Anchor chain is 50m enough?

[craigsmith]

My anchor chain is worn out and as with most boats it has 50m of chain. However considering the tide off the Channel Islands is 50m sufficient or borderline?

I have never dragged off the Channel Islands but I cannot say that I am completely relaxed. I have just bought a Rocna for this season so I will be much more happier than the CQR it replaces, should I buy 60m or is that overkill?

How much chain would you carry if you had to start again?

You only 'need' enough chain to safely clear underwater sharp bits in your intended cruising grounds. You may 'want' more for practical reasons, e.g. you don't want the chain leaving the windlass. The length of chain has little to no impact on the anchor's performance.

The message here is that beyond a certain minimum dictated by the region it is really more a personal preference issue.

 

[snowleopard]

The length of chain has little to no impact on the anchor's performance.

A story from a Board of Trade master's oral....

Examiner: You are anchored off a lee shore. The wind increases to F6. What do you do?

Candidate: Let out another shackle of chain

Examiner: The wind now increases to F8, what do you do?

Candidate: Let out another 2 shackles of chain.

Examiner: The wind is now up to F10, what do you do?

Candidate: Let out another 3 shackles of chain

Examiner: Where are you getting all this chain from?

Candidate: Same place you're getting all this wind.

 

[FullCircle]

A story from a Board of Trade master's oral....

Examiner: You are anchored off a lee shore. The wind increases to F6. What do you do?

Candidate: Let out another shackle of chain

Examiner: The wind now increases to F8, what do you do?

Candidate: Let out another 2 shackles of chain.

Examiner: The wind is now up to F10, what do you do?

Candidate: Let out another 3 shackles of chain

Examiner: Where are you getting all this chain from?

Candidate: Same place you're getting all this wind.

 

[craigsmith]

Right.

Correct answer to the first question: ensure I have optimal scope deployed and increase if necessary up to a max of ~ 8:1 or as anchorage permits.

Correct answer to the second and subsequent questions: nothing, because I have chosen an adequate anchor for my vessel and have an optimal rode deployed.

 

[jimi]

The chair is 13 years old and has lost it's galvanising and has started to rust.

I'd sit with that ;-)

 

[mattonthesea]

Rusty Anchor Chain

I'd sit with that ;-)

Yep me too. I have 47m of rusty 8mm chain on a 5.5 ton Rival 32. It means washing the deck down every time I raise the anchor. When I got the boat I took her to a sandy anchorage and 'ran' around the anchor several times, end for ended and did the same. I had to chop off 3m (hence 47m) as the links had 'welded' together but otherwise I have had no problem in 5000 miles of cruising. I would get it regalvanised but I didn't get a round tuit before leaving!

I also have 50m of rode in case of those deep needs!

As previously mentioned: the current version of Girlfriend will cause any version of Wife (V 1.0 - Wife XP or Vista) to crash; the next release of Wife may have sorted this incompatibility

 

[nmeyrick]

How much rust is too much?

I currently have a rather rusty looking chain (50m of i believe 10mm) on my Rival 38. I am setting of on a couple of months of cruising this summer, covering the south coast, channel isles and possibly scillies.

I have never really used the anchor, a venerable 45lb CQR in anger and am planning to upgrade it. I had planned to upgrade the chain at the same time, and had considered regalvanising but almost ruled this out on the basis that the anchoring set up is only as strong as the weakest link (no pun intended) and don't want to endanger the boat.

But people here seem pretty unconcerned about rusty chain. How much rust can I have without it causing a problem? How would I tell whether my chain is worn or compromised, or if it is strong enough to be regalvanised?

Thanks

 

[craigsmith]

Ignoring badly rusting chain would just be negligent. It is matter of common sense. Without seeing your chain nobody can say. Surface rust is not likely to be a significant problem, but if the rust has substantially reduced the section size of the chain then it is badly compromised. A lot of the strength of chain is in the outer part of the rod... just by simple geometry... it does not take the loss of much of the surface to seriously reduce the strength (10 mm chain is about 25% stronger than 9 mm chain for example, so imaging losing an effective 0.5 mm of radius from a link - it only has to happen in one place on one link).

Bad rust may make re-galvanizing impractical / too expensive, as it must obviously be cleaned off and treated before dipping. Especially with cheaper chain it often makes more sense to buy new stuff.

There is the related issue that possibly you don't know what the chain is - brand and grade - the way you describe it, it seems maybe this is the case. In this situation I would be uncomfortable using it even in good condition. I would be dumping the stuff and getting good quality G40 or preferably G70 high tensile replacement in which case you could lighten the load on your boat by switching to 8 mm.

 

[fireball]

Look at how much metal has been wasted - up to 10% or so and it is less of an issue - beyond that is (I would suggest) new chain rather than re-galvanising.

 

[Rigger Mortice]

The length of chain has little to no impact on the anchor's performance.

I know that you carefully worded that to say the "anchor's performance" and that it is impractical to think of the anchor in isolation. Nevertheless, I would be fascinated to see the supporting evidence of that statement.

