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T

Tabling. The broad hem worked along the borders of a sail, awning or other canvas work.

Tack, to tack. So to change the course of a sailing vessel by coming about as to take the wind from over the opposite bow to that over which the wind previously came. When the wind is coming over the port bow the vessel is said to be on the port tack, and when it comes over the starboard bow she is on the starboard tack.

Tackle. Any combination of ropes and blocks that multiplies power. A single whip usually called a tackle though erroneously so classed, gives no increase of power but simply a change in direction of the power applied.

Tackles, Relieving. A term applied to a pair of tackles, generally stowed in the vicinity of the rudder quadrant or spare tiller. The tackle usually consists of a fixed double or multiple block with a hook or shackle for attachment to the structure and a movable block for attachment to the tiller.

Tactical Diameter. The horizontal distance from the original course to the position where the ship has turned through 16 points of the compass.

Taff Rail. A term applied to the rail around the top of the bulwark or rail stanchions on the after end of the weather deck, be it upper, main, raised, quarter or Poop.

Tail or Guide Rod. An extended portion of rod working in a bearing as a guide for parts in motion.

Tail Plate. See Horseshoe Plate.

Tail Shaft. See Propeller Shaft.

Tallow, Launching. See Launching Tallow.

Tank, Ballast. A space or compartment which may be filled with water to add weight when it is necessary to produce a change in trim or in the stability of the ship.

Tank Foundation. A term applied to the seating supporting a tank and given the name of the tank which it supports, as Oil Filter Tank Foundation.

Tank, Peak. All classification societies require that transverse bulkheads be built near each end of a ship to prevent water from flowing into the larger compartments should the ends of the ship become damaged. The observation of this rule leaves narrow "V" shaped compartments in which no cargo is stored, but they may be filled with water to alter the longitudinal inclination of the ship.

Tank, Sanitary. A tank arranged to receive the discharge from the various sanitary or plumbing fixtures located below or close to the water line and which cannot drain overboard by gravity. Contents of sanitary tanks are pumped overboard.

Tank Testers. Men from the calking and chipping gangs who test tanks or compartments for leaks and who perform such work as the tests indicate to be necessary in order to insure water or oil tightness.

Tank Top Plating. See Plating, Tank Top.

Tank Trimming. A space or compartment at the end of a ship which is filled with water in order to produce an alteration in the longitudinal inclination of the ship.

Tank Vessel. A vessel designed for the carriage of oil in bulk and fitted with especially constructed tanks for this purpose. The term is applied to both sail and power driven ships.

Tanks. Compartments for liquids or gases. They may be formed by the ship’s structure as double bottom tanks, peak tanks, deep tanks, etc., or may be independent of ship’s structure and installed on special supports.

Tanks, Gunwale or Topside. Compartments near the gunwale, or the top of the sides of the ship, used as water ballast tanks.

Tanks, Settling. See Settling Tanks.

Tanks, Wing. See Wing Tanks.

Tapered Liners. See Liners, Tapered.

Tapered Rope. See Rope, Tapered.

Tar, Hard Wood. A tar obtained from the destructive distillation of a hard wood.

Tar, Pine, Kiln and Retort. A dark, oily liquid obtained by slowly burning resinous pine wood in a kiln or by its destructive distillation in a retort. It is used as a paint and a preservative for cordage, etc.

Tarpaulin. A term applied to a pliable canvas hatch cover. One or more tarpaulins are stretched over the wooden hatch covers and the edges are held in place by battens wedged into cleats on the hatch coaming. Also applied to pieces of canvas used as a shelter for workmen or as a cover for deck equipment.

Taximeter. An early 20^th century navigational instrument for taking bearings.

Taut. The condition of a rope wire or chain when under sufficient tension to cause it to assume a straight line, or to prevent sagging to any appreciable amount.

Tee Bar. A rolled shape, generally of mild steel, having a cross section shaped like the letter T. In ship work it is used for bulkhead stiffeners, bracket and floor clips, etc. The size is denoted by dimensions of cross section and weight per running foot.

Tee, Branch. A tee with side or branch outlets.

Tee, Bull Head. A term applied to a tee in which the outlet is larger than the entrance.

