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Bridging troubled waters: Washington boatbuilder develops prototype bridge erection boats (BEBs) for Marine Corps.

Since its founding in 1998, Aluminum Chambered Boats (ACB) of Bellingham, Wash., has specialized in high-performance aluminum boats utilizing a proprietary sealed-chamber topside design. The chambers are designed to provide flotation, double-skin protection against damage and reserve buoyancy close to the waterline.

Over 300 hulls from 23 to 30 ft. long have been delivered to government, commercial and recreational operators. Since it had supplied craft to the U.S. military, ACB was also asked to bid on the contract to replace the U.S. Marine Corps MK II bridge erection boats (BEBs), which were built about 30 years ago.

According to Vince McLeod, ACB's director of federal government sales and operations, the specification called for what was virtually a small lightweight tug able to maneuver floating bridge sections in flowing rivers. McLeod concluded it would not fit any of the company's standard hull forms. But on closer examination, they realized that ACB's 23 ft. V-bottom hull with chambered topsides could indeed support the required power package and load capacity with only small changes. McLeod's proposal was for a hull with an 18[degrees] V below the waterline, a 22 in. draft, and a beam of 8 ft. 2 in., including the D-rubber fendering.

A prototype was constructed with hull plate of 1/4 in. aluminum and the side chambers 3/16 in. aluminum, individually sealed and pressure tested. Two push knees on the bow and a step on the stern brought the overall length to 27 ft. On deck, the proposed Mark III BEB was laid out as a workboat with the helm forward, four bollards and a hand-cranked winch on a pedestal aft. A removable base is provided for mounting a 7.62 mm machine gun on the stern deck.

A pair of Cummins 6BT210 diesel engines that each produce 210 hp at 2600 rpm are located amidships under the raised middeck. Under the stern deck are the ZF 220 marine gears with a 1.12:1 ratio, as well as the Ultrajet 305 waterjets. Control of the jets is by a hydromechanical control system. To allow operation in tropical conditions with air temperatures from -25[degrees] to 125[degrees]F and in water up to 95[degrees]E a pair of oversized recessed Duramax Marine keel coolers are fitted. The engines are. certified to the EPA's IMO-Tier 1 standard, and under new military guidelines they can run on diesel or modified jet fuel. An 80 gal. capacity fuel tank is located forward of the engine compartment.

Construction of four prototypes began in early November 2004 and was completed this spring. During the builder's trials, the new Mark III BEBs demonstrated a bollard pull of 4800 lb. forward and 2300 lb. in reverse. The MK III vessels can transport a palletized cargo of 4400 lb., or 14 marines and two crew at a top speed of 15 knots. Top speed without a load was over 28 knots. For shipping, the cabin top is removable and the mast collapsible. The hull is fitted with four lifting eyes to allow it to be transported by ship, trailer, helicopter, rail car or C-130/C-5 aircraft.

A delegation of Marines arrived in Bellingham and put the boat through an initial series of operational tests with the floating bridge units on a local lake. All four boats were then delivered to the Army's Aberdeen Test Center in Maryland for further field-testing in the deployment of the pontoon bridges, support of divers, hydrographic surveys, patrols, etc. ACB expects that the Marines will exercise options for a production run of 61 more BEBs.
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Title Annotation:marine propulsion
Author:Marsh, Peter
Publication:Diesel Progress North American Edition
Date:Nov 1, 2005
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