anchor chain and rope size

[Neil Smith]

Hi all,

I have a 58 foot narrowboat with a 20kg anchor, what chain link size should I go for and what rope diameter, I can work out the length according to river depths.

Neil

 

[Chewbacka]

I use 10mm chain on the basis that heavier is better as it helps to keep the anchor shaft parallel to the river bed, and 10mm is about as heavy as I can comfortably handle.   The rope from memory is about 15mm nylon as a thicker rope is more comfortable to handle and there was not a huge saving in using something thinner.  Nylon because it is stretchy and absorbs the snatch as the anchor bites and so reduces the chance of pulling the anchor out.   So far I have never needed to use the anchor, but I think my thinking is sound.

[Richard10002]

In my experience, when the anchor is actually doing its job in adverse conditions, thus holding the boat when it, and the rode, are under tension, the chain or rope is pretty much taught. I agree that catenary plays a part when the line is not taught.

Assuming this to be the case, it is the length of chain or rope, rather than its weight, that dictates the angle of the anchor shaft to the bottom. This is particularly true when the conditions are such that the rode tightens and slackens as the boat moves with wind and waves.

(Worth mentioning that, when calculating the amount of rode to let out, the distance between point where the rode leaves the boat and the water line should be added to the depth, before multiplying. In light conditions 3x should be enough, in "normal" conditions, 5x is recommended and, in heavy conditions, 7x to 10x).

[Alan de Enfield]

7 hours ago, Richard10002 said:

(Worth mentioning that, when calculating the amount of rode to let out, the distance between point where the rode leaves the boat and the water line should be added to the depth, before multiplying. In light conditions 3x should be enough, in "normal" conditions, 5x is recommended and, in heavy conditions, 7x to 10x).

Ideally these figures should read :

minimum of 3x depth when using 100% chain

minimum 6x depth when using 50 / 50 chain rope

minimum 10x depth when using 100% rope.

 

Anchor weight may, or may not be sufficient depending on type.

A 20Kg grapnel type will not be sufficient and give you a totally false sense of security

A 20Kg Danforth type is (maybe just about) barely sufficient

A 20kg CQR / Plough type would be good

A 20Kg Fortress type will 'hold a battleship'

[howardang]

46 minutes ago, Alan de Enfield said:

Ideally these figures should read :

minimum of 3x depth when using 100% chain

minimum 6x depth when using 50 / 50 chain rope

minimum 10x depth when using 100% rope.

 

Anchor weight may, or may not be sufficient depending on type.

A 20Kg grapnel type will not be sufficient and give you a totally false sense of security

A 20Kg Danforth type is (maybe just about) barely sufficient

A 20kg CQR / Plough type would be good

A 20Kg Fortress type will 'hold a battleship'

I would't disagree with those figures, but the nature of the ground has an important bearing on holding power and must be taken into account. For instance, there is a great difference in holding power betwen an anchor set in clay as opposed to a mainly rocky bottom.

 

Howard

 

 

[Neil Smith]

48 minutes ago, Alan de Enfield said:

Ideally these figures should read :

minimum of 3x depth when using 100% chain

minimum 6x depth when using 50 / 50 chain rope

minimum 10x depth when using 100% rope.

 

Anchor weight may, or may not be sufficient depending on type.

A 20Kg grapnel type will not be sufficient and give you a totally false sense of security

A 20Kg Danforth type is (maybe just about) barely sufficient

A 20kg CQR / Plough type would be good

A 20Kg Fortress type will 'hold a battleship'

It is a plough type and I can manage a 20kg comfortably as I used to on a salty boat, but I can't remember what thickness chain and rope I had.

Neil

[Alan de Enfield]

1 minute ago, howardang said:

there is a great difference in holding power betwen an anchor set in clay as opposed to a mainly rocky bottom.

100% agree - but - I reckon most Canals / Rivers are fairly soft 'ouze', mud, or gravel obviously with the odd shopping trolley thrown into the mix.

[nb Innisfree]

I used a shopping trolley as an anchor, easy to handle and lots of grab but rope must be securely fastened to it. I must have lost hundreds in the canal system over the years... 