Telegraph. An apparatus, either mechanical or electrical, for transmitting orders from a ship’s bridge to the engine room, steering gear room, or elsewhere, or between fire rooms, and from engine room to fire rooms. The transmitting apparatus, operated by the sender, is termed the transmitter, and the receiving apparatus, the indicator. A gong is usually fitted in order to call attention to the movement of the indicator.

Telemotor. A device for operating the valves of the steering engine from the pilot house either by fluid pressure or by electricity. When fluid pressure is utilized, two leads of pipe are necessary so that the fluid may move aft in one pipe and forward in the other, or vice-versa. The movement is provided for by a small pump or ram actuated by the steering wheel.

Telemotor, Electric. The function of a telemotor, either electric or other, is to control from the pilot house, the movement of the valve of the steam steering engine which turns the rudder. On small boats where the distance from the wheel house to the steam steering engine is short, satisfactory results have been obtained by the use of wire rope or shafting and gears to control the engine valve. On large boats the mechanical defaulters are multiplied and the physical exertion required, considerable and objectionable.

Telephone, Intercommunicating. See Intercommunicating Telephone.

Telephone, Loud Speaking. The performance of the loud speaking telephone on battleships and merchant vessels in the past three years has shown it to be the quickest, safest and most reliable means of communication yet developed for use on ships. The loud speaking telephone transmits a message so loudly and clearly that it can be heard at a distance from the instrument without the use of an ear receiver. The person talking merely brings his lips to within a few inches of an opening in the housing containing the transmitter and the receiver and touches a key. This housing is made of heavy, non-corrosive metal and is waterproof. It need not be opened and the instrument is always ready for instant service. At the same time the sensitive parts of the instrument are protected from accidental injury and from the damp sea air which quickly ruins the ordinary telephone. The loud speaking telephone does not pick up ship noises and is always heard distinctly – even in the noisiest engine room. It does not destroy the watertight integrity of the bulkheads as does the voice tube. It is more convenient, more sanitary, and far more efficient than either the voice tube or the ordinary marine telephone.

Telescope. An optical instrument intended for the use of one eye only and designed to enlarge and clarify the images of distance objects. It consists essentially of a tube having a large converging lens that forms the optical image of the object observed and a small lens or combination of lenses which magnify the image.

Tell Tale. An indicating device employed on automatic machinery or in a specific operation which gives audible or visual indication, or both, as to the exact time a specific function is begun or completed.

Telltale, Rudder. A term applied to an instrument that indicates the angle of the rudder with the center line of the ship. It is generally fitted in front of the steering wheel.

Tempering Furnace. See Furnace, Hardening or Tempering and Furnace, Tempering Pot.

Template. A mold or pattern made to the exact size of a piece of work that is to be laid out or formed and on which such information as the position of rivet holes, size of laps, etc., is indicated. The most common types of template used in ship work are made out of paper or thin boards.

Template, Pattern. A wood frame, a paper or card board outline of a part of a ship showing the shape of the part, location of holes, and giving by means of notes made thereupon dimensions and information as to the fabrication of the part.

Templates, Transferring. Patterns made from the mold loft lines or from some part of the ship by means of which an outline and form of a part is retained and conveyed to wherever needed.

Temporary Bulkhead. See Bulkhead, Temporary.

Tender. A small boat, usually power driven, used for purposes of general utility by the personnel of a large vessel. A vessel of moderate size fitted with repair facilities, reserve stores of provisions, fuel, water, etc., for the use of a number of smaller naval vessels, such as destroyers or submarines.

Tenoning Machine. A power operated machine which usually has a hand feed and cuts a tenon on pieces of timber by means of knives carried in short revolving cutter heads.

Tensile Strength. The measure of a material’s ability to withstand a tensile or pulling stress without rupture. Tensile strength of a material is usually measured in pounds or tons per square inch of cross section.

Theodolite. An instrument which, superseding the circumferentor and graphometer, is used for general surveying purposes and by naval hydrograghers.

Test Head. The bead of water corresponding to the pressure prescribed as a test for bulkheads, tanks, compartments, etc. Test heads are prescribed to insure satisfactory water or oil tightness and also as tests of strength.

Thermometer. An instrument for measuring the degree of heat or temperature.

Thermotank. A box or tank containing steam coils through which air for ventilation is heated in passing.

