L   Lima

You should stop,

I have something important to communicate.


A vessel labours when progress becomes difficult because of the sea state.   She may pitch and roll excessively;  this puts a strain on the stays and shrouds and on the crew.

A vessel might labour under the press of too much sail,  which might push her head down into the water or cause her to heel excessively.


v   To lace a sail to a spar is to pass small line through the eyelets in the sail and around the spar.

n   The gold braid,  depicting rank,  on a naval officer's uniform.


The small line used to attach a sail to a spar such as a gaff or boom or mast.

The process of attaching a sail to a spar with small line.


All stairs aboard ship (except for staircases on passenger ships) are called ladders.   They are often so steep as to be nearly vertical.


Lagan is cargo that is lying on the bottom of the sea, sometimes marked by a buoy,  and which can be reclaimed.   See Derelict.


Large ponds,  perhaps close to or linked to the sea in some parts of the Americas and West Indies.

Laid up

Preserved,  unused;  Kept in good condition against being used again.



A device which gives out light.

There is an implication (in early 21st century) of a device which burns oil,  the flame of which gives off a white light.   In this context a lamp may be used to light the cabin of a boat,  or lamps with coloured glasses might be used as navigation lights.   Such lamps must be kept upright and so are usually gimballed.

Modern devices which use electricity are usually called lights.


n   That part of the Earth not covered by water.

n   The part of a plank which fays with (touches,  or lands upon) another timber or plank.

Land breeze

At the end of the day and overnight,  in Summer,  the land cools more quickly than the sea.   The warmer air over the sea rises,  by convection,  and the cooler air over the land moves seaward to take its place.   This creates a breeze sufficient to move sailing vessels.

See Sea Breeze.


The first sighting of land after a sea voyage.   Most skippers attempt a landfall close to a Safe Water Mark.



v   To put passengers or crew ashore.   To disembark.

ng   The place (jetty,  wharf,  beach) where passengers are put ashore.


Entirely surrounded by land.


Someone who has never been to sea.


Something unmistakeable on the land as seen from the sea.

Land lubber

A person from the land,  not the sea,  unfamiliar with the ways of seamen and ships.   See Lubber.


n   A line to make an object (such as a knife or whistle) fast,  or to aid in carrying it.   Anything used aloft should be secured with a lanyard to prevent it falling and causing damage or injury on the deck below.

n  Lengths of small line used,  for example,  to secure the shrouds to the chainplates.   They are more flexible and easy to repair than bottlescrews.


When the planks of a wooden boat overlap along their edges.

Generally,  the word used in the USA for clinker.

Strictly,  clinker refers to the way in which the overlapping planks,  or strakes,  are held together and to the ribs (frames) with clench nails.   In smarter clinker dinghies the strakes are clenched with copper nails and roves.

In a glued clinker boat the plywood strakes are held together with glue,  usually epoxy resin.



The left hand side of the boat,  looking forward.   Now usually called the port side.   Because the steering board (see ‘Starboard’) was on the right hand side a ship would moor ‘port side to’,  ie with it’s left hand side to the loading wharf.   This became known as the ‘loading board’,  or l’a’(r)board.



v   to bind or make fast with several turns of line or rope.

n   A lashing is the binding of parts together with line,  or the line itself.

n   A whip,  for punishment.  See flog.

v   To whip,  as a punishment



Lowest Astronomical Tide.

The lowest tide which can be calculated from the relative positions of the sun and moon.

Also known as Chart Datum   the horizontal datum from which the charted depth and the height of tide are measured..


A triangular sail suspended from a yard at an angle of about 45 degrees to the mast.   The term derives from the word “Latin,” implying “Mediterranean”.   See Xebec.

A settee sail is similar to a lateen,  but is four-sided,  with a short luff vertically from the forward end of the yard to the tack.

Neither sail has a boom.

Lateral buoys

Channel markers.


  • A parallel of latitude is an imaginary line, circling the Earth parallel to the Equator,   and measured in degrees North or South of the Equator,  the angle being subtended at the centre of the Earth.

  • The distance of an observer North or South of the Equator in degrees of arc subtended at the centre of the Earth.   Since one minute of arc is equal,  at the surface,  to one sea mile,  latitude can be used to measure distance on the sea surface.

Finding latitude at sea is fairly easy.   Since the Pole Star is on the extension of the South-North axis of the earth,  the angle of the Pole Star above the Northern horizon is proportional to the latitude of the observer.   The same is true of any star (other than the sun) at its highest elevation,  in either hemisphere.


n   The largest boat carried (or,  more usually,  towed) by a warship during the Age of Sail.

n   A power driven vessel,  usually undecked.

v   To move a boat from the land to the water.   Ships are launched down slipways,  after building,  and are fitted out and commissioned on the water.   Dinghies are launched almost every time they are used.


To move,  to come or to go.

An officer may instruct the crew to "lay aloft",  meaning to climb the mast.

The lay of a rope is the way in which the fibres are twisted together.

Lay down

The keel of a ship is laid down first on the stocks before the rest of construction.


n   A small stowage locker far aft.

n   The storeroom for provisions.


