G.M. – The initial transverse metacentric height, measured in metres from the ships centre of gravity to its metacentre. A large GM indicates a stiff ship.
G.Z. – The length of the righting arm in ship stability calculation.
Gacrux – Star γ Crucis. S. H. A. 173°; Dec. S57°; Mag. 1.6.
Gaff – Spar, having jaw that fits round mast, and to which the head of a gaff sail or trysail is attached and extended.
Gaff Topsail – Small triangular sail having its foot extended along gaff, and its luff along mast.
Gage – Old name for a vessel’s draught in water. Also, her position relative to wind and another vessel.
Gain – Radio wave amplification.
Galactic – Pertaining to the Galaxy or ‘Milky Way’.
Galaxy – The ‘Milky Way’.
Gale – A strong wind. Formerly applied to any fresh wind; now usually denotes wind of force 8 and above. Wind blowing at over 34 knots and up to 47 knots.
Gale Warning – Notice of an impending gale. May be given by radio, visual signal, telegram, or other means.
Galilean Glasses – Optical aid consisting of two tubes, each with a double concave eyepiece and double convex object glass.
Galiot – Galley with one mast and 16 rowing benches. Most popular vessel of ancient times.
Galizabra – Spanish 16th century race built galleon used as treasure transport ships from the Spanish New World.
Gallant – Former name for ‘topgallant’.
Galleass – A 17th century oared and masted vessel with lateen sails.A Baltic trading schooner.
Galleon – Spanish or Portuguese 16th century large and highly decorated merchantman or warship. Used as treasure transport ships from the Spanish New World.
Gallery – Projecting walk, or balcony, at stern or quarters of old sailing ships.
Gallery Built – Name given to a flush-decked sailing vessel.
Galley – Compartment in which cooking and other food preparation is done in ships. A vessel’s kitchen. Historically a many oared fighting vessel.
Galley Foist – State barge used on ceremonial occasions. Galley Wireless. The source of all rumours in a Merchant ship.
Galliot – Bluff-bowed, two-masted trading vessel formerly used by Dutch. Usually rigged as a topsail schooner. Shallow draught; leeboards.
Gallivat – Swift sailing craft of about 70 tons, formerly used on Malabar coast. Had two masts, lateen sails and was armed with small swivel guns.
Gallon’s Sun Signal – ‘Heliostat.’
Gallows – Horseshoe-shaped girder, hinged on deck of trawler. Carries block through which trawl warp is led. 2. Support for a boom when sail is lowered and furled.
Gallows Bitts – Vertical framework fitted on deck to take stowage of spare spars and timbers.
Gallows Stanchions – ‘Gallows Bitts.’
Gallows Top – Cross timbers at upper end of gallows bitts.
Galvanic Scale – The relative electrical activity of differing metals within an electrolyte. Some, being noble will resist corrosion, but others are less noble and more likely to corrode.
Galvanizing – The process of hot or cold surface coating a metal with a zinc film in order to increase its resistance to corrosion.
Galway Hooker – An esteemed but coarsely built small Irish sailing cutter.
Gam – Visit between whalemen when on whaling ground.
Gambling Policy – Uncomplimentary, and usually unjustified, name for a policy issued without proof of interest having been given.
Gammon – To lash heel of bowsprit in place.
Gammon (Gammoning) Iron – Iron band clamping bowsprit to stem.
Gammon Plate – Iron plate, bolted to stem head, carrying a ring through which gammoning is passed.
Gammon Shackle – Ring, on gammon plate, to which gammoning is secured.
Gammoning – Securing lashings for the inboard end of a bow sprit.
Gammoning Hole – Hole, near or in stem, through which turns of gammoning are passed.
Gang Casks – Small casks used for bringing off water from shore to ship.
Gangboard – Plank bridge from quay or wharf to ship. Usually fenced.
Ganger – Cable between hawse pipe and a sheet anchor that is stowed on an anchor bed.
Gangway – Entrance into a ship at head of accommodation ladder. Steel or wooden bridge connecting ship with shore, or with another vessel. 2. A clear path along which men can walk.
Gannet – Sea bird of which the principal type is the ‘Solan Goose’.
