Anchoring — types, scope, holding ground

USCG Boatswain Manual Ch. 2 §2.2

USCG Boatswain Manual Ch. 2 §2.2 — Mooring and Anchoring Anchor scope — the ratio of rode length to water depth plus bow height — should be 7:1 in good holding ground and calm conditions, 10:1 in storm conditions. Less scope reduces holding power; the rode must rest along the bottom for the anchor to set.

USCG Boatswain Manual Ch. 2 §2.3

USCG Boatswain Manual Ch. 2 §2.3 — Mooring and Anchoring Common anchor types: Danforth (lightweight, high holding power in sand and mud, poor in rocks); plough (CQR, Delta — good general-purpose, harder to stow); Bruce (claw — good in weeds); mushroom (permanent moorings); fluke (small craft).

33 CFR §164.19

§ 164.19 § 164.19 Requirements for vessels at anchor. The master or person in charge of each vessel that is anchored shall ensure that: (a) A proper anchor watch is maintained; (b) Procedures are followed to detect a dragging anchor; and (c) Whenever weather, tide, or current conditions are likely to cause the vessel's anchor to drag, action is taken to ensure the safety of the vessel, structures, and other vessels, such as being ready to veer chain, let go a second anchor, or get underway using the vessel's own propulsion or tug assistance. [CGD 74-77, 42 FR 5956, Jan. 31, 1977]

NAVEDTRA 14067 §4-3

NAVEDTRA 14067 §4-3 — Ground tackle and anchoring from the deck Ground tackle is the anchor, chain, and associated gear a ship uses to anchor. On the forecastle the chain leads from the chain locker up through the spurling pipe, over the wildcat of the anchor windlass, through the hawsepipe, and out to the stockless anchor stowed in the hawsepipe. Holding the anchor and chain when not heaving are the brake on the wildcat and, more securely, a chain stopper — a pelican hook or riding pawl that takes the strain off the windlass while the ship rides to her anchor. Anchor chain is made up in shots (15 fathoms, 90 feet, each), joined by detachable links, and marked by a paint-and-wire color code at each shot so the crew can call how much chain is out as it runs. Anchoring: with the anchor walk…

NAVEDTRA 14343 §4-1

NAVEDTRA 14343 §4-1 — Ground tackle components — anchors, chain, and appendages Ground tackle is the equipment used in anchoring and mooring: the anchor, anchor chain (cable), connecting fittings, and the machinery that handles them. The stockless anchor is standard on most vessels because its crown and pivoting flukes let it stow snugly in the hawsepipe. When the anchor is let go and the ship drags astern, the flukes trip downward and dig into the bottom; holding power comes from the flukes biting the ground, not from the anchor's weight alone. Older patterns include the old-fashioned (stock) anchor and the lightweight (Danforth) type with large pivoting flukes and high holding-power-to-weight ratio. Anchor chain is measured in shots, each shot being 15 fathoms (90 feet). Shots are joine…

NAVEDTRA 14343 §4-2

NAVEDTRA 14343 §4-2 — Anchors and holding power The holding power of an anchor depends on the anchor type and weight, the nature of the bottom, and the scope of chain veered. An anchor holds best when the pull on it is horizontal, which is why scope matters: with more chain out, the catenary (the sag of the heavy chain) keeps the shank pulling parallel to the bottom so the flukes stay buried. A short scope lifts the shank and can break the anchor out. A common working rule of thumb is a scope of five to seven times the depth of water (measured from the hawsepipe to the bottom), increased in heavy weather. Good holding bottoms are firm mud, clay, and sand; poor holding bottoms are rock, coral, loose shingle, and very soft ooze. The weight of chain on the bottom also adds holding power and …