M/T PORTLAND Unusual 360° Steerable Z-Drive Tug Enters Service
Shaver Transportation Company has recently taken delivery of a new ship handling tug, the Portland, for service in the Port of Portland. The Portland is propelled by two Maritime Industries model 1650 H 360° steerable Z-drives, each rated at 1,700 bhp.
The Maritime propulsion units are believed to be the largest currently installed in North America for tug application.
Shaver Transportation Company made the decision to build a tug with 360° thrust capability to take advantage of the vastly superior maneuvering characteristics that this type of propulsion offers—particularly for ship handling tugs. The accompanying polar thrust diagrams (Fig. 1) illustrate the superiority of the Z-drive tug over a conventional tug with nozzles and flanking rudders. As can be seen, the improvement in lateral and astern thrust, over the conventional tug, is impressive.
An important factor in making this decision was the ability to change thrust direction rapidly.
A typical case where this would be required is when a tug wishes to switch from the pulling to the pushing mode (see Fig. 2). A tug with 360° propulsion can achieve this in a fraction of the time required by a conventional tug.
A decision had to be made as to where the propulsion units should be located in the vessel.
Japanese practice has favored positioning them at the stern, in a location similar to that of conventional propellers, with the tow point forward of the propulsion units. The European practice has generally been to position the units well forward, in what has become known as the "tractor" configuration. This has the advantage that the tow point is aft of the propulsion units, making the vessel, in the pulling condition, very stable and safe from girding (girting).To reduce draft, it was decided to use the reverse "tractor" concept—a joint development of Maritime and Shaver.
As can be seen from the drawings of the vessel, the propulsion units are located aft, although slightly forward of the position normal chosen for Z-drives. The Z-drives M / T Portland Maritime Industries' Z-drive propulsion units.
are located above the bottom of the hull skeg, thus protecting them from grounding damage and minimizing the vessel's draft. The tug tows off the bow and therefore has the same inherent antigirding and anti-stemming characteristics as the normal tractor tug.
From the foregoing, it is apparent that the "reverse tractor" tug, as its name implies, will spend much of its time running astern. The hull has therefore been specially designed for astern operation, to optimize the water flow through the propulsion units and minimize wash impingement on the hull.
The Z-drives are controlled by a Maritime Industries single lever system. Thrust direction, engine speed and clutch are all controlled by a single joystick. There is one joystick for each propulsion unit, since it was preferred to retain full operator control of the exact position and rotational direction of each Z-drive. The alternative would have been a combined control, with the position and rotational direction of both Z-drives under the control of a microprocessor. Such removal of intimate control from the helmsman was considered undesirable for tug operation.
The propulsion units incorporate a number of design features to enable them to survive encounters with logging debris — a not uncommon hazard in the Pacific Northwest. Most important of these is the shock absorbing steering system—a unique Maritime development, evolved over years of Z-drive operating experience in the log-strewn waters of British Columbia.
The Portland was designed by James A. Towers and Donald R.
Hudson and was built by Nichols Brothers Boat Builders of Freeland, Wash. The principal particulars are as follows: length overall, 107 feet 7 inches (32.8 meters) ; length between perpendiculars, 100 feet (30.49 meters) ; beam (molded), 32 feet 6 inches (9.91 meters) ; beam (overall) 34 feet 2 inches (10.42 meters) ; depth (molded) 15 feet 3/4 inches (4.59 meters) ; draft, 13 feet (3.96 meters) ; p r o p e l l e r speed, 300 rpm; and propeller diameter, 86 inches (2.18 meters).
Her main propulsion power is provided by two Fairbanks Morse 38D81/8 diesel engines. Line handling is by means of twin Markey capstans.