Gantline – A line rove through a block near the masthead used to hoist anything aloft.
Gantry – An above deck structure typically supporting a lifting apparatus.
Garboard Strake – The first planks on each side of the keel.
Garland – Rope or selvagee circle, carrying additional strops, placed round head of mast when taking it in and stepping it. Temporary stays, shrouds and guys are made fast to the strops. 2. Rope put round mast, under eyes of rigging, to protect mast and rigging from chafe. 3. Rope grommet put under round shot to prevent rolling. 4. Mesh bag for holding vegetables, mess cleaning gear, etc. 5. Circle of evergreens hoisted at triatic stay on wedding day of an officer of the ship. 6. Wreath of green leaves surrounding shield in centre of Union flag flown by military officers commanding a station, diplomatic servants and Governors or High Commissioners of British colonies.
Garnet – Purchase, on main stay, for hoisting purposes. Also, applied to other purchases, such as ‘clew garnet’.
Garofali – Whirlpools in straits of Messina.
Garvey – A hard chine hull in which the chines do not join on the stem centreline.
Gas Buoy – Navigational buoy carrying a light.
Gas Carrier – A ship designed for the transport of liquefied gases.
Gas Free – A space tested by a gas detector as not containing any hazardous gases or residues.
Gas-Freeing – Removing pockets of gas from compartments of an oil-carrying vessel after cargo has been discharged.
Gasket – Length of sennit fitted for securing sail when furling. 2. Grommet or packing in a gland or pipe joint.
Gat – Navigable waterway between shoals.
Gather Way – To start to move through water with increasing speed.
Gauge – A marine marker that displays the changing level of the sea water by increments.
Gaussian Logarithms – Tabulated values that facilitate the subtraction or addition of quantities when expressed in logarithmic form.
Gaussin Error – Temporary compass error when changing course. Due to time lag in adjustment of sub-permanent magnetism to ship’s new heading.
Gear – Rigging, tackle, fittings, implements, equipment, tools or essential parts.
Gear Case – A housing for the gear train of a motor.
Gearbox – A system of gears which alter the ratio between the revolution of the engine and the propeller shaft. By using a gearbox the engine and the propeller shaft will revolve at different speeds
Geared Turbine – Turbine in which high rotor speed is reduced, before reaching propeller, by reduction gearing; thus allowing turbine to run at high speed and propeller at a lower but more effective speed; so reducing cavitation at propeller.
Gearing – Arrangement of pinions or wheels by which motion may be transmitted, or speed reduced to give more power, or power reduced to give increased speed.
Gel Coat – The surface resin coating of a fibreglass lay-up, containing the colour pigment.
Gel Time – The delay for a resin to solidify after the catalyst has been added.
Gelves – Oriental sailing craft of 16th century. Had one or two masts.
Gemini (The Twins) – Constellation situated between R. A.’s 05 h 40 m and 07 h 40 m (about) and Declination 12° to 32°N. Has three navigational stars. Castor (α), Pollux (β), Alhena (γ). Also, third sign of Zodiac, extending from 60° to 90° celestial longitude. Sun is in this sign from May 21 to June 21 (about).
Gemma – Star α Coronae Borealis.
General Arrangement – A detailed naval architects plan of the layout of a vessel.
General Average – General indemnity made by all interests concerned—and in proportion to the financial value of property each had at stake—for a maritime loss deliberately but reasonably incurred for the safety of the remaining property when in peril.
General Average Act – Voluntary and extraordinary action reasonably taken for preserving property in peril.
General Average Expenditure – Extraordinary expenditure voluntarily and reasonably incurred for preserving property in peril.
General Average Loss – Loss that is due to a general average act or expenditure.
General Average Sacrifice – Deliberate and extraordinary sacrifice reasonably made for preservation of property in peril.
General Cargo – Cargo made up of different commodities.
General Equation – Alternative name for ‘Fundamental Formula’.
General Purpose Rating – A rating who signs-on to work on deck or in the engine room as required.
General Service Pump – GS Pump. A pump that can be used for several purposes. Can feed donkey boiler, provide deck salt water service, supply fresh water to drinking tanks. Cannot pump bilges.
Genoa – A large, overlapping fore sail.
