Ground Tackle

Ground tackle is everything between the boat and the sea floor. This includes the anchor, the cable, and in some instances, the windlass. Here we will look at the anchor and what holds the anchor to the windlass.

Stock Anchor

Also called a fisherman, traditional, kedge, Admiralty, or Navy style anchor, this is one of the oldest anchor designs. The stock is designed to prop up one end of the anchor so that the flukes always bite into the seabed. The primary characteristic that helps a stockless anchor hold is its weight. Unlike most anchors, it is effective in grass or rocks, but compared to more conventional anchors, little else. This is the anchor you will be asked to identify the parts of most frequently during deck examinations.

Stockless Anchor

Also called patent anchor, or Mk. 2. This is typically used by large vessels because the omission of the stock allows the anchor’s shank to be housed in the hawsepipe.

Danforth

A more recent anchor, this style proved popular with recreational boaters for its improved weight to holding ratio and ease of stowing due to the swiveling flukes.

Mushroom

Ideal for holding in soft mud where others may drag, its primary ability to hold comes from its sheer weight. This is typically only seen on permanent or long-term moorings or large vessels that typically stay in one spot.

Modern Anchor Design

There are a plethora of anchors on the market today, each offering distinctions and improvements on the latter. The prudent skipper will research the market options available before making a selection of ground tackle.

Fluke Angle

An anchor resists lateral movement by using its flukes to dig into the seabed. The angle at which the anchor flukes penetrate the soil is the fluke angle; this should be between 30 degrees for softer mud and 50 degrees for harder seabeds. Because the flukes cannot be adjusted the correct anchor should be selected beforehand.

Effects of Seabeds and Anchoring

Tripping defects in anchors frequently occur in soft soils, such as silt or soft mud. Grass can pose a hazard to some anchors designed to dig into sandy bottoms. Other seabeds that pose poor holding include shale and rock. With rocks most anchor designs will not gain good purchase while paradoxically being vulnerable to getting fouled and becoming irrecoverable. The first attempt to clear the anchor should be made by reversing the angle and direction of pull with moderate scope.

When anchoring in an area where other vessels have been known to lose anchors it is prudent to rig an anchor buoy for recovery. This can be done by fitting a crown strap and working wire to the anchor then attaching a pendant with a buoy. If the flukes become stuck in the rocks an attempt can be made to recover the anchor crown first. Adjust the pendant length for the depth of water plus 20%.

A hard clay bottom poses the hazard of the anchor flukes getting shod with clay and not developing full holding power. The only way to restore holding in this situation is by dropping a second anchor, weighing the first, then manually inspecting and clearing the flukes.

The best bottom for anchoring is generally considered to be sand or a combination of mud and clay.

Scope

The ratio of anchor cable length to the anchor depth is called scope. The more scope an anchor has, the more lateral the force acting upon it and the more effective it can operate. When the scope is small the angle of pull becomes vertical which has the effect of weighing the anchor as opposed to hanging from it.

How much scope is required depends on the weight of the anchor cable, the character of the holding ground, and the depth of the water including tidal differences. A normal ratio of scope is five to seven times the depth of the water; generally speaking 5:1 if your anchor cable is chain and 7:1 if it is a combination of chain and hawser. In storm conditions, a scope of 10:1 may be expected.

Ships typically deploy a lower scope in deeper waters.

Cable, Chain, Rode

In small craft terminology, all of the anchor gear between a boat and her anchor is called the rode. Ships generally refer to this as cable, regardless if its composition includes chain or not.

Chain has the advantage of being heavier than synthetic cables, this keeps most of it on the seabed and helps to present a lateral pull to the anchor as opposed to a vertical one, which would have the effect of weighing the anchor instead of setting it.

Cable or rode has the advantage of being cheaper and stowing lighter while onboard the vessel. That portion of fiber anchor line nearest the anchor can suffer from excessive chafe, and for this reason there is generally at the very least a short length of chain leading from the anchor.

Brief Overview of Chain

Before being certified by the American Bureau of Shipping anchor chain must undergo a breaking test and a proof test load. A breaking test tests the strength of the chain up to its breaking point, whereas the proof test load tests the strength of the chain to a specified limit.

The type of chain links most commonly found are stud links. The primary purpose of the stud is to prevent the anchor chain from kinking, as it prevents links from sliding into one another. Another advantage is the cross bar helps prevent link deformation under stress, which increases the strength of the link by about 15%.

A problem is virtually impossible to detect during an in-service inspection is fatigue. The end links are subject to fracture and must be inspected by shore facilities during regular maintenance intervals.

Shots of Chain

Lengths of chain onboard ship are usually measured in shots. Each shot is 15 fathoms (each fathom is 6 feet). Therefore each shot is a 90 foot segment connected to one another using detachable links.

To keep track of how much chain has been set with the anchor, the detachable link is color coded red for the first shot, white for the second shot, blue for the third shot, and repeating that pattern every three shots. More easy to remember is that a number of links either side of the detachable link are painted white with every shot – every shot one additional link is painted white. If five links are painted white on either side of the detachable link, that is the start of the fifth shot of chain. Additionally, the stud has a wire wrapped around it in the same pattern as the white links so that they may be felt in the dark.

The second to last shot of chain will be entirely painted yellow, and the very last shot of chain will be entirely painted red. This is to signal when it is a good idea to slow and secure the anchor chain before the difficulty of future recovery is greatly exacerbated.