U-boat – First and Second World War German submarine.
Ullage –The distance from the top of a tank to its contents top surface.
Ulloa’s Circle – White ‘rainbow’ seen in fog, or at night.
Ultimate Strength – The stress, usually expressed in tons per square inch, that exactly balances the resistance to fracture, or rupture, of a member or material under stress. Sometimes defined as the minimum load that will cause fracture or rupture.
Ultra High Frequency (UHF) – Radio transmission frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz).
Ultra Large Crude Carrier (ULCC) – Largest ship types with sizes above 320,000 dwt. Related Article: How to Identify Oil Tanker Sizes- Handymax, Panamax, Aframax, Supertankers.
Ultraviolet – Electromagnetic radiation with wavelengths between visible light and x-rays.
Umbra – The shadow cast by the Earth or Moon where the Sun is hidden. The conical shadow that an eclipsing heavenly body has on that side of it that is remote from the light source. Occasionally applied to the dark area of a sunspot.
Umbrella – The cone-shaped shield at the top of the funnel.
Una Rig – Single sail spread to a yard or gaff and set on a mast stepped well forward. Used for small craft, and in Norfolk wherries.
Unbend – Untie. Cast loose.
Unbi –. To cast off the upper securing turns of the cable from the bits, leaving the riding turn on.
Uncertainty Phase – A SAR situation wherein doubt exists as to the safety of an aircraft or a marine vessel, and of the persons on board.
Under Bare Poles – Said of a vessel running before the wind with no sail set; the motion of the vessel being due to wind pressure on her stern and upper works.
Under Canvas – Under sail.
Under Deck Tonnage – Tonnage based on space below tonnage deck, each 100 cu. ft. counting as one ton. Measured from top of floors—or ceiling, if any— to underside of tonnage deck.
Under Foot – Said of anchor when it is under ship’s forefoot, and cable is nearly up and down.
Under Power – The condition of a vessel when mechanical power is being used to propel her through the water.
Under Protest – Applied to an action, payment, or signature when it is not freely rendered but is qualified by a statement made before the rendering. It thus leaves the matter open to dispute.
Under Sail – Having sail set. Making way through the water by action of wind on the sails.
Under the Lee – Under the shelter of an object to windward.
Under Way – Not attached to the shore or the ground in any manner. Usually, but not necessarily, moving through or making way through the water.
Under Weigh – Under way.
Undercurrent – Moving water that is below the surface and having a direction and/or rate that differs from that of surface water.
Under-deck Tonnage – The total internal capacity of a ship measured in register tons from the top of the floors to the tonnage deck. This includes all spaces above the floors. The tonnage deck is the upper deck in all ships with less than three decks, and the second deck from below in all other ships. Only complete decks are counted.
Undergird – To pass hawsers under a vessel and heave them taut across the upper deck. Done when seams show signs of opening through strains on mast, or through heavy weather. Also called Trapping’.
Undermanned – Said of a vessel when she is short of personnel she should have in the prevailing circumstances. Having insufficient crew.
Underrun – To follow up the lead of a submerged rope or wire by putting rope over a boat, and hauling the boat along it.
Undersail – To sail in the lee of a shore or headland.
Underset – The seaward setting current that moves under the surface water that is being driven shoreward by wind. Undertow.
Undertow – Water flowing to seaward under surf. Subsurface current pulling out to seaward.
Underwater Body – That volume of a vessel’s hull that is immersed at a given draught.
Underway – Means that a vessel is not at anchor, or made fast to the shore, or aground.
Underwrite – A person who insures, wholly or in part, a marine risk by stating the amount for which he is liable in the policy, and then signing the policy.
Underwriting – Contracting to make good, wholly or in part, a marine loss; signing to this effect at the foot of a policy of marine insurance.
Undock – To clear a dock.
Undulation – A rising above and a falling below a mean level in the manner of a smooth wave, or ripple.
Undulatory – Having an up and down movement, together with a sidewise movement, but without any translation of the particles of the fluid.
Unfurl – Cast loose a sail by letting go the gaskets.
Uniform System of Buoyage – Buoyage system in which the shape and/or colour of any buoy or beacon has a definite significance. Most maritime nations had a uniform system of their own. International system introduced in 1977. Related Article: The IALA Buoyage Systems – Seafarer’s Aids to Navigation.
Union – The device in the upper canton of an ensign or flag. Short name for the Union Jack, or the stars device of USA ensign.
