Anchor & Chain

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Windlass and Bowthruster controls Windlass and Bowthruster controls
Windlass and Bowthruster controls

Few topics excite boaters as much as choice of anchoring tackle. For every fan of one anchor type there are a handful of opposing viewpoints and the fronts are as hardened and immovable as the trenches of World War I. When I first started sailing I didn't really understand what anchoring really involved and had the vague impression that the anchor, also referred to as the “hook”, worked something like a fish hook and hadn't thought about how the anchor is raised if that were truly the case.

Anchoring has several aspects, the two most important aspects are the physical anchor itself and the rope or chain that attaches it to the boat. This is called the rode and one major factor in anchoring mishaps is choosing a length that is too short. Assuming chain rather than rope, a scope of 3:1 is the minimum length to start with; this means that if the water is 30 feet deep one needs to let out at least 90 feet of chain. By doing so, when the boat gets blown back by the wind or the waves or a combination of the two, the resulting pull on the anchor is mainly backwards and parallel to the sea bottom. If the scope is too short, the boat will pull on the anchor at an angle and that is not a good thing when it comes to holding power as it will tend to rip the anchor from the bottom while if the scope is long enough and the pull parallel to the ground anchors are designed to dig themselves in even deeper and thus increase holding power.

The classic among the anchors is the fisherman's anchor, depicted below and known to most as the subject matter of a true mariner's tattoo. The anchor has two hooks like a fish-hook, but it also has a cross-bar. Without this cross-bar, the fisherman anchor will drag with both flukes bouncing along the bottom and it won't “set”; the cross-bar is there to make the anchor tilt and to force one of the flukes to push it's sharp end into the ground and then dig in, just as with a fish-hook. Once this happens the anchor is solidly attached to the bottom and, assuming sufficient scope, it will take a lot of force to budge and the boat is safely secured. Weighing, or lifting, the anchor is a matter of sailing or motoring forward to be right above the anchor while pulling in the chain, then the force upon the anchor is no longer parallel to the bottom but straight up and the buried fluke will break out of the bottom and be lifted up. At least that is what happens in an ideal situation - if things go awry the anchor could get caught (fouled is the mariner's term for this) in rocks or coral or other things on the bottom and might be impossible to lift. Sometimes when that happens the only solution is to dive on the anchor, if one is lucky the water is warm and clear and not too deep and the problem easily solved; otherwise dive gear or external help is the only solution.

Various type of anchors commonly found on boats
Nelson's Dockyard anchor Nelson's Dockyard anchor

[17°0'28.93"N 61°45'58.04"W ]
Nelson's Dockyard anchor
CQR or Plough anchor
CQR / Plough
Bruce anchor
Danforth anchor
Rocna anchor

In addition to holding power, a good anchor must be able to reset quickly. When the angle at which pull is exerted from the ship changes, as it does when the wind direction shifts or if the water flow direction changes (tides or other currents) then anchors will break out of the bottom, and it would be bad if it were to then start dragging along the bottom instead of re-setting and digging back in. The same thing applies when an anchor breaks out due to a temporary overload, it should automatically re-attach itself to the bottom. All anchors are designed to do this but have different characteristics depending upon the type of bottom - some are better in grassy bottoms, others in gravel, others in mud or sand.

G43 Chain G43 Chain
G43 Chain
Chain link attributes
chain link description

Anchor chain is heavy. Really heavy. The recommended chain diameter for Zanshin is 12mm and 150 meters (492 feet) of that weighs around 490Kg! All of that weight is concentrated at the tip of the bow, whereas weight on sailboats is normally best kept as low as possible along the centre line and close to the keel.
There are various types of chain available, with a dizzying number of chain types and chain strengths, this article provides an excellent overview for those interested in detailed information. One common chain type adheres to the DIN 766 standard, which specifies many attributes but the important ones are the chain link size, pitch and diameter (Size, “P” and “d” in the chart below). The other column headings that are cryptic are “WLL” = Working Load Limit and “BLL” or Breaking Load limit. The WLL is usually set to around 1/4 of the BLL.
By switching from 12mm G30 chain to 10mm G70 I can increase the working load limit by almost 25% and save 150Kg of weigh at the. As is to be expected, the higher quality chain is more expensive. With 400 feet of chain I can anchor in water as deep as 130' with 3:1 scope in calm conditions or 100' in somewhat more boisterous ones, which greatly increases my choice in anchorages, particularly later on in the Pacific where deep-water anchoring is more common than in the Caribbean. Additional chain and scope also offers a better margin of safety and I'll always choose 10:1 scope when I am not hampering someone else in the anchorage rather than sticking to the minimum. Having chain in the chain locker is just as useless to boaters as altitude above you or runway behind you is to pilots.

DIN 766 type chain comparison
Grade Size mm P d Kg/m WLL BLL 150mKg
G30 10 28 34 2.30 1250 5096 345
G30 11 31 36 2.70 1600 6422 405
G30 13 36 44 3.90 2000 8154 585
G70 10 30 35 2.35 2200 11000 353
G70 12 36 40 3.30 3160 15800 495
Delta Anchor Delta Anchor
Delta Anchor

Anchoring for me, all alone on board, was a bit of a chore aboard the previous boats. Without an anchor windlass remote this involved going forward and aft a couple of times during the process and I managed to break my little toe during one such exercise (see the St. Barths page for the full story) and my middle toe on yet another trip in 2011 doing the same thing. Therefore I want to have an anchor remote control from the cockpit on my subsequent boats and fortunately Zanshin is equipped with not only an anchor remote but also a chain counter so I know how much I've let out or still have to pull in without having to go forward.
I'll skip over the discussion regarding the advantages and disadvantages of the different anchor types and just put forth that I decided to start off with a Simpson-Lawrence Delta anchor as my main means of attaching Zanshin to the bottom of the sea. The recommended anchor size for the size of Zanshin is a 25Kg (55lb) one but I did an up size to 32Kg (70Lb). This extra weight assists in letting the anchor dig into the bottom, which is particularly helpful in tough holding as with sea-grass.

2218 views since 2017-02-04, page last modified on 2017-04-18.