T – Code flag; I am engaged in pair trawling. Sound signal; A power driven vessel making way in restricted visibility. Morse Code; ▬.

T flag + Four Numerals – Code flags; Local time.

Tab – Name sometimes given to tabling on a sail.

Tab Nab – A small cake or biscuit served on high days and holidays if the cook felt generous.

Tabernacle – Vertical casing, having three sides at right angles, into which a mast is stepped and clamped.

Table – To strengthen foot of a sail by stitching an additional strip of canvas along it. 2. Flat-topped projection on either side of mast and in same thwartship line. Takes heels of cargo derricks. 3. Pre-computed values set out for ready reference.

Table of Offsets – See Offsets

Table Shore – Low, flat shore of sea.

Tabling – Reinforcing pieces on the edges and top of a sail.

Tabloid Cruiser – A small sailing cruiser.

Tabular – Said of values that have been obtained from tables.

Tabular Log – Logarithm whose index has been increased by 10 to avoid having minus values.

Tachometer – Instrument for indicating velocity. An instrument that indicates the speed of an engine’s revolutions.

Tack – Lower forsemost comer of a fore and aft sail. 2. Rope by which the weather lower comer of a course is hauled down. 3. Direction of a vessel’s fore and aft line relative to the wind when under sail; being starboard or port tack according to whether wind is on starboard or port side respectively. 4. Distance sailed on one tack. 5. Lower corner in head of flag or pendant.

Tack Block –Standing block through which tack (rope) of a sail is rove.

Tack Knot – Double wall and crown knot worked in standing end of a tack (rope).

Tack Line – Length of signal halliard inserted between two groups of signal flags when hoisted at the same halliard.

Tack Pins – Old name for ‘belaying pins’.

Tack Purchase – Gun tackle purchase in tack of a fore and aft mainsail.

Tack Rivet – Temporary rivet put in to hold a plate in position while being erected and faired. It is then punched out and the permanent rivet inserted.

Tack Tackle – Small tackle used for sweating down tacks of courses.

Tack Tricing Line – Line fitted with a thimble and used for tricing tack clear of the water when vessel is lying over.

Tacking – Putting ship’s head through the wind, and so bringing wind on the other bow. 2. Working to windward, under sail, by sailing alternately on different tacks.

Tackle – The running gear of a ship. 2. Purchase made by reeving rope or chain through one or more blocks.

Tackle Boards – Frame, at end of a ropewalk, having attachments for yams that are to be twisted into strands.

Tackle Post – Fitting, in a ropewalk, having attachments for laying-up strands of a rope.

Tackling – Sails and all running rigging of a vessel.

Tactical Diameter – See advance.

Taffrail – Originally, upper edge of stern. Later, an ornamental rail going around stem and above the original taffrail. Now, upper edge of bulwark around the stem.

Taffrail Log – Name given to a patent log towed from aft.

Tag – Strongly-built and fully-engined vessel especially designed for towing.

Tail – A rope spliced into the end of a wire halyard or brace.

Tail Block – Block having a short rope tail spliced around strop at head, for attachment by hitching.

Tail Board – Carved work under bowsprits of old ships.

Tail Jigger – Jigger with a selvagee tail, instead of a hook, in the double block.

Tail of Bank – Seaward end of a longitudinal shoal in an estuary.

Tail Off – To maintain pressure on the end of a line as it comes off a winch.

Tail On – Order to assist in manning the fall of a tackle.

Tail Shaft – That part of a propeller shaft shaft that passes through the stem tube and is fitted to take attachment of the propeller.

Tail Splice – The joining of one rope to another rope that diners in size, or in material.

Tail Tackle – Luff tackle, or watch tackle, with rope or selvagee tail in head of double block, and hook in single block.

Tail-end Shaft – ‘Tail Shaft.’

Take a Turn – To take a temporary turn with a rope preparatory to taking in some more of it.

Take Charge – To break away from control.

Take In – To furl, or to lower, sails. 2. To load. 3. To haul in. 4. To receive.

Take Up – Said of seams of a boat when they tighten up and cease to leak.

Taken by the Lee – Said of a sailing vessel when her sails are thrown aback by a sudden shift of wind.

Taking Off – Said of tide or wind when it is getting less.

Tall Ship – A large sailing ship.

Tallant – Rounded upper part of a rudder. See Also: Types of Ship Rudders, Its Parts, and Profiles.

Tally – To count. Particularly applied to the count of items loaded or discharged by a vessel. 2. The count obtained from tallying. 3. Agreement in numbers or quantities.

Tally Board – Board, bearing instructions, that comes to a wrecked ship with a life-saving rocket line.

Tally Book – Book in which is kept a reckoning of items of cargo received or discharged from a hatch or vessel.

Tan – Solution of gum and dark red dye. Used for preserving sails.

Tandem Block – Block having two sheaves in the same plane. Tangent. Line that touches circumference of a circle but will not cut the circumference if produced in either direction. More precisely, a line that is perpendicular to the radius of circle at the point of contact with the circumference.

Tangent Circle – Circle at which the surface of a conical or cylindrical projection touches the sphere. In cylindrical projections it is a great circle; in conical projections it is a small circle.

Tangent Point – That point, on a sphere, at which the plane of the projection touches it.

Tangent Sailing – Name formerly given to ‘Middle Latitude Sailing’.

Tank – In general, any cistern or reservoir in which liquids are stowed. Particularly applied to one containing water ballast, fresh water, oil-fuel, etc.

Tank Cleaning – Removal of all traces of a cargo from the tanks of a tanker by means of high pressure water jets.

Tanker – Vessel specially constructed for carrying liquids in bulk. Vessel constructed for carrying oil in bulk. Related Article: How to Identify Oil Tanker Sizes- Handymax, Panamax, Aframax, Supertanker

Tap Rivet – Rivet substitute having thread on shank and a head shaped to take a spanner. Used in places where riveting is impossible. Holes are threaded, tap rivet is screwed home, head is then cut off.

Tapered Ropes – Ropes whose circumference gradually diminished towards one end. Formerly used for sheets and tacks in Royal Navy. While having full circumference at working part, the rope rendered easily through a sheave or block when veered or slackened.

Tapering – Gradually reducing diameter of extreme end of rope so that end is easily passed through a block or thimble.

Tar – In nautical work, usually means Stockholm tar. Coal tar, however, is often used for preservation of steel decks, particularly the refined tars. Black tar varnish is often used for coating outside of underwater steel plating. 2. Colloquial name for a blue-jacket; rarely applied to a Merchant Navy seaman.

Tare – Amount to be deducted from gross weight to ascertain nett weight of a commodity that is packed.

Tare Weight – The weight of the container of the cargo. Gross weight equals the net weight of cargo plus the tare weight of the containing packaging or receptacle.

Tarpaulin – Originally, canvas dressed with tar, or a substitute for tar. Now applied to canvas treated with a waterproofing and preservative dressings. Used for covering hatches, and for protective purposes. 2. Old name for a seaman. 3. Old name for a seaman’s waterproof hat.

Tarpaulin Canvas – Rather coarse but flexible canvas. Made from second quality yarns, but not lacking in strength, and free from jute.

Tarpaulin Master – Old name for a general collection for a charitable purpose. Name probably arose from the passing round of a tarpaulin hat.

Tart – Tight or well stretched. Neat.

Tart Leech – Said of a sail when well hoisted and having no tendency to bag’.

Taunt, Taunto – High, or tall. Said of masts that are unusually high, or of a vessel having high masts.

Taurus – (Lat. =’Bull’.) Constellation situated between R. A. 03 h 20 m and 04 h 40 m and Dec. 8° to 27°N. Has two navigational stars (Aldebaran and Nath). Also, second sign of Zodiac, extending from 30° to 60° celestial longitude. Due to precession of equinoxes, constellation Aries is now in sign Taurus, and constellation Taurus is mainly in sign Gemini. Sun is in Taurus from April 21 to May 20 (about).

Taut – Tight.

Taut Bowline – Said of a bowline when it is fully stretched with ship sailing closed hauled. ‘On a taut bowline’ denotes a vessel sailing close hauled and as near to wind as possible.

