How much chain do you need?

I was prompted to write this because of the increasing restrictions in France due to environmental concerns and the impact anchoring has been having on the sea grass/Posidonia. This means that in many places along of the French coast, yachts will have to anchor in water >30m depth.

Although the French rules have perhaps highlighted this, it is not the only place where anchoring in water deeper than 30m is required; other places include Monaco, Capri, the Amalfi Coast, some anchorages in Croatia, Greece and Turkey, the fjords in Norway and Chile and, some of the Caribbean islands – it is not uncommon.

With that in mind, and my own experience of the yachts I have run, I ran a short survey on LinkedIn to gauge how much chain yachts carry.

Although not a huge response, the results were sufficient to mirror my own experience of the amount of chain some yachts carry – in some cases, totally inadequate.

The results to “how many shackles do you carry per anchor?

  • Less than 6 shackles – 18%
  • 7 shackles – 18%
  • 8 shackles – 33%
  • More than 9 shackles – 30%

Rule of Thumb

Of course, there are several ‘rules of thumb’ to help determine how much chain cable is laid depending on the depth of water, among other factors such as type of seabed, weather, current, length of stay, etc. Two such examples are: –

  • The International Association of Classification Societies (IACS) – length of chain in Metres = ratio 6 – 10 x Depth of Water in Metres.
    • For 30m this would be a minimum of 180m or just shy of 7 shackles.
  • The Admiralty Manual of Seamanship uses a formula – number of shackles = 1.5 x √Depth of Water in Metres.
    • For 30m this would be a minimum of just over 8 shackles.

With the above figures, if you err on the side of safety, just under 40% of yachts who responded may not have sufficient chain cable to anchor in water >30m depth and, at 35m depth, only 30% of yachts would have the recommended amount of chain. How this compares to the total fleet would be very interesting.

Interestingly, the RYA recommendation is for a minimum of 4 x Depth. For 30m depth only 4 shackles – approx. half of IACS and The Admiralty recommendation. This may be fine for recreational boats, but for superyachts this seems at odds with both IACS who test and approve anchoring arrangements for ships and superyachts, and the experienced seafarers of the Admiralty.

As RYA qualifications are inherent to Yacht Deck Officer training and certification, has their ‘rule of thumb’ become the standard that most superyacht crew use – again an interesting question!

There is no doubt IACS and The Admiralty are a more qualified authority when it comes to anchoring of ships and large yachts and in my opinion captains would be wise to use their ‘rule of thumb’ rather than the RYA.

The Mysterious Equipment Number

Until I did my Master Unlimited CoC, I never took time to consider how the size of anchor and length of chain were determined for a given vessel. That’s when I learnt about the Equipment Number (EN).

Most superyachts are Classed by one of the IACS members such as Lloyds, DNV GL, ABS, RINA, etc., and they use common rules to determine the mooring equipment. This is based on the EN which is calculated for every Classed vessel – the formula is as follows: –

EN = ² ⁄ ³ + 2 BH + 0.1A

Where:-

  • = moulded displacement in tonnes to Summer Load waterline
  • B = moulded breadth, in metres
  • H = effective height, in metres, from Summer Load waterline, to top of uppermost house
  • A = area, in square metres, in profile view, of the hull, superstructure and houses above Summer Load waterline.

The resulting EN is used in a table that details the number and mass of the anchor, chain length, diameter and grade, as well as towing and mooring lines.

Excerpt from Equipment Table – note ‘Total Length’ of chain is normally split equally between the two anchors.

It is important to note that the EN and anchor equipment is based on the following assumptions and limitations:-

  • Temporary mooring in harbour or sheltered waters
  • Current velocity: max 5 Kn
  • Wind velocity: max 48 Kn
  • No waves
  • Length of chain paid out, scope 6 -10
  • Good holding ground

The effect of waves is important – a significant wave height of just 2 metres would reduce the equivalent max current and wind velocities as follows:-

  • Current velocity: max 3 Kn
  • Wind velocity: max 21 Kn

A significant reduction in the holding power.

As most yachts use high holding power anchors (HHP) the rules also allow their mass to be reduced to not less than 75% of the table value.

Bitter End – Caution!

It is also important to know that the pin securing the bitter end to the chain locker is designed to be sacrificial and break at a load between 15% – 30% of the minimum breaking strength of the chain cable – it is designed to fail to prevent structural damage to the vessel.

It should be a fundamental part of the yachts risk assessment and procedures that, in the event of a runaway chain, the mooring team evacuate to a safe area as the flailing end of an anchor cable can have devastating effects – as was sadly experienced on Ocean Victory.

The anchor and mooring arrangements need to be carefully designed for the risks involved; unfortunately, some yachts, especially those with enclosed decks, place the windlass operator in harm’s way and do not provide safe egress in the event of a failure. Like many operational aspects of yacht design, work is still required to improve safety.

A Guide to Anchoring

The video ‘Anchor Awareness’ produced by DNV, GARD and The Swedish Club, although based on commercial ships, is also valid to larger yachts and is a useful resource that helps demonstrate anchor procedures and safe practice and is well worth a watch – especially for junior officers and deckhands who may be part of the mooring team.

Can be accessed by taping on the image below.

anchor awareness

This piece was not meant as a guide to anchor best practice, but to try to assess if yachts carried sufficient chain for the intended depth, and help fill in some of the knowledge gap that may be missing from the yacht syllabus.

I hope it imparts a better understanding of how anchor and chain cable size and length are determined for yachts. And, importantly, the amount of chain paid out relative to depth that is recommended by authoritative bodies.

