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Schneider, Homer J. (ed.) / The Wisconsin engineer
Volume 46, Number 4 (January 1942)

Sea otter II,   p. [12]


Page [12]


                    SEA OTTER II
Automobile Engines ... Vertical Propeller Shafts
R ECENT trials have been completed in Gulf Coast
      waters on a novel development in cargo ship design
      which is being sponsored by the Navy Department
 as at least a partial answer to the submarine threat of the
 North Atlantic. The first full size vessel of this new type
 built for experimental purposes is the 257-foot SEA
 OTTER II. Since the results of the trials will not be
 known for some time, the Navy Department has curtailed
 all but a brief announcement of the details of the vessel.
   The basic design, from which variations have been pro-
posed, has the following general characteristics:
   Length overall  . . . . . . . 257 feet 6 inches
   Length between perpendiculars   . 250 feet
   Breadth, molded    . . . . . .      40 feet
   Depth, molded   . . . . . . .       21 feet
   Load draft (exclusive of propellers)  11 feet
   Load displacement   . . . . . 2250 tons
   Deadweight capacity . . . . . 1622 tons
   Brake horsepower . . . . . . 1760
   Speed . . . . . . . . . .           12 knots
   The vessel is all welded construction using rectangular
plates which require practically no bending except at the
bilges. The hull construction uses 38" plate while the flat
keel requires l2" plate. The hull is divided by two longi-
tudinal bulkheads and transversely by eight watertight
bulkheads. Since the vessel in loaded condition is low in
the water and will be awash most of the time at sea, a
sponson has been erected at the bow to provide extra
buoyancy and better seaworthy qualities.
  A single deckhouse located aft of midships provides
living accommodations for 15 persons, and space for the
wheel house, gun platform, and signal station. One life-
boat is carried. The crew consists of the captain, three
quartermasters, two engineers, one radio man, and one
cook, making a total normal crew of eight men. The
engine room is also located aft of midships.
  Evidence of the minimum     of labor and materials
required for construction is demonstrated by the building
of the Sea Otter II in two months. Long range fuel
capacity is 182 tons which at 11 knots gives a cruising
radius of 9050 nautical miles, and at 12 knots, 7419 nau-
tical miles. Normally the vessel will carry 95 tons, pro-
viding a cruising radius of 3700 nautical miles at 12 knots.
Fresh water tanks carry 5040 gallons; fuel oil for oil
burning heater, 390 gallons; lubricating oil, 890 gallons.
The hull is equipped with a hydraulic steering gear and
an electrically driven capstan.
   The greatest innovation of this strange vessel is its pro-
 pulsion system consisting of sixteen 110-horsepower six-
 cylinder Chrysler gasoline engines of the type used in
 automobiles. Four batteries of four engines each are
 arranged to drive four propellers through vertical shafts
 extending through the bottom of the hull. The four pro-
 pellers are located transversely across the flat bottom of
 the vessel in much the same manner as outboard motors,
 except for the fact that they are suspended just aft of
 midships and not in the stern. Four engines hydraulically
 coupled to a ring gear are arranged radially around each
 shaft opening thus providing 440 horsepower to drive
 each propeller. The thrust is not excessive and is easily
 taken by vertical shaft housing in much the same manner
 as taken by outboard type motors. The two-bladed pro-
 pellers have a diameter of 70 inches and a pitch of 84
 inches. The propellers and transmission units can be
 lifted while under way for repairs, or to reduce draft
 when necessary to give a maximum draft of only 11 feet.
 Current for lighting and auxiliary purposes is generated
 by a gasoline motor driven generator. The vessel carries
 in spare one complete power transmission, two propellers,
 and four engines. It has a turning circle of 1000 feet with
 a 32 degree rudder.
 While the Sea Otter II was built at a cost of $250,000,
 it is estimated that vessels of the same size produced in
 quantity will not cost more than $100,000 each. It is
 contemplated on using a number of the Sea Otters as
 coastal vessels and trawlers, and the likelihood is that
 many will be used in Atlantic service for the duration of
 the emergency, since, with shallow draft and low free
 board, they will offer small targets for air or submarine
 attacks.
 Because of the speed of construction and availability of
 propulsion machinery, the Maritime Commission contem-
plates the construction of a number of vessels of this type
as tankers to relieve the existing oil shortage.
                                               0
                                            Cut and
                                         specifications-
                                           Courtesy of
  Marine
Engineering
and Shipping
  Review.
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In. An


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