Cambridge
School of Navigation John Starkie, PhD, RNR
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G Golf
I require a pilot
Gaff, Gale, Galileo, Galleon, Galley, Galliot, Gallows, Gammon, Gangplank, Gangway, Gantlet, Gantlope, Garboard, Garland, Gas, Gash, Gasket, Gauge, Gauntlet, Gearbox, Gennaker, Generator, Genoa, Gig, Gimbal, Gipsy, Give way, Glass, GLONASS, Glue, GMDSS, GNSS, Good, Gooseneck, Goosewinged, GPS, Graft, Grating, Great circle, Greenwich meridian, Gripe, Grockle, Grog, Groggy, Grounding, Ground track, GRP, Guard wire, Gudgeon, Gulf, Gun, Gunnel, Gunter, Gunter's line, Gunwale, Gust, Guy, Gybe, Gyroscope
A gaff-rigged sloop
n A hook, on a long pole, for landing big fish.
A gaffe is an embarrassing spoken mistake.
Gale
A wind of Force 8 on the Beaufort scale, with speeds of 34 to 40 knots.
A yachtsman's gale is Force 6 with wind speeds of 22 to 27 knots.
A near gale is Force 7, with wind speeds of 28 to 33 knots.
A severe gale is Force 9, with wind speeds of 41 to 47 knots.
Galileo
Galileo is Europe’s Global Satellite Navigation System (GNSS), providing improved positioning and timing information.
Galleon
Sailing boats are now (early C21) defined by their rig. In earlier centuries they were defined more by their purpose or size. As the purpose, size and rig evolved over decades and centuries names tended to linger, so that in two different centuries boats with the same type-name might be very different.
The term "galleon" was originally given to certain types of war galleys with 80, 64 and 60 oars, used for battle and on missions of exploration, in the 12th and 13th centuries.
The sailing galleon evolved from the carrack in the second half of the 16th century. The forecastle was lowered and the longer hull improved stability and speed. Galleons were purpose-built warships, and were stronger, more heavily armed, than carracks. Later, between the 16th and 18th centuries a galleon was a large, multi-decked sailing ship, with three or four batteries (decks) of cannon, used primarily by European states.
The galleon was the prototype of all square rigged ships with three or more masts for over two and a half centuries,
The principal warships of the opposing English and Spanish fleets in the 1588 confrontation of the Spanish Armada were galleons, with the modified English "race built" galleons developed by John Hawkins proving decisive, while the capacious Spanish galleons, designed primarily as transports, showed great endurance in the battles and in the violent storms on the voyage home; most survived the ordeal.
Charles Galley, sister ship to Adventure Galley
Galliot
Fusta
Sailing boats are now (early C21) defined by their rig. In earlier centuries they were defined more by their purpose or size. As the purpose, size and rig evolved over decades and centuries names tended to linger, so that in two different centuries boats with the same type-name might be very different.
Historically, in the Mediterranean Sea, a galiot was a type of ship with oars, also known as a half-galley, then, from the 17th century forward, a ship with sails and oars.
In the North Sea a galiot was a type of Dutch or German trade ship, similar to a ketch, with a rounded fore and aft like a fluyt. They had nearly flat bottoms and were usually fitted with leeboards. to sail in shallow waters.
To Falconer, in 1815, it was " . . a Dutch vessel, carrying a main and a mizen-mast, and a large gaff-main-sail."
Gangplank
A moveable bridge used to board or leave a ship at a pier.
See Brow.
Gangway
A narrow walkway between the forecastle and the quarterdeck, to obviate the need to step down into and up out of the waist.
Gantlet
See Gantlope, below.
Gantlope
A severe, often capital, nautical punishment in which the offender (usually a thief) ran between two rows of men who beat him with knotted knittles (or nettles).
Often known as "running the gantlet"
There is no clear association with 'gauntlet' as in 'glove'.
Garboard
The lowermost strake of the planking, fitting into the rabbet of the keel.
The garboard was the most difficult of all planks to fit because it twisted, often through 90° or more from stem to stern.
Garland
A net, with a hooped opening, in which sailors kept their personal belongings.
