Anchor chains and lines

Anchor chains and lines

In this comprehensive guide to anchor chains and anchor lines, we hope you'll find all the answers to the most important questions and plenty of helpful tips!
As any skipper will tell you, every boat must have reliable, quality anchor equipment at its disposal. Not only is this essential when moored in a quiet and idyllic bay, but even more so when there is wind or swell. Making the right choice will therefore not only make your life easier on board, it is also paramount to ensuring the safety of your boat and its crew. Anchor chains can come in various grades and types, and each has its own specifications and features that enhance effectiveness. The wide range of products is sure to satisfy all requirements. However, one thing is true for all chains: the breaking load of an anchor chain must be such that it is able to withstand individually acting forces caused by the current, wind and swell in any situation, and this also depends on the boat's size, depth of the water and anchorage. The weight of your anchor chain is also an important factor to consider, as is how easy it is to handle on board. It may therefore be worthwhile looking at chain and rope combinations when choosing anchor rode.

Finding the right anchor chain

How to choose the right anchor chain

Finding the right anchor chain depends first and foremost on your type of boat and the area you sail in. Hot-dip galvanised steel chains are widely used in northern latitudes. "This type of chain is reasonably cheap, but also has properties you should be aware of," explains Dietbrecht, equipment expert at SVB. "Because of its rough surface, silt or algae tend to stick to it. Furthermore, the zinc coating could eventually rub off on the seabed, which could cause rust to occur on damaged areas."

What's more, when raising anchor, this kind of chain doesn't flow as compactly into the locker as well as others. The chain can form a pyramid, meaning that the hanging part won't be heavy enough to pull the chain down into the locker. This is not the case with smooth stainless-steel chains, also called Niro chains, but these are around three to four times more expensive and some alloys have little or no corrosion resistance in warm water areas (Caribbean or Mediterranean). The salt water literally eats into the steel and forms holes, which, if they remain unnoticed, can cause the chain to break unexpectedly under load. High-quality, so-called high-strength steel or duplex steel is supposed to prevent such a scenario, but other products also offer corrosion resistance.


Anchor chains: DIN or ISO?

What does DIN and ISO mean?

In Germany, chains are manufactured according to the industry standard DIN 766. Chains from other European countries often correspond to the ISO standard 4565. DIN sizes correspond to uniform dimensions that have been established according to the German Institute for Standardisation (DIN). The International Organisation for Standardisation, ISO for short (from Greek isos = equal), is a corresponding international standardisation organisation. Outside Europe, chains are commonly measured in inches.

"If using a windlass on board, the size of the anchor chain must match that of the gypsy," says Dietbrecht. "If the links in the chain are the wrong size, it will jump and not run through smoothly." By conforming to strict calibration standards such as ISO or DIN, most anchor chains and chain links will run reliably through the windlass. According to DIN and ISO, round steel chain links with a thickness of six and eight millimetres are identical in terms of link length and internal link dimensions. Differences in classification only exist from a size of ten millimetres of steel chain. This information is usually indicated on the winch. However, these industry standards do not say anything about the material of the chain steel and the alloys can have very different properties. Steel chains of the designations 1.4401, AISI 316, V4A, 1.4404, AISI 316L are not considered suitable for seawater in warm areas. The benchmark here is the material 1.4462 (AISI 318LN).

DIN or ISO anchor chain?

Overview ISO anchor chain

d: Link diameter t: inside length (mm) b: Inside width (mm) B: Outside width (mm)
6 18 8,1 21,6
7 21 9,45 25,2
8 24 10,8 28,8
10 30 13,5 36
12 36 16,2 43,2
14 42 18,9 50,4
16 48 21,6 57,6
18 54 24,3 64,8
20 60 27 72
22 66 29,7 79,2

DIN chain characteristics

d: Link diameter t: inside length (mm) b: Inside width (mm) B: Outside width (mm)
6 18,5 7,2 20,4
7 22 8,4 23,8
8 24 9,6 27,2
10 28 12 36
11 31 13,2 40
13 36 15,6 47
14 41 16,8 50
16 45 19,2 58
18 50 21,6 65
20 56 21,6 72
Anchor chain thickness

Anchor chain thickness

Which anchor chain thickness should i have?