Genoa Jib – Large jib used in yachts. Sheets home well abaft mast. Very effective in light winds.
Geocentric Latitude – Angle at centre of Earth between plane of Equator and a radius of Earth going to any position on surface.
Geocentric Longitude – Angular value at centre of Earth, of arc of Ecliptic intersected between First Point of Aries and a secondary circle passing through a heavenly body. Measured eastwards.
Geocentric Parallax – ‘Diurnal Parrallax’.
Geodetic Datum – A European and North American uniform system of reference of latitude and longitude for setting out and drawing charts.
Geographic Position – A vessels latitude and longitude, or the position of a celestial body directly overhead expressed in declination and Greenwich hour angle (GHA).
Geographical Latitude – Angle between plane of Equator and a perpendicular passing downward from a given point on Earth’s surface. Owing to Earth’s spheroidal shape, this angle will not be at centre of Earth unless latitude is 0° or 90°.
Geographical Mile – Length of one minute of arc of Equator. Value is 6087.2 feet.
Geographical Position of Heavenly Body – Latitude and longitude of a point on Earth’s surface at which a given heavenly body would be in the zenith.
Geo-Navigation – A type of navigation proposed, by J. B. Harbord, for methods of conducting a ship, or fixing her position, by geographical observations.
Geordie – Nickname given to brigs formerly used in Tyne coal trade and the men who manned them.
Geostrophic – Meteorological term for Earth’s rotational effect on wind. Deflection of wind caused by this is termed the ‘geo- strophic component’.
Geostrophic Wind – The wind flowing parallel to straight isobars, where the Pressure Gradient force and Coriolis force are balanced.
German Eye Splice – Made in a rope by tucking first strand with lay, second strand tucked under same strand, but against the lay, third strand tucked as usual.
Ghosting – Sailing slowly in light wind.
Gib – Projecting arm of a crane; a jib. 2. Forelock of a shackle. 3. Wedge-shaped piece of metal used for transmitting thrust to a collar, or inclined surface.
Gibbous – Applied to Moon’s phase after her second quarter and when her disc is more than a semi-circle but less than a circle. Also applied to inferior planets and Mars, who take this form at times.
Gienah – Star γ Corvi. S. H. A. 177°; Dec. S17°; Mag. 2.8. Gift Rope. Guess Warp. 2. Additional line given to a boat when towed.
Gig – Single-banked rowing boat pulling four, five or six oars and about 25 to 30 feet long. A small, oared, fast ship’s boat.
Gilguy – An object for which the correct name is forgotten.
Gill – The respiratory organ of fishes.
Gill Net – A fishing net that catches fish by their gills.
Gilliwatte – Name given to Captain’s boat in 17th century.
Gimbals – Two rings, pivoted at right angles to each other, which keep a compass or chronometer in horizontal plane in all circumstances.
Gimletting – Turning an anchor by moving stock through a circle, with shank as axis.
Gin – Hoisting apparatus consisting of a barrel mounted in bearings and turned by a crank.
Gin Block – Name given to metal pulley blocks, particularly those with skeleton frames.
Gin Tackle – Purchase made by reeving rope through double and treble blocks.
Gingerbread – Decorated scroll work, usually gilded, around stem and quarters of olden ships.
Gipsy – The sprocketted cable holder of a windlass.
Girder – In steel construction, a term for a heavy duty fore and aft placed strengthener.
Girder Strength – Resistance offered by any member, or construction, to deformation of its longitudinal axis.
Girding – Binding. Passing frapping lines.
Girdle – A binding passed round an object.
Girt – Said of a vessel having two cables out and so taut that she cannot swing. 2. The condition of a tug when her towrope leads abeam or before the beam and the stress on it causes danger of capsizing.
Girth – The distance measured on any frame line, from the intersection of the upper deck beam end around the body of the vessel to the corresponding point on the opposite side. The half girth is from the keel centre line to upper deck beam end.
Girth Band – Strengthened strip stitched from clew to luff of jib or staysail.
Give Way – Order given to boat’s crew to commence rowing. If already rowing, is an order to put extra weight on oars.