Taut Wire Measuring Gear – Used in surveying ships to indicate an exact distance run. About 140 miles of pianoforte wire is carried on a drum, one turn being led round a ‘counter’ wheel having a circumference of .01 of a cable, 0.001 of a mile. End of wire is weighted and lowered to sea-bed. As ship goes ahead, the wire is allowed to go out. Number of revolutions of ‘counter’ wheel is registered, thus giving a distance. Accuracy is within 0.2 per cent.

Tavistock Theodolite – Instrument used for precise measurement of angles in marine surveys.

T-Bar – Rolled steel section of T-shape.

Tchebycheff’s Rule – For finding area of a figure bounded by straight lines and a curve. Ordinates are drawn to suit shape or curve, their mean value being multiplied by length of base line. Used as an alternative to ‘Simpson’s Rules‘.

Teak – Valuable and important wood grown in India and Burma. When seasoned, will not warp, split, crack, or alter shape. Is not injured by contact with iron, is easily worked and is not attacked by ants or other insects. Specific gravity, 0.64.

Tee Bar Bulbed – Tee bar with bulb along lower edge.

Teem – To pour. To empty.

Telegraph – Engine-room or Docking Telegraph. A mechanical or electrical device which, on a lever being moved, transmits or acknowledges orders for engine movements or handling of ropes.

Telegraph Men – Hands stationed on bridge of a steam, or motor, vessel to work engine-room telegraphs as ordered.

Telegraph Ship – Vessel specially constructed for laying, picking up, or working on, a submarine telegraph cable. Cable ship.

Telemotor – Steering-gear which controls a steering engine by hydraulic pressures set up by movements of the steering-wheel.

Telescope – Optical instrument for magnifying image of distant objects, so making them to appear nearer. Crude form was in use before 1570. In 1608, two Dutch spectacle makers, Jansen and Lippershey, made three instruments ‘for seeing at a distance’. Galileo improved on these by using double concave eyepieces. Kepler introduced convex eyepiece. Light-collecting power depends entirely on area of object glass. Different types include terrestrial, refracting, reflecting, and prismatic telescopes—and the periscope.

Telescopic Funnel – Funnel that can be lowered vertically, either entirely or in sections. Originally used in vessels having sails and engines. Now confined to small craft that pass under bridges.

Telescopic Topmast – Topmast that can be lowered inside a tubular lower mast when required. Telltale. General name for a mechanical indicator—such as the pointer on a helm indicator, or the repeating pointer from engine room. Formerly, was an indicator on beam of cabin—showing position of helm or rudder.

Tell-Tale Compass – Inverted compass formerly attached to beams of cabin so that direction of ship’s head could be ascertained at any moment by the Master.

Tell-Tale Shake – The shaking of a rope, by a man working aloft, to indicate that he wishes it to be slacked or let go.

Temper – The opposite to anneal. When hardened tool steels are heated and cooled slowly they become soft. The tempering process is one of heating the metal to cherry red then plunging it into water to cool quickly.

Temperate Zones – Those areas of Earth’s surface lying between the Arctic and Antarctic Circles and the Tropics.

Temperature Gradient – Rise or fall in temperature of a mass as registered in a horizontal direction through the mass.

Tempest – Violent wind storm.

Template, Templet – Piece of thin wood, or metal, cut to shape of a required fitting or member, and so acting as a pattern. 2. Perforated strip of metal used as a guide for siting rivet holes.

Tend – To attend. Formerly said of a vessel at anchor when she swung to the prevailing tidal stream.

Tendency – Inclination to change. Particularly applied to changing of barometric pressures. ‘Barometric Tendency.’

Tender – Said of a vessel having a small righting moment; so being easily moved from her position of equilibrium, and slow in returning to it. 2. Small vessel employed in attending a larger vessel, or vessels. 3. To offer for acceptance, or consideration. The act of offering for acceptance or consideration.

Tender Vessel – One that is easily heeled due to a high centre of gravity.

Tenon – The heel of a mast, shaped to fit into the mast step. A squared end to a timber machined to fit tightly into a mortice.

Tenor – General meaning, or purport, of a document or statement.

Tensile Strength – Amount of tension that can be put on a member or fitting without rupturing it.

Tensile Stresses – Of a ship, are those components of hogging and sagging stresses that tend to rupture the fore and aft members of her construction.

Tension – State of being stretched or strained so that rigidity is generated. 2. Name sometimes given to ‘voltage’.

Tentacle – An animal/insect’s flexible appendage used for feeling or moving.

Tenth Wave – Commonly believed to be higher than preceding nine waves. Although it is true that wind effect causes one wave to override another, and so make a larger wave, it is not established that the eleventh wave will do this—so making a larger tenth wave. In some places the fifth wave is consistently larger.

Tephigram – Diagram showing atmospheric conditions at various levels of altitude.

Terce – Cask holding 42 gallons, 1/3 of a pipe or butt. Tierce.

Tercentesimal Scale – Temperature scale in Absolute units, so going into the third ‘hundreds’.

Teredo – A marine borer that is destructive to wooden planking and wharf piles.

Teredo navalis – Soft, cylindrical mollusc, about 24 to 30 inches long, that bores into timbers of wooden ships. Has small shells attached to tail, and uses these for lining the hole made.

Teredo Worm – Common name for ‘Teredo navalis’.

Term – Short name for ‘Term Piece’.

Terminator – Line dividing illuminated surface of Moon from surface not illuminated. Sometimes applied to same line on planets, including Earth.

Terrada – Oriental sailing vessel of 16th century, usually having one or two masts.

Terrestrial – Pertaining to Earth. Used generally to differentiate points, lines, and circles of terrestrial sphere from similar points, lines, and circles of celestial sphere.

Terrestrial Magnetism – Natural magnetism of Earth.

Terrestrial Radiation – Emission of heat by land during night.

Terrestrial Telescope – The telescope generally used at sea. Object viewed is observed correctly, and not inverted. This rectification causes a certain amount of light to be lost.

Territorial Waters – Water adjacent to a coast and over which the sovereign power of the country claims control. Usually taken as being within three miles off the coast, but this is not universally accepted. There is no hard and fast international agreement on the application of this rule to wide estuaries, gulfs, bays, etc.

Test Head – A head of water corresponding to the prescribed pressure test for bulkheads, tanks, compartments, etc., watertightness.

Tethys – Greatest of the sea deities of Greek mythology. Wife of Oceanus and mother of all great rivers, and of 3000 Oceanides.

Tew – To beat hemp for ropemaking.

Tewing Beetle – Flat piece of wood formerly used for beating hemp.

Texts – (List of contents of the CD)

Thalamites – The oarsmen in ancient Greek triremes, who sat lowest, or next to the vessel’s sides.

Thames Measurement – Yacht measurement by ‘Thames Tonnage’. Historically TM = (length x width x depth) ÷ 100. Latterly TM=((length-width) x (width x ½ width)) ÷ 94.

Thames Tonnage – Yacht measurement introduced 1855 by Royal Thames Yacht Club. Calculated by [B2 (L-B)] /188 when B is beam loo and L is extreme length in feet.

Theoretical Navigation – Old name for all calculations made for fixing ship’s position. It thus included Common and Proper Pilotage—or Pilotage and Navigation.

Thermal Conductivity – Efficiency, of a substance, to conduct heat; silver having the greatest thermal conductivity.

Thermal Efficiency – Work done by an engine when expressed as a ratio of the heat energy in the fuel consumed. Due to funnel emissions, radiation, and other losses, maximum thermal efficiency – of boilers and engines combined is about 0.3; of turbines is about 0.2, reciprocating engines about 0.17.

Thermogram – Recording made by a thermograph.

Thermograph – A recording thermometer.

Thermometer – Instrument for measuring temperature, usually by the expansion or contraction of a column of mercury or alcohol. As the range of these two substances is somewhat limited, it is necessary to use other means for measuring high temperatures. Instruments for measuring furnace temperatures are ‘pyrometers’.

Thermometrograph – Self-registering thermometer made by Cavendish, 1752.

Thermostat – A temperature sensitive device used to operate a control mechanism. A valve that opens or closes in response to temperature

Thermotank – Casing containing pipes through which steam, cold water, or brine may be passed. Air for ventilation can be drawn round these pipes, and so brought to any required temperature.

Thick and Thin Block – Block having two sheaves, of different sizes, through which two different ropes were rove. They were fitted, for example, on quarters of a yard to take sheet and clewline.

