Anchor rode.

Bristolfashion

Bristolfashion

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I've been whiling away the lockdown planning my new anchoring system. I was interested in whether I can downsize slightly to 7mm, high test chain from 8mm.

I've run just about every rule of thumb available. If I use Nigel Calder's approach, I get this for my proposed rode :

Load at 42knts wind speed : 598kg
Working load limit (wll) 7mm high test chain : 765kg
Wll 12mm anchor plait : 825kg
Wll Shackle : 750kg
Wll Kong 6-8mm swivel : 625kg

Which suggests that the set up is fine but that no benefit is gained by 8mm chain / 14mm rope as the same swivel would be used & it has the lower rating.

We also conclude that, whilst the swivel is great for most situations, in a manure / fan experience, removing the swivel would be advantageous. Working the numbers, that might increase the acceptable wind speed by 4knts to 46knts.

For higher wind speeds, our back up rode of 14mm/8mm with no swivel (which won't go through a winch) might be expected to cope with winds to 49knts.

After that ..........!

P.s. we are coastal cruisers and not expecting to endure an exposed anchorage in high wind speeds.
 
If you changed chain size would you have to change windlass gypsy?

When I changed my anchor and rode I got a Kong swivel because it seemed a good way of attaching the anchor but close reading of the instructions suggests a shackle to allow for lateral forces which seems to defeat the point of the swivel?

How is the rope spliced to the chain? Is this as strong as elsewhere in the set up?
 
Thanks for your reply.

It's a new windlass, so no problems with gypsy size.

The rope / chain splice should be strong, but obviously gets close inspection on each deployment. I've never had one fail.

The problem with lateral forces are dealt with by having 3 links of 10mm chain between the swivel and the anchor shackle - this set up is shown well on Jimmy Greens website.
 
Have a read of Neeves posts on this forum. He uses 6mm chain on his 40ft cat. If I was redoing my anchor system I would go for 6mm chain now rather 8mm chain. The lighter weight of chain means I could have my whole rode in chain rather than chain rope mix.
 
I though of the same for my 27ft LM27, but trying out a test length of 7mm made me realise the gypsy drum would not work with it.

More seriously might be that 7mm costs much more and when I calculated the reduction in weight it was only about 10kg. Hardly going to make any difference to her sailing ability. I might as well just move the old rubbish under the fore peak bunks and stick them to slide about under the cockpit floor
 
It would help if you tell us the boat type and size. I'm guessing 10-11 meters? ABYC H-40 says 1400 pounds for 30 feet at 42 knots. If yes, 7mm G43 chain and such is about right (Neeves is G70). Remember, this also depends on snubber practice, and Neeves uses long, soft snubbers.
 
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thinwater said:
It would help if you tell us the boat type and size. I'm guessing 10-11 meters? ABYC H-40 says 1400 pounds for 30 feet at 42 knots. If yes, 7mm G43 chain and such is about right (Neeves is G70). Remember, this also depends on snubber practice, and Neeves uses long, soft snubbers.
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Sorry, I thought I'd do a brief post rather than overloaded with detail, but it's a Sadler 29 (8.5m), not heavily laden.

On my last boat I had 6mm/12mm set up and found that all the chain plus the water depth in rope or so (27m chain) so often felt about right and took the shock out of the system - I obviously had a good long snubber for chain only / very short rope out situations. This was in Australia where one rarely has tight anchorages.
 
Remember that if you use lighter chain, you lose the benefit of catenary, and to compensate, you should use a long stretchy snubber. Intrigued at your maximum wind of 42 knots. The most I've had at anchor is 74 knots. ?
I don't use a swivel, but I do have what I call a 'bent link', which ensures that as soon as said link comes up to the bow roller, the anchor is automatically rotated to the correct orientation.
 
NormanS said:
Remember that if you use lighter chain, you lose the benefit of catenary, and to compensate, you should use a long stretchy snubber. Intrigued at your maximum wind of 42 knots. The most I've had at anchor is 74 knots. ?
I don't use a swivel, but I do have what I call a 'bent link', which ensures that as soon as said link comes up to the bow roller, the anchor is automatically rotated to the correct orientation.
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I'm assuming 74knts would be a gust, not wind strength? If it's gusting 74, you could expect wind speeds around 50knts +.

42knts is from the ABYC table & is the suggested point for coastal or ocean cruisers whereas long-distance cruisers should consider up to 60knts. I guess it's all about how much shelter is around & the ability to run to safe harbour. We've certainly anchored when general wind speeds were higher, but the actual speeds at our sheltered anchorage were more acceptable. As a UK coastal cruiser, I'd never expect to anchor in a position & with a forecast that led to a sustained wind speed of 60knts plus gusts (or, to be honest, 40knts +)

To be really sure of security in a plus 60knt wind I'd need to look at 1" rope and 12mm chain - huge on a 8.5m boat. I think at that point, something else would break! In open seas the max probable wave height is 16m!
 