Give Way Vessel – A term used to describe the vessel which must yield in meeting, crossing, or overtaking situations.
Glacial – Applied to deposits, sands and gravels that are out-wash of glacier sheets.
Glacier – A slowly moving river of ice formed from the accumulation of years of previous snow falls on the mountains above.
Glass – Name commonly given to a barometer. 2. German name for a telescope, which was, formerly, called a ‘perspective glass’. 3. Sand glass for measuring intervals of time. Two of these were used with the ‘ship log’; one measuring 14 seconds, the short glass; the other, the long glass, measuring 28 seconds. Before the introduction of clocks, the watches on board were regulated by sand glasses taking half an hour to empty; the bell being struck each time the glass was turned. Intervals of time at sea were measured in ‘glasses’ up to end of 18th century.
Glass Fibre – Glass spun into fine flexible threads that can be chopped strand mat or woven. The glass mats are formed in a mould and solidified by the addition of a resin. The process is called Glass Reinforced Plastic (polyester), GRP.
Glasses – Binoculars.
Glazed Frost – Rain that freezes when surface temperature is below freezing point.
Global Maritime Distress and Safety System GMDSS – a Convention of the IMO. A global communications service based upon automated systems, both satellite-based and terrestrial, to provide distress alerting and promulgation of maritime safety information for mariners.
Global Navigation Satellite System GNSS – Worldwide position and time determination system that includes one or more satellite constellations and receivers.
Global Radiation – Short wave radiation reaching the ground from the sun and scattered downwards by clouds, dust particles etc.
Globigerina Ooze – Chalky, light-coloured mud found at about 3000 fathoms in Atlantic Ocean mainly composed of decomposed shells of globigerina and other Crustacea and mollusks.
Gloomy – Applied to weather that is dark, lowering and dismal.
Glory Hole – Any small enclosed space in which unwanted items are stowed when clearing up decks. 2. Steward’s accommodation.
Glut – Doubling piece at centre of head of a square sail. Has a hole into which is passed becket of bunt jigger.
Gnomon – Perpendicular rod, or pillar, formerly used for measuring altitude. 2. The stylus of a sundial.
Gnomonic Chart – Chart constructed by gnomonic projection. All British Admiralty charts on scale of 1/50, 000 or smaller are gnomonic. Charts of polar area are nearly always gnomonic.
Gnomonic Projection – Projection of Earth’s surface on a plane that is tangent to surface at a given spot, and by lines from centre of Earth. Advantages are (1) So long as area is small there is no appreciable distortion: (2) projection of great circles are straight lines: (3) there is little distortion in polar regions. Its disadvantage is that scale is not constant; areas away from point of tangency are distorted.
Go About – To go from one tack to the other, when under sail, by putting ship’s head through the wind.
Go Ahead – To move forward through the water. 2. To take station ahead of another vessel.
Go Astern – To reverse engines so that vessel moves stern first. To move through water stern first. To take station astern of another vessel.
Go by the Board – Said of a mast that breaks close to the deck.
Goal Poster – Nickname given to a vessel having a rectangular girder structure athwart upper deck to support derricks. Stump mast is usually stepped in middle line of transverse girder.
Gob Line – Back rope of a martingale. 2. A length of rope used in a tug to bowse in the towrope. Gog Rope.
Godfray’s Azimuth Diagram – Devised by Hugh Godfray to facilitate the finding of true azimuth from own latitude, apparent time, and declination of observed heavenly body.
Godown – Oriental name for a storehouse or warehouse.
Goes Adrift – To break loose.
Gog Rope – Gobrope.
Going Free – Sailing with wind abaft the beam.
Going Large – Sailing with wind abaft the beam.
Golden Number – Every 19 years Moon goes through her changes on different dates, and then repeats them on these dates; this is called the ‘Lunar Cycle’ and was adopted in 433 B. C. The Golden Number of any year is the number it is in the Lunar Cycle. To find it: Add 1 to the year A. D. and divide by 19. The remainder, up to and including 19, is the Golden Number. Gold Slide. Adjustable attachment to a mercurial barometer for giving resultant of corrections for index error, height of instrument above sea level, variation in gravity due to latitude, temperature. Correction is read from a scale alongside a small thermometer, and is noted before reading barometer. Invented by Col. E. Gold, D. S. O., F. R. S.
