137
April 2, 2001

High Tech Catamaran for Ventura California

"I’ve been on this hull in San Francisco, New Zealand and Fiji," says Alex Brodie of Channel Island Cruises in Ventura California, of the extensive research that went into the company’s selection of the Teknicraft catamaran design for their new build, "And what appealed to me was the hull’s combination of sea-keeping at speed."

Brodie’s company, which has a transportation concession for the Channel Islands National Park, currently operates four single-hull 49-passenger boats. The new 149-passenger 65x24-foot Cummins-powered catamaran Islander, delivered in mid March, will replace two of the smaller vessels. The new vessel features a range of environmentally friendly features such as high boxes around the fuel filler fittings to catch overspill. It also has non-toxic high polish bottom paint.

Aluminum boat builder All American Marine, of Bellingham Washington, has a partnership with Auckland, New Zealand’s naval architect Nic de Waal for the exclusive building rights to his unique Teknicraft catamaran designs on the U.S. west coast. Each of the twin Teknicraft hulls or sponsons employs a combination of symmetrical and asymmetrical shapes. The symmetrical bow-sections ensure directional stability in short swell conditions and following seas, while the asymmetrical amidships and aft sections ensures softness of ride and reduced wetted area which enhances comfort and economy. Horizontal steps on the inside of the tunnel walls act both as chines to deflect green water from the hull surface, and to break up the solid water into spray.

The vertical inside shape of the sponsons, reduces the planing area, thereby reducing the vertical acceleration forces. An additional feature in enhancing passenger and crew comfort is the action of the longitudinal chines on the inside of the tunnel walls. As solid green water is broken up into spray while being deflected from the hull, it mixes with air steaming down the opening between the sponsons. This mixture of spray and air creates a high-density medium inside the tunnel, which causes a dampening effect each time the hull moves through a trough of a wave.

The action of the longitudinal chines inside the tunnel, as well as wide chines on the outside, both deflecting water away from the hull, reduces the wetted area and therefore the resistance of the hull. The vertical inside shape of the sponsons minimized wave interference between the sponsons, which further reduces drag.

A hydrofoil system is fitted to the hull of the Islander. The lift produced by the foil-system reduces the hull resistance, which increases speed; while at the same time increases the load-bearing capability. The foil action reduces the power needed to maintain service speed. Unlike conventional hydrofoils, which lift the hull completely out of the water, these foils are designed to only partly reduce the draft, thereby reducing resistance, but still maintaining good sea-keeping by having the hull still partly submerged.

he boat is powered by a pair of emission compliant Cummins KTA19 M4 engines each delivering 700 HP @ 2100 RPM into Twin Disc MG 5114A SC marine gears with 2.5:1 ratios and turning 5-blade 36x42-inch Osborne propellers on three-inch Aquamet shafts. Brodie explains the choice of Cummins engines as a combination of factors including their proven record in the demanding crew boat environment and their ability to meet the power to weight ratio needs of this project. He also points out that his firm has repowered one of their existing single hulled boats with a Cummins engine under California’s Carl Moyer clean air environmental program. Speeds on sea trails peaked at 27 knots and provided a comfortable cruising speed of 24 knots at about 2000 RPM, "Just as predicted," said a pleased Capt. Brodie.

Hull plating is 1/4-inch 5083 aluminum below the water line with 3/16 and 5/32 above. All metal was cut in Seattle at Northwest Plasma.

For additional information on the Teknicraft contact:

Nic de Waal
Teknicraft Design Ltd.
P.O. Box 34-712
Birkenhead, Aukland, NZ
Phone: 011 649 482 3331
Fax: 011 649 482 3334
E-mail: teknicraft@xtra.co.nz

or:

Matt Mullett
All American Marine
Bellingham, WA
Phone: 360 647-7602 Fax: 360 647-7607
E-mail: matt@allamericanmarine.com

For more on the vessel’s assignment:

Alex Brodie
Channel Island Cruises, L.L.C.
1867 Spinnaker Dr.
Ventura, CA 93001
Phone: 805 642-1393

For more on the Cummins engines:

John Walls
Cummins Northwest, Inc.
811 S.W. Grady Way
Renton, WA 98057-9811
Phone: 1 800 274-0336
E-mail: jmwalls@cnw.cummins.com

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