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A Review OUTSTANDING U.S. SHALLOW DRAFT VESSELS OF 1980 The shallow-draft sector of the U.S. shipbuilding industry contin- ues its pattern of steady growth, especially in the offshore sector. Construction of utility boats, sicp- ply vessels, crexvboats, and other types to service the offshore drill- ing and production platforms, as well as tugs and towboats for use on the inland xoaterways, is pro- viding substantial and profitable work for most of the smaller yards. This article—our First Annual Review of Shallow-Draft Vessels — is a portfolio of some of the outstanding craft that have been completed by U.S. shipyards dur- ing the past year. CRABBER/TRAWLER 'BIRGIT-N' The fishing vessel Birgit-N, first crabber/trawler built by Ta- coma Boatbuilding for Bering Sea service, was delivered to Peter Njardvik and A.O. Nordheim to join their other vessels in the rigorous and highly competitive Bering Sea crab fishing. The ves- sel's design, by B.F. Jensen and Associates, incorporates several features that improve the effi- ciency of the trawler. The new boat has an overall length of 123 feet, beam of 32 feet, and depth to main deck of 16 feet. Propulsion is by a Cater- pillar D399 diesel with an output of 1,125 bhp at 1,225 rpm, provid- ing a speed of 12 knots through 4.5:1 reduction gearing. The en- gine is controlled by Mathers Con- trols equipment. Electric power is provided by three Caterpillar gen- erators—two model 3406 each of 210 kw and one model 3304 of 90 kw. The hydraulic system is by Vickers. The Birgit-N has four crab tanks with a total capacity of 8,800 cubic feet, each tank being insulated with 6 inches of closed- cell urethane foam. This four- tank arrangement allows for ease of loading crab, and also facili- tates handling of salmon when the vessel operates as a tender during the Alaskan salmon sea- son. A 60-ton York refrigeration plant is installed to maintain fish in the tanks at a temperature of 30 F in chilled seawater. Sumps located in the forward tanks and a sliding watertight door between tanks will allow rapid discharge of the frozen salmon via a fish elevator through the forward tank hatches. A major benefit of the four- tank arrangement is a shaft alley allowing access from the engine room to the steering compart- ment and lazarette below decks. The circulation pumps are located in the shaft alley, thus leaving more usable space in the engine room. All compartments below the deck are protected by water- tight doors. The efficiency of Birgit-N's de- sign is enhanced by the use of two 10-ton cranes both supplied by Northern Line Machine, a di- vision of Tacoma Boat. The for- ward crane has a reach of 36 feet, and will serve as the picking boom. The aft crane is a unique level-luffing design with a reach of 48 feet. The level-luffing fea- ture of this crane allows the op- erator to raise and extend the boom without the need to con- stantly pay out or haul in line. No matter how the boom is ma- nipulated, the line length remains fixed. This arrangement is said to be safer, faster, and more pre- cise than existing installations. Both cranes are controlled by hy- draulic servos on the main con- trol valves that are located in the engine room. The boat is also equipped with a pair of trawl winches, a stern ramp, and a Northern Line net reel to allow the Birgit-N to trawl for bait fish. Birgit-N 14 Maritime Reporter/Engineering News