Thieves – In marine insurance are persons, not belonging to the ship, who commit robbery with studied intent.

Thimble – Metal ring, with concave side into which a rope may be spliced, or seized; thimble can then take shackle pin, hook, or rope without chafing rope into which thimble is fitted. Made in various shapes. Usually of galvanised iron, steel, brass, or gunmetal.

Thimble Eye – Round hole, in steel or iron plate, with edge rounded or built up so that a rope can be rove through it instead of through a sheave.

Thirty-day Returns – Proportional repayment of insurance premiums for each 30 days an insured vessel is laid up, or taken off insurance.

Thole – A device for holding an oar in place when rowing or steering. One of a pair of wood or metal pins set vertically in the gunwale of a boat that serve as oar locks. See oarlock & rowlock.

Thole, Thole Pin – Metal or wooden peg inserted in gunwale of a boat for oar to heave against when rowing without crutch or rowlock.

Thomson Deflector – See ‘Deflector’.

Thomson’s Sounding Machine – The earlier type of the Kelvin Sounding Machine. Line used was two pianoforte steel wires twined round one another.

Thornycroft Boiler – Water-tube boiler consisting of two lower water drums and an upper steam drum, connected by curved tubes, and all mounted in the heating space.

Thorough Pat – Thoroughfoot.

Thoroughfoot – The fouling of a tackle by one of its blocks being passed through the running parts of the tackle. Probably a corruption of ‘through put’. Also said to be “dipped”. 2. To thoroughfoot is to remove kinks from a coiled wire.

Thranites – The uppermost oarsmen of the three tiers of a Greek trireme.

Thrascias – See classical winds.

Thrashing – Said of a vessel under sail when she is sailing fast on a wind.

Thread – Two or more single yarns twisted together.

Threatening – Term applied to weather when the indications are that it will become bad, or worse.

Three Half Hitches (are more than the King’s yacht wants) – Rebuke to those who make excessive and unnecessary fastenings of ropes.

Three L’s – Lead, latitude and look-out. First used by Sir John Norris (1660-1749) as being the best guide for ‘Coming up the Channel’.

Three Sheets in the Wind – Said of a man under the influence of drink. A ship with three sheets in the wind would ‘stagger to and fro like a drunken man’. Conversely, a drunken man staggers to and fro like a ship with three sheets in the wind.

Three-Circle Type – Name given to a sextant in which strength and rigidity of frame are obtained by having three open circles, in form of a trefoil, incorporated in the frame.

Three-Decke –. Ship having three gun decks below the upper deck; thus having five decks in all. Name is sometimes given to a sea pie made of layers of meat, vegetables, and pastry.

Threefold Purchase – Purchase rove through two treble blocks, so gaining a power of six or seven—depending on which block moves.

Three-Island Type – Name given to cargo vessels having raised forecastle, midship houses, and poop, and rather low freeboard elsewhere. Distinguishes them from flush deck vessels, and others.

Three-Point Problem – Name given to problem of fixing position by measurement of horizontal angles between three identified and charted objects. Now solved by the Station Pointer.

Three-Stranded – Defines all ropes having three strands.

Throat – The part of a gaff that rests against a mast, and from which the jaws spring. 2. Fore upper corner of a fore and aft sail. 3. Angle at junction of arm and shank of an Admiralty pattern anchor. 4. Interior angle of knee or compass timber.

Throat Bolts – Eye bolts in jaw end of gaff and in lower part of a top. They take hooks of throat halliards.

Throat Brails – Brails that lead through blocks below jaws of a gaff.

Throat Downhaul – Rope for housing down the throat of a gaff.

Throat Halliard – Rope or purchase for hoisting throat of a gaff.

Throat Seizing – Put round two parts of a rope that has a circular bight and the parts going in opposite directions. Similar to a round seizing but without the trapping turns.

Throttle – Hand accelerator unit on an outboard engine.

Through Bill of Lading – Bill that covers transit of goods from consignor to consignee when more than one means of transport is employed.

Through Fastenings – Nails, screws, bolts, rivets, etc., that go through all parts they join together, the outer ends being so secured that accidental withdrawal is precluded.

Through-hull Connection – A hull fitting used to connect piping with the atmosphere outside with a watertight connection through the hull.

Thrum – To pass small tufts of rope yarns through canvas to make a mat. 2. The small tuft so used.

Thrum Mat – Mat made by thrumming rope yarns, or other fibres, into a textile backing.

Thrust – A pushing force exerted along a line.

Thrust Bearing – A bearing designed to absorb the forward thrust of the propeller.

Thrust Block – Substantial fitting secured to a vessel to take the thrust of screw propeller, and so cause vessel to move ahead or astern. In simpler forms, webs on thrust shaft work in grooves in thrust block. See ‘Michel Thrust’.

Thrust Shaft – That section or propeller shafting which transmits propeller thrust to thrust block, and so to ship.

Thruster – A controllable propeller placed in the athwartships direction to provide a transverse thrust to assist a ship in manoeuvring.

Thuban – Star α Draconis. R. A. 14 h (approx.); Dec. N64 1/2°; Mag. 3 (var.). When Great Pyramid was built it was the pole star.

Thumb Cleat – Small cleat having only one horn. Generally used as a fairlead.

Thumb Knot – Name sometimes given to the ‘overhand’ knot. Related Article: Can You Knot? 10 Widely Used Knots on Merchant Ships.

Thunder – Noise made when lightning flash passes through atmosphere and causes rapid expansion and contraction of air. As flash is comparatively long,. the noise from each point in path arrives later as its distance from observer increases, thus giving a continuous sound.

Thunder Cloud – Unusually dark nimbus cloud from which lightning flashes emanate.

Thunderbolt – Lightning flash that touches surface of Earth and causes damage. Name is sometimes given to a meteorite that strikes Earth.

Thunderstorm – Storm in which thunder is heard; caused by decreases in upper air temperatures being abnormal. This vertical instability causes large cloud formations, with correspondingly large electrical charges.

Thwart – Transverse seat in a boat, for rowers to sit on.

Thwart Hawse – Forward of and across the fore and aft line of another vessel.

Thwart Marks – Old name for ‘leading marks’.

Thwartships – Usual contraction of ‘athwartships’. At right angles to the fore and aft line of the ship.

Ticket – Colloquial name for a ‘Certificate of Competency’. Generally looked upon with disapproval.

Tidal – Pertaining to tides.

Tidal Basin – An area of water that is partly enclosed, but is subject to fluctuations due to rise and fall of tides.

Tidal Bore – A wave caused by constriction of spring tide as it enters a long narrow shallow inlet.

Tidal Constants – Amounts by which the tide, at a particular place, diners from tide at a port of reference. They may be ‘time’ or ‘height’ constants. Time constant applied to time of high or low water at port of reference will give approximate time of high or low water at that particular place. Similarly, height constants will give heights of high and low water.

Tidal Current – Name sometimes given to ‘tidal stream’.

Tidal Friction – Retardation of Earth’s rotation by Moon’s tractive effort on atmosphere and waters of Earth; so causing day to be lengthened by about 0.002 of a second in 100 years. In about 50, 000, 000, 000 years the day and month will be of equal length (about 47 x 24 hours).

Tidal Harbour – Harbour whose depth of water depends on state of tide.

Tidal Paradox – Applied to the phenomenon of a fall in surface level of water when a tidal current flows over a submerged shoal.

Tidal Prediction – Forecasting of times and heights of tidal undulation at a given place; or of the rise or fall in sea level at a given place at a given time.

Tidal River – River whose depth and rate of flow are affected by tides of the sea.

Tidal Species – The different categories into which tides and component tides can be placed. Principal arc Diurnal, Semidiurnal, Quarter Diurnal, and Long Period mixed tides result from combination of two or more of these.

Tidal Stream – Periodical horizontal movement of water, in seas and oceans, caused by tide-producing forces.

Tidal Types – ‘Tidal species.’

Tidal Undulation – The rhythmic rise and fall of sea level due to tide-producing forces. A bore, or aeger, is not an undulation.

Tidal Waters – Waters affected by rise and fall of tide, or by tidal currents.

Tidal Wave – Name given, erroneously, to an unusually large wave—that is generally due to anything but tidal action. A tsunami.