Gondola – Venetian boat rowed with one oar. Has a cabin amidships and an extended and ornamental stem piece.
Gondolo – Ship’s Longboat of the 16th century.
Gonies – Albatrosses.
Goods – Articles that are bought and sold.
Goole Fender – Fender placed across stem of vessels moving in Goole docks to prevent damage to low dock sills.
Gooseneck – Projecting iron fitting with ring or band at its outer extremity. Used for studdingsail yards and similar purposes. 2. Iron that connects end of a spar or boom with its pivot.
Goosewing – Course or topsail with weather clew hauled out, lee clew hauled up and buntlines taut reduces to less than half the sail. 2. A studding sail. 3. Wing and wing in a schooner with booms on alternate sides.
Gopher Wood – Timber used for building Noah’s ark. Probably cypress wood.
Gore – ‘Goring Cloth.’
Gore Strake – Strake that tapers to a point before reaching stern.
Gorge – Aperture, in a wood block, through which rope is rove. More usually called ‘swallow’. A narrow steep sided valley.
Goring – Said of a sail that increases in width downwards.
Goring Cloth – Side cloth of a topsail. Has oblique edge, at side, to increase width of foot.
Gottlieb’s Log – Submerged log fitted near keel in early 19th century. Way of ship caused a wheel to turn, and so actuate registering mechanism inside ship.
Gouge – A rounded chisel.
Grab – Steel bucket consisting of two hinged parts which are open when lowered but closed when weight is taken for hoisting. Used when discharging, or loading, fluid cargoes such as shingle, coal, grain, etc.
Grab Lines – Becketted line around outside of a lifeboat. Fitted for men in water to grasp them.
Grab Rail – Protruding rail around sides of a deck house fitted for grasping in heavy weather.
Grab Ratline – Taut wire stretched just above rim of lower tops. Placed to assist men going aloft by futtock rigging.
Gradient – Rise or fall of barometric pressure as related to distance. Said to be ‘steep’ when pressure changes quickly with change of position; ‘low’ when it changes slowly.
Gradient Wind – A wind curving across isobars due to imbalance between the pressure gradient force and Coriolis forces.
Graduated Meridian – Meridian, on a Mercator chart, graduated for the measurement of distance. Is generally in chart border, but may be a central meridian.
Graduated Parallel – Parallel of latitude, on a Mercator chart, graduated for measuring Mercatorial distance and determining longitude. Usually in upper and lower borders, but may be along a central parallel.
Graduations – Series of marks, or lines, for facilitating measurements.
Graft – Decorative finish to an eye splice in rope. A certain number of yarns from ends of tucked strands are left out, the other yarns being tapered and marled to rope. Over the marled yarns the other yarns are woven—the yarns forming the warp, sailmaker’s twine being used for weft.
Grafting – Making a graft around a rope.
Grain – Defined as ‘any corn, rice, paddy, pulse, seeds, nuts, or nut kernels’. 2. The water ahead of a ship, and through which she will pass. Opposite of ‘Wake’.
Grain Certificate – Document giving particulars of a vessel loading grain, her draught and freeboard when loaded, quantity and kind of grain, method of stowing and measures taken to prevent shifting.
Grain Laden – Technically, applied to a vessel carrying an amount of grain equivalent in weight to two-thirds of her registered tonnage; or bulk equal to 100 cubic feet for each registered ton.
Grain Space – Internal volume of all holds in a ship. Measured from tank top to underside of deck, and from ship’s side to ship’s side in holds.
Grains – Harpoon with four barbs and 5-ft. wooden handle.
Grampus – Large mammal, of the porpoise family, about 20 feet long. Met with in North Atlantic ocean.
Grampussing – Old-time punishment for a man found asleep on watch. His arms were triced up by rope and two buckets of water were poured down his sleeves.
Granny (Knot) – An improperly tied knot, similar to a reef knot.
Grape Shot – Cannon balls with diameter rather less than half the calibre of the gun firing them. Formed into a cylindrical shape when loaded but which fly apart when fired.
