Bow shackles

[ip485]

I need to replace the anchor shackle and am uncertain what I need.

The anchor is a Rocna 55KG so hopefully heavy, large and powerful. The yacht is around 22 tons. The ground tackle all chain. The aim is ground tackle that will cope with "anything", so I dont want the shackle to prove to be literally the weakest link.

So firstly what breaking strain would forum mites recommend.

Secondly, I want to avoid a conventional pin because it inevitably catches on the cheeks of the anchor guide (I have that type at the moment). That leaves countersunk D type, a bullet swivel anchor shackle or a green pin nut and bolt type. The swivel has the cleanest lines but I know some feel they are not up to the job. Is that true of every make - what about the Kong range? Then the green pin type seem more secure than the countersunk but not as streamlined as either of the other two.

Opinions welcome please.

 

[sarabande]

give the Crosby shackle people a call ?

http://www.atrgroup.co.uk/product/safety-bow/

 

[ganter]

Firstly your concern is strength with that weight of anchor and rig.

Secondly, a non protruding pin to run fair through your cheeks.

Go for this...



You tighten the pin with an allen key - but that's fine as it will seldom, if at all, be loosed.

Choose carefully...some are weight rated and some aren't but that would be what I'd go for.

 

[prv]

I dont want the shackle to prove to be literally the weakest link.

In that case, the obvious answer is to get one with a breaking strain equal to (or preferably greater than) the breaking strain of the chain. Simples. Don't go by guesswork or what "some people feel".

What is the breaking strain of your chain?

(I say breaking strain rather than SWL because the safety factor is often not stated, and may vary. But as far as I know, breaking is breaking.)

Pete

 

[Seajet]

Firstly your concern is strength with that weight of anchor and rig.

Secondly, a non protruding pin to run fair through your cheeks.

Go for this...

View attachment 40112

You tighten the pin with an allen key - but that's fine as it will seldom, if at all, be loosed.

Choose carefully...some are weight rated and some aren't but that would be what I'd go for.

My worry with that shackle is I can't see a way of mousing it with monel wire; sure one could apply Loctite, in my time grade 290, but I'd much rather have a physical rather than frictional restraint on the thing coming undone - sorry but I wouldn't trust it with my pride and joy.

 

[NormanS]

Why do you want to use a Bow shackle? A Dee shackle is stronger.
Unless you have a large link on the end of your chain, just use the biggest shackle whose pin will go into the last link.
You can also buy "Cable shackles", which have a shaped pin, (i.e. not round), which is kept in place with a tapered pin, which in turn is kept in with a lead plug. These last, have no protruding heads, and may be your best bet.

 

[prv]

My worry with that shackle is I can't see a way of mousing it with monel wire; sure one could apply Loctite, in my time grade 290, but I'd much rather have a physical rather than frictional restraint on the thing coming undone - sorry but I wouldn't trust it with my pride and joy.

If you have a narrow bow roller like I do then you don't have much choice. I have a similar shackle (though D rather than bow) as it's the only type that will fit.

I applied suitable loctite (can't remember the grade off-hand now) to the thread and also centre-punched the joint between pin and body on the head side. I thought of tack-welding it as well but I thought the heat might change the properties of the metal (re corrosion or strength) and since it was a special high-strength material (possibly heat-treated too) I didn't want to mess with that.

Pete

 

[Seajet]

Pete,

I agree in those circumstances you don't have much choice, apart from maybe a mid-long term plan to change the stemhead fitting.

In reality probably fine for weekends and holidays, though might not suit a born worrier like me !

For long distance & really serious anchoring I suspect we'd both like something different.

 

[estarzinger]

Take a look the the wichard rapide shackles. They are oval in shape and slide into narrow anchor rollers very nicely. I don't know what chain size you have but the 7/16 rod diameter rapide will fit thru 3/8" g4 chain and has a higher breaking strength than the chain.

I have used one for 16 years, 50kg anchor, decently "serious" anchoring.

 

[Salty John]

Use a bow shackle of equal or greater breaking strain to the chain - it will probably be stainless steel.

Find one in which the bow, not the pin, will fit through the link.

Put the pin through the anchor shank, using loose washers to locate the anchor in the centre of the pin.

View attachment 40115

 

[prv]

Use a bow shackle of equal or greater breaking strain to the chain [...]

Find one in which the bow, not the pin, will fit through the link.

Chances are that those two will be mutually exclusive.

Pete

 

[Salty John]

Chances are that those two will be mutually exclusive.

Pete

Which is why you sometimes need to specify a large end link, as offered by good chain manufacturers.

 

[GHA]

Use a bow shackle of equal or greater breaking strain to the chain - it will probably be stainless steel.

Find one in which the bow, not the pin, will fit through the link.

Put the pin through the anchor shank, using loose washers to locate the anchor in the centre of the pin.

View attachment 40115

Normally good advice but Ronca for one has a slot in the shank which allows the shoulder of the shackle to pass through so the pin attach to the chain and the body to the shank, this means when the boat veers around the shackle can spin so there's no side load on the shackle. Not sure if other shanks are like this but a really good simple idea.