Tide – Periodic rise and fall of sea surface, at any given point, due to tractive and gravitational effects of Sun and Moon, together with centrifugal effect of Earth’s gyrational movement.

Tide – The regular raising and lowering from mean sea level due to the gravitational effect of the moon and sun (and other planets).

Tide Chart – Is a graphical representation of the range of highs and lows throughout the period with the springs and neaps recorded. Data includes Tide tables, tides, tidal predictions and graphical data for more ports worldwide.

Tide Day – Lunar day. 2. Interval between successive high waters of a diurnal tide; between high water of one semidiurnal tide and the second following high water.

Tide Gauge – Instrument for measuring height of tide, or for indicating it. Usually automatic in action.

Tide Pole – Iron tube, or rectangular wooden spar, used for observing tidal rises during marine surveys. Usually painted black and white—in alternate feet— with graduations that can be read from a distance.

Tide Rip – Disturbed water due to tidal current passing over marked inequalities in the bottom.

Tide Rode – Said of an anchored vessel when her head is pointing in direction from which a tidal current is flowing.

Tide Tables – Pre-computed tables giving daily predictions of times and heights of high water—often, of low water—at selected ports and positions. 2. Ancillary tables for deriving times and heights of tide at selected secondary ports, from tabulated tides. Also, tables for finding heights of tide at a port at times intermediate between high and low waters.

Tide Waiter – Alternative name for ‘Tidesman’.

Tide Water – Navigable water affected by rise and fall of tide, or by tidal currents.

Tide Way – An area experiencing the full force of the tide.

Tide-rode – A vessel whose bow is swung into the tide.

Tidesman – Customs officer who boards a vessel on arrival, and remains on board during discharge of cargo. 2. Customs officer employed during certain states of tide.

Tideway – Channel through which a tidal current runs, particularly that part in which current has its maximum rate.

Tie – Short rope, other than a gasket, used for securing a sail when furled.

Tie Down – A line securing an object.

Tie Rod – A through bolt to stop a hull or structure from falling outward.

Tieplate – Plate fitted between, and attached to, two members to maintain their distance apart, or relative positions. 2. Iron plate extending athwartships, on under side of deck, in way of mast of a sailing vessel. Placed to prevent mast wedges distorting deck planking in way of mast.

Tier – Mooring buoys at which several vessels lie alongside each other. 2. Hemp cable when flaked down for running. 3. Grating or spar shelf on which hemp cable was flaked for running. 4. A range of casks. 5. Row of vessels moored alongside one another.

Tierce – Cask holding 42 gallons. When used for salt provisions were in two sizes; one contained about 304 Ib., the other about 336 Ib.

Tight – Said of a ship when she does not leak.

Tiller – Lever, in head of rudder, by which steering is effected by government of the rudder.

Tiller Arm – An arm extending from the rudder stock which can be used to manually turn the rudder.  A bar that acts as a lever for steering, connected to the rudder stock.

Tiller Chain – Chain going between tiller and the machinery by which rudder is governed.

Tiller Head – The inboard end of tiller, at which it is actuated.

Tiller Rope – Rope connecting drum of steering-wheel with tiller.

Tilt – Canvas awning over stem sheets of a boat.

Tilt Boat – Small rowing boat having an awning, or tilt, for the protection of passengers.

Timber – Wood that has been dressed, or partially dressed. 2. Frame of a wooden vessel or boat. 3. Large piece of wood used in the construction of a wooden vessel.

Timber and Room – Horizontal distance from one frame of a wooden vessel to the next frame. Measured by width of the timber, plus space between frames.

Timber Dogs – Two claws riding on a single ring. Used for gripping timber logs for lifting.

Timber Head – Projection of rib of a wooden ship above the deck, for use as a bollard. Name now given to wooden bollards on piers and wharves when they are heads of vertical timbers.

Timber Hitch – Made by passing rope round a spar and then taking end round standing part and dogging it round its own part. With an additional half-hitch it is the appropriate method for towing a spar or piece of timber.

Timber Load Line – Special load line used only when carrying a timber deck cargo.

Timber Spacing – Alternative name for ‘Timber and room’.

Time – Mode by which is measured the passage of events. A measure of duration. In navigation, all time is measured by hour angle of a specific body or point, and is based on diurnal rotation of Earth, monthly revolution of Moon around Earth, the annual revolution of Earth round Sun.

Time Azimuth – Bearing, of a heavenly body, derived from latitude of observer, declination and hour angle of the body observed.

Time Charter – Agreement whereby a shipowner leases his vessel to a charterer, for a specified period and under conditions agreed.

Time Clauses – Institute clauses applicable to a ‘Time’ policy of insurance.

Time of Origin – Time at which a signal is ordered to be sent. Serves as a reference number identifying the signal.

Time of the CLosest Point of Aooroach (TCPA) – Plotted time of closest approach of a radar target.

Time Penalty Clause – Inserted in a policy of marine insurance to free insurer from all claims for loss consequent on loss of time.

Time Policy – Contract of insurance covering a risk for a specified period, not exceeding one year for marine insurance policies.

Time Signal – Visual, radio, or telegraphic signal made to indicate an exact instant of time.

Time To Go (TTG)  GPS indicator of the time it will take to reach the waypoint at current speed.

Time Zones – Sectors of Earth’s surface bounded by meridians 15° apart, zero zone being 7 1/2° on either side of prime meridian. Times kept in these zones vary from Greenwich in complete hours. Each zone is identified by a figure denoting the number of hours that its time differs from G. M. T., and a sign,+ or —, indicating how the difference is to be applied to Zone Time to get G. M. T.

Timeneoguy – Small rope tautly stretched to prevent sheets and tacks fouling when working ship. Originally, was a tack tricing line that kept sail from obscuring view of helmsman, or ‘timoneer’.

Tingle – Sheet of lead or copper that has been tacked on outside of a boat to stop a leak. Usually put over canvas, fearnought, or other fabric that has been soaked in tallow or oil. A pad of oakum is often used.

Tinny – Australian slang for an aluminium dinghy.

Tinny to Tanker – A past AMSA initiative to facilitate seafarers transitioning commercial vessel licenses from small domestic craft to international shipping, no longer being progressed.

Tipping Centre – That point, in fore and aft line of a vessel, that does not rise or fall with change of trim. It is the point at which the tipping change appears to be hinged.

Title of Chart – Includes particulars regarding date of survey, names of ship and officers engaged in survey, compass variation at a given date, secular change in variation, geographical position of a named point, units used for denoting soundings, tidal data, conspicuous objects, natural scale of chart, abbreviations used. Modern charts rely on Chart 5011 for much of this information.

Toe Rail – An edging rail around the weather deck.

Toggle – Piece of wood, or other material, used in conjunction with a becket when quick attachment or release is required. Any small spar passed through eye of rope, that has been rove through an aperture or ringbolt, is a toggle.

Toleration – Amount of inaccuracy that can be accepted in any item that is made to specified dimensions.

Tom Bowling – The ideal seaman. Immortalised in Dibden’s song, and in Smollett’s ‘Roderick Random’.

Tom Cox’s Traverse – Work done by a man who bustles about doing nothing. Usually amplified by adding ‘running twice round the scuttle butt and once round the longboat’.

Tom, Tomm – To shore up. 2. A shore, or support.

Tomahawk – Small pole axe used for fire-fighting, and other purposes.

Tommy – 18th century term for (soft) bread as distinct from ship’s biscuit.

Tompion – Plug put in muzzle of gun to keep bore clean and watertight.

Ton Register – Obsolete unit of ship tonnage, 1 TR =100 Imperial cubic feet.

Tongue – Upper main piece of a built mast. 2. Rope spliced into upper part of a standing backstay. 3. Clapper of a bell.

Tonnage – Expression of a ship measurement that is not necessarily based on weight. In some cases it is derived from cubic capacity —this usage being ascribed to the number of ‘tuns’ that would stow in the space. The principal ship tonnages are Gross, Net, Displacement, Deadweight, and Under Deck

Tonnage – The weight of a vessel.

Tonnage Deck – That deck that forms the upper boundary of the space measured when assessing tonnage. In vessels having less than three complete decks it is the upper deck. In all other cases it is the second deck from below.

Tonnage, Gross – The entire internal cubic capacity of a vessel expressed in tons of 100 cubic feet each.