Grapnel – An anchor with many claws. Used for hooking a submerged cable or wire. Formerly used for making attachment to a vessel so that she could be boarded. 2. Rope attached to a boat’s anchor for riding by.
Grappling Iron – Grapnel when used for laying hold of a ship, or other floating body.
Grass Line – Coir hawser.
Graticule – From same root as ‘Grating’. Network made on chart by lines of latitude and longitude.
Grating – A perforated covering plate. Used to cover hatches in good weather, to let in light and air or provide a non slip deck surface.
Grave – To clean a vessel’s bottom by burning off the fouling.
Graveyard Watch – The middle watch, midnight to 4 a. m.
Graving – To scrape down the hull of a vessel.
Graving Dock – A dry dock. Originally, a dock in which a vessel’s bottom was cleaned by burning off the fouling.
Graving Piece – Small piece of wood let into a plank having a small defect.
Greaser – Engine-room rating whose duty is to attend to lubrication.
Great Circle – Circle of sphere whose plane passes through centre of sphere. All great circles of a sphere have a common centre, and each great circle bisects all other great circles.
Great circle route: The shortest course between two points on the surface of a sphere.
Great Circle Sailing – The sailing of a ship between two positions when her course is along a great circle of Earth. Her head is continuously kept pointing to her destination by frequent adjustments of course—except when sailingalong Equator or a meridian.
Great Circle Track – Arc of gre at circle, on surface of Earth, between two given positions. Is line of shortest distance between these positions.
Greave – To ‘Grave’.
Grecian Splice – Neat and strong splice often used for splicing standing rigging that had parted. Each end is unlaid to a whipping. Heart yams of each end are laid up into three small strands, and spliced. Remainder of yarns are laid up into foxes and cross pointed over splice.
Greek Fire – ‘Wildfire.’
Greek Winds – See classical winds.
Green Flash – Momentary flash of green light occasionally seen in horizon just after sunset, or before sunrise, in clear atmosphere. Due to refraction of Sun’s light.
Green Sea – Sea that sweeps over a vessel without breaking. Solid unbroken water that is shipped aboard.
Greenheart – Tough American hardwood timber with high marine durability, prized for keels, etc.
Greenhouse Effect – The process by which the Earth’s atmosphere limits the reflection of solar heat back into space. The increasing proportion of carbon dioxide in the atmosphere is increasing the Earth’s heat retention, and threatening climate change.
Greenwich – The historic London observatory and suburb through which 0º longitude passes.
Greenwich Date – Time and date at Greenwich corresponding to an instant of time at another position.
Greenwich Hour Angle (GHA) – is the celestial longitude measured from Greenwich to 360 degrees westward.
Greenwich Mean Time – Time based on hour angle of point of definition of mean time as measured at Greenwich.
Greenwich Meridian – Adopted as the prime, or International, meridian, largely because its antimeridian—the Date Line— passes through no important land masses.
Gregale – N. E. gale in vicinity of Malta during winter. Name is also given to similar wind in Tyrrhenian Sea and off S. Coast of France. Strong cool north easterly wind – one of the eight traditional traders winds of the Mediterranean Sea, notably the West Mediterranean.
Gregorian Calendar – Reformed calendar introduced by Pope Gregory XIII in 1582. Previous (Julian) calendar assumed year to be 365 1/4 days, which was 0.0065 of a day in excess. Gregorian calendar will be in error by one day in A. D. 5442.
Gridiron – A support (usually a bed of logs) for a vessel to take the bottom in large tidal areas to dry out and enable underwater repairs.
Grids – Strainers around the inlets of sea cocks or propeller thrusters.
Grim Wheel – Blades fitted abaft a ship’s propeller to divert the slip-stream and thus increase the fore-and-aft thrust.
Gripe – The outer forefoot timber fastened to the lower stem. A vessel gripes when her tendency is to come up into the wind.
Gripes – Lashings to hold a boat down onto the vessels deck.
Griping – Coming too close to wind when under sail.
Grog – Mixture of rum and water. Named after Admiral Vernon, who first issued watered rum. He was in the habit of wearing grogram breeches, and was nicknamed ‘Old Grog’.
Grommet – Ring made of rope strand laid up around its own part.