 

[craigsmith]

www.petersmith.net.nz/boat-anchors/catenary.php

 

[Scotty_Tradewind]

I I decided to get a Rocna and 25 more metres of chain. However, I bought the Rocna first and, after a couple of seasons use, that seems to solved the problem of getting the anchor to bite so I never bothered with the extra chain.
Richard

similar experience.
And I've just ordered my second Rocna for my 'new' boat





www.sailingscotty.com

 

[Rigger Mortice]

www.petersmith.net.nz/boat-anchors/catenary.php

Thanks for that.
I haven't been able to get beyond the first two graphs as I can't understand them. You mention that the horizontal axes are different but you don't state what they are. Distance from anchor to boat,? Length of chain? If the former then I would expect the 2nd graph to show a greater distance. If the later then the chain length appears to have reduced!!!

I'm trying to understand the "science" and whilst I can understand the general point which is being made, the presentation of the maths behind it doesn't seem quite right.
Unfortunately you have not given any details of the mathematical modelling.

 

[Twister_Ken]

Thanks for that.
I haven't been able to get beyond the first two graphs as I can't understand them. You mention that the horizontal axes are different but you don't state what they are. Distance from anchor to boat,? Length of chain? If the former then I would expect the 2nd graph to show a greater distance. If the later then the chain length appears to have reduced!!!

I'm trying to understand the "science" and whilst I can understand the general point which is being made, the presentation of the maths behind it doesn't seem quite right.
Unfortunately you have not given any details of the mathematical modelling.

Also, the words are not written by anyone versed in the art of communication. It's a classic case of I speak jargon, why don't you?

 

[Seven Spades]

Ignoring badly rusting chain would just be negligent. It is matter of common sense. Without seeing your chain nobody can say. Surface rust is not likely to be a significant problem, but if the rust has substantially reduced the section size of the chain then it is badly compromised. A lot of the strength of chain is in the outer part of the rod... just by simple geometry... it does not take the loss of much of the surface to seriously reduce the strength (10 mm chain is about 25% stronger than 9 mm chain for example, so imaging losing an effective 0.5 mm of radius from a link - it only has to happen in one place on one link).

Bad rust may make re-galvanizing impractical / too expensive, as it must obviously be cleaned off and treated before dipping. Especially with cheaper chain it often makes more sense to buy new stuff.

There is the related issue that possibly you don't know what the chain is - brand and grade - the way you describe it, it seems maybe this is the case. In this situation I would be uncomfortable using it even in good condition. I would be dumping the stuff and getting good quality G40 or preferably G70 high tensile replacement in which case you could lighten the load on your boat by switching to 8 mm.

The chandlers I have spoken to only really supply G30 and poo poo G40 as being over the top and expensive. I have never heard G70 before this post. Lets say my 10 ton 40' boat has been using 50m of 10mm chain. Are you suggesting I can reduce both the length and diameter of the chain by increasing the quality of the chain and increasing the length of rode? If so how do you quantify this. If this is the case what are the consequences of a crowded anchorage, i.e. is there a downside in that you might need to pay out more than the surrounding boats?

What is the relative differences in strengths of G30, G40 and G70?

 

[Conachair]

I haven't been able to get beyond the first two graphs as I can't understand them. You mention that the horizontal axes are different but you don't state what they are. Distance from anchor to boat,? Length of chain? If the former then I would expect the 2nd graph to show a greater distance. If the later then the chain length appears to have reduced!!!

Pretty sure the y axis (vertical) is depth of water to the anchor roller and x axis (horizontal) is horizontal distance from boat to the anchor. If you look closely the 2nd graph shows yellow dot at the right hand end of the chain further from the anchor, only takes a little to straighten out the chain. And he's right, when the forces on the boat get high the chain points straight at the anchor. Catenary does nothing. Neither do angels/chums/whatever you call them. In the more normal conditions we can carry on argueing

 

[fishermantwo]

Your suggesting 9m of chain would do me? The tidal range is greater than that. Do you mean a metre of chain per FOOT of boat length? That would be reasonable - I have marginally less & no problems.

No I mean exactly that. Old blokes like us don't need to be pulling all that chain that's doing nothing anyway. As Craig mentions you only need chain on the bottom to stop wear on a rough bottom and set the anchor.
My yachts 9.14 metres and I have 8 metres of 10mm chain and a CQR. My fishing vessel which I have now sold and I'm retired, 12 metres long. 10 metres of chain and a Delta. For survey purposes my fishing vessel also carried 2 CQRS, one with 40 metres of chain, the other 12 meters of chain and a 100 meters of nylon. These were viewed annually but never moved in 25 years of operation. Interestingly the "Authorities" classify a CQR as a high holding anchor.

Hopefully we will get some feedback eventually from cyclone Yasi. Lots of boats destroyed but plenty survived winds just over 300 kph.

 

[Rigger Mortice]

when the forces on the boat get high the chain points straight at the anchor. Catenary does nothing.

Yes, I think we can all accept that (except Parsifal!) , but the graphs are not clear and need to be validated.

This is all being presented to us as a carefully researched learned document and I am trying to work out if it really is.

I've looked further at the report and the next section is, to me, incomprehensible. I am beginning to think that it maybe twaddle. It may not be, but it certainly needs further explanation.

I'll be interested to see how he supports it.

 

[Poignard]

Yes, I think we can all accept that,

Well I can't.

The only way an anchor chain or warp can be straight is when it is weightless (unless it's hanging straight down!)

 

[Rigger Mortice]

Well I can't.

Of course, strictly speaking, you are correct. You could have also added that if there was an infinite tension on the chain then the chain would be straight!

However, I think we are talking about reality and, in extremis, the chain will be to all intents and purposes straight.

But, Yes. You are right.