Two high-speed ferries owned and operated by TT-Line Company Pty Ltd, which run between Australia’s Port of Melbourne in Victoria and Devonport in Tasmania, have had a series of hull coating upgrades which are paying off in terms of improved efficiency and lower maintenance requirements. One of the ferries has already had her hull coated with AkzoNobel’s top-of-the-range biocide-free foul release coating, Intersleek 1100 SR, whilst the second vessel will have a similar coating upgrade completed later in 2017.
The two ships, Spirit of Tasmania I and II, operate on this very challenging route, a 249-nautical mile voyage which takes in the harsh conditions prevailing in Bass Strait and the very shallow and speed-restricted water in Port Philip Bay on the approach to Melbourne. From approximately April to December, the two ferries sit alongside their respective berths for approximately 13.5 hours in every 24-hour cycle. The fouling challenge is therefore substantial.
The 194m-long ships run a nightly service year-round and, during about four months in the summer, they also provide a daily service up to five days per week. The ships maintain service speeds of 23 knots at night but are required to sustain a higher speed of 28 knots in open water on the daytime sailings. The two vessels were built at the Kvaerner Masa-Yards facility in Turku, Finland, (now Meyer Turku) in 1998 and were acquired by TT-Line in 2002.
The ships’ hulls were originally coated with a self-polishing copolymer antifouling coating. However, in 2008, TT-Line’s executives took the decision to invest in Intersleek 970 on board the Spirit of Tasmania II. Approximately 5,000 m2 of the ship’s flat bottom and vertical sides were fully blasted during a docking at the Captain Cook Graving Dock at Garden Island in Sydney and the ship’s hull was coated with Intersleek 970. At the same time, the ship’s propellers were upgraded.
“Since we recoated Spirit of Tasmania II and fitted more efficient propellers at the same time, we could not estimate the benefits specifically attributable to the coating upgrade,” explains Captain Stuart Michael, TT-Line’s General Manager of Marine Operations. “However, in 2009 we carried out the same process on board the sister ship, Spirit of Tasmania I, but we did not replace her propellers. We found that efficiency definitely improved as a result of the coating upgrade and the blasting back of many layers of previous hull coatings.”