Tonnage, Net – The internal cubic capacity of a vessel remaining after the capacities specified spaces have been deducted from the gross tonnage.


Tonne – Metric unit of weight. Equals 0.9842 avoirdupois ton and 1000 kilo.

Tonnes Per Centimetre (TPC) – The mass which must be added to, or deducted from, a ship in order to change its mean draught by 1 cm. T.P.C. Tonnes Per Centimetre. Tonnes required to change the vessel’s mean draft by one centimetre. The buoyancy created by increasing the draught by 1 cm.

Tons Burden – Carrying capacity of a vessel expressed in tons. In Section 3 of Merchant Shipping Act it means ‘net registered tonnage’.

Tons Gross – Measure of below deck spaces and superstructure of full width.

Tons per Inch – Number of tons required to increase a vessel’s draught by one inch at a given draught.

Top – Platform at head of lower mast. Rests on trestle trees and thwartship bearers. Gives a good spread to upper rigging. 2. Division of the watch in Royal Navy.

Top Block – Iron-bound block, connected to eyebolt under lower cap, to take the top rope when sending topmast up or down.

Top Brim – Top rim.

Top Button – Truck at a mast head.

Top Chains – Preventers, in sailing warships, that took weight of the lower yard if slings were shot away.

Top End – Rectangular block at lower end of piston of a marine reciprocating engine. Upper end of connecting rod is hinged into it.

Top Hamper – The fittings, furniture, and tackles that are above the upper deck of a vessel; more especially those that are aloft.

Top Lantern – Lantern from which a ‘top light’ is shown.

Top Light – Light shown from a main or mizen top as a guide to following warships when in line ahead.

Top Lining – Doubling piece of canvas, on after side of topsail, to take any chafe against the top rim. 2. Platform of thin wood fastened on after side of crosstrees.

Top Maul – Maul kept in fore and main tops for removing topmast fid when required.

Top Minor – Hole through which a strand is drawn to twisting machine when making rope by hand.

Top Rim – Edge of the top on lower masts of sailing ships. After side was often fitted to take stanchions. Usually divided into ‘fore’, and ‘after’, and ‘side’ rims. Name was given, also, to a curved beading, on fore side of rim, to reduce chafing of topsail.

Top Rope – Rope by which a topmast is hoisted or swayed up.

Top Tackle – Purchase used for swaying a topmast.

Top Timber – Timber immediately above the futtocks in ribs of ship’s side.

Topgallant – The square sail set above the course sails (lowest), lower topsail and upper topsail of a sailing ship.

Topgallant Bulwarks – ‘Quarter boards.’

Topgallant Forecastle – Short deck right forward, and raised above the upper deck, to carry machinery for working cable.

Topgallant Mast – Mast above topmast. When royal yards are crossed the mast is longer: the upper part being the royal mast, the lower part being the topgallant mast.

Topgallant Yard – Yard next above topsail yards. Topgallant sail is bent to it.

Top-heavy – Too much weight aloft.

Topman – Seaman whose duties are in the top when under sail. 2. In Royal Navy, is a rating in the ‘foretop’ or ‘maintop’ division of a watch.

Topmark – Identification shapes above buoys. Related Artice: The IALA Buoyage Systems – Seafarer’s Aids to Navigation.

Topmast – Mast immediately above a lowermast—into which it may be telescoped, or to which it may be fitted.

Topmast – The mast can be in two or three sections, the lower mast, the topmast and the topgallant mast.

Topmast Backstays – Two stays leading aft, one on cither side, to stay a topmast against forward acting forces.

Topmast Stay – Standing rigging that stays a topmast in a forward direction. That on fore topmast is set up well forward on deck. Main and mizen topmast stays are set up in fore and main tops, respectively. Alternatively, they may be doubled in number and led to either side of ship forward of the mast.

Topping – Raising one end of a yard or boom higher than the other end.

Topping a Furnace – See ‘Priming and Topping’.

Topping lift – Rope or tackle for lifting the head of a derrick or boom.

Topping Maul – Carpenter’s hammer having a conical point and large, flat, circular head.

Toprail – Rail, supported by stanchions, along after edge of a lower top.

Topsail – Sail next above course in square-rigged vessels, and above mainsails in fore and aft rigged vessels. Those in square-rigged vessels originally carried three reefs. In merchant vessels, the sail was, later, divided into an upper and a lower topsail, both without reefs.

Topsail Breeze – Fresh breeze in which a yacht can carry topsails.

Topsail Halliard Bend – Made by taking three turns around a spar, then end around standing part and under all three turns, then back over two turns and under the last turn. Allows spar to be hoisted close to block.

Topsail Schooner – Schooner, usually two-masted, having square topsails on fore mast.

Topsail Sheet – Rope by which clew of a topsail is hauled out. To ‘pay a debt with a topsail sheet’ is to sail without paying the debt.

Topsail Yard – Yard to which head of a topsail is bent.

Topside Line – Sheer line drawn above top timber at upper edge of gunwale.

Topsides – That part of ship’s side that is above waterline. Used colloquially for ‘on deck’.

Tormentor – Large fork used for lifting boiled salt meat out of a galley copper.

Tornado – Whirlwind having a diameter of less than a quarter of a mile, and a speed of travel of about 30 knots. Wind velocity may exceed 200 knots. Local effects may be disastrous.

Torpedo – Fish that kills its prey by making physical contact and discharging electricity. Varies in weight between 20 and 100 Ib. Its electrical shock can kill a human being. 2. Name formerly given to a submarine mine or any container of explosive fired, above or below water, when alongside an enemy vessel. 3. Locomotive container of explosive that can be adjusted to travel at a desired depth, along a pre-arranged course or courses—and to explode on graze or impact.

Torpedo Boat – Small, fast craft introduced for attacking large warships with torpedo. First in Royal Navy (1877) was H. M. S. ‘Lightning’, 27 tons, 19 knots. Modern torpedo-boats are motor-propelled.

Torpedo Booms – Steel booms hinged near waterline and with heads attached to a steel ridge rope to which a torpedo net was laced. Netting was normally carried on shelf along ship’s side. When torpedo attack was expected, nets were dropped and booms hauled perpendicular to ship’s fore and line; thus forming a net screen against torpedoes.

Torpedo Catcher – Fast craft designed for attacking and destroying torpedo boats. First in Royal Navy was H. M. S. ‘Rattlesnake’ (1886). Subsequently called Torpedo Boat Destroyers then simply Destroyers.

Torpedo Gunboat – Gunboat fitted with torpedo tubes.

Torpedo Net – Netting made of interwoven steel wire rings and used as defence against torpedo. Extended almost full length of ship, on both sides, and to a depth of about 20 ft. Disadvantages outweighed advantages when torpedo was fitted with pioneer. Nets were discontinued after 1914-1918 war.

Torpedo Ram – War vessel fitted with a ram, and with torpedo tubes that fired directly forward.

Torque – A rotary force, such as that on a propeller shaft; the turning moment from tangential effort.

Torque Wrench – A wrench designed and to transfer an exact degree of tightness. To prevent thread stripping and comply with manufacturers specifications.

Torricelli’s Theorem – Refers to velocity of water through an orifice. Usually given as SQR 2gh when h is difference of levels on either side of orifice, g being coefficient of gravitational force. Due to frictional and other factors, the practical velocity is about 0.6 of theoretical velocity.

Torrid Zone – That area of Earth’s surface that lies between the Tropics of Cancer and Capricorn.

Torse – A coarse kind of hemp.

Torsion Meter – Instrument for measuring amount of torque in a shaft. Used for measuring torque in propeller shaft turned by a turbine; thus arriving at horsepower of engine.

Total Drift Error (De) – Sum of the individual drift errors from the time of a SAR incident until datum. Used when determining Total Probable Error (E).

Total Eclipse – Eclipse of Sun, or Moon, in which no part of the disc is illuminated.

Total Loss – Used in marine insurance to denote that the subject of insurance has been completely lost, or has been so damaged that it is valueless.

Total Probable Error (E) – The estimated error in a SAR datum position. It is the square root of the sum of the squares of the total drift error, initial position error, and search facility position error.

Touch – To make a brief call at a port or place. 2. To touch the bottom without grounding. 3. Said of a sail when its luff comes into the wind. 4. Tinder or match used for firing muzzle-loading guns.

