One of twin trawlers that spread the same net over a wide track spacing.

Related Terms

OBSTRUCTION

An object such as a wreck, net, etc., which blocks a fairway, route, etc.

SLING

Rope, net, and any other means for handling general cargoes

COMMERCIAL TRAWLER

A fishing boat that uses a trawl net or dragnet to catch fish.

CENTER OF EFFORT

The point of origin of net aerodynamic force on sails, roughly located in the geometric center of a sail, but the actual position of the center of effort will vary with sail plan, sail trim or airfoil profile, boat trim, and point of sail. Also known as center of pressure.

INTERNATIONAL TONNAGE CERTIFICATE

A certificate issued to a shipowner by a government department in the case of a ship whose gross and net tonnages have been determined in accordance with the International Convention of Tonnage Measurement of Ships. The certificate states the gross and net tonnages together with details of the spaces attributed to each.

LONGSHORE CURRENT

A current paralleling the shore largely within the surf zone. It is caused by the excess water brought to the zone by the small net mass transport of wind waves. Longshore currents feed into rip currents.

NRT

Net registered tons. See Tonnage (Net)

TONNAGE OPENINGS

Nonwatertight openings in the shelter deck and in the tween deck bulkheads immediately below in order to exclude spaces from tonnage measurement and thus obtain reduced gross and net tonnage. The openings could be closed by nonwatertight wood shifting boards or metal covers meeting the tonnage and load line regulations

NET TONNAGE

Net tonnage is the gross tonnage less certain additional spaces such as crew and officer spaces, chart room, and a percentage of the propelling machinery spaces; also see deadweight, displacement, light and displacement, loaded

NPSH

This is the abbreviation for Net Positive Suction Head. This is an expression used in cargo pumping calculations. It is the pressure at the pump inlet and is the combination of the liquid head plus the pressure in the vapor space.

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