There are no legal guidelines on chain thickness, so responsibility here lies with the owner or skipper. You'll have to decide for yourself which is the best anchor chain for your boat. Many specifications and recommendations for skippers are based on safety guidelines issued by yacht associations or the Germanischer Lloyd (GL) classification society. From a purely economic point of view, an anchor chain should of course only ever be as thick as it needs to be. However, experienced boaters do tend to choose chains that are a little thicker, to be on the safe side in case of an emergency. The required chain link thickness is determined by the size of the vessel, i.e., the boat weight and the breaking load of the anchor chain, and varies depending on the chain material. Some specifications base the calculation of the breaking load of an anchor chain on the displacement of the boat, which corresponds to the boat weight in relation to its mass. The average breaking load value for ten-millimetre chain steel is about 80 Kn. The minimum breaking load according to DIN 766 is 4.0 t for a 10 mm round steel chain. The most common thickness for recreational boats is eight, ten and twelve millimetres. An alternative recommendation is provided by Germanischer Lloyd, which refers to the length of the ship (GL recommendation): up to 8 metres boat length = 6 millimetres chain steel, up to 10 metres = 8 millimetres, up to 12 metres = 10 millimetres, up to 14 metres = 12 millimetres and up to 16 metres = 13 millimetres. " You can't tell what loads an anchor chain can take by looking at it from the outside, so a new anchor chain should always have a test certificate from the manufacturer," recommends Dietbrecht, sailor and boating expert.

This is the only way you can be sure that the specified breaking load and gauge accuracy (i.e. exact adherence to the specified dimensions) is correct, and you won't be in for any nasty surprises when at anchor. The price of an anchor chain can vary considerably and depends on the design, quality and length you need. This can range from a few hundred to several thousand euros.

TIP: „Breaking loads on galvanised chains and Nirosta chains are the same. They just have different surface finishes. Hence the difference in price."

Anchor line or anchor chain?

Should i use Anchor line or anchor chain?

Because of its high tensile strength, many skippers prefer an anchor chain. But on dinghies, inflatable boats or small motor yachts (up to 1.5 t weight), you can use an anchor line and it does offer some advantages. Due to its light weight, an anchor line is easier to handle; moreover, the weight of an anchor chain will affect the trim and increase hobby-horsing if stowed in the bow. Furthermore, anchor lines can also have considerable breaking loads, about eight tonnes at 22 millimetres thick, and in adverse conditions with waves or wind they are actually superior to a chain because of their elasticity. Because the line is more flexible, it can absorb dynamic load peaks better, whereby an anchor chain would "jolt" hard. This jerking happens when a wave hits the bow while the chain is taught. The risk here is that the anchor could be ripped free from its hold, or anchor equipment, such as a windlass or cleat could become damaged.

From boat sizes with a weight of 1.5 t, the thickness of an anchor line should be at least twelve millimetres. 10-millimetre lines should be chosen for smaller boats as they are better to handle. Any thinner and lines can cut easily into the hand when being hauled in. The ideal material for an anchor line is nylon or polyester with square braid. Polyethylene lines are not suitable as anchor lines because they do not absorb water and tend to float as a result. Likewise, mooring lines are not suitable for use as anchor lines. Mooring lines must be UV resistant, flexible and have good stretch and abrasion resistance.

Anchor lines, on the other hand, should be relatively stretch-free, but still elastic enough to prevent jerking. Disadvantage of an anchor line: Unlike a chain, it does not self-stow in the chain locker when anchoring and because you need a longer length than a chain, it takes up more space. When using a line, it is essential to note that the swing circle is larger. When a ship is at anchor, it rarely stays fixed at one point: changes in wind conditions or current direction cause it to move in an arc around the anchor. The ship's movement around the anchored position is called the anchor swinging circle. It's important to make sure there are no obstacles within the circle. A wide range of variants available on the market also includes leaded anchor lines. These lines are mostly used with a second anchor.