Thimble. An iron ring, oval or heart shaped fitting whose outer surface is concave in order that it may be held in place when worked into the corner of a sail as a cringle or in the bight of a rope. It serves as a lining to prevent the chafe of a hook, shackle, pin, etc.

Tholes; Thole Pins. A term applied to the pins of wood or metal that are fitted snugly into holes in the gunwale of a pulling boat for the purpose of forming a rowlock for the oars.

Thread. The spiral part of a screw.

Thread, Common. A standard machine thread as distinguished from a pipe thread.

Threading Machine. A machine used for cutting screw threads. This would apply to a lathe, bolt cutter, pipe threading machine, etc.

Three-Ply Riveting. See Riveting, Three-Ply.

Throat. A term applied to that part of a boom or a gaff lying immediately behind the jaw.

Throat Sheet, Boiler. See Boiler, Throat Sheet.

Throttle Valve. See Valve, Throttle.

Throttle Valve Lever. A lever used to operate the throttle valve.

Through Fastening. See Fastening Through.

Thrums. Short pieces of rope yarns used in making mats, being sewed by their bights to the canvas or cloth. Thrums are made by cutting old and worn out gear into lengths and unlaying the strands.

Thrust. The net reaction of a propeller or wheel tending to force the vessel through the water. For a model propeller the thrust is generally measured in pounds, but for full sized vessels it is oftentimes reduced to pounds per ton of displacement.

Thrust Bearing. A bearing designed primarily to take the propeller thrust from the shaft and transfer it to the structure of the ship. It is constructed with a series of rings and channels for the reception of the collars of the thrust shaft. The rear faces of the thrust bearing rings and the forward faces of the thrust shaft rings bear on one another when the screw is turning ahead. The opposite takes place in backing. The faces of the bearing channels are usually of white metal so as to provide steel on white metal wearing surfaces. At the forward and after ends of the thrust bearing casing spring bearings of the usual type are fitted to carry the weight of the thrust shaft. Special methods of lubricating and cooling are provided.

Thrust Block. Thrust Stools are to be of ample size and strength in proportion to the power transmitted to the thrust bearing; they are to extend well beyond the thrust block and are to be stiffened and supported by extra intercostals, double reverse angles, etc. All shaft stools are to be of ample strength and stiffness, in proportion to the weight of shaft and height of stool.

Thrust Block Foundation. A term applied to the seating to which the thrust block is attached. As the whole push or pull exerted on the ship by the propeller is taken through the thrust block it is necessary to construct a strong foundation that will distribute the pressure to the hull of the ship without undue local strain. This foundation should be built as high up to the center line of the shaft as possible to decrease the overturning moment on the bolts holding the thrust block in place.

Thrust Horsepower. See Propeller Thrust.

Thrust, Propeller. See Propeller Thrust.

Thrust Recess. A small compartment off the main engine room designed to contain and give access to the thrust shaft and block.

Thrust Shaft. That length of shafting which is fitted for the purpose of transferring the thrust of the propeller to the thrust bearing. This is effected by means of circular collars or rings worked on the thrust shaft.

Thwarts. Boards extending across a row boat just below the gunwale to stiffen the boat and to provide seats.

’Thwartship Bunker. A bunker having its largest dimension in a transverse direction. It is frequently a fore hold compartment located immediately forward of the boiler spaces. Such a bunker is sometimes used as a reserve bunker or it may be used for cargo.

Tides. The alternate rise and fall, averaging twice in 24 hours and 51 minutes, of the level of the ocean and the accompanying inflow and outflow of rivers, bays, channels, etc. Corresponding high and low tides, therefore, occur 51 minutes later each day. The cause of tides is the combined result of the mutual attraction of the earth, moon and sun for each other. When the sun and moon are in conjunction or in opposition, that is, both on the same side or on opposite sides of the earth, their tide producing effects conspire to produce the SPRING TIDES. These occur at the time of and for two or three days after the full and new moon. When the moon and sun form a right angle or the moon is in quadrature, the crest of the solar tide occurs in the trough of the lunar tide or vice-versa, and the NEAP TIDES result. These occur after the first and third quarter of the moon. The semi-diurnal variations of the tide are HIGH TIDE, when the tide ceases to rise and before it begins to recede; EBB TIDE, the falling tide; LOW TIDE, when the tide ceases falling and before it begins to rise; FLOOD TIDE, the rising tide.