A shot-garland was a board, or plank with hemispherical cavities in which cannon balls were kept close to the guns. There is no evidence for the use of 'brass monkeys', and the story of why balls fall off brass monkeys is almost certainly apocryphal.
Gas
n A generic term for propane, butane or a mixture of the two commonly used as a fuel in galley stoves on small boats.
Propane is sometimes used to power small outboard motors.
Gas has a lower energy density than solid fuels such as coal, or liquid fuels such as alcohol, petrol, paraffin or diesel fuel, but a much higher energy density than electrical batteries. It is sold (and can be carried and used) in a much more convenient package than solid or liquid fuels.
Gas has a lower flashpoint than solid fuels or diesel fuel and is comparable with petrol vapour. It is heavier than air; escaping gas sinks into the bilges of a boat where a spark causes it to explode and destroy the boat.
n A mixture of flammable gases once derived from the distillation of coal and now extracted from deep within the earth's crust, used as a fuel for heating and cooking in town houses.
n A contraction of 'gasoline', the North American word for petrol.
Air is a mixture of several gases, including Nitrogen, Oxygen, Carbon dioxide and many rare gases in small amounts. The unique and characteristic property of a gas is that it expands (or compresses) to fill, homogeneously, the entire volume of its container. By contrast, liquids and solids occupy a fixed volume (at a given temperature and pressure) irrespective of the volume of the container.
Gash
Rubbish; refuse.
To "ditch the gash" is to throw the rubbish overboard or, in the light of MARPOL 73/78 , to take it off the boat to a shore-side disposal facility. All European ports and marinas have rubbish skips, oil disposal drums and dead battery banks.
MARPOL is an acronym for Marine Pollution Regulations, 1973 and 1978.
See Pollution.
Gasket
A plaited cord permanently attached to a yard and used to hold the sails closely to the yard when furled (or stowed).
Most 21st Century sailing vessels use sail-ties (tyers), which are not attached to anything and which migrate into nooks and crannies all over the boat.
Gauge
A device for measuring.
A pressure gauge measures the pressure of, eg, oil in an engine, air in a cylinder.
A barometer is a gauge which measures atmospheric pressure.
A tide gauge measures Height of Tide (but not depth of water).
See 'Instrument'.
Gauntlet
A heavy glove which fits the hand, wrist and part of the arm.
"Running the gauntlet" see Gantlope
Gearbox
Gears are (usually) toothed inter-engaging wheels of different sizes. As one gearwheel rotates its teeth engage with another which, being of a different size and having a different number of teeth, rotates at a different speed and in a different rotational direction. The assembly of gears is arranged inside a container (the gearbox) which excludes dust and dirt and contains a lubricant.
A gearbox is placed between an engine and its propeller so that the propeller rotates at a different speed from the engine, and can be arranged to rotate in a different direction.
Generator
Broadly, a device which changes energy from one form to another.
More specifically, a device which produces (generates) electricity. These devices include alternators, dynamos, solar panels, wind turbines, water turbines, petrol, diesel or gas powered engines.
Gennaker
A large, lightweight genoa used for downwind sailing.
Said to be intermediate between a spinnaker and a genoa, but it is usually a staysail, which a spinnaker never is.
Genoa
A jib, or foresail, the clew of which extends abaft the mast. A genoa is usually a staysail.
Gig
A small boat for the captain's use.
Gimbal
A device which allows a lamp or cooker or compass (or camera) to remain upright however the boat heels or pitches.
Gipsy
Part of the rotating mechanism of a capstan or a windlass may be grooved to fit the line used, or it may have ridges and hollows calibrated for the chain used.
Give way
IRPCS Section II refers to the conduct of vessels in sight of one another.
IRPCS Rule 16 "Action by give-way vessel" says
"Every vessel which is directed to keep out of the way of another vessel shall, as far as possible, take early and substantial action to keep well clear."
The order to a boat's crew to begin rowing, so that the boat makes way through the water.
Before the IRPCS, a vessel 'had way', or was 'making way', if she were moving through the water. The IRPCS redefined 'under way' to mean " . . that a vessel is not at anchor, or made fast to the shore, or aground. " A vessel no longer needs to be moving through the water to be under way.
Glass
n A state of existence for some 'solids'. A non-crystalline amorphous solid. At high temperatures sand melts; when it cools it becomes a glass.