Lines running from near the top of the mast to the boom on both sides of the sail.
When the sail is handed it is gathered by the lazyjacks and prevented from billowing to leeward or falling into the cockpit;  they hold the boom up in the manner of a pair of topping lifts
Lazyjacks may consist of more than one pair of lines,  often balanced by small blocks.  Control lines may run to the heel of the mast to control the tension of the lazyjacks.   They may be linked to a permanent sail cover attached to the boom.


n   pron   led

A metallic element of specific gravity 11.34,  making it one of the heaviest common metals.   It has a low melting point (327°C) and is easily cut with a saw.   It is probably the metal most suitable as ballast for a sailing boat.   It is also used in plumb bobs (the Latin name for lead is Plumbum;  the chemical symbol is Pb) and lead lines.

n   pron   led

A nominalisation of lead line.

n   pron leed

In a sailing vessel,  the distance from the Centre of Effort aft to the Centre of Lateral Resistance.

v   pron   leed

To guide;  to show the way,  as in leading lights.

A block​,  or pulley,  is used to lead a rope in a different direction.

n   pron   leed

A length of (usually) leather with a loop at one end and a snap shackle at the other,  for controlling dogs;  for 'showing them the way'.

Leading lights

Two lights placed in line to define a safe course along a river or into and out of a harbour.   The nearer light is placed low down close to the water:  the further light is higher,  often on a hillside.   The lights are usually surrounded by,  or accompanied by,  shapes characteristic of the location.

To keep safe a ship or boat keeps the two lights in line with one another;  usually the boat is not pointing toward or away from the lights,  but at an angle to compensate for cross-tides.

Leading lights at Seili,  Finland
Leading line

A line on a chart showing the way into and out of a harbour,  bay or river.

Usually,  there are two marks on the shore to form a transit for the approach or departure.

The line on the chart is marked with the bearing of the two marks.

The marks may be lit,  as leading lights.

At Tarbert,  there is a leading line formed by a Q.G on the island and a tower on the hillside,  on a bearing of 239.2°T.   This line also passes through 2.F.R (vert) on the ferry pier.

Leading line
Lead line

A device for measuring depth of water,  to aid in estimating a position.   It has been used since at least the time of St Paul (Acts xxvii) in the 1st century AD.

A hand lead line was 20 fathoms long,  divided into 20 equal lengths,  with nine marks and 11 deeps.    A lead plummet,  of 7 to 14 pounds (3.2 to 6.4 kg),  was attached to one end.   The bottom of the plummet was hollow and,  in use,  filled with tallow.   When ‘swinging the lead’ a sailor would cast the plummet into the sea and allow the line to run through his fingers.   When the plummet reached the bottom the sailor would ‘read’ the marks and deeps with his fingers and call out the depth of water.   With the plummet back on deck a quartermaster would examine the tallow for evidence of sand,  shells,  mud, etc,  and use this data,  with his dead reckoning,  to estimate the ship’s position.


A deep sea lead line might be 100 fathoms or more,  and would be deployed by several men working together along the side of the ship.

See also Marks and Deeps.   See also Luce.

The lead & line aboard tb Hydrogen

n   Three nautical miles.   One twentieth of a degree of a great circle.

The giant with the 'seven-league boots' could take strides of 21 miles.

n   A group of people dedicated to a single cause.

There is a slight implication of underhandedness,  secrecy.

Co-conspirators are in league with one another.


The unwanted movement of water through the hull or deck into the vessel.


A group of rocks,  or perhaps hard sand,  near the surface of the sea.



The calm region downwind of an obstruction such as a boat or headland.   The downwind side of a boat is the leeward (pron. ‘l’ward’ or ‘looard’) side.


Wooden or metal plates pivoted on the outside of both sides of a boat,  capable of being pivoted down into,  or up out of,  the water,  used to reduce the leeway of a boat while sailing.   They are used on flat-bottomed boats in water too shallow to allow a keel,  most widely in and around the Netherlands and in the Thames Estuary.   The leeboard on the weather side of the boat is usually pivoted up out of the water.

Thames barges used their leeboards to touch and go.

Not to be confused with centreboard or daggerboard,  although all three perform the same function.

The vessel in the right-hand picture is a typical Dutch sailing vessel with a leeboard,  on her Port side,  of classical design.   She is moored in one of the central canals in Amsterdam.

The vessel in the middle picture is another Dutch sailing barge on the river Cam.

Whereas centreboards and daggerboards might often be shaped as aerofoils (hydrofoils),  to reduce drag,  modern leeboards can be shaped as lifting foils with a flat or concave side to leeward and a convex (often NACA shaped) surface to windward.   They may have a higher aspect ratio than the boards shown here.

Tredwen's barge yachts were equipped with leeboards.


Jim Michalack insists that leeboards must be placed at the widest part of the hull so that the water flow across the board is parallel with the hull.   This,  of course,  is nonsense:  the boards must be placed at the centre of lateral resistance so that they balance the leeway caused by the sails.   It is normal to shape the sheerwale so that the board is inclined outward and is almost parallel to the centre line.   Depending on the camber of the board it may be 'toed-in' (with the leading edge a little closer to the centre line than the trailing edge) a few degrees.


n   The aftermost (trailing or leeward) edge of the sail.

The forward,  more or less vertical,  edge of a sail is now known as the luff.   On a square-rigged ship the vertical edges of the square-rigged sails were interchangeable,  depending on the tack,  and were known as the fore-leech and the after-leech.   See Falconer,  Smyth,  Luce.

n   An Annelid worm which sucks blood.   They were once used to remove blood from 'patients who needed bleeding',  and are now use to remove blood from extensive bruises.



A metal bar across the foredeck,  much like a horse across the stern, on which the clew or sheet of a foresail might run.   They are still used on Thames barges and some sailing yachts.