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Content
- Secretary Lewis Announces Plan To Transfer MarAd To DOT page: 4
- Work On Two Tankers At Northwest Marine Will Total Over $7.8 Million page: 5
- $2.3 Million Awarded To SeaTec For Mooring And Pipeline Project page: 5
- Cat Introduces New Family Of High-Speed Diesels- Product Bulletin Available page: 6
- Bay Building Barge With First Conveyor To Handle Wet Phosphate Rock page: 6
- NICOR Acquires Arthur Levy Enterprises And Offshore Island Boats page: 7
- New Licensee In Japan For B&W Diesel Engines page: 7
- Robert Ware Establishes His Own Maritime Public Relations Service page: 7
- Circular Detailing New Suez Canal Regulations Available From Candia page: 7
- IMODCO Receives Order From Petrobras For $5-Million SPM Terminal page: 7
- TIW Industries And DMI Sign Agreement To Build Dredges In Canada page: 8
- Wartsila Turku Shipyards Delivers Superferry 'Silvia Regina' page: 8
- U.S. Combat Systems In Foreign Built Ships Topic At ASNE Meeting page: 8
- Todd Continues Expansion —$12-Million Drydock Ordered From Bender page: 9
- Gems Paddle Switches Monitor Flow Conditions —Literature Available page: 9
- Eller & Company Acquires Uiterwyk Cold Storage page: 9
- Puget Sound Tug & Barge Will Build 12 Barges Costing $39.5 Million page: 9
- Seaco Energy/Coastal Carriers Joint Venture Plans Floating Terminals page: 9
- Conversion Of RO/RO 'Ponce' Completed By Sun Ship page: 10
- New Torque Controller Introduced By Delaval —Literature Available page: 10
- First Of New Destroyer Class Commissioned At Ingalls Yard page: 10
- Santa Fe Diving Services Awarded Contract To Provide RCV And Crew page: 10
- National Steel Lays Keel For U.S. Navy Cable Repair Vessel page: 10
- Major Work On 'Wavertree' Performed By Bethlehem Yard page: 11
- Marathon Introduces New Super 300 Jackup For Harsh Environments page: 12
- Paper On Real Time Monitoring Presented At Pacific Northwest SNAME page: 12
- Second Crandali Dock At National Sea Products Yard Rebuilt And Enlarged page: 12
- Dravo Acquires The Ryan-Walsh Group page: 13
- Union Oil Products Carrier Launched At NASSCO Yard page: 14
- Anthony McAllister Jr. Elected Chairman Of New York Towboat Association page: 14
- $172-Million Navy Order To Bell For New Type Landing Craft page: 14
- Theriot-Modec To Build Ammonia Barge For Energy Transportation Subsidiary page: 15
- Edward Campbell Named To Board Of Trustees At Webb Institute page: 15
- M/T PORTLAND Unusual 360° Steerable Z-Drive Tug Enters Service page: 16
- $140-Million Contract For Two Offshore Rigs Awarded To Gotaverken Arendal Shipyard page: 16
- Benson, Basse And David Join Tampa Barge In Management & Production page: 16
- Delaware Valley ASNE Chapter Discusses Government Contracting page: 16
- New NKK Ship Design Will Reduce Fuel Use By Some 40 Percent page: 17
- Los Angeles SNAME Discussed Single-Point Mooring Technology page: 18
- Hudson Delivers The 'Gulf Dolphin7 To Gulf Fleet Marine page: 18
- Third Seaboard RO/RO Ordered At Fredriksstad Yard Will Have MacGregor Hoistable Decks page: 18
- Cummins Powers First Towboat Built By Brice Shipbuilding page: 19
- Brochure On Motorship Protection Program Offered By Drew Ameroid Marine page: 20
- Bethlehem Steel Names Messenger Assistant To Mgr-Ship Repair Sales page: 20
- Grumman Hydrofoil For Israel Launched At Lantana Boatyard page: 20
- Dravo-Built Towboats For China Get A Lift From Dock Express page: 20
- Report Available Comparing Qualities Of Synthetic Ropes page: 21
- Petronio Elected VP-Engineering At Pool Company Of Houston page: 21