Anchor line or anchor chain?

Length of anchor chain or line

What length of anchor chain or line do i need?

The vessel size, current and swell are all factors that can determine what length anchor chain you should choose. In general, the longer the anchor chain or anchor line, the better the anchor will hold. The angle of pull is important here, and it should not exceed eight degrees. For optimal mooring of a sailboat or a motor yacht, a chain length corresponding to 5 to 7 times the water depth is usually sufficient. If an anchor line is used instead of an anchor chain, a good rule of thumb is that the line length should be at least ten times the water depth.

Chain fore-runner

What do I need a Chain fore-runner for

A chain fore-runner is recommended to be used with anchor lines on boats that are above a certain weight. A fore-runner chain is a length of anchor chain that pulls down the anchor shaft by its own weight, thereby increasing the static friction on the bottom and thus the effectiveness of the anchor. A chain fore-runner will also protect the anchor line from rubbing and sheathing on rocky seabed. From a boat weight of 1.5 t, a chain fore-runnner of three metres in length is sufficient according to GL recommendations. The German Sailing Association (KA), on the other hand, recommends a chain fore-runner of at least six metres in length.

Anchor buddy (weight)

Anchor buddy (weight)

In some situations, an anchor weight on the chain fore-runner is useful. This extra weight is lowered down on a shackle on the anchor chain and does two things: Firstly, the anchor chain is held down to the ocean bed, so that more chain pulls along the surface on the bottom. And because boat swing is reduced, this is advantageous in crowded anchorages. Secondly, an anchor buddy is useful in strong winds, as it relieves pull on the anchor chain and can prevent the anchor from breaking free. Ropes are available from retailers and suppliers by the metre, but for chains usually only in thicknesses up to 13 millimetres, and above that only in so-called "chain lengths" of about 27 metres. The length of the anchor chain on board should be at least 70 to 120 metres, depending on the sailing area, and correspondingly more for an anchor line or combination of line and chain. Some boaters insist on spare rode consisting of anchor and chain. This can be useful in difficult conditions, but again requires storage space and adds weight on board. Normally, spare rode is not necessary if you check the condition of your chain on a regular basis.

Anchoring in tidal waters presents a particular challenge. Sufficient chain must be deployed to ensure that at least five times the water depth is still out at high tide. In addition, the larger swing circle must be taken into account at low tide.

Attaching, using and caring for your anchor chain

It is advisable to attach an anchor chain to the anchor with a rotating shackle. This prevents the chain from twisting. The end of an anchor chain should be attached to the boat in the chain locker with a rope lashing or strong strop so that it can be easily cut in an emergency. Always shackle a line to the chain. Don't use a sailor's knot like an anchor bend - the knot won't hold reliably in the smooth, synthetic rope. In addition, each knot causes a weak point that reduces the breaking strength of the line by about half. Above a certain boat size, the use of an electric windlass is recommended because the anchor rode is simply too heavy. If the windlass fails, you can sail towards the anchor when retrieving, thus reducing the load. In fact, this is generally advised when using a windlass because it reduces strain on that piece of equipment.

As anchor lines are not very heavy, they can usually be hauled in by hand easily. However, some windlasses have a special capstan fitted to them for this purpose. On sailing yachts, an additional capstan on the foredeck is more likely to be a nuisance and, besides, there are usually enough winches there for hauling. Special care is not required for an anchor chain and can be used for several years, depending on how much wear it is subject to. Nevertheless, it won't hurt to rinse the anchor chain and chain locker with fresh water every now and then to clean.

TIP: If your boat is winterised on land, you must take out the entire chain, including the anchor. Just let your windlass run down and that’s it. This will prevent the chain from rotting away inside the damp and salty chain locker.