Here we go - another anchor thread!!

[Hurricane]

Now that I've got a spanking new Rocna anchor, I've been wondering how to fit it.
Out in Sardinia last summer, MYAG showed me his set up and how he connects his anchors.
He also pointed me at Vyv Cox's site here https://coxengineering.sharepoint.com/Pages/default.aspx

Currently, we use an Osculati "The Twist" swivel see here - http://www.osculati.com/en/cat/Scheda.aspx?id=245
The idea is that this swivel always brings the anchor up the correct way round.
It has worked well apart from recently "jack knifing" a few times round the anchor shaft.
I have a messy fix/solution to the "jack knifing" - just bundling some shackles in fixes the problem.

Recently, I've been thinking.
If I leave the Osculati Twist Swivel connected, maybe it will break (being the weak link in the chain - excuse the pun) and I would hate to loose my lovely new anchor.

So, I've been doing some research and there are some mixed views out there.
Quite a number of people say don't use swivels at all if you can manage without them.
Which is what I am starting to think we should do.

So the first question is what is the best shackle for the job - 12mm chain onto a 55kg anchor.
Should it be stainless - should it be galv - D shackle or Bow etc....
And where is the best place to get them?

Vyv's site is very good - showing the tests that he has carried out - but I am having difficulty working out what shackle would be best for my situation.

If I can't manage without a swivel, maybe the time has come to ditch the Osculati Twist.
In which case what swivel should I use - again Vyv's site kind of suggests a Kong swivel but is that the best?

Any views would be gratefully accepted.

 

[jfm]

I don't see why you don't carry on with the osculati banana Hurricane. It's a great bit of kit. And a fat shackle, high quality forged from witchard or similar, to attach it to the anchor shank. Eg a 11205 from their catalogue, or whatever will fit. Assemble with Loctite of course. W also do titanium shackles but hardly necessary for your loadings which will rarely exceed 2 tonnes

FWIW I just bought an Ultra straightener, because the osculati banana is too long (It tries to go around a roller in my boat!) but you don't have that problem in JW, so stick with the Osculati banana. I haven't installed the Ultra yet but it is a nice bit of kit

 

[julians]

I had a swivel (not sure on brand , but it was fitted as standard equipment by the dealer/manufacturer) fail early last year (atfer 7 years use) , costing me an anchor.

I replaced it with a Kong swivel, which looks a much more robust design, but having only had it for 2 seasons, cant comment on longevity.

 

[Deleted User YDKXO]

The only problem I found with the Osculati Twist is that it operates quite violently and the bigger the anchor the more damage that can do. When I changed up to a 60kg Delta on my current boat, I started with the Twist attached but after a couple of uses, the violent twist of the heavier anchor damaged the bow roller and I removed the Twist. I have also used the Kong swivel and yes it works OK but you have to keep an eye on it because there are stories on the internet about failures eg http://www.latitude38.com/lectronic/lectronicday.lasso?date=2009-05-15#.VkD2ztBWRuE Certainly the 'cheeks' of the first Kong I bought started to splay out after a couple of seasons and I thought it prudent to replace it

Actually there's some good advice on the Rocna site about avoiding lateral loads on in line swivels http://kb.rocna.com/kb/Swivels and their advice to put a short length of chain between the swivel and the chain looks sound

A good technique for turning an anchor around the right way is simply to leave it hanging just below the surface of the water and going astern. It works first time for us nearly all of the time and if it doesn't work first time, it works second time!

 

[jfm]

A good technique for turning an anchor around the right way is simply to leave it hanging just below the surface of the water and going astern. It works first time for us nearly all of the time and if it doesn't work first time, it works second time!

Yup, especially with an AnCam Mike :encouragement:

 

[MapisM]

their advice to put a short length of chain between the swivel and the chain looks sound

You mean between the swivel and the anchor, I suppose?
If so, I suspect it might be difficult for Hurricane, because he doesn't have a lot of space on JW between the bow roller and the winch, and he wanted to fit also a lock in between, like MYAG has.

