X – Code flag; Stop carrying out your intentions and watch for my signals. The traditional signature of an illiterate seaman. Morse code; ▬ ● ● ▬.
X-band – A radar with 3cm wavelength transmitting at 10,000MHz.
Xebec – Small three-masted, lateen-rigged trading vessel of Mediterranean Sea and Iberian coast. Differs from a felucca by having a square sail for running.
Xenon – A heavy, colourless and odourless inert gas found in the atmosphere.
Xiphias – The common swordfish of the Mediterranean. Has no central fin.
XTE (Cross Track Error) – on GPS “steer to screen”, the lateral off course error displayed when proceeding to a position.
Y – Code flag; I am dragging my anchor. Morse code; ▬ ● ▬ ▬.
Yacht – Vessel built for pleasure cruising, or for racing. Earliest English yacht would appear to be one built, at Cowes, for Queen Elizabeth in 1588. Charles II was given a vessel (‘Mary’) by the Dutch; this introduced the word ‘yacht’— meaning ‘chaser’— to the English language.
Yacht Club – Association of yachtsmen to further the interests of yachting, to arrange races and to frame rules and regulations for the good order of the sport. Oldest is the Royal Cork Yacht Club, founded 1720.
Yacht Codes – Signal codes adopted, or devised, by yacht clubs before introduction of the ‘International Code’ of 1857. Most of the important clubs had their own codes. Acker’s ‘Universal Yacht Signals’ was the first common code.
Yachtsman – One who owns or sails a yacht.
Yankee Jib Topsail – Balloon jib topsail cut very high in clew..
Yanky – Dutch sailing vessel of small size, and clumsy in a sea way.
Yarage – Handiness and general manoeuvrability of a vessel.
Yard – Spar fitted across a mast, primarily to extend the head of a sail and to extend the foot of a sail above it, if any. It can be angled so that sail can be trimmed to a prevailing wind. In modern vessels its main purpose is to carry signal halliards. Ship building or repair facility.
Yard and Stay – Name sometimes given to ‘union purchase’ method of rigging two derricks for loading or discharging overside. Is a relic of sailing ship seamanship, when one tackle was put on a stay—over a hold—and other tackle was put at yard arm, so plumbing loading, or discharging, point.
Yard Arm – That part of yard that lies between the lift and the outboard end of the yard.
Yard Arm and Yard Ann – Said of two square-rigged ships that are so closely alongside one another that their yard arms are nearly touching.
Yard Arm Iron – Boom iron fitted at yard arm to take a studding sail boom.
Yard Rope – Rope used for sending a yard up or down.
Yard Tackle – Purchase rigged on yard of square-rigged ship for lifting heavy weights in or out.
Yarely – Smartly. Quickly.
Yarn – Threads that are laid up and form part of a twine, line, or strand. Fibres that are twisted together to form a rope.
Yarrow Boiler – Water-tube boiler consisting of two lower water drums and an upper steam drum, these being connected by water tubes. In the triangle thus formed is the furnace, which heats the water drums, tubes, and lower side of steam drum. Water level is about halfway up steam drum.
Yaw – The rotary motion of a vessel resulting from her pivot at the centre point. The bow swings successively form left to right.
Yawl – Decked sailing boat having main mast and a small mizen mast that is abaft tiller. Sheet of mizen sail is led to block at end of a bumpkin clamped in fore and aft line at transom. 2. Original name of jolly boat of Royal Navy.
Year – Unit of time based on one revolution of Earth around Sun. It has varying values depending on point of definition used, and on mode employed. See Anomalistic, Bissextile, Civil, Equinoctial, Leap, Mean Solar, Sidereal, Solar, and Tropical years. The year in common use is the Civil Year.
Yellow Jack – Originally meant ‘yellow fever‘. Later, applied to the yellow flag flown by a vessel when in quarantine.
Yeoman – Rating in Royal Navy who assists a store-keeping officer, or navigating officer. 2. A yeoman of signals.
Yeoman of Signals – Petty officer in Signals and Communications branch of Royal Navy.
Yield Stress – The stress limit of a material at which plastic (permanent) strain under load commences.
Yoke – Brass or wooden fitting placed transversely on head of rudder of a boat. Forms lever when steering with yoke lines. 2. Lower cap of an upper mast.
Yoke Lines – Lines leading to extremities of a yoke and with ends in stern sheets. Used for controlling rudder except when under sail.
Yonker – Young foremast crewman.
York Antwerp Rules – Codified rules for the adjustment of claims under General Average. First issued 1890, revised and extended 1924 and 1974. Name derives from the cities in which the conferences were held.
Young Flood – The beginning of flood tide, or of the current due to it.
Young Gentleman – Name sometimes given, customarily, to midshipman in Royal Navy.
Young Person – Legally, one who is not less than 14 years of age, and not more than 18 years of age.
Youngster – Young person.
Younker – Variation of ‘youngster’.
Yourkevitch Form – Hull form designed for fast vessels, and used in construction of ‘Normandie’. Fore body lines are narrowed, and hollowed at a waterline position that depends on vessel’s designed speed. Stern sections are somewhat flat and wide.