Lee helm

A vessel is said to carry lee-helm when she has a tendency to pay off before the wind (bear away;  turn downwind) and the tiller has to be kept down in order to counteract this.

See weather helm.


The command given to come about,  or change tack,  on a modern sailing boat.

The cry made by some helmsmen as they begin to change the tack.   It is a contraction of "helm's a'lee",  meaning that the tiller has been put to leeward.   It is followed by the skipper's command of "let go (the leeward sheet) and haul (the new leeward sheet)".

Lee shore

The shore downwind of a ship.

The wind blows onto a lee shore.


The leeward side is the downwind side.  The wind blows away from the leeward side.  A vessel to leeward is downwind.


The angle at which a vessel is blown off her course by the wind.

The angle between a vessel‘s heading and her course through the water (her water track).

Any vessel,  power or sail,  will be blown sideways by the wind.   Sailing vessels always have some device (keel,  centreboard,  daggerboard,  leeboard) which resists leeway but does not eliminate it.   Power-driven vessels rarely have such devices.

Any vessel on a constant heading will be blown off her course;  this leeway angle must be accounted for when calculating her course over the ground.

A vessel which chooses its course over the ground must adjust its heading to account for leeway.

Leeway resistance

Keels,   Balance,   Centreboard,  Daggerboard,  Leeboard

Long keel,   Deep keel,  Bilge keel,  Bilge board,  Twin keel

Chine runner,    Wing keel,  Scheel keel,  Hull shape

Both power driven vessels and sailing vessels tend to be blown sideways by the wind.   Power driven vessels rarely have leeway-resisting devices:  they rely on their power and angle to the wind to get where their skippers want to go.   Sailing boats,  however,  rely for their motive power on a wind from one side of the boat or the other:  their motive power,  of itself,  induces leeway.   Leeway resistance is important for a sailing boat.

Leeway cannot be prevented,  only reduced.

Leeway-resisting devices,  or lifting foils,  tend relatively to lift the boat to windward.

Lifting foils generate both lift (to windward) and drag (which slows the boat).

The proportion of lift to drag depends on the aspect ratio of the foil.

Aspect ratio is the ratio of span to chord:  referring to the diagram,

AR = s/c

Where the chord is not constant along the span,  aspect ratio is the square of the span divided by the area of the foil.

AR = s2/A

Generally,   for a given area,  the higher the aspect ratio the greater the lift and the less the drag.

Foils of high aspect ratio are often shaped further to reduce drag and increase lift.   

By 'shape of the board' we might mean the thickness of the board at different parts of its chord.   A NACA foil has a rounded leading edge thickening to a maximum about one-third of the chord from the leading edge.   The rest of the board is progressively thinner toward the trailing edge,  which is cut off square.   A true centreboard would be symmetrical about the centre plane of the chord.   NACA 4-digit shapes are often used.

Twin keels and leeboards can be made asymmetric,  so that each approximates to half of a NACA foil.   If the flat or concave side of the keel or board is kept to leeward the board becomes a true lifting foil,  like an aeroplane wing.

The shape of the foil affects the manoeuvrability  of the boat.

A deep,  high aspect-ratio foil turns (and tacks) easily and quickly,  but will not hold a course without constant attention to the helm.

A low aspect-ratio foil follows a straight course easily,  but turns and tacks slowly.

A single foil is deepest in the water when the boat is upright.   As the boat heels to the wind,  and the foil angles to windward,  it becomes shallower,  presents less area to the side-flow of water and becomes less effective.

The leeward of a pair of twin keels becomes deeper and more vertical,  and therefore more effective,  as the boat heels.

Many sailing areas,  such as the East Coast of England,  are in shallow water where grounding is common and,  often,  intentional.   Many anchorages and moorings dry at Low Water.   It is important that sailing boats can take the ground without supervision:  deep,  fin,  keels are not safe,  but lee-,  dagger- and centre-boards are,  as are twin and bilge keels.   Thames barges and Humber Keels are flat-bottomed with leeboards.


The leeway-resisting effort of a vessel's hull,  including the keel,  is focussed at the Centre of Lateral Resistance (CLR).

The driving force of the wind,  acting through the mast(s) and sheets,  is focussed at the Centre of Effort (CE).

The distance of the CE on front of the CLR is known as the lead (pron:  leed) and determines the balance of the vessel and its rig.   If the CE is too far forward (too much lead) the head of the vessel will tend to be blown away from the wind:  it is said to have lee helm.   If the CE is too far aft (too little lead) the stern of the vessel will tend to be blown away from the wind:  it is said to have weather helm.   Both lee helm and weather helm need constant pressure on the helm to hold a course.   Too much of either becomes tiring for the helmsman:   the angle of the rudder causes turbulent drag which slows the boat.   The extreme of weather helm,  and rudder angle turbulence causing a 'rooster tail',  can be seen in an Una boat or a Catboat running downwind.


Nowadays (early 21st Century) we think of a centreboard as a plate which hangs down from the CLR of a boat,  deep into the water,  and which is pivoted so that it can be raised or lowered,  totally or partially,  at will.

The earliest centreboards were simply long planks of wood fastened lengthwise below the keel:  literally,  boards along the centre of the keel.   They could not be pivoted,  or even moved.

Leeway resistance is related to the area of the board in the water,  the aspect ratio of the board and the shape of the board.