Common (silicate) glass is an amorphous transparent solid. When heated it softens and then liquefies without a clear melting point.
Glass can be spun into fibres and woven into sheets or mats. Such mats can be shaped into boats and saturated with activated resin (such as epoxy resin). Glass fibre, or fibre-glass, or glass reinforced plastic (GRP).
n A barometer.
n A telescope.
n An hour-glass (or sand-glass) is an instrument with two glass bulbs joined by a narrow neck. When the glass is inverted the sand flows from the upper bulb to the lower bulb in a calibrated period of time. During the Age of Sail the halfhour-glass was used to measure the interval between bells. The twentyeight-second glass was used to time the reading of the log.
The sand flows through an egg-timer in about 3 minutes.
GLONASS
"Globalnaya navigatsionnaya sputnikovaya sistema"
The global navigation satellite system (GNSS) of the Soviet Union (now the Russian Federation). Beginning on 12 October 1982, numerous rocket launches added satellites to the system until the constellation was completed in 1995. After a decline in capacity during the late 1990s, in 2001, under Vladimir Putin's presidency, the restoration of the system was made a top government priority and funding was substantially increased. GLONASS is the most expensive program of the Russian Federal Space Agency, consuming a third of its budget in 2010.
Glue
A material which binds other materials together.
Most glues begin as a more or less viscous liquid. The liquid is applied to one or both surfaces to be held, and the faying surfaces are clamped together. Over time, the glue dries, or cures (oxidises or polymerises) to hold the two surfaces together.
GMDSS
Global Maritime Distress and Safety System: an international set of safety procedures, equipment and protocols to improve safety and rescue at sea.
The equipment includes DSC radio, EPIRB, Inmarsat, NAVTEX, PLB and SART.
GNSS
Global Navigation Satellite System.
The four operational systems are GPS, GLONASS, Navic* and Galileo.
The Chinese system, BeiDou, has been described as a potential navigation satellite system to overtake GPS in global usage, and is expected to be more accurate than the GPS once it is fully completed. The current third generation of BeiDou claims to reach millimeter-level accuracy (with post-processing), which is ten times more accurate than the finest level of GPS.
* The Indian Regional Navigation Satellite System (IRNSS)
Good
Good visibility is more than 5 miles.
Because the Radio 4 Shipping Forecast is restricted to 350 words a standardised shorthand is used: the word 'good' means 'visibility of more than 5 miles'.
Gooseneck
The universal joint which links the boom to the mast.
It allows the boom to swing from side to side and also to be angled upward.
Goosewinged
When a fore-and-aft rigged boat is sailing downwind the jib may be set to one side and the mainsail to the other.
When a square-rigged vessel is sailing in a very strong wind a sail may be fully furled to the middle of the yard with only the clews set.
GPS
Global Positioning System: the US form of Global Navigation Satellite System (GNSS). A device which measures the time taken for a signal to travel from a satellite to the device. These times (from several American satellites) are translated by the device into position on the surface of the Earth. A series of positions can be described, by the device, as a Course over the Ground (COG) and a Speed over the Ground (SOG). These positions may be displayed on the electronic chart of a chartplotter. See also GNSS, GLONASS, Galileo, BeiDou, Navic.
See Log. .
Graft
A decorative and practical ending for a rope. The fibres at the end of a rope are woven around the rope, reducing its thickness slightly and creating a decorative handhold.
Sailors often made ornamental and useful objects, such as key fobs, belts, lanyards, from the ends of old ropes: when they sold these objects ashore it was "money for old rope". Grafting was both a mild punishment and a means of preventing sailors cutting off the ends of ropes for their own ends (!) (purpose).
Grafting the end of a rope could take a whole day: hard graft!
Grating
An open work covering, or ceiling, made of wooden strips.
The example shown here was made in 2017 by Jim Ledger for the forepeak of his catboat.
Great Circle
The largest circle which can be drawn on a sphere.
The Equator is a great circle of the earth, as are all the meridians of longitude.
When planning a course over long distances, a great circle is the shortest distance between two points. Unless the line is along the Equator or a meridian a great circle is not a rhumb line.