Z – Code flag; I require a tug. By a fishing vessel, I am shooting nets. Sound signal; I intend overtaking on your port side. Morse code; ▬ ▬ ● ●.
Z bar – A metal bar with cross section in the shape of a Z.
Z drive – A propulsion drive train where the prop shafts are horizontal, parallel and driven by a vertical engine output shaft.
Z flag + four numerals – Code flags; Time UTC.
Zapato – Small Peruvian rowing boat.
Zaurac – Star ζ Eridani.
Z-Bar, Zed Bar – Rolled steel section of Z-shape, but with right angles.
Zenith – Point in the heavens vertically above an observer. Elevated pole of rational horizon.
Zenith (Magnetic) – That point in heavens indicated by a line passing longitudinally through a freely-suspended magnetic needle.
Zenith (Z) – A point in the celestial sphere directly above a terrestial observer.
Zenith Distance – Arc of a vertical circle intercepted between an observed point and the zenith.
Zenith Distance (ZD) – An angular distance from directly above the observer and a celestial body. It is 90 degrees less the body’s altitude.
Zenith Parallel – Small circle of celestial sphere, parallel to horizon and passing through all points having the same zenith distance.
Zenith Sector – Astronomical telescope that is weighted and pivoted, and fitted with an attachment for determining the true vertical. Used for measuring zenith distances.
Zenithal Projection – Projection of surface of a sphere by lines from centre to a plane that is tangent at the zenith.
Zephyr – A warm, light westerly breeze.
Zephyrus – Westerly wind of ancient Greece. See classical winds.
Zero – That point, in a scale, that is supposed to have no value, and from which the values of other points are reckoned. On one side of zero the values will be positive and negative on the other side.
Zig – Historic Polish fishing boat.
Zigzag – To make good a mean course by steering short courses on either side of it. Done in wartime to make submarine attack more difficult. May be done, in normal circumstances, when searching for an inconspicuous object.
Zigzag Clock – Clock fitted for use when zigzagging. Special mechanism is incorporated to ring a bell when a course has been steered for a pre-arranged time.
Zigzag Sailing – Sailing on alternate tacks.
Zinc (Zn) – A metal used for rust proof plating (galvanising), sacrificial anodes and a component of the alloy of brass (zinc and copper). See de-zincification.
Zinc Protector – Slab of zinc attached to underwater body of a ship to prevent steel of hull becoming electro positive to copper or copper alloy fittings exposed to salt water. Galvanic action breaks down zinc slabs, which is renewable. See ‘Cathodic Protection’.
Zodiac – Twelve signs, or constellations, through which Sun travels in his annual course along the Ecliptic.
Zodiac – A belt of the heavens eight degrees each side of the ecliptic divided and named by the ancients into twelve patterns of stars called the signs of the zodiac.
Zodiacal Constellations – Those constellations lying in a zone about 8 1/2° on either side of Ecliptic, and from which the Signs of the Zodiac take their names. The signs do not now agree with the constellations of the same names; this being due to precession of the equinoxes.
Zodiacal Light – A long, tapering, and narrow beam of faint light that is sometimes to be seen coming upwards from Sun before he rises, or after he has set.
Zonal Flow – Atmospheric circulation following parallels of latitude.
Zonda – A wind of the eastern slopes of the Andes during May and November. See foehn
Zone – Area between two parallel circles of a sphere. In a more general sense, it may mean an area on the surface of a sphere. See Seasonal Zones.
Zone – Defined areas of the globe, being North or South, frigid, torrid or temperate
Zone of Silence – Area in which a sound is inaudible although it may be heard all round the area. The cause of it is not known. Quite frequently noticed in connection with fog signals of lighthouses.
Zone Time – Time kept at sea for official purposes. Sea areas are divided into sectors (termed ‘zones’) that extend 7 1/2° on either side of the prime meridian, and of all meridians of 15° or a multiple of it. Each zone keeps a time that is one hour different from the zone on either side of it. Each zone, therefore, has a time that is an integral number of hours different from Greenwich Mean Time, and the zone is named by this number. Easterly zones prefix a minus sign, westerly zones prefix a plus sign, to the zone number. The zone number, when applied to the zone time, and using its prefixed sign, will give Greenwich Mean Time. Zone+ 12 and zone—12 meet at the Date Line.
Zone time (ZT) – The local time on the Earth’s surface calculated as plus or minus that at Greenwich, (UTC). The earth is divided into 24 one hour zones of 15 degrees longitude each.
Zooid – Invertebrate that multiplies by budding.
Zoophyte – Coral or sponge.
Zooplankton – Microscopic drifting marine animal life.
Zoospore – A fungal or algal spore.
Zubenelg – Star β Librae. S. H. A. 131°; Dec. S09°; Mag. 2.7.
Zubenelgenubi – Star α Librae. S. H. A. 138°; Dec. SI 6°; Mag. 2.9.
Zubenesch – Old name for star α Lyrae.
Zugites – The middle tier of oarsmen in an ancient Greek trireme.
Zulu – Scottish east coast fishing vessel. Plumb stemmed with raked sternpost Scottish 19th century sailing but later motorised herring drifter.
Zygaena – The genus to which the hammer-headed shark (Zygaena malleus) belongs.