USCGC Barbara Mabrity (WLM-559) is a Keeper-class coastal buoy tender of the United States Coast Guard. Launched in 1999, she is home-ported in Mobile, Alabama. Her primary mission is maintaining aids to navigation from western Florida to the Mississippi River. Secondary missions include marine environmental protection, search and rescue, and security. She is assigned to the Eighth Coast Guard District.
Construction and characteristics
On 22 June 1993 the Coast Guard awarded the contract for the Keeper-class vessels to Marinette Marine Corporation in the form of a firm contract for the lead ship and options for thirteen more. The Coast Guard exercised options for the fifth through tenth ships, including Barbara Mabrity, in February of 1997. The ship was launched on 26 March 1999 into the Menominee River. Barbara Mabrity is the ninth of the fourteen Keeper-class ships built.
Her hull was built of welded steel plates. She is long, with a beam of , and a full-load draft of . Barbara Mabrity displaces 850 long tons fully loaded. Her gross register tonnage is 904, and her net register tonnage is 271. The top of the mast is above the waterline.
Rather than building the ship from the keel up as a single unit, Marinette Marine used a modular fabrication approach. Eight large modules, or "hull blocks" were built separately and then welded together.
The ship has two Caterpillar 3508 DITA (direct-injection, turbocharged, aftercooled) 8-cylinder Diesel engines which produce 1000 horsepower each. These drive two Ulstein Z-drives. Keeper-class ships were the first Coast Guard cutters equipped with Z-drives, which markedly improved their maneuverability. The Z-drives have four-bladed propellers which are in diameter and are equipped with Kort nozzles. They can be operated in "tiller mode" where the Z-drives turn in the same direction to steer the ship, or in "Z-conn mode" where the two Z-drives can turn in different directions to achieve specific maneuvering objectives. An implication of the Z-drives is that there is no reverse gear or rudder aboard Barbara Mabrity. To back the ship, the Z-drives are turned 180 degrees which drives the ship stern-first even though the propellers are spinning in the same direction as they do when the ship is moving forward. Her maximum speed is 12 knots. Her tanks can hold 16,385 gallons of diesel fuel which gives her an unrefueled range of 2,000 nautical miles at 10 knots.
She has a 500 horsepower bow thruster. The Z-drives and bow thruster can be linked in a Dynamic Positioning System. This gives Barbara Mabrity the ability to hold position in the water even in heavy currents, winds, and swells. This advanced capability is useful in bringing buoys aboard that can weigh more than 16,000 lbs.
Electrical power aboard is provided by three Caterpillar 3406 DITA generators which produce 285 Kw each. She also has a 210 kW emergency generator, which is a Caterpillar 3406 DIT.
The buoy deck has of working area. A crane with a boom long lifts buoys and their mooring anchors onto the deck. The crane can lift up to .
The ships' fresh water tanks can hold 7,339 gallons. She has three ballast tanks that can be filled to maintain her trim, and tanks for oily waste water, sewage, gray water, new lubrication oil, and waste oil.
Accommodations were designed for mixed gender crews from the start. Crew size and composition has varied over the years. When she was launched, her complement was 18, commanded by a chief warrant officer. She currently has a crew of 24.
Barbara Mabrity, as all Keeper-class ships, has a strengthened "ice belt" along the waterline so that she can work on aids to navigation in ice-infested waters. Not only is the hull plating in the ice belt thicker than the rest of the hull, but framing members are closer together in areas that experience greater loads when working in ice. Higher grades of steel were used for hull plating in the ice belt to prevent cracking in cold temperatures. Her bow is sloped so that rather than smashing into ice, she rides up over it to break it with the weight of the ship. Barbara Mabrity is capable of breaking flat, 9-inch thick ice at 3 knots.
The ship carries a cutter boat on davits. She was originally equipped with a CB-M boat which was replaced in the mid-2010s with a CB-ATON-M boat. This was built by Metal Shark Aluminum Boats and was estimated to cost $210,000. The boat is long and are equipped with a Mercury Marine inboard/outboard diesel engine.