Grooving – In a steel plate, is the formation of a narrow groove by corrosion.
Gross Pressure – Total pressure as differentiated from pressure that ignores atmospheric pressure. Steam gauges of boilers indicate pressure in excess of atmospheric pressure.
Gross Tonnage – A formula for measure of the internal volume of a vessel (less certain excluded spaces) in volumetric tons where 1 ton = 100 ft³.
Ground – Applied to the electrical potential of the earth’s surface. It can be established by a connecting the earth to a live conductor, including any metal area which forms part of the wetted surface of a vessel’shull that may be live. Grounding: An unintentional contact with the seabed.
Ground Futtock – Floor timber lying on keel and bolted to keelson.
Ground Log – Log that measures vessel’s speed over the ground. Has a lead, or other weight, and a marked log line.
Ground Rope – Roping along bottom of a trawl net.
Ground Speed (G.S.) – The speed an aircraft is making relative to the earth’s surface.
Ground Swell – Swell not caused by wind prevailing at the place. A swell that on reaching soundings of half its wavelength, rises and becomes shorter and steeper.
Ground Tackle – Ship’s outfit of anchors and cables particularly that part that is in use.
Ground Tier – Lowest tier of cargo in a hold.
Ground Ways – Launching ways down which the cradle slides
Groundage – Money paid by a vessel for occupying space in a port.
Grounding – Bringing vessel’s keel into contact with the bottom so that she ceases to be completely waterborne.
Grounding Clause – Inserted in a policy of marine insurance to exclude the taking of the ground, in certain rivers and harbours, from consideration as a stranding.
Groundways – Timber baulks that are laid across the keel blocks to support a vessel on a slipway’s cradle.
Group Flashing Light – A light showing at regular intervals a group of two or more flashes.
Group Occulting Light – A light showing at regular intervals a group of two or more sudden ellipses, the periods of light being longer than the periods of dark.
Groupage – The consolidation of several compatible consignments into a full container load.
Growing – Increasing of size of a wood-built vessel after launching. 2. The direction of an anchor cable as it takes the weight.
Growler – Small iceberg that has broken away from a larger berg.
Grown Chock – A triangular bracket or knee that is sawn from the bow of a tree so the grain follows the shape, thus providing the greatest strength.
Grown Spar – Wooden spar made from one tree, as distinguished from a made spar.
Groyne – Walls of stone or timber constructed down into the shallow water at right angles to the foreshore to minimise coastal erosion and sand drift from alongshore currents.
Grus – Constellation in about R. A. 22h; Dec. S47°. Has one navigational star.
Guarantee Dry Dock – Return to the ship builder usually at the end of the first year.
Guard Boat – Ship’s boat, in R. N., carrying the officer of the guard.
Guard Rails – Permanent rails, or iron stanchions, with wire or chain rove, fitted on outboard edge of a weather deck or superstructure.
Guard Ship – Warship formerly anchored in a port to act as a receiving ship, to control movements afloat, and to maintain order.
Guard Zone – A user determined area of the radar screen, within which the presence of an echo causes an alarm to sound.
Guards – The. Stars γ and β of Ursae Minor, the Little Bear.
Gudgeon – A rudder attachment fitting.A metal eye attached to the transom of boat to take the pintle (pin) of a rudder; alternatively, gudgeon (eye) may be fitted to a rudder to accept the pintle (pin) on a transom.
Guess Rope – ‘Guess Warp.’
Guess Warp – Rope with one end made fast at a distant point and the other end kept handy in ship so that a boat can be hauled along it by her crew. Standing end may be at a point well forward in ship, at a lower boom or at ring of a laid out edge anchor.
Guess Warp Boom – Boom guyed out well forward in a ship to keep guess warp clear of ship’s side, and give good length for boat to ride by.
Guest Warp – ‘Guess Warp’.
Guiana – About 200 miles wide.
Guiana Current – Westerly current about 50 miles off N Coasts of Brazil and
Guides – Iron castings guiding crosshead of piston of a reciprocating engine. Ahead guide is larger than astern guide and usually has a water service for cooling purposes.
Guinea Current – Easterly current running between Cape Roxo and Bight of Biafra. Rate sometimes exceeds three knots.