- Two MARCO Oil Skimmers Delivered To Mexican Navy page: 21
- SHIPBOARD AUTOMATION & MONITORING SYSTEMS page: 22
- David Taylor Naval R&D Center Hosts Hydromechanics Meeting page: 22
- W.B. Buhrmann Elected President Of Newly Formed U.S. Steel Companies page: 24
- Valley Line Asks Title XI For $90.1-Million Barge And Towboat Project page: 24
- Petro Marine Services To Build $25-Million Shipyard In Alaska page: 26
- Riverway Completes Second Drydock For Its Own Repair Division page: 27
- New Brochure Describes National Crane's Line Of Marine Lifting Systems page: 27
- Shipyard Conference Honors Past Chairmen McKay And Pirozzolo page: 28
- HUDSHIP To Build Four Big Towing/Supply Vessels For Zapata page: 29
- U.S. And Canada Agree To Cooperate In Marine Transportation R &D page: 34
- Philadelphia Resins' New Brochure Describes The Company And Its Products page: 34
- Griffin & Alexander Jackup Rig Commissioned At Bethlehem-Beaumont page: 35
- Lima Electric Announces New Model Alternator- Literature Available page: 35
- Port Handbook Makes Museum Donations page: 36
- Great Lakes/Great Rivers SNAME Spring Meeting Held In Cleveland page: 36
- Raytheon Opens New Marine Sales And Service Facility In Mississippi page: 36
- Partnership Between AMCA International & McDermott Formally In Business page: 36
- Gulf Fleet Marine Names Vaccaro Contracts Manager page: 37
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- McAllister Reports Ship Financing Policy Now Under Government Study page: 39
- Largest DMI Dredge Delivered To Mexican Owner page: 39
- 34th Annual Statistical Analysis Released By Marine Index Bureau page: 40
- Underway Replenishment Machinery Topic At Long Beach/LA ASNE page: 40
- Rubber Fendering Reduces Damage To Vessels And Piers page: 40
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- Mario Moor Will Head Sulzer's New Subsidiary Company In Hong Kong page: 41
- Revised Rules On Mobile Offshore Rigs Issued By Det norske Veritas page: 41
- APL Ready To Build 45-Foot Production Unit Containers page: 41
- U.S. Maritime Industry's Safety Excellence Cited At Award Ceremony page: 42
- Tracor Marine Awarded $2.5-Million Navy Contract To Manage OCEI Facilities page: 42
- Ned Smith Named Vice President-Finance For American Steamship page: 42
- Dravo To Provide People's Republic With Technical Assistance And Equipment page: 42
- IHI's New Shaft Generator System Meets Its Design Expectations page: 43
- McDermott Incorporated Promotes Four To « Vice President Posts page: 43
- Twin City Yard Lays Keel For Seagoing Split-Hull Dredge page: 44
- First Large-Scale Floating Seawater Desalination Plant Launched At Nordseewerke page: 44
- Multipurpose Cargo Vessel Launched At GHH Sterkrade Yard page: 44
- Cat-Powered Research Vessel Delivered By A t l a n t i c Marine page: 47
- Last Of Ten Supply Vessels For NMS Launched By Promet page: 47
- NASSCO-Built Destroyer Tender Delivered To Navy page: 50
- Dome Petroleum Orders Drill From Cammed Laird Yard page: 51
- ACBL Towboat 'W.T. Toutant' Launched At Jeffboat Shipyard page: 52
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- C.E. Matthews Appointed N a t i o n a l Sales Manager For Morse Controls page: 53
- Skagit Crane Provides Improved Fuel Economy —Literature A v a i l a b le page: 53
- New York Maritime Day Ceremonies Featured Presentation Of Two Awards page: 58
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- Bulk Carrier 'Star Of Texas7 Launched At Levingston Yard page: 59
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