Building a variable depth swimming pool for Superyacht Vava II

Vava II is one of the world’s most impressive and luxurious superyachts. She was being built by Devonport Yachts at Babcock’s Yard in Devonport.

Among the many advanced features that had been specified by the client was the construction of a variable depth swimming pool. This would be achieved by raising and lowering the floor of the pool to four predetermined levels: Adult, Family, Toddler and Deck. At the uppermost “Deck” position, the pool would become a dance floor for parties – complete with light panels!

To achieve this required the use of highly sophisticated water hydraulics. Since Devonport Yachts’ engineers had no experience in this specialist field, they asked Armada to prepare proposals for building the hydraulic system. This unique project set our team a number of challenges:

• The pool is a stainless steel tank, lined with glass panels, with the pool floor being raised and lowered by a scissor-lift mechanism.
• The lifting mechanism would all be within the pool itself and would be immersed in chlorinated water. Water would be used in the hydraulic cylinders for the scissor-lift, to avoid contaminating the pool water.
• A mechanical ‘cleat’ mechanism would lock the pool securely in place at each level and the cleats would be released hydraulically. A set of eight hydraulic lock cylinders would secure the floor in its uppermost ‘Deck’ position.
• The movement of the floor would need to be very accurate to avoid damaging the glass sides of the pool – with only a 10mm gap between the moving floor and the glass.
• Chlorinated water is very corrosive and the switches and transducers providing feedback for control of the floor would be permanently immersed.
• The three functions of lifting/lowering, operating the cleats, and securing the locks would have to be very accurately controlled.
• The whole system was to be operated by a touch screen adjacent to the pool and integrated with the other pool controls such as water quality and temperature.
• Due to earlier delays in the construction of the pool, the Armada team had less than six months to design and build this unique new system.

Armada worked closely with Water Hydraulics Ltd, who had supplied the original cylinders for the scissor lift. A complete list of required equipment was drawn up, some of which had to be specially made for the project.

The scissor lift had two separate (port and starboard) arms to control the balance of the pool floor. Each arm was driven by a separate pump, so that we could achieve very slow and smooth movement of the pool floor. One pump was designated the ‘master’ pump and would also drive the cleats and locks. The pumps were built into a stainless steel reservoir to form a stand-alone power unit.

The power unit, its electrical controls and solenoid control valves were fitted in machinery space adjacent to the pool. The positional feedback for the floor was achieved by four ‘draw-wire’ linear encoders, one at each corner of the pool. Two lift cylinders were used for each scissor arm, to give the necessary power.

Control of all these functions was achieved using an Allen Bradley programme logic controller and a remotely mounted touch screen control panel. The floor is controlled to within plus or minus 10mm from dead level during all of its movements.

Joff Collins, Armada Engineering Managing Director, says:

“It was a real privilege for our team to be involved in such a prestigious and challenging project. This is a custom-designed hydraulic system that is very much one of a kind. To achieve the right result, we had to meet a range of very exacting technical specifications.

“It is a great illustration of the unique skills that our engineers possess, the creative thinking that they can apply to tough problems, and the way that our business can diversify into new areas.

“After our engineers carried out all the required testing and fine tuning, the system was successfully commissioned on schedule. The new pool has proved to be a huge success with the owners and their family and friends.”