Tie Plates. A term applied to long narrow plates used for the purpose of tying deck beams together where there is no steel deck plating.

Tiller. A heavy bar or lever having one end bored to fit on the rudder stock and having the other end fitted for connection to steering leads or relieving tackle. The function of the tiller is to turn the rudder, but as on most ships this is accomplished by a steering engine through a quadrant or yoke, the tiller is only a spare fitting to be used with the relieving tackles when there is a breakdown in the steering engine.

Tiller Rope. See Rope, Tiller.

Timber, Horn. The center line frame in the stern of a wooden ship, extending aft from the stern post.

Timber Sizer. A machine used for the conversion of logs into timber. Usually a huge band saw mounted alongside a heavy track along which a carriage is designed to travel.

Timbers, Counter. The inclined frames projecting aft from the wing transom and forming the counter. (Wooden ship.)

Timbers, Ship’s. A general term referring to the individual sticks or members of which a wood vessel’s frame work is composed.

Timbers, Stern. The aft upper stern frames in a wooden ship corresponding to the cant frames in a steel ship.

Timenoguy. A rope stretched between two points to prevent gear from fouling or chafing.

Tin Knocker. A workman who fabricates articles from thin sheet metal.

Tip Clearance. The clearance or distance between the circumference of the tip circle of a propeller and the hull of the vessel.

To Overhaul a Tackle. To separate the blocks of a tackle thus giving a greater drift to the moving blocks.

Toggle Pin. A pin, usually having an eye worked on the head. and having a point so constructed, that a portion of it may turn on a pivot pin, forming a tee shaped locking device to keep the pin in place.

Tomahawk. A riveting hammer with a long heavy head used in driving large rivets.

Tongue and Groove. A term applied to a plank one of the edges of which is cut away to form a tongue and the other recessed to form a groove. The tongue on one plank is matched with the groove on the other.

Tongue and Groove Deck. See Deck, Toungue and Groove.

Tonnage Deck. See Deck, Tonnage.

Tonnage, Gross. The entire internal cubic capacity of a vessel expressed in tons of one hundred cubic feet each.

Tonnage, Gross Registered. The gross tonnage as entered on the register or other official certificate of the tonnage of the vessel.

Tonnage, Net. The internal cubic capacity of a vessel which remains after the capacities of certain specified spaces have been deducted from the gross tonnage. These deductible spaces include principally crew’s quarters, working spaces and machinery compartments.

Tonnage, Net Registered. The net tonnage as entered on the register or other official certificate of the tonnage of a vessel.

Tons Per Inch of Immersion. The number of tons of additional weight required to immerse a vessel one additional inch of draft. The approximate tons per inch of immersion at any draft for salt water is equal to the area of the waterplane in square feet divided by 420.

Tool Grinders. Men who shape and sharpen the cutting tools for the several machines by grinding.

Tool Re-manufactured. Tools which have been reconditioned. They are sometimes reground to a smaller size and again they are restored to their original size.

Tool Steel See Steel, Tool.

Tools, Calking. Hand operated tools used in calking either wood or metal.

Tools, Pneumatic Calking. Tools used for metal calking in which the power is supplied by compressed air.

Top Timbers. A term applied to upper portions of frames in wood ships.

Topgallant Mast. See Mast, Topgallant.

Topmast. See Mast, Top.

Topmast, Fidded. A term applied to a topmast that laps over the upper portion of the lower mast. This form of topmast is supported at its lower end by a bar, called a fid, which passes through a slot in the topmast and also a slot in a pair of brackets which are attached to the lower mast. A band is worked around both masts at the level of the top of the lower mast. Withdrawal of the fid allows the topmast to be lowered.

Topmast Stay. Stay secured to the topmast near the upper end, set up with turnbuckles located near the stem on deck. Sometimes both forestay and topmast stay are secured to the same pad on deck near the stem.

Topping Lift. A rope or chain extending from the head of a boom or gaff to a mast or to the vessel’s structure for the purpose of supporting the weight and permitting the boom or gaff end to be raised or lowered.

Topping Lift Tackle. Tackle between the boom and masthead used for lowering and raising a boom.