 

[jimmy_the_builder]

The only problem I found with the Osculati Twist is that it operates quite violently and the bigger the anchor the more damage that can do. When I changed up to a 60kg Delta on my current boat, I started with the Twist attached but after a couple of uses, the violent twist of the heavier anchor damaged the bow roller and I removed the Twist. I have also used the Kong swivel and yes it works OK but you have to keep an eye on it because there are stories on the internet about failures eg http://www.latitude38.com/lectronic/lectronicday.lasso?date=2009-05-15#.VkD2ztBWRuE Certainly the 'cheeks' of the first Kong I bought started to splay out after a couple of seasons and I thought it prudent to replace it

Actually there's some good advice on the Rocna site about avoiding lateral loads on in line swivels http://kb.rocna.com/kb/Swivels and their advice to put a short length of chain between the swivel and the chain looks sound

A good technique for turning an anchor around the right way is simply to leave it hanging just below the surface of the water and going astern. It works first time for us nearly all of the time and if it doesn't work first time, it works second time!

Yup, especially with an AnCam Mike :encouragement:

I also had the same issue with the distal end of the Kong swivel flaring after a few seasons use, so I replaced with an Osculati banana. You're right that it will bang the anchor around a bit if you just recover it blind - but this is one of those situations where the ancam is invaluable - when you see the shank arriving at the bow roller, you just slow the whole recovery down and bring the anchor home really slowly (by modulating the windlass button). Works perfectly every time; no arsing about going astern

 

[Hurricane]

Thanks everyone

The Osculati banana does work fine with the current 40kg Delta but it does sound a bit alarming as it hits the bow roller.
I'm wondering if that will be too much for it with the extra load of the new 55kg anchor.
Here is a pic I took years ago when it was new.

Everything relies on that "T" shaped piece of metal.

MAPISM
I've measured it all with the chain lock in place and there is just enough room for the Osculati banana and the chain lock.
I haven't fitted the chain lock yet - I want to see how well it fits with the new anchor which is still here in Devon.
Won't be taking it out until about Feb next year.

But I'm now thinking that I will position the chain lock as if I were going to use the Osculati banana but not fit anything other than a strong shackle.

My thoughts are that the new anchor might dig in so much that it will be a struggle to get it out - especially in the mud of our local lagoon.
You should see the size of this thing - it is in my garage and I can only just lift it.
The idea is that if this happens, SWMBO can simply flip the latch on the chain lock and the engines could break the anchor out.
With that kind of load, I'm wondering if the Osculati banana swivel will cope.
Thats my thoughts anyway.

 

[jfm]

Everything relies on that "T" shaped piece of metal.

Yep but it's quite some bit of metal hurricane. I don't know the diameter nor grade of s/s nor whether forged but yield strength will be in the order of 50 tonnes per square inch. I bet your anchor chain has never seen more than 2-3 tonnes of tension briefly in its whole life

 

[Hurricane]

I bet your anchor chain has never seen more than 2-3 tonnes of tension briefly in its whole life

Even if it gets stuck and I'm pulling with the engines?
OK, I don't mean stuck in rocks but I'm worried that the force in thick mud might be considerable.

Actually, I was hoping that you would say that - I was thinking the same.
But this little T piece does seem to be the "weak link in the chain".

 

[Nick_H]

Mike, the Vyv Cox test shows that an anchor rode made up of 8mm galv chain, a 6/8 mm Osculati twist, and a 10mm shackle, will be well matched, ie. the three elements all have broadly the same tensile strength.

I can't see any reason why these results wouldn't scale up to your chain size, as in each case the Twist is being used with the larger size of chain in it's range, so in tensile at least I don't see the twist as being a weak link in your set-up.

If I have any concerns about the Twist it's more around stress corrosion cracking in the area you highlighted, because I don't really understand how and why it occurs, and it's almost impossible to spot with the naked eye even if you strip the Twist down to inspect it. The only answer I can think of is to replace it every few years.

 

[julians]

The Kong swivel uses a similar mechanism to the osculati to provide the actual swivel action.

 

[Deleted User YDKXO]

You mean between the swivel and the anchor, I suppose?

Like this picture

http://kb.rocna.com/kb/File:Swivel_in-line-with-chain.jpg

I think Rocna are quite right. What causes the problems with these swivels is the lateral loading on them when connected directly to the anchor shank. I guess all you need is a couple of chain links between the anchor and the swivel to stop this

 

[Deleted User YDKXO]

Even if it gets stuck and I'm pulling with the engines?
OK, I don't mean stuck in rocks but I'm worried that the force in thick mud might be considerable.

