Extending the anchor rode

[jcpa]

I posted a version of this text on the "Splicing anchorplait to chain" thread, but I am reposting it here as I am sure more of you have some relevant wisdom to share.

The anchor rode that came with my boat was 20m of 8mm chain and 30m of 14mm octoplait spliced together over a number of chain links (as shown on the Jimmy Green website). However, the chain was quite rusted, so I bought replacement lengths of chain and plait - fully intending to splice them together. I was going to salvage the old rode, removing the rusted bits and re-joining with Crosby mending links, and then putting it in the cockpit locker for use with a spare/kedge/lunch hook (replacing a smaller 6mm chain/rope rode).

Then I saw various posts about keeping a long rope or chain handy to extend the main rode when required (deeper/rougher conditions). I have therefore simply tied my new chain and rope together while I ponder things. In practice, I have only anchored briefly so far, in calm shallows, and have not needed to let the rode out beyond the knot (boat only draws 0.7m with keel up).

But what do forum-ites do if they want a longer warp (e.g. for a Channel Island trip)? Shackle in more chain (e.g. at the anchor end), or join on more rope at the boat end? Or do you all have huge lengths of warp in the first place? I rather got the impression that shackles in anchor chain were not approved of - even tested/graded ones, though I don't know it that is for weakness reasons, or because of windlass problems (I don't have one of those!).

Sailorman has said in the other thread that he replaced his usual 20m of 8mm chain and 30m of octoplait with 60m of 8mm chain and 50m of octoplait for a Channel Island cruise, but never used it there, and it is now in his shed. Was this an unnecessary expense?

I would much like to hear what others would do.

 

[Rossynant]

I would (as not doing it now) keep longer chain for main bower, some 40m or more + warp, not necessarily attached. Though I think on my boat now I will splice the warp to, having plenty space in locker. Or divide locker for two bowers, still thinking.
When more than some 30-40 m of chain is necessary then another length of chain can be attached, or warp since in tough situation warp is better.
There is nothing wrong with shackles, but somehow normal anchor shackles are hard to see now. Such were dependable, going through rollers and even gypsy. It was customary to have 2-3 pieces of chain aboard, different lengths, so to be joined as needed.

 

[Oldhairy]

I'm not overly fond of joining links so I use s/s lug-less shackles. Lug-less because the conventional ones snagged on the bow roller. They still have to be hand fed through the capstan. And outrageously expensive.
Yet to hear of a vessel getting into trouble for carrying too much ground tackle

 

[vyv_cox]

In your situation, with your boat, I would not be faffing about joining anything to anything. Have a decent length of chain in the locker, sufficient for virtually all eventualities. When I owned 27 and 29 foot boats of similar type to yours I carried 50 metres of chain that was enough, even in Liverpool Bay, for all ranges of tides. Later, when cruising far more widely, 50 metres was always enough in the vast majority of cases, although I did upgrade to 60 for certain anchorages in the Med.

The theory says that chain over about 20 metres offers no advantages where strength is concerned. The practice is that all chain offers many advantages, including holding the boat from wandering all over the anchorage and not having rope draped around your prop and rudder. It is also far easier to stow in the chain locker.

 

[jcpa]

Thanks for those comments.

I think I'm going to finally splice together my new chain and rope, and the splice a hard eye in the other end of the rope. I will similarly splice a hard eye in the other end of the old rode, meaning I could easily shackle it (the wrong way round) to the new rode to give me more length if I ever need it. I may not have Vyv_cox's 50m of chain, but I would have 20m of chain and 60m of rope (and another 10m of "salvaged" chain on the end - but probably still sitting in the locker!).

Not perhaps everyone's solution, but I think it makes sense to me!

 

[oldbilbo]

.....The anchor rode that came with my boat was 20m of 8mm chain and 30m of 14mm octoplait..... However, the chain was quite rusted, so I bought replacement lengths of chain......

I confess to a similar experience. However, I bought 50 metres of 10mm chain from a forumite - 'willing buyer/willing seller' - and toddled off home pleased with my 'bargain'. Now I have hoiked this chain out of my car, I realise I now need a rather larger boat to carry it, a larger bower anchor to match the strength, and a FAR LARGER crew to haul it all back on board again.

The temptation is to have the 20 metres of 8mm stuff re-galvanised, use that with the octoplait, and save the hernias for later in life.

Where did I go wrong....?

 

[vyv_cox]

I confess to a similar experience. However, I bought 50 metres of 10mm chain from a forumite - 'willing buyer/willing seller' - and toddled off home pleased with my 'bargain'. Now I have hoiked this chain out of my car, I realise I now need a rather larger boat to carry it, a larger bower anchor to match the strength, and a FAR LARGER crew to haul it all back on board again.

The temptation is to have the 20 metres of 8mm stuff re-galvanised, use that with the octoplait, and save the hernias for later in life.


Where did I go wrong....?

There is a surprising difference in weight between 8 mm and 10 mm, as you have found. I used to retrieve a 35 lb anchor on 8 mm chain manually, hard work but achievable. The same anchor on 10 mm chain on a friend's boat was out of the question.

If you need the chain strength you could consider going to Grade 70 8 mm, which has considerably more strength than grade 30 10 mm. I know that this is what Paul and Rachel Chandler have done when refitting Lorne Rival.

 

[oldbilbo]

There is a surprising difference in weight between 8 mm and 10 mm, as you have found.

