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Mooring

A seaman aboard the *Fougueuse* throws a a heaving line.

A mooring (also moorage) is usually an arrangement by which a nautical vessel (or aircraft) may be held stationary. The vessel is then said to be "moored". The word also refers to the place where the vessel is moored (particularly if the place is especially convenient or if it is especially designed), the act of bringing the vessel into the mooring place and making it fast there, or the permanent anchor at the bottom of the waterway that hold a vessel in place.

Strictly, however, mooring refers to any device used to hold secure any object by means of cables, anchors, or lines.

Moorage either refers to the place one commonly moors ones vessel, the act of keeping a vessel moored in a marina, with a daily or monthly fee paid for occupying a berth of a given size, or the fee paid in such a case.

A nautical mooring is typically either an immobile object (AKA. permanent anchor) located on the bottom of a waterway with a rode (line, cable, or chain) running to the surface where a float makes it easy to pick up and make fast to from a vessel. It may also be a set of bollards, rings, or cleats to which a vessel may be made fast at a quay, dockside, or (on inland waterways) the river bank or towpath.

Permanent Anchor Mooring

Of the permanent anchor type of mooring there are four basic types; dead weight, mushroom, screw in, and triple anchor. These moorings are used instead of temporary anchors because they have considerably more holding power, cause less damage to the marine environment, and are convenient. They are also commonly used to hold dock floats in place.

Example: On The Great Barrier Reef off the Australian coast, a vast number of public moorings are set out in popular areas where boats can moor. This is to avoid the massive damage that would be caused by many vessels anchoring in close proximity.

Dead weight moorings are the simplest kind of mooring generally made as a large concrete block with a rode attached which resist movement with sheer weight and to a small degree by settling into the substrait. The advantages are that they are simple, cheep, If they drag in a storm they still hold well in there new position afterwards, and are better suited to rocky bottoms where other mooring systems don't hold well. The disadvantages are that they're heavy, bulky, and awkward.
Mushroom moorings are the most conventional moorings for mud and silt substraits as they are shaped like an upside down mushroom which can bury itself in these materials quite readily. The advantage is that it has up to ten times the holding power to weight ratio as compared to a dead weight mooring. The disadvantage is that they're more expensive then dead weight moorings, don't hold well on rocky or pebbly substraits, and they take time to settle in before reaching full holding capacity.
Screw in moorings a quite modern method the screw in mooring is a shaft wide blades winding around it so that it can be screwed into the substrait. The advantages are that it gets the best holding power to weight ratio in fact weight isn't really an issue as an eight foot screw can withstand 20,800 pounds of force without braking out in a muddy substrait which is about ten times as much force as a 2,100 pound concrete dead weight can take (Helix Mooring Systems inc.,) also being so small they're relatively cheap. The disadvantage is that it generally takes a diver to install and maintain them.
Triple anchor mooring systems this "'unconventional' mooring system" (Chapman) uses three lightweight anchors (AKA. Danforth) set in an equilateral triangle and all chained to a common center from which a normal rode extends to a mooring buoy. The advantages are that it's light, relatively cheap, and holds quite well with any direction of force. The disadvantage is that it's difficult to install.

rode system

The basic rode system is a line, cable, or chain several times longer than the depth of the water running from the anchor to the mooring buoy, the longer the rode is the shallower the angle of force on the anchor (it has more scope.) A shallower scope means more of the force is pulling horizontally so that ploughing into the substrait adds holding power. By adding weight to the bottom of the rode, such ass by using a length of heavy chain, the angle of force can be dropped further. unfortunately this scrapes up the substrait in a circle around the anchor. To avoid this issue a buoy can be added along the lower portion of rode to hold it off the bottom.

The two-headed mooring bitt

Line placing after mooring. The ship is attached to the large round bollard on the shore (right, behind)

The widespread construction for mooring a ship by hand is the two-headed mooring bitt. The rope is pulled over the bitt, pulling the ship to the mooring place this way. In the second step, the rope is tied to the bitt, as shown. This tie can be put and released very quickly. In quiet conditions (a lake) two men (each with his own bitt) moor the 260 t ship in several minutes.

References

Chapman, Charles F.; Chapman Piloting: Seamanship and Small Boat Handling, 61st edition, 1994 St. Remy Press; ISBN 0-6881683-3

External Links

MooringExchange.com, Free listings of available moorings for boaters
[1], Helix Mooring Systems inc.

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Category:Boats