This knowledge may result in more secure anchoring and the provision of chain more appropriate to the expected use, water depths and conditions that may be encountered.

I can sleep when I’m dead

I suspect many captains and crew will have succumbed to the embrace of this maxim – I know I have in my past.

Working long hours and having minimum sleep was often worn as a badge of honour, it demonstrated a grafter, someone who was willing to put in all the hours necessary to get the job done. But as research has now shown, sleep deprivation, whether acute or chronic, can have short term consequences – sometimes devastating – as well as long term physiological and/or mental health effects.

I was somewhat aware of the importance of sleep and things such as the circadian rhythm, but it was only recently after reading ‘Why We Sleep’ by Mathew Walker, who is currently Professor of Neuroscience and Psychology at the University of California, Berkeley, that I began to really appreciate why sleep deprivation can be so damaging to not just health, but also performance and safety.

The book details the reasons why we sleep, what happens during sleep, the benefits of sleep and the effects of disruption and/or deprivation. Like the air we breathe, the water we drink, and the food we eat, sleep is essential to our health. The Guinness Book of World Records happily records extreme activities such as a freefall from 41,422 metres and other events such as tight rope walking across the Grand Canyon without safety net or tether but does not recognise sleep deprivation records because of the danger to health!

What’s this got to do with yachting?

The World Maritime University (WMU) Report1 into the hours of work and rest (HOWR) in shipping also considers this subject and the effects of lack of rest, fatigue, safety and well-being of crew and these issues are equally applicable to yachting.

We know that the demands on crew have been increasing for many reasons and, in the main, there has not been any real change in the manning levels to meet that demand and on many yachts, it is likely that the quality and quantity of sleep is suffering as a result. Compounding the potential for sleep disruption are the variable work patterns that are an operational characteristic of yachting as the program and use changes e.g. guest-off, guest-on, daywork, watches, late finishes and early starts, even if crew are maintaining their HOWR.

Consider that the HOWR minimum rest period should not be less than 10 hours, but can divided into two periods, one of which not less than 6 hours. And that within that time there are factors such as eating, socialising, waking and preparing for work, that eat into sleep time. If working to the minimum regulations the longest period of sleep could be less than 5 hours – less than the amount research suggests is optimal.

I’m sure we all know how bad we can feel for days after a long-haul flight, yet crew are often expected to switch from working during the day to night at short intervals. Studies have shown it takes a day per hour of time zone difference for the body to acclimatise. It would take days for a crewmember assigned to work a night watch to properly adapt and perform at their best and they would likely be feeling the undesirable effects when they switched back to daywork at the end of the week – when they would have to go through the whole process again.

The working pattern and allowing sufficient time to acclimatise to the working hours is an important factor in helping with sleep and fatigue. I know in the past we used to rotate deckhands onto night watch once a week and stewardesses would frequently switch from late nights to early morning with the result their body clocks where probably always jet lagged. Having a schedule that allows acclimatisation to working hours is not an easy task given limited crew and variable demands but, where practical, it warrants a more considered approach.

Of course, it’s not just the work pattern that can disrupt sleep. The environment, such as noise and light, can affect the quality and quantity of sleep. Noise from being underway, picking up and dropping anchor, bow thruster operation, light from portholes or crew entering the cabin. And as we all know, the violent motion and noise of a yacht in rough weather also can severely disrupt sleep.

Crew accommodation and cabins are also a factor. Having somewhere free from noise and light pollution, with a comfortable ambient temperature, can be a challenge on some yachts, especially the smaller yachts where space is severely limited and often the crew mess and laundry are in the same space. Though, even on some larger yachts, the crew cabins can sometimes seem like an afterthought.

Minimising noise and light – beyond the minimum MLC standards – should be a priority such as: –

  • Black out blinds for portholes
  • Curtains around bunks that can also block light and afford some privacy
  • Low intensity lighting for crew corridors
  • Better sound insulation – especially crew corridors and where cabins back onto the crew mess or technical spaces
  • Improved isolation of equipment; resilient mounts, sound boxes.
  • Doors at corridor ends
  • Carpet with underlay in cabins and corridors

Some of the above could be applied to existing yachts.

For those who believe they can manage on minimum sleep, it is interesting to note, though not scientifically proven, that Ronald Reagan and Margaret Thatcher, two of the most well-known exponents of 4 – 5 hours of sleep, suffered in later years from Alzheimer’s. The point being, perhaps the cumulative effects of restricted sleep may be more profound than we might think.

Unlike shipping, our industry is not driven by commercial pressures but by more esoteric metrics such as pleasure, enjoyment, quality, safety, and security, all of which are heavily reliant on the crew. Yet often yachts are designed to comply with the minimum standards rather than the operational realities of delivering incomparable experiences to yacht owners and/or charter guests.

The ‘WHU Report’ and ‘Why We Sleep’ should be essential reading for anyone involved in the design and operation of a superyacht. They offer compelling reasons why better sleep can result in happier and healthier crew, better performance, safer yachts and why it deserves more attention in our indusrty.

*1 World Maritime University (2020). A culture of adjustment, evaluating the implementation of the current maritime regulatory framework on rest and work hours (EVREST). World Maritime University. (Attributed authors: Baumler, R., De Klerk, Y., Manuel, M.E., and Carballo Piñeiro, L.)
By |2021-06-28T08:54:52+02:00May 3rd, 2021|captains, crew, leadership, Managment, regulations, Safety|
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