[howardang]

8 minutes ago, Alan de Enfield said:

100% agree - but - I reckon most Canals / Rivers are fairly soft 'ouze', mud, or gravel obviously with the odd shopping trolley thrown into the mix.

Canals are not really a concern for anchoring for obvious reasons, but river bottoms can vary widely from silt to gravel to shale to solid rock to clay etc. and part of the decision about how much cable to deploy depends on a rough knowledge of the nature of the bottom ( if it is known) if no information is available you need to be ready to vary the amount until the anchor holds.

Howard

[Alan de Enfield]

4 minutes ago, howardang said:

........you need to be ready to vary the amount until the anchor holds

We were recently anchored up, when during the night the anchor alarm went off and we were dragging - this repeated several times thru' the night until eventually we had 150 feet of 10mm chain out and we were only in 6 foot of water.

The 'theory' says we should have been 'ok' with 18 feet of chain, but, as you say, you need enough 'spare'  to let out until you anchor correctly sets.

[jddevel]

Word of warning ALWAYS make sure your anchor rope/chain is SECURELY attached to the boat. I admit to writing from experience when in the North Sea  40 years ago in a Princess 32 I`d recently purchased I travelled through a force 7 and needed to anchor up to wait for the tide to turn to enter the Ouse to Kings Lynn. Discovered that during the somewhat rough passage without my knowledge the anchor had "left" its housing on the foredeck and all the rope and chain had disappeared overboard. I fortunately had an emergency one which I was able to deploy. I learnt the hard way!!!.

[Alan de Enfield]

13 minutes ago, jddevel said:

Word of warning ALWAYS make sure your anchor rope/chain is SECURELY attached to the boat. I admit to writing from experience when in the North Sea  40 years ago in a Princess 32 I`d recently purchased I travelled through a force 7 and needed to anchor up to wait for the tide to turn to enter the Ouse to Kings Lynn. Discovered that during the somewhat rough passage without my knowledge the anchor had "left" its housing on the foredeck and all the rope and chain had disappeared overboard. I fortunately had an emergency one which I was able to deploy. I learnt the hard way!!!.

That's why its called  'bitter end' - you feel a bit bitter as you watch the end that should be attached disappear over the side.

[jddevel]

19 minutes ago, Alan de Enfield said:

That's why its called  'bitter end' - you feel a bit bitter as you watch the end that should be attached disappear over the side.

Actually sea state was such I never saw it go. The family still laugh at me peering  down the hole into the chain locker and obviously my expression of disbelief at its loss. Not sure whether their humour at the time was nervous at having reached a certain amount of shelter or their stupid father wondering if somehow it had gone back into the locker!!!

[Richard10002]

Between the anchor rode, (chain or rope, or whatever), there should be a weak link connecting it to the the securing point on the boat. This should be easily severed in the event that you actually want to let the anchor go and get the hell out of there.

I always thought that it is this weak link that is called "the bitter end", but there will be many assertions as to meaning and origin:

e.g. from http://www.phrases.org.uk/meanings/the-bitter-end.html

"But not so fast. Enter, stage left, Captain Smith. Here's what he has to say, in his publication Seaman's Grammar, 1627, which is the earliest citation of the phrase in print:

"A Bitter is but the turne of a Cable about the Bits, and veare it out by little and little. And the Bitters end is that part of the Cable doth stay within boord."

As you might have deduced, a bitt is a post fastened in the deck of a ship, for fastening cables and ropes. When a rope is played out to the bitter end, it means there is no more rope to be used.

[Alan de Enfield]

3 minutes ago, Richard10002 said:

And the Bitters end is that part of the Cable doth stay within boord

Interesting, and passes the time on a lovely Summers day :

I read that to say that the 'bitter end' is the portion that remains onboard (hopefully) rather than the 'cut-able' link between he cable & the Bit .

 

[nb Innisfree]

4 minutes ago, Richard10002 said:

Between the anchor rode, (chain or rope, or whatever), there should be a weak link connecting it to the the securing point on the boat. This should be easily severed in the event that you actually want to let the anchor go and get the hell out of there.

 

 

Surely a axe close at hand would be better, after all that's what they use in 'Pirates of The Caribbean'