Gulf – A very large area of water contained within a fold of coastline and/or islands.
Gulf Stream – The Ocean current setting Northerly along the North American East coast then Easterly across the North Atlantic, bringing a temperate climate to Northern Europe from the Caribbean.
Gulf Weed – Weed found floating in an area of about a quarter of a million square miles of Gulf Stream between 19°W and 47°W and 20° to 45°N. Some of it is occasionally carried to British Isles.
Gull – Sea bird that feeds on fish and breeds on rocky headlands. There are about 20 different types and, in common speech, the name includes skua, tern, petrel and others.
Gun Port – Openings in a ship’s side through which gun barrels can protrude.
Gun Room – Nowadays, mess of R. N. officers of subordinate rank— sublieutenants, midshipmen, cadets. Originally, was Gunner’s store room, and messing place of Gunner and his subordinates.
Gun Running – Illicitly carrying arms into a country.
Gun Tackle – Purchase by which a gun was hauled out after recoil due to firing. Consists of two single blocks with hook in each.
Gunboat – Small warship with relatively large gun power. Primarily, though not exclusively, intended for service in rivers and shallow waters.
Gunkholing – Cruising in shoal water or overnighting in small coves.
Gunmetal – Alloy of approximately 88% copper and tin.
Gunner – Commissioned officer in R. N. Responsible for ammunition and gunnery stores. Has other duties in connection with armament, and is assistant to gunnery officer.
Gunners Quoin – Wedge used by gunner when laying a muzzle loader.
Gunter Rig – Version of gaff rig where the gaff is hoisted tight to the mast to form a mast extension. Often the rig can stow within the boats deck length.
Gunter’s Scale – Large, flat boxwood board having scales of equal parts on one side and logarithmic scales on other side. Required values were found by use of dividers or a ruler. Invented by Edmund Gunter (1581-1636) and in use for more than 200 years.
Gunwale – Side timber, or wale, covering the timber heads, and to which the breechings of upper deck guns were secured. 2. The upper strake of a boat’s planking, particularly its upper edge, is now called the gunwale; as, also, is the upper edge of bulwarks.
Gunwale Bar – Angle bar connecting deck stringer plate to sheer strake.
Gusset – A scab that joins the side and bottom frame members at the chine.
Gusset Plate – Plating that is attached by angle irons to knit together two members of a ship’s structure.
Gust – A sudden, stronger wind of short duration.
Gut – Narrow deep inlet.
Gutter Bar – Inboard angle bar of a waterway at side of deck.
Gutter Ledge – Fore and aft beam in middle fore and aft line of a hatch covered with arched hatch covers—which it supports at their middle and highest part.
Gutterway: –A trough along the shelter deck’s edge which disposes of runoff from the deck wash.
Guy – Rope or tackle by which a boom or derrick is controlled laterally.
Guyot – Tablemount.
Gyassa – Egyptian boat used on Nile for transport of cargo. Has two masts, lateen sails and can carry up to about 200 tons.
Gybe – To turn a sail boat so that the change from port to starboard tack occurs by presenting the vessel’s stern to the wind. The momentum of the booms travel from loose sheeted on one side to loose sheeted on the other side can cause damage if poorly executed.
Gybe-ho – Warning cry of imminent gybe manoeuvre.
Gyn – ‘Gin.’
Gyration – Movement, round an axis, that is accompanied by generation of centrifugal and centripetal forces.
Gyro Compass – A spinning compass that always remains pointed in the direction that it was first spun (true north).
Gyro Repeater – Electrically-operated dial that is graduated as a compass and kept in step with master gyro compass; so indicating position of gyro compass at stations remote from it.
Gyropilot – Gyro-controlled automatic steering device.
Gyroscope – Rapidly-rotating wheel so mounted that it has three degrees of freedom: 1, freedom to rotate on its own axis; 2, freedom from constraint about its horizontal axis; 3, freedom from restraint about its vertical axis. These allow the rotating body to keep its direction in space unless otherwise disturbed.
Gyrostat – Rapidly rotating wheel that is constrained about either its vertical or its horizontal axis. It thus has two degrees, only, of freedom.