 

[vyv_cox]

For a large application like the OP's there may not be a suitable Wichard countersunk shackle. Several people have contacted me to say they had trouble in locating them in 12 mm and above sizes. A Kong or Osculati connector, fixed if you don't want a swivel, would probably have sufficient strength. There is a lot of information about chain strength at http://coxengineering.sharepoint.com/Pages/Chaindefinitions.aspx and on shackles and connectors at http://coxengineering.sharepoint.com/Pages/Connectors.aspx

I have used Loctite 242 for several years now on countersunk shackles, after testing it and finding it very effective. After a season of anchoring I can detect no relaxation of the pin in my shackle.

 

[Salty John]

Normally good advice but Ronca for one has a slot in the shank which allows the shoulder of the shackle to pass through so the pin attach to the chain and the body to the shank, this means when the boat veers around the shackle can spin so there's no side load on the shackle. Not sure if other shanks are like this but a really good simple idea.

I don't understand how a slotted hole in the anchor shank, such as Danforth has had forever, changes the best practice for rigging chain. Perhaps I'm misunderstanding the arrangement.
A shackle must be loaded in line with the pin - for a load 45 degrees off centre you have to downrate to 70% of SWL and for 90 degrees by 50%. Having the chain on the pin cocked against the side of the shackle isn't allowed with any amount of downrating.
That these odd ball off centre arrangements work is down to the fact that the weakest part of the system is the anchor's hold on the seabed, except when it's fouled. Only in such a case does the weak point move elsewhere, usually to the shackle or a rope to chain joint.

 

[GHA]

I don't understand how a slotted hole in the anchor shank, such as Danforth has had forever, changes the best practice for rigging chain. Perhaps I'm misunderstanding the arrangement.
A shackle must be loaded in line with the pin - for a load 45 degrees off centre you have to downrate to 70% of SWL and for 90 degrees by 50%. Having the chain on the pin cocked against the side of the shackle isn't allowed with any amount of downrating.
That these odd ball off centre arrangements work is down to the fact that the weakest part of the system is the anchor's hold on the seabed, except when it's fouled. Only in such a case does the weak point move elsewhere, usually to the shackle or a rope to chain joint.

If you have the pin through a hole in the shank and side load the bow you are side loading the pin, if you have the bow through a slot in the shank and side load then the shackle can spin in the slot so the load is still in line between the pin and the bow of the shackle. All the slot does is let you get the shoulder of the shackle through the shank so the bow is attached to the shank and the shackle can articulate as the boat veers from side to side.


Edit:re reading your post, having to derate a shackle for side loading is exactly why you should have the bow through the shank and not through the chain. With the diameter of a chain link the point of contact can never be far off centre of the link so the angle is forced to be always close to zero. A pin through a hole in a shack is constrained by the pin diameter vs hole diameter and quickly become side loaded.

Pic might make more sense.. Impossible to side load the pin by more than a degree or so if at all..

 

[GeorgeLlewellin]

For a large application like the OP's there may not be a suitable Wichard countersunk shackle. Several people have contacted me to say they had trouble in locating them in 12 mm and above sizes. A Kong or Osculati connector, fixed if you don't want a swivel, would probably have sufficient strength. There is a lot of information about chain strength at http://coxengineering.sharepoint.com/Pages/Chaindefinitions.aspx and on shackles and connectors at http://coxengineering.sharepoint.com/Pages/Connectors.aspx

I have used Loctite 242 for several years now on countersunk shackles, after testing it and finding it very effective. After a season of anchoring I can detect no relaxation of the pin in my shackle.

Your website pages contain a lot of really useful specialist information which can be difficult or impossible to obtain elsewhere.

But have you ever tested this swivel anchor connector which turns an anchor like a CQR around so that is stows correctly.

http://www.securefixdirect.com/6-8m...tor-stainless-steel---marine--boat-4040-p.asp

Also available from a number of other sources. This worked really well on my brother’s boat.
Thanks George

 

[alahol2]

Take a look the the wichard rapide shackles. They are oval in shape and slide into narrow anchor rollers very nicely. I don't know what chain size you have but the 7/16 rod diameter rapide will fit thru 3/8" g4 chain and has a higher breaking strength than the chain.

Agree look at maillon rapide on the S3i site. Very strong and neat solution. Has a certain amount of 'fail safe' inherent in the design. Been using for the last 15+ years.

 

[vyv_cox]

But have you ever tested this swivel anchor connector which turns an anchor like a CQR around so that is stows correctly.

http://www.securefixdirect.com/6-8m...tor-stainless-steel---marine--boat-4040-p.asp

Also available from a number of other sources. This worked really well on my brother’s boat.
Thanks George

I cannot tell whether yours is the same make, but I tested this one from Osculati that looks very similar.

It is connector E in the table on this page of the website http://coxengineering.sharepoint.com/Pages/Connectors.aspx Failed at 4.39 tons, which is a lot better than Grade 30 chain and well into the Grade 40 range.

 

[Poignard]

Which is why you sometimes need to specify a large end link, as offered by good chain manufacturers.

eg Griff Chains Ltd (made in England).

I would tighten up the pin, rivet over any protruding thread or centre-pop around it, then saw the eye off.