Touch and Go – To touch the ground, with the keel, for a minute or so and then proceed again.

‘Touch and Stay’ – Inserted in a marine insurance policy to permit vessel to call at a customary port for purposes connected with the voyage. Does not give liberty to deviate.

Touch Hole – Priming hole of a muzzle-loading gun, to which tinder or match was applied for igniting charge.

Touch Off – To fire a muzzle-loading gun by touching the priming with a match or tinder.

Touch the Ground – Temporarily and lightly to make contact with bottom when in shoal water.

Tow – Coarse fibres of hemp that have been separated from the finer fibres. To draw through the water by means of a rope, hawser, or cable. 2. Vessel or craft being towed.

Tow Line, Tow Rope – Rope or hawser by which a vessel is towed.

Towage – The act of towing. 2. Service rendered by towing.

Towage Clause – Clause in a charter party, and repeated in a bill of lading, giving a vessel permission to tow, or to be towed, in stated circumstances.

Towing Becket – Used to attach a towline to a towing bridle.

Towing Bridle – Length of chain. Very often two legged made fast to both quarters of the tug or both bows of the tow.

Towing Horse – An arched transverse beam from bulwark to bulwark in a tug to keep the towrope clear of the deck.

Towing Light – The additional white light shown on foremast of a steam vessel when towing, and a yellow light shown aft.

Trabaccolo – Adriatic cargo vessel or trawler of about 60 tons. Original rig: two masts, lugsails, bowsprit and jibs.

Track – Circular piece of wood fitted on head of an uppermost mast. Generally carries flag halliards, sometimes a wind vane.

Track – Route, in sea or ocean, along which vessels customarily travel. 2. That part of a line of advance that has already been travelled; particularly applied to storms. 3. Disturbed water astern of a vessel. 4. To tow a boat from a tow path.

Track Spacing (S) – In SAR the distance between adjacent parallel search tracks.

Trackage – Towage, particularly from a tow path.

Tracking – Towing, particularly from a tow path.

Trackle – To lower a sail slightly.

Tractive Force – That part of Moon’s gravitational pull that causes the water of Earth to move horizontally towards Moon.

Tractor Propulsion – A system of vertical blades used to propel tugs and ferries, also called a cyclonic system due to the way the blades turn. Related Article: Types of Tugboats and Everything You Need To Know.

Trade Winds – More or less constant winds that ‘tread’ the same path for long periods. They blow from tropical high pressure areas towards the equatorial low-pressure area. Trading Flag. Courtesy Ensign.

Trades – Short name for ‘trade winds’. Also used as denoting the cargo usually carried by a vessel or vessels; e. g. ‘grain trade’, ‘timber trade’—or the areas traded in, such as ‘Baltic trade’,’short sea trade’.

Traffic Separation Zone – A routeing measure to separate the flow of vessels in areas of high traffic density, usually the approaches to busy harbours. Vessels should enter and exit the zones at their termination points.

Trail Boards – Carved boards on either side of a figure head.

Train Tackle – Purchase, from ringbolt in deck to rear end of gun carriage, for holding a broadside muzzle-loading gun while back for loading.

Training Ship – Ship carrying instructors and fitted out for training purposes. The training may be specialised, or general.

Training Wall – Wall, or embankment, erected at sides of a harbour or river to keep the water in predetermined bounds, or to deflect the water into a desired direction.

Trajectory – Used in meteorology to denote the path taken by any particular particle of air when moving over Earth’s surface. In gunnery, is the path of the projectile from gun muzzle to the surface of Earth, or to its bursting position.

Trammel – Fishing net made up of a 40-fathom length of small mesh net between two 40-fathom lengths of large mesh net. Extended between two ropes moored in line of tide, or on bottom in shallow water.

Tramontana – North wind in Mediterranean Sea.

Tramp – Cargo steamer that is not confined to any particular run or to any particular cargo, but carries any cargo that is profitable and convenient.

Tramp Ship – Vessel operating without a fixed itinerary or schedule or charter contract.

Transfer – Distance a vessel moves away from her original line of advance when altering course under helm. Is measured along a line perpendicular to her original course, and to the point where she is on her new course.

Transfer – See advance.

Transient Ship – Name formerly given to a ‘Tramp’.

Transire – The ‘outward clearance’ document of a vessel going from one United Kingdom port to another. Issued by Collector of Customs to Master at loading port. Delivered before discharging, to Collector of Customs at discharging port.

Transit – Passage of a heavenly body across meridian of observer. 2. Passage of an inferior planet across Sun’s disc. 3. In pilotage, the position of two distant, fixed objects when they are in line to an observer; the line passing through them and observer being a position line.

Transom – Name sometimes given to ‘Transom Frame’. 2. One of the thwartship beams bolted to stem post of a wooden vessel. Carries after ends of deck planking and helps to preserve shape of after body. 3. The stern timbers, or plating, of a vessel with a flat stern. As this stem formed the after side of the cabin, the name was sometimes applied to the cabin itself.

Transom Floors – Triangular steel plates rising vertically from upper arch above screw aperture of a single screw ship.

Transom Frame – Strong horizontal girder with its vertical centre line secured to stem post. It takes the cant frames of an elliptical stem and supports the quarters and overhanging stern.

Transom Knee – Knee bolted to transom and after timber.

Transom Stern – Stem consisting of a flat thwartship plate that is approximately vertical.

Transport – To carry from one place to another. Particularly applied to a vessel carrying troops or government stores.

Transporting Line – Rope led from ship to an appropriate place on shore, particularly in a dock or basin, for moving a ship by warping.

Trans-ship – To put out of one ship into another. Often written ‘tranship’.

Transverse – Across a vessel, at right angles to a line drawn from bow to stern.

Transverse Member – Shipbuilding term for a beam, the two frames to which it is attached and the floors at lower ends of frames. If the beam is pillared, the pillar is included.

Transverse Stress – A stress that tends to deform the transverse shape of a vessel or member.

Transverse Thrust – Any thrust that is perpendicular to the normal. Particularly applied to that component of the force exerted by a screw propeller which tends to move the stem side-wise. Its effect is frequently termed ‘paddlewheel effect’.

Trap Boat – A vessel engaged in fishing by baiting and retrieving fish traps, so as to restrict the vessel’s manoeuvrability.

Trapeze – A safety harness and wire that in small fast sailing craft allows the crew to counteract the heel by leaning well overboard.

Trass – Chain confining lower yard to mast. Sometimes is an iron fitting for same purpose, and may be on yard, mast, or both.

Trass Hoop – Iron band, around mast or yard, that is attached to truss.

Traveller – Hoop, ring, or cylinder that can travel freely when encircling a mast, spar, horse, rope, or bar.

Traverse – Zig-zag track of a sailing vessel when plying to windward. 2. A term used in surveying to describe a series of connected lines, of known length and direction, on surface of Earth. If the last line of the series joins the first line, and so encloses a figure, the traverse is termed a ‘closed traverse’. 3. To traverse a yard is to brace it as far aft as possible.

Traverse Board – Circular board marked with points of compass and having holes radiating from centre and towards each compass point. In these holes pegs were inserted, at an appropriate distance from centre, to indicate direction and distance run on the different tacks during a watch, 16th century.

Traverse Sailing – Sailing towards a position by a succession of alternate tacks.

Traverse Table – Table giving lengths of sides of all right-angled triangles when one angle, other than right angle, and one side are given. Included in all nautical tables for determining departure and difference of latitude made good when sailing obliquely to the meridian and distance run is known.

Traverse Wind – Head Wind.

Trawl – A wide-mouthed fishing net dragged along the ocean bottom.

Trawl Warp – Wire rope, leading through a block in gallows, by which a trawl net is towed.

Trawler – A vessel engaged in fishing where its nets restrict the vessel’s manoeuvrability.

Trawling – Dragging a trawl net along the sea bed for the purpose of catching fish. Can only be done in areas where sea bed is fairly smooth and free from obstructions.

Tread – The length of vessel’s keel.

Treble Block – Block having three sheaves on the same pin.

Tree – Wooden beam, or bar, used in the furniture of a ship. Usually qualified by a word giving its particular function or description; e. g. crosstree, rough tree, chess tree, trestle tree, waist tree, etc.

