Pros & Cons of Dee shackles vs Bow Shackles

[Andrew G]

Spurred on by a recent thread on swivels I’m keen to know forum members’ views on the pros and cons of Dee shackles and Bow shackles in the anchoring system (that is from one end of the rode to the other, and, any places in-between), and any clever tricks you get up to to improve their performance. Cheers, Andrew

 

[Kelpie]

My understanding is that bow shackles are for use where a degree of articulation is required, e.g. joining a mooring riser to a ground chain. In other applications a D shackle is used.

 

[J Neeves]

I understand the concept, bow shackles allow the load to orientate 'correctly' - but the suggestion is that in applications where the orientation is fixed then a 'D' shackle would be used. Does this then mean that 'D' shackles are 'better' - why not use bow shackles in all, or more applications.

Or - Why have 'D' shackles at all (unless they are better) - except they have a 'narrower' profile.

The OP seems to be restricting his question to the anchor rode - given that you might want articulation in almost every application - why not use a bow shackle 'everywhere'

The only location where there is no need for articulation is in the chain locker to secure the bitter end - but even here I'd not use a 'D' but a bit of cordage as I can cut it free (quickly - well relatively so) - so why use 'D' shackles at all?

Jonathan

Ediit

PS are there documented or first hand experiences of 'D' shackle failure that was actually caused by their lack of articulation.

 

[afterpegassus]

Bow shackles can be used for joining two or more components and can take directional loading, whereas a D shackle ought to be used for just two and should be loaded in line

 

[GHA]

Or - Why have 'D' shackles at all (unless they are better) - except they have a 'narrower' profile.

) - so why use 'D' shackles at all?

They're cheaper.

 

[vyv_cox]

I tested quite a collection of both types, results at http://coxengineering.sharepoint.com/Pages/Connectors.aspx. At the time I tried to find some difference between the two designs but I was unable to. I guess it would take a far larger number of samples to be certain but at the moment I suspect that there is little between them.

 

[J Neeves]

Here in Sydney if you go to a lifting apparatus supplier they call bow shackles 'anchor shackles' even though they actually sell them, or the proof tested ones, for lifting and many of them are not HDG. And/or if you ask for an anchor shackle you are immediately offered a bow shackle and never a stainless one - only HDG.

Jonathan

 

[Andrew G]

Thanks for comments so far. As Jonathan asks (and Vyv might too??) are there any observations of them actually performing differently? I must admit that in one of my uses of Dee shackles I put narrow spacers on either side of the pin to keep the chain centred on the pin – seemed to work (but I have since dispensed with that swivel).
Seems to me that bow shackles would pass through the cheeks of a bow roller better than Dee if it wasn’t for that great big pin. Cheers Andrew.

 

[Deleted member 36384]

Bow shackles can be used for joining two or more components and can take directional loading, whereas a D shackle ought to be used for just two and should be loaded in line

This is not true. So called D shackles can be loaded exactly the same as Bow shackles. Crosby D and Bow shackles have cast in markings at 45 degrees each side of the centre line to give a quick check that direction of load is within 45 degrees.

The reason that bow shackles exist is so that the pin ends are within the maximum OD of the bow, thats it, the only reason.

 

[Andrew G]

Blowing, any reason that the pin ends should be within the max OD (other than to minimise their width) ie there is no structual reason that I can see?? Cheers, Andrew

 

[J Neeves]

There seem to be different designs of Bow shackle. Some have quite long pins, still within the maximum OD of the bow, but some have short pins, well within the max OD. I have been told that lifting bow shackles have short pins as a short pin can take a higher load (for the same diam of pin). Rated shackles, with the WLL cast into the bow, tend to (or all?) have short pins.

The distance between the eyes (or the length of the pin) of lifting shackles varies by a few mm (edit - for a given size of shackle), some might not fit your anchor - its worth checking.

Jonathan

 

[vyv_cox]

This weekend I was shown this simple add-on to an anchor shackle, which seems like an excellent idea that overcomes many of the problems of fitting shackles to narrow bow rollers. Not my idea and I'm not trying to steal his thunder, I believe he will post it himself. The device is simply two cones that fit over the shackle pin. Centralises the load very effectively for any shackle type. Cheap and easy.

 

[NormanS]

This is not true. So called D shackles can be loaded exactly the same as Bow shackles. Crosby D and Bow shackles have cast in markings at 45 degrees each side of the centre line to give a quick check that direction of load is within 45 degrees.

The reason that bow shackles exist is so that the pin ends are within the maximum OD of the bow, thats it, the only reason.

If you have a set-up where you want to have two separate loads onto one shackle, like two slings at 45º, a dee shackle will not have enough space at the bottom of the Dee, to take the two shackles, and you would have to use a bow. My understanding from lifting gear, now somewhat out of date, is that for a given size, a Dee shackle has a greater SWL than a Bow.

 

[vyv_cox]

Although a very few of the ones I tested failed in the wire, the vast majority failed at the pin to eye thread, at the pin or the eye itself. That seems to indicate that the shape of the shackle body has little to do with it.

 

[NormanS]

Although a very few of the ones I tested failed in the wire, the vast majority failed at the pin to eye thread, at the pin or the eye itself. That seems to indicate that the shape of the shackle body has little to do with it.

I expect your tests were made using a single in-line load.

 

[vyv_cox]

I expect your tests were made using a single in-line load.

Correct. I did not consider any divided loads mentioned in your post above. Doesn't seem very relevant to anchors, although as you say can be for lifting and hoisting.

 

[Noahsdad]

Vyv those cones look just the ticket for centralising my runners and checkstays.
Are they commercially available in various sizes or have I just missed spotting them in the chandlers?

 

[vyv_cox]

Vyv those cones look just the ticket for centralising my runners and checkstays.
Are they commercially available in various sizes or have I just missed spotting them in the chandlers?

No, they were designed by a forumite and made for him by one of his technicians. He tells me he has no plans to market them, so feel free to copy. I am expecting him to post about them shortly.

 

[GHA]

Load cell shackles use similar, been trying to remember for ages where I'd seen one before


Probably cost a bomb though, maybe some fat washers made from cheap ebay nylon bar would work?

 

[Andrew G]

Vyv, re your pic at #12:
1) the cones could add substantially to the strength of any shackle (Dee or Bow). I suppose you haven’t tested the effect of a load centred on the pin vs at an end?
2) I assume that is the Allen key headed pin you raised in another post – very neat
3) What is that to the right of the pic?
GHA - nice big pic. . . (just me being me . . .)
Cheers, Andrew