A board of greater area naturally resists leeway better than a smaller board,  all else being equal.

For a given area of board,  a higher aspect ratio is better than a lower aspect ratio.   Consider a rectangular board,  with its leading and trailing edges vertical and its lower edge horizontal (its upper edge is within the boat!).  It's axiomatic that (for a given area of board) the higher aspect ratio board will penetrate deeper into the water than a lower aspect ratio board.

A centreboard needs a case,  first to keep the water out of the boat,  and second,  to provide bearing surfaces for the top of the board.   As the boat is blown to leeward,  and the board resists this,  the force of water on the bottom of the board rotates the whole board around a long fulcrum given by the bottom of the centreboard slot,  in the roll axis.   This tendency to rotate is prevented by the sides of the centreboard case.   The case must,  therefore,  be strong and well supported.   It is common for cases to 'wring' and leak at the junction of keel and board.

Centreboards are often of steel or iron to provide ballast well below the boat.   Occasionally,  on larger boats,  they may carry extra ballast as weights or streamlined bulbs at the lower end.

A significant advantage of the centreboard as a leeway resisting device is that it pivots upward when it touches the seabottom.

A significant disadvantage is that the centreboard case occupies a large part of the interior of the boat and interferes with the accommodation.


Leeway resistance menu

Leeway resistance menu



Dagger board

A daggerboard differs from a centreboard in that it fits closely in its case and does not pivot in the pitch axis.   This is a disadvantage when sailing in shallow water.   If the daggerboard strikes the bottom at speed it can itself break or it may damage its case.   As with the centreboard the case occupies much of the interior of the boat.

Leeway resistance menu


Many of the remarks about the centreboard (ballast,  wringing,  area,  aspect ratio and shape) also apply to the daggerboard.




Leeboards are attached to the outside of the gunwales of a boat,  on both beams.   They are more or less flat plates (like a centreboard or a daggerboard) which hang down into the water.

On larger vessels only the leeboard to leeward is deployed while sailing,  the leeboard on the weather side being raised out of the water alongside the boat.   On smaller boats (such as sailing canoes) a single leeboard might be used on both tacks.

Leeway resistance menu


Like centreboards and daggerboards,  leeboards might be shaped like foils with NACA sections except that the leeward side (when deployed) might be flat or concave.

The remarks about area and aspect ratio also apply to leeboards.


A significant advantage of leeboards,  especially on larger vessels such as Thames barges,  Tredwen's barge yachts or a few Herreshoff yachts is that they are arranged to pivot in two dimensions.   Thus they swing aft and upward when they strike the ground and they pivot outward,  away from the hull,  when they are left down on the weather side of the boat.

Another significant advantage is that they do not intrude (apart from the mechanism for raising and lowering) into the accommodation.

A perceived disadvantage is their appearance,  which some people find ugly.


Long Keels

Long keels are fixed centreboards (in the original sense of the word) occupying most of the length of the boat.   Often,  the keel's draught is greater toward the stern.

Leeway resistance menu


An advantage of a long keel is that the boat is directionally fairly stable:  she holds her course for some time without the intervention of the helmsman.

The corollary of this (often seen as a disadvantage) is that the boat turns slowly in response to the rudder:   when changing tack the boat must be sailed through the turn.


A long keel has a low,  or very low,  aspect ratio,  but may have a relatively large area.


Fixed keels usually contain,  or have attached to them,  ballast to keep the boat upright and stable.


The difference between long keels and fin (or deep) keels is a continuous spectrum.



Deep Keel

Deep keels (also known as fin keels) are fixed centreboards (in the original sense of the word) of higher aspect ratio usually placed near the middle section of the boat (at the CLR) in the fore and aft line.   They appear in a wide range of shapes and sizes.

They are not directionally stable,  but the boat can be turned and tacked quickly and easily.

Deep keels are always ballasted.

Leeway resistance menu



Bilge keels

Bilge keels are set in pairs,  one on each side of the boat at the turn of the bilge.   They are common on fishing vessels which take the ground at each low water:  the boat then rests on its shallow central keel and the two bilge keels.


Bilge keels,  having a small area and low aspect ratio,  are relatively less effective in reducing leeway than other forms of keel:  their primary purposes seem to be to dampen rolling and to keep the boat upright when aground.


Bilge keels are rarely ballasted.

Leeway resistance menu



Bilge boards

Bilge boards are similar to bilge keels,  but smaller.   They are more useful for roll damping than for leeway resistance.

Leeway resistance menu



Twin keels

Twin keels have a greater area than bilge keels,  extending deeper into the water so that when the twin-keeled yacht takes the ground it rests on its twin keels with its centre keel well clear of the bottom.


Twin keels are more effective at reducing leeway than bilge keels.   They may be of high aspect ratio and they may be shaped as symmetric or asymmetric NACA foils in much the same way as leeboards:  they are then as effective as fin (or deep) keels in reducing leeway.   When the boat heels the keel to leeward becomes more or less vertical.


Twin keels are often ballasted in the same way as fin keels.

Leeway resistance menu



Chine runners

These curious 'keels' may have evolved from bilge keels,  or from Scheel keels (to which they are topologically identical) but are not shaped or positioned such that the boat can be supported by them:  they provide only leeway reduction.

They might echo the 'centre-board keel' of 1774 described by Folkard in 1906.

