Anchor weights and connectors

[charles_reed]

A valid point

The weight of a boat will determine the amount of "snatch" it transmits down the chain to the anchor.
This is the most ubiquitous factor in causing an otherwise well-dug-in-anchor from coming adrift.
That snatch can be reduced considerably by fitting a length of high-hysteresis rode into the system.

Unfortunately light boats, especially those with an underwater profile such as the Bavaria are far more likely to shear about than heavy, long-keel boats with a lower topsides.

Unfortunately any discussion on anchoring seems to degenerate into a simplistic examination of anchor design and tackle weights.

IMHO these come way down the scale of criticality as to an effective anchoring system, which is an extremely complex dynamic, in which the most important factor is the nature of the bottom.

Still I only anchor about 180 times a year....

 

[vyv_cox]

Re 'What do you think of these?'

The problem with all the ones I can see is that the chain and anchor are attached to the connector by the same fixings that hold the connector together. In my destructive tests these were always the ones that failed at the lower loads. Kong and Osculati designs are joined by a screw that only has that function. The chain and anchor are connected to forged lugs that form part of the main body. Like this:-

On the question of whether a swivel connector is necessary:
All anchors, with the possible exceptions of a fisherman and maybe a Danforth, have no axial symmetry. When recovering chain with a windlass, many anchors, such as Delta, CQR, spin as they rise through the water, sometimes to a considerable degree. Some windlass gypsies have the ability to allow twisted chain to pass through them, others don't. If the twist passes through the chain will finish up extremely twisted in the locker, so that eventually lowering the anchor beyond a certain depth becomes impossible. If the gypsy does not pass twisted chain it will jam.

Fitting a swivel will help to avoid this situation, although it will not eliminate it entirely. Almost all windlass manufacturers recommend that a swivel be fitted.

 

[charles_reed]

Yes

I' well aware of his site.

The figures his spreadsheets produce bear out, amply, the points I've made.

His caveat about "recent" anchors, such as the Spade, Delta and Rocna (a remake of the Bugel) is IMHO a placatory gesture, if ever I've seen one.

 

[saltwater_gypsy]

Re: Yes

re: Vyv's spinning chain.
If you have about four or five links engaged in the gypsy then the chain must come up and into the chain locker in an orderly non- spinning manner. I can't see how it can twist through the gypsy without jamming on the way up.
Its a good idea however to wait for a moment before docking the anchor to let any built up twist sort itself out.
Do manufacturers really recommend that you fit a swivel?

 

[captainslarty]

Re: Yes

We use a 12mm stainless swivel assembly designed locally for purse trawl lifting.. that uses a 12mm shackle to 65 mtrs of 10mm stainless chain. The trawler stuff is excellent. 34 foot boat, around 10 tons loaded.

 

[vyv_cox]

Re: Yes

<<< then the chain must come up and into the chain locker in an orderly non- spinning manner.>>>

No, it doesn't. I have to untwist the chain in my locker several times in a season, when it reaches the stage that I can't let out more than about 30 metres. Now that I'm in the Med I can see something like 10 metres down and the anchor twists some three or four times in that depth when raising it.

Several windlass manufacturers recommend a swivel. I have a Maxwell and they most definitely do. I have read a few other manufacturers' instructions in the past and can't quote those who do from memory, but some definitely do.

 

[Salty John]

Re: Yes

You make a good point Vyv. I prefer not to use a swivel but every now and again I do like to get all the chain out and restow it.

 

[KellysEye]

>Should i use a swivel or just a shackle?

A shackle, swivels break and are the most common point of failure after shackles that aren't seized (yes there are idiots around).

 

[roly_voya]

I have a very similar setup on a slightly lighter boat and it works fine. Would suggest you add a chain hook and 10m 16 super stretchy line to isolate chain from boat, mainly for sound damping but also stops snatching.

 

[vyv_cox]

<<< A shackle, swivels break and are the most common point of failure after shackles that aren't seized (yes there are idiots around). >>>

The best swivels were considerably stronger than the worst shackles in my destructive tests. Some of the galvanised shackles, all a size bigger than the chain, failed at half the chain UTS. The best stainless shackles were stronger than the chain but the swivels ran them close.

