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Natural Ventilation. See Ventilation, Natural.

Nautical Mile. A distance approximately equal to 6,080 feet, or exactly one-sixtieth of a degree on the equator.

Naval Architect. Primarily, one responsible for the design and alteration of ships or for the investigation and carrying out of important projects in connection therewith. Frequently he is charged with responsibility for the maintenance of vessels in service, for valuation proceedings, for the construction of new vessels, etc., though these duties do not fall strictly within his province. The Naval Architect is responsible for the strength, stability, speed, trim and weight of the vessel in hand. It is, therefore, necessary that he should have an adequate knowledge of the principal items entering into the vessel such as machinery, cargo, fittings, etc., although he is concerned with the details of hull, fittings, etc., only.

Naval Constructor. Primarily, one responsible for the building and maintenance of ships or for the investigation and carrying out of important projects in connection therewith. He is sometimes charged with responsibility for the design of new vessels and for the alteration of those already in service. The Naval Constructor is responsible for the proper interpretation of plans and specifications, for the fabrication of the vesselís structure, installation of fittings, and testing of parts, systems and equipment in accordance with the specifications and the best practice both as to general intent and as to detail.

Navigating Bridge. See Bridge, Navigating.

Navigating or Flying Bridge. See Bridge, Navigating.

Navigraph. A type of Sextant.

Navisphere. A navigational celestial globe used in sailing schools in the late 19th and early 20th century, also sometimes employed on ships for quick identification of the stars.

Needle Valve. See Valve, Needle.

Net Tonnage. See Tonnage, Net.

Netting. Nets made of either fiber or wire rope and used as a covering for hawse pipes, chock openings, etc., as landings in cage masts, and under spars in lieu of foot-ropes.

Neutral Axis. Consider the cross section of a beam, girder, or ship which is stressed by bending. The extreme fibers on one side are in compression while the extreme fibers on the other side are in tension. At some axis between them exists neither tension nor compression. This is termed the neutral axis for the section. The neutral axis passes through the center of gravity of the section.

Neutral Equilibrium. See Equilibrium, Neutral.

Newel Post. An ornamental upright pillar about which winding stairs are formed.

Nibbing Plank. See Plank, Margin.

Nipple. A piece of pipe, having an outside thread at both ends, used for making pipe connections. Close nipples are those that are threaded throughout. Short nipples are those having a small amount of unthreaded surface between the threaded ends. Shoulder nipples are those having a shoulder between the two pipe threads. Sub-nipples are those having different threads on the ends. Long nipples are those having a length of from 4 to 12 inches. Reducing or swaged nipples are those having one end smaller in diameter than the other.

Nocturnal. A navigational instrument of metal or wood for observing certain stars relative to the pole star in Ursa Minor, and thus discovering the hour at night.

Non-Condensing Engine. See Engine, Non-Condensing.

Non-return Valve. See Valve, Non-Return.

Nosing. The molding or part of the tread of a staircase which projects over the riser.

Nozzle, Boiler. A fitting with a finished face and fitted with stud bolts for the attachment of a pipe line to a boiler.

Nozzle, Turbine. See Turbine Nozzle.

Nut Facing Machine. A machine designed to automatically face and machine finish nuts.

Nut Machine, Hot Press. A machine designed to automatically heat and forge nuts from bar stock.

Nut of Propeller Shaft. A nut attached to the after end of a propeller shaft to prevent the propeller from backing off.

Nut Tapper. A machine similar in design and operation to a drilling machine, provided with tools for tapping the thread in nuts. Such machines are made with single or multiple spindle.


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