Page 34: of Maritime Reporter Magazine (May 2004)

Propulsion Technology

Waterjets for a Difficult Design Task

The idea of a ferry going over the sea to Skye (see ferry route on map, upper portion of next page) is not a new one, though a challenge in terms of efficiency and comfort to say the least. Upon inves- tigation, it was found that a waterjet propulsion solution was the only viable option.

The idea of a ferry going over the sea to Skye is not a new one, although with the Skye bridge opening a few years ago. it is not an adventure many people undertake these days. A small car ferry operates in the south of the island, and a large car ferry takes people over from

Uig in the north west corner of Skye to the Outer Hebridian islands of Lewis and Barra. There had however, long been talk of a possible passenger service linking the North of Skye to the Scottish mainland at Gairloch. A feasibility study was carried out by the local council, after which some local businessmen pulled together to form a new company in 2003 called West Highland Seaways

Ltd.. trading as 6° West.

The requirement to make the route successful was that the journey must be

Vessel Specification

Length 48.4 ft. (14.8 m)

Beam 13.1 ft. (4 m)

Draft 2 ft. (0.6 m)

Displacement 12.5 tons

People (summer) 36 Passengers + 2 Crew

Cargo (winter) 1 on or 12 Passengers + 2 Crew

Speed 18 Knots Cruising

Engines 2 x Cummins 6BTA5.9M

Certification .. .EU Class C & MCA Workboat CoP done four times per day, in an hour and a half, requiring an average speed of 18 knots. The journey must be comfortable, but in a craft that could handle the rough sea conditions. While existing designs were offered with modifications to meet the new EU regulations on the safety of

Passenger Vessels, they tended to be rel- atively heavy displacement vessels, which required excessive power and fuel consumption to achieve the 18 knots required.

Ace Marine were approached, and responded with a new concept in boat design that was designed to be low cost, lightweight and comfortable, with reconditioned airline seats. The designer molded a relatively narrow hard chine planing hull form around six rows of seats with the intention of delivering excellent sea keeping qualities, both at speed, and at loitering speeds.

The client specified a pair of Cummins engines for redundancy. The 26-in. diameter propellers required to push the vessel at 18-20 knots meant long shafts with brackets, and exposed rudders. In order to protect the propellers and rud- ders for beaching purposes, the designer • NON-HAZARDOUS • BIODEGRADABLE • NON-CORROSIVE • SAFE

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