Topside. That portion of the side of the hull which is above the designed waterline.

Topside Planking. The outside planking on a wooden ship which is above the waterline.

Topside Strake. See Strake, Topside.

Torpedo. A steel plug, sometimes of spherical shape, designed for use in expanding a lead lining tube against its outer jacket of steel or iron pipe. To accomplish this the torpedo is forced through the lead tubing from end to end.

Torpedo Boat. A type of war vessel now practically obsolete. Its principal characteristics are high speed, light construction, small displacement, and a main battery of torpedo tubes. The type was intended for use in the attacking of capital ships by means of the torpedo. The advent of the destroyers together with the increasing demands for greater seaworthiness and personal comfort has ended the building of vessels of this type.

Torque. The moment of a system of forces that causes rotation.

Tow Rope. See Rope, Tow.

Tow Rope Resistance. See Resistance, Tow Rope.

Towboat. See Tug.

Towing Machine. A machine that automatically, according to the strain on the rope, reels in or out a towing hawser. They act as shock absorbers preventing sudden tension and danger of parting. Their drums are designed to reel up and stow the hawser.

Towing Winch. See Towing Machine.

Trailing Lines. Light lines fastened to the handles of oars and secured to the boat inboard. They are used for trailing the oars alongside when the crew is not pulling.

Transfer Pump. See Pump, Transfer.

Transformer, Electric. A stationary electric machine consisting of primary and secondary coils, insulated from each other, wound, on a laminated iron core. They are usually designed to transform a high voltage to a low one or conversely to transform a low voltage to a high one.

Transom Beam. See Beam, Transom.

Transom Floor. See Floor, Transom.

Transom Frame. See Frame, Transom.

Transom, Wing. An athwartship timber attached to the top of the stern post. (Wood ship)

Transoms, Filling. Athwartship timbers attached to the forward side of a stern post.

Transport. A vessel intended for the carriage of troops, equipment, ordnance, military or naval stores, etc. The carriage aboard ship of passengers or merchandise.

Transverse. At right angles to the ship’s fore and after center line.

Transverse Bulkhead. See Bulkhead, Transverse.

Transverse Frames. See Frame, Transverse.

Transverse Number or Numeral. A key number used by classification societies in their rules for determining the scantlings of the frames and transverse members. These numbers with the corresponding scantlings are tabulated in the rules and are the results of experience and comparison.

Transverse Stability. The tendency of a ship to return to the upright position when inclined transversely by an impressed force.

Transverse Stresses. Stresses acting at right angles to the center line of a vessel or, if referring to a beam or girder, acting at right angles to the length.

Transverse Subdivision. The subdivision of a ship resulting from the fitting of transverse or athwartship bulkheads.

Trap, Steam. See Steam Trap.

Traverse Board. A device for keeping a record of the course steered and distance covered by a ship.

Trawler. A vessel designed for fishing and fitted for handling sweeping nets. Vessels of this type are of robust construction, have considerable sheer, great draft aft, good maneuvering qualities and large fish holds.

Tread. The length of a vessel’s keel.

Treads. The steps or horizontal portions of a ladder or staircase upon which the foot is placed.

Treads, Safety. A special non-slipping metal tread fitted to the deck at the foot of ladders and stairways. They are also often fitted to the upper surface of the steps of ladders and stairs. When the steps themselves are safety treads they are called safety steps.

Treble Purchase. A purchase in which two treble blocks are used.

Treble Riveting. See Riveting, Treble.

Tree Nail Turners. Men who operate wood cutting machines which make tree nails.

Tree Nails (Trunnels). A cylindrical wooden pin used to secure the planks of a wooden ship to the frames. After the tree nail is firmly driven into place and cut off flush with the planking its head is expanded by means of a small wedge.

Trestle-Trees. A term applied to fore and aft pieces, whether of wood or steel, that are fitted at the hounds of a mast for the purpose of supporting the cross trees or platform at the top of a mast.

Trim. The longitudinal deviation of a vessel from her designed waterline at a given draft. When expressed in feet and inches it is equal to the sum of the distances that points on the waterline at the bow and stern are above or below the designed waterline at the mean draft at which the vessel is floating. The variation in a vertical direction of the fore and aft extremities of the actual position of a vessel’s plane of floatation from its designed position.

