Anchor cable is twisted around or it has been fouled.

A line, wire, net, etc., is wound round the propeller.

A term used to describe the growth of marine plants and animals on man-made structures in the sea.

The rate at which the heat transfer surfaces in a boiler become fouled. Fouling occurs due to the exhast gases passing over heat transfer surfaces.

A four-stroke engine is an internal combustion engine in which the piston completes four separate strokes while turning the crankshaft.

Four-terminal sensing (4T sensing), 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements than the simpler and more usual two-terminal (2T) sensing. The technique is called Kelvin sensing.

This class of biofuels includes electrofuels and solar fuels.

Fracture is the separation of an object or material into two or more pieces under the action of stress.

Fracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials.

A term used to define one of the transverse members that constitute the riblike part of the skeleton of a ship. The frames act as stiffeners, holding the outside plating in shape and maintaining the transverse form of the ship.

The fore-and aft distance, heel to heel, of adjacent transverse frames.

Arrangements of stiffeners used to support hull plating. Two different types of framing are in general use or may be combined. They are longitudinal, transverse and combined framing.

The Francis turbine is a type of water turbine that was developed by James B.

Free cooling is an economical method of using low external air temperatures to assist in chilling water, which can then be used for industrial processes, or air conditioning systems.

Free energy suppression is a conspiracy theory that technologically viable, pollution-free, no-cost energy sources are being suppressed by government, corporations, or advocacy groups.

In physics, a free surface is the surface of a fluid that is subject to zero parallel shear stress, such as the interface between two homogeneous fluids, for example liquid water and the air in the Earth's atmosphere.

When a tank is partially filled, the liquid’s centre of gravity position will change as the ship is inclined. Liquid in partially filled tank always decreases the initial metacentric height GM, righting lever GZ, and angle of vanishing stability.

Freeboard is the distance measured from the waterline to the upper edge of the deck plating at side of the freeboard deck amidships.

Normally, the uppermost complete deck exposed to weather and sea, which has permanent means of closing all openings in the weather part thereof, and below which all openings in the sides of the ship are fitted...

see Load line mark.