The Paradox microcruiser is the only boat to use them for which plans are available:  Paradox sailors say that they work well.   In a wind a Paradox heels significantly:  this puts the leeward chine runner deeper into the water where it behaves as a leeway-reducing foil of low aspect ratio,  much like a long keel.   Paradox sailors say that their boats tack slowly,  like long-keeled boats.

Leeway resistance menu


Wing keels

There is a vertical keel,  of moderate aspect ratio,  to the bottom of which are fixed lateral,  horizontal ‘wings’.

When sailing upwind,  with the boat heeled,  the leeward ‘wing’ becomes more nearly vertical and improves leeway resistance.   Otherwise,  the large surface area has significant frictional drag.


Leeway resistance menu



Scheel keel

The shape of the keel reduces the flow of water under the keel and so increases leeway resistance

Leeway resistance menu



Hull Shape

All parts of the hull below the waterline contribute to leeway resistance,  but the shape is important.

A round-bottomed boat has less resistance to leeway than a dory or a sharpie.   The Paradox (above) is a small sharpie:  the cross-flow of water under the hull is reduced by the chine runners.

Leeway resistance menu


n   That part of the voyage between two waypoints.

During the Napoleonic Wars,  ships and their crew might be on station for months or years.   When they returned to port the men might not be allowed ashore,  in case they deserted;  so 'wives' were allowed aboard.   At the beginning of a watch,  when rousing the men,  the bo's'n would call "Shake a leg";  those legs showing from under the blankets which were obviously female need not leave their hammocks.

Leg o' mutton

A triangular sail,  said to be shaped like a leg of mutton,  originally a 'shoulder of mutton'.

Respelled and redefined, like so many words,  when it crossed the Atlantic.



n   In some ports and harbours the owners of deep keeled boat expect their boats to take the ground between tides,  or for scraping the bottom.   They may fit metal or timber legs at each beam to keep the boat upright.   It then rests on its own keel and the two legs.

Lie to

Heave to

To arrange the sails and the rudder so that the vessel lies more-or-less still in the water.

For most sloops.  the mainsail is drawing,  the foresail is aback and the tiller is a'lee.

To keep a vessel more-or-less still in the water by deploying a sea anchor from one of the bows.


An Easterly wind in the Mediterranean Sea.



An officer who performs the duties of a superior officer in the absence of the superior officer.

A naval officer next in rank below the captain.


A buoyant ring,  or horse-shoe shaped device,  for keeping a person afloat in the water.   Lifebelts are kept readily to hand so that they can be thrown into the water when someone falls off the boat.


A boat,  often power-driven,  carried by ships for use in the event that the ship sinks.


See lifebelt,  above.

Life jacket

An inflatable jacket (or similar) which supports an unconscious person in the water.

The bladders may need to be inflated by mouth,  or by pulling a lanyard which activates a carbon dioxide cylinder,  or by a salt capsule which dissolves in water and activates the cylinder.

A personal flotation device (pfd) or a buoyancy aid is not a lifejacket.


Lifeboats of the Royal National Lifeboat Institution are kept ashore ready to be manned and put to sea in case of an emergency at sea.



An inflatable raft,  with a canopy,  carried on the deck of small vessels and yachts.   Larger vessels carry enough for all passengers.   On immersion in water a hydrostatic valve releases the raft from its container and inflates it.

Liferaft in its container


adv   A vessel is light when she is not loaded,  or is unballasted.

v  To light;  to help or assist.  "Light along that rope with us,  will you,  mate?"

n   Electromagnetic radiation visible to the human eye.

     A device which emits light.   See lamp.

Vessels carry navigation lights when under way and other lights which show their status or work.

Many buoys have intermittent lights which show their type and position.

n   A window,  as in a portlight.

See Lights.


n   When a ship has sailed as far up an estuary as her draught will allow her cargo is transferred to a lighter for onward carrying.   This makes the ship lighter (!).

n   A handheld device,  powered by petrol or gas,  which produces a small flame for lighting cigarettes or pipes.   They may also be used temporarily to melt and seal the ends of synthetic line to prevent fraying;  the sealed end may be known as a 'butane splice'.


A substantial building or structure which carries a light useful for navigation.   The lights may be red,  green or white,  or a combination of all three.



A discharge of electricity between one cloud mass and another,  or between a cloud and the ground.   The disruption of the air,  being heated very quickly,  causes shock waves which are heard by the human ear as a loud noise,  thunder.

Where the lightning strikes the ground it often causes disruption of the objects it strikes;  trees may explode;  houses may be burned;  people may be killed.


See also  buoy​,  lighthousenavigation lights.

The lights on buoys might flash (Fl),  or occult (Oc) or be isophase (Iso).

Flashing and occulting might be single or grouped. or compound grouped.

Safe Water Marks,  Isolated Danger Marks and Cardinal Marks always have white lights.

Red Lateral,  or Channel,  Markers have red lights:  green Lateral,  or Channel,  Markers have green lights.   (The red or green lights on wharves or piers are fixed (F).)

Special Marks have yellow lights.

Emergency Wreck Markers have alternating (alt) blue and yellow lights.

The lights of lighthouses might flash or (rarely) occult or be isophase

They are usually directional (dir) in that each light can be seen only over a limited arc of the horizon.  

Where there is more than one colour they will be sectored:  each colour can be seen over a limited arc of the horizon,  and only one colour can be seen from any one direction.

Navigation lights of boats are always fixed and sectored relative to the vessel which carries them.