Trim by Head. That condition of trim in which a vessel inclines forward so that her actual plane of flotation is not coincident with or parallel to her designed plane of flotation.

Trim by Stern. That condition of trim in which a vessel inclines aft so that her actual plane of flotation is not coincident with or parallel to her designed plane of flotation.

Trimming Tank. See Tank, Trimming.

Trochoidal Wave. A wave, the contour of which is the curve traced out by a point on a radius of a circle, which latter is rolled on the underside of a given line. This is the wave contour which is usually adopted for use in connection with calculations of bending moment for a vessel among waves.

Trough Tool. A smoothing tool for use on structural shapes.

Truck. The pedestal or ball at the extreme top of the topmast or topgallant mast.

Trundle Head. The circular portion of the capstan

Trunk. A vertical or inclined shaft formed by bulkheads or casings extending one or more deck heights, around openings in the decks, through which access can be obtained, cargo stores, etc., handled or ventilation provided without distributing or interfering with the contents or arrangements of the adjoining spaces.

Trunk Bulkhead. See Bulkhead, Trunk.

Trunk Cabin. A cabin which extends but a partial deck height above the upper or weather deck.

Trunk Deck. See Deck, trunk.

Trunk Deck Stringer. See Stringer, Trunk deck.

Trunk Deck Stringer Bar. See Bar, Stringer.

Trunk Deck Vessel. A vessel having a long continuous opening or hatch in the weather deck. The longitudinal coamings of this hatch are carried up about a deck height above the weather deck and connected at their upper edges by a flat or deck.

Trunk Hatchway. See Hatchway, Trunk.

Trunk, Ventilating. Trunks through which air is led for supplying fans and blowers, or through which heated air is allowed to escape.

Truss. An iron band around a lower mast having a pivot attachment to the center of a lower yard, thus forming the center of motion for bracing the yard around and at the same time holding it in position at the mast; to brail up a sail.

Tub. A short cask or half barrel. Also an opprobrious or contemptuous term applied to a vessel to signify that it is out of date or faulty in design.

Tube Cleaners, Boiler. See Boiler Tube Cleaners.

Tube Expander. A tool used to expand the end of tubes into the sheets or headers of boilers, and into flanges, etc.

Tube Sheet, Condenser. See Condenser, Tube Sheet.

Tube Sheets. See Boiler Tube Sheets.

Tubes, Boiler. See Boiler Tubes.

Tubes, Condenser. See Condenser Tubes.

Tubes, Sounding. Small pipes leading vertically up from a tank and arranged with the lower end opening into the tank so that the liquid rises in the pipe so its height can be measured by lowering a sounding rod into the pipe.

Tug; Tugboat. A vessel, equipped with heavy duty engines and machinery, used for towing miscellaneous types of floating craft.

Tug or Towboat. A small, handy, power-driven vessel fitted with slow-turning powerful machinery, especially designed for towing.

Tumble Home. The decreasing of a vessel’s beam above the waterline as it approaches the rail. (The opposite of flare.)

Tumbler. An attachment to the jaws of a gaff to prevent the chafing of the mast.

Tunnel Frames. See Frames, Tunnel.

Tunnel Plating. The plating composing the structure of a tunnel.

Tunnel Recess. The enlarged end of a shaft tunnel. At the forward end this enlargement is termed the thrust recess and at the after end the stuffing box recess.

Tunnel, Shaft. (Shaft alley) A long narrow compartment running from the propelling machinery to the stern tube and containing the line shafting and its bearings. Fitted in order to provide access to the shaft and shaft bearings as well as to protect the shafting from the cargo in the after holds.

Turbine. A machine in which the kinetic energy of the steam is transformed into direct rotary motion. A reciprocating engine produces work by the relatively slow overcoming of resistance by the pressure of the steam up to the cut off and by the hyperbolic expansion of the steam up to the release while a turbine does its work through the impulse reaction of steam or steam jets at high velocity on rotary vanes.

Turbine Annulus Area. The net area available for steam flow through the blade rings of a turbine.

Turbine Blades. The vanes either on rotor or casing which are subject to and directly effect the travel of the steam through the turbine.

