Naval News reports that the French shipyard OCEA has launched the largest aluminum offshore patrol vessel ever constructed. It is going to the Philippine Coast Guard as part of a package deal that also included four much smaller patrol boats. The shipyard claims substantial lifecycle saving in fuel and maintenance as well as lower emissions due to the choice of building materials. (Note the underwater body on the after third of the ship. It looks unusual.)
Choice of an aluminum hull and superstructure does bring on discussion of the possible dangers of using aluminum, frequently blamed for serious damage due to fire including USS Belknap (CG-26) and loss of British type 21 frigates HMS Antelope and HMS Ardent and the destroyer HMS Sheffield during the Falklands War.
There are real issues with the use of aluminum, since it softens, melts, and looses its structural integrity at lower temperatures than steel, as seen on HMS Amazon when it had a fire in 1977, but losses as a result of structural aluminum have frequently been exaggerated. Problems with cracking of aluminum superstructures have been largely as a result of the different expansion rates of mixed steel and aluminum construction.
In the case of Belknap, the collision severed fuel lines running outboard on the carrier and dumped huge amounts of fuel onto the ship, feeding the fire, while ammunition cooked off. Nevertheless the ship was saved by extraordinary DC effort.
The loss of Antelope and Ardent were evaluated to have not been the result of their Aluminum superstructure.
The Sheffield actually employed steel rather than aluminum in both its hull and superstructure, so aluminum construction played no part in her loss.
OPV 270 main specifications
- Overall length : 84.00 m (275.5′)
- Range : 8000 nm @ 12 kts
- Endurance : 5 weeks
- Speed : 22.0 knots
- Crew : 40 persons
- Passenger and VIP : 26 persons
- Survivors : 35 persons