You lack clarity in your description of your windlass. You say its a new windlass. If you mean it is not yet purchased or you can change it well and good - you can then buy a windlass with the gypsy to match your chain (or change the windlass). If its installed then the windlass has a 'fixed' gypsy which you can change at some considerable cost. A 6mm, or 7mm or 8mm chain needs a gypsy to match - they are not universal.

As I mention gypsies are expensive, very! Check the cost of the gypsy as this may cool your enthusiasm for changing from 8mm to anything else. Until you clarify this - we are recommending and passing comments on a change you may decide is not feasible. Most windlass will take a gypsy the next size up or down. If you already hav e the swivel - fine - other wise send a PM to NormanS and he will provide a much better option or:

How to boomerang your anchor right back at you - MySailing.com.au

I believe Viking anchor now sell these. www.vikinganchors.com mail order

and for an introduction to snubbers

The art of snubbing, in the nicest possible way - MySailing.com.au

The best snubbers, and cheapest, are climbing ropes retired from climbing gyms.

We are using a 6mm G70, made in Australia, and a bridle of 12mm x30m (each arm) bridle made from climbing rope. We will be downsizing the bridle we have just received, yesterday, 30m x 10mm x2 rope which we will install tomorrow. Our yachts is a 38' cat 7t.

Personally I would not bother to change from 7mm from 8mm (as mentioned above) - I'd downsize to G70 x 6mm. You then enjoy a decent weight saving and can carry more chain, and not need a mixed rode (as you can introduce a snubber). 6mm chain will take up much less room in your chain locker so carrying a bit more than you do currently is feasible.

Jonathan
 
Lucy52 said:
Sorry for the drift , but does anyone know where to buy to buy the "bent link" mentioned by NormanS, sometimes called a banana link. Preferably in the UK.
Click to expand...

See post 11, Viking Anchor I beleive has them on their website.

Bristolfashion - you mention changing to High Test chain. High Test chain is an American terminology and would also be called G43. G43 has a WLL based on a safety factor of 3:1 whereas metric chain, G30 and G40 has a WLL based on a safety factor of 4:1. The WLL of G43, or High Test chain, is thus artificially, or arithmetically, high. Note also that shackles can be sold to safety factors of 5:1 or 6:1. To make sure everyone is further confused CMP sell their Yellow Pin shackles to a metric specification but sell their Black Pin shackles to an Imperial specification - so a 2t Black Pin shackle is sold to a SHORT ton spec, not metric ton. For you shackles I strongly recommend you buy Crosby G209a shackles (available fro. many sources in the UK, I get mine from Tecni in the UK.

Either you should recalculate the WLL so that you compare like with like or look at the minimum break strengths.

The reason that G43 has a safety factor is that it is used, or was used, as a Transport Chain, and Americans for reasons lost in the mists of time used a different safety factor. Most metric chain all uses the same safety factor of 4:1 EXCEPT Maggi used to sell their G70 with a safety factor of 5:1.

If you are looking at replacing 8mm metric c chain with a G43 imperial chain of 7mm it might fit your gypsy (though I doubt it) - the only way to check is to try it. Take the gypsy off, take it to your nearest chandler and try it. Alternatively beg 300mm of the chain you want to buy (you may need to buy the 300mm) and try it for fit on your gypsy.

Jonathan
 
Bristolfashion said:
I'm assuming 74knts would be a gust, not wind strength? If it's gusting 74, you could expect wind speeds around 50knts +.

42knts is from the ABYC table & is the suggested point for coastal or ocean cruisers whereas long-distance cruisers should consider up to 60knts. I guess it's all about how much shelter is around & the ability to run to safe harbour. We've certainly anchored when general wind speeds were higher, but the actual speeds at our sheltered anchorage were more acceptable. As a UK coastal cruiser, I'd never expect to anchor in a position & with a forecast that led to a sustained wind speed of 60knts plus gusts (or, to be honest, 40knts +)

To be really sure of security in a plus 60knt wind I'd need to look at 1" rope and 12mm chain - huge on a 8.5m boat. I think at that point, something else would break! In open seas the max probable wave height is 16m!
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Sustained wind was over 60 knots. In Loch Seaforth, Isle of Lewis. Month of June, some years ago. Wasn't even a named storm. We get weather.
 
Neeves said:
See post 11, Viking Anchor I beleive has them on their website.

