Alma S.: Getting Traction

Last spring the z-drive Alma S. joined the Bisso Towboat fleet. The boat also joined its sister vessel, Cecilia B. Slatten. Now 6 years old, Cecilia B. Slatten was the first tractor tug in what has become a growing fraternity of z-drives working on the lower Mississippi River.

An increase in the inboard slant to the side bitts and bulwarks differentiates Alma S. from Cecilia. The slant allows Alma S. to tuck under a ship’s counters better. Another change is using John Deere generators to meet Tier 2 federal emission requirements.
The 100-by-38-foot, 4,300-hp Alma S. is operating from the company’s moorage at Burnside, La., on the east bank of the river approximately halfway between New Orleans and Baton Rouge.

Two azimuthing Rolls-Royce/Ulstein z-drives are powered by EMD 16-645 E6 diesels that have been modified to meet the new federal emissions requirements. The bollard pull is 60 tons.

On deck is a Markey hydraulic hawser winch with Plasma hawser line, a McElroy deck capstan and a Washington Chain quick-release tow hook.

Bisso Towboat has a third z-drive planned, for completion in late ’07 or early ’08, to be built at Main Iron Works, Houma, La.

According to Scott Slatten, Bisso’s president, the company is committed to z-drives. They have proven themselves admirably suited to the job of ship-assist work in tight spots and difficult currents, and also adept at chewing up the debris that populates the lower Mississippi River. The drives are not as vulnerable to jamming and breakage from logs and flotsam as was first thought.

Alma S. is named after Scott Slatten’s mother, Alma Slatten.

 
Top left: Capt. Ruben Dupre at the controls of the 100-foot z-drive tug.
Top right: The Markey hydraulic winch on the foredeck.
Left: Chief Engineer Michael McKarry with the Rolls-Royce/Ulstein z-drives.
Bottom left: Alma S. shows off the inward curves of its bulwark that allow it to get in closer to ships.
Bottom right: one of the two EMD 16-645 E6 diesels that generate a total of 4,300 hp.