Turbine Blade Friction. The friction produced by the flow of steam across the turbine blades. This friction is much increased by the presence of water in the steam It is accordingly advantageous to make the surfaces of all blading as smooth as may be and to use superheated steam.

Turbine, Compound Impulse Reaction. A turbine in which the principal expansion of the steam occurs in the vanes. The steam velocity is moderate but for good efficiency the peripheral speed of the rotor must be about three-quarters that of the steam speed. Owing to the low rotor speeds used, this type is especially suited to ship propulsion.

Turbine, Cruising. A turbine designed for use at relatively low speeds as compared with the vessel’s maximum. They are designed and fitted to give reasonable economy under cruising conditions. They may be installed either as separate units or be built within the same casing as the high pressure turbine. When fitted independently they are placed on the low pressure turbine shaft.

Turbine Cylinder or Casing. The outer and stationary portion of the turbine. For purposes of construction and access it is made in two portions, the upper and lower half respectively. In large units each part may itself be made up of two or more parts.

Turbine Diaphragm. A division member or plate which separates two adjacent turbine stages from each other. lt consists of a wrought or cast steel division plate riveted at its outer edge to a cast steel rim and at its center to a hub through which the rotor shaft passes. The rim dovetails into the turbine cylinder. The hub is provided with close fitting grooved packing to reduce steam leakage.

Turbine Effective Blade Height. The clear distance between the inner face of shroud ring and the top of foundation ring.

Turbine Efficiency. The ratio of theoretical to actual steam consumption in turbines. The principal turbine losses are those due to steam friction, both against itself and against the blades; exhaust steam velocity; leakage over blade tips at glands, etc.; mechanical friction; radiation. The above losses total almost 40 per cent. Hence the average efficiency to be anticipated in practice may be taken as slightly in excess of 60 per cent.

Turbine Foundation. See Engine Foundation.

Turbine Guide Blades. Fixed or stationary blades carried on the casing of an impulse-reaction type of turbine. These blades receive the steam from the moving blades and while changing its direction of flow also increase its velocity.

Turbine Lifting Gear. Gear designed for lifting the upper casing of the turbine for examination, erection, repairs, etc. When ready for use guides are provided so as to insure movement without damage to blading. The gear proper consists of a motor acting through a system of worms and worm wheels.

Turbine Moving Blades. Blades carried by the rotor and therefore having motion relative to the fixed blades carried by the casing. These blades, or blades having the same function, are fitted in both the impulse and impulse-reaction types of turbine. They receive the steam directly from the nozzles or guide blades and by changing its direction of flow are able to transmit a rotative effort to the turbine shaft.

Turbine, Multiple Stage Impulse. A turbine in which the expansion of the steam takes place in sets of nozzles and from which the steam impinges on vanes set on several revolving discs. Only a limited pressure drop is allowed for each set of nozzles. This keeps down the velocity of exit steam from same and thus reduces blade velocity. Several rows of moving blades are fitted on each wheel and the steam speed falls from row to row. It is accordingly possible to use a much lower peripheral disc speed in the single stage impulse type. Hence turbines of this class are successfully used for main propulsive units in marine installations.

Turbine Nozzle. A device for supplying steam in the proper amount and direction to the rotating buckets of the turbine. The number and size of nozzles are directly dependent upon the horsepower desired. In the first stage, nozzles occupy only a part of the turbine circumference, but in the last stages the entire circumference is taken up. Nozzles are made in segmental castings of suitable size and shape for the location desired.

Turbine Operating Gear. A mechanism for turning the rotor over for repair or examination. It consists of worm wheels on the turbine shafts. These worm wheels are actuated by removable worms and shafts operated by turning engines or other means.

Turbine Reduction Gearing. See Reduction Gearing.

Turbine Rotor. The rotating part of the steam turbine. It is built up of the following principal parts: a cylinder or drum; wheels; shafting; dummy piston. In the construction of the rotor, balance and rigidity are of the first importance in order to insure absence of vibration and accuracy of clearance. The cylinder or drum is worked out of the solid ingot. In large installations two drums may be used, an additional wheel being fitted at the juncture of the drums. Great care is required in handling and boring the drum to avoid distortion due to concentrations of pressure. Wheels may be of various forms and are either cast or forged. Steel forgings are the best practice at the present time. The shafting is suitably turned and the wheels are shrunk thereon. Pins are fitted to guard against the motion of wheel on shaft. The cylinder or drum is then shrunk on to the wheels and secured thereto by riveted screws fitted with means to prevent backing off. The grooves for the reception of the moving blades are worked in the outer surface of the drum. Journals are provided on shafting and the entire weight of the rotor thus transmitted to the main bearings. A dummy piston is placed at the steam end of the rotor. It consists of a series of collars formed on the rotor extension and rings attached to dummy casing and fitted with small clearance corresponding to the collars. Steam leakage is prevented by the wire drawing action of this contrivance.

