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McAllister, whose steering goes back to steam, "and they let me handle the boat, and I said this is fantastic."

It was an impressive thought: a single- screw tugboat that could go in any direc- tion. He bought two Z-drives, 3,000 hp each.

Capt. McAllister describes a number of drive systems that could be alternatives to

Z-drives, including flanking rudders, of which McAllister was an early adopter in the Northeast. They proved their mettle, in Capt. McAllister's judgment, control- ling "acres of barges" on western rivers with sharp bends, and stand today in ship docking as "tried and proven" for their ability to provide equal directional power forward and astern.

But some propulsion systems move you sideways too, at full power or nearly so.

Capt. McAllister describes Voith-Schnei- der drives as the most maneuverable, but providing less bollard pull per HP, and a higher initial cost than the Z-drive. Z-dri- ves are not without trade-offs of their own, including a reduction of power through two pairs of bevels and three shafts. "For coastal towing, the Z-drive can't compete with the efficiency of large- diameter, slow-turning propellers." But for shipdocking tugs, there's no question- ing their effect. "Z-drives are the rage," says Capt. McAllister, and they're what a ship docking operation is expected to have. McAllister fulfills expectation — at present has nineteen Z-drive ship docking tugs. About half are YTB conversions.

The upgrade to Z-drive involves a lot more than just re-engining. The whole propulsion system is restructured, requir- ing a rebuilt stern. Marine architect Don- ald Hankin designed a Z-drive stern for the Kaleen and the Donal, which were converted in McAllister's yard at

Mariner's Harbor. It was the same yard from which the updated Navy tugs would leave at dawn, to dock Navy ships in 2006. 22 • MarineNews • July, 2006

The McAllister skippers wore uniforms too, or at least dress shirts for the occassion. Here, Capt. Gus

Rankin on the Stacy McAllister keeps an eye on things. (Photo: Don Sutherland)

The single-screw J.P. McAllister, up from Balto, is one of four tugs keeping the Kearsarge against its dock. Nearby observers were surprised by the force they exerted. (Photo: Don Sutherland.)

Pilot Jeff McAllister returns to the Stacy McAllister after guiding the destroyer Ramage out of the North

River dock for her next destination. (Photo: Don Sutherland)

The McAllister Responder, ex-Empire State, conducts the Amphibious Transport Dock U.S.S. Shreveport (LPD 12) up the Hudson, to be turned for docking back at Stapleton. (Photo: Don Sutherland)

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