Union Flag – Union of an ensign when flown by itself.
Union Hook – Swivelled cargo hook with ring carrying two swivels for connection to the two runners of a union purchase.
Union Jack – Device for a flag that forms the inner upper canton of a national ensign, or is used separately. Particularly applied to the British jack, which contains the crosses of Saints George, Andrew, and Patrick.
Union Purchase – Method of rigging cargo derricks so that they need not be moved while loading or discharging a hatch. One derrick plumbs the hatch, the other derrick plumbing the loading or discharging point overside. Runner of each derrick is shackled to the same cargo hook. Precision in plumbing results.
Unitization – Consolidation of a number of cargo articles into a larger whole to ease handling.
Universal Time – Alternative name for ‘Greenwich Mean Time’.
Universal Time Coordinated (UTC) – Also called Coordinated Universal Time. the time at Greenwich, 0 degrees longitude.
Unload – To discharge, or remove, cargo.
Unmanned Machinery Space (UMS) – a decked propulsion machinery space that under normal operating conditions is not occupied or is intermittently occupied.
Unmoor – To cast off hawsers by which a vessel is attached to a buoy or wharf. To weigh one anchor when riding to two anchors. To remove a mooring swivel when moored to two cables.
Unreeve – To pull the ropes of a tackle clear of a block.
Unrig – To remove rigging. To take off tackling or fittings.
Unseaworthy – Said of a vessel when she is not in all respects fitted to perform her contracted tasks. In a limited sense it is used to denote a vessel not fit to face the hazards of the sea; in a larger sense, particularly as regards insurance interests, it includes her incapability of carrying cargo properly, her failure to have officers that are properly qualified, her lack of navigational aids, and other similar negligences.
Unserviceable – a tag on broken equipment.
Unsettled – Changeable.
Unship – To remove from a ship. To remove an item from its place.
Unstable Air – Parcels of air with uneven temperature and humidity mixing.
Unstable Equilibrium – A ship which, when forcibly inclined, heels still further, and may capsize, is in unstable equilibrium.
Unukalkay – Name of star ‘Cor Serpentis’, or α Serpentis.
Unwatched – Said of a navigational beacon light that is shown from a position at which there is no permanent attendant.
Up – To put the helm up is to move tiller to windward. Applied to sails, means to hoist the sail.
Up Anchor – Weigh anchor. Hoist up the anchor. To retrieve the anchor.
Up and Down – Said of cable when it extends vertically and taut from anchor to hawsepipe. An anchoring term used to indicate that the anchor cable is leading vertically from the hawse pipe. Related Article: Safe Anchoring Techniques – How to Drop the Ship’s Anchor Properly.
‘Up Right and Down Straight—Like a Yankee Main Tack’ – Old phrase of a seaman when boasting of his candour. American ships, at one time, had comparatively short main tacks.
Up Together – Order to the oars, on both sides of a boat, to give way together.
Updraught – A rapid vertically moving parcel of air found in thunderstorms.
Upper Berth – A bunk suspended above another.
Upper Deck – In ships with more than one continuous deck, is the highest continuous deck.
Upper Topsail – The square sail set above the course sails (lowest) and lower topsail of a sailing ship.
Upper Transit – Passage of a heavenly body across observer’s meridian.
Upper Works – All erections above the freeboard deck. A vessel’s superstructure above the weather deck.
Upriver – See upstream.
Upside Down Ensign – Old signal of distress.
Upstream – Towards the source of a river; against the flow.
Uptake – Enclosed casing that takes furnace gases from ends of boiler tubes to base of funnel.
Upwelling – Water currents rising from the depths.
Upwind – To windward.
Uranography – The mapping of heavenly bodies on a chart or star globe.
Uranus – Planet between Saturn and Neptune. Not used in navigation. Discovered by Herschel, 1871. Has five small satellites.
Ursa Major – ‘The Great Bear.’ Most brilliant of the northern constellations. Contains seven bright stars: Dubhe, Merak, Phecda, Megrez, Alioth, Mizar, and Alkaid; the first two point to Polaris. This constellation is also called the ‘Plough’, ‘Dipper’, ‘Charles Wain’, and ‘Waggon and Horses’. It has been called the ‘Corn Measurer’ by the Chinese, and considered as a hippopotamus by the Egyptians.
Ursa Minor – ‘The Lesser Bear.’ Northern constellation containing Polaris, α Ursae Minor.
Uvroe, Uvrou – Euphroe.