Light characteristics




QFl.R   or Q.R                  

2.F.G (vert)           






A white light flashing twice at the beginning of every 10 second period.   An Isolated Danger.

A green light flashing twice at the beginning of every 5 second period.   A Starboard Hand Marker in IALA-A;  Port Hand Marker in IALA-B.

A quick-flashing red light.   A Port Hand Marker in IALA-A.

Two fixed (F) green lights,  orientated vertically.   On a pier or wharf,  on the starboard side of a channel (IALA-A).   See Southwold pier,  below.

A red light which flashes twice,  then once,  at the beginning of every 5 second period.   A Preferred Channel Marker in IALA-A where the Preferred Channel is to starboard.

A white light which occults twice at the beginning of every 5 second period.   A Safe Water Mark

An isophase white light,  on for 5 seconds,  off for 5 seconds,  in every 10 second period.   A Safe Water Mark.

A white light flashing 6 times plus 1 long flash at the beginning of every 15 second period.   A South Cardinal.

A red,  green and white sectored light,  flashing 4 times at the beginning of every ten second period.   A lighthouse,  with a light 27m above Mean High Water Springs and visible nominally at 5 nM.


A ship,  equipped with a light as for a lighthouse,  permanently anchored (moored) at a strategic point marked on the charts.

Most lightvessels (lightships) have been replaced with automatic buoys or lighthouses.

Limber Holes

Holes drilled horizontally in the vessel’s frames or floor timbers,  permitting the passage of water along the length of the bilge.   If the strum box of the bilge pump is placed at the lowest point of the bilge all the water can be pumped out without moving the pump or the strum box.

Limber holes often become blocked with small debris:  a small-link,  loose chain passing along the vessel through all the limber holes can be pulled back and forth to clear the holes.



n   A long relatively thin material made up of many twisted or braided fibres and strands,  with very many uses on both sailing and power-driven boats.

Luce claimed that anything with a diameter greater than 1.5 inches was rope.

Others suggest that rope is on the reel or in the coil;  anything cut from the reel and put to use is line.   This is at odds with the terms bell-rope,  man-rope,  bolt-rope,  sheet-rope (see Slocum).

It has been suggested that most lines on a boat have a specific name (eg,  sheet,  ha'lyard,  brace,  vang) but virtually all of these words are nominalized adjectives describing 'rope' or 'line'.

n   A one-dimensional figure;  something with length but no breadth or depth;  as a line drawn on a chart with a pencil.


The lights on fixed structures,  such as wharfs and pierheads are red or green,  to show the side of the channel.   They are usually fixed,  not flashing,  and may be two lights vertically orientated.

The lights on Southwold pier (on the right) are 2.F.R.(vert).3M.   That is,  two fixed red lights,  vertically orientated,  visible at a nominal 3 nautical miles.   This tells the mariner that the direction of buoyage along the coast is toward the North.

2.F.G.(vert) Southwold Pier

n   The lines of a vessel

The body plan of a vessel consists of "a series of vertical cross-sections through the hull" .

The profile plan is a series of curved lines showing the shape of the vessel at the buttocks as seen from the side.

The half-breadth plan is "a series of horizontal sections through the hull at (the) waterlines".

See Kopanycia

Lines and offsets


n   The line of battle.   During the Age of Sail ships went into battle in strict formation,  often line astern or line abreast.   The big fighting ships were 'ships of the line'.   Smaller vessels,  such as frigates and sloops,  would have stayed out of the line to act as messengers and signal repeaters.

n   A company which operates passenger vessels (liners) on a regular schedule

'Toe the line'.   To do as you're told,  whether you like it or not.   Sailors to be reprimanded were drawn up before the quarterdeck,  with their toes at a chalk line,  or a seam in the deck planking.   A petty officer would 'draw the line',  beyond which the men could not go.   A 'line in the sand' has a similar,  metaphorical,  meaning.   Politicians often have 'red lines' which mark the limits of their negotiations.

The captain of a ship of the line was required to keep his place in the line of battle.

The captain of a liner is required to be nice to his/her passengers.


v   Said of a vessel when she leans sideways, for instance when her cargo has shifted.

See heel.

n   "a number of connected items or names written or printed consecutively, typically one below the other."

The items or names may be arranged numerically,  alphabetically,  by date or time,  or in any other way,  including randomly.

The skipper of any vessel will have lists of crew members,  of victuals,  of spares,  of jobs to be completed,  and many others.

Such lists may be check-lists:  semi-permanent lists which the skipper checks periodically.   The check-list for a compound task,  such as starting an engine,  might have items such as 'oil checks',  'battery checks',  'heaters on',  'stop control closed' which must be checked and completed in sequence.



A large passenger-carrying ship operated by a line,  or company.

Shipping lines are companies engaged in carrying passengers and cargo, often on established routes and schedules. Regular scheduled voyages on a set route are called "line voyages" and vessels (passenger or cargo) trading on these routes to a timetable are called liners.


A line with a thimble or a block,  often a snatch block,  on one end.

Falconer (in 1815) defined a lizard as “ . . An iron thimble,  spliced into the main bowlines,  and pointed over,  to hook a tackle to.

Smyth (in 1867) thought it was “A piece of rope,  sometimes with two legs,  and one or more iron thimbles spliced into it.

Layton (in 1987) described it as a "Rope or wire pendant with a round thimble at [the] unattached end."

Barnes (in 2015) suggested it was a Barber Hauler;   a lizard may be used as a Barber Hauler but the two are not synonymous,  and a lizard has other uses.

