National Advisory Committee for Aeronatics was a United States federal agency founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved, and its assets and personnel transferred to the newly created National Aeronautics and Space Administration. Among other things, NACA produced the NACA duct, a type of air intake used in modern automotive applications, the NACA cowling, and several series of aerofoils which are still used in aircraft manufacturing. The aerofoil shapes are often used in hydrofoils, including centreboards, rudders and leeboards.
A solid metallic cylinder, much longer than wide, with a point at one end and a flat ‘head’ at the other. Used to join two pieces of wood. The point is placed on one piece of wood; the head of the nail is struck with a hammer and the point is driven through both pieces of wood. The friction of the nail in the wood holds the two pieces together; the friction between the two pieces prevents them sliding upon one another.
Some woods split readily along the grain when nailed; to prevent this a hole, slightly narrower than the nail, is bored through both pieces of wood and the nail is driven through the hole.
Traditionally, nails, in preference to screws, were used for joining planks to frames.
The narrow parts of a navigable waterway, especially a canal.
The English canals were built to a 7 foot gauge. Most of the waterways were wider, but the bridges, tunnels and narrow locks were no narrower than 7 feet. Fleets of 'narrow boats', up to 70 feet long, were built to carry cargo and passengers along the waterways and through the narrows.
40 ft by 7ft steel narrow boat on the river Cam
Several narrow boats at Jesus Lock in Cambridge. In the foreground Rosie is disembarking passengers
Nautical mile (nM)
In English usage a sea mile is, for any latitude, the length on the earth’s surface of one minute of latitude subtended at the centre of the earth. It varies from about 1,855.3 metres (6,087 ft) at the equator to about 1,849.1 metres (6,067 ft) at the poles , with a mean value of 1,852.3 metres (6,077 ft).
The international nautical mile was chosen as the integer number of metres closest to the mean sea mile, ie 1852m.
American use has changed recently. The glossary in the 1966 edition of Bowditch defines a "sea mile" as a "nautical mile". In the 2002 edition, the glossary says: "An approximate mean value of the nautical mile equal to 6,080 feet; the length of a minute of arc along the meridian at latitude 48°.".
When using charts based on Mercator’s projection, one minute of latitude is close enough to one nautical mile to be useful.
n The process and business of planning and following a route, in this context, by water. The person who navigates is a navigator.
v To navigate; to plan and follow a route.
n The British canals are known as navigations. The men who dug the canals were known as navigators (or navvies). Navvy is now a generic word for a labourer.
All vessels should carry navigation lights for use at night or in reduced visibility. They enable the vessel to be seen rather than to see. They enable other mariners to identify some characteristics of the vessel. Navigation lights are described in detail in the International Regulations for Preventing Collisions at Sea. (Beware of summaries and interpretations (like Wikipedia) which change the meaning)
Rule 23, “power-driven vessels underway” says “
(a) A power-driven vessel underway shall exhibit;
(i) a masthead light forward
(ii) a second masthead light abaft of and higher than the forward one . . .
(iv) a sternlight. . . “
There are modifications and exceptions.
Rule 25, “Sailing vessels underway . . .” says “
(a) A sailing vessel underway shall exhibit;
(ii) a sternlight.”
There are modifications and exceptions.
Someone who navigates.
See also Navigation, above.
A grid of fibres linked together by knots. Objects larger than the grid openings are contained by the net; smaller objects pass through.
Nets are used to catch fish larger than a certain size while allowing the fry to pass through.
Convective Cumulonimbus clouds form at the cold front, and are accompanied by rain and lightning.
n Lengths of braided rope used to attach the messenger, or voyol, to the anchor cable. The nippers were attached by the nipper-men (usually foretopmen) and held as the voyol pulled the cable. (A modern equivalent might be the short length of line often attached between the anchor chain and a cleat to prevent the rode snubbing the windlass) At the main hatch the nippers would be removed and the ship's children would carry them back to the manger board to be used again.
n An affectionate term for a young child.
The abbreviation for nautical mile.
When the sun is directly overhead.
Eight bells in the forenoon watch.
From any point on the Earth, True North is the direction in which the North pole lies.
The North and South poles are the tips of the axis on which the Earth rotates once every 24 hours.
From most points on the Earth, Magnetic North is not in the same direction as True North. The Magnetic North pole lies between Northern Canada and the True North pole, and moves toward Russia at about 40 miles per year.
It follows that a magnetic compass points to magnetic North and not to true North; the variation* between true North and magnetic North is different for almost every point on the Earth, and must be taken into account when navigating with a magnetic compass.
* not variance, which is a statistical value.
Not under command
IRPCS Rule 3 "General definitions" says
"(f) The term "vessel not under command" means a vessel which through some exceptional circumstance is unable to manoeuvre as required by these Rules and is therefore unable to keep out of the way of another vessel."
A vessel which has lost steering or propulsion is not under command.
In region A conical buoys are green and mark the starboard side of a channel when returning to harbour: they are rarely called 'nuns'.
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