Greenwich Meridian
The Prime meridian. Half of a great circle linking the North Pole, Greenwich in East London and the South Pole.
Zero° East and zero° West. It is noon Greenwich Mean Time (1200GMT) when the sun is directly overhead Greenwich.
Gripe
n The shape of the deadwood at the stern or at the forefoot. The gripe affects the way in which a ship sails (whether she has weather helm or lee helm) and tacks.
v A sailing ship gripes when she tends to move up to windward as she sails; she has weather helm.
Grog
During the Age of Sail a pint of rum a day was issued to all sailors over the age of twenty.
In 1740 Admiral Vernon ordered that the men's rum be diluted with equal parts of water.
Vernon's practice of wearing a grogram coat earned him the nickname 'Old Grogram', and his watered rum came to be called 'grog'.
Alan Grogono (known as 'Grog') runs the best animated knot website on the internet.
Groggy
Drunk; inebriated (from having drunk an excess of grog).
Grounding
When a vessel touches the sea bed, or runs aground.
Ground track
A line on the chart describing a vessel’s course over the ground.
It is a vector where the direction is in °T and the magnitude is the distance travelled (over the ground) in one hour.
A ground track is characterised by two arrow heads part way along the line.
In calculating a course to steer the ground track is (usually) a straight line between the present fix and the destination: it has direction but its magnitude is estimated graphically when the tide vector and the heading vector have been drawn.
In estimating a position the heading vector and the tide vector are drawn on the chart and the ground track is estimated graphically; when drawn, it has both direction and magnitude.
Groyne
A wall or fence, usually wooden, extending from the beach at right angles into the sea.
Groynes restrict the movement of sand and shingle along the coast.
GRP
Glass reinforced plastic. Glass-fibre, or fibre-glass. The construction material used for many modern boats. Glass is spun into fibres, which are then woven into a mat and saturated with resin (often epoxy resin) which sets hard.
Guardwire
Wires along the sides of the boat, at about knee level, which purport to prevent the crew from falling off the boat.
Some authorities (such as the RYA) regard guard wires as essential safety equipment. Others (like the Pardeys) see their presence as more dangerous than their absence; on yachts up to about 40 or 50 feet the stanchions holding the guardwires may not support the kinetic force of a crewman falling heavily against them; when moving forward, many crewmen support themselves against the guardwires instead of using harness tether and jackstays.
Gudgeon
Pintles and gudgeons are used to attach a rudder to the transom of a boat; the pintle has a pin, the gudgeon has the hole to receive the pin.
In this example the gudgeon is attached to the transom (on the right) and the pintle is attached to the rudder (on the left), which is held out of the gudgeon.
The gudgeon in this picture is not firmly screwed down because the transom of this West Wight Potter is being repainted.
Gulf
An extensive area of water connected to the sea by a relatively narrow straight.
Gun
A device for projecting missiles rapidly over long distances.
The missiles are usually inert masses, not self-propelled. They are propelled by a controlled explosion, the rapid combustion of a powder and the rapid expansion of hot gases. The powder burns in a cartridge held in the breech of the gun. The expanding gases propel the missile along a barrel and from the muzzle at the end of the barrel.
Many varieties of guns range from small, hand-held devices (with barrels a few centimetres long and missiles (bullets) of a few grams) to enormous immobile devices (with barrels many metres long and missiles weighing many kilos).
Cannon were (are) large guns weighing tons rather than pounds.
Early (Age of Sail) cannon were mounted on wheeled trucks on the deck. Their missiles were spherical iron balls weighing from 4 pounds to 32 pounds and could be propelled for three miles or more. They damaged their target by the momentum of their weight and speed.
Modern ship’s cannon are mounted on revolving turrets; they are computer-controlled; and they fire explosive or incendiary shells.
Rifles differ from guns in having a spiral groove (rifling) cut into the wall of their barrels. This causes the missile (a bullet) to rotate; this in turn keeps the bullet on a truer trajectory.
Machine guns are rifles designed to fire very many bullets rapidly, one after the other.
Small hand-held guns (pistols) are usually rifled. There are two kinds: revolvers have a revolving chamber with six cartridges (rounds); automatic pistols have rounds held in a clip inside (usually) the hand-grip.