A lizard illustrated by Luce in 1891



Length over all;  the total length of a vessel.

See LOD.


The gruel,  or porridge,  served to the patients in the sickbay.

A loblolly boy was a surgeon’s assistant.


n   A means of raising or lowering boats from one level to another in a river or canal.

The lock chamber (or pen) is enclosed by gates at both the upstream and the downstream ends.   Paddles (slackers in the East of England) may be opened at the upstream end to allow water into the lock.  and opened at the downstream end to empty the lock.

v   To move a boat from one level to another by means of a lock.

n   A mechanical device,  operated by a key,  to prevent a door or gate being opened by those who have no key.

v   To secure a door or gate so that only those with a key can open it.



A box,  or chest,  or space with a door,  to stow small items.

Davy Jones' Locker,  at the bottom of the sea,  is where drowned sailors go.

The West Indian duppy (whence Davy) was a ghost or spirit:  Jones might be a corruption of the Biblical Jonah,  swallowed by a whale:   a locker is a receptacle for safekeeping.



Length on deck.   The length of a vessel excluding the bowsprit and rudder.

See LOA.


n   A place,  usually on the first floor above the workshop,  where sails are made or the lines of new vessels are laid out.   The floor is clear and smooth,  so that sails can be spread,  measured,  cut and sewn and so that the lines of vessels can be drawn on the floor.

v   To draw and fair the lines of a new vessel (on the loft floor).   It is done,  first,  to correct any mistakes in the architects table of offsets and,  second,  to prepare patterns for the moulds of the new vessel.

See Kopanycia



A device which measures how fast a boat is traveling through the water,  and how far it has sailed,  through the water,  since the log was last reset to zero.   (cf GPS)

The original device was,  literally,  a small log of wood attached to a length of knotted line.   The log of wood developed into a triangular board with a trip mechanism.

The 'marine surveyor' (see Falconer, 1815) was a metallic Y shaped device;  the leg of the Y was attached by a line to a mechanism on the ship;  the arms of the Y were asymmetric and rotated the device as it was towed through the water.   The mechanism on the ship struck a bell for every mile travelled through the water.

The Walker log (clearly derived from the marine surveyor) was a brass torpedo,  with fins,  which rotated at a speed proportional to the speed of the boat.   The rotations were recorded mechanically,  then electrically and electronically.

Log impeller:  a propeller,  or paddlewheel located underwater close to the boat's hull.   The movement of water causes the impeller to spin;  its spinning is translated electronically into speed (usually in knots) and distance travelled (usually in nautical miles) through the water.   The friction of the impeller bearings increases over time,  making the log less accurate.   The impeller becomes fouled with sedentary marine life over time,  making the log less accurate or even useless.

Acoustic (Doppler) log:   This device uses sound waves to measure speed through the water.

Tennis ball log:  a tennis ball (or similar) is attached to a fixed length of light line.   the ball is cast overboard and the time for the line to become taut is measured;  this is related arithmetically to the speed of the boat through the water.

The Knotstick has a spring balance in a cylinder and a disc in the water at the end of a light line.   The force on the spring is proportional to the speed of the boat through the water and is displayed on a scale.



A book in which is recorded (or logged) important or memorable details of a voyage.

Sometimes,  confusingly,  abbreviated to ‘log’ because the results of casting the log were logged in the logbook(!)

The deck log(book) records important moments (such as a change of heading,  or stopping the engine,  or passing a waypoint) in the navigation and management of the boat.   Most captains will ask for an entry to be made in the deck log(book) every half hour,  at the same time that the ship’s position is recorded on the chart.

An RYA logbook contains the syllabi for the various RYA grades and has space for the owner to record details of voyages and certificates.

A personal log(book) contains any information which the individual wishes to record.


The largest (most capable) of the boats carried on a ship of the line during the Age of Sail.


Several types of sailing vessel used by the Vikings in the 19 to 13th centuries for exploration,  warfare and trade.

Now applied by Viking Cruises to its long diesel-electric river cruising boats.



An imaginary line, circling the earth from pole to pole,   and measured in degrees (subtended at the centre of the Earth) from the Prime (or Greenwich) meridian of zero degrees.    Longitude measures angular distance East or West of the Prime Meridian,  and therefore measures time.

The earth rotates from West to East,  so that the sun rises in the East (looking down on the North Pole from space,  the earth appears to rotate anticlockwise relative to the sun).   The earth rotates once (360°) every 24 hours so that during each hour of time the sun appears to move 15° toward the West:   conversely,  each degree of apparent movement of the sun takes 4 minutes of time.

Before the launching of GNSS satellites sailors needed an accurate clock to be able to find their longitude;  they needed to know how many hours,  minutes and seconds they were ahead of,  or behind,  Greenwich Mean Time when the sun was exactly overhead.


A crewmember specifically assigned to look out for other vessels,  land,  objects in the water:  any potential hazards.


n   That part of an oar between the blade and the handle (grip);  The long part which operates in the crutch or rowlock.

n   The glow of light on the horizon which is the atmospheric refraction of the light of a lighthouse (or a coastal town),  but not the light itself.

v  To tower over,  vaguely and darkly;  to overshadow.

Loose cannon

If the breechings (ropes) which held a cannon in place were to break the cannon would roll around the deck.   As the wheels of its carriage became caught on obstructions,  and as the ship rolled and pitched,  its movement would be erratic and unpredictable.   Weighing several tons,  it would damage most things in its path,  and kill or maim anyone who got in its way.   It would take the combined efforts of several officers and many men with ropes to secure it.