Treenail – Cylindrical length of wood, from one to two inches in diameter, used for securing planking to frames, and other purposes, in wood-built vessels.

Trekschuyt – Covered boat formerly used in Holland and Flanders for transporting goods and passengers. Was towed by horses or oxen.

Trend – The increase in girth of an Admiralty pattern anchor shank as it approaches the arms. Extends for a distance equal to that of arms. 2. Angle between a vessel’s fore and aft line and the cable to which she is riding.

Trennels – Tree-nails.

Trestle Trees – Brackets, of wood or steel, on either side of lower mast, to support a top. With wooden masts, they rest on hounds. In modern ships they are riveted to steel mast, and support the fid on which heel of topmast rests.

Triage – The process of sorting survivors according to medical condition and assigning them priorities for emergency care, treatment, and evacuation.

Trial Trip – Short voyage of a newly-built, or repaired, vessel to test engines, steering, and other machinery, and to ascertain ship’s capabilities and deficiencies. Trials.

Triangle Knot – Made in bight of rope so that two firm loops are formed. Not used in practical work, but is of interest as being a ceremonial knot of Brahmins.

Triangulation – Method used in surveys. Distance between two stations being known accurately, the distance of another station can be computed trigonometrically from the angles between it and each of the other stations.

Triangulum Australe – ‘Southern triangle.’ Well-marked stellar triangle about halfway between Scorpio and south pole. R. A. 16h; Dec. 69°S (approx.).

Triatic Stay – Stay going horizontally from cap of one mast to cap of next mast. Common in vessels fore and aft rigged. Sometimes called ‘jumper stay’.

Tributary – A smaller river that joins a larger.

Trice – To haul up by pulling downwards on a rope that is led through a block or sheave.

Tricing Line – Any small rope used for tricing; particularly that led through block at jaws of gaff to tack of a gaffsail.

Trick – A turn of duty at the steering wheel (usually up to two hours). See Also: How to Steer a Ship and Become a Better Helmsman.

Trident – Three pronged spear of Roman and Greek Sea Gods Neptune and Poseidon.

Trident Log – Towed log, on ‘Cherub’ principle, that has an electrical unit for repeating the indications at a point distant from log.

Triemiolio – Light, fast vessel of Rhodes in classic times.

Trim – Difference, or relationship, between the forward and after draughts of a floating vessel. Ship is said to be trimmed by the head or stem according to which end is deeper in the water.

Trim Indicator – Instrument for measuring and indicating the longitudinal inclination of a vessel.

Trimaran – A vessel having three hulls, the central one usually being the largest.

Trimmer – Man who shovels bulk cargo, particularly coal, from hatchway to the wings and under deck spaces in a hold. 2. Man who shovels coal from bunker to a position nearer to stokehold.

Trimming – Adjusting. Applied to cargo, denotes placing it in its proper position and, if necessary, winging it out. Applied to a vessel, denotes placing and arranging cargo so that there is a desired relationship between the forward and after draughts. Trimming a bunker is passing the coal in it to another bunker, or to a position where it will be handy for feeding fires.Trimming yards and sails is carefully adjusting them so that the maximum wind effect is obtained.

Trip – Voyage. To release. To raise an anchor clear of the bottom. To release a spring-loaded snap-shackle.

Tripod Mast – Steel mast consisting of three members whose heels are spaced as a triangle, and whose heads meet and are secured together. No stay or shrouds are required. First used in H. M. S. ‘Captain’ (1870); but the idea is much older, and is to be noted in many small craft all over the world.

Tripping – Breaking an anchor out of the ground. 2. Said of a boom when its outboard end skims the water. 3. Raising the heel of an upper mast.

Tripping Line – In general, a line that stops a particular item from doing its work. On a sea anchor, it capsizes the anchor and is used for hauling it in; on the clew of a sail, it hauls it up and spills the wind out of the sail. On heel of an upper mast, it lifts the mast and takes the weight off the pin or pawl.

Tripping Palm – More or less flat projection on arm of a self-canting anchor. Its duty is to bite into the ground and ensure that the nukes turn downward to bite into the ground. Related Article: Parts of an Anchor and Its Windlass Arrangement.

Triquetrum – Ancient navigational instrument for measuring altitude of Sun. Consisted of two pieces of timber hinged at ends. One leg was kept in horizontal plane, the other was pointed to Sun.

Trireme – Ancient war vessel of Carthaginians, Greeks, and Romans. Had three tiers, or banks, of oars. Greek equivalent was the Trieres.

Triton – Greek sea god, son of Neptune.

Trochoid – Curve that would be made in the vertical plane of a point in a circle that is rolling on a horizontal plane. Is of much importance when considering motions of free waves of the sea.

Troll – To fish by drawing bait through the water.

Troop Ship – Vessel fitted for carrying troops and their equipment. A transport.

Trooper – Troop ship. Transport.

Trooping – Royal Naval term for carrying relief crews for vessels on foreign stations, and for bringing back the crews relieved. 2. Carrying troops by sea.

Tropic of Cancer – Parallel of latitude, or declination, 23° 27′ N, being the highest parallel reached by Sun in his northerly motion. Reached about June 21.

Tropic of Capricorn – Parallel of latitude, or declination, 23° 27’S, being the highest parallel reached by Sun in his southern motion. Reached about December 21.

Tropic Tides – Diurnal tides whose amplitudes vary with the declinational values of the tide-raising bodies—Sun and Moon.

Tropical Air – Air that has travelled from low latitudes to high latitudes.

Tropical Cyclone – Meteorological depression originating in low latitudes. Tropical revolving storm. An area of intense low pressure which form over tropical waters, usually in the summer.

Tropical Month – Interval between successive transits of Moon through the same point in Ecliptic. Value is 29 d 12h 43.075 m.

Tropical Year – Time taken by Earth to go round Ecliptic from First Point of Aries. As First Point of Aries has a variable retrograde motion (about 50. 26″ annually), Earth does not complete a sidereal revolution. Length is aboutd 05 h 48 m 48 s, but this varies slightly.

Tropics – The tropics of Cancer and Capricorn. The area of Earth between the tropics.

Tropopause – Boundary between the troposphere and stratosphere.

Troposphere – The atmospheric shell in which we live. Extends upwards to a height of about 10 miles in the tropics, about seven miles in temperate latitudes, perhaps, five miles at poles. Temperature decreases, more or less uniformly, with heights. Winds are not constant, rain can be precipitated.

Trot – Line of mooring buoys laid out at regular intervals. 2. Line of fishing hooks laid out at regular intervals when “bottom fishing’.

Trough – Hollow between two waves in water. 2. Area of lowest barometric pressure in a cyclonic storm, lying perpendicularly— more or less—to direction of travel of the storm.

Trucks – Large wooden beads through which jaw rope of a gaff is rove. They reduce friction on mast when gaff is lowered or hoisted. 2. The small wheels of a wooden gun-carriage.

True – Word used when denoting values from which known errors have been eliminated. Used in this sense we have “true altitude’, ‘true course’, “true azimuth’, etc. Also used when differentiating between similar entities in different forms, such as “true’, and ‘mean’ Suns, ‘true’ and ‘magnetic’ north, etc.

True Altitude – Angular value of arc of vertical circle intercepted between a heavenly body and rational horizon. Deduced from apparent altitude by application of corrections for refraction, parallax and dip.

True Azimuth – Angular distance of a heavenly body from observer’s meridian. Measured from the elevated pole.

True Bearing – Angle between observer’s meridian and the great circle passing through observer and object observed. Expressed in three-figure notation, or quadrantally.

True Course – The vessel is steering is the angle between true north and the vessel’s head. The true bearing of any object from the vessel, is the angle between true north and the line joining the vessel to the object.

True Distance – Length of arc of great circle intercepted between two points on Earth.

True Lay Wire – Wire rope in which each wire is shaped in the spiral form it must have in the rope — and is not twisted into this shape. Pre-formed.

True Sun – The apparent, or actual, Sun as distinguished from mean, and other, suns.

Trundle Head – That upper part of a capstan which contains the sockets into which the capstan bars are shipped.

Trunk – Rectangular space bounded by vertical plating and capable of being closed on upper side. Lower side is generally open to a larger enclosed space.

