gold Coast Seaway into short, choppy seas with virtually no swell, a significant test for the yacht's interior build.
Then we headed through the Gold Coast Seaway into short, choppy seas with virtually no swell, a significant test for the yacht’s interior build. Craftspeople were dispatched to all cabins to listen and look for movement, for any latches that may come loose. Nothing to report. She was solid in spite of the bumpy ride.
This stage of the test also involved tight turns, checks on the Humphree carbon fibre stabiliser fin performance and the behaviour of the yacht in sometimes difficult seas. This involved switching the stabilisers on and off. With stabilisers off, the yacht leaned gently into the turn, perfectly safely and comfortably for the crew on board. Then, in the middle of a turn, the captain would enable the stabilisers and the yacht smoothly came upright.
The 78 Motor Yacht demonstrated very low vibrations as tested by Dan Henderson and his team during the sea trial.
Next came study of the yacht’s attitude through various trim tab and speed settings. The only way to undertake this important task was simply to lean over the flybridge deck’s padded aft rail and study the yacht’s wake. It was an odd sight to see a group of men braced against the rocking of the yacht simply, apparently, staring at white water. But the information they gained was quickly noted for further study at the design studio.
Back on the Broadwater, Mr Henderson conducted a vibration test. To the untrained eye, this, too, is a very odd sight. Mr Henderson took an instrument with a small monitor screen, a cable and a small module on the end. He sat on the floor almost under the captain’s seat and placed the module upright on the floor right under the seat! He later explained that this is the central point on the yacht most likely to pick up any unusual vibrations on board.
Decibel (sound level) tests would be undertaken only when all the furniture, bedding and soft furnishings were brought aboard the yacht. Mr Henderson pointed out that furniture always dampens noise and the only fair test is with the yacht in her final state of fitout.
The data collected during the sea trial was returned to the design studio, shared with the engine and gearbox suppliers and translated into fine-tuning of the yacht so that, when her new owner steps on board and heads out to sea, everyone is certain she will deliver optimum performance.