Turbine Shroud Ring. A ring designed to take the ends of turbine blading, so as to maintain alignment and protect against the action of centrifugal forces.

Turbine, Single Stage Impulse. A turbine in which the expansion of the steam takes place within a set of nozzles and from which the steam issues in jets of high velocity impinging upon vanes set securely upon a revolving disc. The jet velocity of this type has between 2,500 and 4,000 feet per second. The peripheral disc speed is always considerably less than half the jet velocity. Owing to the high speed of this type it is not suited to use for the main drive of an ordinary sea-going vessel. It is, however, much used for driving dynamos on shipboard.

Turbo Generators. A combination consisting of a steam turbine and an electric generator generally on the same shaft. The current furnished by the generator is used for lighting the ship and sometimes for motors on the auxiliary machinery and machines in the engineer’s work shop.

Turn. To cause a rope or chain to encircle a spar, pin or bitt one or more times, also to pass the bight of a rope over a bitt or cleat. The act is generally referred to as taking or catching a turn.

Turn In. To retire for the night.

Turn Turtle. To capsize or to founder. To turn completely over.

Turnbuckle. A device for connecting two parts of a bar, rod or rope together with an adjustable tension. It consists of an internally threaded link turning on screws at each end threaded in opposite directions or- one end may have a swivel and the other a screw. The link is operated by means of a wrench or a lever. Frequently the link is constructed with a hole through the center for applying a marline spike as a lever.

Turning Circle. The approximate circle described by a vessel in turning when the helm is hard over.

Turning Engine. See Engine, Turning.

Turning Gear. An arrangement or device for turning the main engine by power other than its own. In large installations a turning engine, either steam or electric, is used to actuate a large worm wheel carried on the main shaft. In smaller engines the worm wheel may be operated by hand lever or by jack. In very small engines the wheel may be operated by a pinch bar and toothed gear wheel.

Turning Gear Wheel. A large worm wheel mounted on the main shaft in power and the larger hand operated turning gears. In the smaller hand operated gears, a toothed wheel mounted on the main shaft and arranged for operation by means of a pinch bar.

Turpentine, Wood. The resinous juice of pine or fir trees used in mixing paints, varnishes, etc.

Turret Armor. Armor fitted to the turret structure for the protection of the gun and ammunition handling mechanism.

Turret Deck. See Deck, Turret.

Turret Deck Stringer. See Stringer, Turret Deck.

Turret Deck Stringer Bar. See Bar, Stringer.

Turret Deck Vessel. A merchant vessel constructed with a side having an abrupt round over or tumble home at about the level of the main deck from which point the sides are carried up in a reverse curve to the narrow deck termed the turret deck.

Turret Ship. A war vessel in which the main battery guns are mounted in structures (generally protected with armor) carried on rollers and capable of rotation.

Turrets. Structures designed for the mounting and handling of the guns and accessories (usually main battery guns) of a war vessel. Turrets are constructed so as to revolve about a vertical axis usually by means of electrical or hydraulic machinery.

Turtle-Back. Usually applied to the weather or forecastle deck forward as, in naval practice, to protective decks in the vicinity of the water line when of excessive camber or sharply sloped or curved down at side.

Turtle Deck, Turtle-Back. See Deck, Turtle.

’Tween Deck. See Deck, ‘Tween.

’Tween Decks. A term applied to the space between any continuous decks.

’Tween Deck Tonnage. The enclosed space between decks expressed in tons of one hundred cubic feet.

Twice-Laid Rope. See Rope, Twice-Laid.

Twine. Small cotton or flax cord or thread used by sail-makers in working on canvas.

Twofold Purchase. A purchase in which two double blocks are used.

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