Trunk Cabin – A cabin supported clear of the deck by a raised (trunk) housing around the deck opening.

Trunk Ship – Vessel having trunks at deck level to act as feeders to holds.

Try – To lie to under storm canvas, reduced sail, or even, bare poles.

Trysail – Fore and aft sail, set to a gaff, used when lying to in heavy weather, or when sailing on a wind.

Trysail Gaff – Gaff to which head of trysail is extended.

Trysail Mast – Small mast formerly carried slightly abaft principal mast, to take a trysail.

Tsunami – Wave generated by an under-water upheaval of the earth’s crust. Can travel great distances and cause destruction on arrival at a coast. Improperly called a tidal wave.

Tube Nest Cooler – A water cooling system where fresh sea water passes through internal tubing, cooling hot engine water that flows around the tubing.

Tube Plates – Perforated plates in combustion chamber and front end of marine boiler. They take front ends of smoke return tubes, which are fitted between them.

Tubinares – Means ‘Tubular nostrils.’ Applied to petrels, in which this characteristic is pronounced.

Tuck – After part of a vessel, where bottom planking comes to the counter.

Tuck a Strand – To pass end of one strand under an unlaid strand when splicing. Colloquially: to gain an advantage, or favourable notice.

Tuck Rail – Lower strake of horizontal timber in counter of a wooden vessel.

Tufa – Light porous stone, rather like sandstone, that sometimes contains vegetable matter.

Tuft – Short piece of wool attached to the surface of a sail as an indicator for steering to windward, and to trim, on all points of sailing.

Tugboat – A small tug. A small vessel used to tow or push large ships or barges. Related Article: Types of Tugboats and Everything You Need To Know.

Tumble Home – The inward inclination of a vessel’s sides due to her breadth at upper deck being less than her maximum breadth.

Tumbler – Hinged pin on which end link of chain holding an anchor is placed. When shaft—on which pin is fixed—rotates, the link falls off and anchor is released.

Tumbler Bolt – Device used for making good a missing rivet, and other purposes, when outside of plating is inaccessible. Works on the principle of a toggle.

Tun – Large cask holding 252 gallons (four hogsheads) of wine. 2. Wine measure of same quantity.

Tunnage – Duties levied on every tun of wine, and pound of goods, shipped from or to England. Introduced about 1348. Was the beginning of the present Customs duties.

Tunnel – Arched casing around propeller shafting. Extends upwards in after holds of cargo vessels with engines amidships. Goes to stem gland and allows access to propeller shaft bearings.

Tunnel Escape – Vertical ladder from after end of tunnel for emergency use.

Tupaia – Tahitian navigator taken aboard to provide pilotage for Captain James Cook’s voyage of discovery of the South Seas, New Zealand and the Australian East Coast.

Turbine – Machine in which rotary motion is produced by high velocity of a fluid acting on blades appropriately mounted in its path. Can be divided into two types, ‘impulse’ and ‘reaction’. Broadly stated, an impulse turbine in same manner as an undershot water mill; reaction turbine being turned on same principle as a windmill. Marine turbines are steam or (petroleum) gas driven. The latter needing no boilers.

Turbo Charger – The blades of a turbine in the outlet exhaust flow of an engine are driven by the gases flowing over them. Compressor blades at the other end of the same axle are spun in the inlet flow, drawing large volumes of air into the cylinders. This enables faster combustion than naturally aspirated engines and increases power of the engine.

Turbulence – Disturbed, or eddying, movement of any fluid when passing over any obstruction—solid, liquid, or gaseous—in its path. Is of importance in meteorology.

Turk’s Head – Knot put in end of rope by unlaying strands, making a ‘wall’ and crowning it, then following through twice. Can be made with a single line. Resembles a turban in appearance.

Turn – Complete encirclement of a cleat, bollard, or pin by a rope.

‘Turn’ – Order given to man holding sand-glass when heaving the (hand) log and stray line is out. He then turns glass so that sand runs down, and reports, ‘Done’.

Turn Buckle – Stretching screw; bottle screw.

Turn to – Commence work.

Turn Turtle – To turn over completely, with keel uppermost. To capsize.

Turn Up – To fasten a rope securely by taking turns around a cleat or bollard.

Turn-around – The time a vessel stands in a port.

Turnbuckle – A device that applies tension to ropes or wires by the use of opposing screw threaded terminals, tapped into a central frame.

Turned Knee – Beam knee made by curving bar to shape required.

Turner’s Reefing Gear – Single-handed gear for yachts. Main boom is on an axis, and can be rotated by a lever and pawl acting on a ratchet wheel near heel of boom. Thus causes sail to be rolled up around the boom.

Turning Centre – That point on which a vessel turns when under helm. Any point forward of this will turn in a direction opposite to that of any point abaft it. In most vessels of normal form this point lies between 0.3 and 0.4 of vessel’s length from forward but much depends on trim.

Turning Circle –. Circle whose diameter is the distance from the point at which helm is put over and the point where direction of ship’s head has changed 180°, or 16 points. It varies with speed, draught, trim, and amount of helm.

Turpentine – Oily Australian timber used for pilings as it is very durable against teredo infestation.

Turret Deck Type – Applied to a vessel constructed on a principle introduced by Doxford, of Sunderland. Side plating curves over to form a harbour deck, and then upwards again to form a ‘trunk’ or ‘turret’. Ships of this type are practically self-trimming. Hold pillaring is either very small, or entirely absent. Web frames are used for maintaining strength and form.

Turret Ship – Warship carrying main armament in a turret or turrets. 2. Vessel of turret deck type.

TVMDC – True-Variation-Magnetic-Deviation-Compass.

Tween Decks – The space between any continuous decks.

Twelfths Rule – Finding the approximate amount the tide will fall in a certain time.

Twenty-foot Equivalent Unit  Unit for a standard container of 20 ft long x 8 ft wide x 8.5 ft high; (6050 x 2440 x 2590 mm).

Twice Laid – Rope made from good yams taken from old ropes.

Twiddling Line – Small line made fast near hand wheel of a sailing vessel and passed round a spoke of the wheel to ease strain on arms of helmsman. Particularly useful when vessel makes stem-way. 2. Small line rove through sheaves of a yoke, the end being made fast in boat, to form a purchase for yoke lines when steering. 3. Name given to the ‘twitching line’ of old magnetic compasses of large diameter. These cards were sluggish in action. A small piece of sail-maker’s twine was made fast to card, usually with beeswax, so that helmsman could give card a twitch if it appeared to be dead.

Twig – To swig. To sweat up on a rope.

Twilight – Partial illumination by sunlight during interval between Sun’s upper limb being on horizon and his centre being 18° below it. Caused by the scattering, refraction, and reflection of light by  earth’s atmosphere. Period of time before sunrise and after sunset when some light remains. See ‘Civil’, ‘Nautical’, and ‘Astronomical’ twilights.

Twilight Arch – Upper boundary of a slightly illuminated tract of sky when Sun is below visible horizon.

Twilight Stars – Stars suitably placed for observation during mom-ing or evening twilight.

Twin  – Said of a vessel having two propellers.

Twin Propellers – Twin screws.

Twin Screws – Pair of screw propellers, one on either side, which rotate in opposite directions when propelling a vessel. Introduced in 1888. May be inturning or out-turning.

Twine – String thread used for sewing and whipping.

Twine – Two or more threads twisted together to make a small line. 2. The linen thread with which canvas is sewn.

Twist Knot – Plait knot.

Twitching Line – See ‘Twiddling Line’.

Two Blocks – Said of a purchase or tackle when it has been hauled upon until its two blocks are touching one another.

Two-Stroke Cycle – Charging and compression on one stroke, ignition and scavenging on second stroke, of an internal combustion engine.

Two-Stroke Engine – Internal combustion engine having a power impulse on alternate strokes.

Tye – Rope by which a yard is hoisted. Usually rove through a sheave on mast.

Tye Block – Special iron-bound block shackled to a yard. Tye is rove through it to obtain extra purchase.

Typhoon – Violent cyclonic storm prevalent in seas around China, Japan, and the Philippine Islands.Tyzack Rail Bar – Rolled section used as gunwale capping. Comprises a flat rail with bulb on lower side of one edge, other edge having flat strip at right angles to bar—this strip being drilled with holes for riveting to bulwark plating at upper edge.

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