A device is not a gun when the missile contains propellant which continues to accelerate the missile after it has left the barrel. Such devices include modern-day mortars (although the original mortars were short- but wide-barrelled guns) and rocket launchers.
Gunter
Folkard describes the gunter as a form of gaff which is vertical. It carries the peak of the mainsail above the top of the mast, effectively increasing the height of the mast. When the sail is reefed the gunter yard* is brought part way down, thereby effectively decreasing the height of the mast.
A sliding gunter is held parallel to the mast by a set of linked hoops, two of which are attached to the yard while the other two slide on the mast. Both Falconer and Luce thought of a sliding gunter as a form of topmast.
A folding gunter is held to the mast by jaws and a parrel; when the ha'lyard is eased the tip of the yard falls away and the yard descends to lie along the top of the boom. When the sail is reefed the ha'lyard is moved further up the yard.
* The use of the word 'yard' is difficult to understand; 'topmast' might be more appropriate for both the sliding and the folding gunter. See lugsail.
Like the gunter rig, the Solent rig (see Folkard) had (has) a triangular mainsail the peak of which is raised by an asymmetric yard, not a topmast, hauled up parallel to and higher than the mast. This may be why the gunter spar (gaff or topmast) is often called a yard.
One modern 'authority' states that a 'gunter' is the wire span along the length of a gaff along which the block of the ha'lyard travels: I can find no historical precedence for this.
Gunter's Line
A line of numbers on a logarithmic scale once used, in conjunction with a pair of compasses or a sliding scale, for calculation.
A precursor to the slide-rule.
Gunwale
pron Gun'l'. The phonetic contraction ‘gunnel’ has been in use since at least 1780, when Falconer used it in his Dictionary of the Marine. It was the wale (or thicker plank) which was pierced for the gunports at deck level. It is now the topmost plank of the hull, often reduced to a beading of wood around the hull at deck level, or simply where the hull meets the deck. In the last case, there may be a toerail at the gun’l’.
Since the topmost plank is now rarely a wale, and since sailing boats now rarely carry guns, it might seem appropriate to use the term sheerstrake or, on GRP boats where there is almost always a toerail, to abandon the term altogether.
Gust
A sudden and short-lived increase in the strength of the wind.
Guy
A generic term for a sheet, or brace; more especially applied to controlling a spinnaker boom.
Gybe
Of boats with fore-and-aft sails (such as Bermudan or Gaff-rigged boats), turning from one tack to another with the wind behind the boat. An accidental gybe may cause the boom to cross the boat very quickly: this may break sheets, spars or people’s heads. If there is no kicking strap to hold the boom down it may rise high into the air and then fall down heavily: a Chinese gybe.
When running downwind the mainsail is often ‘by the lee’. An accidental gybe can be avoided by rigging a line (a preventer) between the boom and a cleat well forward.
To execute a planned gybe the helmsman and mainsheet handler must work together. As the helmsman turns the boat, and the wind draws aft, the mainsheet should be pulled in hard so that the mainsail is fore-and-aft as the wind comes behind. As the helmsman continues the turn the wind will blow on the other side of the mainsail, the boom will cross the boat and the sheet should be eased quickly, and then trimmed. The winch should not be used, because the sheet handler cannot disengage the handle and remove the sheet from the winch fast enough to ease the sheet correctly.
(If the sheet cannot be hauled by hand, the boat is over-canvassed and should be reefed.)
Gybing a gaff mainsail is much more difficult than gybing a Bermudan mainsail. The gaff always lags behind, and then overtakes, the boom and is hard to control even when vangs are used.
Gybing the jib, or genoa, is less tricky than gybing the mainsail; even so, the two sheet handlers should coordinate their efforts to avoid the sail becoming wrapped around the forestay.
It was normal for square-rigged vessels to change tack with the wind behind; this was known as ‘wearing ship’ and was much safer (for them) than staying through the eye of the wind.
Gyroscope
A heavy disc rotating very quickly in a gimballed framework maintains its orientation, and the orientation of its supporting framework, to the earth however it is moved.
A gyroscopic compass maintains its orientation to the earth however the ship pitches, rolls or yaws; it is independent of the earth's magnetic field and so can be calibrated to True North.