Perhaps I can qualify as one of your idiots. I have never, in well over 20 years of cruising, including full time for the past four years, seized an anchor shackle, nor seen the need. What I have seen is that the screws holding swivels together, which cannot be seized and are difficult to tighten fully, do tend to loosen. Which is why I tested Loctite and found it to be totally satisfactory for underwater use, at least for anchoring.

 

[Abigail]

Hi - I haven't seen the article (out of country), but I think this is interesting. I've seen lots of boats put loads of attention into chain, anchor, technique etc, but can't tell teh breaking load on the swivel or shackle at all. We use a wasi swivel, which is expensive but v strong and well fastened. If we were to anchor in one place for 2 months plus we would replace it in advance with a double galvanised shackle, to reduce salt water corrosion.

Couple of points not mentioned above:

(i) I'm much more comfortable in tidal areas with a swivel. I think the Alain Fraysse material has a caveat somewhere about the impact of tides maybe making a diffference to his recommendations. (this comment is from memory only)

(ii) whether you use galvanised or stainless is partly a funciton of what materials your chain and anchor are made of. If you have a s/s anchor, you might want an s/s swivel.

Generally, I agree that the hold of the anchor on the bottom and the size of anchor are higher considerations but ground tackle, including the dinghy should be considered as a whole system not only as a colleciton of parts.

 

[vyv_cox]

I don't believe that galvanic corrosion between a stainless steel shackle/connector and the carbon steel of either a chain or anchor is a significant problem. There is some loss of galvanising on the final links of the chain but this is hardly a big issue. Aerosol galvanising spray seems to work well: I did my anchor at the beginning of last season and it still looked good at the end. I will do the end of my chain with it this year.

For reference, I have lived aboard all summer season for the past four years and normally anchor for most of six months.

 

[charles_reed]

I use

< 10m of 16mm Octoplait with a Wichart chain shackle.

The textile rode has transformed my boat's anchoring success rate.

 

[charles_reed]

saltyjohn, don\'t know

where you got your forces from, but I'd beg to differ:-

a) the static load, as reported, is far greater
b) no allowance is made for "snatch" which can increase static load x5.

 

[Dipper]

I believe that the RNLI have used Kong connectors and they have certainly used Osculati swivel connectors.

 

[captainslarty]

I dont know why anyone is messing about with neat swivels / joints etc etc lol.. /forums/images/graemlins/laugh.gif

Heres what ya need... 35 euros... built like a yorkshire toilet..

No worries, sleep sound..

This is the spare connector... just in case I 'break' one... /forums/images/graemlins/smirk.gif /forums/images/graemlins/smirk.gif /forums/images/graemlins/tongue.gif

Pah Humbug...

 

[vyv_cox]

And you trust those welds over a forged component? Sooner you than me.... Not to mention the screw thread where the two parts join together.

I don't know how they build toilets in Yorkshire but I would hope it's better than this.

 

[Salty John]

Re: saltyjohn, don\'t know

I have accumulated a huge amount of information on this subject over the years!
The table on my website is compiled from actually measured values rather than calculated values such as the ABYC figures. The ABYC figures are often 4 or 5 times the loads actually measured in various tests; they use some pretty huge safety factors but never say what they are.
In January 2007 YM printed an anchoring test with measured loads which gave figures about 30% less than mine, mine being based largely on information from the marine engineer Robert Smith.
I'm satisfied with the validity of my numbers.
My suggestions for ground tackle are in line with the MCA recommendations, and have proved to be good choices for my own boats.

 

[vyv_cox]

Re: saltyjohn, don\'t know

You may be quoting some of your figures from an 'Experts advice' piece that I wrote in YM last year. I carried out a good deal of research for this article, including exchanging several e-mails with Prof. John Knox, who possibly knows more about this than anyone.

As you say, the ABYC values are very high, with no real explanation as to why. The expression derived by John Knox agrees very well with measured values using Anchorwatch load cells. The earlier YM article quoted actual measurements over two years of almost daily anchoring and I also corresponded with the author of that.

Actual loads measured are a lot less than people imagine, and this clearly takes snatching into account for the most part. Calculated loads in the thousands of pounds appear to be way over what is actually the case. I clearly recall hauling in chain the hard way, before I owned a windlass, in winds of force 6. According to ABYC I am Superman!

 

[captainslarty]

Hi Vyv, absolutely YES, I do.. they are superb.

and cost effective,, and safe.. Size matter lol

oe