Mike, in 2 seasons, we've never had an issue raising our 60kg Delta using the winch only and in the right conditions I've seen this anchor dig itself well into the seabed. Obviously, you do have to be more careful to manouvre the boat to the anchor rather than allow the winch to pull the boat to the anchor, such that there is minimum strain on the winch. I must say that after many years of patient and sometimes not so patient cajoling, my SWMBO has become quite skilled at pointing out which direction I should move the boat and ensuring that the winch doesn't strain

As I mentioned previously I'm going to try a 55kg Rocna myself next season and I'm not expecting any issues breaking it out

 

[MapisM]

Like this picture

http://kb.rocna.com/kb/File:Swivel_in-line-with-chain.jpg

I think Rocna are quite right. What causes the problems with these swivels is the lateral loading on them when connected directly to the anchor shank. I guess all you need is a couple of chain links between the anchor and the swivel to stop this

Yup, that's what I guessed from your previous post, and I also agree that swivels can be more easily damaged by side loads.
Otoh, such setup takes space in the area between the bow roller and the winch, which is somewhat restricted in many boats, JW not being an exception...

 

[Deleted User YDKXO]

Otoh, such setup takes space in the area between the bow roller and the winch, which is somewhat restricted in many boats, JW not being an exception...

Surprised if there isn't space for an extra 2 or 3 chain links, say 100mm?

 

[Hurricane]

Surprised if there isn't space for an extra 2 or 3 chain links, say 100mm?

In JW's case, I'm fairly sure that there is space for a few links then a swivel then the chain.
MYAG uses this concept - with three chain links between the swivel and the anchor - I think.
I think Vyv's website discusses this - saying that you can use less links if necessary.
IMO, a big consideration is "jack knifing" - this is where the rode passes under the anchor's shaft when deployed (boat swings round etc)
A short length of chain doesn't seem to tangle but the Osculati twist is a real problem in this respect.
When recovering, several times, it has managed to completely lift the anchor with the Osculati twist stuck at right angles under the anchor shaft.
We now know that the best way to fix the problem is to lower the anchor back to the sea bed and start again.
It happened again in In Menorca this year - the whole lot came up twisted but this time, it bent the shackle that fixes the Osculati twist to the anchor shaft.
Being that we were at sea and not intending going into a marina for the foreseeable future, I added a couple of shackles in parallel to the bent one so that I could sleep at night!!
After replacing the bent one, these extra shackles have now ended up as my current solution.
They have the effect of taking up the "sloppiness" of the shackle where it attaches to the anchor so that the Osculati twist cannot possibly "Jack Knife".
Messy solution - but it works.

 

[MapisM]

In JW's case, I'm fairly sure that there is space for a few links then a swivel then the chain.

Well M, you obviously know JW much better than myself - or anyone else, for that matter!
But just to better explain my train of thought, I also assumed that you are still thinking to fit a mechanical chain lock, somewhere between the swivel and the winch.
So, I looked for a pic you posted in another thread - see below.
Now, by moving the Osculati thingie 100mm towards the winch, I can't see enough space left for the lock.
Or did you decide that the lock is unnecessary? Or am I missing anything else, maybe?

 

[Hurricane]

Well M, you obviously know JW much better than myself - or anyone else, for that matter!
But just to better explain my train of thought, I also assumed that you are still thinking to fit a mechanical chain lock, somewhere between the swivel and the winch.
So, I looked for a pic you posted in another thread - see below.
Now, by moving the Osculati thingie 100mm towards the winch, I can't see enough space left for the lock.
Or did you decide that the lock is unnecessary? Or am I missing anything else, maybe?

Ahh - I see your point.
Sorry - my mistake - if I were to use the short chain solution, I would also get a different swivel.
I think I have the answer if I use the Osculati swivel - use the extra shackles - Ughh

My calcs are that the new anchor's shaft will "park" about 80mm further aft.
I intend fitting the chain lock between the Osculati swivel and the windlas - its tight but I think it would work.
If not (and I want to try this first) I will scrap the Osculati and just fix the chain directly onto the anchor with a good (Wichard) shackle.
If we then get problems recovering it or with the chain twisting at the anchor, I will introduce a Kong swivel with a short length of chain.

Sorry for the confusion.

 

[Deleted User YDKXO]

Now, by moving the Osculati thingie 100mm towards the winch, I can't see enough space left for the lock.

Ah yes I see the problem now. I did not appreciate that JW's anchor is held in a hawse pipe rather than a conventional bow roller assembly