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Selecting the correct rode and ground tackle for your vessel

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What is the issue?
Investing in the correct rode and ground tackle is not straight forward. There are a large range of different anchors and rode and chain sizing’s.

Why address this?
Implementing correct ground tackle is essential for the welfare of the vessel and crew. Sleeping serenely whilst at anchor is largely a measure of confidence in the ground tackle and the manner in which it has been deployed. Equally I have spent many a dark night riding out a gale, and the occasional cyclone, praying for the survival of the ground tackle that the vessel is dependant upon. Some science needs to be applied to the decision making.

How to address this?
Base your anchor and rode selection criteria upon the chart presented in figure 1.

I would add these additional comments:

1/ I recommend all chain on the primary rode.
2/ I recommend at least 1 boat length of chain on rope rodes.
3/ Beware of cheap imitation CQR anchors. Watch out for a steel pin or bolt securing the shank tothe flukes – on the genuine CQR this is forged with the shank.
4/ I would use a Danforth as my second anchor but not my primary anchor. Note that on Danforth’s own selection charts they give recommended sizes for winds to only 20 knots. I show bigger sizes. Note that some manufacturer’s recommendations give a lower weight anchor than the Code of Practice.
5/ Do NOT assume that American chain sizes are direct conversions from European chain sizes. Not only is the pitch different but in the USA the wire size of a chain link is actually 1/32” larger than the nominal size.
6/ In severe weather conditions I recommend anchoring to two anchors laid from the bow 45° apart. Protect rope rodes with canvas or leather sleeves at wear points.

Tension on an anchor rode.

Another useful table is an anchor rode tension guide. This shows the estimated tension imposed on an anchor rode by various wind velocities acting on a 36’ cruising sloop with sails furled:

20 knots = 150 lbs or 70 kg of rode tension
25 knots = 225 lbs or 100 kg of rode tension
30 knots = 300 lbs or 140 kg of rode tension
35 knots = 400 lbs or 180 kg of rode tension
40 knots = 550 lbs or 250 kg of rode tension
45 knots = 700 lbs or 310 kg of rode tension
50 knots = 900 lbs or 400 kg of rode tension
60 knots = 1200 lbs or 550kg of rode tension

The load on the anchor rode is substantially less than the safe working load of the chain or rope used to secure a boat of this size. For example, the safe working load of the 8mm chain recommended for a 36’ boat of this type is 800kg, with an ultimate breaking strain of around 3200kgs.

So, unless there is a “weak link” in the system such as a bad splice or deficient shackle, the factor which most effects security is the strength of the connection between anchor and seabed. In most cases the ultimate strength of the anchoring system vastly exceeds the load at which the anchor will break out. I have seen numerous anchor pull tests that compare the break-out load for most of the popular anchor types. There is little consistency in these tests, sometimes one type of anchor wins, in another test that anchor might come out as the worst! The interesting thing is that the majority of the test results, and all the manufacturers’ data, credit the popular anchors with a greater break-out load than would be necessary to hold the boat in the circumstances of the selection chart. So, as long as the anchor is properly set, in the bottom for which it is suited, you can feel confident in ground tackle selected from the chart.

With thanks to:
Salty John, specialising in a select collection of tried and tested sailing equipment. Web site: http://www.saltyjohn.co.uk/ phone +44 (0) 1995 672556 e-mail: info@saltyjohn.co.uk

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