A person who behaves erratically and unpredictably is often described as a loose cannon.


Low pressure

Atmospheric pressure less than 1013 millibars.   See Pressure,  High pressure.

Low water

The lowest tidal height of the tidal cycle.


A clumsy and unskilled person,  especially said of a landsman aboard ship.


Lubbers hole

Each mast of a square-rigged ship is in 3 or 4 parts.   The lowest part of the mast (called the mast) extends from the keel to the first of the tops.   The topmast is attached to the upper part of the mast.   The topgallant mast is attached to the upper part of the topmast.   The royal mast is attached to the upper part of the topgallant mast.   Each mast is supported by stays and shrouds.   The topmast is supported by stays and shrouds attached to the top,  which is a platform attached to the upper part of the mast  to carry the topmast shrouds out as far as possible.   The shrouds of the topgallant mast are attached to another,  higher top.    Each of the tops is supported,  from below,  by the futtock shrouds running from the outer edge of the top to the upper part of the mast below.

When climbing the mast a sailor climbs the shrouds to the lowermost futtock shrouds.   He then climbs outward,  his back downwards,  along the futtock shrouds to the edge of the top.   He then climbs the topmast shrouds to the next futtock shrouds,  and so on.

A lubber is one who,  afraid of the futtock shrouds,  climbs onto the top through the gap (the lubber’s hole) between the mast and the top.


An "Imaginary place of bliss,  where even lubbers are not a nuisance."   Layton.

Lubber line

The line within the compass casing,  but not on the card,  which is to be kept in line with the vessels centreline.   In conjunction with the card,  it indicates the vessels heading.

Alker Tripp called it the 'buffer's line'.

Heading of 200°C

n   The foremost edge of the sail.

The luff of a square-rigged sail was known as the fore-leech,  to distinguish it from the after-leech.

vb   To bring the boat closer to the wind.   Sometimes a skilled helmsman will luff to the wind to ease the tension on a sheet and allow it to be hauled.



A swift and weatherly craft used for coastal trading and fishing,   usually with two masts and carrying lugsails rather than square-rigged,  gaff or Bermudan sails.

The French chasse-maree (chasing the tide) were large,  fast luggers which carried fish from the fishing grounds to the markets.   They were also used for smuggling and piracy.

The Scottish Skaffie,  Fifie and Zulu were large luggers used for fishing.


The four-sided sail is set on a yard;  a fore-and-aft,  asymmetric,  yard,  not a square yard.

Folkard (in 1906) referred to standing lugs and balance lugs.

The standing lug sail is tacked down close to the mast.   The throat of the sail is forward of the mast,  at the forward end of the yard.   The peak is high,  at the after end of the yard.   There may,  or may not be a boom.   On one tack the sail and yard fall away to leeward of the mast;  on the other tack the sail and yard press against the mast.

Standing lug

Folkard's balance lug was what we would now (early 21st century) call a dipping lug.   The tack is held down to one of the bows.   The luff is more or less vertical,  with the throat held high by the yard.   The peak of the sail is high and there is no boom.   On changing tack,  the tack and yard are 'dipped' abaft the mast so that the sail and yard are always on the leeward side of the mast:   literally,  the tack is changed from one bow to the other.

In his 1906 treatise Folkard described an innovation where the foot of his balance lug (our dipping lug) was attached to a boom from the tack to the clew.   He gave it no name,  but this is what we now call a balance(d) lug.   The sail is hauled flat by a 'small tackle' from the boom to the heel of the mast;  this tightens both the luff and the leech of the sail,  and prevents the peak falling away to leeward.   Falconer (in 1815) described lugsails as having vangs (from the peak of the yard to a quarter),  but these are less necessary on a 21st century balanced lugsail.   The balanced lugsail has been described as 'self-vanging'.

A split lug is similar to our dipping lug (Folkard's balance lug) except that the sail is split vertically into two at the mast.   The luff of the after part may be laced to the mast;  the forward part is tacked to the stem or to a bow.   The clew of the forward part has sheets similar to the foresail sheets of a present day sloop.   Both parts of the sail are held at the head by the long yard.

More recent versions of the split lug have a boom attached to the tack of the 'foresail' and the clew of the after sail.   The tack of the after sail is bowsed down to the heel of the mast.

Originally it was possible to lace the luff of the after sail to the leech of the fore sail,  re-creating a dipping lug (Folkard's balance lug) when the crew did not expect to tack or haul close to the wind.

Split lug


A gunter rig has often been described as a form of lug;  its upper spar is often called a yard.

This is difficult to understand.   The gunter 'yard' does not extend forward of,  or across the mast and so is not a yard in any accepted sense.

Indeed, Falconer described the upper spar of a sliding gunter as a topmast.

Gunter rig


A sudden movement of the entire vessel in one direction,  caused by a large wave breaking against the rudder or the topsides.



Load waterline.   The waterline which is at the surface of the water when the vessel is correctly loaded.

For sailing yachts the LWL is usually fixed.   For cargo vessels the LWL is marked on the side of the vessel (see Plimsoll line) and varies with the temperature and salinity of the water.


Lying to

Waiting,  perhaps hove-to,  for another vessel or for a tide or for daylight.


John Starkie

October 2020

If you disagree,

or can't find a word

please let me know.