Yes.... the 10mm stuff is about 50% heavier than the 8mm, according to Bradney Chains' table ( http://bradneychain.anu.net/?wpsc-product=short-link-chain-2 ) - and about a 50% increase in strength, too. But it WAS appealingly cheap....

 

[NormanS]

Yes.... the 10mm stuff is about 50% heavier than the 8mm....

And that is why it forms a better catenary, and holds the boat better.

 

[vyv_cox]

And that is why it forms a better catenary, and holds the boat better.

Ha ha! Nice try! See http://alain.fraysse.free.fr/sail/rode/dynam/dynam.htm

 

[NormanS]

Ha ha! Nice try! See http://alain.fraysse.free.fr/sail/rode/dynam/dynam.htm

He can try and dress it up with all sorts of apparent science, and fancy formulae, but it is hard to deny that heavier chain will give better outcomes than light chain.

 

[vyv_cox]

We've argued this so many times that I cannot be bothered to continue. Suffice to say that I totally disagree with you, and so does the maths.

 

[oldbilbo]

Ha ha! Nice try! See http://alain.fraysse.free.fr/sail/rode/dynam/dynam.htm

It appears from the above reference that I should try for a 'heterogenous rode' - not something ever mentioned in the RYA night classes. Be that as it may, and with an existing 50-odd metres of blurry heavy 10mm galvanised, I seem to be best advised to follow the following....

In addition, this solution is well adapted to higher water depths, provided the available chain is permanently spliced to a nylon extension. For example, if you bought 55 m (180 ft) of chain, you can splice an equal length of nylon to it, so you get a king-size rode! When there is no need for veering the whole chain, you use the hook with the additional short line to take the chain up. If the whole chain is necessary, you simply pay out more rode (up to 110 m - 360 ft).

So I simply need to ensure I have a short length of 18mm or better nylon, with a chain 'ook, and a much longer length of 18mm or better nylon to supplement my OTT chain. Or is there more to this anchoring business than has been aired so far......?

Are we perhaps touching upon conditions that might properly require the employment of tandem anchors, or V'd anchors, or lines ashore to mangrove trees, quays, jetties, and rock pitons?

 

[Rossynant]

Interesting calculations in the link, (not that I studied in detail) but missing some practical points. Who anchors regularly with 11:1 scope, really? In case it's needed - everybody will lay to chain/nylon anyway, not having so much chain, so discussion seem pointless.

Boat surging because of wind as main problem?
50 foot, high freeboard 18 ton yawl, high rig, plenty of 'aerodynamic drag'. In flat water but in wind, up to F6-8 with lots of gusts and veers was lying steady, not a slightest "surging". Traditional boat and two sticks, light modern would be different perhaps - worthy to remember boats are not made equal.

With waves though it was another matter, and this was when anchor might drag. Waves, not specially big, were moving her - even with no wind.
We used 8mm chain for such a boat hi-tensile. It was too light, yes, catenary visibly too small. 5:1 scope, on Danforth (easy to trip I heard). No snubber, nor warp. No problems. So how this relates to calculations provided?

Anchoring with such (11:1) scope, in 5 meter depth?
We would rather not stay in 5 m having 2,5 m draft How much scope (and rode to carry) is sensible in 10-20 m? 11:1?

 

[oldbilbo]

Interesting calculations in the link...... but missing some practical points.

Most would agree.

Coincidentally, I'm re-reading today Annie Hill's account of their junk-rigged schooner 'Badger' dragging in 'woollies' - violent squalls - in Port Stanley, Falklands, even with their BIG Luke laid and well set. This both surprised and unsettled them, for they'd believed their Big Fisherman to be just about bomb-proof when deployed.

I suppose the answer is that no anchor setup is entirely reliable, and that's the age-old reason for an anchor watch, not leaving the boat unattended, and having a sketched set of anchor bearings on the chart table together with a simple plan for 'how do we get out of here at silly o'clock, in the dark and driving rain, when here becomes untenable...'. Am I the only mad fool who still does that before getting my head down?

One further suggestion. Where a nylon warp is spliced onto the end of the anchor chain, there is more than a little potential for the nylon to experience accelerated wear and chafe. This join would benefit from being sleeved in a tubular length of anti-chafe firehose, sized to fit and tied in place, in the same way as the warp is best sheathed where it runs over the bow fairlead. Belt and braces? You betcha....

 

[William_H]

The advice on anchoring is good however .... You do not want to overload your boat in the bow with too much weight. It will exacerbate pitch and generally make the boat sluggish. Secondly you need anchor gear that you can manage by hand because you do not have a winch. These 2 factors will dictate max weight of chain and anchor. If you simply look at the geometry of angle of rode at different ratios of depth to rode length you can see that less than 3 times is really a bad angle . 5 times is much better but beyond 5 times you get little improvement in angle for more rode. This of course is not the only factor but this angle of pull will determine if the anchor holds. It is the way you pull the anchor out after all.
I am no expert on anchoring but would suggest that you need a chain that is strong enough (not usually a concern) You need enough chain to clear the bottom and heavy enough to hold it down and you need lots of rope to allow for emergency anchoring in deep water. Beyond that I would go for a bigger anchor ie larger digging area than more or heavier chain. All commensurate with manageable weight. good luck olewill (who hasn't anchored for many seasons)
Funny here in Oz it is always assumed /specified that you will carry about 10 metres of chain and all the rest is rope. Government regs and AYF rules.