Bristolfashion - you mention changing to High Test chain. High Test chain is an American terminology and would also be called G43. G43 has a WLL based on a safety factor of 3:1 whereas metric chain, G30 and G40 has a WLL based on a safety factor of 4:1. The WLL of G43, or High Test chain, is thus artificially, or arithmetically, high. Note also that shackles can be sold to safety factors of 5:1 or 6:1. To make sure everyone is further confused CMP sell their Yellow Pin shackles to a metric specification but sell their Black Pin shackles to an Imperial specification - so a 2t Black Pin shackle is sold to a SHORT ton spec, not metric ton. For you shackles I strongly recommend you buy Crosby G209a shackles (available fro. many sources in the UK, I get mine from Tecni in the UK.

Either you should recalculate the WLL so that you compare like with like or look at the minimum break strengths.

The reason that G43 has a safety factor is that it is used, or was used, as a Transport Chain, and Americans for reasons lost in the mists of time used a different safety factor. Most metric chain all uses the same safety factor of 4:1 EXCEPT Maggi used to sell their G70 with a safety factor of 5:1.

If you are looking at replacing 8mm metric c chain with a G43 imperial chain of 7mm it might fit your gypsy (though I doubt it) - the only way to check is to try it. Take the gypsy off, take it to your nearest chandler and try it. Alternatively beg 300mm of the chain you want to buy (you may need to buy the 300mm) and try it for fit on your gypsy.

Jonathan
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The windlass is new and sized to match the chain. There was no windlass on the boat before, just a retrieve by hand set up - 8mm chain & 14mm rope.

The gypsy will run DIN 7mm chain plus the various 6mm specs should we desire.

I may have used the terms high test / G40 in a sloppy fashion - the calcs were all based on actual test figures from the proposed components rather generic figures.
 
Lucy52 said:
Thank you Neeves, "Boomerang" ordered.
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You are most welcome.

I'd forget average wind - if you had average wind your yacht would sit there at the end of its tether simply subject to windage. What actually happens is your yacht veers about and suffers snatch loads and and further suffers because of wind sheer, bullets coming from directions that are not the average. Its not the wind speed and windage you need to think of but the acceleration of your yacht impacting your rode when it comes to the end of its tether. To mitigate the forces you either need a decent length of heavy chain or a decent snubber or both. The snatch loads can be frightening if not 'managed'. A large snatch might lift your anchor out, result in divorce proceedings commenced or a crew mutiny (or all three :(. ).

Just remember that as the wind increases the advantage of your catenary increasingly reduces. A correct;y sized snubber will continue to work, roughly linearly, until it fails.

The reality is you are using both the catenary and elasticity together. A mixed rode will commonly have a textile portion with not much elasticity - the textile p[ortion is simply too thick (because it is sized for strength).

For an indication on actual loads or tensions read this:

Anchor Testing and Rode Loads - Practical Sailor

Jonathan
 
Bristolfashion said:
Thanks for your reply.

It's a new windlass, so no problems with gypsy size.

The rope / chain splice should be strong, but obviously gets close inspection on each deployment. I've never had one fail.

The problem with lateral forces are dealt with by having 3 links of 10mm chain between the swivel and the anchor shackle - this set up is shown well on Jimmy Greens website.
Click to expand...
"...problem with lateral forces IS dealt with by having ...." Nothing personal, Bristolfashion, but I despair at the abysmal standard to which English Grammar has descended. They don't seem to teach it properly any more.
I constantly see and hear plural verbs thrown mistakenly into main clauses whenever a plural appears in a subordinate clause.
( Apologies for thread drift)
 
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Bristolfashion said:
The windlass is new and sized to match the chain. There was no windlass on the boat before, just a retrieve by hand set up - 8mm chain & 14mm rope.

The gypsy will run DIN 7mm chain plus the various 6mm specs should we desire.

I may have used the terms high test / G40 in a sloppy fashion - the calcs were all based on actual test figures from the proposed components rather generic figures.
Click to expand...

It is possible to buy Imperial chain, G43, in the UK - so I was really just questioning.

I confess some amazement that the gypsy will accept both 7mm and 6mm chain to metric specifications. But if you have been assured this is the case then even though it must be true - I'd double check by taking the gypsy in and trying it. Once you have a length of chain - its yours! unless you buy the chain from the people who defined the gypsy and assured you it fitted both 6 and 7mm. Some gypsies are more forgiving than others

I've never seen 7mm chain so I am talking from total ignorance :) - but hey its the internet why should ignorance come into it :)

But I would check - its simply too expensive if someone has made some slick comment (like me!)

Jonathan
 
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Spirit (of Glenans) said:
"...problem with lateral forces IS dealt with by having ...." Nothing personal, Bristolfashion, but I despair at the abysmal standard to which English Grammar has descended. They don't seem to teach it properly any more.
I constantly see and hear plural verbs thrown mistakenly into main clauses whenever a plural appears in a subordinate clause.
( Apologies for thread drift)
Click to expand...

You might want to check that capitalized first letter in 'grammar'.
 
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